REFLECTOR: Unexpected door opening

[Al Gietzen]

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
sophistication:-); 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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