Transportation Safety Board of Canada
www.bst-tsb.gc.ca
AVIATION Reports - 2005 - A05F0025
Appendices
- Appendix A - Previous AS 350 Loss-of-Control Occurrences
- Appendix B - List of Laboratory Reports
- Appendix C - Glossary
Appendix A - Previous AS 350 Loss-of-Control Occurrences
November 1990 - Kahului, Hawaii, United States
The pilot of an AS 350 B (N350CB) crashed while hover taxiing at night when he inadvertently operated the hydraulic test (HYD TEST) switch instead of the landing light switch adjacent to it. The pilot was unable to prevent the helicopter from striking the ground. (National Transportation Safety Board [NTSB] report LAX91LA034)
October 1991 - Scottsdale, Arizona, United States
The pilot of an AS 350 B (N9001S) crashed while attempting a landing during loss-of-hydraulics training with a qualified flight instructor on board. The pilots were unable to move the flight controls and prevent the helicopter from striking the ground. The investigation did not identify a cause for the loss of control, but noted that it was the second of such an event. (NTSB report LAX92FA025)
July 1993 - West Plains, Missouri, United States
The pilot of an AS 350 BA (N350BA) appeared to suddenly lose control as he attempted to land in an open field. The investigation did not identify a cause for the loss of control. (NTSB report CHI93FA249)
October 1994 - Whitianga, New Zealand
An AS 350 B (ZK-HZP) flew into the sea after encountering hydraulic jack stall at low altitude; two of the six occupants were fatally injured. Jack stall - also referred to as servo transparency by Eurocopter - is a known characteristic of this hydraulic servo. In summary, it occurs when the helicopter is being manoeuvred and the rotor is loaded to the point where the servos can no longer overcome the associated aerodynamic forces, resulting in feedback through the flight controls, which may become unmanageable. The investigation found no indication of hydraulic system or flight control malfunction. (Transport Accident Investigation Commission of New Zealand report 94-022)
May 1995 - Tampa, Florida, United States
The pilot of an AS 350 B (N35AH) experienced intermittent hydraulic system malfunction, which locked the flight controls. He was unable to control the helicopter and crashed onto the terrain. The investigation revealed remarkable contamination in the hydraulic system. (NTSB report MIA95LA131)
December 1998 - San Angelo, Texas, United States
The qualified flight instructor of an AS 350 BA (N911MV) rolled over during take-off, following loss-of-hydraulics training with a licensed pilot. The event was characteristic of a hydraulic actuator hard-over and the pilot was unable to prevent the helicopter from rolling left and striking the ground. The investigation did not identify a cause for the accident. (NTSB report FTW99LA048)
August 1999 - Islip, New York, United States
The pilot of an AS 350 (N211PD) crashed while hovering during loss-of-hydraulics training with a qualified flight instructor on board. The pilot was unable to maintain control of the helicopter, and both pilots together could not prevent the helicopter from rolling over to the left and striking the ground. Subsequent bench-testing of the servo actuators revealed functional anomalies in several specification tests. (NTSB report IAD99GA056)
March 2000 - Van Nuys, California, United States
The pilot of an AS 350 B (N500WC) crashed while attempting a hover landing following an in-flight loss of hydraulic pressure. The pilot lost directional control and could not prevent the helicopter from striking the ground. The investigation found that the hydraulic pump bearing and drive belt had failed and caused the hydraulic failure. The report also noted that the small physical stature and strength of the pilot were contributing factors, as was the inadequate emergency training. (NTSB report LAX00FA136)
May 2000 - Blanding, Utah, United States
During level flight, an AS 350 B (C-GPTT) was seen to enter into an excessively steep left turn before it plunged nose-down into the terrain. Such in-flight attitudes are characteristic of loss of control. The investigation found evidence of engine operation exceeding temperature limits and concluded that abrupt in-flight manoeuvring was the cause of the loss of control. (NTSB report DEN00FA084)
May 2000 - Mesa, Arizona, United States
The pilot of an AS 350 B2 (N851HW) crashed while attempting a running landing during loss-of-hydraulics training with a qualified flight instructor on board. The pilot reported serious cyclic control difficulties immediately before the touchdown, and despite the hydraulic system being re-engaged using the collective hydraulic cut-off (HYD CUT OFF) switch, the binding was not eliminated. The investigation did not identify a technical cause for the loss of control. (NTSB report LAX00LA195)
May 2000 - Patterson, Louisiana, United States
