Interesting Article

[Trematode]

To put it another way:

What happens when you land with too much crosswind correction in a crosswind?

The same thing that happens if you land with crosswind inputs and no crosswind!

[akoch]

This is assuming the slipping x-wind correction method, not crabbing.

[photofly]

I am just trying to picture how you are setting it down on one wheel, with no wind, while maintaining your centerline.

I think the questions you ask are apposite.

If you want to enter the manoeuvre smoothly I imagine you could begin from a forward slip, by touching down one wheel in the slip (scuffing it) and then smoothly using the rudder to align the fuselage with the direction of travel, while maintaining the bank with the ailerons.

Or you could touch down on both wheels and lift one by increasing the bank, while keeping the fuselage aligned with the runway with the rudder.

Both of those methods would allow you to build up the side-load from zero - the first begins with zero side-load because of the slip, and the second because it starts with zero bank.

If you fly low and level, and just drop one wing to touch the wheel then I expect the aircraft is going to start to slip to the side for the short period until the wheel touches. So that would give you some extra dynamic sideload as the tire bit and halted your sideways motion. In other words you would feel the aircraft jerk and it wouldn't be smooth entry.

The Colonel will have to say if that agrees with his experience?

[Trematode]

Both of those methods would allow you to build up the side-load from zero - the first begins with zero side-load because of the slip, and the second because it starts with zero bank.

I don't see how the first starts with zero side-load -- if you're slipping and there is no crosswind to eliminate your drift, you will touch down with sideload, no?

To clarify, I don't see any problem with the exercise is there's enough crosswind for it: Have at it, do your one-wheeled touch and goes all day long. If you do it right, your wheels would be aligned with the runway the entire time. It can be fun and a good challenge to keep your wheel up for the entire roll in the same way you can keep the nose wheel off the runway when practicing your soft field techniques -- an exercise in power and positive control.

[photofly]

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[photofly]

I don't see how the first starts with zero side-load -- if you're slipping and there is no crosswind to eliminate your drift, you will touch down with sideload, no?

True. If you fly in a forward slip then you can touch a wheel down gently. At that point the wheel axis is twisted both forwards and sideways, so a downward load on it will generate some kind of side-load, yes. Difficult to analyze unless you're into 3d trigonometry (everything so far has been in two dimensions.) And the twisted axis will cause the tire to scuff and skid. But you can still touch down slowly and smoothly onto it, and from there, transition smoothly to bring the nose parallel to the direction of travel.

But just to be clear - that's by starting in a forward slip. You don't have a crosswind to eliminate drift, but in any case in a forward slip you don't have any sideways drift that needs to be eliminated.

[photofly]

I'm not sure if I need to say this or not, but to be clear, I'm not claiming great leaps forward in flying can be made from this very basic analysis of this situation. I think it's interesting and straightforward to show that there is a significant side-load on the wheel if you line the nose up down the runway; but the rest of the discussion I don't think teaches much about real flying, and there are dangers in trying to over-interpret a fairly simple physical model. I enjoy the discussion but at some level of detail it's just too theoretical to be of any practical use.

[Colonel Sanders]

One of the Prime Directives of tailwheel flying is
that you never touch down with a crab - that is,
with the longitudinal axis of the aircraft misaligned
with the direction of travel.

If you do so, you instantly have created a problem
which you must solve. If the tires have any grip at
all - dry pavement is the least forgiving - it will grab
and shoot the aircraft towards the side of the runway.

This problem must be instantly solved with the rudder
pedals.

Rather than creating a problem which must be skillfully
solved, I teach pilots to reject any approach, flare,
touchdown and rollout which is not darn near perfect.

The above is true regardless of whether or not you
are touching down three point, or wheel landing.


Corollary of the above Prime Directive: always have
lots of fuel, so you never have to push a bad approach
into a bad landing. You'd be amazed how many people
do. I have no idea why. Anything goes wrong - or if
you even ASK yourself if you should go around - the
throttle goes all the way in. The tail feathers instantly
start to work. Get some airspeed and a foot or two
between the tires and the runway, and accelerate in
ground effect to at least Vx, then climb out.


Anyways, back to the topic, which is touching down in
a forward slip on one main: I would not recommend it.

Touch down in a side slip, with the aircraft aligned with
the direction of travel, unless your coefficient of friction
is very low (grass, gravel, snow, ice).

5 degrees of crab at touchdown is easy to see, and is
too much. 10 degrees, and life is going to get really busy.

If you can get the crab down to less than one degree
(there is some luck involved), the tailwheel aircraft will
roll down the runway with no intervention required at
the rudder pedals. This is like a piston balanced at top
dead center when you are doing a leakdown test - you
can take your hands off the prop, and it will not move
even though you are pumping 80 psi of air into the cylinder.

Think of being on a bicycle and your entire body weight
on one foot, which is at the very vertical top of the stroke.
There is no resulting torque - just a downforce.

[photofly]

Don't you get some tire-grab as the tire catches against the side-slip?

