Transcript
Section/division
Form Number: CA 12-12a
Accident and Incident Investigations Division
AIRCRAFT ACCIDENT REPORT AND EXECUTIVE SUMMARY
Reference: Aircraft Registration
ZS-RUC
Type of Aircraft
MI-8MTV-1
Date of Accident
CA18/2/3/8152
23 July 2006
Time of Accident
Type of Operation
Fire fighting Licence Valid
Pilot-in-command Licence Type
ATP-Helicopters
Age
Pilot-in-command Flying Experience
Total Flying Hours
Unknown
37
Last Point of Departure
Nelspruit Aerodrome (FANS), Mpumalanga
Next Point of Intended Landing
Nelspruit Aerodrome (FANS), Mpumalanga
Hours on Type
1249Z
Yes Unknown
Location of the Accident Site with Reference to Easily Defined Geographical Points (GPS readings if possible) Spitskop quarry dam near Sabie, Mpumalanga Province (GPS Coordinates S 25° 09.081’ E 030° 49.897’) Meteorological Information
CAVOK, wind northerly at 10 kt, temperature 25 °C, clouds nil
Number of People on Board
3+0
No. of People Injured
3
No. of People Killed
0
Synopsis The helicopter was engaged in a forest fire fighting detail near Sabie when the accident occurred. After three loads of water were bombed onto the forest fire, the helicopter was hovering approximately 5 metres above the quarry dam. The bambi bucket was then submerged into the water for the next load, but as it was hoisted out of the water from hover into forward flight, the crew heard a loud bang followed by a high-frequency vibration, accompanied by loss of main rotor revolutions per minute (RPM) and audible warnings. As the helicopter started to yaw to the left, the flight engineer shut down both engines in order to prevent the helicopter from spinning. The helicopter struck the water and capsized as the main rotor blades impacted the water. The crew evacuated the helicopter through the pilot-incommand’s window as the helicopter sank rapidly into the water. The helicopter was substantially damaged when the helicopter struck the water. The pilot-incommand, the co-pilot and the flight engineer sustained minor injuries in the accident.
Probable Cause The right-hand engine turbine section failed, which caused back pressure in the combustion chamber, reverse flow of the gases and stalling of the compressor, which was evident by a loud bang and a high-frequency vibration. Contributory factor: The helicopter was too low above the surface to recover even though the left-hand engine gained augmentation power and increased in engine power and main rotor RPM. IARC Date CA 12-12a
Release Date 23 FEBRUARY 2006
Page 1 of 42
Section/division
Accident and Incident Investigations Division
Form Number: CA 12-12a
AIRCRAFT ACCIDENT REPORT Name of Owner/Operator Manufacturer Model Nationality Registration Marks Place
: UTAir South Africa (PTY) LTD : Kazan Helicopter Plant : MI-8MTV : South African : ZS-RUC : Spitskop quarry dam near Sabie
Date Time
(GPS at the following co-ordinates: S 25° 09.081 E 030° 49.897 : 23 July 2006 : 1249Z
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 interest 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 given without prejudice to the rights of the CAA, which are reserved.
1.
FACTUAL INFORMATION
1.1
History of Flight
1.1.1 The pilot-in-command departed Nelspruit Aerodrome (FANS) with the co-pilot who was the pilot flying and a flight engineer, and 22fire-fighters on board to an area at Spitskop near Sabie to fight a forest fire that had erupted. 1.1.2 The pilot-in-command stated that they arrived near the area of the forest fire and, with the engines still running, the fire-fighters disembarked from the helicopter. The bambi bucket was then fitted to the main gearbox of the helicopter before they flew to the Spitskop quarry dam where they proceeded to uplift water with the bambi bucket and start bombing the forest fire. 1.1.3 The pilot-in-command further stated that after three loads of water were bombed at the forest fire, the helicopter was hovering approximately 5 m above the quarry dam. The bambi bucket was then submerged into the water for the next load, but as it was hoisted out of the water from hover into forward flight, they heard a loud bang followed by a high-frequency vibration, accompanied by loss of main rotor RPM and audible warnings. The pilot-in-command then immediately jettisoned the bambi bucket and lifted the speed levers in case of an engine failure, but the collective CA 12-12a
23 FEBRUARY 2006
Page 2 of 42
was already at maximum power. As the helicopter started to yaw to the left, the flight engineer shut down both engines in order to prevent the helicopter from spinning. The helicopter sank rapidly, struck the water and capsized as the main rotor blades impacted the water. 1.1.4 The pilot-in-command was seated on the left-hand side and the co-pilot was seated on the right-hand side of the cockpit. The flight engineer was seated just behind the two pilots. All three evacuated the helicopter through the left-hand side cockpit window. They then swam to safety as the helicopter sank rapidly into the water. 1.1.5 The Google aerial view below shows the GPS flight path flown by the helicopter during the fire bombing operation. The track highlighted represents the last recorded track before the accident occurred.
