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Door latch design factors.

Mike S

Mike S

Senior Curmudgeon
With the current interest in the RV 10 door safety latch, I wanted to start a separate thread to get a group consensus of the design elements that we, the users, find desirable.

There are at least 3 threads going right now with latch designs, and all have good and not so good features (IMHO).

http://www.vansairforce.com/community/showthread.php?t=53564

http://www.vansairforce.com/community/showthread.php?t=53151

http://www.vansairforce.com/community/showthread.php?t=53090

Here is what I have come up with so far.

I would like a latch that is totally automatic, and is tied into the existing door handle for operation. One point of operation, not two like the existing factory design.

I would like to see the safety latch located at the middle to rear of the door, this is where the problem is. The latch in Verns thread is simple and elegant, but I am concerned as to the fact it is at the front portion of the door. I do like that it resists upward movement of the door, not just outward. But, as far as I know, all door losses have come from a lack of rear pin engagement.

I would like a latch that can be retrofitted to an finished door, and not look like it is an afterthought/band aid fix.
And that it can be utilized in a door that is upholstered.

And I want to see factory support/approval for the design, so that there wont be any loophole for an insurance co to claim that the "mandatory factory approved" safety was not installed, therefore your claim is rejected.

Please jump in here, and add any design points I have missed.
 
I really like Vern's solution to this issue. im not really sure how the inside of the panel looks ( i havent even ordered a kit yet) but if there is enough room, im sure it could be setup with a push rod to the rear and have a secondary latch back there.
 
one size fits all latch system?

Mike,
The criteria listed seems to eliminate the ones listed except for Greg Hale's.
This solution can be retofitted into Hendricks, Coss or stock door latch designs. Impact to the builder is nominal since it's installed on the inside of the door making it easier to cover the modification up with a door panel or material.Gregg has provided a blueprint detailing the design including the geometry needed to make it work. He has a working unit so it's not just smoke here. Finally, after seeing the rest of his site concerning his RV-10 (his plane is off the hook!) I feel he has developed the simplest yet most universal solution. Just my opinion.

Don Orrick
N410JA
40010
 
I've been giving this quite a bit of thought recently, as well as others. While a solution that was internal to the door would be most aesthetically pleasing, I do have concerns.

The latch would require a hole in the cabin cover and/or middle cabin deck that is outside the door seal. My concern is that water would run down the door gutter into the opening. Just like the factory solution, water doesn't really have a place to go.

With all the brainstorming going on, I'm sure there will be a more elogant solution soon.

bob
 
rleffler said:
With all the brainstorming going on, I'm sure there will be a more eloquent solution soon.

bob
Click to expand...

That is EXACTLY why I started this thread.

The collective VAF mind can be pretty amazing when it comes to problem solving.
 
midwest rv-10 said:
Mike,
The criteria listed seems to eliminate the ones listed except for Greg Hale's.

Don Orrick
N410JA
40010
Click to expand...

The criteria is strictly my opinion so far, I am asking for input and constructive criticism from the VAF group mind, so as to develop a true criteria for all, or at least most of us.
 
Mike, Since we seem to both agree on what we would want in a redesign
I offer my first post as my "input and constructive criticism from the VAF group mind". Unfortunately, the fourth item on your criteria list is not obtainable since this issue is resolved as far as the factory is concerned.
But you need to add to the criteria that it can be retro fit to any style latching system.


Bob,
After reviewing the pictures of Greg's latch system it appears the center door pin is actually inside of the door seal, in fact it's inside of the canopy, basically inside the airplane.

Don
 
midwest rv-10 said:
Unfortunately, the fourth item on your criteria list is not obtainable since this issue is resolved as far as the factory is concerned.

Don
Click to expand...

Don, you know the factory obviously used the latch developed by a builder shown in this thread.

They can and do respond to builder input, but as can be seen the response time may be a bit long----

I am hoping that the group can come up with a design that the factory will acknowledge as satisfactory at a minimum, and preferable substitute for the current "mandatory" unit.

Of the four factors I mentioned at the start, I suspect the buy-in from the factory may end up being the most critical in the long run.

Unfortunately, it will probably take a crash or two, and the almost inevitable lawsuit to prove if that is a correct assumption.
 
