Book 11 Module 7A

CATEGORY B1 B2 AIRCRAFT HANDLING

CONTAMINATION & CLEANING COLD WEATHER PRECAUTIONS

Licence By Post

For best examination results always use latest

issue number.

Licence By Post © Copyright B EASA 66 7A.17 ISSUE 09 1012

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No part of this study book may be re-produced or distributed in any form or by any means, or stored in a data base or retrieval system in whole or in part without prior written permission from Licence By Post. Books in the LBP series are regularly up-dated/re-written to keep pace with the changing technology, changing examination requirements and changing legal requirements.

AUTHORITY

It is IMPORTANT to note that the information in this book is for study/training

purposes only.

When carrying out a procedure/work on aircraft/aircraft equipment you MUST

always refer to the relevant aircraft maintenance manual or equipment

manufacturer’s handbook.

You should also follow the requirements of your national regulatory authority (the

CAA in the UK) and laid down company policy as regards local procedures, recording,

report writing, documentation etc.

For health and safety in the workplace you should follow the regulations/guidelines

as specified by the equipment manufacturer, your company, national safety

authorities and national governments.

ACKNOWLEDGEMENTS

With special thanks to:

AIRBUS INDUSTRIE

BRITISH AEROSPACE

UK CIVIL AVIATION AUTHORITY

for permission to reproduce drawings.

ADDENDUM Addendum action in response to student feed-back after taking the CAA

examinations.

***

Question on Hogging. This subject is not listed in the module 7 syllabus but is listed

in the module 11 syllabuses. It is the tendency of the fuselage to be bent after a

heavy landing. The front and rear of the fuselage are bent down low and the middle is

high. When it bends the other way (low in the middle and high at the ends) it is called

sagging. Tolerances will be allowed (AMM/SRM) in both cases and if within tolerance

the aircraft is returned to service after a thorough inspection for other damage. Where

no tolerances are given or where they have been exceeded then the manufacturer will

have to be consulted and the aircraft withdrawn from service until the problem has

been rectified.

***

Question on external flying control locks fitted to control systems fitted with spring

tabs. If the control lock fits to the control surface and does not cover the tab then the

control column can be moved as it is connected directly to the tab (and the tab will

move). In very general terms the control column is connected directly to the tab and

the tab is connected to the control surface via a spring.

*****

CONTENTS

Page

Ramp maintenance 1

Aircraft movement 5

Marshalling 5

Towing 10

Parking 13

Mooring/picketing 14

Jacking/trestling/shoring 18

Cold weather precautions 25

Ice and snow formation on aircraft 26

Ground de-icing 27

Ice and snow removal 28

Refuelling/defuelling 34

Aircraft cleaning 41

Ground service connections 49

Appendix – CAA essay questions 55

HOW TO TACKLE THIS BOOK

Written to level 2 of the EASA Part 66 syllabus module 7A for the mechanical (B1)

and avionic (B2) aircraft maintenance engineer.

For the category A line maintenance engineer you are referred to the LBP book set

module 7 specifically written to the A standard. The B3 engineer should study the B3

book set.

This book deals with subjects having separate ATA chapters in the AMM:

Chapter 7 - Lifting and shoring.

Chapter 9 - Towing.

Chapter 10 - Parking, mooring and storage.

Chapter 51 - Cleaning.

Have a look at these areas for your aircraft and note any differences/ similarities to

the contents of this book.

Note. Drawings taken from CAPs (Civil Air Publications) may not be found in those

publications due to amendment action.

The author has used large aircraft as examples on the understanding that if the

student knows how to handle the bigger ones then the smaller aircraft will be the

same but without some of the procedures – also the CAA would expect that all B1/B2

engineers know the details to this level anyway.

The subject of Cleaning has been included, this is because the CAA have been known

to ask questions (essay) on this subject for module 7. Cleaning is listed as a subject

in modules 11 though it is not listed as such in module 7. It could, however, be

included as part of the listings, Aircraft Handling & Storage or Abnormal Events.

Note that with all procedures the AMM (Aircraft Maintenance Manual) must always

be consulted.

RAMP MAINTENANCE

The CAA will expect you to be able to ‘see’ an aircraft in after a flight and ‘see’ it out.

It may be a small aircraft with no passengers, it may be large with several hundred

passengers on board. You must be aware of all the maintenance that has to be

carried out. The fundamental checks to be carried out on all aircraft are similar in

terms of refuelling, rectification of any defects, before flight inspections, after flight

inspections, etc.

There are, of course, variations and that is where the aircraft maintenance manual

(AMM) comes in – always refer to it to check for the correct procedures to be carried

out.

The following paragraphs indicate some general points to be considered for a

passenger aircraft. If you can understand how to cope with a large aircraft then the

smaller ones should be easy.

Aircraft Arrival (Figure 2)

1. Check AMM for procedure to be followed (after-flight inspection,

refuelling etc.)

2. Ensure the area is clear of all equipment and debris/snow etc.

3. Ensure that the required maintenance equipment is standing by,

eg, equipment for: baggage handling; refuelling; toilet servicing;

system maintenance – electrical – hydraulic etc.

4. Ensure servicing personnel available.

5. Ensure any spares are available – may have been radioed forward via a

datalink from the aircraft (automatic on some aircraft).

6. When aircraft arrives marshal it in, chock wheels, shut down engines,

put brakes off. Fit landing gear ground locks, flying control locks, and

fit airframe/engine/systems covers if aircraft is to remain on the ground

for a time.

7. Load/unload aircraft (cargo, baggage, passengers).

8. Carry out after-flight inspection. If aircraft taking off soon carry out

between-flight inspection, and replenish consumables. Clean cabin,

galleys and toilets. Rectify any defects.

9. Secure aircraft if it is not leaving straight away.

10. Complete details in the Tech Log and sign.

11. Secure aircraft.

Aircraft Departure (Figure 2)

1. Carry out before-flight inspection (AMM) or between-flight inspection as

necessary. Ensure correct fuel load. Ensure toilets and galleys are

serviced and provisioned and cabin areas cleaned.

2. Make up Weight and Balance Schedule.

3. Check loading (passengers/cargo) and fuel state – make up load sheet

(see later chapters in this book).

4. Remove all covers and ground locks.

5. Ensure aircraft is free of ice and snow. Check weather conditions and

hold-over times.

- 1 -

6. Clear Tech Log and sign. Check deferred defects against the MEL

(minimum equipment list). Ensure pilot is informed of any deferred

defects carried. Pilot to sign Loading Data Sheet.

7. Check all doors, hatches etc are closed and passenger ramps pulled

back out of the way.

8. Connect mic/tel lead to aircraft.

9. Ensure ground crew in place and check with pilot.

10. Ensure equipment available for ‘push back’ (see figure 1).

11. Isolate nose wheel steering.

12. Connect correct towing arm to aircraft and tug.

13. Clear area – start engines, if allowed before push-back (at some airports

engines must be started only after pushback) – remove chocks.

14. After checking with pilot (he/she will get clearance from ATC) push

aircraft back using the tug. Ensure adequate clearance between aircraft

wingtips and tail – use look-outs if necessary.

15. After push-back reinstate nose wheel steering, disconnect towing arm,

hand over aircraft movement control to pilot and remove mic/tel lead.

Fig. 1 TOWING THE A310

The Ramp

The Ramp or Line is the area where cargo, passengers and crew are transferred to

and from the aircraft. It is also the area where a great deal of maintenance is carried

out. Some people call this first-line servicing, others call it ramp maintenance.

Besides rectification of minor defects that have occurred during the previous flight

and before-flight/after flight/turn round inspections are carried out the aircraft has

to have consumables replenished and be cleaned.

With most airlines the following tasks are performed using contractors:

* Refuelling.

* Toilet waste disposal and toilet tank replenishment.

* Drinking water (potable water) tank/s replenishment.

* Oxygen/compressed air systems replenished.

* Cabin, galley, toilet cleaning.

* Galley stock replenishment.

* Aircraft snow removal/de-icing carried out.

- 2 -

Figure 2 shows the various external connections for the ramp maintenance of the

B747 as well as the location of the various maintenance vehicles during turn round

operations.

The B747 is taken as an example as it has most of the systems/equipment used in a

turn-around. Take a moment to study the drawing and note the various maintenance

vehicles and maintenance vehicle connections.

Although contractors may perform most of this work the aircraft is still ‘yours’ and all

work will come under your signature for clearance for flight. So you will need to know

what is going on.

Fig. 2 RAMP SERVICING THE B747 – AN OVERVIEW

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Fig. 3 AIRCRAFT MOVEMENT – GENERAL

With reference to figure 3. If the aircraft is to be moved using the engines then it

must be in accordance with company policy and the person running the engines

must be cleared to taxi the aircraft under power. With the other two methods of

aircraft movement a qualified person must be on the brakes.

Because of the complexities of ramp maintenance there has to be co-ordination

between various people/teams/contractors, to include:

* Engineer in charge of the technical side of the aircraft (you).

* Refuelling team.

* Galley replenishment team.

* Toilet effluent removal team.

* Aircraft cleaners (internal).

* Aircraft cleaners (external). Not often used.

* Baggage handlers/cargo loaders.

* Passenger administration (security, baggage, check-in, movement etc).

* De-icing team.

On small aircraft all of the appropriate items above would be completed by you so

you would know what is going on. On large aircraft this would not be possible so

often a Ramp Manager/Ramp Co-ordinator is used. His/her job is to co-ordinate all

of the above activities and ensure that all are completed in the correct order. You

would check with him/her on the readiness state of the aircraft.

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It would be up to the operator to set up this organisation and to define the

responsibilities of the individual groups/sub-contractors. This would be part of the

company’s exposition – including all safety aspects.

AIRCRAFT MOVEMENT

An aircraft may be moved:

* Under it’s own power using flight crew or ground crew (in some

organisations ground crew can be certified to taxi aircraft).

* Manually – pushing by hand. Quite easy for small aircraft but much

more difficult for the larger ones – though it can be done if needs must

and you have enough manpower. Remember there are some parts of an

aircraft that are not strong enough to be pushed on. These are indicated

in the AMM and have warnings painted on the area such as NO PUSH,

DO NOT PUSH HERE etc.

* Using a tug/tractor and towing gear.

* Using a special hand operated towing trolley that is self-powered and

connected to the nose/tail wheel direct.

MARSHALLING

When the aircraft is moving under its own power and it is in the ramp area it should

be marshalled by qualified personnel. It is difficult for the pilot to judge wing-tip and

tailplane clearances and it is also impossible for him/her to be fully aware of other

aircraft and vehicular traffic in the area.

The person-in-charge is the marshaller who should stand where the pilot can see

him/her – usually in front and to the left (port side) of the aircraft. The marshaller

should be able to see (and be seen) by all other ground crew involved in the

movement of the aircraft. The number of crew depends on the size of the aircraft but

in general there is:

* 1 marshaller.

* 2 wingwalkers – to check wing-tip/helicopter blade clearances from

nearby aircraft/equipment/buildings.

* 1 person at the tail.

All personnel should be aware of the dangers of aircraft moving under their own

power. These include:

* Noise.

* Blast from jet engines.

* Dust and airborne debris from jet engines, propellers, rotorblades.

* Dangers from jet engine intakes.

* Propeller blades.

* Helicopter rotor blades (main and tail).

If the engines are likely to be noisy then ear defenders are to be warn and if the

marshaller is required to walk backwards then he/she should ensure that the ground

behind him/her is free from equipment, safe to walk on and be aware if any

aircraft/vehicles move into the area.

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CAP 637 Visual Aids Handbook published by the CAA show the recommended

signals to use and the ICAO recommended signals are similar. Also CAP 462

Helicopter External Load Operations show hand signals for helicopters. There are

variations depending on where in the world the marshalling is carried out and there

are also some signals, such as ‘thumbs-up’ (affirmative – positive) and ‘thumbs-down’

(cannot confirm –negative) used widely.

Illuminated wands should be used – particularly at night.

