ASN Wikibase Occurrence # 30750
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| Date: | Friday 26 February 1999 |
| Time: | 10:10 LT |
| Type: |  Eurocopter EC 120B Colibri |
| Owner/operator: | American Eurocopter Corp. |
| Registration: | N122TH |
| MSN: | 1017 |
| Year of manufacture: | 1998 |
| Total airframe hrs: | 22 hours |
| Engine model: | Turbomeca ARRIUS 2F |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | near Springtown, TX -
 United States of America
|
| Phase: | En route |
| Nature: | Executive |
| Departure airport: | Grand Prairie, TX (GPM |
| Amarillo, TX (KTDW) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While at cruise altitude, the helicopter's engine began to surge. The pilot initiated an autorotation to an open field. During the downwind forced landing, the skids dug into the ground, and the helicopter nosed over and came to rest on its left side. An examination of the engine revealed that the P3 air pipe, which supplies air to the fuel control, was broken close to the fitting on the combustion chamber casing. Examination of the P3 pipe revealed that its fracture was 'consecutive to the propagation of a fatigue fissure,' as a result of the pipe being 'subjected to an excessive vibratory excitation.' Engine vibration tests were conducted and two main excitation sources were identified. The two sources were the starter-generator and the breather gear assembly. The proposed solution to correct for this vibration consists of fitting an attachment clamp at mid-length of the P3 pipe, 'which moves the natural frequencies out of engine power ratings.'
Probable Cause: The improper touchdown executed by the pilot. Factors were the tail wind condition, and the manufacturer's inadequate design of the P3 pipe supports, which resulted in a fatigue fracture of the P3 pipe.
Accident investigation:
 |
|
Sources:
NTSB FTW99LA085
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Sep-2008 01:00 | ASN archive | Added |
| 25-Nov-2009 04:52 | harro | Updated |
| 09-Mar-2013 12:58 | TB | Updated [Aircraft type, Location, Source, Narrative] |
| 26-Nov-2017 10:00 | ASN Update Bot | Updated [Operator, Nature, Departure airport, Destination airport, Source, Narrative] |
| 08-Apr-2024 09:19 | ASN Update Bot | Updated [Time, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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