Service difficulty report · Pump · Aerosp ATR42*

Difficulty date
September 19, 1997
Submitted
March 26, 2000
Operation
General aviation
Make and model
Aerosp ATR42*
Engine
Pwa PW121
Part
Pump
Part number
8210181A
Condition
Defective
Location
Ovspeed Gov
Part time
17,943 hours
Stage of operation
NR
Nature of condition
J
Precautionary procedure
O

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

What was found

(CAN) THE ENGINE EXPERIENCED A PT OVERSPEED WHICH LASTED FOR A DURATION OF 43 SECONDS OVER 110 PERCENT NP SPEED REACHING A MAXIMUM OF 118.1 PERCENT. THE ENGINE WAS REMOVED AND SHIPPED FOR INSPECTION. DISASSEMBLY FOUND NO DAMAGE TO THE PRINCIPAL PT COMPONENTS ATTRIBUTED TO THE OVERSPEED CONDITION. IT WAS FOUND THE PROPELLER OVERSPEED GOVERNOR HYDRAULIC PUMP WAS GENERATING LESS THAN 50 PERCENT OF REQUIRED PRESSURE. THE CAUSE OF THE OVERSPEED WAS THE FAILURE OF THE PROPELLER OVERSPEED GOVERNOR HYDRAULIC PUMP TO PRODUCE SUFFICIENT PRESSURE TO CONTROL THE PCU, WHICH CAUSED THE PROPELLER TO GO INTO PITCH LOCK AT A FINER PITCH, RESULTING IN NP OVERSPEED. NO REASON FOR THE LOW PRESSURE OUTPUT OF THE PUMP WAS FOUND.

More about the Aerosp ATR-42