Figure 1: Aerial view extract from the BAE report showing the flight path. The track highlighted represents the last recorded track before the accident occurred. See Appendix 1 for the full BAE report on the GPS. 1.2
Injuries to Persons Injuries Fatal Serious Minor None
CA 12-12a
Pilot 1 -
Crew 2 -
Pass. -
23 FEBRUARY 2006
Other Page 3 of 42
1.2.1 According to the available information, the pilot-in-command, co-pilot and flight engineer sustained minor injuries in the accident. They were taken to hospital for observation and released the same day. 1.3
Damage to Aircraft
1.3.1 The helicopter was substantially damaged during the impact sequence with the water. The main rotor blades, including the drive shaft, tail rotor drive shaft and tail rotor blades, were also severed when the helicopter struck the water. See Photo 1 below.
Photo 1: Showing the helicopter during the recovery process.
1.4
Other Damage
1.4.1 There was no other damage to property except that the water in the quarry dam was contaminated by the fuel and lubricants that leaked out of the helicopter.
Photo 2: Showing contamination to the quarry dam
CA 12-12a
23 FEBRUARY 2006
Page 4 of 42
1.5
Personnel Information
1.5.1 Pilot in Command Nationality Licence Number Licence valid Ratings Medical Expiry Restrictions
South African Gender Male Age 37 0270231772 Licence Type ATP - Helicopters Yes Type Endorsed Yes Instruments, Night, Under-sling / Winch and Culling 31 October 2006 None
Previous Accidents
11 January 1995 Fuel exhaustion during game capturing. 04 May 2000 engine failure during the uplifting heavy load.
Flying Experience: Total Hours Total Past 90 Days Total on Type Past 90 Days Total on Type
Unknown Unknown Unknown Unknown
Note: The pilot-in-command failed to provide his flying experience even after numerous requests were made. The current SACAA file does not have this information. 1.5.2 Co-Pilot Nationality Licence Number Licence Valid Ratings Medical Expiry Restrictions Previous Accidents
South African 0271012007 Yes Night 30 June 2007 None None
Gender Licence Type Type Endorsed
Male Age 27 Commercial Helicopters Yes
1.5.4 Flying Experience: Total Hours Total Past 90 Days Total on Type Past 90 Days Total on Type
400.00 150.00 Unknown Unknown
Note: The co-pilot failed to provide his flying experience even after numerous requests were made. The above flying hours were obtained from the pilot’s file at the SACAA office, on the 19 of June 2006. CA 12-12a
23 FEBRUARY 2006
Page 5 of 42
1.5.2 Flight Engineer Nationality South African Licence Number FE 547 Licence valid Yes
Gender Male Licence Type Type Endorsed
Age 35 Flight Engineer Yes
Flying Experience: Total Hours Total on Type Past 90 Days
1.6
1785.2 43.5
Aircraft Information
1.6.1 Airframe: Type Serial Number Manufacturer Date of Manufacture Total Airframe Hours (At time of Accident) Last MPI (Date & Hours) Hours since Last MPI C of A (Issue Date) C of R (Issue Date) (Present owner) Operating Categories
Mi-8MTV-1 95907 Kazan Helicopter Plant 07 May 1992 4867.1 15 May 2006 28.3 24 August 2004 28 July 2004 Restricted
4838.8
1.6.2 Engine No 1(Left hand): Type Serial Number Manufacturer Hours since New Hours since Overhaul
TV3-117BM 7087883100605 Zaporozhye 1345.9 891.3
1.6.3 Engine No 2(Right hand): Type Serial Number Manufacturer Hours since New Hours since Overhaul
TV3-117BM 7087881200118 Zaporozhye 1822.9 891.3
1.6.4 The owner imported the aircraft from Russia in July2004 and the application for CA 12-12a
23 FEBRUARY 2006
Page 6 of 42
registration on the South African Civil Aviation Register (SACAR) was submitted to the regulator on 27 July 2004. 1.6.5 The TV3-117BM turbo-shaft engine family features a single-shaft configuration. The 12-stage compressor has a variable area guide vane. The combustion chamber is a straight flow annular type. The engine has a two-stage free turbine with an overspeed protection system. 1.6.6 According to the flight folio, no defects were recorded with respect to the airframe or engines.
