Service difficulty report · Flapper Valve · Dhav DHC6300

Difficulty date
April 5, 2007
Submitted
May 1, 2007
Operation
General aviation
Make and model
Dhav DHC6300
Engine
Pwa PT6A27
Part
Flapper Valve
Part number
C6VF11531
Condition
Obstructed
Location
Ram Air Duct
Part time
14 hours
Component
Ram Air Duct · Dhav
Component part number
C6VF11531
Stage of operation
IN
How discovered
9
Nature of condition
W
Precautionary procedure
K

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

What was found

(CAN) THE RAM AIR FLAPPER VALVE, P/N C6VF1153-1, BECAME JAMMED IN IT`S DUCT. ATTEMPTS BY THE PILOT TO RECTIFY THE PROBLEM BY MOVING THE CONTROL LEVER BACK AND FORTH RESULTED IN THE CONTROL CABLE, P/N 130-032A22.75B29.0, BECOMING KINKED AND UNSERVICEABLE. DIS-ASSEMBLY OF THE SYSTEM REVEALED THAT THE RUBBER-LIKE MATERIAL USED TO SEAL THE PERIMETER OF THE FLAPPER VALVE HAD BECOME DISTORTED AND ENLARGED, POSSIBLY DUE TO EXPOSURE TO HEAT. THIS CAUSED THE SEAL TO CONTACT THE INNER WALLS OF THE DUCT BEFORE THE FLAPPER WAS AT A 90-DEGREE ANGLE TO THE DUCT, IE: BEFORE THE FLAPPER WAS IN THE CLOSED POSITION. REMOVAL AND REPLACEMENT OF THE DAMAGED CABLE AND FLAPPER VALVE REQUIRED REMOVAL AND REPLACEMENT OF MUCH OF THE A