Does anyone teach this?

[lhornaday]

I am looking at wind correction angles while flying ground reference maneuvers. Not on straight leg segments, but rather while in turns.

The only maneuver guide that states anything about it is in the FAA's airplane flying handbook and it is vauge. Wording from FAA:
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S-turns: To accomplish a constant radius ground track requires a changing roll rate and angle of bank to establish the wind correction angle.

Just as S-turns require that the airplane be turned into the wind in addition to varying the bank, so do turns around a point.
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I am debating whether a wingtip reference line can be maintained on a ground point in turns around a point , or if the wind correction procedures should be used (assuming some wind).

How many of you CFI's teach this?

opcorn:

 

[tgrayson]

I am debating whether a wingtip reference line can be maintained on a ground point in turns around a point ,

No. We do that during 8's on pylons and the result is NOT a circle of constant radius, which the Airplane Flying Handbook points out.

 

[MidlifeFlyer]

Me neither. Not for the constant altitude, constant radius, constant airspeed private pilot ground reference maneuvers. The FAA's flying handbook explains it just fine, except that it tends to avoid talking about how its really a visual maneuver and that the crab and change in bank angle is a natural result of flying that circle or S or rectangular pattern.

 

[lhornaday]

No. We do that during 8's on pylons and the result is NOT a circle of constant radius, which the Airplane Flying Handbook points out.

Where should the greatest angle of crab be during a TAP? I am guessing when directly in the crosswind.

 

[tgrayson]

Where should the greatest angle of crab be during a TAP? I am guessing when directly in the crosswind.

Agreed. A direct downwind or upwind doesn't need any crab at all.

 

[lhornaday]

And the last thing, the one I can't figure out, is how the crab angle is established considering:

- The bank is the steepest on downwind side; and
- A crab angle is somehow reached on the crosswind side while there was supposed to be a constant bank angle decrease from the downwind point.

Is my confusion clear?

FAA: "During the downwind half of the circle,the airplane’s nose is progressively turned toward the inside of the circle;"

Is the change in groundspeed what causes the crab or a specific pilot input?

 

[Joe Gremlin]

I am looking at wind correction angles while flying ground reference maneuvers. Not on straight leg segments, but rather while in turns.

Not for nothing but if someone asked me to do this it would just confuse the heck out of me. How you can establish a wind correction 'angle' in a turn? When you're turning, any angle you establish is going to be constantly changing because... well because your position in relation to the wind will be constantly changing. Isn't it simpler just to teach students that they need to bank more or less (i.e. turn faster or slower) according to what the wind is doing to their ground track?

 

[lhornaday]

Not for nothing but if someone asked me to do this it would just confuse the heck out of me. How you can establish a wind correction 'angle' in a turn? When you're turning, any angle you establish is going to be constantly changing because... well because your position in relation to the wind will be constantly changing. Isn't it simpler just to teach students that they need to bank more or less (i.e. turn faster or slower) according to what the wind is doing to their ground track?

Agreed! But we've been FAA 'rolled. If it is in the books it is game for a checkride bust.

 

[Joe Gremlin]

Roger that.

 

[tgrayson]

Is the change in groundspeed what causes the crab or a specific pilot input?

No, it's the change in flight path that causes a crab. In a normal turn, the flight path is tangent to the circle that you're flying. With a wind, the flight can't be tangent on the crosswind sides, the flight path is slightly at an angle with the circle in the direction of the wind.

The bank continually changes the direction of the flight path, so you need to adjust the bank angle to produce the correct flight path at each point around the circle.

 

[poser765]

No, it's the change in flight path that causes a crab. In a normal turn, the flight path is tangent to the circle that you're flying. With a wind, the flight can't be tangent on the crosswind sides, the flight path is slightly at an angle with the circle in the direction of the wind.

The bank continually changes the direction of the flight path, so you need to adjust the bank angle to produce the correct flight path at each point around the circle.

The crab in turns around a point is really easy to see on the headwind side. When you are doing this with strong wind that requires little bank it seems to me to be easier to see that you ARE actually crabbed. The bank is less, and the rate of turn is less so you have more time to perceive that you are not tangent to the circle.

 

[MidlifeFlyer]

And the last thing, the one I can't figure out, is how the crab angle is established considering:

I touched on this earlier but watch out for confusing the theory of turns around a point with the flying of turns around a point.

So far, I haven't seen a pilot successfully fly turns around a point by looking inside the cockpit and thinking, "now I'm heading crosswind to downwind so I will reduce my crab and steepen my bank." OTOH I've seen a good number do all that by simply visualizing a circle and flying around it (sometimes with the cockpit instrument covered).

Don't get me wrong - understanding the theory is very important - it allows the pilot to anticipate what is likely to happen, as they go around the circle, notice the changes quickly so that the changes in control inputs are immediate, small and smooth, and understand why those effects and changes take place.

The crab angle is established by flying the airplane, not by theorizing in the cockpit.

 

[lhornaday]

Thanks to you all. I am understanding the need for a crab angle clearly now.

