REFLECTOR: Unexpected door opening

[Brian Michalk]

Al,

Excellent post.

I never did like the passenger latching mechanism, and now that the 
plane is out for a while, I might change it. Could you send some 
pictures of your push button design?

Al Gietzen wrote:
>
> Here are my replies and further thoughts on the door issue.
>
> Certainly, with the front hinging, Rodney has addressed the root cause 
> of the dangers of our standard door design. It is a design that would 
> likely never make it in the world of certified airplanes. However; I 
> think the existing door, and door frame configuration does not lend 
> itself well to front hinging; and is a major rework. The existing 
> latch design is plenty robust; it just needs to be insured of being 
> fully latched when the plane is in flight.
>
> Dennis: I would not recommend beefing up the hinges or hinge mounts. I 
> suspect that I would have been in a lot more trouble had the door not 
> departed the airplane. Of course, departing the plane could result in 
> prop damage, which could also be very bad. So the bottom line is that 
> this door design *_must not_* open in-flight.
>
> Larry: Your safety latch is eloquent in its simplicity; and very 
> easily verified visually. (I’ll admit it doesn’t appeal to my sense of 
> sophisticationJ; but I’ll never argue form over function)
>
> I did not install the automatic lock assembly provided by the factory 
> for design reasons as well the necessity of needing two hands to open 
> the door (at least that’s how I saw it). On the passenger side I made 
> my own design of an automatic lock which requires pushing a button 
> just behind the handle to release it and allow the handle to be pulled 
> back. I didn’t do that on the pilot side because of the need to unlock 
> from the outside – instead I added a second spring to the over-center 
> linkage to provide more force holding the latches in place. For the 
> first 50 hours or so of flight I monitored the handle to insure there 
> was no sign of movement during a flight. There never was; so I gave it 
> no further thought.
>
> My opinion is that it is very unlikely that any of these door opening 
> incidents occurred as a result of a failure of a fully latched 
> closure. Even a simple warning light on the panel that the pins are 
> not fully inserted would be an effective deterrent. In 20/20 
> hindsight, I reflect upon the time and effort I put into design of the 
> electrical system, and engine systems, to eliminate potential 
> single-point failures; but didn’t consider sufficiently the need for a 
> warning if the doors were not fully latched. The checklist, and a 
> glance at the handle isn’t enough.
>
> Al
>
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