Reference figures 4, 5 and 6 Marshalling Hand Signals.

Note 1. Where the word ‘pilot’ is used the word ‘aircrew’ or ‘flightcrew’

can be substituted.

Note 2. When hand signals are given to the pilot it is important that the

marshaller ensures that he/she has made eye contact with the pilot.

Note 3. Hand signals (i) and (j). Raised fingers can be used to indicate the

engine referred to. The engines are numbered from the port (left) side

to the starboard (right) side of the aircraft:

1 finger 2 fingers 3 fingers 4 fingers

ENGINE 1 ENGINE 2 ENGINE 3 ENGINE 4

The ‘raised finger’ signal can be used by the pilot to indicate an

engine.

Note 4. Hand signals (m) and (n). These signals (and others) can be used by

the pilot to indicate the same meaning.

Note 5. Hand signal (q). The thumbs-down sign is used as a

negative/none affirmation signal. Used by ground and air crew.

Note 6. Hand signal ( r). The drawing shows the command to the pilot to

move

the tail to the right (starboard) whilst the aircraft is backing. The

hand signal with the right hand is a ‘move-back’ signal. For the

aircraft to move tail left the same signal is given but with the other

hand.

Some aircraft can taxi backwards (if allowed in the AMM). Some

piston engined aircraft with reverse pitch propellers for example. In

these circumstances it is important that the marshaller wear eye

protection as there may be a lot of dust and debris in the air.

Note 7. Hand signal (w). For unplugging ground power the signal is the same

except the movement of the right hand is reversed. It is pulled down

from the left hand in an ‘un-plugging’ movement..

Note 8. Many of the signals shown in figures 4, 5 and 6 can be used for both

fixed wing and rotary wing aircraft, however those showing the

helicopter symbol are specific to helicopters.

Note 9. Hand signal (aa) shows move-right. Move-left is similar but with the

hand positions reversed .

Note 10. Hand signal (ab) shows the command to move-up. To indicate move-

down the palms of the hands are turned down and a flapping-down

motion is given.

Note 11. Hand signal (ac). This move-back signal is given in CAP 637. In CAP

462 the move-back signal is shown as both arms down by the side of

the body sweeping forward to the horizontal position repeatedly. If

you get a question on this in a CAA exam you should bring this to the

attention of the invigilator.

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Fig. 4 MARSHALLING HAND SIGNALS - 1

- 7 -

Fig. 5 MARSHALLING HAND SIGNALS – 2

- 8 -

Fig. 6 MARSHALLING HAND SIGNALS - 3

- 9 -

TOWING

In general when towing, it should be on firm level ground, and a towing arm may be

used attached to the nose wheel or tail wheel. When towing on soft ground a bridle is

used attached to the main landing gear with a steering arm attached to the tail wheel

or nose wheel.

Fig. 7 TOWING THE B747

Towing Bridle and Steering Arm

On soft or uneven ground, tail wheeled aircraft are towed forward by a towing bridle

or frame attached to the main landing gear. The steel cable of the bridle is threaded

through a towing attachment on the tug containing a pulley in which the cable rides.

The free ends of the cable are attached to towing lugs on the main landing gear. A

steering arm is attached to the tail wheel.

Fig. 8 TOWING BRIDLE

With aircraft fitted with nose wheels, the towing bridle may be used for forward or

backward movement (provided it says so in the AMM), and is fitted to the front or

back of the main landing gear.

- 10 -

To tow the aircraft forward a towing bridle is used fitted with a special towing arm

attached to the nose wheel. The tug end of the towing arm contains a pulley through

which the towing bridle cable passes. This allows the aircraft to be steered by the

towing arm while even tension on the towing bridle cable is maintained to the main

landing gear.

Towing Arm

When towing an aircraft in the hangar or on hard level standing a towing arm only

may be used. It is fitted to the nose or tail wheel and usually incorporates a spring

shock absorber, and is fitted with a shear-pin to prevent excessive loads being placed

through the nose or tail unit. If a sudden load is placed through the towing arm by

the tug the shock absorber should cope with it and if it can’t, the shear-pin will shear

thus preventing the load being put through the landing gear which will damage it. On

some towing arms the shear pin may have positions for more than one aircraft type –

for example: B727, B737, etc. Ensure that the pin is in the correct position.

Towing Frame

A towing frame may be used on light aircraft. It provides positive control of the

aircraft by the tug and a steering arm is not required. May look antiquated but does

provide complete control of the aircraft during acceleration, turning and braking by

the tug/tractor driver.

Fig. 9 TOWING FRAME

QUESTION What are the checks and precautions required when towing an aircraft?

(10 mins).

ANSWER 1. Check the AMM. Check C of G is within limits and any

windspeeds (check ATC) are within limits consistent with tyre

coefficients of friction (wet conditions, ice on ground etc). Check

maximum angles of towing arm to fuselage centre-line (in the

AMM and painted on the nose gear).

2. Always ensure the aircraft is serviceable to tow eg:

(a) Landing gear ground locks fitted.

(b) ‘Three Greens’ on the flight deck landing gear indicator .

(c) The brake system is serviceable and pressurised.

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(d) The aircraft is structurally intact. All stress panels fitted.

Check if windscreen has to be fitted prior to movement

(applies to some small aircraft).

(e) The tyres and shock absorbers are correctly inflated.

3. Ensure that the correct number of personnel are used and

the person on the aircraft brakes is competent to use them (many

operators insist on the person having passed a test first before

he/she is issued with a ‘brakes ticket’).

4. Ensure power steering is off or disconnected.

5. The tug driver should be qualified and take his/her orders

from the person in charge.

6. The person in charge should be able to communicate with

all the others involved in the towing operation.

7. Look-outs should be positioned at the extremities of the

aircraft – wing tips and tailplane.

8. Turn corners with as large a radius as possible and do not

exceed the minimum turning radius as stated in the AMM.

9. Maximum towing speed is walking speed – unless local

regulations permit otherwise.

10. Ensure navigation (anti-collision) lights are on. Power will need to

be on.

11. Get permission from Air Traffic Control (ATC) before towing in the

ATC zone.

12. Tow only on firm level ground.

13. When finishing the tow ensure that the wheels have revolved at

least one revolution (some manuals give an actual distance) in a

straight line to relieve tyre and landing gear side and torsional

stresses.

14. Disconnect towing gear, re-instate nose wheel steering and chock

wheels. Secure aircraft if it is to be left and switch lights and

power off.

Towing should always be carried out using the correct equipment supplied for the

job. If it is absolutely necessary to tow an aircraft and the correct equipment is not

available then ropes may be used attached to the main landing gear. The best ropes

to use are polymer ropes such as Nylon, Dacron or Polypropylene. The aircraft

operator will have a policy for this and the chief engineer would normally be called.

Figure 10 shows the AMM details of the minimum turning radii for various parts of

the B747. Note the Pavement Width, the towing conditions and the steerable body

main landing gear. There is no need to commit the details to memory.

All aircraft manuals will have drawings similar to this showing details of the towing

equipment, speeds, wind conditions, minimum turning radii, straight line finishing

runs etc.

Remember, when towing an aircraft (helicopter or fixed wing) the minimum bend

radius must not be exceeded. If the aircraft is turned around too small a radii the

main landing gear on the inside of the bend is likely to suffer damage particularly if it

is of the bogie (multi-wheeled) type with a large ‘footprint’.

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This is because when going round a bend the aircraft tends to move about the inside

main landing gear; the landing gear will resist this movement and high torsional

stresses will be set up. These forces can be high enough to cause the inside of the

shock absorber to rotate in the outer case and cause the torque links to shear.

Helicopters may have 2 main wheels and a nose or tail wheel or 4 main wheels.

Helicopters with skids have transport wheels fitted for towing purposes.

Fig. 10 TURNING RADII - B747

PARKING

When parking an aircraft the following precautions must be observed:

1. Refer to the AMM.

2. The aircraft should be parked in such a way so as not to obstruct the

movement of other aircraft or equipment.

3. Park nose into wind where possible on firm level ground.

- 13 -

4. Intake and Pitot-static blanks should be fitted, also undercarriage and

control locks and covers where specified in the AMM.

5. Chock wheels fore and aft and put brakes off.

6. Secure aircraft doors and hatches.

MOORING/PICKETING (Figures 11 to 16)

This is not too unlike parking an aircraft except that it is carried out when the

aircraft is likely to be left in the open for a long period of time. Whether the aircraft is

to be parked or moored will be a decision made locally but will be dependent on how

long it is to be left and what the expected weather conditions are likely to be.

It is advisable to moor an aircraft if it is to stand outside for long periods. This

applies particularly to small aircraft which would otherwise be damaged in high

winds. In very general terms the aircraft is tethered to the ground, all covers and

locks are fitted and the aircraft made safe. Tethering points on the aircraft are

classed as:

* Main picketing/mooring/tiedown points – usually the landing gear.

* Secondary picketing/mooring points – might include wing tips, tail

plane, helicopter blades.

After consulting the AMM the following points should be observed:

1. Move aircraft to an area where ground/mooring points are provided (if

available). These may be steel rings set in concrete flush with the

ground and spaced at regular intervals in a circle. The aircraft landing

gear is lashed to these. Some airfields have long lengths of thick cable

fixed to the ground in areas where mooring is permissible. The aircraft

is moved so the main gear can be tied with rope to the cable. If mooring

rings/cables are not provided then heavy items of equipment can be

used or screw pickets can be screwed into the ground (if mooring off the

hard standing).

2. Proceed as for parking.

3. Fit ‘weather’ covers to wheels, cockpits, engine intakes, exhausts, Pitot

static probes, TAT probes etc.

4. Isolate fuel tanks and battery (in some aircraft the main battery is left

connected to provide power to the fire detection and extinguishing

systems). In some cases the fuel tanks are filled so as to prevent the

linings drying out and cracking.

5. Secure the aircraft to the ground using the main and secondary

mooring points. Use ropes or chains.

6. Drain drinking water (potable water), remove perishable goods and

valuable and attractive items, first aid kits etc.

7. Move aircraft regularly to avoid tyre flat-spots and bearing brinnelling.

8. Carry out regular checks of the aircraft in accordance with the manual

(weekly and/or monthly).

9. For helicopters remove or secure blades (folded and secured to the

fuselage or tethered to the ground).

10. For turbo-propeller driven aircraft secure propeller/s to prevent them

‘wind-milling’ in the wind.

11. Record all work done in the log book and sign.

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Figure 11 shows the mooring of a Boeing 747 and figures 12 to 16 show details of

mooring a Shorts 360 turbo-prop aircraft. The B747 is typical of a large commercial

aircraft and the 360 is typical of a small to medium size aircraft. You need not

remember the details in each case but, you would be required to be able to explain

how you would go about mooring an aircraft.

Note the use of the following:

* Warning flags on covers and blanks.

* Blanks or bungs for all major aircraft orifices.

* Mooring harnesses for the propellers.

* Mooring rings in the ground.

Fig. 11 MOORING THE B747

The tie-down may be performed using cables with end fittings to fit the aircraft tie-

down points. When ropes are used the best ones to use are Nylon, Dacron or

Polypropylene (stronger and less prone to rot than natural fibre ropes).

- 15 -

If manila is used it will shrink when wet and slack has to be allowed for this (about

1” for small aircraft, larger amounts for big aircraft). Anti-slip knots should be used

such as the bowline. Make sure that ropes/cables used are strong enough (have the

minimum breaking load as laid down in the AMM).

If the ropes are tight to the secondary mooring points damage may occur to these in

high winds. When the aircraft moves in the wind the stain on the secondary points

may be too much and damage might ensue. Secondary mooring points include wing

tips, tailplane on a nose wheel aircraft, possibly podded engines.

A slight amount of ‘give’ must be provided to secondary points and this may be by the

use of bungee cords (heavy elastic cord) or tying the rope from the ground mooring

point to the aircraft via a heavy weight (sack of sand). As the aircraft moves so the

mooring line has to lift the weight.

