Amateur-built TANGO N76HT accident near New Port Richey, Florida

Probable cause

The improper inspection of the airplane ignition system during the last condition inspection by a mechanic, resulting in an ignition cable disconnecting and a partial loss of engine power.

NTSB analysis

The pilot descended to 1,000 feet mean sea level and attempted to increase the engine power. The engine did not respond and the pilot realized that the airplane would not be able to make it to the closest airport. He elected to perform a forced landing on a road. An automobile pulled out on the road and the pilot had to extend the airplane's glide. The airplane collided with mangrove trees and came to rest off the side of the road.

A postaccident examination of the airframe, flight controls, and engine assembly revealed no evidence of a mechanical malfunction. The airplane was configured with one magneto installed on the left side of the engine and an experimental electronic ignition system installed on the right side. An electronic module was installed on the magneto pad and connected to two high-tension spark coils mounted on top of the engine, which fired the upper spark plugs. There were two wires from the module to each coil supplying the trigger voltage signal to fire the spark plugs. One of the wires to the right coil, firing cylinder Nos. 1 and 3, was not connected.

A wiring harness connected the module to the airframe electrical system and the spark coils. The harness was connected to the module with a "D" plug, which was held in place with two screws. The plug was found disconnected from the module and hanging loose. This likely resulted in the complete loss of power to the right ignition system, causing a partial loss of engine power as reported by the pilot.

Review of the airplane logbooks revealed the airplane had flown 25.7 hours since the last condition inspection. The airframe and powerplant mechanic who performed that inspection stated that he did not check the "D" plug during that condition inspection.

Text from the NTSB. Open the NTSB docket for ERA10LA301 for the full record.