1.7 Meteorological Information 1.7.1 The following weather was obtained from the South African Weather Service: Wind Direction Temperature
360°
Dew Point
Unknown
21 °C
Wind Speed Cloud Cover
5 kts
Visibility
9999
Few
Cloud Base
5 000 ft AGL
1.7.2 According to the pilot questionnaire, the weather conditions were as follows:
1.8
Wind direction
Northerly
Temperature
25ºC
Dew Point
Not known
Wind Speed Cloud cover
10 knots
Visibility
9999
Sky clear
Cloud base
Nil
Aids to Navigation
1.8.1 The helicopter was fitted with standard navigational instruments as certified for this type of helicopter, and none were reported unserviceable prior to the accident. 1.9
Communications
1.9.1 The helicopter was fitted with standard communications equipment as certified for this type of helicopter, and none were reported unserviceable prior to the accident.
1.10
Aerodrome Information
1.10.1 The accident occurred whilst uplifting water from a quarry dam near Sabie during a fire-fighting operation (GPS co-ordinates: S25° 09.08’1 E030° 49.897’).
1.11
Flight Recorders
CA 12-12a
23 FEBRUARY 2006
Page 7 of 42
1.11.1 The helicopter was fitted with a Flight Data Recorder (FDR) and a Cockpit Voice Recorder (CVR) as required by regulation.
1.11.2 The cockpit voice recorder (CVR) was downloaded in Russia. The CVR information could however not be copied onto a disc or a tape as both the manufacturer and the operator had no capabilities at the time. 1.11.3 The Flight Data Recorder (FDR) was successfully downloaded by the manufacturer in Russia. Time 00:34:24 00:34:26 00:34:27 00:34:29 00:34:30 00:34:32
Collective Pitch 10.7⁰ 11.2º 10.7° 9.38° 11.0° 10.5°
RPM: Left Engine 95.4% 98.8% 99.3% 99.4% 99.6% 99.6%
RPM: Right Engine 95.5% 99.1% 78.9% 57.8% 50.7% 44.1%
T3: Left Engine 823.1 891.8º C 907.7°C 932°C 929.8°C 390.6.7°C
T3: Right Engine 857.7 939.9ºC 1049°C 960.7°C 911.7°C 348.4°C
RPM: Main Rotor 95.7% 95.8% 89.4% 84.9% 81.8% 80.5%
AC: GEN 1 On Line On Line On Line Off Line Off Line Off Line
AC GEN2 On Line On Line On Line Off Line Off Line Off Line
1.11.4 The flight data recorder (FDR) was downloaded by the manufacturer in Russia and The following parameters were noted as shown on the above table: a) According to the Data that was downloaded from the FDR, the T3: Right Engine exhaust gas temperature (EGT) was reading approximately 35°C higher than the T3: Left Engine temperature for some time according to the parameters that was downloaded from the FDR. b) At 00:34:26 the left hand EGT indicated 891.8°C at 98.8% RPM and the right hand EGT indicated 939.9°C at 99.1% RPM which showed tha t the right hand engine was running 48.1°C hotter than the left hand engine just before the engine surged and subsequently stalled. c) At 00:34:27 the right hand engine surged (stalled) and the engine EGT peaked at a temperature of 1049 °C within a few seconds when th e gas generator and power turbine were being destructed and some thermocouples melted due to the excessive heat.
d) At 00:34:29 both AC Generators tripped off when the main rotor RPM reached 88%, which is in accordance with the aircraft flight manual. e) At 00:34:26 to 00:34:32 the right hand engine RPM dropped from 99.1% to 44.1% after the engine gas generator and power turbine were subsequently destructed. The left hand engine RPM indicated 99.6% with an EGT of 929.8 °C just before the engineer also shutdown the left hand engine. f) Due to the decay of the right hand engine power, the left-hand engine augmentation power was automatically increased from 95.4% to 99.6% RPM as a designed safety feature before the engines were shut-down by the flight engineer.
