SDR CA010515005

Service difficulty report · Rheostat · Dhav DHC6300

Difficulty date: April 10, 2001
Submitted: May 25, 2001
Operation: General aviation
Make and model: Dhav DHC6300
Aircraft time: 9,214 hours
Engine: Pwa PT6A27
System (JASC): 3510 · Crew Oxygen System
Part: Rheostat
Condition: Overheated
Location: Cockpit
Part time: 9,250 hours, 12,943 cycles
Component: Oxygen System
Stage of operation: CR
How discovered: O
Nature of condition: B
Precautionary procedure: H, A

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

What was found

(CAN) OXYGEN REGULATOR IN COPILOT POSITION WAS REPLACED WITH OVERHAULED UNIT. INTERNAL LIGHTING WIRES FOR THIS UNIT WERE CONNECTED IMPROPERLY (POLARITY REVERSED).AS A RESULT THE RHEOSTAT WHICH CONTROLS LIGHT INTENSITY FOR THE COPILOTS INSTRUMENT LIGHTING WAS SHORTED TO GROUND. THE 5 AMP CIRCUIT BREAKER THAT PROTECTS THIS LIGHTING RHEOSTAT DID NOT POP AND CAUSED THIS RHEOSTAT (RATED AT 2.7 AMPS MAX .7 MIN.) TO OVERHEAT AND CAUSE SOME SMOKE IN THE COCKPIT AREA.