(6) Oral Basic Gas Turbine - AME

11/13/13 Oral Basic Gas Turbine - Aircraft Maintenance Engineering

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AIRCRAFT MAINTENANCE ENGINEERING

WE MAKE THE METAL FLY!

ORAL BASIC GAS TURBINE

Following are the questions usually asked in orals, they will be updated from time to time, so keep on v isiting

regularly . Thank y ou

QUESTIONS

Standard Definitions:

MASS: Mass is a quantity of matter in a body . Units MKS – kg; CGS – gm; FPS – lb(mass). Scalar

quantity .

MATTER: Any thing that occupies space (volume) and have mass

RATIO: One magnitude div ided by another magnitude of the same kind

MOLECULE: Molecule is a combination of two or more atoms.

COMPOUND: It is a chemical combination of molecules. E.g. NACL

MIXTURE: It is a phy sical combination of molecules. E.g. Brine

ALLOY : An alloy is a partial or complete solid solution (http://en.wikipedia.org/wiki/Sol id_solu tion) of one or

more elements (http://en.wikipedia.org/wiki/Chemical_element) in a metallic (http://en.wikipedia.org/wiki/Metal l ic)matrix

(http://en.wikipedia.org/wiki/Matrix_%28geology%29). Complete solid solution alloy s give single solid phase

microstructure, while partial solutions give two or more phases that may be homogeneous

(http://en.wikipedia.org/wiki/Homogeneou s_%28chemistry%29) in distribution depending on thermal (heat treatment)

history . Alloy s usually have different properties from those of the component elements.

ION: Ions are the charged particle

PLASMA: Plasma is an ionized state. It is a combination of liquid and solid state of matter and occurs at

very high temperature

FLUID: Any thing that can flow.

COHESION: It is a force of attraction between same ty pe of atoms and molecules

ADHESION: It is a force of attraction between different ty pe of atoms and molecules.

SPECIFIC GRAVITY :

It is the ratio of a density of a substance to the density of water. Density of water is 1000

kg/m3

Hu ssa in Sig n Ou t

http://aircraftmaintenanceengineering.webs.com/

http://en.wikipedia.org/wiki/Solid_solution

http://en.wikipedia.org/wiki/Chemical_element

http://en.wikipedia.org/wiki/Metallic

http://en.wikipedia.org/wiki/Matrix_%28geology%29

http://en.wikipedia.org/wiki/Homogeneous_%28chemistry%29

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1 NAUTICAL MILE:

The arc along the circle of the earth if the angle substanded is equal to one minute.

1 KNOT: A knot is one nautical mile covered in one hour. It is a unit of speed and is used in av iation.

MINUTE: In astronomy (http://en.wikipedia.org/wiki/A stronomy), the minute is a unit of angle, the minute of

right ascension (http://en.wikipedia.org/wiki/Right_ascension). It is equal to 1/60th of an hour of right ascension and

can be further div ided into 60 seconds of right ascension.

DISPLACEMENT:

Shortest distance between two locations or points. It is a vector quantity .

DISTANCE: It is the amount of travel. Scalar quantity .

SPEED: Distance covered in a unit time or rate of change of distance. Speed = Distance / time. Units

MKS – m/s; CGS – cm/s; FPS – ft/s. Scalar quantity

VELOCITY : Rate of change of displacement. Units MKS – m/s; CGS – cm/s; FPS – ft/s. Vector quantity .

V=s/t

(Difference between speed and velocity is of distance and displacement)

INSTANTANEOUS VELOCITY :

Velocity at some instance.

ACCELERATION:

Rate of change of velocity . Units MKS – m/s2; CGS – cm/s2; FPS – ft/s2. Vector quantity . a=

vf-v i /t.

REST: If a body doesn’t change its position wrt to its surrounding the body is said to be in rest

MOTION: If a body changes its positin wrt to its surrounding the body is said to be in motion.

TY PES OF MOTION:

1. Translatory Motion: A motion in which every particle of a body is being displaced by the same amount is

called Translatory motion. E.g. a car.

2. Rotational Motion: A motion in which a body rotates about a fixed point or axis. E.g. a fan.

3. Oscillatory or Vibratory Motion: to and fro motion of a body about a mean position. E.g. Pendulum.

EQUATIONS OF MOTION:

1. Vf = Vi + at

2. S = Vit + ½ at2

3. 2as = Vf2 – Vi2

NEWTON’S LAWS OF MOTION:

1. First Law of motion: A body at rest will remain at rest and a body in motion will continue its state of

uniform motion unless some force is applied.

2. Second Law of motion: When an external force acts on a body it accelerates the body in the direction of

force. Acceleration of an object is directly proportional to the force acting on it and inversely proportional to

the mass of the object.

http://en.wikipedia.org/wiki/Astronomy

http://en.wikipedia.org/wiki/Right_ascension



3. Third Law of motion: To every action there is an equal and opposite reaction.

FORCE: Force is that agent which produces or tends to produce, stops or tends to stop motion in a

body . Units MKS – Newton (kg.m/s2); CGS – Dy ne (g.cm/s2); FPS – Pound (force) (lb(mass). ft/s2. Vector

quantity . F=ma.

WEIGHT: Weight is a force with which earth attracts a body towards its center. Units MKS – Newton

(kg.m/s2); CGS – Dy ne (g.cm/s2); FPS – Pound (force) (lb(mass). ft/s2. Vector quantity . W=mg.

NEWTON’S LAW OF GRAVITIATION:

Every body in the universe attracts every other body with a force which is directly

proportional to the product of their masses and inversely proportional to the square of distance between

them. F=G m1.m2/r2. G=6.67 x10 power -11 .

SCALER QUANTITIES:

Scalar quantities are those quantities that have magnitude only but no direction. E.g. mass,

speed, time, volume, temperature, work, density , distance. Scalars can be added subtracted, multiplied and

div ided according to ordinary arithmetic rules.

VECTOR QUANTITIES:

Vector quantities are those quantities that have both magnitude and direction. E.g. Force,

velocity , weight, displacement, acceleration, momentum. Graphically a vector can be added or subtracted by

head to tail rule.

TRIGNOMETERY :

1 . Sin theta = Prependicular / Hy potenuse

2. Cos theta = Base / Hy potenuse

3. Tan theta = Perpendicular / Base

ENERGY : Energy is the capacity to do work. It is inherent Power

POWER: Power is the rate of doing work. P= F x D

T

It is calculated in foot pounds per second Or Watts.

WORK: Act of performing a productive operation by some mechanical means.

TORQUE: Torque is the twisting or rotary force exerted by the engine to turn the Propeller.

RPM: Number of Revolutions per minute

BOY LE’S LAW: Boy le’s law states that at constant temperature, the absolute pressure and the volume of a

gas are inversely proportional. PV = K

CHARLES LAW: At constant pressure, the volume of a given mass of an ideal gas is directly proportional to its

absolute temperature. V @ T

PRESSURE: Pressure is a force per unit area. Its unit in MKS is N/m2 and FPS is Psi. P=F/A

KINDS OF PRESSURES:



Absolute pressure is the sum of gauge pressure & atmospheric pressure. It is the actual pressure of a

fluid on surface because of the force exerted by the molecules. It is zero referenced against a perfect

vacuum. It is never negative.

· Gauge pressure is equal to absolute pressure minus atmospheric pressure. It is zero referenced against

ambient air pressure, so Negative signs are usually omitted. It can show the negative reading.

· Atmospheric Pressure is the pressure of the outside air which is 14.7 psi at sea level.

· Differential pressure is the difference in pressure between two points.

· Ram or Dy namic Pressure is the pressure of the air or gas cause by motion is called Ram or Dy namic

pressure.

· Static Pressure in fluid dy namics (http://en.wikipedia.org/wiki/Flu id_dynamics), static pressure is the pressure

(http://en.wikipedia.org/wiki/Pressu re) at a nominated point in a fluid. Static pressure is the true pressure of a gas.

Aneroid barometer measures static pressure.

· Total Pressure is the sum of Dy namic pressure and Static Pressure.

· Hy drostatic Pressure is the pressure due to the height of the fluid. Its unit in MKS is Pascal (N/m2) and

FPS is Psi, also bar. P=egh.

IDEAL GAS LAW: The combined gas law (http://en.wikipedia.org/wiki/Combined_gas_law) or general gas equation is

formed by the combination of the three laws, and shows the relationship between the pressure, volume and

temperature for a fixed mass of gas:

Three earlier gas laws:

Boy le's law (http://en.wikipedia.org/wiki/Boyle%27s_law) (1662, relating pressure and volume):

,

Charles' law (http://en.wikipedia.org/wiki/Charles%27_law) or law of volumes (17 87 , relating volume and

temperature):

Pressure law or Third gas law (Gay -Lussac (http://en.wikipedia.org/wiki/Gay-Lu ssac%27s_Law) in 1809, relating

temperature and pressure)

The combined gas law (http://en.wikipedia.org/wiki/Combined_gas_law) or general gas equation is formed by the

combination of the three laws, and shows the relationship between the pressure, volume and temperature for

a fixed mass of gas:

There is also Avogadro's Law (http://en.wikipedia.org/wiki/A vogadro%27s_Law), which is particularly useful in

chemistry : For any gas, the ratio of Liters of the gas to moles of the gas is:

http://en.wikipedia.org/wiki/Fluid_dynamics

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/Combined_gas_law

http://en.wikipedia.org/wiki/Boyle%27s_law

http://en.wikipedia.org/wiki/Charles%27_law

http://en.wikipedia.org/wiki/Gay-Lussac%27s_Law


http://en.wikipedia.org/wiki/Avogadro%27s_Law



, and uses the molar volume (http://en.wikipedia.org/wiki/Molar_volu me) of a gas: 22.4 Liters.

