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The 172s develop cracks in the stabilizer spar, 150s develop cracks in
the fin attach fittings, and the anchor nuts for those bolts will crack. 150s also develop enough wear in the rudder hinges that the rudder stops will go past the stop bolts and jam the rudder hard over, killing all on board. There's an AD on this, as well as the fin anchor nut propblem. Cessna has numerous service bulletins on various age-related issues on their airplanes, and my experience has been that most folks ignore them, since they're not "mandatory" like an AD. The cracking stab spar fits into that one, and almost any 172 with 5000 hours on it will have that cracking. Many folks move their airplanes by pushing down on the stab to turn it; Cessna has determined that this will crack that stab spar much sooner. We don't let our instructors and students do it. It also deforms the nose rib at the stab root. If any pilot saw how light the structure is in there, he'd never touch that stab again. The forces involved in lifting the nose by puching on the stab are much higher than those in normal flight, since the main wheels are well behind the aerodynamic centre of pressure. Cessna has a Continuing Airworthiness Program that we also follow, and things like engine mount crack inspection at 10,000 hours and every 2000 thereafter is listed; we've found cracks at 7000 hours, and at 10,000 we found five more. The wing spar roots and carrythoughs are to be eddy-current tested at 12,000 hours. We're not there yet but I wouldn't be surprised if we find some small cracks. If you can't find evidence in the logs that the mechanic has been paying attention at least to ADs and SBs, you can expect some expensive repairs. Dan |
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