Door latch repair

How to keep the Cessna 170 flying and airworthy.

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tshort
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Door latch repair

Post by tshort »

I've read through all the threads I can find on the door latch repair options, and have the door sitting on my bench at home.

How in the heck does the latch come out? It looks like it slides out the aft edge of the door based on all the pictures I've seen, but for the life of me I can't get the exterior latch to fit in there and slide backwards.

Also, it appears that the interior door handle shaft is riveted to the actuator that goes aft to the latch mechanism ... drill out and replace with a rod and cotter pin?

Thanks in advance.
Thomas Short
1948 C170 N3949V
RV-8 wings in progress
Indianapolis (KUMP)
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Bruce Fenstermacher
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Re: Door latch repair

Post by Bruce Fenstermacher »

Door latch.JPG
You must take the door handle off. Take the interior panel off. Then take out the Phillips screws (57) around the outside plate (27) on around the door handle shaft a lift out that plate. Look close behind the control (45) that attaches to the door handle shaft and you will see a very small cotter pin which must be removed from the small pin (55). You probably think this pin is a rivet. This will release the latch from the handle. Looking at the control (45), it will slide out between blocks (25) and must be returned back through them.

Look under your outside handle. There was originally two rivets that must be drilled out which hold the latch mech. in the door. If your latch has been out before these are probably screws. On the door jam itself you will probably find 8 screws but maybe original rivets. 4 of them hold the plate to the door jam and 4 hold the plate to the latch mech. inside. You really only have to remove the 2 on the top and bottom but if this plate is off altogether it is easier to see in the door.

If your door handles paint is something you care about you want to put some kind of tape on it. It is a very very tight fit sliding the handle out but it will come out.

This is how I remember it removing this mech. from 4 different doors more times than I care. But I've sleeped a few night since the last time, I may have forgotten a rivet or screw.
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tshort
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Re: Door latch repair

Post by tshort »

Bruce-

Thanks for the quick reply.

I've done all but remove the pin (55) in terms of disassembly; when you say, "There was originally two rivets that must be drilled out which hold the latch mech. in the door. If your latch has been out before these are probably screws." - are these through the exterior skin of the door just aft of the handle? If so, there were two screws there which I removed. The handle and latch assembly will move, but it seems too tight to push it out the aft side. It is not yet being restricted by the control arm (45) attached to the door handle shaft. Perhaps I need a little inboard pressure from the outside on the latch assembly to help out.

Any other tips?
Thomas Short
1948 C170 N3949V
RV-8 wings in progress
Indianapolis (KUMP)
flyboy122
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Re: Door latch repair

Post by flyboy122 »

It doesn't fall out. Usually it requires some pulling/wiggling. I've never had to pry on it, or really crank on it, but like I said, this is not a precision smooth slide fit.

These things are a real PIA. When you get it out, I would recommend spending some quality really going through the latch and making sure everything is in tip top shape. Replace springs, worn pins, etc... Otherwise you'll end up taking it again. (Which I learned the hard way.)

DEM
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Bruce Fenstermacher
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Re: Door latch repair

Post by Bruce Fenstermacher »

Yes, my mind, and words were foggy. And I was looking at the IPC picture which can screw with anyone's orientation. The two rivets or screws are on the outside of the door skin and go to the sender of the door latch mech.

As stated, this mech. does not just fall out. It is sandwiched pretty tight between the door structure. The two points just discussed, the jam plate rivets/screws and the control pin at the door handle shaft are the only physical restrictions from the assembly being slide out. This is why you want to protect the paint on your handle and do it with something thin cause the handle will be scrapped past the inside of the outside door skin.

Good news is once you get it out, getting it back in is just as hard, but you'll be ready for it. :) And next time you'll be an expert and plan your time accordingly. :wink:
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Bruce Fenstermacher
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Re: Door latch repair

Post by Bruce Fenstermacher »

DEM wants you to make sure this assembly is in top shape before reinstall. Problem is, it is impossible to know, but I'd guess, this Rube Goldberg (https://en.wikipedia.org/wiki/Rube_Goldberg_machine ) assembly is probably in as good of shape today as it was when it was new. At least there is little most could do to improve it. And if you could make it into a precision assembly, it probably wouldn't work. You would be manufacturing most parts if you need anything.

Like repair/replace of the fuel valve and a few other rights of passage to to a 170 owner, when you get this out and back in and it works 75% of the time, you'll have that special swagger only those 170 owners that have done this will have. :D
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tshort
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Re: Door latch repair

Post by tshort »

We removed and repaired the fuel valve 10 years ago, so I'm halfway to the swagger now! :D

I won't be able to attack it again until after Christmas but I will update with pics etc once I get it apart.

