ASN Wikibase Occurrence # 30994
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| Date: | Saturday 7 March 1998 |
| Time: | 10:56 LT |
| Type: |  Bell UH-1B |
| Owner/operator: | Cantrell Helicopters |
| Registration: | N204DR |
| MSN: | 62-1881 |
| Year of manufacture: | 1962 |
| Engine model: | Lycoming T53L-11 |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Hollister, California -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Agricultural |
| Departure airport: | , CA (307) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot initiated a right turn, then he felt and heard a thump. He lowered the collective and attempted to straighten from the turn. He felt a strong vibration and the nose of the aircraft pitched down. A ground crewman who witnessed the accident reported that while the helicopter was about 35 feet agl, he saw a large piece of the tail and a rotor blade fly off the ship, followed by the tail rotor hub assembly, the remaining blade, and the 90-degree gearbox. The helicopter began a 360-degree right spiral, made 2 1/2 rotations, and then impacted the ground in a 30-degree nose-down attitude. He further noted that the engine still seemed to be producing about 60 percent power. The tail and tail rotor gearbox was found about 125 feet from the fuselage. Metallurgical examination of the vertical tail fin, tail rotor gearbox, and tail rotor blades disclosed an area of chafing which wore through the vertical fin's spar and initiated a fatigue crack. The fatigue crack initiated in an area where the vertical fin driveshaft cover fastened on the left side of the aircraft near the upper end. Chafing had occurred between the cover and the spar, wearing away the spar. According to Bell, the UH-1B requires a daily inspection to visually check the area of the upper vertical fin, per the Aviation Unit Technical Manual, where the fatigue cracking occurred.
Probable Cause: The failure of the maintenance personnel to recognize and repair the chafed area of the tail rotor driveshaft, which resulted in an in-flight separation of the tail fin and hub assembly.
Accident investigation:
 |
|
Sources:
NTSB LAX98LA108
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Sep-2008 01:00 | ASN archive | Added |
| 31-Oct-2011 14:26 | Dr. John Smith | Updated [Time, Total fatalities, Total occupants, Other fatalities, Location, Country, Phase, Nature, Departure airport, Destination airport, Source, Damage, Narrative] |
| 07-Apr-2024 14:22 | ASN Update Bot | Updated [Time, Cn, Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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