Door latch repair

[madpilot]

Well it looks like I have to figure out how go about replace my door latch. The springs seem worn out as well at the door latch itself. I was wondering if it was best to replace it with a whole new system, or try to rebuild what I have. I did some searching on the forums, but I didn't seem to come up with anything.

Larry

[minton]

Convert it to C-150 clutch system. Not very expensive. John Benhams' STC# SA3866SW

[Bruce Fenstermacher]

Larry,

Difficult to say whether you should rebuild or replace. Though it may be simple to replace the system with that of another aircraft you have to ask, simple as compared to what? It may be a simple task for those who do this sort of work day in and out and that are familiar with the tools and techniques required but not so simple otherwise.

Of course the factory system won't just fall out of the door and fix itself either. The door latch system when new is a delicate Rube Goldberg sort of device made of small pins and thin bent sheet metal and mouse trap springs. You've got to wonder how it worked and lasted at all let alone 70 years. Parts are few and far in between but it might be someone has a stash they'll share. Lots of the parts can be hand made again you would have to have the talent to do that sort of thing and also have the temperament to want to repair and perhaps design a slightly better mouse trap.

Chances are, even as weak as these devices are, about the only thing you'll need are some springs. Some of them are still available, there are also instructions to make your own though I've not been successful doing the home made spring thing and I'm a pretty handy guy. Others including me have visited their local hardware store spring collection and with some thought bought springs that when installed, in a different fashion than original, made the system work pretty well. There are a few pictures somewhere here with common local springs installed.

If you have to pay someone to do your handy Rube Goldberg type of work then replacement with another system might be the way to go but there aren't any instructions for that either. The late John Behnam held an STC to do it but I'd doubt it is currently available.

[15A]

Larry,
Both my doors were starting to pop open and refuse to latch sometimes. I pulled the doors and brought them home.
I took one door at a time apart to see what was going on, and it was as simple as straightening some bent parts and replacing the springs. The 140 site has a method to make your own springs.
They've been working fine for 4 years now!

[GAHorn]

Well it looks like I have to figure out how go about replace my door latch. The springs seem worn out as well at the door latch itself. I was wondering if it was best to replace it with a whole new system, or try to rebuild what I have. I did some searching on the forums, but I didn't seem to come up with anything.

Larry

In these modern times it's a common thought when something breaks..."I'll replace it"....which is what you first asked.
Problem is... with these 60 yr old airplanes...you cannot simply go out a buy "replacement door latches". Nor is the C-150 or C-172 system a simple replacement either...it's a modification that requires some skilled sheet metal/structural work.

The later C-172 "rotary gear" system is a better system (and likely why Cessna redesigned this original system which is somewhat "Rube Goldberg" as already mentioned. Even tho' someone had an STC... you can modify your own airplane (i.e. hire someone to to this) and accomplish it with a field approval...or perhaps even get away with merely modifying it and calling it a minor alteration...
...but the simplest answer is to repair your present system.
The springs are available from Cessna if you know what part numbers to ask for. (You said you checked thru these forums and did not find it, but in fact I have posted the info several times in different threads. I'll quit writing and go locate a link or two for you and post it back here with an edited msg.)

Here ya go: http://www.cessna170.org/forums/viewtop ... ch+springs