Fig. 12 PROPELLER HARNESS ATTACHMENT TO THE FUSELAGE

Fig. 13 PROPELLER TETHERING

blank

- 16 -

Fig. 14 MOORING THE SHORTS 360

Fig. 15 BLANKS & COVERS - SHORTS 360

blank

- 17 -

Fig. 16 TIE-DOWN DETAILS - SHORTS 360

JACKING & TRESTLING/SHORING

Aircraft are supported clear of the ground for manufacture and for maintenance

purposes. The equipment includes jacks, trestles, cradles, slings, gantries and

fixtures.

For maintenance purposes hydraulically operated jacks and trestles are usually

used.

Aircraft should be jacked on firm level ground in the hangar located in such a

position so as not to be in the way of other operations. If the aircraft has to be jacked

outside, the same applies but the AMM must be consulted as to the maximum

windspeed allowed and ATC contacted to find out the forecast weather conditions for

the period the aircraft is likely to remain on jacks.

The equipment to carry out a particular task is listed in the AMM as is the procedure

to be carried out. Some (large aircraft) aircraft are serviced in servicing docks and,

while the aircraft is supported, the area under the landing gear is lowered to leave the

aircraft supported clear of the ground. Most aircraft, however, are jacked up using

hydraulic jacks.

Trestles (Figure 17)

Usually used to support the aircraft after it has been jacked, but in some cases may

be used as a jack. They may be specially made or made up from various lengths of

‘angle iron’ joined together with nuts and bolts. They incorporate one or two jacking

heads which are adjustable by screw threads.

- 18 -

A padded metal or wooden beam is secured to the jacking head/s shaped to fit under

the wing or fuselage. Universal trestles can be supplied, so that using various

lengths of angle iron, trestles of different sizes, height, and breadth can be

constructed. The jacking heads will be common to them all.

Fig. 17 TRESTLES

Precautions

1. Check that the trestle and beam is of the correct type.

2. Check security of nuts and bolts.

3. Check screw jack threads for serviceability and lubricate.

4. Check padding and security of beam.

Lifting Jacks (Figure 18)

These are usually hydraulically operated to raise and lower the aircraft but for long

periods when the aircraft on jacks, support trestles are used in conjunction with the

jacks once the aircraft has been raised to the correct height. Types of jacks include:

* Pillar or bottle jack.

* Bipod.

* Tripod.

* Quadruped.

Hydraulic jacks can range in height from about 3ft (1m) to about 15ft (5m). Some of

the larger jacks may have an operating platform part way up the main body reached

by a fixed step ladder. Some of the larger jacks also have provision to be connected to

a central power supply so they can be power operated.

In general the jack comprises a central hydraulic unit around which are the support

legs. The moving pillar has either a screw thread and locking collar or a collar and

locking pin which enables the jack to be mechanically locked when the aircraft is at

the correct height. This prevents the collapse of the jack due to any fluid leakage. To

release the locking device the jack must be raised slightly to off-load the collar.

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Fig. 18 LIFTING JACKS

Raising the jack is usually by means of a hand pump. The fluid control valve is

closed and the hand pump operated. This pumps fluid from the reservoir to the jack.

Some jacks may be controlled pneumatically from a central control panel. The air

release valve must be opened whenever the jack is raised or lowered to allow air

into/out of the top of the reservoir.

To lower the jack, raise it slightly, release the locking collar and slowly open the oil

control valve to control the speed of fall. The air release valve must be closed when

the jack is stationary and the oil control valve must remain closed when the locking

device is engaged.

An adapter head is fitted into the top of the pillar and this locates into a jack plate or

pad which is fitted, usually by pip-pins, onto the underside of the airframe (check

location in the AMM and painted on the airframe). The adapter and plate form a ball

joint which gives a degree of flexibility when raising and lowering the aircraft. The

bottom of the legs of the jack fit into plates with a ball socket joint to allow for any

slight unevenness of the ground.

It is essential that the plates sit firmly on the ground and that the legs are aligned

with a small recess in the plate socket to prevent binding.

When jacking ensure all legs are adjusted so that they carry equal weight, all pins are

fully in, and that the jack is vertical (some have a spirit level fitted).

- 20 -

Fig. 19 BOTTLE OR PILLAR JACK

Fig. 20 ARC LIFT

Jacks differ in their lifting capacity, size, number and composition of legs:

(a) Bottle or Pillar jack. Used for wheel changes or brake maintenance

where the jack is fitted to the landing leg (via an adapter) to raise the

aircraft sufficiently to get the wheel clear of the ground (figure 19). For a

flat tyre this height would be the depth of the tyre plus a small amount

for tyre clearance.

(b) Bipod. One of the legs of a quadruped jack is removed to leave two load

bearing legs and one adjustable support leg. This is used for arc lifts

where one side of the aircraft is significantly lower than the other (shock

absorber flat or flat tyre for example) (figure 20). The jack is placed so

that the two load carrying legs (lifting legs) are parallel to a line drawn

between the other main gear and the nose gear (or tail wheel).The jack is

angled against the third support leg so as to be at right angles to the

underside of the wing. As the lift progresses so the jack will straighten

through an arc with the support leg being continuously adjusted.

- 21 -

When the jack is vertical the lift stops and the other jacks are positioned

and a conventional jacking operation is carried out. This is a difficult

operation and is not often carried out. Always refer to the AMM

(c) Tripod. Three legs, equally disposed around the central body. Used for

vertical lifts only.

(d) Quadruped. Four legs, equally disposed around the central body. Two

are adjustable to allow for uneven ground. Used for vertical lifts only.

Larger jacks have transportation wheels fitted either permanently or temporary for

movement to and from the aircraft and can be towed – though very slowly. The

correct jack must be used (the maximum load is marked on the side of the jack) and

the correct adaptor and the aircraft should be raised and lowered slowing.

Servicing usually involves:

(a) Cleaning, lubrication and inspection for damage and corrosion.

(b) Checking oil level.

(c) All pins are in position and leg adjusting mechanisms work.

(d) Correct function of air and oil control valves.

(e) Correct operation of the jack and locking devices.

Jacking and Trestling a Nose Wheel Aircraft (Figure 21)

1. Consult the AMM for details of procedure, equipment used, position of

equipment, weight and C of G limits, fuel state, etc.

2. Check aircraft's C of G and fuel state.

3. Check aircraft is structurally sound to jack.

4. Configure the aircraft for jacking. Isolate appropriate electrical circuits

(pull C/B's). If this is not done the aircraft may think that it has taken

off and various services/warnings could operate.

5. Bond aircraft to ground.

6. Jack on firm level ground in the hangar or outside in a position so as

not to obstruct other aircraft movements. If jacking outside check wind

speed and direction with air traffic control and cross refer to the AMM.

7. Position ground equipment (one jack at the nose and one under each

wing – usually).

8. A person who knows what to do should be positioned at each of the

following:

(a) Each jack and trestle.

(b) Look-out for overhead obstructions (fin hitting the hangar

roof).

(c) Levelling station (plum-bob or spirit level on the aircraft to

check aircraft is being raised level).

(d) A person in charge to be in contact with all the others.

9. Chock the wheels (unless the manual states otherwise – the wheels of

levered suspension undercarriages will roll forward as the aircraft

raises, so check) and put brakes off.

10. Raise the aircraft slowly and keep in a level position, follow up with a

tail trestle. This is used to prevent the possibility of tail over balance.

- 22 -

11. At the required height lock all jacks and position steady trestles. These

may be at the tail, mid fuselage, wing tips and mid wing positions.

Consult the AMM and the positions are also painted on the aircraft.

Jacking and Trestling a Tail Wheel Aircraft

Many of the points mentioned for a nose wheeled aircraft apply here but the general

procedure is different and is usually as follows:

1. Chock the main wheels and ensure the brakes are off.

2. Weight the tail either by attaching weights to the tail wheel or placing

weights inside the rear of the aircraft. The author has seen sealed sacks

of sand used and stacked in the rear toilet on one aircraft. These

weights ensure that the aircraft does not tip forward on its nose.

3. Raise the tail of the aircraft manually (small aircraft), or by use of a

crane and special adapter in the main spare of the tailplane (the tail of

small aircraft are raised using a frame under the tail supported by a

cross-beam with two men either side the tail is raised manually).

4. Place a trestle under the tail, lower the aircraft onto it, and tie it down.

5. Place main jacks in position under each wing and jack until the wheels

are clear of the ground.

6. Place trestles as per the AMM.

Lowering the Aircraft

This will vary with each type of aircraft but in general it is the reverse of raising with

the following additional checks:

1. Consult the AMM.

2. Ensure the landing gear is complete, serviceable, and locked down with

‘three greens’ showing and ground locks fitted

3. Check wheels and tyres for serviceability and ensure tyres and shock

absorbers are correctly inflated.

4. Hydraulic system pressurised with landing gear locked down.

5. Wheel brakes are off and all unnecessary equipment and items clear

from under the aircraft.

6. All systems that require the aircraft to be jacked for testing have been

tested and cleared.

7. Stress panels are fitted.

8. Aircraft electrically/electronically configured for lowering (we don’t want

the spoilers deploying automatically for example).

9. Check aircraft loading and C of G.

Remove trestles and clear away from aircraft. Slowly lower the aircraft

to the ground keeping it level. This is done by releasing the lock ring on

each jack by 2 or 3 turns, opening the air release valve and slowly

opening the hydraulic control valve. The rate of descent is controlled by

this valve. When the jack ram lowers sufficiently to near the locking ring

then this is screwed up another 2 or 3 turns. This is a safety measure

so if the hydraulics was to fail the aircraft would only drop to the lock

ring.

- 23 -

10. When the aircraft is firmly resting on the ground and the jacking heads

are clear of the aircraft slide the jacks clear of the aircraft. Remove the

adapters from the aircraft (usually fitted with pip-pins and chock the

wheels.

Note. When removing the jacks from under the aircraft lower them clear of the

aircraft as quickly as possible as the aircraft oleos may stick and the aircraft might

‘jump’ down. Ensure hands are clear of the jacking head in case this happens.

With a tail wheeled aircraft the main jacks are lowered first; the main wheels

chocked; then the tail is lifted off its trestle, the trestle removed and the tail lowered

to the ground and all the weights removed.

Jacking and Trestling a Helicopter

This is similar to jacking and trestling a nose wheel aircraft and with helicopters

fitted with skids the amount of lift during a jacking operation is small as there is no

tyre deflection and little shock absorber deflection (there is some as the skid

structure is designed to flex to absorb shocks).

General

Remember to record and sign for all work carried out on the aircraft in the log book

or work cards – including jacking and trestling.

Note the jacking arrangements for the B757 in figure 21. Note the primary jacking

points and the secondary stabilising jacking point at the tail. Note the C of G range

and the Mean Aerodynamic Cord (MAC) length. For more details of these please refer

to the book in this series entitled Weight and Balance.

Fig. 21 EXAMPLE - JACKING THE B757

- 24 -

COLD WEATHER PRECAUTIONS

In some countries this is never a problem but in others, those in the northern parts

of the northern hemisphere and the far south in the southern hemisphere, frost, ice,

slush and snow can be a problem. In general:

1. Keep all working areas clear of snow and ice.

2. When spreading sand/salt outside in the working areas. Keep sand/salt

away from aircraft, aircraft equipment, jet intakes, Pitot static vents,

etc.

3. Ideally keep aircraft in heated hangers. Not always possible

4. Work in heated hangars/heated areas as much as possible. Personnel

must avoid getting too cold as this produces Cold Stress.

If it is not possible to work in a heated hangar or in close proximity to a

portable space heater then periods must be allowed at regular intervals

for the person to return to a heated area to be warmed through.

After Flight (Check the AMM)

1. Fit all airframe, engine and Pitot/static covers, and landing gear locks.

2. If aircraft is wet apply anti-freeze liquid to the inside of covers before

fitting.

3. Allow any ice in intakes, water drains, etc, to melt, drain water then fit

covers and plugs.

