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Section/division Accident and Incident Investigation Division Form Number: CA 12-12b

AIRCRAFT INCIDENT REPORT AND EXECUTIVE SUMMARY

Reference: CA18/3/2/1019

Aircraft registration ZU-FHM Date of incident 22 November 2013 Time of incident 1120Z

Type of aircraft Van’s RV-8 (aeroplane) Type of operation Private (Part 91)

Pilot-in-command licence type Private Age 57 Licence valid Yes

Pilot-in-command flying experience

Total flying hours

612.7 Hours on type 11.8

Last point of departure Morningstar Aerodrome, Western Cape Province

Next point of intended landing Mossel Bay Aerodrome (FAMO), Western Cape Province

Location of the incident site with reference to easily defined geographical points (GPS readings if possible)

On Runway 27 at FAMO (GPS position: 34°09’32.57” So uth 022°03’17.40” East)

Meteorological information Surface wind: 250°/12 kt, Temperature: 24°C, Visibi lity: +10 km

Number of people on board 1 + 1 No. of people injured 0 No. of people killed 0

Synopsis

The pilot, accompanied by a passenger, departed Morningstar Aerodrome, a private aerodrome located near Cape Town, on a private cross-country flight to FAMO. After a flight of approximately one hour, they joined overhead FAMO at 2 500 ft. The pilot followed the unmanned aerodrome procedure, observed the wind to be from the west and elected to land on Runway 27. While on the descent, he observed a helicopter (Bell 212) operating on the aerodrome with a bambi bucket suspended below it. He broadcast his intentions on the aerodrome frequency 124.20 MHz, stating that he had the helicopter visual. The pilot decided to continue with the approach and configured the aircraft for landing with full flaps (40°) selected. H e observed the helicopter crossing the runway from north to south while on the approach. He broadcast his position stating he was on final approach, to which the helicopter pilot relied: ‘Have you visual, don’t worry, we will be out of your way by the time you get here.’ The pilot continued with the approach and landing, but while taxiing to vacate the runway, the aircraft passed the hovering helicopter some distance away, and started yawing from side to side, the tail lifted and it nosed forward, coming to rest on the runway in a nose-down attitude. Neither of the occupants was injured.

Probable cause

The turbulence generated by the helicopter downwash most probably crossed the path of the light aircraft while it was taxiing along the runway, which caused the tail to lift and the aircraft to nose forward.

ASP date 10 February 2015 Release date

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Section/division Accident and Incident Investigation Division Form Number: CA 12-12b

AIRCRAFT INCIDENT REPORT

Name of Owner : Cygnet Capital CC

Name of Operator : Private

Manufacturer : Van’s Aircraft

Model : RV-8

Nationality : South African

Registration Marks : ZU-FHM

Place : Mossel Bay Aerodrome

Date : 22 November 2013

Time : 1120Z

All times given in this report are Co-ordinated Universal Time (UTC) and will be denoted by (Z). South

African Standard Time is UTC plus 2 hours.

Purpose of the Investigation:

In terms of Regulation 12.03.1 of the Civil Aviation Regulations (1997) this report was compiled in the

interests of the promotion of aviation safety and the reduction of the risk of aviation accidents or incidents

and not to establish legal liability.

Disclaimer:

This report is produced without prejudice to the rights of the CAA, which are reserved.

1. FACTUAL INFORMATION

1.1 History of flight

1.1.1 The pilot, accompanied by a passenger, departed Morningstar Aerodrome, located

near Cape Town, at approximately 1015Z on a private cross-country flight under

visual flight rules (VFR), with their destination being Mossel Bay Aerodrome

(FAMO).

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1.1.2 At 1115Z, they joined overhead FAMO at 2 500 ft. The prevailing wind was

assessed by the pilot to be from the west, and he elected to land on Runway 27. He

joined the left-hand circuit for Runway 27, and while descending, spotted a

helicopter hovering to the northern side of Runway 27. He them made a radio call

on the local aerodrome frequency (124.20 MHz) stating: ‘Foxtrot Hotel Mike (FHM),

have the helicopter traffic visual.’

1.1.3 The pilot decided to proceed with the approach and configured the aircraft for

landing by selecting 40° of flap at an approach spe ed of 80 kt indicated airspeed

(IAS). The pilot then observed the helicopter, a Bell 212 (ZS-HHS) flying towards

the runway and crossing it to the south. He again broadcast his intentions: ‘FHM,

short finals Runway 27, full stop’ to remind the helicopter pilot of the approaching

aircraft. The response from the helicopter pilot was: ‘Have you visual, don’t worry,

we will be out of your way by the time you get here.’

