REFLECTOR: 165 kt Gear Extension Speed

Wed Dec 7 17:03:30 CST 2005

Hi Rene,

I briefly considered this idea as well. The problem is
that you want the gear doors to be nice and flush when
the gear is retracted. That's would to be challenging
to accomplish with hinges - it's hard enough to get it
right with ridged tabs. Also, you wouldn't want the
hinges to allow air loads to affect the fit of the
doors while flying. Further, it seems like hinges
could invite flutter.

Just my thoughts, Pat

--- Rene Dugas <dugasd at bellsouth.net> wrote:

> Wouldn't two hinges place at the attach point to the
> upper main gear leg
> and at the upper attach point on the main gear leg
> allow flex and
> minimal undesired motion and excellent strength?
> Rene'
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Chuck Jensen
> Sent: Tuesday, December 06, 2005 10:27 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: RE: REFLECTOR: 165 kt Gear Extension Speed
> 
> 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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