ASN Wikibase Occurrence # 153673
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| Date: | Sunday 16 November 2003 |
| Time: | 10:35 |
| Type: |  Bell 407 |
| Owner/operator: | Petroleum Helicopters (PHI) |
| Registration: | N405PH |
| MSN: | 53207 |
| Year of manufacture: | 1997 |
| Total airframe hrs: | 4606 hours |
| Engine model: | Allison 250-C47B |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Minor |
| Category: | Accident |
| Location: | Eugene Island 27, Gulf of Mexico -
 United States of America
|
| Phase: | Take off |
| Nature: | Offshore |
| Departure airport: | Eugene Island 27, Gulf of Mexico |
| EI 63 | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter, which had a FADEC controlled turboshaft engine installed, experienced a loss of engine power after take off from an offshore platform in the Gulf of Mexico. The 10,000-hour commercial rated helicopter pilot, reported that the helicopter "cleared" the platform deck and entered translational lift when "it lurched violently to the left and started a rapid descent." The pilot then lowered the collective and dropped the nose to avoid striking the platform. He recalled hearing a "screaming or screeching type of sound" as the helicopter descended, and was not able to maintain main rotor RPM. The helicopter landed into the water, and rolled to the right. After the occupants evacuated, the helicopter submerged 30 feet under the surface. The skid mounted float system was not activated, although the pilot stated that the floats were "armed" and that he attempted to deploy the floats while in the autorotation, via the float activation button that was mounted on the collective. The float activation button was located within a circular ring that was mounted on the pilot's collective. Download of the Incident Recorder (IR) of the ECU showed that the IR was first triggered by a droop in rotor RPM, followed by a MGT exceedence, power surge, engine flameout, and Ng underspeed in a span of 3.38 seconds. Download of the MGT instrument showed a recorded peak temperature of 953 degrees for 1 second. Teardown examination of the engine revealed a catastrophic failure of the power turbine assembly. Metallurgical examinations by the NTSB and Rolls Royce revealed evidence that the 3rd stage turbine wheel airfoil(s) had failed. A root cause of the failure was not determined, and further testing was conducted at Rolls Royce. As a result of some of the dynamic test results, Rolls Royce issued several Commercial Engine Bulletins (CEBs) regarding inspection of in-service turbine assemblies. Additionally, Bell Helicopter issued an Alert Service Bulletin (ASB), which introduced flight manual revisions to avoid power turbine RPM (Np) steady state operation between 68% and 97%. After examinations of the airframe (fuel system, rotor systems, flight control systems, drive systems, electronic control systems), no anomalies were found other than within the power turbine assembly.
Probable Cause: The loss of engine power due to the failure of the 3rd stage turbine wheel and subsequent catastrophic failure of the turbine assembly.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20040224X00226&key=1
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 02-Mar-2013 13:16 | TB | Added |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 09-Dec-2017 18:05 | ASN Update Bot | Updated [Operator, Departure airport, Destination airport, Source, Narrative] |
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