ASN Wikibase Occurrence # 75773
This information is added by users of ASN. Neither ASN nor the Flight Safety Foundation are responsible for the completeness or correctness of this information.
If you feel this information is incomplete or incorrect, you can submit corrected information.
| Date: | Monday 18 September 2000 |
| Time: | 08:15 |
| Type: | VAT/Sikorsky S-55QT Whisper Jet |
| Owner/operator: | Papillon Grand Canyon Helicopters |
| Registration: | N17754 |
| MSN: | V55-398T |
| Total airframe hrs: | 487 hours |
| Engine model: | Honeywell TSE331-10UA-5 |
| Fatalities: | Fatalities: 0 / Occupants: 7 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | 6 km E of Hoover Dam, AZ -
 United States of America
|
| Phase: | En route |
| Nature: | Passenger - Non-Scheduled/charter/Air Taxi |
| Departure airport: | Las Vegas, NV (LAS) |
| Grand Canyon, AZ (GCN) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter was being operated as a sightseeing flight to the Grand Canyon. The pilot reported that during cruise flight the rotor and engine noise suddenly decreased and the helicopter began a descent. During the ensuing forced landing, the helicopter landed hard. The helicopter was fabricated from an ex-military remanufactured and modified Sikorsky S-55 (UH-19D). The original radial reciprocating engine had been replaced with a Garrett Gas Turbine TPE 331 modified to a TSE 331 IOUA 511SW. It had a 6,000-hour time between overhaul. According to maintenance records dating back to July 3, 1985, the accident engine P-54083 operated in more than one Fairchild SA226 airplane in Australia, and several rotary wing S-55 aircraft during their certification in the United States. Following the accident the engine was shipped to the modifier for functional testing in a cell. The engine started and idled normally. Increasing the rpm to the certified operating specification of 101.5 percent revealed no abnormal conditions. The test propeller was moved from the start locks and increasing torque load was applied. As the torque was increased the engine responded normally until approximately 60 percent torque when the indicated engine rpm rapidly decreased and an emergency shutdown was initiated. The process was repeated through 12 cycles, during which the indicated rpm began a sudden rapid decrease when torque was increased. Test cell troubleshooting failed to identify or correct this condition. During manual rotation of the propeller following the final cycle some "slipping" was noted between the output shaft and the main rotating group. Subsequent examination of the gearbox revealed disengagement of the sun and bull gear assembly. Examination revealed fretting damage to the retaining nut and mating surfaces related to loss of specified torque. Visual examination of the sun and bull gears revealed severe damage to the mating splines of both gears. About 9 months before the accident the original manufacturer issued a service bulletin providing for the replacement of the affected components; the engine modifier recommended replacement of the components prior to further operation. Examination of past oil analysis samplings revealed increases of iron and magnesium over a period of time, with analysis report comments of "Alert" and "Iron Appears High."
Probable Cause: The failure of maintenance personnel to accomplish a service bulletin addressing the potential failure of engine drive gears, and the ignored oil analysis testing results that indicated an impending internal engine failure that subsequently resulted in the loss of engine drive to the main rotor during flight.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20001212X21998&key=1
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 19-Jul-2010 03:19 | TB | Added |
| 19-Jul-2010 06:59 | TB | Updated [Registration] |
| 19-Jul-2010 08:05 | TB | Updated [Departure airport, Destination airport] |
| 19-Jul-2010 08:42 | TB | Updated [Departure airport] |
| 19-Jul-2010 11:03 | TB | Updated [Aircraft type] |
| 21-Dec-2016 19:25 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 24-Nov-2017 09:16 | TB | Updated [Aircraft type, Source, Damage, Narrative] |
| 12-Dec-2017 19:09 | ASN Update Bot | Updated [Operator, Departure airport, Destination airport, Source, Damage, Narrative] |
| 11-Oct-2021 19:01 | harro | Updated [Narrative, Accident report] |
Corrections or additions? ... Edit this accident description
The Aviation Safety Network is an exclusive service provided by:
Quick Links:
| ASN Home | Send Correction / Feedback |
| FSF Home | Disclaimer | Copyright |
| Contact Us | Privacy Policy |
| Press / Media |
CONNECT WITH US:
©2024 Flight Safety Foundation