The pilot of an AS 350 B2 (N350JG) experienced a mechanical failure in the tail rotor system. The pilot carried out the procedures for tail rotor failure in flight, including pressing the HYD TEST switch for five seconds. To silence the warning horn, he then pressed the warning horn mute switch, which is adjacent to the HYD TEST switch. During touchdown, the pilot lost control and the helicopter rolled over. Examination of the cockpit revealed that the HYD TEST switch was still depressed, but the horn switch was not. The investigation determined that the pilot inadvertently pressed the HYD TEST switch instead of the adjacent mute switch, and the accumulators exhausted hydraulic pressure just as the pilot was touching down. (NTSB report FTW00LA153)
January 2001 - Enniskillen, Northern Ireland
During flight in marginal visual weather conditions, an AS 350 B2 (G-OROZ) was seen to descend nose-down in a right turn and strike the terrain. At the same time, the warning horn was sounding. The HYD TEST switch was found in the TEST position. The investigation concluded that the pilot lost control of the helicopter as a result of disorientation in deteriorating meteorological conditions. The reasons for the warning horn sounding and the HYD TEST switch being in the TEST position were not determined. (Air Accidents Investigation Branch [AAIB] report EW/C2001/1/2)
May 2001 - Houston, Texas, United States
The pilot of an AS 350 B2 (N311TV) experienced a hydraulic system failure while approaching a heli-pad at about 20 feet above ground level (agl). The helicopter struck the ground and rolled over. The hydraulic warning light did illuminate; however, the warning horn did not sound. The HYD CUT OFF switch on the collective lever was found in the CUT OFF position, and the switch guard was broken. The investigation found no mechanical anomaly with the hydraulic pump or regulator. The report concluded that the pilot inadvertently activated the HYD CUT OFF switch and lost control during approach. (NTSB report FTW01LA121)
October 2001 - Roswell, New Mexico
The pilot of an AS 350 B2 (N111DT) experienced cyclic control lock in hover flight at about 200 feet agl. The helicopter descended and struck the ground and two of the four persons on board were fatally injured. The pilot recalled no difficulty with the collective lever, nor did either the warning horn sound or the warning lights illuminate. The investigation did not determine a cause. (NTSB report FTW02FA017)
April 2002 - Valdez, Alaska, United States
The pilot of an AS 350 B2 (N917JT) experienced a hydraulic system failure during cruise flight. During the hover landing, the pilot was unable to maintain control and the helicopter rolled to the left and struck the terrain. The investigation determined that the hydraulic pump drive-belt broke in flight, causing the loss of hydraulic system pressure. (NTSB report ANC02FA029)
September 2002 - Peach Springs, Arizona, United States
The pilot of an AS 350 BA (N357NT) experienced a hydraulic system failure during cruise flight. During the landing, the pilot was unable to maintain directional control and he reduced the throttle. The helicopter landed hard and the tail boom was cut off by the main rotor blades. The investigation did not identify the cause of the hydraulic system failure. (NTSB report LAX02FA281)
January 2003 - Mekatina, Ontario, Canada An AS 350 B2 (C-GOGN) crashed on approach to a landing site following a hydraulic system malfunction, fatally injuring the four occupants. The investigation determined in part that the hydraulic pump drive-belt broke in flight, precipitating a loss of hydraulic system pressure, and that the pilot was unable to maintain control of the helicopter. The investigation also found that the flight control forces encountered by the pilot may have been too extreme to overcome, making it impossible for him to control the helicopter. (TSB report A03O0012)
September 2003 - Grand Canyon, Arizona, United States
An AS 350 BA (N270SH) collided with a canyon wall during descent, fatally injuring all seven occupants. Preliminary information reveals that the pilot had changed/delayed his entry and descent into the canyon for unknown reasons. The weather conditions were suitable for visual flight, and no indications of mechanical defect have been found. The investigation is ongoing and has not determined a cause. (NTSB occurrence LAX03MA292)
November 2003 - Mesa, Arizona, United States
The pilot of an AS 350 B3 (N820NA) reported that he had experienced a hydraulic system failure in flight, and he diverted to the nearest airport. During the approach to landing, the helicopter turned left but the pilot could not control the yaw with right pedal input. The helicopter touched down in a left turn and rolled over. The HYD TEST switch was found in the TEST position. The investigation concluded that the pilot inadvertently operated the HYD TEST switch. (NTSB report LAX04LA035)
December 2003 - Houghton, Norfolk, United Kingdom
During hover just after take-off, the pilot of an AS 350 B (G-EJOC) experienced a rapid stiffening of the flight controls with the hydraulic caution light illuminated, but no warning horn sounding. With difficulty, the pilot landed the helicopter, damaging the tail rotor on some trees. The investigation revealed that the pilot had likely inadvertently selected the HYD TEST switch to TEST instead of selecting the horn switch back on following his pre-flight hydraulic test sequence. He then took off with the HYD TEST switch in TEST and the horn muted. (AAIB report EW/G2003/12/10)
