Direct Crosswind

[white_knuckle_flyer]

The yaw is opposite to the way you are rolling
your steering wheel.

So if a couple of guys, one on each wing, were pushing me over to the gas pumps and I turned the column to the right and the downward deflecting aileron hit the left-wing guy on the head and he momentarily stopped pushing in order to curse me out, then I would start turning left with right aileron input.

Is this adverse yaw ?

Many people do not find it intuitive that at
slow speeds, you roll the control column in
one direction, and the nose goes the other
direction..

I think you could go further and say that it is intuitive for no one. Not unless you believe in reincarnation and someone was a pilot in a former life.

[CpnCrunch]

I just wish that the aviation community in general would come clean and pick a side. There are people out there who will tell you that once a plane is in the air, the only thing going on is the relative wind over your wings/rudder. "Have you ever seen a weathervane that is hovering in the air ? And if you did, how well would it work?, they would chide.

But there are those who say weathervaning within the air mass is real, albeit the effects are most keenly felt at slow speeds where the effects of the relative wind upon the rudder are diminished.

No wonder it took me to long to get my PPL. It was just this kind of stuff that kept my head spinning.

I think you just need to look at what happens during a turn. Completely ignore adverse yaw for now. When you roll into a left bank, the lift vector has a sideways component, so the plane starts moving towards the left. So why does the plane start turning? The reason is because of the tail fin. You now have a net sideways wind acting on the plane (instead of moving directly into the wind), so the tail acts like a big weathervane, causing the plane to turn.

Exactly the same thing happens when sideslipping. In that case you don't want to turn, so you use opposide rudder to prevent the weathervaning.

What I don't understand is why BPF/CS/Photofly are saying that the primary reason to use the ailerons while taxiing is to prevent weathervaning via the effects of adverse yaw. That just doesn't make sense for a variety of reasons. Care to explain?

[pelmet]

In terms of headwind or tailwind on base, why don't you just take the crosswind half the time from each direction. Then the student gets to practice both a headwind and a tailwind on base, gets to see the difference and can plan accordingly so that in the future when they don't have a choice they will be well versed.

That's sounds like a time tested idea by now (with regards to the opening post on this thread).

Come to think of it, the left circuits on runway 24 at CYSN would seldom be landing with right crosswind since we would simply be cleared to land runway 29 (used to be 28).

It's as simple as that. Good practice. I'm not an instructor so I don't want to be pretending how to train students like some people here have been doing for many years.

As can be seen on this thread, some pilots also fly to the maximum capability of the aircraft with full rudder on final and that is fine for the superior pilot. But for an average guy like me with several small types being flown but only occasional flying in each specific type, I tend not to fly at maximum limits compared to the display pilots.

Have just decided to be conservative that's all. Will enjoy watching the videos of the top guys. So it is interesting to hear about the idea of taking a crosswind from a certain side if landing in max crosswind due to the extra rudder required when some power is added, and it is good information to know. But in general, I would suggest that the student see strong crosswind from behind on base as good practice. After all, go-arounds are good practice as well.

[Shiny Side Up]

Stick over ALL THE WAY into a crosswind landing.

http://www.youtube.com/watch?v=US9je8STwjo


This is not optional.

So I can't help but notice that he's taking the crosswind from the left.

[photofly]

What I don't understand is why BPF/CS/Photofly are saying that the primary reason to use the ailerons while taxiing is to prevent weathervaning via the effects of adverse yaw. That just doesn't make sense for a variety of reasons. Care to explain?

I'm not saying that, and I'm also being told I'm a pedant for making the distinction. Also I'm not saying it's the primary reason, but it's certainly a good reason.

If you want to avoid turning left, increase the drag on the right side of the aircraft. You can do this by increasing the drag on the right wheel with the right side brake, or you can increase the drag on the right wing by lowering the aileron there to increase the lift (and the drag also).

That difference in drag between the two wings when you deflect the ailerons is one cause of adverse yaw while flying. In this case the drag is helping you prevent yaw, but not creating yaw. If I'm a pedant for being clear about that, I accept the title willingly.

[CpnCrunch]

I'm not saying that, and I'm also being told I'm a pedant for making the distinction. Also I'm not saying it's the primary reason, but it's certainly a good reason.

If you want to avoid turning left, increase the drag on the right side of the aircraft. You can do this by increasing the drag on the right wheel with the right side brake, or you can increase the drag on the right wing by lowering the aileron there to increase the lift (and the drag also).