4. Drain oil whilst hot (from piston engines in particular in extreme cold),

and drain water traps in Pitot/static systems.

5. Drain drinking (potable) water systems.

6. Drain and clean all toilet systems.

7. Clean, drain and remove any foodstuffs from galleys.

8. Drain oil and water traps on pneumatic systems.

9. Park or moor aircraft – leave brakes off (prevents them freezing on).

10. Record all work done in the log book.

Before Flight (refer to AMM)

1. Remove covers, blanks and locks.

2. Remove ice and snow from airframe and engines using blower heaters

or fluid spray systems (see later chapters).

3. Pre-heat engines using blower heaters.

4. Fill any drained systems and check for leaks. Piston engines are usually

filled with pre-heated oil (in extreme cold conditions).

5. Check all heaters – windscreen – Pitot – TAT – drain masts – ice

detectors – EPR – heater mats etc.

6. Carry out normal before flight inspection.

7. Ensure all engine intakes are clear of snow/ice deposits. Rotate

fan/turbine with wooden stick to check freedom of movement.

8. Check that all control surfaces, flaps, slats, spoilers, landing gear

mechanisms, airframe, all air vents and probes, intakes, exhausts etc

are clear of frost and snow deposits.

9. If aircraft does not fly within a certain time (depending on ambient

temperature) re-do items 2, 3 and 7 above.

- 25 -

ICE & SNOW FORMATION ON AIRCRAFT

Icing on aircraft is caused by a combination of freezing conditions (low ambient

temperature or low outside air temperature (OAT) and moisture in the atmosphere. It

may also be caused by freezing rain or drizzle. The actual amount depends on

surface temperature, surface condition, duration of icing conditions, and the amount

of moisture present in the atmosphere.

Hoar Frost

Hoar frost occurs on a surface which is at a temperature below the freezing point of

the adjacent air and, of course, below freezing point. It is formed in clear air when

water vapour is converted directly to ice and builds up into a white semi-crystalline

coating. Hoar frost is white, soft and feathery.

When hoar frost occurs on aircraft on the ground, the weight of the deposit is

unlikely to be serious, but the deposit, if not removed from the airframe, will interfere

with the airflow causing drag and possibly preventing it attaining flying speed during

take-off. The windscreen may be obscured, and the free working of moving parts such

as flying control surfaces may be affected.

Remove all frost deposits from the aircraft before dispatch.

Rime Ice

This ice formation, which is less dense than glaze ice but more dense than hoar frost,

is an opaque, rough deposit. At ground level it forms in freezing fog conditions and

consists of a deposit of ice on the windward side of exposed objects. Rime ice is light

and porous and results from the small water drops freezing as individual particles,

with little or no spreading. A large amount of air is trapped between the particles.

Aircraft in flight may experience rime icing when flying through clouds with the air

temperature and the temperature of the airframe below freezing point; the icing

builds up on the leading edge, but does not extend back along the chord. Ice of this

type usually has no great weight, but the danger is that it will interfere with the

airflow over wings, etc, and may choke the orifices of the carburettor, air intakes and

Pitot-static vents.

Glaze Ice

Glaze ice is the glassy deposit that forms over the village pond after a frosty night. On

aircraft, glaze ice forms when the aircraft encounters freezing rain with the air

temperature and the temperature of the airframe below freezing point.

It consists of a transparent or opaque coating of ice with a glassy surface and results

from the liquid water flowing over the airframe before freezing; glaze ice may be

mixed with sleet or snow. Glaze ice is dense, tough and sticks closely to the surface.

It cannot easily be shaken off and, if it breaks off in flight it comes away in lumps

which can cause damage to the airframe.

- 26 -

The main danger of glaze ice is aerodynamic and debris damage, but to this must be

added, that due to the weight of ice, unequal wing loading and propeller blade

vibration may occur. Glaze ice is the most severe and the most dangerous form of ice

formation on aircraft.

Debris Icing

This is caused by slush/snow/moisture being throne/blown onto the aircraft by the

wind, or passing vehicular traffic or blown by propeller/jet efflux from other aircraft.

Pack Snow

Normally, snow falling on an aircraft does not adhere and will settle on the top

surfaces only. If the temperature of the airframe is below freezing point however,

glaze ice may form from the moisture in the snow. The icing of the aircraft in such

conditions, however, is primarily due to water droplets, though snow may

subsequently be embedded in the ice so formed.

Conclusions

If any ice or snow on aircraft is not removed before take-off then the following may

result:

(a) Decreased lift due to aerofoil change in shape. An ice layer 1/16th of an

inch (1.6mm) thick on the leading edge can reduce lift by up to 24%.

(b) Increased drag due to the rough surface of the airframe (skin friction).

(c) Decreased propeller efficiency due to alterations of the blade profile and

increased blade thickness.

(d) Propeller vibration due to uneven distribution of ice.

(e) Loss of control due to ice preventing movement of control surfaces.

(f) Increased risk of control surface flutter due to control surface

C of G change because of the ice.

(g) Increased aircraft all up weight and increased wing loading. The weight

of the ice may prevent the aircraft from taking-off.

(h) Higher stalling speed.

(i) Loss of inherent stability may occur due to displacement of the centre of

gravity caused by the weight of ice.

(j) Loss of vision if the windscreen becomes iced over.

(k) Ice debris damage.

(l) Malfunction of flight/engine instruments. This would occur if

Pitot/static and EPR probes/vents became blocked.

GROUND DE-ICING

The aircraft de-icing systems are designed to remove or prevent the formation of ice

on parts of the wings, tail, engine nacelles and various probes during flight and

would not normally be effective in removing deposits which have accumulated while

the aircraft is stationary. Their use may aggravate the situation by melting some of

the deposit which would then freeze elsewhere.

- 27 -

The use of cabin/airframe heating to remove deposits from the fuselage/wings etc is

not recommended. So ground de-icing by the ground crew must be carried out if

there are any deposits on the aircraft.

When aircraft are kept in a hangar during inclement weather any melted snow or ice

may freeze again if the aircraft is subsequently moved outside into sub-zero

temperatures. Complete protection could be provided by placing aircraft in heated

hangars, but for large aircraft this is not always possible except for servicing.

ICE & SNOW REMOVAL

In general, depending on ambient temperatures, ice deposits can be removed from

the airframe/engines using:

* Cold water (ambient temperatures above freezing).

* Hot air.

* Hot water (ambient temperatures above -3°C). Max water temperature

82°C (180°F) followed by de-icing fluid (rare).

* De-icing fluids(common)/de-icing pastes.

Hot air blowers are powered electrically or by the use of fuel and are very effective for

smaller aircraft. For larger aircraft their use is limited to local area warming for work

purposes.

For most aircraft ice is best removed by the use of de-icing fluid (eg DTD 406 or

similar, or, in severe conditions, Kilfrost ‘Arctic’ or equivalent).

These fluids normally contain ethylene glycol and isopropyl alcohol and may be

applied either by spray or hand. It should be applied as close to the departure time

as possible and repeated if aircraft departure is delayed.

De-icing fluids may adversely affect glazed panels, composite structures or the

exterior finish of aircraft, particularly when the paint is new. Only the type of fluid,

and it’s method of application, as stated in the AMM should be used.

Some fluids, particularly those with an alcohol base, may cause dilution of oils and

greases. Spray nozzles should not therefore, be directed at lubrication points or

bearings and an inspection of areas where fluid may be trapped is necessary. The

AMM may specify re-lubrication in these areas whenever de-icing fluids are used.

Frost and ice may also be removed from aircraft surfaces using a mobile hot air

supply. The air is blown on to the wings, fuselage and tail surfaces and blows

away/melts the ice. Operators using this equipment should ensure that any

meltwater is dried up and not allowed to accumulate in hinges, structure etc, where

re-freezing could occur.

When using hot air blowers, remember that the air can heat some polymers (plastics)

to near melting point, can melt greases out of bearings and may even over-heat some

aluminium alloys (if prolonged close exposure is allowed). Exercise care when

directing the hot air stream so as not to give prolonged exposure to these areas as

well as to any inflammable liquids.

- 28 -

Soft laying snow can be removed from the top surfaces of the aircraft with a long

handled brush or squeegee, care being taken not to damage aerials, vents, stall

warning vanes, vortex generators, etc, which may be concealed by the snow. In at

least one aircraft manual the procedure for snow removal on top of the fuselage is to

use a soft rope thrown over the fuselage and pulled to and fro and backwards over

the fuselage. Again the same precautions should be observed re aerials, stall warning

vanes, vortex generators etc.

Snow should be brushed off the aircraft structure and should not be allowed to go

into cowlings, intakes, vents, shrouds etc. Light snow can be removed by blowing

with cold air. It is important to remove the snow from around the aircraft and keep

the working area clear. Should snow and ice be allowed to accumulate on the ground

it will make working in the area difficult, cause obstruction and may be sucked into

intakes.

Remember, when walking on the surface of the aircraft it is slippery at the best of

times. When there is snow about then the aircraft surface can be treacherous to walk

on. Always use a safety harness or tackle the job from a set of steps or a gantry.

Fluid Sprays

Fluids may be used hot or cold and are of two main types:

Type I AEA fluid (unthickened). Has a high glycol content and a low viscosity.

Good de-icing but has short ‘hold-over times’.

Type II AEA fluid (thickened). Has a minimum glycol content of 50%. Good de-

icing with longer ‘hold-over times’.

The above classifications are fairly old and some (modern) aircraft manuals make

mention of type I, II, III and type IV fluids. For example, type II and IV fluids are used

when:

Temperature down to (°C) Dilution ratio by volume (de-icing

fluid/water)

-3 50/50 (Type I fluid used neat also.)

-14 75/25

-25 100/0

below -25 Insure ambient temperature at least 7° higher

than freezing point of de-icing fluid.

Ice and frozen snow deposits can be removed by fluid spraying. It is important to

ensure that all surfaces are de-iced including all airframe external surfaces

(including wings, tailplane and fin); control surfaces; high lift devices; spoilers;

propellers; rotorblades (on helicopters); windscreens; engine intakes; ram air and

other intakes; landing gear up and down locks; fluid drains; Pitot and static probes;

EPR probes; TAT probes; A of A vanes etc.

- 29 -

In general do not direct the fluid:

(a) Into the wheel brakes.

(b) Into control surface shrouds and structure openings.

(c) Into Pitot/static vents, TAT probes, EPR probes, drains etc.

(d) Onto windscreens and transparent panels - in some cases

delamination may occur (if fluid incompatible, use approved windscreen

de-icing fluid).

(e) Into air intakes and exhausts - engines and air-conditioning systems.

(f) Into fuselage vents/drain holes.

(g) Into bearings and greased mechanisms.

(h) Close to the structure or other equipment, particularly if the fluid

spray is high pressure - it could cause damage and erosion.

In general always:

(a) Consult the AMM.

(b) Remove heavy deposits of snow symmetrically about the aircraft

longitudinal and lateral axes so as to prevent possible overbalance.

(c) Blank off Pitot/static vents, intakes and exhausts and vents and

drains where possible.

(d) Ensure the aircraft is completely snow and ice-free. Some manuals allow

a small amount (depth specified) of ice on the underside of the wing and

some hoar frost on the top of the fuselage. Check the AMM.

(e) Carry out a visual inspection after removal to check for (d) above, check

structure for impingement damage and ensure that fluid has not entered

into areas where it should not be, eg:

* Probes – pressure and temperature sensing.

* Structure drains.

* Brakes.

* Structure.

* Drain masts.

* Normal and emergency exits.

* Cargo doors.

* Windows and windscreens (through vent holes etc).

* Inspection panels.

* Control surface shrouds.

* Control surfaces.

* Air conditioning intakes/exhausts.

* Engine intakes/exhausts.

(f) Record and sign for the work done in the aircraft log book. Record the

fluid used, the dilution ratio, the date and time of application, the fluid

temperature and the ambient temperature.

