The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.
Gear Retraction Failure
The pilot reported selecting gear up with no results. A maintenance technician tracked the problem to an intermittent dynamic breaker relay, p/n SM50D7, but did not make a recommendation.Part Total Time: 245 hours.
The AN3-7A top rudder hinge bolt was described as having loosened from its locking nut plate, precipitating complete rudder separation while the aircraft was in flight at 2000 feet agl. The mechanic suggests there should be additional safeties for these rudder hinge bolts other than the mechanical locking features of the nut plates.Part Total Time: unknown.
Oversized Exhaust Couplings
Both tail pipe/muffler connections (p/n STC-8645SW) were found to be oversized. The exhaust pipe clamps were not of sufficient strength to squeeze the oversized pipe down on the muffler exhaust tube. The resulting loose fit was allowing exhaust fumes to shoot into the cabin heat and carburetor heat sections of the mufflers. One thing that aggravated the condition was the fact that the tail pipes were crammed too far up on the muffler pipe.Part Total Time: unknown.
Cracked Wing Spar
A borescope inspection of this aircrafts aft wing spar unveiled a crack around the flap-track attach points. Probable cause is fatigue, states the submitter. This is a very high-time aircraft with over 13,000 hours total time. It has also been used as a flight trainer for its entire life. I recommend all C172s with 8000 hours or more be inspected, by borescope or other acceptable means, (in) the area of the rear wing spars around the flap track attach points.Part Total Time: 13,526.01 hours.
While flaps were being retracted, the L/H inboard flap attach bracket caught on the wing cove panel support, states the mechanic. This caused substantial damage to the cove panel support as well as the attach bracket. Cause was determined to be worn flap tracks (p/n 0523231-13). The repair included installation of new tracks and rollers. He recommends replacement of these parts at 5000-hour intervals, as they are not life limited by Cessna. The damaged flap was replaced with a serviceable unit.Part Total Time: unknown.
Missing Alt-Air Door Spring
Climbing to 8000 feet, the pilot noticed a power loss and engine surging at two different times. During a phase-1 inspection, a mechanic observed the alternate-air door stuck in the open position. Further scrutiny revealed the spring (p/n 0550361-25) assisting the door was missing from the hinge assembly. The controlling servo was inspected for damage and the possible presence of the missing spring neither was evident. This mechanic feels the alternate-air system …is weak and needs to be improved.Part Total Time: 743.1 hours.