With the addition of Avogadro's law (http://en.wikipedia.org/wiki/A vogadro%27s_law), the combined gas law

(http://en.wikipedia.org/wiki/Combined_gas_law) developed into the ideal gas law

(http://en.wikipedia.org/wiki/Ideal_gas_law):

This law has the following important consequences:

1 . If temperature and pressure are kept constant, then the volume of the gas is directly proportional to

the number of molecules of gas.

2. If the temperature and volume remain constant, then the pressure of the gas changes is directly

proportional to the number of molecules of gas present.

3. If the number of gas molecules and the temperature remain constant, then the pressure is inversely

proportional to the volume.

4. If the temperature changes and the number of gas molecules are kept constant, then either pressure or

volume (or both) will change in direct proportion to the temperature.

IDEAL GAS: An ideal gas is a theoretical gas composed of a set of randomly -moving point particles

(http://en.wikipedia.org/wiki/Point_particle) that interact only through elastic collisions

(http://en.wikipedia.org/wiki/Elastic_col l ision). The ideal gas concept is useful because it obey s the ideal gas law

(http://en.wikipedia.org/wiki/Ideal_gas_law), a simplified equation of state (http://en.wikipedia.org/wiki/Equ ation_of_state),

and is amenable to analy sis under statistical mechanics (http://en.wikipedia.org/wiki/Statistical_mechanics).

ENTROPY : It is the degree of molecular disorder.

TEMPERATURE:

It is the degree of hotness or coldness of a body .

TEMPERATURE SCALES:

Marks Degree Celsius Degree Fahrenheit Degree Kelv in

Min 0 32 27 3

Max 100 212 37 3

Parts 100 180 100

Conversion Degree Celsius Degree Fahrenheit Degree Kelv in

Celsius 5/9 (F-32) +27 3

Fahrenheit 9/5 C + 32 +27 3

http://en.wikipedia.org/wiki/Molar_volume

http://en.wikipedia.org/wiki/Avogadro%27s_law


http://en.wikipedia.org/wiki/Ideal_gas_law

http://en.wikipedia.org/wiki/Point_particle

http://en.wikipedia.org/wiki/Elastic_collision

http://en.wikipedia.org/wiki/Ideal_gas_law

http://en.wikipedia.org/wiki/Equation_of_state

http://en.wikipedia.org/wiki/Statistical_mechanics



Kelv in +27 3 +27 3

Degree Celcius – Degree Farenhiet – Degree Kelv in

COEFFICIENT OF LINEAR EXPANSION:

It is change in length per unit length per degree rise in Kelv in.

COEFFICIENT OF VOLUME EXPANSION:

It is change in volume per unit volume per degree rise in Kelv in.

DALTON’S LAW of Partial Pressures:

The pressure of a mixture of gases simply is the sum of the partial pressures

(http://en.wikipedia.org/wiki/Partial_pressu res) of the indiv idual components.

PASCAL’S LAW: When a fluid is confined in a container or a sy stem and its pressure is increased or decreased

by means of a piston or some other mean, then it is observed that the pressure at every point within the

sy stem is changed by the same amount.

PASCAL: Pascal is a force of one Newton on an area of one meter square. N/m2. 14.7 psi = 1 .103 x 10

power 5 Pascal. One bar is equal to 10 power 5 Pascal.

HOOK’S LAW: Hooke's law of elasticity (http://en.wikipedia.org/wiki/Theory_of_elastici ty) is an approximation that

states that the extension of a spring is in direct proportion with the load added to it as long as this load does

not exceed the elastic limit. Materials for which Hooke's law is a useful approximation are known as linear-

elastic (http://en.wikipedia.org/wiki/Linear_elastici ty) or "Hookean" materials.

Mathematically , Hooke's law states that

where

x is the displacement (http://en.wikipedia.org/wiki/Displacement_%28vector%29) of the end of the spring from its

equilibrium (http://en.wikipedia.org/wiki/Mechanical_equ i l ibriu m) position;

F is the restoring force exerted by the material; and

k is the force constant (or spring constant).

OHM’S LAW:

In electrical circuits (http://en.wikipedia.org/wiki/Electrical_circu it), Ohm's law states that the current

(http://en.wikipedia.org/wiki/Electric_cu rrent) through a conductor between two points is directly proportional

(http://en.wikipedia.org/wiki/Proportional i ty_%28mathematics%29) to the potential difference

(http://en.wikipedia.org/wiki/Potential_difference) or voltage (http://en.wikipedia.org/wiki/V oltage) across the two points,

and inversely proportional to the resistance (http://en.wikipedia.org/wiki/Electrical_resistance) between them,

provided that the temperature remains constant.[1 ] (http://en.wikipedia.org/wiki/Ohm%27s_law#cite_note-0)

http://en.wikipedia.org/wiki/Partial_pressures

http://en.wikipedia.org/wiki/Theory_of_elasticity

http://en.wikipedia.org/wiki/Linear_elasticity

http://en.wikipedia.org/wiki/Displacement_%28vector%29

http://en.wikipedia.org/wiki/Mechanical_equilibrium

http://en.wikipedia.org/wiki/Electrical_circuit

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Proportionality_%28mathematics%29

http://en.wikipedia.org/wiki/Potential_difference

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Electrical_resistance

http://en.wikipedia.org/wiki/Ohm%27s_law#cite_note-0



The mathematical equation that describes this relationship is:[2 ]

(http://en.wikipedia.org/wiki/Ohm%27s_law#cite_note-Mil l ikan-1)

KRISCHOFF’S LAW:

Kirchhoff's circuit laws are two equalities (http://en.wikipedia.org/wiki/Equ al i ty_%28mathematics%29) that deal with

the conservation of charge (http://en.wikipedia.org/wiki/Charge_conservation) and energy in electrical circuits

(http://en.wikipedia.org/wiki/Electrical_circu it), and were first described in 1845 by Gustav Kirchhoff

(http://en.wikipedia.org/wiki/Gu stav_Kirchhoff). Widely used in electrical engineering

(http://en.wikipedia.org/wiki/Electrical_engineering), they are also called Kirchhoff's rules or simply Kirchhoff's laws

(see also Kirchhoff's laws (http://en.wikipedia.org/wiki/Kirchhoff%27s_laws) for other meanings of that term).

COLOUMB’S LAW:

The magnitude of the electrostatic force between two point (http://en.wikipedia.org/wiki/Point_sou rce) electric

charges is directly proportional (http://en.wikipedia.org/wiki/Proportional i ty_%28mathematics%29) to the product of the

magnitudes of each of the charges and inversely proportional to the square of the distance between the two

charges

BUOY ANCY FORCE:

Buoy nacy force is an upward thrust. It depends upon the weight of the volume of the fluid displaced by the

body . It is used in hy drometer to determine the specific grav ity of the liquids. E.g. battries. Floating bodies

have a greater buoy ancy force then their weight. Aircrafts that fly due to buoy ancy force are balloons and

airships.

STREAM LINE FLOW:

When a fluid flows through a duct in such a way that there is no turbulence in the flow, the flow is said to be

streamline.

VENTURI: Venturi is a streamline duct through which air will flow without turbulence. The bore of

venture converges upto throat and diverges towards the outlet.

CONTINUITY OF FLOW:

Fluids in steady motion pass each cross-section of the streamline duct in identical amount in

each second.

Continuity of flow is when the mass flow rate is constant

m = eAV e=density , A=Area, V=Velocity .

BERNAULI’S THEOREM:

In streamline flow of ideal fluid (inv icid – nonviscous fluid), the sum of Kinetic Energy ,

Potential Energy and Pressure Energy remains same.

BRAY TON CY CLE:

The Bray ton cy cle is a thermody namic cy cle (http://en.wikipedia.org/wiki/Thermodynamic_cycle) that describes the

workings of the gas turbine (http://en.wikipedia.org/wiki/Gas_tu rbine) engine, basis of the jet engine

(http://en.wikipedia.org/wiki/Jet_engine) and others. It is named after George Bray ton

(http://en.wikipedia.org/wiki/George_Brayton) (1830–1892), the American engineer (http://en.wikipedia.org/wiki/Engineer)

http://en.wikipedia.org/wiki/Ohm%27s_law#cite_note-Millikan-1

http://en.wikipedia.org/wiki/Equality_%28mathematics%29

http://en.wikipedia.org/wiki/Charge_conservation

http://en.wikipedia.org/wiki/Electrical_circuit

http://en.wikipedia.org/wiki/Gustav_Kirchhoff

http://en.wikipedia.org/wiki/Electrical_engineering

http://en.wikipedia.org/wiki/Kirchhoff%27s_laws

http://en.wikipedia.org/wiki/Point_source

http://en.wikipedia.org/wiki/Proportionality_%28mathematics%29

http://en.wikipedia.org/wiki/Thermodynamic_cycle

http://en.wikipedia.org/wiki/Gas_turbine

http://en.wikipedia.org/wiki/Jet_engine

http://en.wikipedia.org/wiki/George_Brayton

http://en.wikipedia.org/wiki/Engineer



who developed it, although it was originally proposed and patented by Englishman John Barber

(http://en.wikipedia.org/wiki/John_Barber_%28engineer%29)[1 ] (http://en.wikipedia.org/wiki/Brayton_cycle#cite_note-0) It is also

sometimes known as the Joule (http://en.wikipedia.org/wiki/James_Prescott_Jou le) in 17 91. cy cle.

The term Bray ton cy cle has more recently been given to the gas turbine (http://en.wikipedia.org/wiki/Gas_tu rbine)

engine. This also has three components:

A gas compressor

A burner (or combustion (http://en.wikipedia.org/wiki/Combu stion) chamber)

An expansion turbine (http://en.wikipedia.org/wiki/Expansion_tu rbine)

Ideal Bray ton cy cle:

isentropic process (http://en.wikipedia.org/wiki/Isentropic_process) - Ambient air is drawn into the compressor,

where it is pressurized.

isobaric process (http://en.wikipedia.org/wiki/Isobaric_process) - The compressed air then runs through a

combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the

chamber is open to flow in and out.

isentropic process (http://en.wikipedia.org/wiki/Isentropic_process) - The heated, pressurized air then gives up

its energy , expanding through a turbine (or series of turbines). Some of the work extracted by the

turbine is used to drive the compressor.

isobaric process (http://en.wikipedia.org/wiki/Isobaric_process) - Heat Rejection (in the atmosphere).