That difference in drag between the two wings when you deflect the ailerons is one cause of adverse yaw while flying. In this case the drag is helping you prevent yaw, but not creating yaw. If I'm a pedant for being clear about that, I accept the title willingly.

It was BPF who said it was the primary reason, and I thought you were agreeing.

The first problem with that theory is that most training planes have very little adverse yaw due to their design. The rudder will almost always be a lot more effective at yawing than the ailerons, as that is what it was designed to do. We're trained to keep the wings level with aileron and pointing in the right direction with rudder, so it seems odd to be hearing that we should be using the ailerons to prevent weathervaning. It makes much more sense to me to use the rudder. Sure the ailerons on some planes might help you keep the nose straight, but it seems to me that it would likely be a minor effect. It seems more plausible that the reason you use the ailerons while taxiing is to prevent the upwind wing being lifted up.

Anyway, all you guys (photofly/CS/BPF) have a hell of a lot more experience than me, so I guess it must just be my puny little brain just isn't understanding this. So please explain in simple terms where the flaw in my logic is so that us simpletons can understand

[photofly]

It was BPF who said it was the primary reason, and I thought you were agreeing.

I'm not disagreeing, either. I just know it works really well.

The first problem with that theory is that most training planes have very little adverse yaw due to their design.

At cruise speeds they have little differential drag. At slow speeds however, the differential drag is very demonstrable and real. Think about how the nose slews around when you use the ailerons in slow flight. And try the "rolls on a point" exercise - it's much more difficult and valuable at slower airspeeds.

The rudder will almost always be a lot more effective at yawing than the ailerons, as that is what it was designed to do. We're trained to keep the wings level with aileron

Not in slow flight, you're not, and definitely not in a stall scenario, either.

You're trying to oversimplify the controls of an aircraft. Controls affect the aircraft's movements around more than one axis.

[CpnCrunch]

At cruise speeds they have little differential drag. At slow speeds however, the differential drag is very demonstrable and real. Think about how the nose slews around when you use the ailerons in slow flight. And try the "rolls on a point" exercise - it's much more difficult and valuable at slower airspeeds.

Ah, good point. I actually tried the 'rolls around a point' exercise a few weeks ago in a 150, but gave up because there seemed to be almost no noticeable adverse yaw. I was at cruise speed, so I'll try it at a lower speed next time.

The rudder will almost always be a lot more effective at yawing than the ailerons, as that is what it was designed to do. We're trained to keep the wings level with aileron

Not in slow flight, you're not, and definitely not in a stall scenario, either.

You're trying to oversimplify the controls of an aircraft. Controls affect the aircraft's movements around more than one axis.

I was referring to crosswind landings/takeoffs here. I'm aware that the controls affect more than one axis (and that in itself depends on the plane's design), but generally we're trained to keep the wings level (or into wind) with ailerons and nose pointed in the right direction with rudder when landing or taking off. Yes, this is different from slow flight/stall where you're not meant to use the ailerons, which is worth bearing in mind.

[trey kule]

With a couple of exceptions, I believe the purpose of the rudder is to counteract adverse yaw in propeller aircraft.

The cycle of control is yaw, roll, pitch IIRC, and that seems to far more exception proof.

[Colonel Sanders]

he's taking the crosswind from the left

CAR 602.96(3)(b)

Stick all the way over into the crosswind
during landing rollout.

That's all you need to know.

[Shiny Side Up]

Ah, gotcha.

[Big Pistons Forever]

What I don't understand is why BPF/CS/Photofly are saying that the primary reason to use the ailerons while taxiing is to prevent weathervaning via the effects of adverse yaw. That just doesn't make sense for a variety of reasons. Care to explain?

I thought I was pretty clear in my post. I only commented on the effect of the adverse yaw caused by the deflected ailerons during the landing roll, I never mentioned this phenomenon during taxi because it of course does not exist to any appreciable degree.

[photofly]

I never mentioned this phenomenon during taxi because it of course does not exist to any appreciable degree.

Sure it does. And note that when taxiing into a headwind, just like the end of a landing roll, stick full over into the wind is still the recommended technique.

[trey kule]

While you are talking about the rudder while taxiing, what about the elevator?

[photofly]

While you are talking about the rudder while taxiing, what about the elevator?

Ailerons, not rudder, while taxiing.

