Service difficulty report · Potentiometer · Sino SJ302

Difficulty date
February 24, 2020
Submitted
December 3, 2020
Operation
General aviation
Aircraft
N50SJ
Make and model
Sino SJ302
Aircraft serial
005
Aircraft time
821 hours, 586 cycles
Engine
Wilint FJ442A
Engine time
942 hours, 637 cycles
Part
Potentiometer
Condition
Contaminated
Location
Te Flaps
Part time
821 hours, 586 cycles
Stage of operation
AP
How discovered
O
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

FLAP POTENTIOMETERS USED FOR INDICATION AND CONTROL OF THE TRAILING EDGE FLAPS WERE FOUND TO BE NOT ENVIRONMENTALLY SEALED. THE COMPONENTS WERE QUALIFIED FOR AN ENCLOSED LOCATION, NOT AN EXPOSED LOCATION WHERE THEY ARE INSTALLED. AFTER REPEATED FLAP FAILURES ON THE FLIGHT TEST AIRCRAFT, IT WAS DISCOVERED THAT MOISTURE WAS ENTERING THE POTENTIOMETER AND LIKELY FREEZING AT ALTITUDE. THIS CAUSED ERRANT SIGNALS FROM THE POTENTIOMETERS AND INDICATED FLAP FAILURES WHEN THE FLAPS WERE DEPLOYED ON APPROACH. THE ZONE IN WHICH THE COMPONENT IS INSTALLED DICTATES THAT THE POTENTIOMETERS MUST BE ENVIRONMENTALLY SEALED, A DETAIL THAT WAS MISSED IN THE ORIGINAL CERTIFICATION OF THE SJ30-2. SYBERJET, THE CURRENT OWNER OF THE SJ30 TYPE CERTIFICATE, HAS OBTAINED NEW (PROPERLY SEALED) PARTS FROM THE MANUFACTURER AND INSTALLED THEM ON THE FLIGHT TEST AIRCRAFT FOR EVALUATION.

More about the Sino SJ30-2