Actual Bray ton cy cle:

adiabatic process (http://en.wikipedia.org/wiki/A diabatic_process) - Compression.

isobaric process (http://en.wikipedia.org/wiki/Isobaric_process) - Heat Addition.

adiabatic process - Expansion.

isobaric process - Heat Rejection.

HORSE POWER: Horse Power is a unit of Power. One Horse Power is 550 foot-pounds of work accomplished in

one second. (37 5 mile pound per hour = 550 ft. lbs / sec = 33,000 ft. lbs / min). Both time and distance are

necessary to compute Horse Power.

The term, Horse Power is not used for turbo-fan or turbo-jet engines because time and distance elements are

not alway s involved, since when a turbo-jet or turbo-fan is not moving forward as like a plane standing on

ground with engines running, time and distance elements are zero.

POWER OF A GAS TURBINE ENGINE:

Power of a gas turbine engine can only be calculated if the aircraft

is moving, when thrust is opposing drag & propelling the aircraft at a constant speed. Power of a gas turbine

engine is given by :

Power = Drag (lbs) X Aircraft speed (ft / sec)

OR

Since at a constant aircraft speed Thrust = Drag so,

Thrust Horse Power = Thrust (lbs) x Aircraft Speed (ft / sec)

550 ft. lbs / sec

http://en.wikipedia.org/wiki/John_Barber_%28engineer%29

http://en.wikipedia.org/wiki/Brayton_cycle#cite_note-0

http://en.wikipedia.org/wiki/James_Prescott_Joule

http://en.wikipedia.org/wiki/Gas_turbine

http://en.wikipedia.org/wiki/Combustion

http://en.wikipedia.org/wiki/Expansion_turbine

http://en.wikipedia.org/wiki/Isentropic_process

http://en.wikipedia.org/wiki/Isobaric_process

http://en.wikipedia.org/wiki/Isentropic_process


http://en.wikipedia.org/wiki/Adiabatic_process




37 5 mile pound per hour = 550 ft. lbs / sec = 33,000 ft. lbs / min

Power of a Gas Turbine engine is calculated as THRUST HORSE POWER, because this engine delivers power

through thrust generated by the reaction force.

GAS TURBINE ENGINES:

Gas Turbine Engines are simple heat engines that convert heat energy of fuel into mechanical

work.

They are machines which give momentum to the mass of air & fuel.

GAS GENERATOR:

A gas generator is a gas producing section of a gas turbine engine. It excludes inlet duct, propelling nozzle of a

turbo jet & propeller shaft and reduction gear of turbo-prop engines.

THRUST: Thrust is a forward acting force and is a reaction force to the force applied to accelerate the

mass of air rearward in case of a gas turbine engine. It is measured in pounds.

MOMENTUM THRUST:

Momentum Thrust is the Majority of the thrust. It is obtained by the change of momentum of gasses within an

engine.

PRESSURE THRUST:

Pressure thrust is an additional thrust obtained when the engine operates with the propelling nozzle in a

choked condition. It is obtained by the pressure difference at the propelling nozzle and the outside

atmosphere.

Pressure Thrust = (Pressure at the jet nozzle Pj – Ambient Pressure Pam) x Jet nozzle area.

GROSS THRUST:

Pressure Thrust added to Momentum thrust prov ides Gross Thrust.

THRUST HORSE POWER:

Thrust Horse Power is defined that at an aircraft speed of 550 ft. lbs / sec the thrust of one

pound is equal to one horse power.

Power of a Gas Turbine engine is calculated as THRUST HORSE POWER, because this engine delivers power

through thrust generated by the reaction force.

For a Turbo-jet & turbo-fan engine:

Thrust Horse Power = Thrust (lbs) x Aircraft Speed (ft / sec)

550 ft. lbs / sec

37 5 mile pound per hour = 550 ft. lbs / sec = 33,000 ft. lbs / min

Thrust Horse Power is proportional to both engine thrust and aircraft speed. If the aircraft speed is zero THP



is also zero. Likewise if aircraft speed for a given thrust is doubled, THP is also doubled.

For a Turbo-prop engine:

Thrust Horse Power = Shaft Horse Power x Propeller efficiency

Thrust horse power developed by a turbo-prop will alway s be less than its Shaft horse power because the

propeller is less than 100 percent efficient (it is usually 80 % efficient), converting only part of the horse

power output into thrust.

SHAFT HORSE POWER:

Shaft Horse Power is the measure of power supplied to the propeller in a turbo-prop-engine.

One SHP supplied to the propeller is assumed to produce 2.5 pounds of thrust.

EQUIVALENT SHAFT HORSE POWER:

Equivalent Shaft Horse Power is the power produced by a Turbo-prop engine.

Equivalent Shaft Horse Power is Shaft Horse Power supplied to the propeller plus the amount of thrust

produced by the engine.

The static Equivalent Shaft Horse Power is the static jet thrust in pounds div ided by 2.5 plus the SHP supplied

to the propeller.

ESHP (static) = SHP + Fn (Jet)

2.5

EFFICIENCY : Efficiency is the effectiveness with which a machine, piece of equipment, process or a person

operates.

It is the ratio of the energy obtained from a machine to the energy put into the machine.

ENGINE EFFICIENCY :

Engine efficiency is the over-all efficiency of an engine which is usually between 7 0-80%. Each

part of an engine such as compressor, combustion chamber, turbine, jet nozzle has its own efficiency . All of

these combine to produce one single Over-all or Engine efficiency .

To assess the engine or over-all efficiency of an engine Thermal or internal efficiency and Propulsive or

external efficiency of the installed engine must be considered. Over –all Efficiency is a product of Thermal

efficiency and Propulsive efficiency

Over-all efficiency = Thermal efficiency x Propulsive efficiency

MECHANICAL EFFICIENCY :

Mechanical efficiency is the ratio of the useful work output of a machine to the work or energy

input.

Mechanical efficiency = Useful work output

Work Input

The difference between the two values is chiefly due to the mechanical frictional losses and losses like air

leakages etc.



THERMAL EFFICIENCY :

Thermal efficiency of an engine is the ratio of useful work output to the heat of combustion of the fuel.

Thermal efficiency = Useful work output

Heat of combustion of the fuel

Thermal efficiency is affected by the temperature drop across the turbine.

The more is the Turbine Entry Temperature (TET), the more will be the energy to do work or more will be the

Thermal Efficiency .

Thermal efficiency (Or Turbine Entry Temperature TET) is a function of (or depends on):

1 . Pressure Ratio 2. Mass of Airflow 3. Temperature to which the air is heated.

OPERATING CY CLE EFFICIENCY :

Operating cy cle efficiency is the ratio of the amount of useful work obtained from a jet engine’s actual cy cle to

the amount of useful work obtained from the same ideal cy cle.

Actual efficiency is alway s less than the ideal.

PROPULSIVE EFFICIENCY :

Propulsive efficiency can be defined as that proportion of the engine work that can be converted into aircraft

work.

Propulsive efficiency can also be defined as the amount of thrust developed by the jet nozzle compared with

the energy supplied to it in the usable form.

Propulsive efficiency is related to an engine installed on the airframe.

Propulsive efficiency indicates how effective an engine is as a propelling unit. If the aircraft is stationary ,

regardless of the amount of thrust produced, the fuel consumed is wasted as far as the aircraft propulsion is

concerned, infact the propulsive efficiency would be zero. But if aircraft speed becomes equal to the jet speed

the Propulsive efficiency would be 100%. Thrust will be zero in that case.

Propulsive efficiency increases as the difference between the aircraft speed and the jet velocity decreases.

The faster the aircraft flies the closer the jet speed and the aircraft become, and the energy put into the jet

stream performs more useful work.

Propulsive efficiency is said to increase when at higher throttle settings the nozzle becomes choked so there is

a very little increase in the jet velocity (Vj), so the gap between the jet velocity and the aircraft speed

narrows.

Propulsive efficiency = Work done on the aircraft x 100%

Work done on the gas stream

Or,

Propulsive efficiency = twice aircraft speed x 100%

aircraft speed + Jet speed

prop. eff = 2Vi/(Vj+Vi)



Question: Why does Propulsive efficiency increases when difference between the aircraft speed and Jet speed

decreases?

Answer: Because the purpose of the engines is to propel the aircraft as much as it can. The more they are

closer to their purpose the more will be the propulsive efficiency .

SPECIFIC FUEL CONSUMPTION (SFC) OR THRUST SPECIFIC FUEL CONSUMPTION (TSFC):

Specific Fuel Consumption (SFC) is the amount of fuel required to generate one pound of thrust in one hour

for a turbo-jet & turbo-fan engines.

TSFC = fuel flow in lbs / lb of thrust / hour

Specific Fuel Consumption (SFC) is the amount of fuel required to generate one Shaft Horse Power (SHP) in

one hour for a turbo-prop engine.

SFC = fuel flow / SHP / hour

Specific Fuel Consumption (SFC) is the measure of an engine’s thermal efficiency and performance.

Low Specific Fuel Consumption (SFC) means better thermal efficiency . It depends on compressor / turbine

efficiencies.

EQUIVALENT SPECIFIC FUEL CONSUMPTION (ESFC):

It is the rate of fuel flow in pounds per hour div ided by a turbo-prop’s ESHP.

Turbo-props cannot be compared on the basis of TSFC, EQUIVALENT SPECIFIC FUEL CONSUMPTION (ESFC)

is therefore used instead

FACTORS AFFECTING THE SPECIFIC FUEL CONSUMPTION:

· SFC & RPM:

SFC is high at reduced RPM, because the compressor / turbine efficiency is poor.

