Pilot Debrief

CESSNA 152 near Miami, FL — 2016-11-13

Final reportERA17LA044
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Date
2016-11-13
Location
Miami, FL, USA
Aircraft
CESSNA 152
Registration
N94292
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The loss of torque on the No. 3 connecting rod’s nuts, which resulted in the failure of the No. 3 connecting rod’s bolts and a subsequent total loss of engine power due to the operator's maintenance personnel’s improper installation of the connecting rod nuts.

NTSB narrative

The private pilot reported that, during the instructional flight to accumulate flight time, the airplane experienced a rough-running engine in cruise flight and that the engine subsequently experienced a total loss of power. The pilot tried to restart the engine to no avail. He then chose to conduct a forced landing to a road, during which the airplane touched down on soft, wet ground before reaching the road. It then nosed over and came to rest inverted. During recovery of the airplane, large cracks were noted in the engine crankcase near the No. 2 cylinder. Disassembly of the engine revealed that the crankshaft was fractured at the No. 3 connecting rod journal and exhibited signatures consistent with extreme heat. The No. 3 connecting rod bolts fractured at the point where the nuts contacted the connecting rod. Each connecting rod nut had a flat-face side and a raised-lip side. As found, the nuts were oriented with the raised-lip side touching the connecting rod despite the engine manufacturer's service instruction, which stated that "Nuts [were] to be assembled with flat face side touching the connecting rod." The caution associated with the orientation of the connecting rod nuts at installation stated that "the connecting rod bolt cannot be tightened correctly if the nut on the connecting rod is installed incorrectly." The operator's maintenance personnel likely installed the nuts incorrectly during an engine overhaul about 246 flight hours before the accident flight, which resulted in a loss of torque on the connecting rod's nuts and the subsequent fracture of the connecting rod's bolts and total loss of engine power.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Proper installation of connecting rod nuts could have prevented engine failure.

NTSB coding

Evidence available

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

Docket documents5

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