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I just saw a photo of the Pipistrel Apis motor-glider, and it got me wondering: How can it safely land with only 2 wheels total? To me it seems that falling to the side would be inevitable, and with wing fuel tanks, that could be terrible. In all the pictures, it's resting on (one of the) wingtips.

enter image description here

Are the wings/wingtips reinforced for landing & supporting the airplane on the ground?

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    $\begingroup$ This motor glider only carries 5.2 gallons of fuel, about 17 pounds on each side, tucked right up against the fuselage. That's not much weight on the wings. $\endgroup$
    – rbp
    Commented Dec 19, 2014 at 6:53
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    $\begingroup$ Just as a sidenote, the U-2 spy plane also only has two center mounted wheels and seems to tip on to one wing after coming to a stop. See landing video. $\endgroup$
    – Tarmo R
    Commented Dec 19, 2014 at 10:58
  • $\begingroup$ Added the name of the plane to the title - this would help searchss (Google/Bing) $\endgroup$
    – CGCampbell
    Commented Dec 24, 2014 at 14:15

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Many modern gliders only have one wheel -- two is a great luxury!

In a glider the wing and flight controls remain effective until the aircraft is almost completely stopped - with a little training and practice it's possible to balance on the one (or two) wheels right up to the point where you're nearly stopped, at which point the glider will gently tip onto one of its wings as it comes to a halt.

As you've surmised the wingtip usually has some reinforcement or other provision (such as a skid plate or a small wheel) to prevent damage when it contacts the ground. The photo below is of one of these wingtip wheels.
304S sailplane wing-wheel

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  • $\begingroup$ Oh I'm really surprised by that. I'l rethink the idea of learning to fly a glider now, haha! $\endgroup$
    – Délisson Junio
    Commented Dec 19, 2014 at 4:43
  • $\begingroup$ @wingleader It's also worth noting that the Apis fuel tank used to be located in the fuselage -- they moved it out into the wing for safety reasons (so you're not sitting on top of 2 gallons of fuel if you crash). $\endgroup$
    – voretaq7
    Commented Dec 19, 2014 at 4:46
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    $\begingroup$ Landing and taking off in a crosswind also requires a fair amount of skill, versus an airplane. At many glider ports you have a ground crew that holds the wing level until the tow plane starts its ground roll. But if you don't have a ground crew, the wing drags as you put in full opposite aileron to get the wing off the ground. Once it comes off the ground, you have to fly it wings level or with the upwind wing low enough to keep the plane rolling straight. $\endgroup$
    – rbp
    Commented Dec 19, 2014 at 6:49
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    $\begingroup$ Don't forget the wind: Even when the glider has come to a stop, some control power remains depending on headwind. BTW, the real luxury is the tip wheel in the picture. Normally the wingtips have small rubber blocks with a steel plate screwed to its bottom. $\endgroup$
    – Peter Kämpf
    Commented Dec 19, 2014 at 7:22
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    $\begingroup$ Looks like someone stole that wheel off his kid's inline skate! Now poor Timmy will be wobbling down the sidewalk instead of doing tricks down the stairs. $\endgroup$
    – FreeMan
    Commented Dec 19, 2014 at 13:31
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Almost every glider has just one wheel close to the centre of mass. Some have a small tail wheel, school gliders may have a front wheel that avoids to scratch the nose when you are learning. Whatever the number of wheels is, you spend most if not all the time balancing on the main one.

Every skilled glider pilot is against anything that could create even the minimum amount of drag and is not strictly necessary!

The key point here is the amount of fuel inside the wings, which is really tiny (a small motorbike tank per wing) and allows for safe landings. If it was more it could create problems mostly because of its weight and the related stress on the wings when touching down. Indeed most of the competition gliders allow to fill their wings with water in order to increase the performances at high speeds, however it is mandatory to evacuate it before touching down, and of course you wouldn't want to do the same with unspent fuel.

enter image description here

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  • $\begingroup$ How would the tanks be completely emptied of water, or do they resign to never filling them with fuel afterwards? (or does a small amount of water not destroy the engine, similar to what would happen in a car)? $\endgroup$
    – user2813274
    Commented Dec 19, 2014 at 16:36
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    $\begingroup$ @user2813274 Competition gliders I'm familiar with do not have engines (it's wasted weight). $\endgroup$
    – voretaq7
    Commented Dec 19, 2014 at 17:00
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    $\begingroup$ @user2813274 Water goes in dedicated tanks that can fill all the wings and you release it by gravity before touching down. Fuel tanks (when present) are tiny and close or inside the fuselage. $\endgroup$
    – DarioP
    Commented Dec 19, 2014 at 17:02

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