Pilot Debrief

ZENITH STOL CH701 near Byron, CA — 2019-11-29

Final reportWPR20LA035
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Date
2019-11-29
Location
Byron, CA, USA
Airport
C83
Aircraft
ZENITH STOL CH701
Registration
N701WJ
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

The pilot/builder's improper construction of the cowling, which resulted in inadequate venting of the engine, its overheating, and a partial loss of engine power.

NTSB narrative

The pilot stated that he fabricated and installed a cowling on the airframe prior to the flight. During the initial climb, the engine experienced a partial loss of power and the water temperature climbed above the maximum temperature. The pilot made a forced landing at the departure airport and encountered wind during the approach. The airplane was pushed off the runway and landed hard in the grass; the airplane came to rest inverted. The engine manufacturer provided instructions to builders to ensure there is proper venting over the engine. The pilot stated that he did not use any plans to build the cowling and did not perform any tests of the venting. The cowling was open on the bottom but did not have aft venting. As a result, the air pressure behind the radiator likely increased to be equivalent to that of the ram air, resulting in the engine overheating and experiencing detonation, leading to the loss of engine power.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have checked engine cooling before takeoff to prevent overheating.

NTSB coding

Evidence available

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

Docket documents4

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