NTSB Identification: WPR11LA140
14 CFR Part 91: General Aviation
Accident occurred Friday, February 18, 2011 in Casa Grande, AZ
Probable Cause Approval Date: 05/03/2012
Aircraft: REARWIN 8135, registration: NC25545
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
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.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: 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. Full narrative available
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