Thanks and happy holidays!
Thomas Short
1948 C170 N3949V
RV-8 wings in progress
Indianapolis (KUMP)
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Bruce Fenstermacher
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Re: Door latch repair

Post by Bruce Fenstermacher »

And if you find you do need a part, there are special people who have collected some of these parts, and put them in a plastic bag, and stored them in a special place, with the intention of finding them when someone is looking for something. Of course we don't remember what we have, it's hard enough, impossible really, remembering where we put them. And we can't really evaluate the condition of our parts vs yours to tell you ours are better cause they probably looked bad when they left the factory.

If you need a 'mouse trap" spring and choose not to "upgrade' with ACE Aero springs from your local hardware or the Cessna kit which uses ACE like springs but cost more, I can make you a "mouse trap" spring cheap.
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BWeathered
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Re: Door latch repair

Post by BWeathered »

Here is an alternate method of installation for the two tension spring method of repair that does not require removing the latch from the door. When I took my co-pilot door off, I found the striker plate to already be missing...shows you how much that door gets used and how little attention I've paid to that door jamb! Someone had drilled out all six rivets (4 from plate to door frame and 2 from plate to latch assembly), did whatever repair they did, then left the striker plate off and just re-painted the door jamb. The only two rivets holding the door latch assembly to the door were those two on the outside skin, in line behind the external door handle.

This gave me some unexpected access and got me to thinking, so rather than drill out the last two remaining external rivets and go through the struggle of sliding the latch out of the door, I took a 5" long precision screwdriver with a 3mm straight blade that fit snugly inside the spring coils and I ground a small notch in the middle of the blade. I couldn't find the perfect length spring in a stock size, so I cut about 6 turns off a #27 tension spring and bent the last turn to catch the latch. Had to open up the other end of the spring to catch the moving bar, too. Threading the spring onto the screwdriver helps align it and prevents it from flying away if you miss one end or the other. Engage the inner side of the far end loop on the screwdriver notch and insert. Then just catch the front of the latch frame and push on the screwdriver to catch the moving bar, which you can see with a flashlight. Once both ends are engaged, just pull the screwdriver out. Voila! I fabricated a new striker plate to finish the job.

This might not be the prescribed method of repairing the latch, but it does seem to have several virtues. First, not disturbing the paint on the two rivets that go through the external skin. 2nd, you don't have to remove the inside door handle or the upholstery panel, either, or disconnect the connecting bar from the latch to inside handle (mine was riveted...no removable cotter pin). Same number of rivets to drill out (if mine hadn't already been gone), it's just that they all are on the back edge of the door jamb, so (3rd) they are not as noticeable. I just looked and my pilot side door does have the striker plate with 6 rivets, but I think I will repeat this procedure and (4th) I don't think I will even have to take to door off the airplane.

Hope this is useful!
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GAHorn
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Re: Door latch repair

Post by GAHorn »

BWeathered wrote:Here is an alternate method of installation for the two tension spring method of repair that does not require removing the latch from the door. When I took my co-pilot door off, I found the striker plate to already be missing...shows you how much that door gets used and how little attention I've paid to that door jamb! Someone had drilled out all six rivets (4 from plate to door frame and 2 from plate to latch assembly), did whatever repair they did, then left the striker plate off and just re-painted the door jamb. The only two rivets holding the door latch assembly to the door were those two on the outside skin, in line behind the external door handle.

This gave me some unexpected access and got me to thinking, so rather than drill out the last two remaining external rivets and go through the struggle of sliding the latch out of the door, I took a 5" long precision screwdriver with a 3mm straight blade that fit snugly inside the spring coils and I ground a small notch in the middle of the blade. I couldn't find the perfect length spring in a stock size, so I cut about 6 turns off a #27 tension spring and bent the last turn to catch the latch. Had to open up the other end of the spring to catch the moving bar, too. Threading the spring onto the screwdriver helps align it and prevents it from flying away if you miss one end or the other. Engage the inner side of the far end loop on the screwdriver notch and insert. Then just catch the front of the latch frame and push on the screwdriver to catch the moving bar, which you can see with a flashlight. Once both ends are engaged, just pull the screwdriver out. Voila! I fabricated a new striker plate to finish the job.

This might not be the prescribed method of repairing the latch, but it does seem to have several virtues. First, not disturbing the paint on the two rivets that go through the external skin. 2nd, you don't have to remove the inside door handle or the upholstery panel, either, or disconnect the connecting bar from the latch to inside handle (mine was riveted...no removable cotter pin). Same number of rivets to drill out (if mine hadn't already been gone), it's just that they all are on the back edge of the door jamb, so (3rd) they are not as noticeable. I just looked and my pilot side door does have the striker plate with 6 rivets, but I think I will repeat this procedure and (4th) I don't think I will even have to take to door off the airplane.

Hope this is useful!
YOU.... are a steely-eyed ROCKET-MAN!

