Pilot Debrief

WSK PZL MIELEC M-18A near Anderson, IN — 2011-07-25

Final reportCEN11LA512
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Date
2011-07-25
Location
Anderson, IN, USA
Aircraft
WSK PZL MIELEC M-18A
Registration
N92640
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

The fatigue failure of the propeller governor speeder spring, which resulted in the pilot’s inability to control engine output power.

NTSB narrative

The pilot was marking a field in preparation for an aerial application when he experienced what he thought was an engine failure. He stated that the engine was still running, but it was not producing power. The pilot pushed the power lever forward; the engine power did not increase, but the engine temperature increased. He stated that the engine was idling fast and that he forced the airplane into a bean field about 150 to 200 yards ahead of a tree line. The pilot ground looped the airplane before contacting the trees. A postaccident examination of the engine did not reveal any anomalies. A bench test of the propeller governor revealed that the maximum speed was above the nominal limit and the minimum speed was below the nominal limit. The control lever position was set higher than the specified position, which indicated that the governor had been adjusted in an attempt to regulate the propeller speed. X-rays and a teardown revealed that the propeller governor speeder spring was fractured. A metallurgical examination revealed a preexisting fatigue crack that, over time, resulted in the failure of the spring. The failed speeder spring would have resulted in a loss of oil pressure to the propeller piston, which allowed the propeller blades to rotate to a high blade angle, which then decreased the engine speed and overall power output of the engine. Maintenance records showed the propeller governor was overhauled on May 19, 2009. The speeder springs did not have serial numbers, and, therefore, the maintenance history of the speeder spring could not be determined.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have opted for a different landing area earlier.

NTSB coding

Evidence available

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

Docket documents14

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