Pilot Debrief

ZENITH ZODIAC 650B near Eufaula, OK — 2022-07-12

Final reportCEN22LA315
Sign in to save
Date
2022-07-12
Location
Eufaula, OK, USA
Aircraft
ZENITH ZODIAC 650B
Registration
N452VC
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

The loss of engine power due to a push rod that was incorrectly installed by the airplane owner.

NTSB narrative

According to the pilots, who were both owners and builders of the airplane, while maneuvering during a local flight, the engine began to run rough. The engine power continued to decrease until they could not maintain altitude. Unable to reach a nearby airport, the pilot flying elected to perform an off-airport emergency landing. During the landing, the airplane impacted uneven terrain, which resulted in substantial damage to the right wing. Postaccident examination of the engine revealed the No. 5 cylinder exhaust valve rocker arm attach stud/bolt had failed. About 5 flight hours before the accident, the owners had replaced the No. 5 cylinder exhaust valve, which included the removal and reinstallation of the rocker arm hardware. The push rod contained an oil passage hole on one end that allowed for lubrication of the rocker arm, and the other end did not contain an oil passage. According to the owner, during the installation he incorrectly installed the push rod in a backward position. The incorrect installation did not allow lubrication to reach the rocker arm, causing it to fail.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Correctly install the push rod to ensure proper engine function.

NTSB coding

Evidence available

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

Docket documents3

Related mishaps