Serious incident Lancair IV-P N366TF,
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ASN Wikibase Occurrence # 309953
 
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Date:Thursday 1 June 2017
Time:18:30 LT
Type:Silhouette image of generic LNC4 model; specific model in this crash may look slightly different    
Lancair IV-P
Owner/operator:Private
Registration: N366TF
MSN: LIV-388
Year of manufacture:2000
Total airframe hrs:1146 hours
Engine model:Continental TSIO-550 SER
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: None
Category:Serious incident
Location:Fulton, New York -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Private
Departure airport:Fulton-Oswego County Airport, NY (KFZY)
Destination airport:Fulton-Oswego County Airport, NY (KFZY)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot and a flight instructor planned to conduct an inflight calibration of an angle of attack indicator. Following a zero g-force maneuver, engine oil pressure decreased to 3 psi and engine speed increased to 3,140 rpm. Immediately after the engine overspeed, a total loss of power occurred. The pilot performed a forced landing to the departure airport without further incident.

Examination of the engine revealed one of the two rear crankshaft counterweights (6th order) separated from the crankshaft, with a 6th order counterweight connecting pin lodged in the crankcase between cylinder Nos. 4 and 6. An impression in the No. 1 connecting rod matched the shape of a 6th order counterweight connecting pin. The oil sump contained significant debris, including four counterweight pin retaining snap rings, four counterweight pin retainer plates, and two 6th order counterweight connecting pins. Based on the examination, the lack of oil pressure and subsequent engine rpm overspeed/surge likely caused the separation of the crankshaft counterweight and engine failure.

Probable Cause: The loss of oil pressure and subsequent engine overspeed/surge during a zero g-force maneuver, which resulted in the separation of a crankshaft counterweight and loss of engine power.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN17IA233
Status: Investigation completed
Duration: 1 year and 5 months
Download report: Final report

Sources:

NTSB CEN17IA233

Location

Revision history:

Date/timeContributorUpdates
01-Apr-2023 13:08 ASN Update Bot Added

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