SFC improves with the increasing RPM and is lowest in the designed cruising speed RPM.

SFC & Forward speed of an Aircraft:

As the aircraft speed increases the Intake momentum drag also increases thus decreasing the thrust, but on

the other hand there is more MAF due to Ram Pressure, and necessities more fuel energy to compress the

mass, consequently SFC rises.

SFC & Altitude:

With an increase in the altitude the SFC improves or decreases, because the compressor and turbine

efficiencies are high at higher altitude.

At higher altitude there is less density and lesser Intake momentum drag. Thus an aircraft needing 80%

throttle setting to maintain a speed of 350 knots at 15,000 ft. may only require 65% of the throttle setting at

28000 ft. to keep the same speed.

When the conditions are colder at higher altitude, for the same Pressure Ratio, the compressor has to do a

lesser work on the MAF that has a little volume thus less fuel is required.

SFC & Pressure Ratio:

SFC decreases as the Pressure Ratio increases. With more Pressure at the outlet of the compressor means

more addition of the fuel, but a higher thrust is obtained as compared to the addition of the fuel. The pounds

of thrust obtained by the addition of the pounds of fuel is high.



SFC & Temperature:

For the same thrust to be obtained as on a standard day (15 deg. C), on a colder day , the compressor has to do

a lesser work on MAF for the required Pressure rise thus less fuel is required, SFC improves, but on a hot day

the compressor will need more MAF to compress and has to do more work for the required Pressure rise, thus

more fuel is required, SFC increases.

BY PASS ENGINE:

By pass engine is a dual flow sy stem engine in which the single incoming flow of air is div ided in two flows, one

flow passes through the core engine and the other is by passed through a by pass duct which is an annular

space between the core and the outer casing.

Advantages of a by pass engine:

· Higher propulsive and overall efficiency

· Low specific fuel consumption

· Lower noise level due to reduced velocity of the jet stream

· Lighter core engine. Less mass flow to handle

Dis-advantages of a by pass engine:

· Extra weight involved in the LP section that has to handle a greater mass airflow in order to develop the

same thrust.

Question: How does a Turbo-fan has a better propulsive efficiency than a Turbo-jet engine?

Answer: Turbo-fan has a better propulsive efficiency than a turbo-jet because it has a lighter core that handles

a lesser mass airflow which gives reduced jet stream velocity , while most of the thrust is developed by the fan

which handles a greater mass moving it rearward slowly .

BY PASS RATIO: The ratio of the cold stream to the hot stream. The ratio of the secondary air to the Primary

air by weight is called By pass Ratio.

FACTORS AFFECTING MASS OF AIRFLOW:

· Design of the compressor

· Compressor RPM or speed (more RPM more MAF)

· Density (more Density more MAF)

· Temperature (more Temperature less MAF)

· Altitude (more Altitude less Density less MAF)

· Forward speed of the aircraft (more Forward speed more Ram effect and more MAF)

FACTORS AFFECTING ACCELERATION OF AIRFLOW:

· Amount of fuel burnt in the combustion chamber. (more fuel burnt more RPM and hence more

acceleration imparted to the MAF by the fast moving compressor)

· Choking or the limitation of compressor to handle the MAF. No more acceleration can be imparted to the



MAF after the compressor begins to choke.

FACTORS AFFECTING THRUST:

· Forward speed of the aircraft:

Net thrust decreases with the forward speed of an aircraft due to intake momentum drag.

Net Thrust = Gross Thrust – Intake Momentum Drag

Net thrust is Maximum when aircraft is stationary with engines running, or it is said to be equal to Gross

Thrust. Gross Thrust does not take into account the Intake Momentum Drag.

Also at higher throttle settings the nozzle becomes choked and there is a vey little increase in the jet velocity

(Vj) in comparison with the forward aircraft speed (Va). The difference between the two velocities narrows

and the thrust output decreases, while on the other hand the propulsive efficiency increases.

The nozzle becomes choked because of the high EGT that increases the speed of sound and thus the exhaust

gas velocity reach sonic thus choking the nozzle.

· Jet Nozzle Velocity :

Thrust increases as the Jet Velocity (Vj) increases, however at high throttle settings the nozzle does becomes

choke due to the high EGT that increases the speed of sound and thus the exhaust gas velocity becoming sonic

thus choking the nozzle. After this an increase in the Jet velocity is only possible if the EGT is further

increased.

· Engine RPM:

Thrust increases with the increase in RPM. In the higher RPM range when the compressor and turbine

efficiencies are high, i.e. In the designed operating range, there is a large increase in thrust for a relatively

small RPM increase.

Majority of the thrust is obtained in the last 25% of the RPM change.

· Mass of Airflow:

Thrust increases with the increase in MAF

· Ram Effect:

The pressure of the air or gas cause by motion is called Ram pressure or Ram Effect.

As the aircraft speed increases the dy namic or Ram pressure of the air in the engine intake increases. With the

increases in air density the MAF through the engine will rise. The result will be an increase in GROSS THRUST

as the forward speed increases.

With the increase in the forward speed of an aircraft the Intake momentum Drag and Ram Effect both raise at

the same time and will tend to cancel each other. Ram also compensates the loss of thrust due to intake

momentum drag because of reduced pressure at high altitude.

Net thrust increases as the forward speed rises above 300 mph. Under subsonic conditions, Ram does not

affect the engine thrust as much as it affects the thrust in supersonic conditions.

· Altitude:

Thrust decreases with increasing altitude.



There are two things with the increase in altitude:

1 . the density decreases thus reducing the thrust.

2. The temperature drop thus increasing the MAF and thus increasing the thrust.

The overall compensating effect is that the thrust falls with an increase in altitude.

Though the reduction of thrust is compensated by the decrease in temperature till only 36090 ft. after which

the temperature remains constant while density continues to fall thus making the fall ion thrust more

pronounced.

If only engine is considered, this makes 36000 ft the optimum altitude for long range cruising at nominal

airspeeds.

§ Air Density and the effect of Temperature and Pressure.

Thrust increases as density increases. Density fall with the increases in altitude and increase in Temperature.

Density is the number of molecules per cubic feet or mass per unit volume.

Density affects thrust proportionally .

Thrust increases with the fall in temperature i.e. on cold day s and on higher altitudes, but decreases on a hot

day when temperature is high. Higher temperature means reduced air density , & Lower temperature means

higher density .

Thrust increases with an increase in Pressure.

Unless an engine has a variable inlet-area, the MAF into the engine at a given RPM is determined by the

density of air going into the compressor.

When the pressure (Ram) increases with an increase in the airspeed or decreased altitude, density increases.

Ambient Temperature:

1 . Reduced Ambient Temperature – Thrust Increases

With the reduced OAT the density of air rises thus increasing the weight of the air or the MAF. This will put the

compressor under load and it will run at reduced RPM but at constant thrust.

To maintain constant RPM, under this condition we need more fuel flow and thrust will increase. (Note that

the MAF is also high)

2. Increased Ambient Temperature – Thrust Decreases

With the increased ambient temperature the density of air decreases thus decreasing the weight of the air or

the MAF. This will put the compressor off-load and it will run at higher RPM and constant thrust.

To maintain (decrease) the RPM to constant, we need to decrease the fuel flow. This will cause the thrust to

drop. (Note that the MAF is also less).

RAM EFFECT: The pressure of the air or gas cause by motion is called Ram pressure or Ram Effect.

RAM RATIO: The pressure rise in the intake due to Ram Effect. It is the Ratio of the Compressor Inlet

pressure to the Ambient Pressure.

Ram Ratio = P1

P0



RAM RECOVERY :

The amount of Static Pressure recovered from the moving airstream or Ram by the Intake is

called Ram recovery .

TOTAL RAM RECOVERY OR TOTAL PRESSURE RECOVERY :

If all of the available Ram pressure is converted into Static Pressure, it is called Total Ram

Recovery .

RAM TEMPERATURE RISE:

The temperature rise due to Ram Compression Effect is called Ram Temperature Rise.

FULLY RATED ENGINE:

A Fully rated engine is one which will give maximum thrust at a specified OAT, after this

specified OAT the thrust will decrease. Lets say that it will give maximum thrust at 25 degree C. Fully Rated

Engines will give maximum Thrust at ISA condition, when the throttle is full. In fully rated the EGT does not

exceed its maximum limit at full throttle.

FLAT RATED ENGINE:

A flat rated engine gives maximum thrust upto a specified band of OAT by increasing the fuel

flow and after the range of the band, the thrust starts decreasing.

Its RPM cannot be further increased by a further increase in fuel flow because of the surge factor.

By adjusting fuel flow (decreasing it) in the flat rated engine, it could be derated from a higher thrust at a given

band of temperature to a lower thrust for the same band of temperature. This is done to enhance the engine

life. In flat rated engines the EGT may exceed than its prescribed limit at full or rapid throttle movement.

FREE TURBINE: It is a turbine which alone rotates the single staged Fan.

VARIABLE GEOMETERY DUCT:

A Variable Geometery Duct is used in very high speed supersonic aircrafts. In such ty pe of

duct the inside area or the configuration of the duct is changed by a mechanical dev ice as the speed of the

aircraft increases or decreases.

The geometry may be changed by a movable spike within the duct, or by incorporating some form of movable

restriction such as ramp or wedge inside the duct, or by the use of variable airflow by pass sy stem which

extracts part of inlet airflow from the duct ahead of the engine.

Dev ices of this ty pe are rigged to operate without the attention of the pilot. Variable geometry

method eliminates Buzz.

SHOCKWAVE: Shockwave is a thin region of discontinuity in a flow of air or gas, during which the speed,

pressure, density and temperature undergo a sudden change.

A shockwave is intentionally setup in the supersonic flow of air entering the duct by means of some

restriction of small obstruction. The shockwave results in the diffusion of the airflow and its velocity is

decreased.



