The International Cessna 170 Association

Hello all,

My Plane...1949 170a #19052

During my last flight, along with an experienced flyer in the co-pilot seat, my pilot door decided to open. A lot of suction to fight don't ya know. In short, this issue popped up 5x's during the 2-hour flight. It kept my co-pilot on his toes.

Has anyone had this problem? I did notice in the 170 parts book, a new interior door latch was introduced at ser #19200.

Any fixes?

Thanks for your response,
J Edmund Taylor

Edmund

Reviewing the parts manual it appears all the parts for the A model and B model are the same. the B model does have an extra spring not found in the earlier IPC. The purpose of the spring is to hold the door handle closed and I don't think help hold the latch. What I think you are seeing is the part number for the entire door assembly changed at 19200 but not the parts inside.

The latches on all the 170 models leave a little bit to be desired as far as I'm concerned. They are very easily broken and after 60 years very worn. They will work OK when it keep after though.

I have no idea why your latch is not being released to hold the door shut. Probably a broken or missing spring. I suggest you study how it is held in and then remove it and look it over. You will most likely have to drill rivets to remove the mechanism as that is how it is held into the door assembly from the factory. Once removed you may see what's worn or broken and make repairs as necessary.

I've had my door mechanisms out several times in the ten years I've owned my plane. I use soft pop rivets to reinstall the mechanism which makes it easier to both remove and reinstall.

Didn't one of our members have an STC to install the later type Cessna door latches in our C-170s?
Sounds like now would be the right time!

blueldr wrote:Didn't one of our members have an STC to install the later type Cessna door latches in our C-170s?
Sounds like now would be the right time!

Yes, I believe John Benham (TX) is the member to which you refer. He had salvaged several sets of 172 door lock/mechanisms and sold them w/paperwork. (I don't know why a STC would be required for this mod, tho'. The doors for 170s and early 172s are identical, and those early 172's qualify for later 172 latches simply under the basis of superceding part nos.)

But John's is an easy route if you can afford it, and don't mind doing the work. It certainly makes a more secure door. I believe Del Lehman also does this mod in his shop.

George,
I am at a loss to remember his name, but didn't our previous maintenance advisor also have an STC for the door latch mod?

blueldr wrote:George,
I am at a loss to remember his name, but didn't our previous maintenance advisor also have an STC for the door latch mod?

Tom Hall? I didn't think so. But using 172 hardware (the rotary-latch type) is a good design and any salvage yard ought to be able to supply damaged doors for the parts.

I just had Del Lehmann install 172 latches on my plane using John Benham's STC and supplied by John Benham. They are a definite upgrade and positively latch until they are released. You would have to talk to Del to find out how hard they are to install. They are not just a drop-in and rivit in place job.

Referring back to my parts catalog, the assembly for the 170a I was looking at, Ser# 19200 on, is a Thumb Latch with bolt, bracket... The illustration shows the latch on the co-pilot door. I assumed the pilot side would have the same parts if it were illustrated.
However, when looking at the door post on the co-pilot side, there is a 2nd vertical slot cut below the Door Latch; this 2nd slot is not cut on the pilot side.
My error in initially describing the Thumb Latch on the door as a Door Latch. (source, Cessna 170a Illustrated Parts Catalog)
J. Edmund

That latch that you are looking at is the lock mechanism that holds the door handle on the out side of the door from being opened effectively locking the door. It in no way actually holds the door closed. The pilots door uses a key and tumbler barrel from the outside.

The sliding, manual, "security" lock on the copilot's door is not fitted to the pilot's door, and in any case, serves no purpose in preventing the door from opening in-flight.

Thank you all for your input. You've given me some ideas to remedy the problem. Joining this club is the best move I could have made.
J Edmund

Edmund I think the first step is determining what exactly is happening to your latch system to make it fail. Work it a few times and observe how if the latch reliably extends to the full out position. I'll bet it doesn't. There are I think 2 original springs, one a larger mouse trap looking thing that moves the latch out and it is probably broke. They are available and there are also instructions ho to make your own. I've not been successful making any.

After removing your latch system you might find additional springs have been added over the years by others. I seem to recall Cessna had an additional spring themselves. Study the parts manual and your mechanism and figure out how it works and I'll bet you can figure out how to add common springs found at most hardware stores to the system to make it work.

This is what I did. I don't have any pictures nor do I exactly remember how I did it and I'd bet the left door mechanism is done differently than the right. Mine work pretty well now.

Doing a search for door spring will reveal the following threads with more info:

http://www.cessna170.org/forums/viewtop ... 60&start=0
http://www.cessna170.org/forums/viewtop ... 44&start=0

Check the "Door Latch Spring Availability" post in the MX Library for sources, prices, and an imaginative alternative.

On the Association's list of STCs, number 49 is Door Latches 150(170). Is anyone familiar with this STC and is it applicable in this situation? Does it replace our latches with the rotary type latches or something different?