ASN Wikibase Occurrence # 153626
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| Date: | Sunday 16 February 2003 |
| Time: | 12:25 |
| Type: |  Bell 407 |
| Owner/operator: | Houston Helicopters Inc |
| Registration: | N407HH |
| MSN: | 53460 |
| Year of manufacture: | 2000 |
| Total airframe hrs: | 546 hours |
| Engine model: | Allison 250-C47B |
| Fatalities: | Fatalities: 2 / Occupants: 5 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Gulf of Mexico -
 United States of America
|
| Phase: | En route |
| Nature: | Offshore |
| Departure airport: | TeSoro Heliport, TX |
| Matagorda 700 block offshore | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On February 16, 2003, approximately 1225 central standard time, a Bell 407 single-engine helicopter, N407HH, registered to and operated by Houston Helicopters, Inc., of Pearland, Texas, executed an emergency landing into open ocean water in the Gulf of Mexico following a loss of engine power. The pilot and his four passengers survived the initial landing, however, the pilot and one passenger later drowned after egress from the helicopter. The remaining three passengers received serious injuries. Visual meteorological conditions prevailed, and a company visual flight rules (VFR) flight plan was filed for the Title 14 Code of federal Regulations Part 135 on-demand air taxi flight. Approximately 1210, the helicopter departed Harbor Island (TeSoro Heliport), Ingleside, Texas, for a 26.1 nautical mile flight to offshore platform, Ensco Rig 84 (Matagorda 700 block offshore), with an estimated time of arrival of 1230.
The helicopter, flown by 19,000-hour pilot and transporting 4 passengers to an offshore oil platform, experienced a catastrophic engine failure and autorotated into open ocean water in the Gulf Of Mexico. Within a few seconds after landing on the water, the helicopter rolled inverted, the pilot and passengers exited, inflated their personal life vests, and waited for rescue. The pilot and one of the passengers drowned prior to rescue personnel arriving about 2 hours after the accident. Surviving passenger statements indicated that they were not aware of an emergency lift raft on-board the helicopter, and that the skid-mounted emergency float system was not inflated prior to landing. Rescue personnel reported high wind and rough seas in the area of the accident. Examination of the wreckage revealed that the float "ARM" switch was found in the disarmed position and its cover closed. The skid-mounted emergency floats were found inside their protective bags. The float system tested functional, and no anomalies were found during airframe component examinations. Download data from the ECU showed that engine performance prior to the loss of power was normal and the engine was operating in a steady state condition prior to the initial deterioration of NG. Detailed inspection of the engine revealed progressive turbine wheel damage throughout the power turbine. The damage varied from approximately 95% of the airfoil material missing on the 1st stage wheel to approximately 10% of the material missing on the 4th stage wheel. The damage observed in the gas producer turbine section was consistent with the separation of one or more of the first stage wheel airfoils. Mostly all of the fracture surfaces were obscured, typical of elevated turbine temperatures (according to the manufacturer, in excess of turbine and material limits). All 4 turbine wheels had evidence of solutioning and incipient melting was observed at the tips of the airfoil remnants. Fracture surfaces of the 1st stage wheel airfoils did not reveal the presence of fatigue. Detailed metallurgical examination revealed the presence of sulfides on the 1st and 2nd stage turbine wheel surfaces. According to the manufacturer, the presence of sulfides is evidence that sulfidation has occurred. Damage on the concave surface adjacent to the fractures near the leading edges of the airfoils was found consistent with type 1 hot corrosion (sulfidation) damage. Examination of radial cracks at the trailing edges of the airfoils revealed heavy oxidation consistent with thermal fatigue. According to Rolls Royce, that "thermal fatigue cracking at the airfoil base is not uncommon." Evidence of EPS 10649 (S1 Aluminide, which is a protective coating applied to the turbine wheel during manufacturing), was confirmed adjacent to the corrosive damage found on the wheels.
Probable Cause: The catastrophic failure of the engine resulting from 1st stage turbine wheel blade failure due to type 1 hot corrosion (sulfidation). Contributing factors were the pilot's failure to brief the passengers on emergency safety equipment (life raft), the pilot's failure to deploy the skid-mounted emergency float system during the autorotation, the high wind conditions, and rough sea state.
Accident investigation:
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|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20030221X00247&key=1
Location
Images:
Photos: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-Mar-2013 11:00 | TB | Added |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 08-Dec-2017 18:03 | ASN Update Bot | Updated [Operator, Departure airport, Destination airport, Source, Narrative] |
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