(g) Monitor the aircraft and the ambient temperature and if the

temperature drops then consider re-de-icing the aircraft, or if the

aircraft does not take off within the Hold Over time allowed then re-de-

ice.

- 30 -

Table from CAP 512 (now withdrawn)

TABLE 1 GUIDE TO HOLD-OVER TIMES

After de-icing the fluid will have a period during which time it will remain effective -

depending on ambient conditions. It is important to read the fluid manufacturer’s

instructions regarding this ‘hold-over time’ and to re-treat the aircraft if the aircraft

does not take-off within the time period.

If in doubt about the ‘hold-over time’ re-treat the aircraft prior to departure anyway.

In general, fluid sprays may be applied cold or hot (hot is the best) and may be low

pressure or high pressure (about 100psi).

Do not exceed the pressure and temperature stated in the aircraft manual, and do

not put the fluid nozzle too near the structure to reduce the possibility of

impingement damage.

Table 1 gives some idea of hold-over times, but it is important to remember that it is

only a guide. You should at all times consult the de-icing fluid manufacturer’s

literature/AMM.

Jet Engines

Jet engine icing can occur if the ambient temperature is less than 10°C (50°F) and

there is visible moisture present such as fog, rain, sleet or snow.

- 31 -

For ambient temperatures down to -30°C (-22°F) the engines can normally be started

without any additional precautions – other than making sure intakes, exhausts,

inlets, outlets and probes are clear of snow and ice. The fuel control is set to RICH

and the oil pressure is likely to read high and the quantity indication likely to read

lower than normal for the first few minutes of running. After this period the values

should normalise.

It the aircraft is taking off the engines should idle for a minimum period of 5 minutes

to allow the engine to warm through. If the engines are just being started to warm

through then they must run for a minimum period of 10 minutes.

If the ambient temperature is lower than -40°C (-40°F) then the engine core must be

pre-warmed for a period of time using hot air blowers (max air temperature 121°C

(250°F). Damage will occur to the bearings otherwise as the oil viscosity will be too

high to allow it to flow. The process will take some time for the core to properly heat

through.

Piston Engines

In very general terms similar conditions apply as to jet engines. It is common at very

low temperatures to drain the oil immediately after engine shut-down. The engine is

pre-warmed before start-up. The oil is pre-warmed before being put back into the

engine and the engine started immediately.

Fluid spray equipment may be:

(a) A bucket and hand operated pump – for small aircraft.

(b) A trolley with a tank and an air pressure supply.

(c) A motorised vehicle with heated pressurised tank and a hydraulically

operated boom spray nozzle. These are operated by specially trained

personnel (normally a driver and boom operator) but it is your aircraft

and you must sign for the work done.

(d) A fixed gantry spray system (car wash system) that the aircraft is towed

through (or taxis through – check engine operation under these

conditions) for those airfields that suffer prolonged icing conditions

during winter.

Hot Fluid Spray

Heated to about 82°C (tank temperature), the heat also has a part to play in removing

the ice so is better than cold fluid spray. Because the fluid is not diluted by the ice

quite so much as the cold fluid spray, it also is better than the cold fluid spray in

preventing further ice formation.

If a ‘car wash’ system is used it is important to note that the fluids used must be

non-toxic and diluted enough to ensure that they are not a fire hazard (hot exhausts

etc). When taxiing through, all cabin conditioning air vents/engine tapings should be

off – to minimise de-icing fluid fumes in the aircraft.

- 32 -

Anti-icing

(Anti-icing is the prevention of ice build-up and De-icing is the removal of ice

deposits).

The above systems will prevent ice formation building up for a time. This depends on

ambient conditions of course. The hot fluid spray being better at this than the cold

fluid spray. However, there is a special dual purpose spray that is much better at

anti-icing than either the cold or hot fluid systems.

This anti-icing barrier compound is mixed with water (check manufacturer’s

instructions) and sprayed at a temperature of about 80°C when used as a de-icing

fluid. When used for anti-icing the fluid is sprayed onto the aircraft cold and

undiluted either before the onset of icing conditions or immediately after the aircraft

has been de-iced. A film of anti-icing compound is left on the sprayed surfaces which

prevents the formation of further ice deposits (depending on ambient conditions).

When used as a de-icing fluid it may give protection from freezing for up to 2 hours.

When used as an anti-icing fluid it will give protection for longer periods - but check

the ambient conditions.

On some aircraft not equipped with an aerofoil de-icing system the use of a de-icing

paste may be specified. This paste will prevent the accumulation of ice deposits.

When spread smoothly by hand over the leading edges of the wings and tail unit the

paste presents a chemically active surface on which ice may form but cannot bond.

Any ice which does form will be blown off in the airflow.

The paste should be reactivated before each flight in accordance with the

manufacturer’s instructions and replaced after approximately four flying hours.

De-icing pastes do not constitute an approved method of de-icing when approval for

intentional flight into icing conditions is required.

Table 2 shows an extract from an AMM. It is interesting to note that cold water is

recommended for ice/snow removal if the ambient temperature is above 1deg C. The

engineer should check that ground temperatures are also above 1deg C and that

forecast temperatures are set to rise.

blank

- 33 - SNOW FROST ICE

A Ambient temperature

34deg F (1deg C) or above

B Ambient temperature

27deg F (-3deg C) to 34deg F (1deg C)

C Ambient temperature

below 27deg F (-3deg C)

1

COLD WATER

USE

NOT ALLOWED

NOT ALLOWED

2 HOT

WATER (200deg F 93deg C)

followed by de-icing fluid.

USE

Optional to apply de-icing fluid.

USE

NOT ALLOWED

3 DE-ICING FLUID

(200deg F)

NOT RECOMMENDED ON COST GROUNDS

USE

USE

4 ANTI-ICING

FLUID

NOT RECOMMENDED ON COST GROUNDS

Apply after method 2 to keep ice, frost & snow to a minimum. Apply after method 3 if necessary.

Apply as protection if

ice, snow or frost expected.

Table 2 EXAMPLE TAKEN FROM AN AMM

REFUELLING/DEFUELLING

Refuelling is the filling or partial filling of some or all of the aircraft tanks and

defuelling is the removal for the fuel from those tanks (normally for maintenance

purposes).

Refuelling is normally carried out at the end of each long flight. The amount of fuel

uplifted depends on the operational requirements. With some aircraft all tanks are

filled completely whilst on others the uplift requirement and tanks to be filled will

depend on the duration of the next flight.

Refuelling systems can be categorised into two groups:

* Open orifice refuelling (over-wing, open vent or gravity refuelling).

* Pressure refuelling, under-wing refuelling or closed line refuelling.

Open Orifice Refuelling

This method of fuelling an aircraft is similar to the way most road vehicles are fuelled

on the garage forecourt. It is common on small aircraft and some larger aircraft have

the facility as well as a pressure refuelling system.

- 34 -

On the top surface of the wing (or fuselage in some cases) there is a filler cap and

tank opening. After operating the quick release fastener and opening the refuelling

panel the refuelling cap is unscrewed from the tank. In figure 22 the refuelling cap is

fitted flush with the wing surface and lifting the tab on the cap allows the cap to be

removed (by twisting the tab or operating a lever).

The filler port may be connected to pipework delivering the fuel to all tanks or, more

often, directly into the individual tank. The cap is usually connected with a lanyard

to the structure to prevent loss and there is usually a bonding point.

To refuel, the fuel nozzle from the bowser is bonded with its bonding lead to the tank

and the nozzle placed inside the tank orifice. The nozzle lever is operated to allow fuel

to flow into the tank. Care needs to be exercised as the tank starts to get full, as it is

a high delivery rate and the fuel will spray back out of the tank when the tank

becomes full. Towards the end of the filling operation flow rates should be reduced

and preparation made to shut-off the control handle on the refuelling hose quickly.

In addition care is needed when opening the refuelling cap to prevent contamination

of the fuel – by rain (if raining) or by debris such as sand etc, if a gale is blowing.

Other potential pitfalls include the danger of walking on the top surfaces of wings

and the possibility of damage to the wing from filler caps, fuelling hoses, people’s

shoes etc. Also there is a risk of fuel imbalance between the tanks (port and

starboard wing tanks for example).

After refuelling the bonding lead should be disconnected and the cap closed.

The biggest disadvantage is that of time to refuel. Access to the top of the tanks can

be difficult and may require step ladders, high rise platforms etc and the actual filling

process can be slow.

Most small aircraft only have the one method of refuelling – gravity refuelling, but

most larger aircraft have both systems fitted. The B747, for example, has the option

of over-wing fuelling, but using this method would require up to 8 hours to fill the

aircraft.

Over-wing refuel points on large aircraft are rarely used but if the aircraft has landed

at an out-station which does not have pressure refuelling equipment then they can

become very useful. Some aircraft are not fitted with them at all, eg the B777.

Pressure Refuelling

This is a system of refuelling where fuel under pressure [max about 50psi (345kPa)]

is supplied from a bowser, tanker, or refuelling pumping vehicle. (It is common at

large airports to have the fuel pumped underground. A pumping vehicle connects into

the ground connection (after lifting a steel cover plate) and pumps the fuel into the

aircraft tanks. The bowser’s (fuel tanker)/pumping vehicle’s fuel hose is connected to

the refuelling point of the aircraft via self sealing connections, both on the aircraft

and on the hose (figure 23). From this single point there is a pipework system within

the aircraft connected to all the tanks in the aircraft. The fuel is controlled into each

tank (by a computer on modern aircraft) by energising solenoids within the refuel

valves, float valves etc.

- 35 -

Fig. 22 OVER WING FUELLING POINT

As each tanks becomes full so its refuel valve shuts off and when all tanks are full

refuelling ceases.

Advantages of pressure refuelling include:

* Higher pressures and flow rates and shorter fuelling times.

* Less risk of spillage.

* Ability to fill individual tanks with any desired quantity of fuel using the

aircraft’s on-board refuelling control system. Electrically or computer

controlled.

* Reduced risk of fuel contamination.

* Better access. Fuelling points are on the underside of the wings and

accessed from the ground.

* Reduced fire risk.

Refuelling Operation

Check the AMM.

The electrical power supply must be ON to operate the various valves, indicators,

refuelling panel and computers etc. This can be provided from the aircraft 400Hz

supply or even from the aircraft battery. Usually power to the refuelling systems is

removed when the aircraft becomes airborne, preventing inadvertent fuel transfer in

flight. The refuelling panel is usually located at the refuelling point and usually

within easy reach of the ground (figure 24).

With power available, and the refuel panel door open, the indications on the refuel

panel will show (the system may go through a BITE check first).

- 36 -

Fig. 23 PRESSURE REFUELLING CONNECTION

The dust cap is removed from the refuelling point and from the hose connector. The

aircraft bonding clip is connected to the refuelling hose and the hose connected to the

aircraft fuelling point via the quick release bayonet type connector.

The action of connecting the hose to the aircraft opens both the valves on the aircraft

refuelling point and the fuelling hose.

When the bowser starts pumping, the pressure will open the non-return valve and

fuel will flow into the system that supplies all the tanks (sometimes called a fuelling

gallery).

As the fuel flows into each tank so a fuel quantity measuring system will measure the

amount of fuel in the tank. The fuel will be shut off to the tank by an electrically

operated shut-off valve when:

(a) The tank becomes full, or

(b) When the fuel reaches the level (quantity) as selected by the engineer at

the refuelling panel.

The fuel flow will continue into the aircraft system until all tanks are full or have

reached their selected quantity level. The bowser/pumping vehicle operator will then

switch the pumping operation OFF.

The system may have provision to allow all tanks to be filled at the correct rate.

However, care still needs to be exercised to ensure an imbalance doesn’t develop (for

example, more fuel on one side of the aircraft than the other would up-set the

aircraft’s C of G laterally).

- 37 -

Fig. 24 REFUELLING CONTROL PANEL

Sometimes additional refuel points are provided to increase the speed of the fuelling

operation – so more than one bowser/pumping unit can be used simultaneously.