[trey kule]

Ah yes. I am so overwhelmed by your indepth knowledge and wisdom of all things aeronautical, I sometimes err in what I type...

[Illya Kuryakin]

WWASGD
Also known as....what would a Seneca grad do?
Illya

[white_knuckle_flyer]

In a nose wheel a/c, how much weathervaning is really going on once the nose wheel is down ?

Is it significantly less than a taildragger ?

[Colonel Sanders]

I once met a fellow who claimed to
have groundlooped a helpless Piper
Cherokee.

To this day, I have no idea if he was
pulling my leg or not.

[pdw]

...what about the elevator?

The neutral position, except for any tail quartering in down position.

[Shiny Side Up]

In a nose wheel a/c, how much weathervaning is really going on once the nose wheel is down ?

Is it significantly less than a taildragger ?

Depends on what kind of nose wheel you have. If you have a steerable one, not much of a problem. If you have a castoring one though, your challenge may vary depending on how much travel it has. I find the RV-Xa models, being light with a big tail like to try and weathervane. They usually have a lot more travel to their nose wheel than most Diamonds or Cirruses. The Diamond don't have as much side area and are sort of streamlined don't have as much problem.

[Colonel Sanders]

I know a guy who stuffed his Grumman
AA5B (like the RV-Xa, castoring nosewheel)
into a snowbank with a crosswind last winter.

Ignore weathervaning at your own peril.

Far more important than a "greaser" landing
is keeping the mother straight.

It's incredibly simple: during a crosswind
landing, full stick over into the wind as you
slow down - every time.

[dirtdr]

I cant believe there has been 3 pages of discussion on this... but i have definately learned something.

Landed at czpc today. Winds gusting to 30kt right down the pipe. Landed pretty short and had a 3000 ft taxi to exit. Played with the "steering wheel" to steer at taxi speed (10kt groundspeed, 40kt airspeed). Turn wheel left, airplane goes right...

My instructor might have mentioned this during training, but at the time i was just too pre-occupied with not taking out the landing lights..

[Colonel Sanders]

My instructor might have mentioned this during training

You mentioned you spent $18k and 72 hrs
getting your PPL ... I guess you didn't spend
much time doing slow flight or stalls or spins?

You probably aren't aware of CAR 405.14
which says:

Flight training that is conducted using an aeroplane or helicopter shall be conducted in accordance with the applicable flight instructor guide and flight training manual

TP975E is the "Flight Instructor Guide".
And on the subject of slow flight it says:

Direction is an important consideration, and every effort should be made to control adverse yaw with rudder ...

Slow flight is not an exercise to be covered and forgotten

Demonstrate control of yaw to achieve co-ordinated flight;

Your FTU not only did a poor job of teaching
you (for $18k and 72TT) it looks like they
couldn't give a flying f__k at a donut about
the regulations, either.

[white_knuckle_flyer]

My instructor might have mentioned this during training

You mentioned you spent $18k and 72 hrs
getting your PPL ... I guess you didn't spend
much time doing slow flight or stalls or spins?

You probably aren't aware of CAR 405.14
which says:

Flight training that is conducted using an aeroplane or helicopter shall be conducted in accordance with the applicable flight instructor guide and flight training manual

TP975E is the "Flight Instructor Guide".
And on the subject of slow flight it says:

Direction is an important consideration, and every effort should be made to control adverse yaw with rudder ...

Slow flight is not an exercise to be covered and forgotten

Demonstrate control of yaw to achieve co-ordinated flight;

Your FTU not only did a poor job of teaching
you (for $18k and 72TT) it looks like they
couldn't give a flying f__k at a donut about
the regulations, either.

This may be a little harsh. My instructor, for example, was very thorough regarding slow flight and how coordinated flight was absolutely essential. Although I'm not clear to what degree he distinguished between adverse yaw from slipstream and adverse yaw from aileron drag.

However, aileron hard over into the wind upon landing, while absolutely taught, was not presented as a means of overcoming weathervaning. As I mentioned earlier, it was always a "Don't allow the upwind wing to gather additional lift" thing.

That said, if I teaching someone how to drive a motorcycle, I would certainly be remiss if I did not teach them that the need for counter-steering increases as your speed increases. And if I wasn't getting paid for the instruction, I probably wouldn't even bother talking about the reasoning behind it. But if I was getting paid, and if the physics behind counter-steering had other applications in motorcycle riding ( does it ?) then I would definitely do a more thorough job in explaining why it works.