Plugged, Stiff, Broken

Before the second landing, the crew selected gear down, which showed down and locked, but the crew saw and smelled smoke. The landing gear circuit breaker tripped after gear completed cycle. Inspection confirmed source of smoke was from the landing gear actuator motor and a faulty dynamic brake relay (mfr p/n SM50D7) is suspected to have caused the landing gear motor to overtravel against hard stop and smoke.

Editorial Staff

Friday, July 19, 2013 at 12:00 AM ET

Verified

Key Takeaways:

Multiple critical aircraft components, including landing gear relays and fasteners, fuel vent systems, and engine ignition parts, experienced failures across various aircraft models.
These component failures led to significant operational issues such as landing gear collapse, engine power loss, engine start failures, and smoke during gear extension.
Failures occurred in parts with varying service lives, with some identified at relatively low total operating hours (e.g., 142 hours for a relay, 400 hours for a spark plug).

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Beechcraft F33A Bonanza
Failed Landing Gear Relay
Before the second landing, the crew selected gear down, which showed down and locked, but the crew saw and smelled smoke. The landing gear circuit breaker tripped after gear completed cycle. Inspection confirmed source of smoke was from the landing gear actuator motor and a faulty dynamic brake relay (mfr p/n SM50D7) is suspected to have caused the landing gear motor to overtravel against hard stop and smoke.
Part Total Time: 142 hours

Cessna 172
Plugged Fuel Vent System
The pilot made a precautionary landing due to a rough running engine. Pilot checked fuel and heard a “wooshing” sound when opening the right tank fuel cap. Pilot thought he corrected a venting problem and took off, but the aircraft lost power on climbout. Investigation revealed a plugged fuel system main vent line, plugged vent interconnect line at the left tank and a restricted right tank vented fuel cap (p/n C156003-0101).
Part Total Time: 4511 hours/56 years

Piper PA-28-181
Failed Main Landing Gear Fasteners
On rollout, right main landing gear collapsed and folded under the wing. Fasteners attaching gear trunion to airframe/wing failed allowing gear to exit wheelwell. Evidence indicates two lower outboard fasteners were broken or loose, allowing bolt holes in the wing spar and the trunnion to become elongated and splay materials outward of the bolt holes. Also, a lateral attach bracket that attached to the trunnion by two bolts and riveted to the aft side of the wing spar indicated fretting corrosion at the lowermost area, another indication of movement due to of failed fasteners.
Part Total Time: 6812 hours

Slick 6310 Magneto
Stiff/Frozen Bearing
Right engine of a Beechcraft Model 58 Baron would not start. Inspection revealed the engine’s left magneto was hard to rotate due to drive end bearing failure. No other damage was found. The stiff/frozen bearing was causing the impulse coupling to be ineffective. A new magneto was installed and the aircraft was returned to service.
Part Total Time: 646 hours

Tempest URHB32S Spark Plug
Broken Electrode
While completing a 1000-hour inspection and cleaning the spark plugs, one of the plugs was found to have a loose wire electrode at its attachment to the end of the spark plug. The wire could be rotated up out of alignment with the center electrode. After rotating the electrode up two times, it came out of the area where it had been crimped onto the plug.
Part Total Time: 400 hours