Refuel valves can be mechanically operated but they are normally solenoid operated,

using the fuel pressure to actually operate them open. This type of refuelling requires

overfill protection to prevent tank rupture or fuel spillage.

Also, with some aircraft care has to be taken when refuelling /defuelling so as not to

put the longitudinal C of G outside the range between the main gear and the nose

gear.

The aircraft’s C of G, for a nose wheeled aircraft, is just forward of the main gear and

with some aircraft with highly swept wings it might be possible to fuel some tanks in

the wings such that the C of G is moved aft passed the main gear – this would cause

the aircraft to tip back onto its tail.

For tailed wheeled aircraft the C of G is behind the main gear and the tanks are so

situated so that it is not normally possible to overbalance the aircraft forwards.

Defuelling

For overwing refuelling type aircraft this is usually carried out using drains situated

at the bottom of the tanks. For some aircraft the system can be drained from the

engine supply connection (check the AMM).

- 38 -

The fuel is drained into cans (suitably bonded) and returned to the fuel supplier

suitably marked as contaminated to be filtered and re-used.

For pressure defuelling aircraft a bowser in connected (with defuel selected), the non-

return valves are de-seated and the defuel handle is turned. On newer aircraft this

may be a switch selection on the refuel panel. This connects the engine feed manifold

to the refuel points. The engine fuel feed boost pumps are used to provide fuel to the

engine feed manifold and through the defuel valve to the bowser.

Once the bowser has positive flow the pumps on the bowser can be selected to suck.

Again, consideration has to be given as to where fuel is being taken from on the

aircraft to prevent imbalances developing.

Precautions

Fuel is highly combustible and fuel flow will cause a build up of static electricity –

which could cause a spark if the correct bonding has not been carried out.

The following precautions should be observed (also check the book in this series

EASA Module 7 entitled Safety):

* Ensure the correct grade of fuel is used. Check the AMM, also indicated

at the refuelling point and marked on the bowser/ground refuelling

point. (For the mechanical engineer see also the books in this series

EASA module 15 for jet fuels and 16 for gasoline and Diesel fuels).

Check the bowser driver’s log book to ensure that the required dip

checks/water drain checks (quality control checks) have been carried

out on that particular batch of fuel. This will also indicate the specific

gravity of the fuel.

* Bonding. The aircraft needs to be bonded to earth, ideally through a

purpose built bonding line but CAAIPs state alternatives for ‘field’

operations. The bowser must also be bonded to earth and this is often

done through the tyres or a bonding chain/lead hanging underneath.

The bowser and aircraft are bonded together by a bonding lead being

reeled out from the bowser to the aircraft and connected to the aircraft

earth point, which is often (but not always) near the refuel point. The

refuelling hose is bonded to the aircraft.

* The aircraft (and bowser) must be in a designated refuel zone that

should contain any spillage (minimum 20ft or 6m radius).

* No smoking, naked lights or unauthorised equipment allowed. NO

SMOKING signs displayed 50ft (15m) distance from the outermost tank

vent.

* Aircraft power should not be connected or disconnected during the

refuel process. APU’s, if running, should be left running for the duration

and should not be started or stopped during this time.

* Ensure fire cover is available - provided by the airport fire service or

through individual hand held CO2 or Dry Power extinguishers.

Refuelling should not be performed in a hanger unless additional fire

cover is available.

* No radio or radar transmissions allowed during the operation.

* No refuelling during an electrical storm.

- 39 -

* Check that there is clearance under the aircraft from any ground

equipment as the aircraft will settle.

* Aircraft engines should not be running. Some exceptions are allowed to

this rule such as some helicopter operations.

* All vehicles should be parked such that they have a clear exit path – in

case of fire.

* Keep all connections, maintenance areas and equipment clean to

prevent the possibility of fuel contamination. Avoid spillage.

* Any engine driven ground equipment that is required should be cleared

to run in fuelling areas (spark proof exhausts etc) and parked as far

away as possible from the actual refuelling operation.

* If any portable electrical equipment is to be used (torches etc) then

these must be of the approved safety type).

* No flash photography within 20ft of filling points or vents. Do not use

mobile phones of any other personal electronic equipment.

* All combustion heaters must be OFF. Some older aircraft have these.

* Complete the bowser operator’s record of fuel taken or received by the

bowser (gauges at the refuelling control station on the bowser). Compare

these values to those of the aircraft system gauges. Dip tanks if

necessary (a very accurate method of ascertaining the quantity of fuel in

each tank).

* Record fuel up-lift or fuel removed in the aircraft log book and sign.

Draining

This may be required if access is required to the fuel tanks or for certain

maintenance operations such as tank removal.

While defuelling will remove nearly all of the fuel it is often necessary to remove the

residual fuel in each tank using the drain valve/port.

Drain ports are also used for taking fuel samples.

Figure 25 shows a typical drain valve. They are located at the bottom of the fuel tank.

For fuel sampling the primary poppet is pushed up, this de-seats the valve and

allows the fuel from the bottom of the tank to drain into a container.

Fig. 25 TYPICAL DRAIN VALVE

- 40 -

Fuel Spillage

Clear-up all fuel on the aircraft and on the ground. If a major spillage occurs

evacuate all personnel, try and stop the fuel flow, and call the fire services. Do not

start aircraft engines or vehicles until all fuel has been cleared from the area.

Do not allow fuel into drains, waterways etc. If this does occur inform the local water

authority and follow their advice.

Fuel can be mopped up using fuel absorbent agents or emulsion compounds.

These should be disposed of in accordance with the local authority regulations.

All tools and equipment used are to be flame proof and/or spark proof.

AIRCRAFT CLEANING

By aircraft cleaning we do not mean the domestic cleaning of the cabin after the

passengers have left the aircraft but the cleaning of the structure/components either

as a routine procedure or after a spillage of some kind.

For some operators the job of aircraft cleaning is contracted out so the engineer

normally does not get involved – except for checks and inspections afterwards. For

other operators the aircraft engineers have to do it all. In either case, you as the

engineer are expected to know how to go about things. As far as the syllabus is

concerned it is not clear whether this applies only to the B1 person so if you are a B2

person it would be advisable to, at least, read through the subject – particularly

battery electrolyte spillage . The responsible engineer would be required to know:

* The materials to use.

* The precautions to be taken.

* The processes to be carried out.

* The checks and inspections to be carried out afterwards.

External cleaning is carried out:

* As a routine measure to keep the aircraft ‘looking good’ and to help

reduce aerodynamic drag. The airframe will get naturally very dirty over

a period of time and dirt increases skin friction and drag.

* To help prevent deterioration/corrosion as a result from dirt build-up.

* As a routine measure when carrying out certain operations where

fluids/chemicals might contaminate the airframe. Such as alighting on

sea-water (float plane, sea plane etc), crop spraying/ dusting, or flying

in a corrosive atmosphere (low level over the sea, for example).

* As part of a rectification procedure when something goes wrong and

fluids are spilt. For example, chemical fluid spillage, hydraulic fluid

spillage, battery electrolyte spillage, mercury spillage, leaks from toilets

etc.

The aircraft as a whole and its component parts should be kept clean. This helps to

reduce wear, allows for leaks to be more readily detected, reduces crevice corrosion

and makes the aircraft more aerodynamic (for surface cleanliness anyway). It also

helps to promote a good image to customers – and makes the aircraft more pleasant

to work on.

- 41 -

For general exterior cleaning a non-acid soapy solution diluted in water can be used

and the area rinsed off with clean water and dried. Turco Air Tech (or similar) is

suitable.

Materials

Various cleaners are available including Teepol, Turco Air Tec, Ardrox 6025 and PD

680. They all meet various MIL specifications and should be used in accordance with

the cleaning manufacturer’s instructions and the AMM.

These are all listed in Chapter 20 of the AMM.

Table 3 shows part of a listing from an aircraft manual. There is no need to commit

the details of any of these materials to memory but reading through the table does

give you some idea as to the range available.

In this book we will deal with the following episodes but always check the AMM

Chapter 51 for specific cleaning instructions. Cleaning after:

* Chemical crop spraying/dusting.

* Salt water contamination.

* Toilet water leakage.

* Hydraulic fluid contamination.

* Battery acid spillage.

* Mercury contamination.

The procedure to be followed will depend on the actual contaminant and the extent,

but in general terms:

1. Refer to the AMM Chapters 20 and 51.

2. If components are affected, remove for cleaning.

3. If control cables or carpets are affected they are replaced.

4. Inspect area after cleaning.

5. Refit components removed and any systems disturbed are tested.

6. Details of the work carried out are recorded in the log book and the

work signed for.

AFTER USE AS A CHEMICAL CROP SPRAYER

Refer to the aircraft manual for cleaning/inhibiting the powder-hopper/spray-tank

and the distribution system (if needed), also for the cleaning of the external

airframe/engines. Refer to the liquid chemical/powder supplier manual (or check on

the instructions on the containers) for any special cleaning instructions/safety

precautions.

If the aircraft is to be washed, check with the local authority responsible for the

drainage system that wash-water is acceptable going into the drains. If it is not

acceptable wash-water must be collected in tanks and removed by a specialist

chemical disposal firm.

- 42 -

DESIGNATION SPEC USES

Aircraft exterior Turco Air Tec USA (MIL-C-087936)

General purpose aircraft exterior cleaner.

Liquid detergent concentrate Ardrox 6025 USA (MIL-C-87936)

Cleaner and stain remover.

Varsol/white spirit UK USA

Cleaning solvent for mechanical parts.

Trichloroethane (Methyl chloroform)

Genklene USA

Cleaning solvent.

Trichlorotrifluoroethane FreonTF Cleaning oxygen system pipe lines.

Isopropyl alcohol Air3660 France USA

General cleaning.

Rain repellent cleaner Altupol Cleaning rain repellent off windscreens.

Safety solvent USA Odour free solvent cleaning agent.

Stain remover Teepol (MIL-D-16791)

Dry cleaner PD 680 (BS 245:76 type 1)

Solvent for cleaning mechanical parts.

Plastic polishing compound (fine grade)

PP-560 USA

Paste for polishing Plexiglas.

VDU cleaner Alglas V Anti static flight-deck CRT screen cleaner.

TABLE 3 – CLEANING AGENTS

Various cleaning agents are listed in the AMM for both general cleaning and

specialist cleaning. All are supplied with user instructions and health warnings

where necessary.

Always keep all fluids/powders off the skin. Ensure they are kept out of the eyes and

are not breathed in. Wear protective clothing, eye protection and breathing apparatus

where specified in the chemical manufacturer’s manual.

For general exterior cleaning a non-acid soapy solution diluted in water can be used

and the area rinsed off with clean water and dried. Turco Air Tech (or similar) is

suitable.

- 43 -

Clean all air filters (carburettors intakes and air conditioning intakes etc.). Ensure all

water traps are drained and cleaned (Pitot static systems, pneumatic systems etc.).

After airframe cleaning move aircraft to a dry area and check all aircraft drains to see

that they are clear and make sure water/cleaning liquid has not entered parts of the

airframe such as:

* Engine intakes and exhausts.

* Pitot static vents etc.

* Windows, doors and hatches.

* Air conditioning vents.

* Cooling grills.

* Drain holes.

Glass windscreens can be washed with a non-acid soapy solution and cleaned with a

chamois leather and plastic windows can be washed with the same solution and

cleaned with a fine grade plastic polishing compound (listed in the AMM).

Inspect all surfaces and external components for corrosion/erosion and rectify any

damage found as per the aircraft manual (SRM).

Ensure all control surfaces have full and free range of movement.

Record details of the work carried out in the aircraft log book and sign CRS.

After airframe cleaning check all drains to see that they are clear and make sure

water/cleaning liquid has not entered parts of the airframe such as:

* Engine intakes and exhausts.

* Pitot static vents etc.

* Windows, doors and hatches.

* Air conditioning vents.

* Cooling grills.

* Drain holes.

SALT WATER CONTAMINATION

Flush area affected with clean water. Wash area with cleaning agent as specified in

Chapter 51 diluted with water. Rinse again and dry with warm air. Inspect the area

for corrosion/damage and repair as laid down in the manual.