1.1.4 At that point it did not seem to be a problem, so the pilot flying ZU-FHM continued

with the approach, aiming to touchdown as near to the threshold markers as

possible to ensure no conflict with the helicopter traffic. At that point the aircraft

was at a speed of between 70 - 75 kt IAS. Upon crossing the threshold, it was

noted that the helicopter was slinging a bambi bucket approximately 100 ft (30 m)

off the ground, and was still crossing the runway to the south. The pilot of ZU-FHM

continued with the landing and touched down just passed the windsock. The pilot

kept the aircraft in the ‘wheeler’ attitude (tail up) for better visibility. At that point, it

was noted that the helicopter had cleared the runway and was manoeuvring into

the hover near the taxiway that ran parallel to the runway. According to the pilot of

ZU-FHM estimates, it seems that the bambi bucket was still approximately 100 ft

off the ground and the helicopter itself was between 200 - 300 ft off the ground.

1.1.5 The pilot of ZU-FHM continued to taxi along the runway in a wheeler attitude, with

the intention to vacate the runway at the taxiway. As the aircraft rolled passed the

hovering helicopter, it was hit by the downwash (turbulence) from the helicopter,

which caused the aircraft to yaw from side to side and the tail to lift. The pilot

pulled back on the control stick to lower the tail, but the aircraft did not respond.

The tail continued to lift, causing the aircraft to nose forward onto the runway

surface. The propeller, spinner and wheel spats impacted the runway surface and

the aircraft came to rest in a nose-down attitude on the runway surface. The pilot

then called on the aerodrome frequency: ‘Mayday. Aircraft down on runway.’ He

then secured the aircraft by closing the throttle, placing the fuel shut-off lever to

OFF, and switched off the magnetos and master. The two occupants then

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disembarked from the aircraft unassisted. They then lifted the aircraft off its nose

and pushed it to the side of the runway.

1.1.6 In a statement obtained from the pilot-in-command of the helicopter, he indicated

that he had advised the pilot of ZU-FHM about the downwash of the helicopter, yet

the ZU-FHM pilot had continued with the approach and subsequent landing.

1.1.7 The Google earth map in Figure 1 indicates the position of either aircraft at the time

of the occurrence. The distance between the runway and the taxiway was

approximately 48 m (157 ft).

Figure 1: Google earth map indicating the approximate position of both aircraft at the time of the incident

1.2 Injuries to persons

Injuries Pilot Crew Pass. Other

Fatal - - - -

Serious - - - -

Minor - - - -

None 1 - 1 -

Pilot of ZU-FHM intended to vacate the runway here.

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1.3 Damage to aircraft

1.3.1 The aircraft sustained damage to the propeller, spinner, left main landing gear

attachment saddles and bolts. There was also damage to the bottom of the engine

cowling and the main wheel spats. The engine required a shock load inspection.

Figure 2: Damage to the propeller

Figure 3: Damage to the spinner

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1.4 Other damage

1.4.1 There was no other damage caused.

1.5 Personnel information

1.5.1 Pilot-in-command (PIC):

Nationality South African Gender Male Age 57

Licence number 0272229170 Licence type Private

Licence valid Yes Type endorsed Yes

Ratings Night rating, Test pilot class 2

Medical expiry date 30 November 2014

Restrictions None

Previous incident

On 6 November 2011, the pilot was involved in a

serious incident at Morningstar Aerodrome with the

same aircraft, when the left main wheel entered a mole

hole while he was taxiing to the runway and the

propeller struck the ground.

1.5.2 Pilot-in-command flying experience:

Total hours 612.7

Total past 90-days 38.7

Total on type past 90-days 11.8

Total on type 11.8

1.6 Aircraft Information

1.6.1 The Van’s RV-8 is a tandem, two-seat, single-engine, low-wing, home-built

aircraft sold in kit form by Van’s Aircraft. The RV-8 is equipped with conventional

landing gear while the RV-8A version features tricycle landing gear. The design is a

larger development of the RV-4 and is similar in appearance, although larger, than

the earlier model.