What about using Vern's system with two attach points per door???

We could use his standard position for the forward point...

For the rear point, we can mount another factory door handle mechanism (minus the door handle) near the aft edge of the door. Like I said, there won't be a handle.

It's primary purpose would be to convert the horizontal movement of the rear pin into an arc for the aft striker.

My airplane will only fly as far as I can throw it, so I don't know. But I think it's possible to do if we would use a toothed push rod to run through both the forward and aft mechanisms. It would operate both mechanisms in unison.

I probably did a lousy job describing that. (Well all except for the part about having an airplane that will only fly as far as I can throw it. That part was pretty clear.)

Phil
 
For the record, I think my 12v door pin idea isn't nearly as nice as Vern's solution. My idea was heavier, required removing some strength from the mid-fuse decks, and didn't oppose vertical door movement.

Like Mike suggested though, I'd like to see it moved a little further aft.

But I humbly request that my idea be thrown out of the running... :) There are some far superior ideas here.
 
Door Flex

I have been wondering how much the doors flex when latched and pushed outward in the middle. I tried on mine with the Metal pin recepticles and it only will flex 1/8 to 3/16 " no matter how hard I push.

Do some doors have more flex than that? Could the flex be the problem asside from not latching the rear pin?

Inquiring minds want to know

Gary Specketer
 
Latch

Verns idea is functional and simple. I have the Hendricks locks and putting the lock handle on is a sinch. The receiver Matt made will work perfectly.

Here is a lesson I learned last week in over engineering. The hendricks door latches are flush on the exterior and have a lock. Internally the lock mechanism is on the horizontal center line which interfers with the internal tube mechanism. I spent 3 days building a lot of crazy linkage combinations to get this to work. Although I made it work I did not like the reliability prospects of the linkage. after stepping back a couple of days I returned to shop and started engineering this again. The solution ended up being simple. After spending many hours trying to build a linkage system that went around the lock the answer was just to move the lock.
 
Cirrus & Trinidad

I was in the FBO shop today and there happened to be two quasi-gull-wing doors in there: a Cirrus and a Socata Trinidad. Of course, the Cirrus has forward rather than top hinges. Still, it has a two pin system facing aft.

More interesting was the Trinidad door system, of which I could only see the exposed features. No pins, but two forward and aft latch points in the bottom of the door. The door has two "hooks" on it that face outboard, and as the door drops into the sill, the hooks latch into two "eyes" that pop up out of the sill. As the single door handle inside is rotated forward, the two eyes pull the door via the hooks down and lock in place. I couldn't see the inner workings, but it looks awfully simple. Not easy to retrofit, but for those of us still building, very attractive and should be pretty simple to emulate. I can get pictures if someone wants.
 
With the current interest in the RV 10 door safety latch, I wanted to start a separate thread to get a group consensus of the design elements that we, the users, find desirable.........

.......... But, as far as I know, all door losses have come from a lack of rear pin engagement.

**** Purchase a proximity switch and connect it to warning light. Most modern Avionics will handle a discrete input you can configure. If your avionics does not have that capability, then add a warning light to the instrument panel. *****

P.S. Might cost you $30.00.
 
bruce1369 said:
**** Purchase a proximity switch and connect it to warning light. Most modern Avionics will handle a discrete input you can configure. If your avionics does not have that capability, then add a warning light to the instrument panel. *****

P.S. Might cost you $30.00.
Click to expand...

Bruce, thanks for the comment. I see you are an 8 guy, so you probably aren't aware that there is already a prox switch and warning light from Vans.

Problem is not everyone installs them, or maybe not everyone pays attention to them??

The idea of the safety latch is, IMHO, to keep the door on the airplane if other systems---including the organic system at the stick----fail in the door latching arena.

Thanks for the input, and thanks to all who have contributed to this thread.
 
Hi Mike,

A mate of mine in Temora, Australia has built four RV10's - and on the last two he has used my latch idea. He has refined the design and his latches are more slim-line, but the idea remains the same. Recently, one of these planes took off and the pilot forgot to close his door handle - he was focused on closing his daughters side but forgot his. Took off and guess what happened..... nothing! He noted increased noise and then realised he had not latched his side - returned and landed safely.