TOILET WATER CONTAMINATION

Does not happen often and when it does it is usually because of an incorrectly seated

valve or a pipe/union leak, or toilet overflowing – on older toilet systems.

Wear protective clothing including goggles.

Find source of leak and rectify.

- 44 -

Remove as much liquid as possible using a cloth or a liquid certified vacuum cleaner.

Remove and discard carpets etc. Thoroughly wash area using a mixture of 100g of

Bicarb of Soda to 1 litre of water. Rinse area and dry. Inspect area to see that all

contaminants have been removed, is corrosion free and all anti-corrosive treatments

are in place. Fit replacement soft furnishings.

HYDRAULIC FLUID CONTAMINATION

Wear protective clothing. Rectify source of leak.

Mop up as much of the fluid as possible. Apply cleaning agent as recommended in

Chapter 51 (in some cases after application it must be left to 30 minutes). Flush with

clean water and dry with air dryer. Inspect area to see that all fluid has been

removed and check that electrical insulation, rubber and plastic items etc have not

been contaminated. If they have, change.

If hot hydraulic fluid (above 132°C) has leaked onto titanium then embrittlement will

result.

The fluid may leave a light brown/dull black residue. Remove this using acetone and

a wooden/plastic scraper. If the protective paint has been damaged or the metal has

been contaminated then the part must be replaced.

BATTERY ELECTROLYTE SPILLAGE

In the event of electrolyte spillage in the aircraft, the following action must be taken

immediately.

Rubber gloves and protective clothing must be worn and use eye protection.

1. Check (and rectify) the cause of the spillage. Check the battery – if suspect,

change. Remove the battery for access.

2. Remove all pools of electrolyte by mopping with a clean rag moistened with

water, care being taken to prevent spreading of the electrolyte. The rag

should be frequently rinsed out in water to remove electrolyte during this

process.

3. Provided the electrolyte has not become trapped in any structure, rinse the

area with clean, cold water, taking particular care not to contaminate

adjacent or below floor electrical equipment. Should carpet become

contaminated, this should be replaced and adjacent structure checked for

evidence of contamination/corrosion.

4. Dry the affected area thoroughly, using a clean rag.

5. Replace any contaminated control cables.

6. If it is suspected that electrolyte has contaminated the structure, perhaps

by capillary action, the following action should be taken.

- 45 -

(a) For lead/acid electrolyte (dilute sulphuric acid) apply sodium

bicarbonate powder to the affected area and wash down with a

saturated solution of sodium bicarbonate.

(b) For Ni-Cad electrolyte (potassium hydroxide solution) rinse the

affected area with 5% solution of acetic acid. If not available,

ordinary household white vinegar may be used neat.

In either case, finally rinse area with clean cold water, taking the same

precautions as in Item 2. Dry the area thoroughly.

If there is any doubt that this procedure has not been effective,

consideration should be given to removal of units and de-riveting the

structure for separate cleaning and inspection.

As sodium bicarbonate (alkali) is in itself mildly corrosive to light alloys,

testing the effectiveness of the cleansing operation may be carried out

using a piece of pH Universal Test Paper. Colour changes indicate the level

of acidity (red) or alkalinity (blue).

Alternatively, litmus paper may be used, satisfactory cleansing being

indicated by no colour change of either blue to red (acid) or red to blue

(alkaline).

NOTE. Acetic acid (5% solution) is not too detrimental to aircraft

structure/light alloys.

7. If any corrosion has occurred to the structure, carry out corrosion removal

procedures (refer to the AMM and to EASA module 7 book entitled

Corrosion in this series) and re-protect structure.

8. Fit and connect the battery (if removed) and test the system as per the

AMM.

9. Record (and sign) all the work done in the appropriate work

cards/Logbook. In all cases of electrolyte spillage, an ADD should be

raised detailing the area affected, the level of cleansing effected

(units/cables removed, etc) and calling for the area to be re-inspected after

24 hours and 14 days for signs of corrosive attack.

Should corrosion then be evident, appropriate action must be taken and

consideration given to repeat inspection at a later date.

CAUTION: In the event of the skin becoming contaminated with electrolyte, wash the

affected area immediately with plenty of clean cold water.

Should eyes become contaminated, flush immediately with plenty of clean cold water

or a propriety brand of eye cleaner such as Steriflex.

In either event seek immediate medical treatment.

- 46 -

MERCURY SPILLAGE

Refer to Chapter 5 of the AMM.

Mercury is found in manometers and in some instruments. It may also be carried as

cargo on transport aircraft. If spilt on metals it can cause rapid corrosion and

embrittlement. The mercury will ‘run’ on the surface like small ball bearings and

quickly run into crevices, and joints.

The rate of corrosion can be so quick as to be apparent in just a few minutes and is

more serious than battery acid corrosion. It is, therefore, important that it is detect,

removed, and treated quickly. You should, of course, follow the procedures laid down

in the AMM/SRM for the aircraft but the following information is generally applicable.

Safety Precautions

1. Wear protective clothing, particularly gloves.

2. Do not swallow mercury or inhale the fumes, report to the medical

centre immediately if this happens.

3. Work in a well ventilated area.

4. Discard all contaminated clothing and materials. Dispose of in

accordance with the local authority regulations.

5. Wash hands, tools, and other equipment contaminated with mercury.

6. Do not smoke, eat or drink, while working with mercury.

Detection Methods

1. Visually. When spilt, mercury will form into ball-bearing like globules.

These will ‘roll’ along surfaces, into crevices, and into joints.

2. X-rays. If unsure of the exact location of mercury it can be seen clearly

on X-rays.

3. ‘Sniffer Gun’. A sniffer gun will pick up mercury vapours and give an

aural and visual warning.

Recognition of Corrosion Products

Mercury corrosion is impossible to rectify in-situ. The only suitable rectification of

corroded areas is by repair (patch or insertion) or by replacement.

Aluminium and Aluminium Alloys. Shows as a greyish powder or whiskery growth.

This growth often occurring within minutes of initial contamination.

Silver, Cadmium and Zinc. Shows as a slightly brighter area where the corrosion has

occurred. The area might be difficult to see.

- 47 -

Fig. 26 LOCALLY MADE-UP MERCURY TRAP

Tackling Mercury Spillage

1. Take action immediately. Corrosion rates can be very quick so the

sooner action is taken the better.

2. Do not move aircraft as the movement can cause the globules to ‘run’

into other parts of the structure.

3. Isolate the area. Place rag or paper towels around the spillage area to

keep globules within the original area. Prevent people walking through

area (if on aircraft floor) to prevent spread of mercury on footwear.

4. Remove source of contamination (broken instrument etc.) - carefully.

5. Remove globules by:

(a) Suction. Use a standard vacuum cleaner with a locally made up

‘liquid’ type trap in the suction line before the vacuum cleaner. (A

glass jar with a screw top lid and two pipes entering through

holes in the lid will do. Figure 26).

(b) A special pick-up brush. This is drawn lightly over the mercury

which will ‘pick up’ on the bristles. Shake the brush carefully into

a glass container.

(c) Foam pad. Pressing the pad into the mercury and releasing it will

cause it to suck up the mercury. Squeeze into a glass container

to remove the mercury from the pad.

(d) Adhesive tape. This will pick up the smaller globules.

(e) Chemical application. Mix up a thin solution of calcium

polysulphide. Mixing this with the mercury will convert the

mercury into an inert mercuric sulphide. Allow the mixture to dry

for 2 hours then vacuum up with a normal vacuum cleaner.

6. X-ray the area to check that all mercury has been removed.

7. Remove panels, de-rivet structure as necessary. Any contaminated drills

should be disposed off as contaminated products.

8. Apply a thin film of oil to area provided corrosion has not started. This

will help prevent the onset of corrosion but cannot be guaranteed to

stop it.

- 48 -

9. Where mercury attack has started on structure it will have to be

removed and a patch/insertion repair carried out. Use the SRM for the

aircraft, and it is important that all the affected area is removed - with

an extra allowance for safety. If the corroded area exceeds the repair

limits the panel must be replaced. Corroded components should be

changed, appropriately labelled and returned to the manufacturers.

10. Record and sign for the work in the log book.

11. Call up for a further inspection to be carried out in the Tech log – say, 3

to 4 days later.

Note. When disposing of mercury and mercury products it is important to

follow local regulations. The mercury should be kept in clearly marked

glass or ceramic containers - sealed and annotated as contaminated.

Contaminated clothing should be stored (dry) in plastic bags and labelled.

The mercury and contaminated material should end up at a special site

suitably equipped to be able to handle these products. Contact your local

authority/local waste contractor (a fee is likely).

GROUND SERVICE CONNECTIONS

Ground service connections include all those connections that are made to the

aircraft to provide power or some other form of supply/return service. These

connections could include:

* Refuelling/defuelling.

* Potable water (drinking water).

* Toilet system drains.

* Pitot/static systems.

* Pneumatic supply.

* Hydraulics – fill system provision and pressure supply and return

connections.

* Electrical connections.

Most of these are dealt with in the appropriate LBP book on the subject. Here we will

deal with just three – electrical, hydraulic and pneumatic ground supplies.

Pneumatic Ground Supplies

On some aircraft this would be taken as the supply of compressed gas for the

charging of gas bottles, oleos etc. On other aircraft the term ‘pneumatics’ would mean

the supply air for cabin air conditioning/pressurisation – usually from the

compressor side of the jet engine to the air conditioning packs/de-icing systems.

When dealing with compressed gas from pressurised transportation gas bottles

always check the following:

1. Check transportation bottles are within test date.

2. Ensure that the correct gas is used – air – nitrogen etc (check AMM).

3. Ensure system is serviceable to charge.

4. Charge slowly.

- 49 -

5. When using an adapter gauge always ensure that the pressure readings

from the various gauges – charging bottles, adapter, aircraft – all read

the correct reading. Stop the charging if readings do no correlate, and

investigate the reasons why.

6. Ensure that adapter gauge is within test date.

7. Allow pressure to stabilise after charging.

8. Check any pressure/temperature graphs.

9. Fit all blanks.

Air supplies for aircraft pneumatic systems can come from the engines, APU or

(whilst on the ground) from an engine driven ground supply trolley/cart. The duct

connection must be clean and the system must be checked that it is not pressurised

before connection is made. The system must also be checked that it is serviceable

before air supply commences.

The air supply cart should have a certificate of serviceability both in relation to it’s

motive power, exhaust emissions, and quality and rate of air supply.

When operating the unit ensure:

* A fire extinguisher is available.

* It is placed as far away from the aircraft as possible consistent with the

ability to connect the supply hose.

* Its air supply rate is within the parameters laid down in the AMM

(pressure and supply rate).

* When disconnecting ensure that the pressure is released.

* The aircraft is configured to accept the supply and the pneumatic

system is serviceable.

Electrical Ground Supplies

For dc supplies a set of batteries mounted on a trolley or an engine driven dc

generator may be used. The master switch on the trolley is off before connection is

made. The aircraft services switches are either off or their position corresponds with

the service selection – ie flaps up, selector switch up.

The AMM is consulted before power is applied.

The power supply plug (and the aircraft socket) may vary in design. A typical dc

supply plug is shown in figure 27. The plug consists of three pins, handed so it

cannot be fitted to the aircraft the wrong way round. The centre large pin is the main

supply pin, the other large pin is an earth/ground pin. The small pin is a relay

control pin. When plugged in and the master switch on, it supplies a small current to

operate a relay on the aircraft which switches out the aircraft battery supply and

switches in the external supply (centre pin) to the dc bus bars. It also causes a

cockpit indicator to show that external power is on.

When the external master switch is switched off the relay resets, external power is

switched off and internal power (batteries) are switched onto the bus bars.

For ac supplies an engine driven ground cart is used. The power supply socket

usually contains 6 pins, handed, so fitment to the aircraft can only be made in the

correct orientation.

