AIRCRAFT ACCIDENT REPORT AND EXECUTIVE SUMMARY

Transcription

1 Section/division Accident and Incident Investigations Division Form Number: CA 12-12a AIRCRAFT ACCIDENT REPORT AND EXECUTIVE SUMMARY Aircraft Registration Type of Aircraft Reference: CA18/2/3/9624 ZT-RAC Date of Accident 14 June 2017 Time of Accident 1030Z MD 500E Type of Operation Private (Part 91) Pilot-in-command Licence Type PPL Helicopter Age 28 Licence Valid Yes Pilot-in-command Flying Experience Last point of departure Total Flying Hours Welkom Airport (FAWM)-Free State Province 1030 Hours on Type 2.9 Next point of intended landing Christiana-North West Province Location of the accident site with reference to easily defined geographical points (GPS readings if possible) Bultfontein area on a national road at GPS: 28 13'32.18"S, 26 7'28.70"E and a field elevation of 4491ft Wind direction:195 ; wind speed: 2-6kt; wind temperature:20 C: Visibility: Meteorological Information CAVOK Number of people on board 1+2 No. of people injured 0 No. of people killed 0 Synopsis The pilot accompanied by two passengers was engaged on a private flight from FAWM to Christiana in the North West Province. According to the pilot they had also planned to fly over the area where his company was conducting road constructions on the regional road R700 in the area of Bultfontein for progress observation. Upon reaching the area, the pilot flew over the area as planned at approximately 80ft above ground level (AGL). He then made a turn to the right and the helicopter experienced an engine power loss and began spinning to the right. The pilot maintained control by stopping the spin and decided to execute a forced landing on a road. During a flare, the helicopter cushioning caused lot of dust which obscured the pilot vision and made it difficult to judge the height to the ground. Prior to contacting the ground it began to swing violently to the right due to the loss of tail rotor effectiveness. The helicopter contacted the ground hard with the right skid gear first which broke off., The aircraft was substantially damaged and neither the pilot nor passengers sustained injuries. The investigation revealed that the helicopter power loss was due to the pilot inadvertently cutting off the engine power, resulting in a rapid loss of height, a spin to the right followed by a hard impact with the road surface. Probable Cause Unsuccessful forced landing following a power loss due to the pilot inadvertent cutting off the engine power resulting in a rapid loss of height, a spin to the right followed by a hard impact with the road surface. Contributory factor: The Pilot used incorrect (Robinson R44) recovery technique instead of a correct (MD500E) recovery technique. SRP Date 10 October 2017 Release Date 08 January 2018 CA 12-12a 20 NOVEMBER 2015 Page 1 of 19

2 Section/division Accident and Incident Investigation Division Form Number: CA 12-12a AIRCRAFT ACCIDENT REPORT Name of Owner Name of Operator Manufacturer Model Nationality Registration Marks Place : Aircraft Assets Finance Corporation : Private : Macdonnel Douglas Helicopter INC : MD 500E : South African : ZT-RAC : Bultfontein area on a national road at GPS: 28 13'32.18"S, 26 7'28.70"E and a field elevation of 4491ft Date : 14 June 2017 Time : 1030Z 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 of the Civil Aviation Regulations (2011) this report was compiled in the interest of the promotion of aviation safety and the reduction of the risk of aviation accidents or incidents and not to establish blame or 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 The pilot accompanied by two passengers was engaged on a private flight to Christiana in the North West Province. According to the pilot, they had planned to fly pass the Bultfontein area where his company was conducting road constructions on R700 to observe the progress. Upon reaching the area the pilot descended to about 80ft AGL and commenced with his fly pass as planned and then made a right CA 12-12a 20 NOVEMBER 2015 Page 2 of 19