CA 12-12a
23 FEBRUARY 2006
Page 8 of 42
1.12
Wreckage and Impact Information
1.12.1 The helicopter was uplifting water from the Spitskop quarry dam in the Sabie area for forest fire fighting purposes. The helicopter was hovering steadily approximately 5 metres above the quarry dam water level with the bambi bucket already hoisted out of the water when the loss of main rotor RPM caused the helicopter to suddenly yaw to the left. The bambi bucket was immediately jettisoned by the pilot-incommand as the co-pilot was the pilot flying. The helicopter sank rapidly whilst rotating to the left and capsized to the right as the main rotor blades struck the water. The helicopter sank rapidly in the water. 1.12.2 The tail boom and tail rotor drive shaft were severed in two places and were only still attached to the main wreckage by the electrical wiring spanned along the tail boom. Pieces of the main rotor blades were located at the bottom of the dam.
Photo 3
Photo 4
Photo 5
Photo 6
The photos above shows the helicopter yawing to the left before rolling to the right and capsized
CA 12-12a
23 FEBRUARY 2006
Page 9 of 42
Photo 7 showing the helicopter inverted and damage to the tail boom
1.13
Medical and Pathological Information
1.13.1 The pilot-in-command (PIC) and co-pilot both sustained minor bruises to their faces and hands and the flight engineer sustained some injuries to his neck. They all were taken to hospital for observation and were all released on the same day.
1.14
Fire
1.14.1 There was no evidence of a pre- or post-impact fire.
1.15
Survival Aspects
1.15.1 The accident was considered survivable as the helicopter was hovering at approximately 5 metres above the quarry dam. The PIC opened the left hand cockpit window before the helicopter sank into the water and the three crew members vacated the helicopter through the window and swam to safety.
1.16
Tests and Research
1.16.1 The helicopter with the engines still attached to the airframe was recovered from the quarry dam and transported to the Aircraft Maintenance Organisation (AMO) facility at Lanseria Aerodrome where a visual inspection was conducted on the helicopter and engine to assess the damage sustained and possible cause of the engine failure. 1.16.2 As the AMO at Lanseria Aerodrome was not equipped with the required tools and equipment to dismantle and examine the engine, it was decided to transport the helicopter to the Operator/AMO/Manufacturer in Russia for further investigation. 1.16.3 The helicopter with both engines still attached to the airframe was thus transported to the Operator/AMO/Manufacturer in Russia for further examination to determine the probable cause of the right hand engine failure. The Russian Authorities conducted the investigation in the presence of a South African Aircraft Accident Investigator (AIID). CA 12-12a
23 FEBRUARY 2006
Page 10 of 42
Photo 8 showing the engines during removal at the premises of the Operator in Russia
1.16.4 Visual examination of the right hand engine with endoscopes concluded the following observations: a) The fuel nozzles and the flame tube show no damage in the visible areas. b) Four (4) of the thermocouples located in the lower part of the engine were of green/grey colour and the lower part of the thermocouple deformed. c) The 1st turbine nozzle guide vane of the compressor turbine had numerous torn out pieces on the inlet blade edges were a green/grey colour. d) The 1st stage of the compressor turbine was destroyed in the visible area and the attached parts of the blades could be observed up to the central part.
Photo 9
CA 12-12a
Photo 10
23 FEBRUARY 2006
Page 11 of 42
e) The 2nd turbine nozzle guide vanes of the compressor turbine and the 1st nozzle guide vanes of the free turbine had numerous damages such as torn out and twisted metal of the blades as shown on photos 9 and 10 above.
Photo 11
Photo 12
There was no evidence of foreign object ingestion as the engine was fitted with an engine intake protector and the compressor and intake section showed no sign of any foreign impact damage as shown on photos 11 and 12 above. f) It was further established that the 1st stage compressor turbine including the nozzle guide vanes and the free turbine blades were further damaged by the high temperatures.
