REFLECTOR: Unexpected door opening

[Jim Agnew]

Al,

There are several failure modes for the door latches.  First the tubes that accept the latch pins could fail I.E., part from the fiberglass.  Second the latch pins may not be deep enough into the tubes so the stress is on the flat portion and not the tapered part that will try to push itself out. Third the latch pin can unscrew from the push rod (I know one of mine did even with locktite on the threads, I now use RED Locktite on them).  

I have auto locking so closing the latches automatically locks them and you must pull up on the door lock before you can move the handle.

As far as the door warning switches go I only have one in the forward center pin location with a nylon mushroom button that activates a roller micro switch.  I know a lot are in the bottom tubes with wood rods that can swell from water and in the perfect place to collect dirt that can jam them.  

Just food for thought.

JIm
 
James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying




________________________________
From: Al Gietzen <ALVentures at cox.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Friday, June 5, 2009 1:48:33 PM
Subject: Re: REFLECTOR: Unexpected door opening


And for those who at the end of your personal deliberations who would still opt for the gull wing, would something as simple as a deadbolt (weighing only a few ounces) serve as a fail-safe back-up to the traditional lock assembly?  Thanks for your thoughts.
 Robin 
Robin;
 
My thought is that we essentially have 4 ‘deadbolts’ in the current configuration.  We simply need a ‘dead sure’ way of knowing they are in place.
 
My further observation is (added to by my experience flying home with a temporary door) that net outward forces on the door in flight are relatively small – at least compared to the strength of the four latches. I think there is likely some negative (outward) pressure over much of the door, likely stronger toward the front edge, and some positive (inward) pressure in the area of the strake extension, and its junction. 
 
I have no idea if there are forces due to small distortion of the fuselage during flight that may work to move the latch pins out of the tubes, but it is not impossible.
 
FWIW,
 
Al
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