Accident Details
Probable Cause and Findings
The engine failure due to several loose, damaged cylinder stud nuts and hold-down bolts. Contributing to the accident was maintenance personnel’s failure to detect that the cylinder nuts and hold-down bolts were not properly secured during the engine’s most recent inspection.
Aircraft Information
Registered Owner (Historical)
Analysis
On June 31, 2015, about 1130 central daylight time, a Grumman G-164A, N963X, impacted terrain after the engine lost power near Emmett, Kansas. The pilot, the sole occupant on board, received minor injuries. The airplane was substantially damaged. The airplane was registered to and operated by Precision Aerial Ag LLC of Seneca, Kansas, under the provisions of 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Wamego, Kansas approximately 1100.According to the pilot's accident report, he was making a spray run when he heard a loud "bang," saw a puff of smoke emit from the upper right-hand side of the engine, and then the propeller seized. He made a forced landing in a brome field, collided with some bushes, and nosed over. Examination of the engine on-site by inspectors from the Federal Aviation Administration revealed several loose cylinder stud nuts and hold-down bolts that appeared to have been pushed up on the cylinder skirt. Several of the studs – number 4 cylinder in particular -- were stretched and looked to be nearly pushed out of the engine crankcase. One cylinder was about to separate from crankcase.
Examination of the engine maintenance logbook revealed the engine had received a major overhaul on February 13, 2007. On March 10, 2010, Airworthiness Directive (A.D.) 99-11-02 was complied with by inspecting the cylinder heads. On March 2, 2011, February 22, 2012, May 30, 2013, and May 13, 2014, A.D. 56-06-02 was complied with by inspecting the cylinder hold-down studs. On July 15, 2014, the engine and propeller were removed due to a blower bearing failure. On August 10, 2014, after the engine and propeller were reinstalled, and again on March 18, 2015, the cylinder bases and heads were checked for cracks and loose studs. At the time of the last inspection, the tachometer read 6,730 hours, and the engine had accrued 506.68 hours since major overhaul.
The accident site was located at 14624 A4 Road, Emmett, Kansas.
Data Source
Data provided by the National Transportation Safety Board (NTSB). For more information on this event, visit the NTSB Records Search website. NTSB# CEN15LA330