1.16.5 The left hand engine was also visually inspected and was considered serviceable at the time of impact. Damage to the engine occurred during the accident sequence and during the rundown after the engine was shut down. 1.16.6 The hydraulic system showed no visual damage of the hydraulic components and the hydraulic tubes with no visible leaks. 1.16.7 The right hand engine was transported to the Russian Engine Manufacturer for further investigation in order to establish the cause of the engine failure during the flight. The engine was disassembled in accordance with the established procedures and according to the attached Appendix 2 Technical Report submitted by the Russian Investigation Board they concluded the following: 1.16.8 1) Compressor: The compressor inlet guide vanes and guide vanes of all Compressor stages have mechanical damages, dents bends, metal tear-outs of different levels. The length of the chord of compressor rotor 1st stage blade section VIII is 26, 18 – 27,33mm (according to the Overhaul Manual minimum permissible size at the moment is 27, 60 mm). 2) Gas generator: All blade airfoils of the 1st stage 7841.9001 are broken to ½ of the upper CA 12-12a
23 FEBRUARY 2006
Page 12 of 42
blade tip shroud platforms and the remaining part of the blades with blade roots are dented at the leading edges. Airfoils of the 2nd stage blades are broken at the level of 1/3rd of their length with mechanical damages. The 2nd stage guide vanes are deeply dented and torn. 3) Free Turbine: The Free turbine 3rd and 4th stage blades and nozzle guide vanes have different degree of damage caused by destroying particles of the 1st and 2nd stage rotor wheel blades in the course of engine operation till it shut down. 4) Thermocouple wiring harness The thermocouple wiring harness is fitted with 14 thermocouples T-102 with the results of the external inspection as follow: The fluoroplastic tubes of thermocouples 1, 4 and 5 are melted. Thermocouples 1 & 4 shows traces of exposure to high temperature. Deformation of stagnation chamber – change of geometrical dimensions and erosion of inlets of more than 3.2mm. Resistance of the thermocouples insulation (R) is from 0, 4 to 10³ megohm (resistance of used thermocouple insulation resistance shall be at least 0, 02 megohm. The thermocouples located at the lower part of engine turbine is green-grey coloured and deformed. According to the attached Appendix 2 the thermocouple wiring harness was exposed to temperatures exceeding the normal operational range causing deformation of thermocouples 1 and 4 and melting of fluoroplastic tubes of thermocouples 1,4 and 5. 1.16.9 The Russian Authorities concluded in their Technical Valuation Report finding that the destruction of the gas generator and power turbine could have been caused by an overheat condition and subsequent surge. 1.17
Organisational and Management Information
1.17.1 The helicopter was being used for fire-fighting purposes at the time of the accident and was operated by an Operator with a valid OAC. The helicopter was leased from UTAir South Africa for fire fighting operations. 1.17.2 The helicopter was maintained by UTAir South Africa, and according to the available records the Aircraft Maintenance Organisation (AMO) that certified the last MPI on the helicopter prior to the accident was in possession of a valid AMO (892) approval Certificate. 1.17.3 The aircraft maintenance engineers (AME) that maintained the helicopter at the aircraft maintenance organisation (AMO) at Lanseria airport were properly licensed by the Russian Authorities but their licences were not validated by the SACAA. Some of the Russian AME’s that maintained the helicopter at Lanseria airport could not speak or understand English. 1.17.4 At the time of the accident, the AMO Chief Maintenance Engineer was out of the country. The ground crew members who carried maintenance work on the aircraft, were all Russian citizens without South African validations. CA 12-12a
23 FEBRUARY 2006
Page 13 of 42
1.17.5 The insignia/placards and warning systems on the helicopter were only in Russian.
Figure 9: The placards and instruments labelled in Russian
CA 12-12a
23 FEBRUARY 2006
Page 14 of 42
1.18
Additional Information
1.18.1 Following the FDR information above (paragraph 1.11), the following table was extracted from the Aircraft Maintenance Manual (AMM) and / or Pilots Operating Handbook (POH); Mode of operation. Mode parameters Modes Power (hp)
Emergency Mode Takeoff Mode Nominal Mode Cruising mode 1 Cruising Mode 2 Idling Mode
2200 2000 1700 1500 1200 Not less than 200
Parameter of the modes RPM speed in % Temperature of gases before the Compressor Main Rotor compressor turbine rotors 97,4 ± 0.5 96,3 ± 0.5 94.7 ± 0.5 93,6 ± 0.5 91,7 ± 0.5 73 + 6
93 ± 1 93 ± 1 95 ± 2 95 ± 2 95 ± 2 35-55-1 45-65-2
920 890 845 815 770 Not more than 780
Specific Consumption of fuel (kg /hr.hp.) 230 236 250 270 290 Not more than 165 kg/hr
1.18.1.1 The table above indicates that during an engine failure the operating engine will automatically increase in power. This occurs with the aid of the pneumatic line connected to both fuel control units (FCU) between the two engines. 1.18.1.2 In the event of one engine fail during takeoff, the compressor RPM of the operating engine augmentation power will increase automatically by 10%.and will result in the engine power increasing on the operating engine to an Emergency Mode of 2200 hp. 1.18.1.3 As the right engine failed with a loss of power, the left engine RPM started to increase transitioning towards augmentation power. Although the left-hand engine gained augmentation power, the helicopter was too close to the surface of the water at the quarry dam to recover successfully. As the helicopter started yawing to the left, the engineer cleaned the live engine by retarding the throttle as the helicopter struck the water.
