RC-Type retractable landing gear

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Radicaldude1234

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May 30, 2009
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Front Range, Colorado
I was just wondering why the RC robart style retracts aren't used more in light aircraft. They have all the uplock/downlock requirements dictated in FAR-23 and are nice because you can use a single actuator to activate the entire mechanism. From what I see, theres no reason why they can't be scaled up as a hydraulic retraction unit.
 

Radicaldude1234

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May 30, 2009
Messages
387
Location
Front Range, Colorado
kinda like the ones in this link:

Robart Mfg. R-C Model Airplane Parts

From what I understand, most landing gear systems have a separately actuated uplock and downlock which, although good for manual releasing, also I think increases complexity somewhat. If you're going to blow the actuator down with compressed air in an emergency anyways, why add more components that might fail and stop it in that case?
 

JimCovington

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Mar 30, 2009
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Burlington, VT
I'm going to guess weight. By them time you scale it up to the strength required for human-carrying aircraft, it's much heavier than more complex alternatives. Those two side plates would have to be pretty massive chunks of steel to carry the loads.
 

Bart

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Apr 13, 2007
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Looked at the retractable gear on a KR-1?

Consists of a thin bar of spring steel or aluminum bent at each end with an axle/wheel bolted on, and a hinge with handle in the middle. Hinge bolts to spar or other structural member.

This thing is as simple and probably light as it gets.

Think: Fixed bow landing gear, but not fixed since it hinges to the fuselage frame. Rotates ~110 degrees up into wing cavities.

Why is this simple and light idea not more popular?
 

JimCovington

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Mar 30, 2009
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Location
Burlington, VT
It's a good question, but I'm going to stick with my original answer. The KR gear is barely 12" off the ground and supports a gross of only 750lbs - most planes require much more clearance, and the suspension & strength of the gear just aren't there at larger sizes.

A quote from this thread on KR gear:
"...gear was stiff enough to encourage PIOs, had almost no effective damping, and had a nasty tendency to wear down the down-locks..."

These are solvable problems - but you might find that by the time you solve them, you have something that looks like Piper or Mooney gear.

https://www.homebuiltairplanes.com/forums/design-structures-cutting-edge-technology/5153-unsprung-landing-gear.html
 
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