The International Cessna 170 Association

Hi All,

The door latches on my 170 keep getting stuck. Specifically it's the latch itself. When I open the door, it's sticks in the retracted position. If I pry gently with a screwdriver it pops back loose. I played around with it today, and it works fine (springs back) until so far in the travel at which point it hangs up. It almost seems like the latch is going overcenter. I searched the forum but didn't find anything.

Thoughts?

DEM

Hello Flyboy,
This just goes to show that we all have the same problems with these fine airplane some time or another. Do a search on Door latch springs and you will see some good responses/solutions to your dilemma. I started that post back in 2012 and was just searching it again tonight, as my other door just did the same thing and I wanted to do a refresher course. Just goes to show you that this forum is worth it's weight in gold!

Here's the link--> Door Latch

Does anyone know the disposition of John Benham's STC #SA3866SW to install Cessna 150/152 type door latch systems?

Does anyone have a copy of the STC or a pats list?

Abe wrote:Hello Flyboy,
This just goes to show that we all have the same problems with these fine airplane some time or another. Do a search on Door latch springs and you will see some good responses/solutions to your dilemma. I started that post back in 2012 and was just searching it again tonight, as my other door just did the same thing and I wanted to do a refresher course. Just goes to show you that this forum is worth it's weight in gold!

Here's the link--> Door Latch

Hi Bill,

I found all the spring threads, but they seem to pertain to broken springs and replacements. Is that what causes the latch to hang up? There is definitely spring tension on the latch, it just seems to go "over center" and hang up.

DEM

bagarre wrote:Does anyone know the disposition of John Benham's STC #SA3866SW to install Cessna 150/152 type door latch systems?

Does anyone have a copy of the STC or a pats list?

That STC was incomplete and missing all the documentation. Jim Wildharber attempted to obtain it on behalf of TIC170A and gave up dealing with him over it.

George, do you know whether or not an STC that is not supported any longer can be used as a basis of approval for a Field Approval for the same mod?

I have the Benham door latch STC and would be happy to share.

Many years ago I had the same problem of a latch over centering. Can't remember exactly what I did but drilled a hole and put a small # 4 or # 6 bolt or maybe it was a rivet in a place that became a hard stop for the latch so that it could not pass over center. If you take the latch out and study it I think you will see a way to do it.

hilltop170 wrote:George, do you know whether or not an STC that is not supported any longer can be used as a basis of approval for a Field Approval for the same mod?

I have the Benham door latch STC and would be happy to share.

I believe that a valid STC might provide some useful data for someone wishing to obtain approval. ( I also believe valid STC's these days usually include proper instructions. I believe the problem is one of validity. FAA-FSDO-SAT, who had originally approved John's mod, had no copy of the approved parts list, nor did John, therefore the validity was in question...if I recall the problem correctly. Jim might have better recall on the matter since he was the person negotiating. I.E., why obtain something from an estate that has no approval-basis?) <EDIT> Bruce emailed me and expressed his belief it was the exhaust STC which was missing the parts list.

Thinking it thru... So, if the STC is no longer/never was valid... and if someone has latches installed using unapproved/invalid approval.... would distribution of the invalid documents be useful? or merely interesting?
I personally believe this to be a minor alteration and suspect a great many IA's do as well if found installed in an airworthy manner. (In fact, the window-latch if converted from the scissor-latch to the Ford vent-window latch, probably should raise more eyebrows as regards documentation validity. In that case, Niagara (the folks who also mfr the starter-clutch) has offered the Ford window-latch for many years claiming FAA-PMA approval basis for 170's even tho' no 170 ever had that style of latch. Their applicability-sheet still makes that claim. I doubt many inspectors would declare such mods as major alterations.)
Anyway, if you have the documentation Richard, ... sure, go ahead and share it....especially if it includes instructions. A valid STC will not be applicable except for those aircraft to which it was assigned by the STC-holder. Keep in mind that J.D. Benham, Jr. may be interested in anything regarding this discussion. Dorothy and he both live in Blanco.

Roesbery wrote:Many years ago I had the same problem of a latch over centering. Can't remember exactly what I did but drilled a hole and put a small # 4 or # 6 bolt or maybe it was a rivet in a place that became a hard stop for the latch so that it could not pass over center. If you take the latch out and study it I think you will see a way to do it.

Ok thanks. Sounds simple enough. I just wanted to make sure I wasn't missing some routine adjustment before I took the latch assembly out.

DEM

These latches are a Rube Goldberg device if you ever saw one. When they where new the probably did not work well. Or at least very well long. Taking them out and looking them over while they operate and tweeting them here and there is the only way to get them working.

Didn't the TIC170A maintenace honcho before GAHORN have an STC for installation of the later style Cessna door latches?

(My memory isn't improving at all as I, so gracefully, age.)

SA3866SW appears to still be valid with the FAA

http://rgl.faa.gov/Regulatory_and_Guida ... t=sa3866sw

Woudln't it have been revoked or something if they decided it was no longer valid?

Just got my latch put back in using the double spring method that Joe talked about and it works well, however it's doing what flyboy's original question was about...sticking occasionally (only when the exterior door latch is used). Roebury is correct that it gets over center and sticks, but it's easily (albeit annoying) put back into it's proper position with a swipe of the finger on the back of the latch. And the best fix would be the bolt talked about also, but I hate adding extra weight to my airplane

Bruce you're correct in describing that system as Rub Goldberg set up, but I think you're being awful nice as I had a few other names for the engineering genius who decided that it took some 50-pieces (I'm guessing) to allow a person to open and close a door!

But, all in all it's still the best looking and flying airplane around as far as I'm concerned.

David, Bruce, George and I have been having email discussions regarding the Benham STC's for the door latches. Richard if you do have the installation instructions I would like a copy since, now that I have had time to think about it, I don't believe John ever gave me any written instructions. He did tell me how to modify the in door mechanism to allow the bar (?) in the door to only extend so far into the enclosure in the door post. I believe my IA just used common sense and did the installation without having specific written instructions.

To avoid problems I inform passengers that only I will operate the interior and exterior latches. Yes it is "doorman" service.