Service difficulty report · Signal Cond Unit · Dhav DHC8301

Difficulty date
February 23, 2019
Submitted
August 14, 2020
Operation
General aviation
Make and model
Dhav DHC8301
Aircraft time
64,471 hours
Engine
Pwa PW123
Propeller
Hamstd 14SF15
Part
Signal Cond Unit
Part number
30005000034
Condition
Failed
Location
Prop Torque
Part time
54,495 hours
Stage of operation
TO
How discovered
O
Nature of condition
F
Precautionary procedure
C

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

What was found

(CAN) 2961 HRS SINCE REPAIR DURING T/O ROLL AS THE LH ENGINE TORQUE WAS RISING TO APPROX 70% THE TORQUE SURGED TO OVER 100% AND PROP RPM DROPPED TO APPOX 600-800 RPM. CAPT SAID IT SOUNDED LIKE THE PROP WAS PARTIALLY FEATHERING.TAKE OFF WAS REJECTED AT OR BELOW 80 KTS. DURING SUBSEQUENT ENG RUN WITH THE CAPT IT WAS DETERMINED THAT 1) THE ECU MODE HAD NO EFFECT ON THE SNAG AND 2) WHEN THE AUTO FEATHER WAS SELECTED OFF THE ENGINE OPERATED NORMALLY. IT WAS ALSO NOTED THE AUX FEATHERING PUMP GREEN LIGHT WAS COMING ON DURING THE EVENTS AND THE AUTO FEATHER WAS NOT ARMING. REPLACED TORQUE SIGNAL CONDITIONER UNIT I.A.W. AMM. 72-01-10-7. WIRING CHECKS CARRIED OUT IAW A/F TROUBLESHOOTING GUIDE PROBLEM 5, NFF. RUNS FOR TSCU REPLACEMENT AS PER ENGINE RIGGING MANUAL PART 5 CARRIED OUT CHECK SERVICEABLE. AUTOFEATHER TEST AS PER ERM PART 5 CARRIED OUT CHECKED SERVICEABLE.