ASN Wikibase Occurrence # 356334
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| Date: | Thursday 9 January 1997 |
| Time: | 15:05 LT |
| Type: |  Beechcraft N35 |
| Owner/operator: | Private |
| Registration: | N7HB |
| MSN: | D-6750 |
| Total airframe hrs: | 3883 hours |
| Engine model: | Continental IO-470 |
| Fatalities: | Fatalities: 0 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Holbrook, AZ -
 United States of America
|
| Phase: | Take off |
| Nature: | Private |
| Departure airport: | (P14) |
| Flagstaff, AZ (KFLG) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
Moments after lift-off, the propeller separated, & the aircraft (acft) veered off the runway, contacted soft soil, & nosed over. Investigation revealed the propeller hub failed forward of the attachment flange, around the circumference of the hub. The pilot said he had performed a thorough preflight & run-up, & found no discrepancies. Metallurgical exam of the hub revealed crack arrest marks, typical of fatigue, emanating from the 4th thread root on the aft piece of the hub. The crack was estimated to be several inches long before failure occurred. Review of records disclosed that McCauley Service Bulletin 179A, McCauley Service Letter 1989-5, & Airworthiness Directive (AD) 89-26-08 had not been complied with during the previous 5 annual inspections. These referenced propellers which should have incorporated an oil-filled configuration with red dye that would become visible once a hub had begun to crack. The AD cited McCauley '2A36C23/84B-0' Constant Speed Propellers. Both McCauley & the FAA engineering directorate, which wrote the AD, reported the intent was to capture all 2A36C23 hubs regardless of blade models. The hub on the accident acft was a McCauley 2A36C23-P-E, with blade Models S-84B-0 installed (rather than blade Models 84B-0). Unanimous response from mechanics & IA's, who worked on the acft during the previous 5 annuals inspections, was that the AD was not applicable since the propeller was not a '2A36C23/84B-0' as stated in the AD.
Probable Cause: fatigue failure of the propeller hub, which resulted in separation of the propeller assembly and reduction of aircraft control. Also causal was: the resultant lack of compliance with Airworthiness Directive (AD) 89-26-08, due to ambiguous and unclear wording of the AD as issued by the FAA. Factors relating to the accident were: non-compliance with McCauley Service Bulletin 179A and McCauley Service Letter 1989-5, and an encounter with soft terrain during the aborted takeoff.
Accident investigation:
 |
|
Sources:
NTSB LAX97LA084
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 12-Mar-2024 21:30 | ASN Update Bot | Added |
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