Pilot Debrief

ERCOUPE 415 near Dawsonville, GA — 2017-02-19

Final reportERA17LA109
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Date
2017-02-19
Location
Dawsonville, GA, USA
Aircraft
ERCOUPE 415
Registration
N99716
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Climb

Probable cause

A decrease in oil pressure due to the pilot's unintentional overfilling of the engine oil sump, and the pilot's subsequent decision to perform an off-airport precautionary landing, which resulted in impact with a tree.

NTSB narrative

The private pilot recently purchased the airplane and was returning it to his home airport. Before the flight, he added 1/2 quart of oil to the engine, bringing the oil level to between 3 1/2 and 4 quarts. About 30 minutes after departure, the pilot noticed that the oil pressure was dropping. He reduced engine power and turned the airplane toward the closest airport. The oil pressure continued to decrease, even though the engine continued to produce power, and the pilot chose to perform a precautionary landing on a road. Upon touchdown, the airplane skidded across the road until it impacted a tree and came to rest in a ditch. Examination of the engine revealed a hole in the oil sump consistent with impact damage, and oil was noted coming from the crankcase breather tube. In addition, oil was noted on the bottom of the airplane from the nose to the empennage. Even after the oil leaked from the broken oil sump and from the breather tube, the postaccident engine oil level was 3 1/2 quarts. A subsequent engine run demonstrated that the engine would experience a momentary drop in oil pressure indication if the oil sump was overfilled. The engine and the oil pressure gauge otherwise operated normally. Since the pilot lacked operational experience with the airplane, it is likely that he unintentionally overfilled the oil sump, which resulted in an interaction between the oil in the sump and the rotating crankshaft. The interaction likely resulted in air bubbles becoming entrained in the oil and a subsequent oil pressure fluctuation. Additionally, since he checked the oil level following a previous flight, it was likely that the oil had not fully drained back into the sump when the reading was taken. Considering that the oil pressure gauge operated normally after the accident, it is unlikely that the gauge was producing a faulty reading in flight.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have performed an emergency landing sooner after oil pressure drop.

NTSB coding

Evidence available

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

Docket documents7

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