BUZZ: Buzz is airflow instability and occurs when a shockwave is alternately swallowed and

regurgitated by the inlet. It occurs at high Mach numbers and can be avoided by changing the amount of inlet

area variation that takes place when variable geometry inlet sy stem is in operation.

A Buzz can cause v iolent fluctuations in pressure through the inlet which may result in

damage to the inlet structure or possibly to the engine.

CASCADE EFFECT:

In Cascade effect before the air can completely separate from the trailing edge of one blade is

affected by the leading edge of blade which follows. Cascade effect is the primary consideration in determining

the aerofoil section, angle of attack, and the spacing between blades to be used for the compressor blade

design for any given axial compressor.

COMPRESSOR MAP:

A compressor Map is a tool to v isualize compressor performance by the designer & the operator. Pressure

Ratio developed across the compressor is plotted against the corrected weight of airflow (MAF) through the

unit.

COMPRESSOR SURGE & BLADE STALL & CHOKING:

· Compressor Blade Stall:

Compressor Blades are tiny aerofoil just like the aerofoil of a wing.

An aircraft wing stalls when the aircraft flies below the stalling speed.

That is the Relative Airflow Speed is too (MAF is low) low. We need to increase the angle of attack to avoid

stalling upto 15 degrees with the help of flaps and slats.

Similarly , when the MAF in a compressor is too low the blade stalls. The angle of attack tends to increase

above 15 degree where the lift is completely destroy ed.

The word stall applies to the instability of airflow on a compressor blade or a stage.

· Compressor Surge (Axi-Sy mmetric Stall):

Axi-Sy mmetric stall or Compressor or pressure surge is a complete breakdown in compression within a

compressor resulting in a reversal of air flow.

Surge results from a condition of instable airflow within a compressor. This condition occurs when there is

less MAF within the compressor while the RPM are very high. The air piled up in the rear stages of the

compressor tends to have a reverse flow following the low MAF in the front stages of the engine. The situation

is such that flame in the combustion chamber also finds an area of low pressure in the front stages of the

compressor and tends to move towards that area, resulting in a fire situation in the compressor. It’s Oxy gen

in the air within the compressor that burns.

· Choking: When the compressor is not operating at its optimum rpm while the MAF within it is very high.

The forward compressor blades are not be able to bite off enough air to be able to compress it sufficiently and

to force it on through the rear stages of the compressor.

Commonly Asked Questions:



Q. WHAT DO WE DO IN THE COCKPIT BEFORE AN ENGINE REMOVAL?

We pull out the squib CB and pull the fire handle. The fire handle is pulled so that no fuel or hy draulic or

electrical supply be available to the engine, and Squib CB is pulled so that fire bottle be not discharged on

pulling the fire handle.

Q. WHAT ARE THE GENERAL PRECAUTIONS FOR AN ENGINE REMOVAL?

1. BEFORE ATTEMPTING MAINTENANCE OPERATIONS ON THE FUEL SY STEM MAKE CERTAIN THAT FIRE

EXTINGUISHING EQUIPMENT IS READILY AVAILABLE IN PROXIMITY TO WORK AREA.

2. CHECK THAT LANDING GEAR GROUND SAFETIES INCLUDING WHEEL CHOCKS ARE IN POSITION.

3. IN ORDER TO AVOID DAMAGE TO LINES, PNEUMATIC DUCTS AND ELECTRICAL CONNECTORS AND TO

PREVENT COMTAMINATION BY FOREIGN BODIES, BLANK OFF THE LINES, DUCTS AND CONNECTORS WITH

PROTECTIVE CAPS.

4. B_E_F_O_R_E_ _P_R_O_C_E_E_D_I_N_G_ _W_I_T_H_ _M_A_I_N_T_E_N_A_N_C_E_ _W_O_R_K_

_O_N_ _O_R_ _N_E_A_R_ MECHANICAL FLIGHT CONTROLS OR PRIMARY FLIGHT CONTROL SURFACES,

LANDING GEARS, ASSOCIATED DOORS OR ANY MOVING COMPONENT, MAKE CERTAIN THAT GROUND

SAFETIES AND/OR WARNING NOTICES ARE IN CORRECT POSITION TO PREVENT INADVERTENT

OPERATION OF CONTROLS.

5. B_E_F_O_R_E_ _P_O_W_E_R_ _I_S_ _S_U_P_P_L_I_E_D_ _T_O_ _T_H_E_ _A_I_R_C_R_A_F_T_

MAKE CERTAIN THAT ELECTRICAL CIRCUITS UPON WHICH WORK IS IN PROGRESS ARE ISOLATED.

6. B_E_F_O_R_E_ _P_R_E_S_S_U_R_I_Z_I_N_G_ _H_Y _D_R_A_U_L_I_C_ _S_Y _S_T_E_M_S_, MAKE

CERTAIN THAT HY DRAULIC SY STEM UNDER MAINTENANCE HAS BEEN ISOLATED.

7 . MAKE SURE THAT PY LON AFT HOIST FITTINGS ARE IN GOOD CONDITION BEFORE Y OU INSTALL AND

AFTER Y OU REMOVE THE BOOTSTRAP REAR MAIN BEAM.

8. OBSERVE SAFETY PRECAUTIONS WHEN WORKING ON THE HY DRAULIC SY STEM. LONG EXPOSURE TO

HY DRAULIC FLUID CAN CAUSE SKIN DEHY DRATION AND CHAPPING. REF. 29-00-00.

9. CHECK AIRCRAFT STABILITY . 05-57 -00

Q1. WHAT ARE THE TWO POSITIONS OF A THRUST REVERSER?

Stow and Deploy ed

Q2. IF A THRUST REVERSER IS NOT PROPERLY RIGGED. WHAT WILL HAPPEN?



A. The FADAC will be sensing that the Thrust Reverser is in deploy ed position and will not allow an power

output by the engine when throttle is moved forward.

Q3. WHAT IS THE DIFFERENCE BETWEEN DRY MOTORING AND WET MOTORING?

In Dry motoring an engine is cranked v ia the bleed air taken from the APU to the engine. And in wet motoring

HP fuel valve is opened momentarily during cranking just to pressurize the fuel lines for the purpose of leak

test.

Q4. WHAT IS MIC?

Major Item change sheet.

Q5. WHAT DOES A NACELLE COMPRISES OF?

AN engine nacelle comprises of air-inlet, fan cowl, reversal cowl. core cowl.

Q6. WHAT PRECAUTIONS BE TAKEN BEFORE THE REMOVAL OF NOSE COWL, FAN COWL, FAN-REVERSER

COWL AND EXHAUST NOZZLE?

Q7 . WHICH LIGHTS ILLUMINATE IN STOW AND DEPLOY ED POSITION OF THRUST REVERSERS?

Deploy Position – Green Light

Stow Position – No light.

Q8. PRECAUTIONS WHEN BRINGING AN AIRCRAFT IN HANGAR?

A good care must be take during towing an aircraft to hanger ..... 2 mechanics on each wing ... 1 to the tail.....1

in cockpit ...........

the steering sy stem to be unlocked and breaks should be working properly .

nose steering by -pass pin... landing gear grnd lock pin... pressurize hy d B for brakes... anti-collision light

Q9. WHAT ARE WARNINGS, CAUTIONS AND NOTES?

W_A_R_N_I_N_G_ : CALLS ATTENTION TO USE OF MATERIAL, PROCESSES, METHODS, PROCEDURES OR

LIMITS WHICH MUST BE FOLLOWED PRECISELY TO AVOID INJURY OR DEATH TO PERSONS.

- C_A_U_T_I_O_N_ : CALLS ATTENTION TO METHODS AND PROCEDURES WHICH MUST BE FOLLOWED TO

AVOID DAMAGE TO EQUIPMENT.

- N_O_T_E_ : Calls attention to methods which make the job easier or prov ide supplementary or explanatory

information

Q10. WHAT ARE SCHEDULED AND UN-SCHEDULED MAINTENANCE CHECKS

S_c_h_e_d_u_l_e_d_ _M_a_i_n_t_e_n_a_n_c_e_ _C_h_e_c_k_s_ (05-20-00)

The initial Scheduled Maintenance Checks are those prescribed by the Maintenance Review Board Report

(MRBR).



U_n_s_c_h_e_d_u_l_e_d_ _M_a_i_n_t_e_n_a_n_c_e_ _C_h_e_c_k_s_ (05-50-00)

The Unscheduled Maintenance Checks section covers Maintenance Checks to be performed whenever a flight

in abnormal conditions has been reported by the flight crew. This section has been div ided into two

categories of information :

- Inspections

- Checks

Q11. WHICH CHAPTER OF THE AMM TELLS US ABOUT THE TIME LIMITS AND MAINTENANCE CHECKS?

Chapter 00

Q12. LIST THE ATA CHAPTERS?

AIRCRAFT GENERAL CHAPTER

Time Limits/Maintenance Checks .......................... 5

Dimensions & Areas ...................................... 6

Lifting and Shoring ..................................... 7

Leveling & Weighing ..................................... 8

Towing & Taxiing ........................................ 9

Parking & Mooring ....................................... 10

Placards & Markings ..................................... 11

Serv icing ............................................... 12

AIRFRAME SY STEMS

Standard Practices - Airframe ........................... 20

Air Conditioning ........................................ 21

Auto Flight ............................................. 22

Communications .......................................... 23

Electrical Power ........................................ 24

Equipment/Furnishings ................................... 25

Fire Protection ......................................... 26

Flight Controls ......................................... 27

Fuel .................................................... 28

Hy draulic Power ......................................... 29

Ice & Rain Protection ................................... 30

Indicating/Recording Sy stems ............................ 31

Landing Gear ............................................ 32

Lights .................................................. 33

Navigation .............................................. 34

Oxy gen .................................................. 35

Pneumatic ............................................... 36

Water/Waste ............................................. 38

Airborne Auxiliary Power ................................ 49

STRUCTURE

Structures .............................................. 51



Doors ................................................... 52

Fuselage ................................................ 53

Nacelles/Py lons ......................................... 54

Stabilizers ............................................. 55

Windows ................................................ 56

Wings ................................................... 57

POWER PLANT

Standard Practices - Engines ............................ 7 0

Power Plant ............................................. 7 1

Engine .................................................. 7 2

Engine Fuel and Control ................................. 7 3

Ignition ................................................ 7 4

Air ..................................................... 7 5

Engine Controls ......................................... 7 6

Engine Indicating ....................................... 7 7

Exhaust ................................................. 7 8

Oil ..................................................... 7 9

Starting ................................................ 80

Q13. WHAT IS A CHAPTER BREAKDOWN POLICY ?