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Figure 4: The aircraft ZU-FHM

1.6.2 Airframe:

Type Van’s RV-8

Serial number 82532

Manufacturer Van’s Aircraft

Year of manufacture 2010

Total airframe hours (At time of Accident) 145.3

Last Annual inspection (hours & date) 85.7 22 November 2012

Hours since last Annual inspection 59.6

Authority to Fly (issue date) 21 February 2013

Authority to Fly (expiry date) 19 February 2014

C of R (issue date) (present owner) 4 March 2010

Maximum take-off weight 818 kg

Operating category Private

1.6.3 Engine:

Type Lycoming AEIO-360-H1B

Serial number L-26765-51A

Hours since new 145.3

Hours since overhaul TBO not yet reached

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1.6.4 Propeller:

Type Hartzell C2YR-1BFPY

Serial number CH-45243B

Hours since new 135.3

Hours since overhaul TBO not yet reached

1.7 Meteorological information

1.7.1 The weather information contained in a table below was obtained from the pilot’s

questionnaire.

Wind direction 250° Wind speed 12 kt Visibility +10 km

Temperature 24°C Cloud cover Nil Cloud base Nil

Dew point 12°C

1.7.2 There was no meteorological aerodrome report (METAR) available for FAMO. A

METAR for George Aerodrome (FAGG) was available for 1100Z, and indicated the

wind to be 190° at 10 kt, with few clouds at 5 000 ft and a temperature of 26°C.

FAGG is located 18 nm (34 km) north-east of FAMO.

1.8 Aids to navigation

1.8.1 The aircraft was equipped with standard navigational equipment as per the

minimum equipment list approved by the regulator. There were no recorded defects

to navigational equipment prior to the incident.

1.9 Communication

1.9.1 FAMO is an unmanned aerodrome, therefore the pilot broadcast his intentions on

the very high frequency (VHF) aerodrome frequency 124.20 MHz. He was in radio

contact with the helicopter that was operating at the aerodrome at the time. There

was no breakdown in radio communication between the two aircraft.

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1.10 Aerodrome information

Aerodrome location Mossel Bay Aerodrome (FAMO)

Aerodrome co-ordinates 34°10’00 South 022°00’50 Eas t

Aerodrome elevation 526 ft above mean sea level (AMSL)

Runway designations 09/27

Runway dimensions 18 m x 1 000 m

Runway used 27

Runway surface Asphalt

Approach facilities Landing lights

Aerodrome status Licensed

1.10.1 The runway was resurfaced during February 2013.

1.11 Flight recorders

1.11.1 The aircraft was not equipped with a flight data recorder (FDR) or a cockpit voice

recorder (CVR), nor was either required by the regulations to be fitted to this type of

aircraft.

1.12 Wreckage and impact information

1.12.1 The aircraft came to rest in a nose-down attitude on Runway 27, which resulted in

damage to the propeller, spinner and wheel spats. No damage was noted with

regard to the flight control system of the aircraft.

1.12.2 This was an office-based investigation and therefore no on-site information was

gathered apart from the information that was obtained from the pilot and the

maintenance facility that conducted the repairs.

1.13 Medical and pathological information

1.13.1 Not applicable.

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1.14 Fire

1.14.1 There was no pre- or post-impact fire.

1.15 Survival aspects

1.15.1 Both occupants were properly restrained by the aircraft-equipped safety harnesses.

1.15.2 This incident was associated with low kinetic energy and was considered

survivable.

1.16 Tests and research

1.16.1 None considered necessary.

1.17 Organizational and management information

1.17.1 This was a private flight conducted by the owner of the aircraft.

1.18 Additional information

1.18.1 Hover flight generates downwash (Source: Principles of Helicopter Flight, WJ

Wagtendonk, Chapter 11)

For the rotor to produce the aerodynamic force required to sustain the helicopter in

flight at a constant height, it must exert an equal and opposite force on air. In other

words, the net rotor thrust upwards must be equal to the net downwash. Air is

drawn from a state of rest above the disc and accelerated through the disc,

reaching its final downwash velocity about two rotor diameters below the disc (in

free air conditions).

The final downwash velocity is approximately twice the induced velocity. Its

magnitude depends on:

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Disc loading

Air density.

The higher the disc loading, the higher the downwash velocity. Since, in the hover,

disc loading is proportional to gross weight and total rotor thrust, it follows that the

heavier the helicopter, the greater the downwash velocity.

The less dense the air, the higher the downwash velocity. Hover flight at high

altitude or under conditions of high density altitude involves greater downwash

velocities.

When hovering more than one disc diameter above the ground and out of ground

effect, the downwash beneath the disc dissipates into the surrounding air without

appreciable surface interference.