3 hand turn to follow the road. According to the pilot, during a turn the helicopter engine out light illuminated associated with an audible sound through the earphones and was followed by a loss of power. The helicopter then started pitching the nose up and down and pulling left and right. The pilot immediately rolled the throttle in an attempt to increase engine power and increased the collective control without success. The pilot then entered into an autorotation whereby the helicopter entered into a spin to the right. However the pilot was able to contain the situation and regain control of the aircraft and stopped the spin. He then further made a turn to the right as he passed a gravel road. Figure 1: Shows the google view of the accident site and planned route According to the eye-witnesses who was at the accident site at the time observed a black helicopter flying pass on the left hand side along the road at a low height of approximately 80ft AGL. When the helicopter was passing a T-junction, It was observed making a turn to the right then suddenly it entered a spin before impacting the ground According to the pilot he opted to execute a forced landing on a gravel road which was perpendicular to R700. The aircraft came down at a high rate of descent while rotating to the right. During a flare the aircraft entered a cloud of dust that was caused by aircraft rotor downwash. The aircraft impacted the ground at high vertical velocity and the right hand skid gear broke off on impact The main rotor blades also made contact with the ground while the aircraft was skidding until it stopped at 2 meters before the road information board. The helicopter sustained substantial damages to the right hand skid gear, bottom right CA 12-12a 20 NOVEMBER 2015 Page 3 of 19

4 edge of the fuselage and all five main rotor blades were also damaged The accident occurred during day light conditions on the road R700 facing in the direction North West next to the road information board with GPS position determined to be 28 13'32.18"S, 26 7'28.70"E and a field elevation of 4491ft Above mean sea level 1.2 Injuries to Persons None of the occupants sustained any injuries during the accident sequence. Injuries Pilot Crew Pass. Other Fatal Serious Minor None Damage to Aircraft Figure 2: Shows damages to the helicopter The helicopter sustained substantial damages to the right hand skid gear, bottom right edge of the fuselage and all five main rotor blades were also damaged CA 12-12a 20 NOVEMBER 2015 Page 4 of 19

5 1.4 Other Damage None 1.5 Personnel Information Nationality South African Gender Male Age 28 Licence Number Licence Type PPL Licence valid Yes Type Endorsed Yes Ratings Instrument Medical Expiry Date 30 November 2017 Restrictions Corrective lenses Previous Accidents None Flying Experience: Total Hours Total Past 90 Days 26.8 Total on Type Past 90 Days 2.9 Total on Type The pilot is also a commercial pilot license holder on aeroplanes. According to the available information, the pilot began his private pilot license on helicopter in 2015 on which he attained 60.1 hours on both R22/R44 helicopter types to date. On the 9 th of June 2017 he then began with his conversion on the MD helicopter type and accumulating 2.2hours when he was signed off on the 10 th June 2017 by a qualified type rated instructor allowing him to fly solo to build hours. The aircraft endorsement records applications were submitted to SACAA on 14 June At the time of the accident the application was still pending According to the pilot s logbook the following were the hours accumulated as per aircraft type flown: Helicopter type Hours on type Robinson R Kiss K Robinson R MD500E 369E 2.9 CA 12-12a 20 NOVEMBER 2015 Page 5 of 19

6 1.6 Aircraft Information The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E) Figure 3: Show three view dimensions of the helicopter type The aircraft is an import from Namibia and was initially registered in the SACAA register in The MD 500E, model 369E helicopter is a 5 seater, rotary wing aircraft constructed primarily of aluminium alloy. The airframe structure is eggshaped and provides very clean aerodynamic lines. The fuselage is a semimonocoque structure that is divided into three sections. It is powered by Rolls Royce model 250-C20B gas turbine engine. The main rotor is a fully articulated five bladed system, with anti-torque provided by a 2 bladed semi-rigid type tail rotor. Power from the turbo shaft engine is transmitted through the main drive shaft to the main rotor transmission and from the main transmission through a drive shaft to the tail rotor. An overrunning (one way) clutch, placed between the engine and main rotor transmission permits free-wheeling of the rotor system during autorotation. The landing gear is a skid-type attached to the fuselage at 12 points and is not retractable. Aerodynamic fairing covers the struts. Nitrogen charged landing gear dampers act as spring and shock absorbers to cushion landings and provide ground resonance stability. Provisions for ground handling wheels are incorporated on the skid tubes. CA 12-12a 20 NOVEMBER 2015 Page 6 of 19