[Colonel Sanders]

If you have a crab angle, doesn't that make it a forward slip?

You can land wings level with a crab. Happens a lot

In my posting above, I was talking about both banked and
wings-level touchdown.

[Colonel Sanders]

Don't you get some tire-grab as the tire catches against the side-slip?

Nope because either

1) there is a crosswind, and the aircraft doesn't move
sideways in the side-slip, or

2) there is no crosswind, and you side-slip right before
touchdown, and the aircraft doesn't have time to react
to the inclined lift vector.

I wish Eric was home from University. We need to film
this from several angles and paste it all together with
PIP into a youtube video.

[photofly]

I think I misunderstood you. You're recommending to fly into this with no crab angle at all, right? But presumably you want to transition to the side-slip just before you touch down the wheel. If you start to sideslip too early you'll pick up a lot of sideways drift across the runway (like kicking out the crab for a wings-level crosswind touchdown.)

EDIT: OK, got it.

[Colonel Sanders]

If you start to sideslip too early you'll pick up a lot of sideways drift across the runway

Theoretically yes, but practically speaking what
you do is drop the wing just a little (say 5 degrees)
right before touchdown, then after touchdown,
increase the bank to 10 degrees or so with full
aileron and power.

I want the wingtip about 18 inches off the pavement.

I wish Eric was home from University. We need to film
this from several angles and paste it all together with
PIP into a youtube video

We could film helmet cam, camera pointed at the
tire, view from directly behind, and front quarter.

[Shiny Side Up]

push a bad approach
into a bad landing. You'd be amazed how many people
do. I have no idea why. Anything goes wrong - or if
you even ASK yourself if you should go around - the
throttle goes all the way in.

The main problem is that at the point where thy realise stuff has gone wrong its already become a crash. Frequently, adding power at this point just adds energy to the crash making the results more spectacular. The more power the airplane has the worse this tends to be, since if they're behind the ball to begin with, chances are they're not going to be ready for the resulting yaw from applying the power. One of the things I harp on with students - even with nose dragger landings - is that you have to decide early rather than later, preferably before the rubber is grabbing the ashpalt.

[Colonel Sanders]

The main problem is that at the point where they realise stuff has gone wrong its already become a crash

That sounds good, but I'm not sure it's always true.

VFR into IMC is a good example of people making
the wrong decision, to continue what they are doing.

I am not a psychologist, but there is something about
pilots - perhaps they are selected for it - who are very
internally driven to achieve an objective. If they weren't
like that, they wouldn't have overcome all the hurdles to
be pilots.

It takes an awful lot of maturity to say "No, I'm not doing
that" - especially when you are already doing it!

There's something about the momentum of events that
has a way of carrying people to the scene of an accident.

Pilots are ashamed to overshoot. Beats the hell out of me
as to why. Everyone wants more time in their logbook (except
maybe me and .). Well, going around will probably put
another 0.1 or 0.2 in your logbook, so why not do it?

I'm not ashamed to overshoot because I couldn't give
a f__k what anyone says. Most people are morons
anyways - by definition, half of the population has an
IQ of less than 100 - so why would you care what they
think?

[Shiny Side Up]

The main problem is that at the point where they realise stuff has gone wrong its already become a crash

That sounds good, but I'm not sure it's always true.

Of course its not always the case, though I would say it does account for most of the take off/landing type accidents to which I was referring. I'm sure you seen that guy who is so far behind his airplane its a few provinces ahead of him. Hell, last one I saw, the power came up to go around well after he was mowing grass.

VFR into IMC is a good example of people making
the wrong decision, to continue what they are doing.

I am not a psychologist, but there is something about
pilots - perhaps they are selected for it - who are very
internally driven to achieve an objective. If they weren't
like that, they wouldn't have overcome all the hurdles to
be pilots.

It takes an awful lot of maturity to say "No, I'm not doing
that" - especially when you are already doing it!

There's something about the momentum of events that
has a way of carrying people to the scene of an accident.

Hard to say. Sometimes it feels like some are just ticking time bombs, accidents waiting to happen. Sure we all have to have a level of that can do attitude, but there's "can do" and then there's that "must do" almost obsessive trait you see in others. Others just seem to have a real lack of sense of self preservation. I suppose you're right that flying airplanes seems to attract these people as well.

[Colonel Sanders]

http://www.flyingmag.com/technique/prof ... hesitation

By the same token a certain amount of optimistic confidence is natural in a pilot, an overly optimistic attitude can lead to wishful thinking. This attitude leads to many of the common human factor accidents, and it is more likely that a pilot will fall prey to wishful thinking on final approach, so the closer a pilot is to his destination, the less likely he is to turn around, divert or abandon the approach.

For example, a pilot who realizes he is low on gas many miles from the destination is going to find some place to stop and fill the tanks. As a pilot who is low on gas approaches his destination, wishful thinking can start to kick in. Because of a desire to avoid stopping for gas that close to the destination, the pilot might decide he has enough gas to make it without any specific data to support that decision.