I reckon that the wheel has been invented... this system works, the latch is automatic, the rear pin always engages, its in the middle of the door... rest my case!!

Cheers

Andre
 
andrejv said:
Hi Mike,

A mate of mine in Temora, Australia has built four RV10's - and on the last two he has used my latch idea. He has refined the design and his latches are more slim-line, but the idea remains the same. Recently, one of these planes took off and the pilot forgot to close his door handle - he was focused on closing his daughters side but forgot his. Took off and guess what happened..... nothing! He noted increased noise and then realised he had not latched his side - returned and landed safely.

I reckon that the wheel has been invented... this system works, the latch is automatic, the rear pin always engages, its in the middle of the door... rest my case!!

Cheers

Andre
Click to expand...

Andre, Congrats on the save man!

Can you post some pictures of the new design?

I want to thank you for working on this years before the crowd. You are on the cutting edge mate!
 
Larry, this is the original safety latch from acouple years ago, here is the link once again. It has been posted before, but as the thread grows, things tends to get lost...

As can be seen, it is obviously the mother of the Vans SB latch.
 
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andrejv said:
Hi Mike,

I reckon that the wheel has been invented... this system works, the latch is automatic, the rear pin always engages, its in the middle of the door... rest my case!!

Cheers

Andre
Click to expand...

Is it still a two step release, or is the safety now released by the factory handle??? Like in this post
 
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>>More interesting was the Trinidad door system, of which I could only see the exposed features. No pins, but two forward and aft latch points in the bottom of the door. The door has two "hooks" on it that face outboard, and as the door drops into the sill, the hooks latch into two "eyes" that pop up out of the sill. As the single door handle inside is rotated forward, the two eyes pull the door via the hooks down and lock in place. I couldn't see the inner workings, but it looks awfully simple.<<


I owned a Socata for ten years. The first moment I sat in the RV-10 demonstrator, I thought that the door latch was much better in the Socata and that the Van's door handle looked cheesy and homemade.

I don't believe that there has ever been a door pop open in a TB that wasn't due to simply not being latched in the first place. They don't have a door warning light (at least mine didn't). It is designed so that even with the door down, if the handle isn't latched the door is slightly open so as to make it more obvious that it isn't latched.

I do know of a case of a Socata that lost a door that wasn't latched and landed safely and another that opened on takeoff and the guy yawed the airplane enough to fly the door back down.

Their system is easy from the door aspect, but more complex in the fuselage. The inside handle is much lower and would conflict with the seat so the inside handle is forward of the door and connected by rod linkage. The advantage of that is that the handle is more in view of the pilot. Their lock is a simple cam tooth that stops actuation.

I have thought about buying the mechanism from a salvage TB and installing it in my 10. Buying the parts from the factory would be pricey in my opinion, but I am sure the system could be made to work.
 
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RV10 door latch

Here are the photos of the modified version of my latch. Simon Pike from Temora, Australia, has built more RV's than just about anyone and he is a fantastic person and a perfection builder to boot. He has (as usual) made things simpler and yet just as effective.

This photo shows: the base plate with two nut plates which fits along the inside of the bottom of the door; a chunk of steel that has been shaped up to make that 'latch' part and a thread has been tapped into the rear end to attach an AN bolt, the head of which has been removed; a metal ferrel through which another AN bolt runs; a spring which pre-loads the latch system and two pieces of angle which support the hinge. Note that the AN bolt that is attached to the 'latch' section is welded to the ferrel.

http://img202.imageshack.us/i/imgp16272.jpg/

This photo shows the head of the AN bolt sticking out through the door and its used to de-activate the latch when opening the door from outside.

http://img269.imageshack.us/i/imgp1616mp.jpg/

This shows the 'head' of the latch with a cover masking the hinge section.

http://img211.imageshack.us/i/imgp1619.jpg/

Lastly, we see the 'head' section engaging a piece of angle which has undercut and is riveted to the deck.

http://img231.imageshack.us/i/imgp1617.jpg/

The system remains 'two system' ie the pre-existing Vans latch plus this safety feature. Point is though, as long as you pull the doors closed prior to T/O, they will not come open, even if the Van's latch is forgotten!!! (and the rear pin ALWAYS engages!)

Regards

Andre
 
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