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 Last point of departure Next point of intended landing Total flying hours Morningstar Aerodrome, Western Cape Province 612.7 Hours on type 11.8 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 Number of people on board Synopsis Surface wind: 250 /12 kt, Temperature: 24 C, Visibi lity: +10 km 1 + 1 No. of people injured 0 No. of people killed 0 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 1 of 14
Section/division Accident and Incident Investigation Division Form Number: CA 12-12b AIRCRAFT INCIDENT REPORT Name of Owner Name of Operator Manufacturer Model Nationality Registration Marks Place : Cygnet Capital CC : Private : Van s Aircraft : RV-8 : South African : ZU-FHM : 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). CA 12-12b 11 JULY 2013 Page 2 of 14
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 CA 12-12b 11 JULY 2013 Page 3 of 14
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). Pilot of ZU-FHM intended to vacate the runway here. 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 - CA 12-12b 11 JULY 2013 Page 4 of 14
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 CA 12-12b 11 JULY 2013 Page 5 of 14
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 On 6 November 2011, the pilot was involved in a serious incident at Morningstar Aerodrome with the Previous incident 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. CA 12-12b 11 JULY 2013 Page 6 of 14
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 CA 12-12b 11 JULY 2013 Page 7 of 14
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. CA 12-12b 11 JULY 2013 Page 8 of 14
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. CA 12-12b 11 JULY 2013 Page 9 of 14
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 10 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. CA 12-12b 11 JULY 2013 Page 11 of 14
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. CA 12-12b 11 JULY 2013 Page 12 of 14
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. CA 12-12b 11 JULY 2013 Page 13 of 14
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 fixedwing 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. CA 12-12b 11 JULY 2013 Page 14 of 14