January 2004 - Attawapiskat, Ontario, Canada
The pilot of an AS 350 B (C-GDKD) experienced a serious cyclic control malfunction while in forward flight, without the loss of hydraulic pressure or any warning or indication thereof. The pilot managed to land the helicopter shortly after, without damage or injury. Subsequent remedial action by the operator included replacing the two lateral Dunlop servo actuators. The incident was not formally investigated by the TSB, and because the actuators were not examined by the TSB, no information of their functionality or condition is available. (TSB file number A04O0015)
May 2004 - Brooklyn, New York, United States
An AS 350 BA (N4NY) was destroyed after the pilot lost control while attempting to hover out-of-ground effect following a sudden loss of hydraulic power. During the uncontrolled and severe attitude changes, the helicopter crashed on a rooftop; two of the three occupants were seriously injured. The investigation revealed that the hydraulic pump drive-belt had been installed inside-out and had broken, causing a total loss of hydraulic pressure to the flight controls. While this mechanical verification identified the cause of the loss of hydraulic power, the reason for the loss of control was not determined. The pilot, however, had not correctly identified the hydraulic failure and had received no hydraulic failure training. (NTSB report NYC04FA117)
December 2004 - Apache Junction, Arizona, United States
The pilot of an AS 350 B3 (N971AE) lost control during the approach to a prepared landing site and the helicopter collided with the terrain. The attitude changes immediately before impact are characteristic of a loss of control. One of the three occupants was killed and the others were seriously injured. The investigation is ongoing. (NTSB occurrence LAX05FA053)
March 2005 - Mahdia, Guyana
The pilot of an AS 350 B3 (F-CJTU) experienced a hydraulic malfunction while in forward flight. The cause was found to have been the failure of the splines on the hydraulic pump drive shaft. When the pump stopped, the hydraulic pressure dropped, the warning horn sounded, and the pilot carried out the procedures prescribed in the rotorcraft flight manual (RFM). The pilot was able to control the helicopter without difficulty throughout the flight without hydraulic power, and carried out a running landing, incurring no damage or injury. The helicopter response and the control forces reported by the pilot were manageable and quite similar to the training he had received. (This occurrence was not investigated. The pilot of this helicopter was flying C-GNMJ, the occurrence aircraft.)
January 2006 - Port Hedland, Western Australia, Australia
The pilot of an AS 350 B2 (VH-KVN) was on approach to landing when the warning klaxon sounded and the hydraulic caution light illuminated. The pilot landed the helicopter without further event, and disembarked the two passengers. Inspection of the helicopter and discussions with company maintenance did not reveal any mechanical reason for the warning light or horn, and the pilot boarded the passengers and took off into the hover. There were no indications of abnormal operation or control response and the pilot transitioned into forward flight. Seconds thereafter, the pilot experienced uncommanded left yaw and lateral cyclic forces that he could not counter. The helicopter struck the ground in a right roll attitude and the occupants received minor injuries. The cause for the loss of hydraulic pressure was the failure of the splines on the hydraulic pump drive shaft; the reason for the spline failure was not pursued. The reasons for the continuance of flight after the initial hydraulic malfunction, or for the subsequent loss of control after take-off, were not identified. (Australian Transport Safety Bureau report 200600039)
May 2006 - Goshen, New York, United States
The pilot of an AS 350 BA (C-GGLM) experienced a hydraulic pump failure while in cruise flight. Accordingly, the hydraulic pressure was lost and the pilot carried out the required emergency procedures, electing to perform a running landing in a field. As the helicopter approached the ground, the pilot attempted to slow it to a near-hover condition but was unable to prevent the helicopter from turning. He assessed that he had a flight control malfunction and lowered the collective quickly to descend. The helicopter struck the ground hard, causing substantial damage. There were no injuries. The preliminary investigation revealed a failed hydraulic pump spline and coupling. It was not determined why the pilot lost control. (NTSB report NYC06LA121)
Appendix B - List of Laboratory Reports
The following TSB Engineering Laboratory reports were completed:
- LP 036/2005 - Component Analysis
- LP 123/2005 - Examination of Switches
- LP 128/2005 - Component Examination
These reports are available from the Transportation Safety Board of Canada upon request.
