Grumman Acft Eng Cor-Schweizer G 164C accident near Maxwell, California, April 29, 2018
On April 29, 2018 at about 10:30 pm local time, a 1978 Grumman Acft Eng Cor-Schweizer G 164C, registered N6674K, was substantially damaged in an accident during maneuvering (low-alt flying) near Maxwell, California (Richter Aviation Airport). It was an other work-use flight under general aviation rules (Part 91). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 29, 2018 · about 10:30 pm local time
- Place
- Maxwell, California · Richter Aviation Airport · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Grumman Acft Eng Cor-Schweizer G 164C C, built 1978 · all G 164Cs on the register
- Registration
- N6674K · registry record · serial 16C
- Damage
- Substantial damage
- Flight
- Other work-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (total) during maneuvering (low-alt flying) defining event
- Off-field or emergency landing during emergency descent
- Nose over/nose down during landing (landing roll)
- Fuel starvation during maneuvering (low-alt flying)
The NTSB's findings
- Aircraft › Aircraft power plant › Engine fuel and control › Fuel controlling system › Malfunction
- Not determined › Not determined › (general) › (general) › Unknown/Not determined
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land
- Flight time: 7,186 hours in all; 3,508 in this make and model; 13 in the last 90 days; 10 in the last 30 days; 7,132 as pilot in command
- Medical certificate: Class 2 (waiver time limited special)
- Seat: sngl
- Injury: no injuries
The aircraft
- Airframe total time: 10,114 hours
- Last inspection: annual inspection, April 18, 2018; 30 hours since
- Maximum gross weight: 6,300 lb
- Seats: 1
- Landing gear: fixed
- Engine: Garrett TPE331-10-511 (turboprop); 69,835 hours total
The flight
- Departed from: 12CN Maxwell CA at 10:25 pm
- Destination: 12CN Maxwell CA
- Flight plan: none
- Runway 34/1, 2,856 ft by 40 ft
Weather at the time
- Light: daylight
- Wind: from 160° at 8 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 77°F (25°C), dew point 55°F (13°C)
- Altimeter: 29.87 inHg
- Observation at 10:53 pm from MYV, 27 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
6 documents, released by the NTSB on June 15, 2021. View them here, or download them; the NTSB redacts some personal details before release, and this site shows the NTSB's own titles rather than its file names.
| # | Document | What it is | |
|---|---|---|---|
| 1 | Pilot/operator Aircraft Accident Report, NTSB Form 6120.1 | PDF, 9 pages | View Download |
| 2 | Honeywell Aerospace Teardown Report | PDF, 175 pages | View Download |
| 3 | Maintenance Records | PDF, 10 pages | View Download |
| 4 | Statement of Party Representatives to NTSB Investigation | PDF, 1 page | View Download |
| 5 | Release of Aircraft Wreckage, NTSB Form 6120.15 | PDF, 1 page | View Download |
| 6 | Photo Array of Accident Site | PDF, 4 pages | View Download |
The same docket at the NTSB · documents without a copy here are fetched from the NTSB when you open them.
Other NTSB records under N6674K the same tail number, which may have belonged to a different aircraft at the time
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.