# NTSB FTW91FA029: Beech F-90, N311DS, Nacogdoches, TX, January 11, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: January 11, 1991, 10:40 local (16:40 UTC)
- Place: Nacogdoches, TX
- Location: 31.5918° N, 94.7142° W: Placed by OpenAirDocs from NTSB’s distance and direction from NACOGDOCHES A L MANGHAM JR RGNL (OCH), within about a mile (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=31.5918&lon=-94.7142&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report March 9, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 23242
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW91FA029
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/23242/pdf
- Page: https://openairdocs.org/ntsb/FTW91FA029

## Probable cause

THE LOSS OF THRUST DUE TO THE PROPELLER'S FEATHERING ON LIFTOFF AS A RESULT OF IMPROPER ADJUSTMENTS MADE DURING AN ENGINE CHANGE. A FACTOR WAS THE LACK OF SUITABLE TERRAIN TO WHICH THE PILOT COULD EXECUTE A FORCED LANDING.

## Sequence of events

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

- Airframe/component/system failure/malfunction, takeoff - initial climb
  - propeller governor control,linkage - improper (cause)
  - propeller feathering - inadvertent activation (cause)
  - maintenance,adjustment - improper, other maintenance personnel (cause)
- Forced landing, descent - emergency
- In flight collision with object, descent - emergency
  - object - tree(s)
  - terrain condition - none suitable (contributing factor)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

THE PILOT REPORTED THAT SHORTLY AFTER LIFTING OFF, THE AIRPLANE BEGAN DECELERATING SLOWLY. HE THOUGHT THE THROTTLES HAD RETARDED; HOWEVER, ALL OF THE ENGINE INSTRUMENTS INDICATED TAKEOFF POWER. REALIZING THAT HE COULD NOT RETURN TO THE AIRPORT, THE PILOT SELECTED A FORCED LANDING AREA AND AIMED THE AIRPLANE BETWEEN TWO TREES. INVESTIGATION REVEALED THAT BOTH PROPS WERE AT OR NEAR FEATHER PITCH ANGLES AT IMPACT AND BEING DRIVEN UNDER POWER. BOTH ENGINES HAD BEEN CHANGED IMMEDIATELY PRIOR TO THE FLIGHT AND BOTH GROUND IDLE STOPS HAD BEEN ADJUSTED AFTER THE ENGINE CHANGE WITH THE LEFT ENGINE BEING SLAVED TO THE RIGHT. THE SYSTEM OPERATED OFF OF A SQUAT SWITCH ON THE RIGHT GEAR. MISRIGGING OF THE RIGHT ENGINE WOULD BE REFLECTED IN THE LEFT AND ALLOW OIL PRESSURE TO BE VENTED FROM THE DOMES, WHICH IN TURN WOULD ALLOW THE PROPELLER CYLINDER SPRINGS TO DRIVE THE PROPS TOWARD FEATHER AS THE RIGHT STRUT EXTENDED DURING TAKEOFF.

## Aircraft

- Registration: [N311DS](https://openairdocs.org/deregistered/N311DS-2013-08-06), registration cancelled 2013-08-06, S/N LA-41, built 1980 (OpenAirDocs)
- Reported make and model: BEECH F-90
- Registry model: [Beech F90](https://openairdocs.org/model/beech-f90) (registry code 1152909) (OpenAirDocs)
- Registry engine: [U/A Canada PT6A series](https://openairdocs.org/engine/u-a-canada-pt6a-series) (registry code 61508, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: LA-41
- Airframe hours: 3262
- Engines: P&W PT6A-135 750 horsepower turbo prop
- Damage: Destroyed
- Fire: On-Ground
- Flight: Ferry, Part 91
- Operator: Ridgeaire, Inc.
- Registered owner: Ridgeaire, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, January 9, 1991, 1 hours before
- Destination: ADS, ADDISON, TX
- Flight plan: IFR
- Airport: OCH, East Tex Reg., runway 36, 5,001 × 75 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 58; commercial, private; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 6,689 total, 56 in this make and model, 6,689 as pilot in command, 130 in the last 90 days, 70 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 310° at 11 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 41 °F, dew point 36 °F
- Altimeter: 30.00 inHg

## 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 19910111000389A](https://openairdocs.org/incident/19910111000389A), Jan 11, 1991: Beech F90, Nacogdoches, TX, Destroyed. Engines surged on takeoff props went to feather. Settled into trees. Indicates selenoid linkages improper setting.

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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