C172 Door Bolt Adjustment

[Skymac]

I’ve got a M Model with the 1 way rotary gear system that is mounted in the fuselage with the bolt that is in the door.

I have a issue where in the neutral door handle position, the bolt does not extend far enough and only barely catches the gear in the door post which causes the door to often pop open any time the wind is blowing hard, etc.

Is there an adjustment on this or does anyone have any tips with this particular system? The service manual does a poor job for talking about this. I’m wondering if new spring ls would help this, but I don’t think so. Maybe some shims but I’m not sure how that would work. I only need it to extend about 1/16” to get a good capture on the rotary gear.

 

[Bell206]

does anyone have any tips with this particular system?

Is this a new problem or has the door always been this way?
From the outside, is the door centered in its opening?
Is the latch bolt centered in the striker plate on the door post?
Is the interior handle indexed per the manual and S/N?

 

[Dan Thomas]

I’ve got a M Model with the 1 way rotary gear system that is mounted in the fuselage with the bolt that is in the door.

I have a issue where in the neutral door handle position, the bolt does not extend far enough and only barely catches the gear in the door post which causes the door to often pop open any time the wind is blowing hard, etc.

Is there an adjustment on this or does anyone have any tips with this particular system? The service manual does a poor job for talking about this. I’m wondering if new spring ls would help this, but I don’t think so. Maybe some shims but I’m not sure how that would work. I only need it to extend about 1/16” to get a good capture on the rotary gear.

I think that pin that goes through the plunger might be broken or missing. IIRC, one of the springs rides on it.

 

[Skymac]

I’ll give that a look see on that pin. Otherwise it functions correctly. It is properly indexed.

We changed the old hinges with new McFarland hinges. The door fitment is better than with the old, original hinges though. Good alignment all the way around. The old hinges were sagging from being worn causing the door to graze the bottom skin.

 

[Bell206]

We changed the old hinges with new McFarland hinges.

Did the latch bolt issue become noticeable after the hinge change? Once you verify the entire latching mechanism is serviceable, reshim the striker plate on the door post to get proper bolt engagement. You can use washers or shims and is usually a requirement if you change hinges or replace doors. I believe its also mentioned in the mx manual as well.

 

[Dan Thomas]

I believe its also mentioned in the mx manual as well.

This. There are several free versions of online service manuals. They might not be the most recent revisions, but they are far better than SGOTI opinions when it comes to fixing anything.

 

[Skymac]

Did the latch bolt issue become noticeable after the hinge change? Once you verify the entire latching mechanism is serviceable, reshim the striker plate on the door post to get proper bolt engagement. You can use washers or shims and is usually a requirement if you change hinges or replace doors. I believe its also mentioned in the mx manual as well.

We have the service manual and hasn’t really said anything of the such, beyond indexing the handle. I can’t shim the striker side because that would make it further from the bolt unfortunately, I’ll dig it apart next week. Just wanted to get some other ideas because I adjusted the rotary wheel after the hinge replacement thinking that would make it better, but then we saw the bolt just needed to stick out a hair further.

It certainly happened after the hinge change, although what’s funny is the door fit terrible with the original hinges, it’s so much better now, fits like a glove.

 

[Clip4]

Some times what happens is the door is not shut enough and the operator forces the door handle bending a rod connecting the handle to the door latch mechanism.

Usually the rod can be straighted.

 

[Dan Thomas]

Some times what happens is the door is not shut enough and the operator forces the door handle bending a rod connecting the handle to the door latch mechanism.

Usually the rod can be straighted.

That won't affect the spring-loaded neutral position of the plunger. It will prevent the plunger from fully locking the door. BTDT. His problem is within the latch assembly.

 

[Bell206]

I can’t shim the striker side because that would make it further from the bolt

You lost me. The striker plate is on the airframe not the door. If you shim out the striker plate it gets closer to the door, ie., the bolt. Pic below #60/61. 2nd pic is the blip from the service manual on shimming the striker plate. While the book calls for shim, washers can also be used. Perhaps you are talking about something else???

 

[Skymac]

Here’s what I have. I have 3 different airplanes and not striker as in Area B of that’s pets manual.

 

[Skymac]

 

[Skymac]

 

[Skymac]

As you can see here the bolt needs to extend out about 1/16 for a perfect engagement.

 

[Bell206]

not striker as in Area B of that’s pets manual.

I screwed up. I sent you a diagram of the bagg door striker.

