# NTSB BFO91LA054: Grumman AA-1C, N9755U, Union Hall, VA, June 13, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: June 13, 1991, 10:54 local (14:54 UTC)
- Place: Union Hall, VA
- Coordinates: 36.999519, -79.679794 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=36.9995&lon=-79.6798&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report December 14, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 11681
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=BFO91LA054
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/11681/pdf
- Page: https://openairdocs.org/ntsb/BFO91LA054

## Probable cause

THE LOSS OF ENGINE POWER BROUGHT ON BY A FAILURE OF THE NUMBER THREE CLYINDER EXHAUST VALVE. CONTRIBUTING TO THE ACCIDENT WAS A HIDDEN OBJECT ON THE EMERGENCY LANDING FIELD.

## Sequence of events

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

- Loss of engine power(total) - mech failure/malf, cruise - normal
  - engine assembly,valve,exhaust - failure,partial (contributing factor)
- Forced landing, descent - emergency
- Nose over, landing - roll
  - terrain condition - hidden obstruction(s) (contributing factor)

## Analysis

THE PILOT WAS AT CRUISE ALTITUDE WHEN HE EXPERIENCED A PARTIAL LOSS OF POWER. HE TRIED TO ANALYZE HIS PROBLEM WITH NO SUCCESS. HE THEN EXPERIENCED A FURTHER POWER LOSS AND ELECTED TO DIVERT TO A NEARBY AIRPORT. THE ENGINE COULD NOT PRODUCE ENOUGH POWER TO MAINTIAN ALTITUDE SO THE PILOT FOUND IT NECESSARY TO MAKE A FORCED LANDING IN AN OPEN FIELD. AFTER TOUCHDOWN, THE AIRCRAFT STRUCK A HIDDEN OBSTRUCTION WHICH TORE AWAY THE LEFT AND NOSE LANDING GEAR.

## Aircraft

- Registration: [N9755U](https://openairdocs.org/deregistered/N9755U-1991-09-10), registration cancelled 1991-09-10, S/N AA1C0114 (OpenAirDocs)
- Reported make and model: GRUMMAN AA-1C
- Registry model: [Grumman American Avn. AA-1C](https://openairdocs.org/model/grumman-american-avn-aa-1c) (registry code 3960100) (OpenAirDocs)
- Category: Airplane
- Serial number: AA1C0114
- Airframe hours: 1557
- Engines: LYCOMING O-235-L2C 115 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Operator: Christopher P. Nelson
- Registered owner: Christopher P. Nelson
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, December 1, 1990
- Departed: W03, WILSON, NC
- Destination: BKW, BECKLY, WV

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 43; private; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 333 total, 279 in this make and model, 277 as pilot in command, 35 in the last 90 days, 24 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 50° at 6 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 84 °F, dew point 61 °F
- Altimeter: 30.00 inHg
- Observed at: ROA, 40 nm away

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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