7 Airframe: Type MD 500E (369E) Serial Number 0210E Manufacturer Macdonnel Douglas Helicopter Inc Date of Manufacture 1998 Total Airframe Hours (At time of Accident) Last MPI (Date & Hours) 03 June Hours since Last MPI 4.6 C of A (Issue Date/Expiry Date) 14June 2016/ 13 June 2018 C of R (Issue Date) (Present owner) 25 November 2016 Operating Categories Standard Part 127 Engine: Type 250-C20B Serial Number CAE Hours since New Hours since Overhaul Modular Main Rotor: Type 369D21100 (X5) Serial Numbers H970;H971;H973;H974;H978 Hours since New Hours since Overhaul TBO not yet reached Tail Rotor: Type 369D (X2) Serial Numbers C244/ C245 Hours since New Hours since Overhaul TBO not yet reached The helicopter was involved in a main rotor incident strike at airframe hours 1854,4 on 14 February 1995 in the country of origin. All five main rotor blades were changed with the currently installed. According to the available maintenance records, the helicopter was maintained and equipped in accordance with manufacture s approved procedure by the regulator approved AMO. At the time of the accident flight, the helicopter was just transferred from FALA to FAWM to the new owner whose owner paperwork was still under process at CAA offices. CA 12-12a 20 NOVEMBER 2015 Page 7 of 19

8 1.7 Meteorological Information The meteorological conditions as obtained from the pilot s questionnaire Wind direction 195 Wind speed (2-6)kt Visibility CAVOK Temperature 20 C Cloud cover Unknown Cloud base Unknown Dew point Unknown 1.8 Aids to Navigation The helicopter was equipped with standard navigation equipment that meets the requirement of the regulator. There were no reported defects with the navigation equipment at the time of the accident. 1.9 Communications The helicopter was equipped with standard communication equipment that meets the requirement of the regulator. There were no reported defects with the communication equipment at the time of the accident Aerodrome Information The accident occurred on the regional road R700 facing in the direction North Westerly next to the road information board with GPS position of: 28 13'32.18"S, 26 7'28.70"E and a field elevation of 4491ft Flight Recorders The helicopter was not fitted with a cockpit voice recorder (CVR) or a flight data recorder (FDR) and neither was required by the regulation to be fitted to this type of helicopter. CA 12-12a 20 NOVEMBER 2015 Page 8 of 19

9 1.12 Wreckage and Impact Information The helicopter accident occurred on a Regional road R700 which was under construction (Refer to Figure 1). The area surrounding the accident site is private farms with vegetation. According to the pilot, the flight was planned for them to fly pass over the region to observe the progress on the road works and then proceed to the landing destination. According to the pilot, the helicopter s approach was at a 1000ft AGL and then descended to approximately 80ft AGL. Moments after a turn to the right the engine experienced power loss. Figure 4: Shows the ground scars caused by impact sequence The helicopter impacted hard with the ground as a result of loss of control. The impact marks on the road surface began at 1 to 2 meter from the helicopter wreckage on the right hand side. According to the pilot, the helicopter at close proximity to the ground whilst been cushioned caused lot of dust which obscured him from making a clear judgement of the distance to the ground. The helicopter began rotation to the right hand side direction due to loss of tail rotor effect and suddenly contacted the ground hard where after it bounced on towards the tar road. At the time the pilot noticed collision was evitable with the road signage on the side of the road and then turned the helicopter toward the right hand side. The helicopter contacted hard with the right hand skid gear first and began skidding where after it broke off. The helicopter fuselage dropped to the right and began skidding along with the main rotor contacting the ground. The helicopter came to a full stop 2m from the road signage. CA 12-12a 20 NOVEMBER 2015 Page 9 of 19

10 Figure 5: Wreckage as it was found Wreckage examination as it was found: There was hard contact and skidding marks on the tar road edge leading towards the right hand side of the wreckage. The right landing skid gear broke-off from the root attachment points. The right hand fuselage bottom edge was damaged due to scrapping along the tar road. All five main rotor blades made contact with the ground and got damaged. The damage on the rotor blades are consistent with the damage caused by auto-rotation. All annunciating audible and warning lighting were serviceable. The left front door was damaged by the main rotor during the accident sequence Medical and Pathological Information N/A 1.14 Fire There was no evidence of pre or post impact fire during the accident. CA 12-12a 20 NOVEMBER 2015 Page 10 of 19

