Budd Davisson @ Airbum.com On Landing Taildraggers
Budd Davisson, the popular and prolific aviation writer and part time airplane evaluator, posted the following a few months ago on the Bearhawk Yahoo website. It is the best short essay on landing taildraggers I've ever read. I asked for and received permission to repost it here.
You can learn a lot at Airbum.com.
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February 9, 2005
Alright, I'm a little more rested and ready to take this thing on:
First, you can't make a black and white statement that wheel landings are bad and three-points are the only way to land. It changes with the conditions and the airplane.
For anyone in the group who I haven't assaulted on this particular subject: I've been teaching in tailwheels as a CFI for 39 years, 4,000 hours plus dual given in the Pitts in which I specialize in teaching people to land with narrow, short runways being my specialty. Another couple thousand dual given in other tailwheels from Cubs to T-6's.
My rule for the use of a wheel landing is strictly driven by the gust spread. As the gust spread becomes a larger part of the airplane's stall speed, the likelihood of being picked up right at the point of touchdown increases. However, even that isn't black and white because the direction and character of the gusts come into play.
If you study wind closely, which I do on a daily basis, you'll notice that there are some crosswinds where the gusts always come from a different direction than the wind. Normally, if you have a 30 degree right crosswind, for instance, with a 10 knot gust spread, that gusts will be from 40-45 degrees, so for that instant, you have a bigger crosswind then you have the airplane set up to handle (wing down at a given angle, etc), which calls for instant correction. This is no big deal unless two factors are involved: if the gust spread is 20-25% of the aircraft's stall speed or more and it gets to be a VERY big deal if the wind is snapping from slightly in front of the wing to behind it. Then you have a serious shear condition that loves to plant airplanes like hockey pucks.
If the wind has no gusts, then it really doesn't make any difference how strong it is because the airplane will just be moving slower on touchdown, so a three point is nearly normal and is all that's needed. However, the lighter the airplane, the lower it's crosswind component limit will be although even that isn't carved in stone. A Maule, for
instance, is the same weight as a BH but it will barely handle 10 knots across the runway (the POH says 12, I think) because of the huge fin and the tiny rudder. 108-3 Stimson's with the big fin have the same problem. The BH is at least twice that.
Some airplanes, a Taylorcraft BC-12D, for instance, really work you in fairly small winds because it is so incredibly light and doesn't want to stop flying. Still, if you stay right on it, you can handle more wind than you think, but gust spreads are its real enemy.
On heavier airplanes (T-6's, Mustangs, etc) I always three-point them even though you don't see it done often. The only reason people don't is because they are worried about landing crooked and loosing them, which isn't really a factor.
On airplanes with higher wing loading, e.g. the Pitts, I ALWAYS three-point it. The Pitts has such good slow speed control and is so heavy, I don't consider it to have a crosswind limitation. My record is a documented 38 knots, gusting to 50 that was snapping from 60 to 90 degrees to the runway and it wasn't even a hard thing to do and the airplane was a LONG way from it's limits.
THE FOLLOWING IS CRITICAL WHEN THREE-POINTING IN GUSTY WINDS:
First, be ready with the power to break a fall should a gust die just as you're ready to touch down. Then be ready to roll the wing into the wind should a gust pick you up after touch down.
The kiss of death in a gusty three point landing is to let the airplane begin drifting AFTER it has been picked up by a gust, which is highly likely if flying a lightly wing loaded airplane. If it is picked up OR you bounced and you let the wind drift you, it will take much more down wing to cancel out both the wind induced drift AND the momentum of the airplane moving sideways.
At the same time, there's going to be an increased tendency for the airplane to weather vane at the moment it is picked up. So, there you are five feet off the ground moving sideways, the nose coming into the wind and running out of speed. If you let the airplane touchdown in that situation, you're going to be a very busy bear. Very busy. The airplane's tendency to snap into the wind because of the drift and crooked stance will be dramatic.
Here's an absolute, not to be violated rule: if you bounce or get picked up in a crosswind, the instant it starts up, you lean into the wind AND COME BACK DOWN IN YOUR ORIGINAL TIRE TRACKS. That means you'll be aligned with the line of travel (nose straight, wing down) with no drift and there will be no consequences.
On light airplanes, Cubs, Champs, etc, if the gust spread gets up to around 10 knots (25% of stall) and the wind is 20 or more degrees off the nose, for most folks, wheel landing is definitely called for to cancel out the possibility of the gusts slamming you into the ground at touchdown. However, wheelies in that situation can call for more technique then a three point would.
First, it should be stated that different airplanes wheel land better than others and the idea that you can wheel it on without "loading" it after touchdown borders on lunacy, especially in gusts. The whole reason for a wheelie is to touchdown at a high enough speed that the wind is less of a factor, which also calls for a lower angle of attack. If you
zero out the rate of descent exactly, yes, you can fly it on to the ground and not paste it on but that is really a trick and one I'm never confident I can pull off. So, because you've almost always got just a little rate of descent at touch down you always have the possibility of a little rebound and it's the rebound that can eat your lunch on a wheel landing (and that's ignoring a number of other lunch eating possibilities).
The other thing that'll eat you up on wheel landing is to "anticipate" the touch down: you're hanging there and you know it's going to touch at any moment and you yield to temptation and try to push it on from a few inches up. Boing! And you bounce. In some airplanes you can force it on in that position, most you can't. The right thing to do is to power up slightly and fly it back on to the ground.
The trick is to hold it off and fly formation with the ground gradually closing on it until you land on the back half of the main tires and gently bring the tail up level or slightly high to nail it down. When instructing in Champs, we used to run the trim all the way forward then, just as the airplane touched down, put both of our hands out in front of
the student so we could show them that it was the trim that had rolled the tail up and held it up until it was ready to come down gently on it's own. I don't recommend this technique but it was a good demonstration.
One way to fight rebound is right at that magic moment when you know it's just about ready to touch, drop one wing slightly, so you touch one wheel before the other. This cuts the rebound in half. In a crosswind, you'll be landing on one wheel anyway so it's not that much of a problem.
Wheel landings are useful but they have the potential for spectacular problems if a pilot persists in trying to force it back down after bouncing/skipping. The mains touch, the CG continues going down, the airplane pitches up, the pilot forces it down, the CG comes down harder so this leap is worse than the last but the speed is diminishing so he
has less control, yada, yada, yada.
Lynn's comment about the Army not letting them wheel-land Bird Dogs was based on the fact that the rebound and crow hopping tendencies of the L-19's whippy gear in a wheel landing is such that you can get some really wild porpoises going. Been there, done that. I don't know how you wheel land most spring gear airplanes without without loading them in a very precise manner at touch down.
Do I think airplanes should be wheel landed as a matter of course? Absolutely not! The additional speed is your enemy and waiting to bite you in the butt. Do I think airplanes should ALWAYS be three-pointed? Absolutely not, although it depends on the airplane. There are NO conditions, for instance, in which you'll see me wheeling a Pitts on. But, you'll never see me trying to three point a T-craft in a 15 knot wind with ten knot gusts 30 degrees off the nose. Hopefully, you'll never see me trying to fly a T-craft at all in that wind.
Incidentally, to get a tailwheel endorsement, the FARs say the instructor is supposed to teach wheel landing, so you should know how to do them anyway.
**CENSORED****CENSORED****CENSORED****CENSORED**! I didn't mean to ramble on so long. Sorry. But this is obviously one of my soap box subjects.
bd
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