Photo 13: Showing the placards and instruments labelled in Russian.
CA 12-12a
23 FEBRUARY 2006
Page 15 of 42
1.18.2 During the initial interviews with the crew, there was confusion about the warning that the audible warning was heard. One of the crewmembers stated that it gave a gearbox warning and the other two stated that it gave a generator audible warning of “Ganarata“ in the Russian language which referred to the generator. 1.18.3 According to Aircraft Flight Manual, failed generators in-flight is indicated with a voice alert: “First generator failed”, “second generator failed” – transmitted by a voice warning system. In addition, the following occurs: 1.18.3.1
Flashing of annunciators GENERATOR I FAIL and GENERATOR II FAIL
1.18.3.2
Voltmeter pointer sets against scale zero point when shifting voltage selector switch to position FIRST GENERATOR, SECOND GENERATOR: Amp meter pointers of both generators set against zero point.\
1.18.4 1.18.3 In almost all cases, a severe compressor stall stagnates or stops the airflow. An aerodynamic stall of the turbine can cause a back pressure in the combustion chamber resulting in reverse flow of the gases and stall of the compressor. One of the significant effects of severe compressor stall is disruption of the air flow and over-temperature of the turbine section. (Aircraft Accident Investigation by Richard H. Wood)
1.19
Useful or Effective Investigation Techniques
1.19.1 None. 2.
ANALYSIS
2.1
After three loads of water were fire bombed at the forest fire at Spitskop near Sabie, the helicopter was hovering approximately 5 metres above the quarry dam for the next load of water with the bambi bucket submersed in the water. As the bambi bucket was hoisted out of the water to go into forward flight, the crew heard a loud bang followed a high vibration and loss of main rotor RPM.
2.2
Although the augmentation take off power was automatically increased on the lefthand engine when the right hand engine experienced an engine failure, the helicopter was too low above the water to recover successfully and to go into forward flight. The pilot-in-command immediately released the bambi bucket and the flight engineer shut down the engines when the helicopter yawed to the left. The helicopter sank rapidly and capsized as the main rotor blades impacted the water.
2.3
The crewmembers escaped through the left hand cockpit window with only minor injuries sustained.
2.4
There was no evidence of foreign object ingestion as the engine was fitted with an
CA 12-12a
23 FEBRUARY 2006
Page 16 of 42
engine intake protector and the compressor and intake section showed no sign of any foreign impact damage. 2.5
The hydraulic system showed no visual damage of the hydraulic components and the hydraulic tubes with any visible hydraulic leaks.
2.6
The helicopter with both engines still attached to the airframe was transported to the Russian authorities in Russia for further investigation as the AMO at Lanseria Aerodrome was not equipped with the proper tools and equipment to dismantle and investigate the engine. The right hand engine was disassembled in accordance with the established laid down procedures.
2.7
The Technical Report submitted by the Russian Investigation Board concluded that the thermocouple wiring harness was exposed to high temperatures exceeding the normal operating range, causing deformation of thermocouples 1 and 4 and destruction of the gas generator and power turbine blades due to overheating and when the engine subsequent surged.
2.8
It is reasonably to suggest that a disruption and destruction in the turbine section caused a back pressure in the combustion chamber resulting in a reverse flow of gases and subsequent stall of the compressor as was evident by the loud bang and high frequency vibration high turbine temperature that were experienced.
2.9
Although the crew was properly licensed on the type helicopter, the placards and audible warning on the helicopter were only in Russia that the crew members could not read or understand the audible warnings.
3.
