Pilot Debrief

DIAMOND DA 40 near San Carlos, CA — 2008-09-13

Final reportSEA08IA217
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Date
2008-09-13
Location
San Carlos, CA, USA
Aircraft
DIAMOND DA 40
Registration
N419JS
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

The improper assembly of the governor during manufacture.

NTSB narrative

The pilot departed on a local area flight when the engine had higher than normal RPMs. The pilot elected to return to the departure airport and his mechanic inspected the airplane. The mechanic discovered a blister in the engine casing and fragments of metal in the oil. The engine was then disassembled and a ball bearing from the propeller governor was located in the engine which had the potential of resulting in a catastrophic engine failure. Examination of the engine showed that the ball bearings from the governor were able to pass through the oil drain hole of the governor. Follow up examinations of the propeller governor showed that the governor bearing race and plunger were assembled with the bearing race set screw and plunger hole misaligned. When the bearing race set screw was torqued down, the set screw tip flattened against the harder plunger surface. During operation, the set screw/plunger race separated.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot should have returned to land after first RPM anomaly.

NTSB coding

  • Sys/Comp malf/fail (non-power) · Enroute-climb to cruise

Evidence available

  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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