Figure 5: A helicopter in hover flight and the effect of main rotor downwash

1.19 Useful or effective investigation techniques

1.19.1 No new methods were applied.

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2. ANALYSIS

2.1 Man (Pilot)

The pilot flying ZU-FHM was appropriately rated to conduct the flight. He joined

overhead FAMO with the intention to conduct a full-stop landing. He followed the

unmanned aerodrome approach procedure and observed the only other traffic to be

a helicopter operating on the aerodrome. He broadcast his intentions on the

aerodrome frequency, to which the helicopter crew responded, cautioning him with

regard to downwash generated by the helicopter. The pilot continued with the

approach and subsequent landing on Runway 27. He was aware of the helicopter

manoeuvring in the proximity of the runway. He opted to keep the aircraft in the

‘wheeler’ attitude, which provided him with better visibility (the RV-8 being a tail

dragger type aircraft). He proceeded to taxi along the runway passed the hovering

helicopter, which was overhead the taxiway at the time, approximately 48 m from

the runway. The aircraft then suddenly started yawing from side to side and the tail

lifted above level attitude; the pilot was unable to lower the tail with control input,

applying aft control stick, and the aircraft subsequently nosed forward onto the

runway surface. With the aircraft in the ‘wheeler’ attitude during taxi, the stability of

the aircraft was compromised. A sudden gust of wind from the side or aft position

most probably would have had the same result as the turbulent air that dissipated

into the surrounding air, generated from the downwash of the hovering helicopter.

The pilot was most probably caught off guard when he encountered the turbulent air

and he was unable to control the aircraft on the ground before it nosed forward onto

the runway surface.

2.2. Machine (Aircraft)

ZU-FHM was serviceable for the flight. The pilot was unable to lower the tail once

the aircraft encountered turbulent air generated by the downwash of the hovering

helicopter. Following an examination of the aircraft after the incident, no control

surface malfunctions where noted that could have limited or jeopardised control of

the aircraft. The helicopter remained in hover flight with the bambi bucket

suspended below it while the aircraft joined overhead the aerodrome, the helicopter

crew then crossed the runway from north to south while ZU-FHM was on the

approach for landing.

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2.3 Infrastructure

FAMO is a licensed unmanned aerodrome. There was a serviceable windsock and

the asphalt runway surface was in good condition.

2.4 Environment

Fine weather conditions prevailed during the approach and landing, with the wind

from the west at approximately 12 kt. The pilot landed on Runway 27, into wind.

Weather conditions were not considered to be a factor in this incident.

3. CONCLUSION

3.1 Findings

3.1.1 The pilot flying ZU-FHM was the holder of a valid private pilot licence and had the

aircraft type endorsed on his licence.

3.1.2 The aircraft was in possession of a valid Authority to Fly.

3.1.3 The helicopter pilot had cautioned the pilot of ZU-FHM to be careful of the

downwash after passing over the runway. The pilot opted to continue with the

landing on Runway 27.

3.1.4 The helicopter was in an out-of-ground effect (OGE) hover with a bambi bucket

suspended underneath it, overhead the taxiway, when the aircraft landed on

Runway 27.

3.1.5 The pilot kept the aircraft in the ‘wheeler’ attitude (tail up) after landing to increase

visibility during taxi.

3.1.6 The pilot was unable to arrest the lifting tail with control input (applying aft stick) and

the aircraft nosed forward onto the runway surface.

3.1.7 The aerodrome was a licensed unmanned facility. The runway surface was in a

good condition.

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3.2 Probable cause

3.2.1 The turbulence generated by the helicopter downwash most probably crossed the

path of the light aircraft while it was taxiing along the runway, which caused the tail

to lift and the aircraft to nose forward.

3.3 Contributory factors

3.3.1 The decision by the helicopter crew to cross the active runway and enter into hover

flight over the taxiway, knowing the downwash might be problematic for the landing

light aircraft.

3.3.2 The pilot flying ZU-FHM most probably misjudged the effect of the helicopter

downwash and continued with the landing.

3.3.3 The decision by the pilot taxiing ZU-FHM to keep the aircraft in the ‘wheeler’ attitude

(tail up) and to continue taxiing on the runway passed the hovering helicopter.

4. SAFETY RECOMMENDATIONS

4.1 It is recommended to the Director of Civil Aviation that a designated helicopter

training/manoeuvring area be identified at FAMO, which will limit the effect on fixed-

wing aircraft operations in the vicinity of the runway and taxiway.

4.2 It is recommended to the Director of Civil Aviation that the authority develop

standards for helicopter operations at licenced aerodromes in South Africa.

5. APPENDICES

5.1 None.