11 1.15 Survival Aspects The accident was considered survivable. The cockpit was intact with no damages sustained. The ELT did trigger following the accident in which the Search and Rescue made some follow-up and then advised the AIID regarding the situation. A location and time of the activation was provided to the investigating personnel Tests and Research Following the reporting of the alleged engine power loss. The MD helicopter and the engine manufacturers were invited to test both the fuel system on the airframe and on the engine. None of the tests revealed any anomalies that could have contributed to the accident. Research (Refer to the Annexure A) 1.17 Organizational and Management Information This was a private flight under provision of Part According to the maintenance records, the helicopter was equipped and maintained in accordance with the manufacture s prescribed procedures by a regulator approved aircraft maintenance organisation According to the available records, the helicopter was recently bought by a new owner who resides in the area of Welkom in the Free State Province. The helicopter was transferred on the 10 th of June by the accident pilot and the instructor as part of the training. The pilot was the only person available with helicopter flying experience upon its transfer. His helicopter training conversion was conducted to make him ready to operate the machine Additional Information Pilot statement According to the pilot during the reported power loss, he stated that he rolled the throttle in an attempt to increase power on the helicopter engine however it was unsuccessful. CA 12-12a 20 NOVEMBER 2015 Page 11 of 19

12 According to the manufacturer s pilot, the use of throttle during normal operation is not advisable. This is in relation with the helicopter type operating hand book which only indicate the use of throttle twisting (rolling) during engine starting and engine switching off.n 1 and N 2 governor control switches are provided to increase engine power on demand during operation The pilot is more qualified on the piston engine helicopter type. The helicopter type he was flying at the time of the accident was equipped with a turbine engine. Throttle control differential as compared on both helicopters Robinson R44 Helicopter: Information is extracted from Robinson POH Model R44 II Page 3-2 Power failure between 8ft and 500ft AGL Procedure: Lower collective immediately to maintain rotor RPM Adjust collective to keep RPM between 97 and 108 or apply fully down collective if weight prevents attaining above 97 Maintain airspeed until ground approached then begin cyclic flare to reduce rate of descent and forward speed. At about 8feet AGL, apply forward cyclic to level ship and raise collective just before touchdown to cushion landing. Touchdown in level attitude and nose straight ahead. Loss of tail rotor thrust during hover 1. Failure is usually indicated by right yaw which cannot be stopped by applying left pedal. 2. Immediately roll throttle off into detent spring and allow aircraft to settle. 3. Raise collective just before touchdown to cushion landing UNANTICIPATED YAW / LOSS OF TAIL ROTOR EFFECTIVENESS (LTE) Unanticipated yaw is the occurrence of an un-commanded yaw rate that does not subside of its own accord and, which, if not corrected, can result in the loss of helicopter control. This un-commanded yaw rate is referred to as loss of tail rotor effectiveness (LTE) and occurs to the right in helicopters with a counter clockwise rotating main rotor and to the left in helicopters with a clockwise main rotor rotation. CA 12-12a 20 NOVEMBER 2015 Page 12 of 19

13 Again, this discussion covers a helicopter with a counter-clockwise rotor system and an anti-torque rotor. LTE is not related to an equipment or maintenance malfunction and may occur in all single-rotor helicopters at airspeeds less than 30 knots. It is the result of the tail rotor not providing adequate thrust to maintain directional control, and is usually caused by either certain wind azimuths (directions) while hovering, or by an insufficient tail rotor thrust for a given power setting at higher altitudes. For any given main rotor torque setting in perfectly steady air, there is an exact amount of tail rotor thrust required to prevent the helicopter from yawing either left or right. This is known as tail rotor trim thrust. In order to maintain a constant heading while hovering, you should maintain tail rotor thrust equal to trim thrust. The required tail rotor thrust is modified by the effects of the wind. The wind can cause an un-commanded yaw by changing tail rotor effective thrust. Certain relative wind directions are more likely to cause tail rotor thrust variations than others. Flight and wind tunnel tests have identified three relative wind azimuth regions that can either singularly, or in combination, create an LTE conducive environment. These regions can overlap, and thrust variations may be more pronounced. Also, flight testing has determined that the tail rotor does not actually stall during the period. When operating in these areas at less than 30 knots, pilot workload increases dramatically Useful or Effective Investigation Techniques None 2. ANALYSIS 2.1 According to the available information, the pilot is a private pilot license holder on helicopter with 2.9 hours on the helicopter type. Prior to the accident flight, the pilot flew the helicopter on two occasions during his helicopter type conversion and accumulated 2.2 flying hours. He was then signed off to fly unsupervised by a helicopter type rated instructor allowing him to building hours. It is the investigator s opinion that the insufficient training offered to the pilot was influenced by the operational matters. The pilot was the only person who has helicopter flying experience in which the helicopter was recently purchased and was delivered to their facility. It is evident that the pilot training insufficient as per hours accumulated by the pilot. CA 12-12a 20 NOVEMBER 2015 Page 13 of 19