Each Chapter/Sy stem is broken down into sections/subsy stems (combinations of functional/phy sical

groups).

Example :

- 29-00-00 - Hy draulic Power - General

- 29-10-00 - Main

- 29-20-00 – Auxiliary

29-00-00 CHAPTER (hy draulic)

29-10-00 SECTION / SUBSY STEM (combinations of functional/phy sical groups).

29-11-00 SUB-SUBSY STEM (main)

29-11-11 SUBJECT (unit or component)

Each Section/subsy stem is broken down into sub-subsy stems (Installations/Circuits). Example :

- 29-10-00 - Main

- 29-11-00 - Green Main Hy draulic Power

- 29-12-00 - Blue Main Hy draulic Power

- 29-13-00 - Y ellow Main Hy draulic Power

Each sub-subsy stem is div ided into subjects. Each subject represents a unit or component. Example :



- 29-11-00 - Green Main Hy draulic Power

- 29-11-11 - Green Assembly Reservoir

- 29-11-12 - Hy draulic Reservoir

- 29-11-13 - Green Hy draulic Pump

N_O_T_E_ : The subjects 01 to 08 are used in the Illustrated Parts Catalog (IPC) only in order to split the sub-

subsy stems of the aircraft into zones.

Q14. WHAT IS DTMSRAICAD?

(D) Description and Operation – Page 001-099

(T) Trouble shooting (Refer to TSM) – Page 101-199

(M) Maintenance Practices – Page 201-299

(S) Serv icing – Page 301-399

(R) Removal and Installation – Page 401-499

(A) Adjustment Tests - Page 501-599

(I) Inspection Checks – Page 601-699

(C) Cleaning and Painting – Page 7 01-7 99

(A) Approved Repairs – Page 801-899

(D) Deactivation and Reactivation - Page 901-999

N_O_T_E_ : When the quantity of pages for any one sub-heading will exceed 99 the next pages will be

numbered :

- 99, A00, A1, A2, A3 etc...

- 599, A500, A501, A502, A503 etc...

Q15. Functional Item Numbers (FIN)

Equipment on the aircraft is generally allocated a unique identifier known as a Functional Item Number (FIN).

(2)Mechanical FIN

Mechanical equipment is identified by 6 numerals, the first two are the

ATA Chapter/Sy stem prefix and the last four the equipment number.

A ty pical mechanical FIN is 27 1198, where :

27 : ATA Chapter/Sy stem (Flight Controls in this example)

1198 : equipment number

N_O_T_E_ : The third numeral may identify a specific sy stem to which an equipment belongs.

e.g. 291XXX = Hy draulic Sy stem - Green

292XXX = Hy draulic Sy stem - Blue



293XXX = Hy draulic Sy stem - Y ellow

Q16. TY PES OF ADJUSTMENT TESTS?

e)Adjustment/Test (A/T) (Pages 501 to 599)

Test information is div ided into three categories - operational test,

functional test, sy stem test.

Below are definitions of the three categories :

1_ Operational test

This test is required to ascertain that an item (sy stem, subsy stem component) is fulfilling its intended

purpose. It does not require quantitative tolerances and it can include readings using aircraft instruments.

This test requires no special equipment or facilities other than that installed on the aircraft and is comparable

to the tests performed by the flight crews. It is not intended that the operational test of the unit shall meet the

specifications and tolerances ordinarily established for overhaul, or major maintenance periods. A test can

be carried out where appropriate, with ground hy draulic, electrical and/or air conditioning connections

made to the aircraft.

2_ Functional test

This test is required to ascertain quantitatively that a sy stem or unit is functioning in all aspects in

accordance with minimum acceptable sy stem or unit design specifications. This test may require

supplemental ground support equipment and be more specific and detailed than an operational test. It

contains all necessary information to perform proficiency tests to maintain sy stem or unit reliability at an

acceptable level without reference to additional documents.

3_ Sy stem test

This test contains all adjustment specifications and tolerances required to maintain sy stem and/or unit

performance at maximum efficiency and design specifications. It is self-contained and may duplicate other

tests.

Q17 . WHAT EFFECT OF OAT ON ENGINE THRUST?

1. Reduced Ambient Temperature – Thrust Increases

With the reduced OAT the density of air rises thus increasing the weight of the air or the MAF. This will put the

compressor under load and it will run at reduced RPM but at constant thrust.

To maintain constant RPM, under this condition we need more fuel flow and thrust will increase. (Note that

the MAF is also high)

2. Increased Ambient Temperature – Thrust Decreases

With the increased ambient temperature the density of air decreases thus decreasing the weight of the air or

the MAF. This will put the compressor off-load and it will run at higher RPM and constant thrust.

To maintain (decrease) the RPM to constant, we need to decrease the fuel flow. This will cause the thrust to

drop. (Note that the MAF is also less).



Q18. WHAT IS A HEAT ENGINE? WHAT ARE ITS TY PES?

A heat engine is a dev ice which converts thermal energy into mechanical output. Gas Turbine Engines are

simple heat engines that convert heat energy of fuel into mechanical work.

Q19. WHAT ARE ANTI-STALL DEVICES?

VBV, VSV, Twin Spool, IGV’s, Bleed valves

Q20. HOW DOES VBV’s AND VSV’s WORK? WHAT IS THE FEEDBACK OF THEIR OPERATION?

VBV’s and VSV’s work automatically and in relation with each other. At high power setting when there is a

need of more airflow the VBV’s are closed so as to prov ide as much of the airflow to the rear compressor

stages as it can while the VSV’ are at their optimum angle (open) to facilitate the airflow to the later stages.

But at low power settings VBV’s are open to bleed off the excessive airflow to avoid surging and VSV’s are

closed (means at the zero degrees of their angle).

Q21. WHAT IS A RAM JET, PULSE JET AND ROCKET MOTOR? HOW DO THEY WORK?

Ram Jet, Pulse Jet and Rocket motors are not gas turbine engines but they work on the same principle that is

the reaction propulsion. They could be called members of reaction family engines.

Ram Jet: Ram jet is the simplest jet engine and does not have any moving parts. It is only a large open-ended

piece of pipe with a fuel injection and fuel metering sy stem. Ram jet relies upon the ram effect to build up the

pressure of the air entering the engine to the amount that will enable the engine to operate. Hence a Ram jet

must be carried aloft and accelerated to operating speed by some means other than its own thrust. It may ride

piggy -back on a rocket to operational altitude or it may be borne to the proper height and speed as a dropable

external store on a conventional airplane, which might be the case for an air-to-air and air-to-ground ram-jet

missile.

It is a breathtaking engine.

Pulse Jet: A pulsejet is a ramjet with an air inlet which is prov ided with a set of shutters that is spring loaded

to remain in the closed position. After a pulse jet is launched, ram air pressure forces the shutters to open,

fuel is injected into the combustion chamber, and is burned. Ignition is intermittent and goes on and off as the

shutters open and close. The gases produced by combustion are forced out of the jet nozzle by the pressure

that has build up within the combustion chamber. The acceleration of the gases through the nozzle generates

thrust.

When the pressure in the combustion chamber is less than the ram pressure the shutters open admitting more

air and the cy cle repeats itself.

Pulse jets may be started and operated at a considerably lower speeds than Ramjets, and it is possible to

design a Pulse jet that would hardly require any initial velocity . Pulse Jet was used as Buzz Bombs by the

Germans in the second world war.

It is a breathtaking engine.

Rocket Motor: A rocket motor or a rocket operates on jet propulsion principle and carries its own fuel and an

oxidizer to burn with the fuel within itself or aboard the vehicle that the rocket propels. A rocket motor is not



a breathtaking engine and can operate in complete independence in outer space.The fuel and the oxidizing

agent together, constitute the propellant. Solid fuel or propellant, motors carry the propellants stored in their

combustion chamber, while in case of liquid propellant, it may be stored in tanks that is piped to the

combustion chamber.

Q22. FUNCTIONS OF NOSE COWL.

First, it must be able to recover as much of the total pressure of the free airstream as possible and deliver this

pressure to the front of the compressor with minimum loss.

Secondly , it must deliver air to the compressor inlet under all flight conditions with as little turbulence and

pressure variation as possible.

Also, it must hold minimum drag, which it itself creates.

Q23. WHAT IS THE PURPOSE OF A COMPRESSOR? HOW DOES IT WORKS?

Purpose of compressor is the compression of air. Because mixing of fuel with uncompressed air will not create

enough expansion of the gases to do any useful work for the engine operation.

A compressor stage consists of a set of rotating blades called rotor followed by a set of stationary blades

called stator. What the rotors do, they speed up the air going through the engine, while the stators they

actually slow down the air. What happens is the transfer of velocity energy into pressure energy .

Q24. TY PES OF COMBUSTION CHAMBERS?

Can Ty pe combustion chamber (Small Turbo-props)

Annular Ty pe – (Large Turbo-fan engines)

Can Annular

Q25. STATE THE ADVANTAGES OF CAN, ANNULAR AND CAN-ANNULAR TY PE COMBUSTION CHAMBERS?

