Tri-Gear Landing Gear on a Fly Baby

Calm down, purists.  I'm not *seriously* suggesting that we need a tricycle landing gear for Fly Babies.

Then again, there are some arguments for it.  We had a discussion on the topic on the Fly Baby Mailing List, and here's what Richard Dodson had to say:

Well, from what reading I have been able to do on the origins of the Fly was supposed to be the Experimental for the average, not wealthy homebuilder.  Problem is that most average homebuilders are not taildragger pilots these days.  The sport pilot proposal is great, but we are still talking at least $$ (vice $$$$ a la Vans, etc.) to get an average LSA flying.  I spent over $3000 (hotel, travel, plane, instructor) getting 20 hours of taildragging time (provided, of course, that one can even find a taildragger instructor in the area with an insured aircraft! - not easy in the South).  This flys in the face of the Fly Baby concept.

Don't get me wrong, the Fly Baby is a beautiful airplane as is.  Got better curves than my wife. But, can we translate it into something that fits most pilot's skills and background today and maintain the ease of construction, low cost, and fun flying purpose - not to mention most of the good looks?

Richard really has a powerful argument there.  We can talk about using updated materials all we want, but to most pilots today, the prospect of flying a taildragger is daunting.  And, as Richard mentions, the whole process of getting checked out is expensive.

There's one thing that makes it a bit more complicated than most airplanes:  The landing gear structure of the Fly Baby is part of the wing bracing structure (see the Bracing page).  It's not just moving the gear...we have to maintain a good structure for attaching the flying wires to. might we go about changing to a trigear configuration?  The nosegear itself can be relatively simple...let's assume we go to an RV or Grumman Trainer sort of nosegear system.  We'll not make it steerable, we'll just let the thing pivot and use brakes to steer.  We are a number of trigear homebuilts for which we can copy the attachment system...probably end up with some tubes added to the engine mount.

Now, what about the main gear.  The easiest thing to do is just to swap it around....use the existing landing gear mounts, and just "flop" the gear legs around:

Keep in mind that just switching the gear around would't'd need the ends of the legs cut to match the fuselage at the new location.

One problem with this picture is that I'm not sure if the main wheels are far enough back.  The axle has to be further aft than the rearmost CG limit...the aftmost limit is about 31% MAC, so the diagram might be all right.  But if it's not far enough back, the plane will drop on its tail as soon as you'd stand on the wingwalk while boarding (like the B-24 would).  But position the gear too far back, and the plane "flumps" down when the mains touch on landing (so much leverage) and/or it's hard to rotate on takeoff.

So this is just a "notional" drawing.  I cringed when I drew it, but it tended to grow on me.  Once nice thing is that it puts the attach point for the flying wires almost directly between the spars.  This is good; the flying wires pairs take up a more equal load, now.

However, I can see one big drawback:  The gear "V" isn't oriented right to resist landing loads.  Hard landings are going to tend to want to push the wheels in the direction of the big green arrow.  Note that there isn't a gear strut to oppose that, like there is in a stock airplane.   A hard landing will try to rotate the gear legs around the top aft fitting, and the front strut isn't really oriented to resist that.

But then... a Piper Tripacer is almost the same.

One suggestion was to keep the flying-wire attach point about the same and make the gear a trailing-arm setup for shock absorption.

Structurally, I like this better...the aft gear leg is still set up to oppose the landing loads.  The flying wires attach in approximately the same place, so the loads are where Pete designed them.

Doing the trailing-arm gear is a problem, though.  The conventional method of shock absorption requires a VERTICAL gear leg...which we don't have.  We'd have to use a torque-tube type shock-absorption method, rahter than something that depended on a vertical spring or shock absorber.

To wrap up, I want to make one thing clear:  There are no drawings of this, and as far as I know, no one trying to do this.  If you want to build a tri-gear Fly Baby, you are on your own....

I'll have to admit that my initial reaction to the concept of a tri-gear Fly Baby was YUCKKK!!!  But after I make the drawings and let them sit on the screen for a while, it kinda grew on me.

Comments? Contact Ron Wanttaja.

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