REFLECTOR: 165 kt Gear Extension Speed

[Scott Derrick]

Pat,

Many thanks for the story.

Just a few hours ago, I was looking at the gear and trying to figure out 
a "easy", haha, way to seal the cabin where the gear legs come through, 
sans doors. I glanced at the main doors and thought, "you know, I could 
just really beef up these babies, and a couple more attach points and 
have main gear doors and 165 knt extension speed."

So much for thinking...

Scott

Pat Shea wrote:

>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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>
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