14 2.2 The pilot was more experienced on flying a reciprocating engine equipped helicopters (R44 s) which had a difference of engine power increase settings on demand operations. On the R44 which is also fitted with a governor switch, raising a collective control will increase engine power and also adjusting the blade pitch symmetrically to maintain minimum required power to sustain lift. However on the MD helicopter type to increase engine power demands are controlled by adjusting either N 1 or N 2 governor switch allocated on the collective control column raising the collective on the MD will only increase the pitch and not the power. The pilot stated that during a turn, the helicopter commenced an un-commanded yaw to the right in which afterwards he started operating the twist grip in an attempt to increase engine power however was unsuccessful. The recovery (procedure) technique used by the pilot to increase engine power on the helicopter type by using twist grip either than the allocated governor switches N 2 is used on an R 44 and not in the case of MD helicopter. 2.3 The pilot stated that during a turn to the right hand side, the helicopter experienced an un-commanded yaw to the right. These actions are indicative to an unanticipated yaw relating to the loss of tail rotor effectiveness. The helicopter is equipped with five main rotor blade system that rotate counter clockwise. This will cause the nose of the aircraft to have a turning effect to the right, therefore to counter act this turning effect the use of the left anti-torque pedal will be required to compensate this movement. 2.4 The manufacturer was invited to assist with the investigation of fuel system and engine. The engine was removed and bench tested on a test cell. The engine was performing in accordance with the manufacture s specification. No anomalies were noticed during any of the tests relating to the fuel system and reported engine power loss and the flight control systems. 2.5 The reported weather condition at the time leading to the accident did not have any contributions towards this accident. 3. CONCLUSION 3.1 Findings The pilot was signed off to fly the helicopter solo for hour building by a helicopter type rated instructor at approximately 2.2hours flying experience. The pilot s flying experience and familiarisation on the helicopter type was found to be insufficient at CA 12-12a 20 NOVEMBER 2015 Page 14 of 19

15 the time of the flight The helicopter type was not yet endorsed on his license at the time of the accident. The application was submitted on the same date of the accident, however, he was signed off by a type rated instructor allowing him to build hours unsupervised The pilot had more flying hours on the piston engine helicopters as compared to the turbine engine equipped helicopters The helicopter was maintained and equipped by the regulator approved AMO in accordance with manufacture s approved procedures. The helicopter had enough fuel at the time of the accident Good weather conditions prevailed in the surrounding area and it cannot be attributed to the cause of the accident The pilot only had accumulated 2.9 hours on type which was inadequate to handle any emergencies that may occur and control the situation safely The engine was removed and tested on test cell and it was running in accordance with manufactures specification. 3.2 Probable Cause/s The helicopter experienced engine power loss due to the pilot inadvertently cutting off the engine power resulting in a rapid loss of height, a spin to the right followed by a hard impact with the road surface. Contributory factor: The Pilot used incorrect (Robinson R44) recovery technique instead of a correct (MD500E) recovery technique. CA 12-12a 20 NOVEMBER 2015 Page 15 of 19

