Pilot Debrief

UNIVAIR AIRCRAFT CORPORATION 108-1 near Tuftonboro, NH — 2013-07-17

Final reportERA13LA327
Sign in to save
Date
2013-07-17
Location
Tuftonboro, NH, USA
Aircraft
UNIVAIR AIRCRAFT CORPORATION 108-1
Registration
N8721K
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Initial climb

Probable cause

Maintenance personnel’s failure to remove circumferential gouges in the aft radius of the R2 rod journal on the crankshaft during its last engine overhaul, which resulted in the fatigue failure of the crankshaft and a subsequent total loss of engine power.

NTSB narrative

About 7 minutes after takeoff and while leveling off the airplane at 1,800 ft, the pilot leaned the fuel-to-air mixture, and the engine immediately began to run roughly. The more experienced right-seat pilot took control of the airplane and attempted to restore power, but his attempts were unsuccessful. The propeller continued to rotate briefly but then stopped. The pilot maneuvered the airplane for a forced landing in a field, and the airplane subsequently impacted a raised concrete culvert. Postaccident examination of the engine revealed that the crankshaft was fractured. Metallurgical examination of the crankshaft revealed evidence of fatigue cracking that had originated from circumferential gouges at the aft radius of the R2 rod journal. A review of engine records revealed that, about 45 years before the accident, the crankshaft was replaced during an engine overhaul and that the main and connecting rod bearing journals were ground 0.010-inch undersize. About 7 years before the accident, the engine was overhauled again, and the crankshaft main and connecting rod bearing journals were polished. The engine was installed in the accident airplane about 3 years before the accident; the engine failure occurred about 115 hours after the engine's last overhaul. It is likely that, if maintenance personnel had detected and removed the circumferential gouges at the aft radius of the R2 rod journal during the engine's last overhaul, the fatigue cracking would not have started and the crankshaft would not have failed.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have aborted takeoff after engine began to run rough.

NTSB coding

Evidence available

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

Docket documents12

Related mishaps