Cessna T210L N30266

Summary

On 21 June 2010 at about 16:57 local time, a Cessna T210L registered N30266, operated by U.S. Department of Agriculture Forest Service, was involved in an accident near Lock Haven, Pennsylvania, United States. 3 people were on board and 3 died. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 June 2010 at 16:57

Classification

Accident

Location

Lock Haven, Pennsylvania, United States

Nearest airport

William T. Piper Memorial (LHV)

Coordinates

41.1342, -77.4336

Aircraft

Cessna T210L

Registration

N30266

Category

Airplane

Engines

1

Operator

U.S. Department of Agriculture Forest Service

Operating rule

Public Use

Purpose of flight

Aerial Observation

Phase of flight

Not recorded

Route

Clarion → Lock Haven

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA10GA320

3 people died.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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. 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.

Quoted verbatim from the NTSB record.