CONCLUSION
3.1
Findings
3.1.1 The crew was properly licensed to conduct the fire fighting operation. 3.1.2 The crew members were all English-speaking and thus could not understand the audible warnings that were in Russian. The placards on the aircraft were also in Russian. 3.1.3 The AMO maintenance personnel were the holders AME licences that were issued in Russia without South African validations. 3.1.4 The last 100 hours AMS maintenance inspection was carried out and certified on 15 May 2006 at a total of 4 845.70 airframe hours. Maintenance records showed that the maintenance and scheduled inspections were carried out in accordance with the scheduled inspection program. 3.1.5 The right-hand engine failed due to destruction and overheating of the gas generator and power turbine of the engine. 3.1.6 The left-hand engine augmentation power RPM increased automatically by 0.8% when the right-hand engine failed. CA 12-12a
23 FEBRUARY 2006
Page 17 of 42
3.1.7 The flight engineer shut down the left-hand engine as the helicopter started yawing to the left, but the helicopter was too low above the water to recover successfully. 3.1.8 All deformation and failure of the main rotor blades, tail rotor blades and drive shaft was caused during the accident sequence. 3.1.9 The time from when the right-hand engine failed until the helicopter impacted with the water was approximately 5 seconds. 3.1.10 The helicopter, with both engines still attached to the airframe, was transported to Russia for further investigation by the Russian authorities. The Russian authorities concluded that the failure of the right-hand engine was as a result of destruction of the gas generator and power turbine caused by an overheating condition and subsequent surge.
3.2
Probable Cause/s
3.2.1 Failure of the right-hand engine turbine section caused back pressure in the combustion chamber, reverse flow of the gases and the compressor to stall, which was evident by a loud bang and a high-frequency vibration. Contributory factor The helicopter was too low above the ground surface to recover even though the lefthand engine gained augmentation power and there was an increase in the left-hand engine power and main rotor RPM.
4.
SAFETY RECOMMENDATIONS
4.1.1 It is recommended that the Regulator makes sure that all placards are in English for all SA registered aircraft. 4.1.2 It is recommended that the Regulator ensures that the manufacturer and/or operators have the capability to download the flight recorder (CVR) and transfer data to any usable form of recording, such as an audible disc.
5.
APPENDICES
5.1
Appendix 1 BAE report on the GPS
5.2
Appendix 2 Report on the right-hand engine submitted by the Russian authorities
CA 12-12a
23 FEBRUARY 2006
Page 18 of 42
Compiled by : Frans De Bryn
Date:……………………..
For: Director of Civil Aviation
Investigator-in-charge: ……………
Date: …………………………..
Co-investigator: …………..…………
Date: ……………….…………
CA 12-12a
23 FEBRUARY 2006
Page 19 of 42
Appendix 1
CA 12-12a
23 FEBRUARY 2006
Page 20 of 42
CA 12-12a
23 FEBRUARY 2006
Page 21 of 42
CA 12-12a
23 FEBRUARY 2006
Page 22 of 42
CA 12-12a
23 FEBRUARY 2006
Page 23 of 42
CA 12-12a
23 FEBRUARY 2006
Page 24 of 42
CA 12-12a
23 FEBRUARY 2006
Page 25 of 42
CA 12-12a
23 FEBRUARY 2006
Page 26 of 42
CA 12-12a
23 FEBRUARY 2006
Page 27 of 42
CA 12-12a
23 FEBRUARY 2006
Page 28 of 42
CA 12-12a
23 FEBRUARY 2006
Page 29 of 42
CA 12-12a
23 FEBRUARY 2006
Page 30 of 42
CA 12-12a
23 FEBRUARY 2006
Page 31 of 42
CA 12-12a
23 FEBRUARY 2006
Page 32 of 42
CA 12-12a
23 FEBRUARY 2006
Page 33 of 42
CA 12-12a
23 FEBRUARY 2006
Page 34 of 42
CA 12-12a
23 FEBRUARY 2006
Page 35 of 42
CA 12-12a
23 FEBRUARY 2006
Page 36 of 42
CA 12-12a
23 FEBRUARY 2006
Page 37 of 42
Appendix 2
CA 12-12a
23 FEBRUARY 2006
Page 38 of 42
CA 12-12a
23 FEBRUARY 2006
Page 39 of 42
CA 12-12a
23 FEBRUARY 2006
Page 40 of 42
CA 12-12a
23 FEBRUARY 2006
Page 41 of 42
CA 12-12a
23 FEBRUARY 2006
Page 42 of 42
