Pilot Debrief

ZENITH CH 750 near Montrose, MO — 2020-09-20

Final reportCEN20LA412
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Date
2020-09-20
Location
Montrose, MO, USA
Aircraft
ZENITH CH 750
Registration
N210WP
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

A total loss of engine power due to an electrical overload in the engine control unit wiring system; the electrical overload occurred as a result of improper installation by the airplane builder.

NTSB narrative

The pilot of the experimental, amateur-built airplane was en route to the destination airport when the engine momentarily lost power. The pilot immediately selected the alternate fuel pump and engine control unit (ECU), and the engine regained power. About 5 minutes later, the engine lost total power, and the pilot attempted to restart the engine. The engine restart was unsuccessful, and the pilot performed a forced landing to a field, during which the airplane nosed over and came to rest inverted, resulting in substantial damage to the left wing and rudder. Postaccident examination of the airplane revealed that the main fuse block was discolored and exhibited internal thermal damage. An automotive blade-type fuse that connected to both primary and secondary fuel pumps and primary and backup ECUs displayed arcing signatures and had failed. According to the engine manufacturer, the primary and secondary ECUs should have been wired directly to the main bus and should not have contained a fuse. The improper installation of the airplane’s electrical system resulted in an overloaded electrical system for the installed fuse. After bypassing the failed electrical system, an engine test run was performed. The engine started and operated normally with no mechanical issues noted.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Not modifying the ECU wiring as per manufacturer service bulletin.

NTSB coding

Evidence available

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

Docket documents5

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