Door latch design factors.

[woxofswa]

>>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.

[andrejv]

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