The International Cessna^® 170 Association

Bruce, I agree. I have seats from a '75 172 in my airplane. They have big square backs that hit the window latches. I can't move the seats past the latches without opening the window first to get the latch out of the way.

First, having newer seats installed as George has pointed out in the past is not something you want to point out to any FAA type.

Second, Having ANY modified seats without the paperwork to back it up could be even worse. The fact that your AI or any AI has passed the annual is not relevant. If its wrong it will continue that way.

If at a later date getting someone into the mix that knows his stuff and is concerned enough to raise the "BS" flag on it then you will then have to comply. You as the owner are responsible for the condition and airworthiness per the FAR's and knowingly operating in that "Unairworthy" condition puts you squarely on the hook for whatever could happen down the road. The FED's don't have any interest in excuses. You could be the next notch in their grip.

Front seat backs support your torso from tilting back under "G" loads and if it were to collapse during a critical phase of flight things could be disastrous. Most field modifications are not looked at by engineers and thus what if any testing was at best the by seat of the pants. That doesn't give me a warm fuzzy.

If it were me I'd change out the seat for a legal one and then change out the window latch by way of either "STC" or "minor modification" to a style that could accommodate your style of seat.

Just trying to be of help

If the underlying seat structure is unchanged I can't imagine that cushion being illegal. It's a minor thing, in my opinion, just like any other trim item. Interior shops make these sort of minor customizations all the time. (Has anyone ever seen "lumbar support"? And it looks as if it'd be a left, front seat.)

Having had that style of seat apart many times I'd bet that the seat back frame has been modified thus my comments.