ASN Wikibase Occurrence # 42442
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Date: | Friday 4 October 1996 |
Time: | 13:15 LT |
Type: | Boeing Vertol 107-II (CH-46A) |
Owner/operator: | Columbia Helicopters, Inc. |
Registration: | N196CH |
MSN: | 407 |
Year of manufacture: | 1965 |
Total airframe hrs: | 7075 hours |
Engine model: | GE T58-140-1A |
Fatalities: | Fatalities: 3 / Occupants: 3 |
Aircraft damage: | Destroyed |
Category: | Accident |
Location: | Canby, OR -
United States of America
|
Phase: | En route |
Nature: | Unknown |
Departure airport: | Aurora, OR (3S2) |
Destination airport: | |
Investigating agency: | NTSB |
Confidence Rating: | Accident investigation report completed and information captured |
Narrative:The Boeing Model BV-107-II departed on a maintenance check flight with 1.4 hrs total flight time after conversion from a Model HKP-4 per FAA Project #TDO639NY-R. About 37 min later, witnesses saw the rotorcraft moving erratically & tumbling out of control. Postcrash exam of the rotorcraft's flight control system revealed a disconnect between the lower bearing end of the aft directional and lateral control pushrod & the inboard clevis of the forward mixing unit section bellcrank. A bolt, consistent with hardware for that connection, was found in the control closet area. An improper part (collective bellcrank, PN 107C2606-8) was found in place of the required lateral bellcrank (PN 107C2606-9). Clevis width of the -8 part was slightly larger than the -9 part; thus, the clevis bolt was not long enough to allow a cotter pin to be properly installed through the nut & bolt with the required washers (2 thick & 1 thin) installed. To compensate (allow for installation of the cotter pin), 2 thin washers were used in place of the 2 thick and 1 thin washers. Metallurgical exam of the bolt revealed evidence that a nut had been applied to the threaded end, but there was no evidence that a cotter pin had been inserted. No pre-accident engine malfunction or crew impairment was evident.
Probable Cause: failure of maintenance personnel to install a cotter pin in a clevis bolt in the flight control system, which resulted in the aft directional and lateral control output pushrod to become disconnected from a bellcrank in the forward portion of the first stage mixing unit. A factor relating to the accident was the use of an improper bellcrank, which was wider in the clevis area.
Accident investigation:
|
| |
Investigating agency: | NTSB |
Report number: | SEA97FA001 |
Status: | Investigation completed |
Duration: | 1 year |
Download report: | Final report |
|
Sources:
NTSB SEA97FA001
Location
Revision history:
Date/time | Contributor | Updates |
24-Oct-2008 10:30 |
ASN archive |
Added |
10-Jan-2011 07:18 |
TB |
Updated [Time, Aircraft type, Other fatalities, Nature, Source] |
21-Dec-2016 19:24 |
ASN Update Bot |
Updated [Time, Damage, Category, Investigating agency] |
08-Apr-2024 18:46 |
ASN Update Bot |
Updated [Time, Operator, Other fatalities, Nature, Source, Narrative, Category, Accident report] |
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