16 4. SAFETY RECOMMENDATIONS 4.1 It is recommended to the DCA in the interest of aviation safety to review and possibly impose the minimum hours required for conversation training of piston helicopter to turbine powered helicopter. The turbine engine helicopter has more functions and very complex systems and the pilot had only 2.2 hours for conversion and it was evident during this accident that he had difficulties in handling the emergencies and to land the helicopter safely. 5. APPENDICES 5.1 The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E) Section 4 Pages (4-23, 4-24) CA 12-12a 20 NOVEMBER 2015 Page 16 of 19

17 5.1 Annexure A The information is extracted from: Rotorcraft Flight Manual: MD 500E (Model 369E) Section 4 Pages (4-23, 4-24) Low rotor Speed Indications: Red [Engine out] warning indicator ON and Audible warning in headset Drop in RPM/ Change in noise level Note: The LOW ROTOR warning is activated when N r falls below 468. Conditions: Low rotor RPM will most commonly be associated with the following Engine failure Transient rotor droops during large, rapid increases in power. Governor failure producing an under speed. Procedure: Respond immediately to the low rotor RPM warning by adjusting collective to maintain rotor RPM within limits. Check other Caution/ Warning indicators and engine instruments to confirm engine trouble and respond in accordance with appropriate procedures in this section. Low speed Manoeuvring Manoeuvers that exceed thrust capability of the tail rotor should be avoided. Note: Conditions where thrust limits may be approached are: High density altitude, high gross weight, rapid pedal turns and placing the helicopter in a down wind conditions. These conditions may exceed the thrust capability of the tail rotor. Extreme aircraft attitudes and manoeuvres at low speeds should be avoided. Warning: Un-coordinated turns/ manoeuvers may cause fuel starvation with less than 35 pounds of fuel on board. Warning: Observe the cross-hatched region of Height Velocity Diagram (Ref Section V). These represent airspeed / altitude combinations from which a successful autorotation may be difficult to perform. Operation within the cross hatched area is not prohibited but should be avoided. CA 12-12a 20 NOVEMBER 2015 Page 17 of 19

18 Practice Autorotation Warning Performance throttle rigging check prior to attempting practice auto rotations. Mis-rigging of the throttle control may result in inadvertent flameout during rapid closing twist grip to the ground idle position. Uncoordinated turns/ manoeuvres may cause fuel starvation with less than 35 LBS of fuel. Do not practice autorotation if the FUEL LEVEL LOW caution indicator is ON. Caution : Do not perform intentional full touchdown autorotation with blade tracking reflectors installed on blade tips. For autorotation decent, the twist-grip should be in the full open/ ground idle position. However, if a practice autorotation landing (minimum engine power) is desired, rotate the twist-grip to the ground idle position. Increase collective pitch after establishing autorotation to prevent rotor over speed if flight is at high gross weight or high density altitude. To reduce rate of descent or to extend gliding distance, operate at minimum rotor rpm. Restore ROTOR RPM (N R ) by lowering collective prior to flare out. If a power recovery is desired, lower collective to full down, rotate the twist-grip to the full open position, verify that N 2 is between 102% and 103% percent and that full engine power is available prior to increasing collective. Conduct practice autorotation at 131knots IAS or below (see V ne placards). Maintain rotor between 420 and 523 by use of the collective control. Note: Keeping the rotor above 420RPM will place the engine above the N 2 speed avoid range. Caution: Refer to Section II Power turbine (N 2 ) speeds avoid ranges. Maximum glide distance is attained at 80knots and 410 rotor RPM. Minimum rate of descent is attained at 60knots and 410 rotor RPM Note: Glide distance attained during an actual engine autorotation may be less than the glide distances achieved during practice autorotation s when operating at reduced RPM (N 2 /N r needles joined). Touchdown in a level attitude Avoid use of aft cyclic control or rapid lowering of collective pitch during initial ground contact or during ground slide. CA 12-12a 20 NOVEMBER 2015 Page 18 of 19

19 Autorotation RPM Normal rotor RPM (collective fully down) is 485±5 RPM at 2250 pound gross weight at sea level, 60knots. Rotor speed will decrease approximately 10RPM for each 100 pounds reduction in gross weight and increase approximately 6.5 RPM for each 1000 foot increase in density altitude. For gross weights greater than 2250 pounds, increase collective control as required to maintain approximately 485 RPM. CA 12-12a 20 NOVEMBER 2015 Page 19 of 19