Appendix C - Glossary
| A | ampere |
|---|---|
| AAIB | Air Accidents Investigation Branch |
| AC | Advisory Circular |
| AC | alternating current |
| AD | Airworthiness Directive |
| agl | above ground level |
| AME | aircraft maintenance engineer |
| AN | Airworthiness Notice |
| ASB | Alert Service Bulletin |
| CARs | Canadian Aviation Regulations |
| CFM | complementary flight manual |
| CG | centre of gravity |
| DC | direct current |
| DGAC | Direction Générale de l'Aviation Civile |
| DPDT | double-pole, double-throw |
| EASA | European Aviation Safety Agency |
| ECF | Eurocopter France |
| ELT | emergency locator transmitter |
| FAA | Federal Aviation Administration (United States) |
| FARs | Federal Aviation Regulations (FAR) |
| FMS-7 | flight manual supplement number 7 for Canadian helicopters |
| g | load factor |
| HYD | hydraulic warning light |
| HYD CUT OFF | hydraulic cut-off (switch) |
| HYD TEST | hydraulic test (switch) |
| IAS | indicated airspeed |
| IGE | in-ground effect |
| kg | kilograms |
| km/hr | kilometres per hour |
| kt | knots |
| lb | pounds |
| mm/sec | millimetres per second |
| N | north |
| NTSB | National Transportation Safety Board (United States) |
| PPC | pilot proficiency check |
| RAAF | Royal Australian Air Force |
| RFM | rotorcraft flight manual |
| rpm | revolutions per minute |
| SB | Service Bulletin |
| SDR | service difficulty report |
| SNIA | Société Nationale Industrielle Aérospatiale |
| TBO | time between overhaul |
| TC | Transport Canada |
| TRLC | tail rotor load compensator |
| TSB | Transportation Safety Board of Canada |
| VFR | visual flight rules |
| VMC | visual meteorological conditions |
| VNE | never-exceed speed |
| W | west |
| º | degrees |
| ºC | degrees Celsius |
| ' | minutes |
1. Coordinated universal time minus four hours.
2. See Glossary at Appendix C for all abbreviations and acronyms.
3. The horn for low rpm is also the warning for loss of hydraulic pressure.
4. The three main rotor blades are identified as red, blue, and yellow.
5. The AS 350 B2 may be equipped with either SAMM or Dunlop servo actuators, or both. All four servos installed on C-GNMJ were Dunlop.
6. A latched pushbutton switch retains its selected position until it is pressed again.
7. RFM, Section 3.1, Subsection 7.2, Tail Rotor Control Failure.
8. TC's Emergency Airworthiness Directive CF-2003-15R2.
9. During flight, a helicopter builds up static electricity, which at times can be several thousand volts.
10. Referred to as time between overhaul (TBO).
11. TSB report A03O0012.
12. The control forces were considered marginally acceptable because they were limited to a relatively short duration and occurred at a low airspeed, normally at the end of an approach to landing.
13. Helicopter models previously certificated to an earlier standard and issued a type certificate.
14. Section 723.98, Training Programs, of the CARs.
15. For all Canadian helicopter pilot licence holders, TC requires an individual type endorsement for each helicopter type flown.
16. The switch also has the military part number MS27719-23, which is interchangeable with 12TW1-3.
17. Eurocopter Service Letter 1648-29-03 dated 04 December 2003.