NTSB Identification: IAD99FA023.
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Accident occurred Sunday, November 29, 1998 in MIDLAND, VA
Probable Cause Approval Date: 12/18/2001
Aircraft: Armbruster MINI-500, registration: N500GH
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The pilot/owner was flying his amateur-built helicopter and crashed in a wooded area. Examination of the helicopter revealed that the non-certificated 2-cycle engine had experienced a power loss due to a 'cold seizure.' About 18 Hobbs meter hours prior to the accident the pilot had replaced pistons, rings, wrist pins, rod bearings, thermostat and head O-rings. Metallurgical examination of the PTO cylinder walls revealed deposits from the side (piston skirt) of the accident PTO piston and a previous PTO piston, indicative of a prior cold seizure event. Although the kit helicopter was built according to plans, the engine manufacturer did not recommend several of the engine modifications found on the accident helicopter. Additionally, the engine manufacturer did not recommend the installation of this model engine in the helicopter and published the following warning with the engine manual: 'This engine, by its design is subject to sudden stoppage. Engine stoppage can result in crash landings, forced landings or no power landings. Such crash landings can lead to serious bodily injury or death.'

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

the improper repair of the engine following a previous engine seizure which resulted in the loss of engine power over unsuitable terrain.

Full narrative available

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