Grumman G-164 accident near Guymon, Oklahoma, July 8, 1989
On July 8, 1989, a Grumman G-164, registered N788Y, was substantially damaged in an accident near Guymon, Oklahoma. 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 UPPER RIGHT ENGINE MOUNT (FIREWALL ATTACH BOLT) DUE TO FATIGUE, AND FAILURE OF THE LOWER RIGHT MOUNTING BOLT FOR AN UNKNOWN REASON, WHICH ALLOWED OVERLOAD FAILURE OF THE TWO REMAINING MOUNTING BOLTS AND SEPARATION OF THE ENGINE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 8, 1989
- Place
- Guymon, Oklahoma · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Grumman G-164 · all G-164s on the register
- Registration
- N788Y · no longer on the register · serial 180
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
DURING PULLUP FOR A TURNAROUND MANEUVER, THE ENG FELL FROM THE AG AIRPLANE. CONTROL WAS LOST & THE AIRPLANE HIT FLAT IN A FIELD. A POST-ACDNT INVESTIGATION REVEALED THE UPPER RIGHT ENG MOUNT (FIREWALL ATTACH BOLT) HAD FAILED FROM FATIGUE. THE LOWER RIGHT BOLT HAD ALSO FAILED PRIOR TO ENG SEPARATION, BUT ITS FACTURE SURFACE WAS TOO BADLY DAMAGED TO VERIFY THE REASON OF FAILURE. THE UPPER LEFT & LOWER LEFT ATTACH BOLTS WERE FOUND NECKED DOWN AT THEIR RESPECTIVE FRACTURES FROM OVERLOAD FAILURE.
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: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: airplane single-engine; instrument: airplane
- Flight time: 12,000 hours in all; 2,500 in this make and model; 120 in the last 90 days; 40 in the last 30 days; 12,000 as pilot in command
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 6,347 hours
- Last inspection: annual inspection, November 1, 1988; 100 hours since
- Maximum gross weight: 3,750 lb
- Seats: 1
- Landing gear: fixed
- Engine: P&W R-985-AN-14B (piston); 0 hours total
The flight
- Departed from: NONE Hooker OK
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 080° at 7 knots
- Visibility: 15 statute miles
- Sky: clear
- Temperature: 90°F (32°C), dew point 52°F (11°C)
- Altimeter: 30.00 inHg
- Observation at 11:50 pm from LBL, 29 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 N788Y 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.