Pilot Debrief

SCHRODER DAVID LANCAIR IV P near Fulton, NY — 2017-06-01

Final reportCEN17IA233
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Date
2017-06-01
Location
Fulton, NY, USA
Airport
FZY
Aircraft
SCHRODER DAVID LANCAIR IV P
Registration
N366TF
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

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.

NTSB 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.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Avoiding zero g-force maneuvers could have prevented engine failure.

NTSB coding

  • Loss of engine power (total) · Maneuvering

Evidence available

  • Photos
  • 6 docket documents
View NTSB final reportView NTSB docket

Docket documents6

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