Thu Jan 05, 2017 12:58 pm
Congratulations.
Pre-purchase inspection for the older 172 is straightforward, but should also include a VERY thorough check of front and especially rear wing attach fittings and surrounding structure at the wing root. You must remove the (troublesome) metal fairing strip between wing and fuselage. You are looking for any signs (in the areas you can see) that there might be corrosion inside the fittings and spacer blocks and stuff where you cannot see it, A good friend and experienced IA mentioned to me that there have been cases of corrosion in the rear spar fittings inside the fuselage where you cannot see it, in the aluminum blocks or spacers. You cannot actually see the problem with the wings mounted on the airplane, but sometimes you can see small "ends" of corrosion that have migrated out into an area that you can see. It's a pain in the butt, and nobody wants to do it, but this is what holds the wings on the airplane. The problem is that the structure inside the fuselage (the front and rear spar carry-through) are channels that you cannot see inside.
If the airplane was kept in a temp/humidity controlled sealed hangar in Saudi Arabia since it was new, this will likely not be necessary. If it has lived in the environment shown in the photo you provided, that's a different story. Cessnas and most other production airplanes are not very well sealed against water incursion. They just didn't have any concept that that airplane would still be flying actively 60 years after it was built. If they had, there would be three times the number of inspection panels, you'd be able to get to the !(#*$% fuel selector valve, etc.
The wing root "cover" strip on most average 172's out on the ramp seals the gap well enough to keep a Hippopotamus out of your wing root, but water, dirt, etc. gets in there routinely. Over 60 years, the main wing structural attach fittings (and plenty of other stuff) can get corroded. Very few people care enough to think it through and put some sealing tape, or put fresh rubber channel in that actually seals. It's the top of the airplane, and the slight dihederal angle of the wings will cause water to flow toward this gap.
Last edited by
EZFlap on Fri Jan 06, 2017 2:37 pm, edited 1 time in total.
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