Grumman Acft Eng Cor-Schweizer G 164C N6674K

Summary

On 29 April 2018 at about 22:30 local time, a Grumman Acft Eng Cor-Schweizer G 164C registered N6674K was involved in an accident near Maxwell, California, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

29 April 2018 at 22:30

Classification

Accident

Location

Maxwell, California, United States

Nearest airport

Richter Aviation Airport (12CN)

Coordinates

39.2647, -122.1192

Aircraft

Grumman Acft Eng Cor-Schweizer G 164C

Registration

N6674K

Category

Airplane

Year built

1978

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Maxwell → Maxwell

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR18LA128

Nobody was injured.

A total loss of engine power due to an uncommanded closing of the fuel shutoff valve, which terminated fuel to the engine. The reason for the fuel shutoff valve’s closure could not be determined based on the available information.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The pilot departed the private agricultural airstrip to the south, orbited over the area just west of the airstrip, then proceeded east. Just east of the airstrip, the pilot turned left heading north then made a 180° left turn back toward the south and onto a right downwind in preparation to land to the north. The pilot stated that about midway down and parallel to the runway, the engine surged about two to three times then completely lost power. The pilot elected to perform a forced landing in a plowed field, but during a short landing roll, the airplane nosed over on its back, which resulted in substantial damage to both upper wing panels, both horizontal stabilizers, the rudder, and the elevator. Postaccident examination of the engine revealed damage consistent with an engine that was not producing power at the time of impact. Functional tests of the fuel control unit identified fuel schedules that were out of specification limits, and operation of the engine at low power conditions with the out-of-specification fuel control settings most likely resulted in unstable engine operation below 100% engine speed. The fuel shutoff valve (FSOV), which terminates fuel flow to the engine, was found in the electrically commanded closed position after removal from the airplane. Testing of the valve indicated that it required a higher voltage to open than specified, and had a higher leakage through the output port than was specified, but it passed all other tests and neither condition would cause an uncommanded closing of the valve. The results of the engine teardown examination coupled with the functional testing of various engine components failed to reveal what precipitated the reported engine surge condition before the subsequent loss of engine power.

Quoted verbatim from the NTSB record.