[Beefitarian]

"Realize they're low on fuel"?

People are flying airplanes without bothering to calculate these things and keep track of how long they've been airborne?

[Colonel Sanders]

Yeah, I know. That's the "swiss cheese" accident
model, and is probably mistake #3. If that pilot
continues to make mistakes, he will have an accident.

The important thing for pilots to realize is that there
is a powerful tractor beam pulling you to your destination
airport, and possibly your doom.

It can be an awfully tough decision to

1) not take off in the first place (get-home-itis)
2) stop midway for fuel (eg headwinds)
3) divert to a different airport
4) overshoot at the destination airport
4) return to your departure airport

But sometimes if you don't make the above tough
decisions, there are horrible consequences.

Some years ago, I got delayed clearing customs
at CYOW, and by the time we finally took off for
my little airport to the west, weather was moving
in. It was nasty, and had a solid edge. I got within
10 miles of home, and I had to turn the formation
around and go back to Ottawa and put the airplanes
in a very expensive hangar overnight, and arrange
for transportation for us home that night, and then
back to Ottawa the next day to get the airplanes
when it was sunny.

Lots of people really hate me, and one of the reasons
why is that I'm not afraid to make tough, unpopular
decisions like that, and then stick by my decisions.

Life is not a popularity contest in high school, as
people will teach you here. If you think like that,
I guarantee that you will have accidents in aviation,
probably eventually a fatal one.

Being a pilot is a lot more than just wiggling the
aircraft controls. That is necessary, but not sufficient.

You must also learn to make decisions. Correct
ones. Tough ones. Unpopular ones. That takes a
thick skin sometimes, which I have observed that
many people these days lack. They want to be
popular, and please everyone around them. That's
a great way to bust your @ss.

I know I will be viciously attacked by the touchy-feely
crowd for saying this, but there is no crying in the cockpit.

[Shiny Side Up]

The important thing for pilots to realize is that there
is a powerful tractor beam pulling you to your destination
airport, and possibly your doom.

Lots of times though I find that its just plain idiocy that causes problems. While the tractor beam may be strong, I have a tough time believing that it is the sole reason in many cases where I've seen pilots do ludicrous things in the process of going flying. Like the guy a week or so ago who tried to go flying with a flat tire. I mentioned to im he had a flat tire, and fighting against my inherently evil nature, I volunteered the services of a jack and an aircompressor to potentially remedy the problem. No, no, he would decide, his airplane, he's the pilot. So he surveys it, then with a shrug attempts to just giv'er. He makes about 3 feet. Gets out, looks at the tire. Tries again. Then repeats this process several times. I think he got about 12 feet before the tire was peeled off of the rim. Then just abandons the airplane in place and speeds off. What's the definition of insanity again? The point is that I have trouble believing that its just the lure of the destination that makes people do unreasonable things but rather that some are prone to making bad decisions in the first place.

It can be an awfully tough decision to

That assumes of course that there was some sort of consious decision made. In the case of the fellow above, It would seem that in his mind there was no question of whether to go flying or not, hell or high water he was going to go, only when the laws of physics intervened was he going to be stopped. Sadly this individual isn't unique, but the point is there are people out there who span the full sanity spectrum, some of which hold pilot's licenses. After all, we have a whole list of CARs which seem largely mandate what common sense would dictate anyways, but they are there because in someone's thought process said crazy activity seemed reasonable to do.

[Cat Driver]

Like the guy a week or so ago who tried to go flying with a flat tire. I mentioned to im he had a flat tire, and fighting against my inherently evil nature, I volunteered the services of a jack and an aircompressor to potentially remedy the problem. No, no, he would decide, his airplane, he's the pilot. So he surveys it, then with a shrug attempts to just giv'er. He makes about 3 feet. Gets out, looks at the tire. Tries again. Then repeats this process several times. I think he got about 12 feet before the tire was peeled off of the rim. Then just abandons the airplane in place and speeds off.

Such an individual should be charged with reckless and dangerous operation of an airplane and his license should be revoked.....permanently.

[akoch]

I had a flat tire. Which I discovered only after attempting touch and go. Went practicing from CYPK to CAP3, and on touch and go noticed that the airplane tended to turn sideways more than usual. I figured that was a flat tire, but I had to land either there or back at the home airport. Went CYPK, landed on what I thought was the good side as much as I could. But it did not really feel much different for landing and roll out. Taxiing though was a bit wired pulling it one side. Turned out a defect in the inner tube that ruptured it. Thank you Goodyear.
So I think I ended up with a couple of take offs and two landings with the flat. But I did not get an impression that it was such a big deal on a small airplane line mine. Noticed it only because I was actually paying attention. Might be way different on a heavy and fast one.

[Colonel Sanders]

Turned out a defect in the inner tube

There's an awful lot of us that have been bitten by
that in the last few years.

[Cat Driver]

We had both our tubes go flat in the new Husky in less than fifty hours from new, both tubes were manufactured with weak bonds.

[Cat Driver]

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