But something doesnt look right in the bottom pic. Maybe its just the angle. Are you sure the new hinges are on correctly and the door has equal spacing around the entire periphery? Did you repaint the door after the new hinges?

EDIT:
Is it possible when installed new hinges door was pushed forward a bit?

And you've confirmed the latch mech is good with proper bolt travel?

Perhaps remove the aft rotary clutch assy and see if its been modified. If not try shimming the assy forward and check without trim installed.

 

[Dan Thomas]

The rotary clutch installation looks fine to me. The plunger is just not sticking out enough, and that is caused by some fault in the latch assembly in the door. It's not neutralizing properly.

The whole arrangement is a bit sketchy and always was. Those doors are famous for popping open when the airplane is tied down out in the wind. The wind rocks the airplane, which distorts the fuselage structure and alters the doorframe shape, lifting the aft end of the door so that the plunger loses its engagement with the wheel. Some owners reach in through the baggage door and fully latch the pilot's door, then lock the baggage door. Door stays shut (and locked) that way. Much harder to break into, too. The door's keylock just grabs the external latch handle to keep it from being pulled.

The 182RG's doors sometimes pop open when the airplane is on jacks. The doorframe flexes as the jacks lift the airplane ahead of the normal CL.

Cessna fixed this crap in the restart models. It was part of the empty weight increases.

 

[Dan Thomas]

Oh, and one more thing: DO NOT oil or grease the latch. That attracts dust and creates sticky sludge that causes plenty of latching hassles. If one takes the latch out to fix stuff, clean it all off and leave it it that way. If one just has to lube something, use paraffin. Wax, like a candle. It doesn't attract dust. A bit of it on the ramp of the plunger will ease locking.

The AD on Cessna legacy seat rails and rollers and lock specifically forbids any lube on the rollers, particularly. Run them completely clean and dry. The only thing Cessna will recommend is paraffin on the underside of the seat rail flanges, to stop galling of the aluminum rail against the aluminum roller housings. Makes the seats slide nicely. From a legacy 172 manual:



Note their recommendation of lubing the latch with GP grease. I have had to clean a lot of that gummed-up stuff out of latches.

 

[Bell206]

The plunger is just not sticking out enough

Is that what the pic in Post #14 is showing?

 

[Dave Theisen]

As they say, “When one door closes, another one opens. Other than that, it’s a good Cessna.”

 

[Dan Thomas]

Is that what the pic in Post #14 is showing?

Yup. The plunger should almost touch the bash plate on the doorframe as the door closes. Someone might have ground it off a bit for some reason, instead of fixing it properly. You find such stupid stuff on 40-year-old airplanes.

 

[Skymac]

I’ll reply back with the fingers of the inner door latch mechanism once we tear into it. I just wanted to make sure I wasn’t missing something obvious.

No we didn’t repaint they door. The hinge job actually went very smoothly and couldn’t have been a more perfect fit.

Word to the wise though, don’t buy hinges thinking they are a perfect fit themselves. I was not expecting to beat the fire out of my brand new $$$$ hinges to get a good fit. Doesn’t give a person a good feeling when you need to stand bending them.

 

[Dan Thomas]

Word to the wise though, don’t buy hinges thinking they are a perfect fit themselves. I was not expecting to beat the fire out of my brand new $$$$ hinges to get a good fit. Doesn’t give a person a good feeling when you need to stand bending them.

Not surprising. The door seals available now seem to be either thicker or stiffer than the originals, making the door hard to close. We had a 172 that was stressing its hinges something awful just trying to get the doors shut. You could see the doorpost and skin distorting as the forward half of the hinge pulled it outward. I finally made some aluminum shims to put under that forward half; made the door fit just right. Better than starting cracks. There was a serial number range in the mid-70s that had doorpost cracks showing up at the lower hinge; there was a service bulletin on it, and sure enough, we had one, and had the cracks. Got to pull the side panel out of the airplane and look through the access holes in the doorpost. The post would crack in its bend radius. Hinges were pulling on it.

 

[Bell206]

Doesn’t give a person a good feeling when you need to stand bending them.

To give you some positive reinforcement, tweaking and/or shimming new hinges is just part of the process. Those aircraft are hand made and no 2 are exactly a like. Throw in different operational histories and each airframe develops its own "set." The fact you matched the existing paint stripes after a hinge change was pretty good. However since it has been noted above your latch is not operating properly, you need to get that fixed and hopefully wont require another tweak to those hinges. With some aircraft, door/latch fitting can be a rather enduring process with a little finesse and on occasion the need for a BFH.