Can Ty pe:

1 . Structural strength (Due to smaller size and lesser diameter)

2. Light weight structure

3. Indiv idual units can be removed from the engine for inspection.

4. Use on centrifugal compressor ty pe engines.

Disadvantages - Due to their shorter dia, they are made larger in length. – Improper gas distribution on the

face of the turbine.

Annular:

1 . It uses limited space without any increase in length or dia.

2. Better mixing of fuel and air within a relatively simple structure.

3. Proper distribution of hot gases at the face of the turbine.

4. Use in high by pass turbo-fan engines

Disadvantages – Fuel spray patterns with the combustors are difficult to achieve. Degradation within the

combustor liners require a major engine disassembly to rectify .

Can-Annular:

1 . It is more efficient in respect of power output.



2. Also the length of cans is reduced.

3. Easy removal of cans from the engine without major disassembly for inspection or repair.

4. Use on large turbo-jet & turbo-fan engines.

Q26. WHAT DO WE DO IN THE COCKPIT BEFORE AN ENGINE REMOVAL?

We pull out the squib CB and pull the fire handle. The fire handle is pulled so that no fuel or hy draulic or

electrical supply be available to the engine, and Squib CB is pulled so that fire bottle be not discharged on

pulling the fire handle.

Q27 . WHY AN AIRCRAFT IS INTO THE WIND FOR RUNUP? ALSO ITS EFFECTS ON ENGINE PARAMETERS?

An aircraft is faced to the wind direction for run-up because:

1 . maximum amount of mass of airflow is available through the Ram pressure for the engine.

EPR - will increase

N1 & N2 RPM - N1 and N2 Rpm will be within the operator’s designed limits for normal operation and

the difference between the speed of two compressors will not be greater

EGT - will be within the operator’s designed limits for normal operation

2. also if an engine is tested in tail wind there is probably a chance of exhaust gas ingestion through the

intake again and will lead the engine to surge.

EPR - will decrease

N1 & N2 RPM - N1 and N2 will be offloaded due to warmer air ingestion that has a lesser density and

lesser MAF, but the difference between their speed will be much greater.

EGT - will experience an abnormal rise.

3. Reverse wind-milling may also happen if engine is tested in the tail wind.

Q28. SAFETY PRECAUTIONS OF ENGINE RUN-UP?

Safety precautions

• Anti-collision beacons must be switched on throughout the engine ground run

• Aircraft maintenance organisations must ensure that all personnel, equipment and cargo is well clear of the

rear of the aircraft during an engine ground run

• A superv isor must be appointed over the engine ground run to ensure the safety of the operation and all

airside users in the v icinity . The engine ground run must be stopped immediately if a dangerous situation

arises

• To improve v isibility for airside drivers, all ground serv ice equipment must be moved well away from the

aircraft during the operation

• Before commencement of aircraft ground run activ ity at Site 1 (Terminal and Freight Apron areas), warning

signs must be placed on the edge of the Apron Serv ice Road directly behind each aircraft wing tip to warn

other apron users that aircraft ground run activ ity is in progress.



The signs should state, ‘Caution: Engine Ground Run in Progress’.

Engine ground run signs must be removed immediately following the end of the aircraft ground run activ ity to

signal to apron users that it is safe to pass behind the aircraft.

Q29. WHAT ARE THE REQUIREMENTS OF A MAINTENANCE ORGANIZATION COMMENCING A GROUND

RUN?

Requirements of Maintenance Organisations

• To ensure that appropriate maintenance personnel are aware of the ground running sites, and of the

conditions relating to their use, the maintenance organisation must take such steps as necessary to publish

details of the sites and procedures in whatever form of internal documentation is most appropriate.

A copy of all documentation must be supplied to the Airside Standards Superv isor.

• Maintenance organisations must ensure the person towing an aircraft to a ground running location is a

holder of a current Airside Driver Authority Level 3 and the vehicle has a current Authority for Airside Use

(Airside Vehicle Permit).

Q30. WHAT IS THE DIFFERENCE BETWEEN DRY MOTORING AND WET MOTORING?

In dry motoring we run the HPC v ia bleed through the APU to the starter. In wet motoring we do the same but

with HP fuel valve open for not more than 30 seconds to pressurize the fuel lines and thus do a leak check.

Q31. WHY DO WE DO A DRY MOTORING?

To clear off any accumulated fuel to clear off an engine after failed attempt to normal start.

Q32. WHAT IS MAXIMUM MOTORING SPEED?

The maximum motoring speed is defined as the rate of increase in N2 rpm is less than 1% in approximately 5

seconds.

Q33. AT WHAT N2 SPEED DOES THE STARTER CUTS OUT?

45-47 % rpm.

Q34. IN CASE OF FIRE INDICATION (INTERNAL ENGINE FIRE OR TAIL PIPE FIRE) WHEN DO WE OPERATE

FIRE EXTINGUISHER?

DRY MOTOR THE ENGINE TO EXTINGUISH AN INTERNAL ENGINE FIRE OR TAILPIPE FIRE. USE A FIRE

EXTINGUISHER ON THESE FIRES ONLY IF THE DRY MOTOR CANNOT CONTROL OR EXTINGUISH THE FIRE.

THE ENGINE WILL BE DAMAGED IF A FIRE EXTINGUSHER IS USED, AND Y OU MUST REMOVE THE ENGINE

Q35. WHY DO WE GIVE A TIME OF 5 MINUTES AT IDLE BEFORE ENGINE SHUT DOWN?

Because turbine case and turbine rotor do not cool at the same rate after shut down. The turbine case that

cools faster may shrink down on the on the rotating turbine blades, if the engine is too hot. In extreme cases

the blades squeal and sieze.

Q36. CAN ENGINE OPERATION WITH OPEN COWLS BE DONE TO OPERATE THRUST REVERSERS?

No



Q37 . WHAT DETERMINES EPR OR N1 BEFORE A FLIGHT FOR TAKE-OFF, CLIMB & CRUISE AND DESCENT?

WHAT FACTORS ARE TAKEN INTO CONSIDERATION?

The required EPR is determined by the flight operations just before the flight consulting a Flight Manual or

Operation Manual. The factors are considered are as follows:

· Aircraft Ty pe

· Engine Ty pes

· Outside Air Temperature

· Wind Direction

· Runway selected

· Humidity

· Altitude

· Pay Load (Cargo, Passenger and Fuel)

Q.38. IN CASE OF A TURBO PROP, IN WHICH RANGE IS THE POWER CONTROL LEVER CONTROLLED

MANUALLY ?

· In Beta range, which is used for ground handling and in-flight approach. At all other times a constant

propeller speed is maintained automatically by the PCU for any given Propeller control lever setting.

Q39. WHAT WILL Y OU DO AFTER ENGINE FIRE BOTTLE DISCHARGE?

· Washing with engine being dry motored and water with detergent Zok-27 spray ed at the inlet.

Q40. FROM INTAKE TO EXHAUST…WHAT HAPPENS WITH THE AIR?

· Air Intake:

Well, speaking in subsonic terms, when air enters the intake it is diffused due to the divergent shape of the

intake where its velocity is decreased along with an increase in the static pressure.

Compressor:

After it enters the compressor a continuous steady rise in the pressure is witnessed but as compared to the

compressor inlet and outlet there is a slight decrease in pressure due to frictional losses. Then there is a

steady decrease in the velocity through the compressor, though the axial velocity is maintained constant.

Diffuser: The air then enters the diffuser. It has a divergent shape and due to this shape the static pressure

rises while the velocity is further decreased so that it could sustain the flame in the combustion chamber.

Combustion Chamber: Combustion occurs at constant Pressure. Though practically a slight decrease in

pressure has been observed due to air friction and turbulence. The velocity keeps on decreasing here. The

temperature is at its highest in the Primary section of combustion chamber.

The outlet of a combustion chamber is convergent in shape and this is to prov ide expansion as the air leaves

the combustion chamber following with an increase in velocity .

NGVs: There is a sudden expansion of gasses as they pass through the nozzle guide vanes where the velocity is

at its highest.

Turbine: After the NGV as the air passes on the turbine a large drop in pressure occurs as the pressure energy

is converted into mechanical work. Similarly Velocity drops as the Kinetic energy is again converted into

mechanical work, and also the Temperature drop occurs as heat energy is again converted into mechanical



work.

Exhaust: After the turbine the gas passes through the exhaust section where the Pressure in the exhaust duct

drops slightly due to frictional losses and a further drop in pressure occurs in the propelling nozzle where the

pressure energy is converted into Kinetic energy . Here the velocity highly increases and the temperature

drops.

After the air leaves the

Q41 INSPECTION SEQUENCE?

· To permit simultaneous inspection of several areas of the aircraft the inspection has been div ided into a

number of _Packages_.

· The inspections are div ided into three phases :

· - Phase 1 : is a general inspection for primary damage and indications of

· remote damage and is mainly external.

· - Phase 2 : is a more detailed inspection and is mainly internal. Some component

· removal may be called up.

· - Phase 3 : is a very detailed inspection involv ing component removal and

· strip down.

Q42. WHAT IS MAXIMUM POWER ASSURANCE TEST? STATE ITS PURPOSE? WHEN DOES A POWER

ASSURANCE TEST BECOMES MANDATORY ?

AMM 7 1-00-00

(3) Power assurance check.

Power assurance check is a functional test

· It determines that the engine can go to takeoff power while the EGT and engine RPM stay in operation

limits.

· This test is not performed to accept or reject an engine

· This check becomes necessary after engine maintenance that could change engine operation, like after

engine installation, modular installation etc.

· This check compares engine performance to other power assurance runs. The difference in power

assurance run data tells y ou if there are large changes in engine operation margin and if the margin where the

engine operates is permitted.

(a)The function of the power assurance check is to make sure that the engine can go to takeoff power while the

EGT and N2 speed stay in operation limits. Do this check after engine maintenance occurs that could change

engine operation. This check compares engine performance to other power assurance runs. The difference in

power assurance run data tells y ou if there are large changes in engine operation margin and if the margin



where the engine operates is permitted. The check can also examine flight crew concerns.

