REFLECTOR: Unexpected door opening

[Terry Miles]

Al,

 

I am not sure I can contribute directly, but I have this to offer in general
on doors.  M. Collier as part of his long list of enhancements beefed up the
cabin ceiling with a layer of carbon fiber.  If I remember he thought this
necessary for ground-based gusty winds acting on an open door on the ramp.
Engineering at FedEx made a big point about cargo doors and gust limits
beating the crap out of hinge mounts and door hardware.  

 

I  didn't use the factory cylinders.  Instead we used McMaster Carr
cylinders that mechanically lock in when the door is fully  open.  Later,
and because of fit issues, the McMC 90 lb cyl were replaced with lighter
ones.  My door D tube which is hollow and had the cylinder mount surface was
cracked with the strain.  I squirted in a syringe or two of balloon in that
corner the make the D-tube solid at that point.

 

I drilled for #10-32 countersunk hinge screws. (as I recall)  That they are
fully seated and tight is  a preflight item.  They have loosened up over
time.  I used blue lock tite at some point after I was flying.  

 

On the perfect door when closed:  The door and the frame will mate perfectly
and hinges are at equal stretch/compression.   When the bayonets go into the
receivers there are no changes to the sentence before.  I don't have that.
I think the door very likely puts a side load on the hinge faces when I jam
it into the door frame.  The frame and the bayonets line up pretty good.   I
used the factory door mechanism, but on the pax door I had a monkey with the
lateral barrel and the pull up pin so they would contact each other  at 90
degrees or so.  Before the adjustment,  I could rotate the handle w/o
lifting up on the pin.ya  know the two-handed concept.  I hope this can add
to things.  Like Chuck Jensen I have bayonent activiated door lights for
both doors bounted right in prime panel real estate and "door pins and
lights" are on my before takeoff check.  

 

Last.  They leak.  Trying to install door seal material gives me headaches
on the latch and closure issues.  

Best regards,

Terry

 

PS:  I have a Marine story on doors.  I was co-pilot in the B747.  We had
flown a whole airplane full of Marines from Korea back to some army post in
KY.  They were all going on leave.  These were just kids most of them and
with all their stuff in sea bags which seabags  were locked in a lower belly
and we could not get the door open.  The skipper was a wimp.  He called the
company and of course they said to ferry the airplane to St. Louis for
repair and leave these young Marines without their luggage.  I walked up to
this NCO with stripes up and down his sleeve whose stuff was also in the
belly bin, and said something like "Geez, I am sorry Sargeant.   If I were
in charge I'd just tell to you take a half dozen guys and "just get that
door open."  Without batting an eye he said:  "Sir it would only take one
Marine to do that."   I would like to think somebody got those bags to their
owners, but I'll never know.  

 

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Al Gietzen
Sent: Tuesday, June 02, 2009 14:54
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Unexpected door opening

 

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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