REFLECTOR: 165 kt Gear Extension Speed

[Chuck Jensen]

Pat,

Your efforts at beefing up the gear doors falls under two inviolate
rules.

1.	The rule of unintended consequences.
2.	No good deed goes unpunished.

Chuck
Do Not Archive

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Pat Shea
Sent: Monday, December 05, 2005 2:32 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: 165 kt Gear Extension Speed

Caution, long gear door story follows:

 Knowing that losing a gear doors is potentially (most
likely?) a disaster of the worst kind in pusher, I
decided to beef mine up a little. The main gear doors
and attachments concerned me most. It just seems like
when the gear is extended, a lot of surface area is
being exposed to 120KT winds - especially if you
include a yaw factor. The main gear doors are
supported on one end by a thin tab that's glassed onto
the gear with two bid on each side. Soooo, not only
did I add layers of glass to the main gear doors
themselves, but I also beefed up the tab. In the end,
my tab ended up being about 3/16" thick and was
glassed on with 4 bid having lots of overlap on the
gear leg. 

 What a moron I was! The day before the first flight a
did some high speed taxiing and all went well. While
inspecting the plane that night, I noticed that one of
the tabs was cracked where it met the gear leg and the
other tab had literally failed in the same place. I'm
talking failed to the point where it was providing
little or no structural support. 

 After picking myself up off the floor the problem
became obvious: the main gear legs are fiberglass and
have an elbow shaped curve in them. This combination
provides for shock absorption through flex. Since the
gear doors are bolted directly to the gear legs with
this curve in the middle they better be able to flex a
lot! Mine were as stiff as boards. In fact, when I
unbolted the gear doors from the tabs and raised the
plane on jacks, just the flex from the weight of the
plane caused about a 1" mismatch at the tabs. The
force required to match the holes back up was
ridiculous. On landing the legs obviously flex even
further than this. When I showed all this to my test
pilot we agreed to go ahead with the first flight -
just without the main gear doors of course. I'm sure
he wanted to ask me if I'd made any other "mods"....

 When I called Brendan at the factory he said he
didn't know of  any horror stories about gear doors
going through props, but he WAS horrified to hear my
tabs had failed. He said the gear doors are supposed
to be (read as "must be") relatively flexible. BTW, a
lot of the flex comes from where the gear door bends
90*. And yes, I had beefed mine up there too - see
attached pic. I ended up having to undue all that
beefing up to get the proper flex back in the gear
door and tab. When I was at Osh this year I checked a
main gear door on another Velocity and it easily
flexed by inches between the wheel and the tab. Mine
still aren't that flexible but appear to work. I've
got 100hrs and probably as many landings. Of course
now I check my gear doors and tabs for any sign of
cracking on every preflight.

Embarrassingly,

Pat Shea XLRG 

--- Richard Riley <richard at riley.net> wrote:

> On Berkut we had the beefiest gear doors you've ever
> seen - 10 plies 
> of carbon, full length extruded hinge (ms2001-6) and
> no gear extend 
> speed.  I've opened the gear at 200 kts.  We had an
> electric speed 
> brake, the brake itself was about 10 plies of glass
> in various 
> orientations.  With the brake out, the gear down,
> cross controlled at 
> idle with a fixed pitch prop, I've had an 6000 FPM
> rate of decent at 
> about 180 kts.
> 
> Just a datapoint.




		
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