(b)Because a power assurance run is usually not sufficiently stable, other quality check procedures can give a

more accurate estimate of margin. These other quality checks include a test stand run as given in the Engine

Manual, and/or rev iew of flight data received during takeoff and analy sis done with algorithms from the OEM.

The Power Assurance Check is not a good test for the performance analy sis of the engine. Do not use only the

Power Assurance Check to accept or reject an engine. The Power Assurance run is usually not sufficiently

stable to accurately calculate the engine’s health.

Y ou can get a more reliable performance analy sis by doing a test cell operation or on-wing performance trend

monitoring.

Q43. CAN RECOMMENDED GRADE OF FUEL BE MIXED?

Y es

Q44. CAN ALL OF THE FUEL BE TRANSFERRED FROM ONE FUEL TANK TO ANOTHER DURING FLIGHT?

No

Q45. CAN OIL OF DIFFERENT GRADES BE MIXED?

No

Q46. WHAT IS ENGINE TRIMMING? AND WHY IS IT DONE?

The fuel control adjustment is called engine trimming. It is done because at the time of manufacture there are

manufacturing tolerances due to which two engines may produce different level of thrust at the same RPM

setting. So by adjusting the fuel control the Thrust is maintained the same with a slight change in the RPM.

Q47 . WHAT IS ENGINE TRIM SPEED? IS TRIM SPEED AND DATA PLATE SPEED IS SAME?

The adjusted compressor RPM , corrected to standard day conditions at seal level is known as the engine trim

speed. This is done by an adjustment on the fuel control that governs the N2 speed.

Y es, both are same. Data plate speed is determined at the time of the manufacture when the engines are

adjusted to produce their exact rated thrust on calibrated engine test stand. Data plate speed is then stamped

on engine data-plate in terms of both actual RPM and percent RPM.

Q48. WHAT IS ENGRAVED ON ENGINE DATA PLATE? AND WHERE IS IT INSTALLED ON AN ENGINE?

1. Engine Trim Speed

2. Engine Gross weight

3. Engine Serial Number

4. Engine Rated Thrust

Q49. WHAT IS SHUNT?

Shunt is installed to give a false EGT signal



Q50. WHAT IS FLAT RATE CORNER POINT?

Flat rate corner point in flat rated engines is the OAT limit after which the Thrust will tend to fall, we cannot

increase the Thrust or the EGT will go bey ond its limit. EGT though becomes constant after this point.

Q51. WHAT ARE THE POSSIBLE CAUSES & EFFECTS OF A HUNG AND A HOT START?

Hung Start:

1 . Inadequate bleed pressure to the starter.

2. A faulty starter

3. Ceased Main engine bearing.

4. Inadequate fuel flow.

5. Abnormal signals to FCU of CIT (high CIT), BP (high burner Pressure signal), Ambient Pressure (Low

ambient pressure).

Effects: Deterioration of the Starter

Hot Start:

1 . Accumulated fuel in the combustion chamber.

2. Faulty fuel nozzles.

Effects: Deterioration of the NGV’s and the Turbine area.

Q52. WHAT IS TAKE OFF THRUST?

This is the maximum thrust that can be used without over boasting the engine. This rating is normally

continued to only 5 minutes time period and is to be used for take-off only .

Q53. WHAT IS MAXIMUM CONTINEOUS?

This is the maximum thrust that may be used continuously and is primarily intended for emergency use at the

discretion of the captain.

Q54. WHAT IS IDLE?

It is not a thrust rating, but a thrust lever position obtained by fully retarding the thrust lever. Minimum

thrust suitable for ground operation is called ground idle and that in air is called flight idle.

Q55. WHAT ARE THE COMPRESSOR SURGE PARAMETERS?

EPR, EGT & RPM

Q56. WHAT IS FOG?

Visibility of less than 3280 ft due to moisture.

Q57 . IS ENGINE OPERATION WITH HINGED COWL IS PERMISSIBLE?

Y es it is permissible but its is normally done with closed cowls.

Q58. IN WHICH ENGINE OPERATION MODE, THE ENGINE EXPERIENCES THE MAXIMUM MATERIAL AND

THERMAL STRESSES?



During Thrust reverser mode, because it is during when the gas flow moment is changed against it course

Q59. WHERE IS AN ENGINE DATA-PLATE LOCATED? WHAT ARE THE PARTICULARS OF ENGINE DATA-

PLATE?

Data-Plate is located on the left side of the fan frame. Fan frame denotes the actual engine

TY PE CERTIFICATE FRENCH CERTIFICATE

Engine M/1M13

MODEL # SERIAL #

CF680-C2A8 695-408

RATING

T/O THRUST MAX. CONT. THRUST

57 860 48080

Q60. WHAT SENSE GOES TO MEC THAT ENABLES TO OPEN AND CLOSE VBV AND VSV?

During high thrust operation, the burner pressure will be sensed low by the MEC and it will signal the VBV to

close and VSV to open, but in low thrust operation mode, the burner pressure will be sensed high by the MEC

and it will signal VBV to open and VSV towards close.

Q61. MEC SIGNALS VSV OR VBV TO CLOSE OR OPEN?

MEC signals VSV to close or open, which is linked with the VBV. VBV itself doesn’t receive signal directly from

the MEC

Q62. WHAT IS NORMALLY THE POSITION OF VBV ON GROUND OR WHEN THE ENGINE IS SHUTTED OFF?

Its position is towards open, because on ground there is a low thrust operation mode, so the air is being bled

off v ia VBV…and when the engine is stopped the position of VBV remain the same that is in open.

Q63. WHERE IS FUEL USED IN ENGINE?

1. for ignition in the fuel nozzles

2. For cooling in the fuel oil heat exchanger

3. For the operation of MEC

4. For the hy draulic actuation of VSV

Q64. WHAT ARE THE UNITS OF VBV ON TEST BENCH AND VSVs?



VBV – volt DC

VSV – in degrees and volts

Q65. TREND MONITERING (ETMS – Engine Trend Monitering Software) SOFTWARE IN TSE-LM

SAGE – Sy stem Analy sis for Gas Turbine Engine

Q66. THROUGH WHICH PORTS DO Y OU DO THE BSI OF 1ST STAGE NGV?

Through ports in Combustion Chamber.

Q67 . How one can reduce / optimize Engine Maintenance Cost per Flight Hour?

There are four basic parameters to calculate severity factor, in order to calculate true Engine Maintenance

Cost:

1 . Annual Utilization-EFH, EFC

2. Average OAT

3. EFH:EFC Ratio

4. %age Derate

Q68. VBV IS AN ANTI-STALL DEVICE, BUT WHEN IT DUMPS THE MAF…IT DECREASES WITH AN INCREASE

IN ANGLE OF ATTACK…THIS SHALL TAKE THE ENGINE TO STALL, THEN WHY IS IT CALLED AN ANTI

STALL DEVICE?

Actually when it dumps the almost air or mass of airflow, more air rushes into the engine compressor thus

increasing the velocity of air…now with an increase in velocity the angle of attack decreases taking away the

engine compressor from stall.

Q69. What is important for the weight calculation of Jet A-1 fuel?

A. When weight is to be measured than the specific grav ity of the fuel on that particular day considering the

pressure and temperature must be known.

Q7 0. Why is a turbo-prop inefficient at height as above as 30000 to 35000 ft??

The higher y ou go, the faster y ou must go to maintain the same lift because of air thinning.

Now if y ou want to go faster, y ou need to push around air with more thrust.

But y ou can't just turn the prop faster, as a prop tip speed at the speed of sound induces wave drag which

dramatically reduces thrust. ... Y ou'll need to add more blades to the prop. The more blades y ou add, the

more y our prop will look like a fan. This is where y ou find a prop fan design.

The higher/faster y ou want to go, the more blades y ou add. At some point, y ou might as well cowl the blades

of y our 'prop' to increase the air speed, reduce noise and increase the compression of the blades.

Now y ou have a turbo fan.

Y ou will need to add more blades to the prop. The more blades y ou add, the more y our prop will look like a

fan. This is where y ou find a prop fan design.

The high / faster y ou want to go, the more blades y ou add, at some stage , y ou might as well coel the blades of

y our prop to increase the speed, reduce noise and increase the compression of the blades. Now y ou have a



turbo-fan.

Q7 1. IN GROTOR TY PE OF PUMPS, WHICH GEAR HAS MORE TEETH?

Internal Gear

Q7 2. WHAT IS THE DIFFERENCE BETWEEN PACKING AND SEALS?

Seals are used in stationary parts and packings are used in rotary parts.

Q7 3. GEAE – CWC stands for:

Customer Web Center

Ty pes of GEAE SBs?

1. Spare parts

2. Standard

3. Alert

4. Other

5. N/A

Q.7 4 WHAT ARE THE CATEGORIES OF SBs?

0-9 Categories

Q7 5. TY PES OF BEARINGS

Ball bearing: takes thrust and radial loads. It has lesser friction due to point contact

Rollar bearing: takes radial load only . It has relatively more friction due to line contact. Tapered bearing are

roller bearings.

Q7 6. CLASSIFICATION OF BEARINGS?

One dot

Two dot

Three dot

Q7 7 . PRIMARY MAINTENANCE

1 . Hard time maintenance (Preventative)

2. On-condition (Preventative)

3. Condition monitoring (Trend)

Q7 8. WHAT IS HARD TIME MAINTENANCE?

A.



PRIMARY MAINTENANCE

|

----------------------------------------------------------------------------------

| |

Preventative Trend

| |

-------------------------------------------------------------------- |

| | |

Hard Time On-condition Condition Monitoring

|

Engine Health Monitoring:

Following Parameters

-Engine Oil sy stems

-Engine airborne v ibration monitoring

-Boroscope inspections

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