Pilot Debrief

REARWIN 8135 near Casa Grande, AZ — 2011-02-18

Final reportWPR11LA140
Sign in to save
Date
2011-02-18
Location
Casa Grande, AZ, USA
Aircraft
REARWIN 8135
Registration
NC25545
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The partial loss of engine power due to the separation of an exhaust valve rocker box as a result of the failure of the rocker box attaching studs.

NTSB narrative

The engine began losing power immediately after takeoff, and the pilot executed a forced landing in a rough, uneven field. The main landing gear sheared off, and the airframe sustained substantial damage. Postaccident examination of the engine determined that the No. 4 cylinder exhaust valve rocker box was detached from the head of the cylinder. Three of the six attaching studs where broken, and the other three studs had pulled out of the head. One of the three studs that had pulled out was rounded off, indicating that it had been loose in the head for some time. The adjacent stud was also rounded off, but not as much, and the final stud had no signs of rounding off. It is likely that the separation of the rocker box resulted in the partial loss of engine power because the exhaust valve for the No. 4 cylinder could no longer open and close properly, which allowed exhaust gases to migrate through the No. 4 cylinder's intake valve and into the induction system.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot did not check engine for hydraulic lock before starting after inactivity.

NTSB coding

Evidence available

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

Docket documents5

Related mishaps