ASN Wikibase Occurrence # 291596
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| Date: | Thursday 30 November 2006 |
| Time: | 08:50 LT |
| Type: |  Piper PA-46-500TP |
| Owner/operator: | Twin Landfill Corporation |
| Registration: | N804JH |
| MSN: | 4697044 |
| Year of manufacture: | 2001 |
| Total airframe hrs: | 595 hours |
| Engine model: | Pratt & Whitney Canada PT6-42A |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Steamboat Springs, Colorado -
 United States of America
|
| Phase: | Unknown |
| Nature: | Private |
| Departure airport: | STEAMBOAT SPRIN, CO (SBS |
| CANON CITY, CO (1V6) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During takeoff, the pilot applied power to the engine, and the takeoff roll was smooth. The pilot noted that the runway centerline was somewhat obscured by snow and the airplane drifted slightly to the right of centerline. As the airplane accelerated to approximately 50 to 60 knots (1/3 down the runway), the airplane 'suddenly turned hard to the left and started to skid,†according to the pilot. The pilot immediately reduced power to idle and did not apply brakes or reverse thrust. Subsequently, the airplane departed the left side of the runway. After repairs were completed from a previous incident, the accident airplane was equipped with a supplemental type certificate (STC) engine mount that eliminated the need for repetitive inspections required by the airframe manufacturer's service bulletins (SBs). Following a number of cracked engine mounts and nose gear failures, several Piper SBs were issued and the original engine mount was redesigned. The redesign process included finite element model analysis and other testing programs. These design tools were not incorporated in the original mount design. During a postaccident examination of the original engine mount and the STC engine mount, investigators found that there was compliance (flexibility) in the engine mount actuator attach feet structure (in both versions), which sometimes resulted in cracks in the engine mount at the actuator feet. Although the STC version reduced the likelihood of fatigue cracking in the mount, compliance remained. The NTSB's investigation determined that compliance could be exacerbated at some speeds, resulting in a high shimmying effect, and a subsequent uncommanded left or right turn of the nosewheel during takeoff or landing. The new engine mount, which the manufacturer subsequently replaced under warranty on all PA-46-500TP airplanes, incorporates a heavy-duty, one-piece design at the actuator attach point, eliminating the original two-piece design, which was produced in two-weld and one-weld versions. The new one-piece design provides a less compliant structure, which prevents relative motion between the two feet in the original engine mount design. Subsequent to this investigation, evidence was received of bulkhead damage immediately behind the engine mount found on a PA-46-310P. The accident airplane was reexamined in 2008, and similar firewall damage was found. The mechanical damage and marks were consistent with the engine mount contacting the bulkhead periodically before the accident.
Probable Cause: The inadequate design of the engine mount, which caused an uncommanded left turn, loss of directional control, and impact with snow-covered terrain. Contributing to the accident was the low nose gear tire pressure.
Accident investigation:
 |
|
Sources:
NTSB DEN07LA030
History of this aircraft
Other occurrences involving this aircraft
| 1 July 2005 | N804JH | 0 | Canon City, Colorado | |
sub |
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 07-Oct-2022 16:40 | ASN Update Bot | Added |
Corrections or additions? ... Edit this accident description
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