Service difficulty report · Servo · Beech E55

Difficulty date
June 27, 2019
Submitted
September 8, 2020
Operation
General aviation
Aircraft
N664AR
Make and model
Beech E55
Aircraft serial
TE1163
Part
Servo
Part number
1C4701292P
Part serial
7070A
Condition
Overtorqued
Location
Clutch Tension
Stage of operation
AP
How discovered
O
Nature of condition
W
Precautionary procedure
O

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

FOLLOWING A FATAL ACCIDENT, TESTING OF THE CLUTCH TENSION OF THE PITCH SERVO REVEALED THE BREAKAWAY FORCE NEEDED WAS 45 LBS. THE SPECIFIED REQUIRED CLUTCH TENSION BREAKAWAY FORCE SETTING IS 13 +/- 2 LBS. THIS SETTING IS ACHIEVED BY TIGHTENING THE CASTLE NUT ENOUGH TO ACHIEVE THE CLUTCH TENSION BREAKAWAY FORCE REQUIRED BY DRAWING DURING FINAL FUNCTIONAL TESTING. AFTER THAT, AN ORANGE TORQUE SEAL STRIP IS APPLIED AND A COTTER PIN IS INSTALLED. UPON FURTHER VISUAL INSPECTION, THE COTTER PIN USED TO SECURE THE CASTLE NUT RETAINING THE CLUTCH APPEARED TO BE NEW, AND THE CASTLE NUT DID NOT ALIGN WITH THE FACTORY ORANGE TORQUE STRIP SETTING APPLIED AT THE TIME OF SERVO COMPLETION AND FINAL TESTING. THE ORANGE TORQUE STRIP ON THE NUT AND THE ORANGE TORQUE STRIP ON THE TENSION WASHER WAS APPROXIMATELY THREE-QUARTER OF A TUM OFF. AT SOME POINT DURING PREVIOUS MAINTENANCE, THE CASTLE NUT SECURING THE CLUTCH ON THE SERVO WAS OVERTIGHTENED, WHICH CAUSED THE BREAKAWAY FORCE NEEDED TO BE 30 LBS TOO MUCH.

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