Ingenuity!..... The Mother of Ascension!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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BWeathered
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Re: Door latch repair

Post by BWeathered »

BWeathered wrote:Here is an alternate method of installation for the two tension spring method of repair that does not require removing the latch from the door. When I took my co-pilot door off, I found the striker plate to already be missing...shows you how much that door gets used and how little attention I've paid to that door jamb! Someone had drilled out all six rivets (4 from plate to door frame and 2 from plate to latch assembly), did whatever repair they did, then left the striker plate off and just re-painted the door jamb. The only two rivets holding the door latch assembly to the door were those two on the outside skin, in line behind the external door handle.

This gave me some unexpected access and got me to thinking, so rather than drill out the last two remaining external rivets and go through the struggle of sliding the latch out of the door, I took a 5" long precision screwdriver with a 3mm straight blade that fit snugly inside the spring coils and I ground a small notch in the middle of the blade. I couldn't find the perfect length spring in a stock size, so I cut about 6 turns off a #27 tension spring and bent the last turn to catch the latch. Had to open up the other end of the spring to catch the moving bar, too. Threading the spring onto the screwdriver helps align it and prevents it from flying away if you miss one end or the other. Engage the inner side of the far end loop on the screwdriver notch and insert. Then just catch the front of the latch frame and push on the screwdriver to catch the moving bar, which you can see with a flashlight. Once both ends are engaged, just pull the screwdriver out. Voila! I fabricated a new striker plate to finish the job.

This might not be the prescribed method of repairing the latch, but it does seem to have several virtues. First, not disturbing the paint on the two rivets that go through the external skin. 2nd, you don't have to remove the inside door handle or the upholstery panel, either, or disconnect the connecting bar from the latch to inside handle (mine was riveted...no removable cotter pin). Same number of rivets to drill out (if mine hadn't already been gone), it's just that they all are on the back edge of the door jamb, so (3rd) they are not as noticeable. I just looked and my pilot side door does have the striker plate with 6 rivets, but I think I will repeat this procedure and (4th) I don't think I will even have to take to door off the airplane.

Hope this is useful!
Follow-up: Finally had time to get to the airport so I tackled the door latch repair on the pilot side with the door still mounted on the plane. After I had the 6 rivets out of the cover plate (drill the inner two rivets out first, the latch tabs they attach to are less stiff than the door frame itself, then the four at the corners) it took me about 20 minutes remove the old broken mousetrap spring and to install two new springs, and most of that time was spent fashioning the new springs from a couple that were 6-7 turns too long. You may be tempted, but you should not have to bend those two small tabs that attach the cover plate to the latch itself (the first two rivets) if you thread the spring onto a small notched screwdriver, as described above. Cleaned the cover plate and the frame and reinstalled all 6 rivets. Total time about 35-45 minutes just taking it slow in the 90 deg heat and 95% humidity! There is one more downside to this that I hadn't considered before, and that is not removing the latch doesn't give you a chance to clean it thoroughly, but all said, I like leaving the door on the plane! It sure is nice to hear a positive click when the door is closed now!
epeter786
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Re: Door latch repair

Post by epeter786 »

For the folks who have removed the latch mechanism, is anyone riveting the two external ones back in place, or just using screws?

Probably screws to make the repair easier when it breaks next time?
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lowNslow
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Re: Door latch repair

Post by lowNslow »

Mine has rivnuts attached to the latch and uses machine screws in place of the external rivets. This was a previous mod before I owned the airplane but it sure made it easy when I had to do a repair.
Karl
'53 170B N3158B SN:25400
ASW-20BL
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brian.olson
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Re: Door latch repair

Post by brian.olson »

Older thread here, but I need to express my thanks to the forum members for the wonderful suggestion on how to repair a broken door latch spring. I flew 62C from our home field south of Atlanta to Panama City Beach, FL on Saturday as an excuse to get out of town and buy a new t-shirt. After paying for fuel at the FBO and starting the pre-flight for the trip back home, I noticed that the door would not stay latched shut. Busted spring was my first (and correct) thought. Long story short - I discovered that while I could latch the door from the inside with the handle, after a couple of minutes it would pop open again ... so I spent a good part of the flight re-latching the door every couple of minutes before I finally gave up and didn't worry about it any more.

I used the last method suggested in the thread - drilling out just the six rivets on the latch faceplate and installing a hardware store spring. I decided to use a hollow brass tube as the insertion device; a Dremel with a cut-off wheel made quick work of cutting the notch in the end to hold the spring. I ended up only using a single spring as the tension was high enough that I felt two springs would be overkill. Six new blind rivets (.08 each at Aircraft Spruce) and the faceplate was secured back on.

Looking forward to re-installing the door tomorrow and resuming my time in the air again.

Delightfully brilliant solution to this problem, and the photos and description provided helped me worry less and smile more. My many thanks once again for the wisdom of the group.

Brian
Brian
1950 170A
N5762C s/n 19716
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GAHorn
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Re: Door latch repair

Post by GAHorn »

If you want to remain pure as driven snow and original, Bruce F. Will mfr them for you if you specify under the provision of “owner produced parts”.
Pics of tension spring installation in lieu of the original “mousetrap” spring (as in the Cessna Svc Ltr) look like this:
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'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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