JEFFERSON, MD, USA
N1094D
HUGHES 269C
ACCORDING TO WITNESSES THE ACFT CAME APART IN THE AIR. RADAR DATA SHOWS THE ACFT AT 2600 FT WHEN IT TURNED ABOUT 35 DEGREES RIGHT IN ABOUT 4 SECONDS. THE ACFT SUSTAINED GENERAL DISINTEGATION. EXAMINATION REVEALED THAT THE SPLINES OF THE TAIL ROTOR SPLINED DRIVE SLEEVE WERE EXCESSIVELY WORN, RENDERING LOSS OF TRANSMISSION OF TORQUE TO THE TAIL ROTOR. TWO OTHER HU-269 ACFT HAD SIMILIAR WEAR OF THE SPLINED SLEEVE. 300-HR INSPECTION REQUIRES THAT THE UPPER PULLEY ASSEMBLY BE REMOVED AND INSPECTED, AND BEARINGS LUBRICATED. SCHWEIZER ACFT CORP HAD ISSUED SERVICE BULLETIN N-219 A MONTH BEFORE THE ACCIDENT WHICH REQUIRED RETORQUING OF THE SPLINE RETAINING NUT. HOWEVER, THE ACFT WAS WITHIN THE REQUIRED COMPLIANCE TIME, AND THE BULLETIN WAS NOT DONE.
THE FAILURE OF THE TAIL ROTOR DRIVE TRANSMISSION SYSTEM DUE TO A WORN TAIL ROTOR SPLINED DRIVE SLEEVE, AND INADEQUATE MAINTENANCE AND/OR INSPECTION BY THE OPERATOR. CONTRIBUTING TO THE LOSS OF CONTROL WAS THE STUDENT PILOT'S FAILURE TO MAINTAIN ADEQUATE ROTOR RPM DUE TO INEXPERIENCE.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