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Fig. 27 EXTERNAL DC POWER SUPPLY PLUG

Three large pins are for the supply of the 3 phases, with the forth large pin being a

ground/earth connection. The two small pins are dc control pins which operate

relays on the aircraft to switch in/out the external power supply.

Figure 28 shows the external power panel of the B777. There are two power supply

connections – the primary and the secondary. The primary is to be used first with the

secondary being connected if more power is required. On many aircraft there is only

one external power connection.

Fig. 28 EXTERNAL ELECTRICAL POWER SUPPLY PANEL – B777

The panel shows the connection status of the supplies together with support

strapping for the (heavy) power supply cable.

In general, power supply panels may have the following equipment/indications:

* 3 external ac power circuit breakers.

* dc control circuit breakers.

* Power connected/power ON lights.

* Panel illumination lights, interphone socket and pilot’s call button.

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Figure 29 shows the indications on the flightdeck for power supply status. It is the

B777 electrical panel and is a good example of a large aircraft electrical supply

indicator. Note the status indications of the primary, secondary and APU supplies.

To connect power:

* Check the AMM.

* Ensure all systems are serviceable.

* Ensure all switches are off or set to the position of the service to which

they relate (to prevent any service from moving when power is switched

on).

* Check that supply cart engine is running correctly and voltage and

frequencies are correct. The same safety precautions apply here as for

any internal combustion engine powered equipment running in the

vicinity of aircraft.

* Insert ground power plug and support using restraining straps.

* Turn power on at the supply.

* Check ‘power available’ lights come on, on the aircraft panel. If they do

not then supply voltage or frequency may be a problem.

* If ‘power available’ lights are on, press ground service power switch on

panel to apply power to the aircraft ground service bus bar. Note

indications.

* Press the primary power switch to apply power to the aircraft power

supply bus bars. Note indications.

Fig. 29 ELECTRICAL POWER INDICATION

Hydraulic Ground Supplies

This could include refill connections, system selector valves etc, but we will

concentrate on the supply of external hydraulic power.

The hydraulic system may require the use of more that one external power test

rig/cart – check the AMM.

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The test rig/cart is usually powered by an internal combustion engine and should

meet the safety requirements applicable to all these type of engines when operating in

the vicinity of aircraft.

The test rig must be fitted with the same type of pump that is fitted to the aircraft -

constant volume (2 connections, pressure and return) or constant pressure (three

connections, pressure, return and idle lines) - or as specified in the AMM. The rig

must be run at the rpm as specified on the rig instruction panel to meet the pressure

and volume flow rate requirements as required by the aircraft system/s.

Fig. 30 HYDRAULIC EXTERNAL POWER PANEL OF THE AIRBUS AIRCRAFT

The test rig should be checked to see if it contains the correct hydraulic fluid –

normally marked on a plate fixed to the rig – if it doesn’t, get a rig that does. It is

connected to the aircraft using hoses with self-seal quick release connections. They

are sized so that the hoses cannot be cross-connected:

* For 2 hose connections (constant volume pump). Large = suction line.

Small = pressure line.

* For 3 hose connections (constant pressure pump). Large = suction line.

Medium = pressure line. Small = idling line.

Check the following when connecting/disconnecting hydraulic power:

1. Check the AMM.

2. Carry out the normal safety precautions in relation to the running of an

internal combustion engine in the vicinity of aircraft.

3. Check that the hydraulic system and all associated systems are

serviceable and ready to be tested (fluid levels, accumulator gas

pressures, completeness etc).

4. If the landing gear is to be tested the aircraft should be on jacks and

suitably trestled/shored.

5. Check flight deck selectors correspond with actual position of systems.

6. Have electrical power on.

7. Connect hydraulic hoses.

8. Start hydraulic test rig – adjust to correct rpm – allow to warm-up.

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9. Operate clutch to engage pump – note that no services move. If they do,

either dis-engage the pump or note they are supposed to move and are

prepared for it (check AMM).

10. Check pressure gauges, low pressure warning lamps etc in the flight

deck.

11. After all testing is completed and the landing gear is locked down with

‘3

greens’ showing the clutch can be dis-engaged and the rig shut down.

12. Using a ‘C’ spanner or special tool to undo the self-seal couplings.

13. No fluid should leak, but if it does then ensure the self seal coupling

seals correctly and the leak stops, fit the blank and check the level of

the reservoir.

””””””

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APPENDIX – ESSAY QUESTIONS

This appendix has been added to provide the reader with some idea as to the essay

questions being asked by the CAA, and the answers. This has been thought

necessary because the areas being asked questions on are actually in other modules

(principally jet engines module 15 and airframes module 11). But because the way

the syllabus is written it has meant that the CAA can include them in module 7.

Module 7 syllabus states, amongst other things, “Types of defects and visual

inspection techniques” (BI and B2) and “Inspections following abnormal events such

as heavy landing and flight through turbulence” (B1).

The answers given here are our own and you must give your own in any CAA

answers. They are quick to pick up what are called ‘model answers’ and

memorised/copied answers come into that group.

Our answers are an answer to the question but also include information about the

question – which helps you to learn. It is most important that when you answer any

CAA question that you answer that question and not one you think it is, or should be.

Note that some of the information in the answers might be better understood if the

appropriate book is read in the module 11 or 15.

Note also that we produce an EE programme specifically written to cover the essay

questions for modules 7, 9 and10. It provides a guide as to the technique of the essay

answer and gives the student questions to be attempted. When completed they are

returned to the appropriate LBP tutor for marking and comment. The programme

also contains a list of the sort of questions asked and indications as to the answers.

The questions in this book are additional to those in our EE programme with question 1 being almost certainly for the B1 person only.

1. QUESTION. The pilot reports a smell from the flight deck air conditioning system.

Detail the possible causes and state your action to clear the aircraft for flight.

Confirm if it is a burning smell. Confirm if it is an electrical smell, an oil smell, a

hydraulic smell or a debris smell and that its actually coming from the air

conditioning ducts.

Check for any shorting of electrical parts in any part of the air conditioning system –

any part of the system up to the mixing chamber where the cold air (after the air

cycle turbine) meets the hot air from the engine/engine compressor, and carry out

any BITE checks.

Change any overheated wiring/electrical components as per the AMM.

If an engine oil smell, and air tapped from the engine carry out investigation as to

engine/s oil consumption over past few flights and any reports of engine/s over-

heating. Carry out a visual check of engine oil seals. Change engine if found

defective. If hydraulic smell check the hydraulic reservoir pressurisation system (non-

return valves in particular) and rectify as necessary.

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If air delivered from engine driven compressor check compressor oil seals and

compressor for over-heating. Change compressor if found defective. Check engine

overheat detectors/air duct temperature detectors (recorded on aircraft fault

computer if fitted) and take appropriate action.

For heating systems that use heat exchangers using engine exhaust pipes as the heat

source and combustion heaters check heat exchangers for leaks and change if

defective. Check CO2 detectors in cabin for correct operation.

Examine combustion heaters for serviceability and correct operation and leakage.

Change if not functioning correctly.

If smell is a debris type smell check ducts for cleanliness, change all air filters,

change coalescer in water separator and check all lagging for dampness and smell.

Check cold air unit for oil leaks. Change if found.

Record all work done and certify and issue CRS.

2. QUESTION. Describe how you would check for water contamination in fuel and

what other checks would you carry out at the same time. Checking for fuel contamination in not actually in the module 7 syllabus, though refuelling/de-fuelling is. The CAA have asked essay questions based on fuel sampling on both B1 and B2 examinations.

To check for water contamination proceed as follows:

1. Allow the aircraft to stand for a few hours after refuelling.

2. Ensure the aircraft is in the attitude as laid down in the AMM -

usually laterally level and longitudinally as specified.

3. Using a clean glass container (clean using alcohol isopropyl) drain

each aircraft tank in turn from its drain valve until no more water

comes out with the fuel. Use the drain valves provided and/or a purging

tool (AMM).

If unsure if water is present use a colour indicator (eg a soluble food

colouring) is added to the container which will show up the water as a

colour. Alternatively a water detector kit may be used, eg the Shell

Water Detector kit. Also a hydrometer may be used to check the specific

gravity.

Any water present may show up as suspended droplets which will make

the fuel show up as cloudy when looked at using a back-light. Free

water will show up as larger droplets or a layer of water at the bottom of

the glass. If water is found continue to drain until all water is removed.

4. If the amount drained is within normal limits as per the AMM discard

the drained liquid as laid down in the local airfield regulations.

5. Close and lock drain valve. Secure panel and record details in the

aircraft log book.

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6. If excessive water is present carry out the following:

* Refer to the AMM and/or the aircraft manufacturer for any

specific instructions.

* Wait a further period of time and drain each tank again.

Take note if significantly more water came from one tank

more than the others. This might mean local rain water

ingress or tank water ejector failure.

* Get the fuel supplier to check the fuel supplied either in

the tanker (bowser) of from the bulk underground supply

system. Get a report from the supplier. (Tankers/fuel

supplies should be water drained at least daily). If it is a

bulk fuel supply problem then this must be rectified by the

supplier.

* Check for obvious signs where water (rain water) could get

into the aircraft tank (rare). Rectify as necessary.

* Check that the automatic sumping pump (water

ejector/ejector pump) is working. If not change.

* Check the Tech Log to see if pilot reports include any

engine problems.

* If fuel is seriously contaminated (which is rare) then the

tanks must be drained and refilled with ‘good’ fuel, the

airframe system re-primed, the engine/s system/s re-

primed and an engine run carried out.

Remember that the fuel will be drained back into the

bowser so the bulk fuel supplier must be informed why the

aircraft tanks are being drained.

If the contamination is the bulk fuel supplier’s fault then

there will be some financial adjustment to the aircraft

operator’s fuel account.

* All work carried out on the aircraft must be recorded and

signed for in the airframe and engine log books.

* Consult the bulk fuel supplier re the disposal/treatment

of the drained fuel.

7. If bacteria contamination suspected carry out a microbe/fungus

detection check as follows:

* From the tank drain, drain a small quantity of fuel into a

clean container.

* Use a commercially available tester kit as per the AMM.

* Put a fuel sample in each of two clean glass containers (1

and 2). One container (say container 2) will have a

quantity of biocide added from the tester kit. +

* Cover and allow the two containers to stand for 48 hours.

If there is a colour change in container 2 then there is fuel

contamination.

* Check all remaining tanks. Any that show contamination

must be drained and inspected internally for

discolouration (brown or black), corrosion or any

deterioration. Any damage must be repaired as per the

AMM/SRM or the tank replaced.

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* Check fuel system components (including filters) for

internal damage and debris blockage. Clean/replace as

necessary.

* Carry out an engine run if any components have been

replaced.

* Carry out any duplicate inspections as necessary.

* Record all work done in the aircraft/engine log book/s and

sign.

+ Some kits use detection papers.

While carrying out a water sampling test it would be obvious to also check for

other contaminants besides bacteria. If debris is found such as particles of metal,

rubber, etc then further checks are to be made, eg:

1. Check the AMM/engine manufacturers manual.

2. Check the fuel filters.

3. Check the oil filters and any magnetic plugs.

4. Depending on what is found in the filters determine if any

component (fuel tank, bearing, pump etc) is breaking up.

5. Carry out a particulate laboratory test such as a SOAP

(Spectrometric Oil Analysis Programme) test to determine

what the particles are and what component/s they came

from (up to 11 elements can be detected by these tests).

6. Change the offending component/s.

7. Depending on the size, the amount and the source of the

debris the engine/s may have to be changed and returned

for overhaul. The system may also have to be flushed out

depending on where the particles originated from –

pumping clean fuel from the fuel tanks to an open fuel

pipe at the engine.

8. If not too severe carry out an engine run and carry special

checks for fuel/oil contamination over the next few flights.

The above answer is long and the author would not expect that this amount of information can be written down in the time allowed in the examination, but it is comprehensive and provides the reader with a sound background as to how fuel contamination can be examined for.

””””””

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