NTSB Identification: DEN92IA074.
The docket is stored on NTSB microfiche number 48223.
Scheduled 14 CFR
Incident occurred Tuesday, July 21, 1992 in DENVER, CO
Probable Cause Approval Date: 05/26/1993
Aircraft: EMBRAER EMB-120 RT, registration: N221YV
Injuries: 26 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

THE CAPTAIN WAS FLYING THE AIRPLANE WITH HIS RIGHT HAND RESTING ON THE POWER CONTROLS. AS THE AIRPLANE TURNED ONTO FINAL APPROACH, IT ENCOUNTERED TURBULENCE OF SUFFICIENT INTENSITY THAT THE CAPTAIN'S FEET CAME OFF THE RUDDER PEDALS. HE FELT A 'CLICK' IN HIS HAND AND 'THERE WAS AN INSTANTANEOUS PROPELLER OVERSPEED.' THE ENGINE WAS EVENTUALLY SECURED BY CLOSING THE FUEL SHUTOFF VALVE AND AN UNEVENTFUL NO FLAP LANDING WAS MADE. POST INCIDENT EXAMINATION DISCLOSED BOTH AIR GROUND CIRCUIT BREAKERS WERE OPEN. THE LEFT ENGINE WAS FOUND TO BE FUNCTIONALLY DESTROYED. A READOUT OF THE DIGITAL FLIGHT DATA RECORDER DISCLOSED THE MAXIMUM LEFT AND RIGHT PROPELLER RPM VALUES ATTAINED WERE 150.49% AND 120.4%, RESPECTIVELY. VERTICAL ACCELERATION VALUES RANGED FROM .647 TO 1.26 G'S, AND LONGITUDINAL ACCELERATION VALUES RANGED FROM .037 TO .096 G'S. THE RIGHT ENGINE TORQUE PEAKED AT 37%, WHILE THE LEFT ENGINE TORQUE REMAINED AT 0%. RIGHT ENGINE FUEL FLOW WAS 16% TO 19% LOWER THAN LEFT ENGINE FUEL FLOW, AND PROPELLER IMBALANCE VALUES FOR THE LEFT ENGINE WAS APPROXIMATELY 50% HIGHER THAN THOSE RECORDED FOR THE RIGHT ENGINE.

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

OPEN AIR GROUND CIRCUIT BREAKERS THAT ALLOWED THE PROPELLERS TO OVERSPEED. A FACTOR WAS: CLEAR AIR TURBULENCE.

Index for Jul1992 | Index of months