Grumman-Schweizer G-164B accident near Buttonwillow, California, June 8, 1990
On June 8, 1990 at about 1:30 pm local time, a Grumman-Schweizer G-164B, registered N6725K, was destroyed in an accident near Buttonwillow, California. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
FAILURE OF THE #7 CYLINDER DUE TO A PRE-EXISTING CRACK. THE TERRAIN CONDITION WAS A RELATED FACTOR.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 8, 1990 · about 1:30 pm local time
- Place
- Buttonwillow, California · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Grumman-Schweizer G-164B
- Registration
- N6725K · registry record · serial 438B
- Damage
- Destroyed
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
THE PILOT WAS COMPLETEING AN AERIAL APPLICATION SWATH RUN, WHEN HE HEARD A LOUD BACKFIRE EMANATE FROM THE ENGINE DURING THE PULL-UP. THE ENGINE THEN QUIT RUNNING ALTOGETHER. THE PILOT ATTEMPTED TO MAKE A LANDING ON A DIRT ROAD, BUT LANDED SHORT IN A TOMATO FIELD, AND THE AIRCRAFT NOSED OVER ONTO ITS BACK. EXAMINATION OF THE ENGINE REVEALED THAT THE NUMBER 7 CYLINDER HEAD HAD A CRACK, WHICH EXTENDED FROM THE FORWARD SPARK PLUG BOSS AROUND THE CYLINDER HEAD TO THE REAR SPARK PLUG BOSS. DETAILED EXAMINATION OF THE CRACK SHOWED THAT THE FRACTURE FACE WAS CONTAMINATED BY CARBON DEPOSITS AND LIGHT CORROSION IN THE COARSE AREA OF THE CRACK, INDICATING THAT THE CRACK WAS PRESENT FOR A LENGTHY PERIOD OF TIME PRIOR TO THE ACCIDENT. THE CYLINDER WAS REPORTED TO HAVE ONLY 181 HOURS SINCE OVERHAUL.
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
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; rotorcraft: helicopter
- Flight time: 12,000 hours in all; 3,000 in this make and model; 150 in the last 90 days; 75 in the last 30 days; 12,000 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 4,894 hours
- Last inspection: annual inspection, April 17, 1990; 165 hours since
- Maximum gross weight: 4,500 lb
- Seats: 1
- Landing gear: fixed
- Engine: P&W R-1340-AN-1 (piston); 0 hours total
- Fire on the ground
- Operator: Vince Crop Duster, INC.
The flight
- Departed from: NONE at 1:00 pm
- Destination: NONE
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 140° at 5 knots
- Visibility: 20 statute miles
- Temperature: 70°F (21°C), dew point 59°F (15°C)
- Altimeter: 29.00 inHg
- Observation at 12:55 pm from BFL, 12 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Other NTSB records under N6725K 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.