ASN Wikibase Occurrence # 75246
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| Date: | Monday 21 June 2010 |
| Time: | 12:57 |
| Type: |  Cessna T210L Turbo Centurion |
| Owner/operator: | U.S. Forest Service |
| Registration: | N30266 |
| MSN: | 210-59901 |
| Total airframe hrs: | 5000 hours |
| Engine model: | Continental TSIO-520-H |
| Fatalities: | Fatalities: 3 / Occupants: 3 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | near Lock Haven Airport, PA -
 United States of America
|
| Phase: | Approach |
| Nature: | Survey |
| Departure airport: | Clarion, PA (AQX) |
| Lock Haven-W T Piper Memorial Airport, PA (LHV/KLHV) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The aerial observation flight was conducted by a 14 CFR Part 135 certificated on-demand air carrier under contract to the U.S. Forest Service. As the flight neared its destination airport, the pilot reported via the airport's common traffic advisory frequency his intent to land. Witnesses reported that, as the airplane overflew them on approach to the airport, it appeared to be in distress, trailing black smoke with the engine "sputtering." The airplane subsequently impacted a light stanchion about 1,300 feet short of the intended landing runway. Location was East Church Street, near the airport. Before coming to rest, the airplane struck a house and several parked cars, and it was nearly consumed during a post-impact fire. Postaccident examination revealed a catastrophic failure of the airplane's engine, which originated with a fatigue failure of the number 2 cylinder exhaust valve. The fatigue failure was likely due to abnormal loading associated with excessive valve-to-valve guide clearance resulting from valve guide wear. Typically, valve guide wear results from either overall elevated engine operating temperatures or individually elevated valve temperatures due to improper valve seating. The normal wear pattern observed on the number 2 exhaust valve seat suggested that improper valve seating was not an issue in this case.
Significant exhaust valve guide wear was observed on all cylinders, with the valve guides of the generally cooler cylinders near the front of the engine showing less wear than those of the generally hotter cylinders near the rear of the engine. This overall pattern suggested a persistent elevated temperature problem, which could have resulted from either improper engine operation or an undiagnosed maintenance issue.
The investigation revealed that, when performing engine cylinder differential pressure tests during required routine inspections of the airplane’s engine, the contract operator utilized gauges that had not been calibrated since their purchase and did not perform the tests in accordance with the engine manufacturer's recommendations. Also, the engine manufacturer recommended that cylinder borescope inspections be accomplished in conjunction with the differential pressure tests, and there were no notations in the engine maintenance records of any visual borescope inspections of the interior of the cylinders. Further, there was no notation in the records that the fuel injection system had been inspected and adjusted per the engine manufacturer’s recommendations. If properly performed, differential pressure tests and borescope inspections may have detected valve guide wear and prevented the exhaust valve failure, and fuel injection system inspections may have detected and corrected incorrect adjustment of the engine fuel system, which can result in elevated engine cylinder temperatures and lead to valve guide wear. These and other instances of non-compliance with manufacturer service recommendations discovered during the investigation indicated that the contract operator was not maintaining the airplane in a manner consistent with its "Operator's Manual," which dictated that inspections of time-limited components were to be conducted in accordance with the applicable manufacturers' recommendations.
Probable Cause: The total loss of engine power resulting from the fatigue failure of the engine's number 2 cylinder exhaust valve. The fatigue failure was due to valve guide wear that led to excessive clearance between the valve and valve guide. Contributing to the accident was the contract operator’s lack of compliance with its own maintenance procedures, which, if followed, would have prevented the accident.
Accident investigation:
 |
|
Sources:
NTSB
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 22-Jun-2010 01:26 | RobertMB | Added |
| 22-Jun-2010 22:12 | RobertMB | Updated [Registration, Cn, Operator] |
| 23-Jun-2010 11:37 | harro | Updated [Embed code] |
| 21-Dec-2016 19:25 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 26-Nov-2017 17:13 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 01-May-2022 08:45 | Ron Averes | Updated [Operator] |
| 12-Nov-2022 02:43 | Ron Averes | Updated [Operator, Location, Destination airport, Narrative] |
| 30-May-2023 00:38 | Ron Averes | Updated [[Operator, Location, Destination airport, Narrative]] |
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