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CA 12-12b 11 JULY 2013 Page 1 of 14
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
CA 12-12b 11 JULY 2013 Page 2 of 14
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:
CA 12-12b 11 JULY 2013 Page 11 of 14
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.