It just isn't clicking how we arrive at the crab angles on the crosswind points.

FAA again: "Because of the decreasing groundspeed and rate of closure while approaching the upwind heading, it will be necessary to gradually shallow the bank during the remaining 90° of the semicircle, so that the wind correction angle is removed completely and the wings become level as the 180° turn is completed"

It seems as if it is saying that these crab angle should be made intentionally with deliberate effort on the pilot's part. I'm just not sure how to explain how a student should plan to arrive at the crab angles.

Are you guys letting them visualize the flight path on their own, or are you teaching them to be at a crab angle on the crosswind points? MidlifeFlyer, are your students doing it naturally without coaching from you?

 

[tgrayson]

It seems as if it is saying that these crab angle should be made intentionally with deliberate effort on the pilot's part. I'm just not sure how to explain how a student should plan to arrive at the crab angles.

MidlifeFlyer's point was that this is primarily a visual maneuver. It's possible to do a somewhat decent job at it without having any idea of the theory. If you get too close, take out some bank; if you start getting too far away, bank more.

Understanding the theory helps the pilot know what to expect and make the maneuver more smooth, but he should never focus on it to the extent of failing to look outside at the ground.

 

[lhornaday]

Ok, thanks. I didn't know if I should start making this a standard part of the maneuver explanations or file it under "gee whiz". I'll keep it on reserve for CFI applicants and students that wish to know.

... now back to that pitch vs power discussion

 

[jrh]

I don't understand why turns around a point need to be so complicated.

To fly a circle, groundspeed and rate of turn have to be proportional. High groundspeeds need high rates of turn, while low groundspeeds need low rates of turn.

In level, coordinated flight, bank angle determines rate of turn.

That's about it.

 

[MidlifeFlyer]

MidlifeFlyer, are your students doing it naturally without coaching from you?

tgrayson understood what I'm trying to say.

Ground reference maneuvers are one of those things I spend some time on the ground with so that the theory behind it is understood.

In the air, I haven't had to "coach" bank or crab. Most of the errors tend to be related to (a) the setup (they are still configuring the airplane and are not already stable on power, altitude, airspeed when the enter the maneuver, (b) trying to fly the maneuver on instruments (at which point I cover the ones I think they are chasing) or (b) making turns and banks based on what they imagine is happening instead of what is happening.

This is, after all, a ground reference maneuver. We're talking about the Tower telling a pilot to make a 360 in the pattern for spacing. The object isn't to make banks and crabs. It's to fly a constant radius circle around a point on the ground. If the student "sees" the circle an a series of points on the ground that makes up the circle, it's hard not to do it properly.

The "coaching" is in having the student look at the right things.

I think you may be too focused on the trees and missing the forest.

 

[lhornaday]

tgrayson understood what I'm trying to say.

Ground reference maneuvers are one of those things I spend some time on the ground with so that the theory behind it is understood.

In the air, I haven't had to "coach" bank or crab. Most of the errors tend to be related to (a) the setup (they are still configuring the airplane and are not already stable on power, altitude, airspeed when the enter the maneuver, (b) trying to fly the maneuver on instruments (at which point I cover the ones I think they are chasing) or (b) making turns and banks based on what they imagine is happening instead of what is happening.

This is, after all, a ground reference maneuver. We're talking about the Tower telling a pilot to make a 360 in the pattern for spacing. The object isn't to make banks and crabs. It's to fly a constant radius circle around a point on the ground. If the student "sees" the circle an a series of points on the ground that makes up the circle, it's hard not to do it properly.

The "coaching" is in having the student look at the right things.

I think you may be too focused on the trees and missing the forest.

I understood your post. I was trying to drawl from your experience. I thought maybe you had noticed some students using different techniques.

 

[lhornaday]

I don't understand why turns around a point need to be so complicated.
...
In level, coordinated flight, bank angle determines rate of turn.
That's about it.

I know we can all do a pretty good job flying in a circle without putting much though into it. I'm not suggesting that students are taken to in depth with the theory. But as high time instructors, I think we can examine things a little more closely than student pilots do, even if it is only to our benefit.

I was originally wondering what other instructors were teaching on this subject. I assume by the replies that only 20% or so explain the necessity for the crab or were even aware of it.

I agree with your statement, bank angle does determines the rate of turn. But consider the airplane in both of the crosswind conditions (I circled them in the picture). Saying that bank angle only can keep the airplane on the upwind half from being blown in, and the airplane on the downwind from being blown away doesn't make sense. The groundspeed is the same at both points, also the bank angle is. So there must be a crab at both points to prevent drift.

Even though I understand the theory now, I still agree that it is only a ground reference maneuver. It can be flown in many ways. Some people just like to dig deeper.

Thanks again guys.

 

[MidlifeFlyer]

I understood your post. I was trying to drawl from your experience. I thought maybe you had noticed some students using different techniques.

The only thing I've really noticed (and I have much less experience that most think - I've never taught more than very part time) is that pilots who "see" the circle and fly it do better than those who don't.