NTSB Identification: FTW91FA029.
The docket is stored on NTSB microfiche number 44643.
Accident occurred Friday, January 11, 1991 in NACOGDOCHES, TX
Probable Cause Approval Date: 03/09/1993
Aircraft: BEECH F-90, registration: N311DS
Injuries: 1 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

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.

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