# NTSB FTW89DPJ08: Grumman G-164, N788Y, Guymon, OK, July 8, 1989

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Final report
- Date: July 7, 1989, 19:15 local (Jul 8, 1989, 00:15 UTC)
- Place: Guymon, OK
- Coordinates: 36.679283, -101.479171 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=36.6793&lon=-101.4792&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report September 5, 1991
- Report: Approved by Office Director
- NTSB case key (mKey): 22702
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW89DPJ08
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/22702/pdf
- Page: https://openairdocs.org/ntsb/FTW89DPJ08

## Probable cause

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.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering - turn to reverse direction
  - engine assembly,mount - fatigue (cause)
  - engine assembly,mount - failure,total (cause)
  - engine assembly - separation
- Loss of control - in flight, maneuvering - turn to reverse direction
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

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.

## Aircraft

- Registration: [N788Y](https://openairdocs.org/deregistered/N788Y-1989-12-19), registration cancelled 1989-12-19, S/N 180 (OpenAirDocs)
- Reported make and model: GRUMMAN G-164
- Registry model: [Grumman G-164](https://openairdocs.org/model/grumman-g-164) (registry code 3952702) (OpenAirDocs)
- Category: Airplane
- Serial number: 180
- Airframe hours: 6347
- Engines: P&W R-985-AN-14B 450 horsepower reciprocating
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Gray, Ronald W., doing business as Gray'S Spraying Service
- Registered owner: Ronald W Gray
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, November 1, 1988, 100 hours before
- Departed: NONE, HOOKER, OK
- Airport: GUY

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: center; flight hours: 12,000 total, 2,500 in this make and model, 12,000 as pilot in command, 120 in the last 90 days, 40 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 80° at 7 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 90 °F, dew point 52 °F
- Altimeter: 30.00 inHg
- Observed at: LBL, 29 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19890707021169A](https://openairdocs.org/incident/19890707021169A), Jul 7, 1989: Scwzer G164B, Guymon, OK, Substantial damage. Engine separated from aircraft during pullup from spray run. Top mounts broke in fatigue. Aircraft impact on belly.

## Other investigations on N788Y (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB FTW86LPJ10](https://openairdocs.org/ntsb/FTW86LPJ10), Jun 27, 1986: Grumman G-164 (N788Y), Hooker, OK, substantial damage

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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