Low Level Flying Techniques: Cross Control

[flagold]

Cross control - when banking is impractical.

Practice:



In cockpit movements:


History of:







Problem & Recovery From:


Cockpit used for demonstration:



Movie of technique above:

Enjoy your flying!

Matt Mattson

 

[skukum12]

Thanks so much for spending time to put this video together.

 

[flagold]

Thank you. I don't know where you came in on this, but I had forgotten to add the diagrams and have since done so. Safe flying to you.

 

[flagold]

I've gotten some emails asking what am I talking about with the baseball - so I must not have done that very good so here goes . . .

The "baseball" is a hard ball of air developed with speed in ground effect. This ball of air is formed by compression & wingtip vortices - both trap it under the airplane. The "ball" is slippery - note the right wing is just slightly high - and the ball of air (you can see it) is shifted towards the left - because the right wingtip vortices are not as effective further from the ground at trapping air. This is an important concept in understanding why ground effect fades rapidly with height. It is why B-25 final runs were done at 30 feet or less (1/2 wingspan) to keep this hard ball of air built up they could maneuver on.

Look for the inner ball and the outer ball:



The inner ball - this is the ball we develop first on any takeoff if only briefly (most of us just climb out without ever thinking about it) and the one we intentionally try to develop on soft field takeoffs and ride along until we have sufficient air speed to get away from it (a soft ball of air - feels dangerous - this is because the wingtip vortices aren't very effective at slow speed in trapping air under the wing). At speed - this inner ball is extremely hard and is the ball we typically bounce off of and up when carrying to much speed into a landing (beginner's bounce).



The outer ball - this is only developed with speed - the wingtip vortices are working efficiently to trap air compressed by the wings and the effect is like (and the feel is like) riding atop a baseball. Just like riding atop any ball though - it moves - and wingtip high is what shifts it right or left - so we do our best to keep the wings level when riding the ball & use the rudder to aim the nose where we want to go. We want our wings level.



Just a note: I get a lot of emails a day - but any on this subject was too many and if I'm ever not clear on flying, let me know on the forum itself so I can clear things up fast for others who didn't ask. I only spoke briefly about this in the film and should have said more. I want no one hurt. My apologies.

 

[RVBottomly]

Thanks for that. After I first got my PPL in the early 80s, in winter, I spent a lot of time flying over a long iced over lake at different air speeds. For some reason I wanted to really learn about ground effect. Now that you describe it, it really does act like balls.


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[EdH]

Awesome video, thanks for posting. Please post more videos, I’d love to watch them. And as a dad with two young kids, thanks for the reminder at the end.


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[flagold]

Awesome video, thanks for posting. Please post more videos, I’d love to watch them. And as a dad with two young kids, thanks for the reminder at the end.


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You're welcome Ed (You too RV) - and yes, the message at the end is probably the most important I ever made in my life.

 

[dgapilot]

Kind of like counter steer on a motorcycle, or step taxi with a seaplane!


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[Kid Durango]

Flagold, you touched on this I think, but it appears the cross-controlled movements are made quickly. Is that correct? And how does one acquire that safely since ground effect is necessary? Forgive my ignorance here. Thanks

 

[flagold]

Flagold, you touched on this I think, but it appears the cross-controlled movements are made quickly. Is that correct? And how does one acquire that safely since ground effect is necessary? Forgive my ignorance here. Thanks

Thanks for asking that. Control inputs have to be smooth not necessarily hard or swift - and simply need to be what is needed to do the job at hand. We use what we need to aim the airplane where we want it to go (in the film they're attacking an airfield and throwing the nose 20 degrees to each side at the beginning to strafe - then they leave the last input (right rudder left aileron - enough to turn the airplane towards the airport, jump more trees and strafe the field (I picked this particular clip for practice because it shows all of it - extreme maneuvering of the nose side to side & changing course directions in ground effect). Most people would, on the face of it think they'd stall out doing all this - but they don't because they're riding that ball of air intentionally and it is very hard to fly into the ground. So we're also learning that as long as you're in ground effect, even with a big plane doing extreme maneuvering - it doesn't mean an automatic stall and crash.

How we were introduced to this: we first practiced this at altitude - picking a course 10 - 20 - then 30 degrees off the nose, leading with the rudder & holding opposite aileron to keep the wings level and hold altitude. Seeing if it took power to hold airspeed or not (and this depends on the time it takes to turn (how hard your rudder input is). If we could hold altitude and wings level up high, then we were allowed to go lower. In short, we're doing a technique to change directions our basic instructors try to break us of immediately: making course adjustments with rudder alone (they want synchronized flight). This is unsynchronized flight - we're down low where we can't use the wings for turns. Once we had a rough idea of how we change course - then we would fly down the airfield getting a feel for this ball of air that is ground effect.

I hope that helps - it doesn't take full inputs or fast inputs to change course - just use what you need to aim the nose and keep wings level until climb-out.

 

[Kid Durango]

Thank you very much for the thorough explanation! I’m with you now! My flight instructor had me practice moving the nose in a box formation to get the feel of the plane and to see just what the movements of the controls would do. We used to do this on our way to the practice area so as to make use of otherwise idle time. I felt boxing the wake in a glider benefitted from these type inputs as well. Again thank you. Ken

 

[dgapilot]

You're welcome Ed (You too RV) - and yes, the message at the end is probably the most important I ever made in my life.

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[Skywalker]

Yes, this is how to land a hang glider. When you feel the wing roll forward over the ball, the required nose-up control suddenly increases, that's your cue to flare as hard as possible, with no fear of a balloon. No "timing" involved. Years later in the Champ I would occasionally get pushed from behind and the nose would dip while in ground effect. I would always explain it with a tail gust, never occured to me to explain it as rolling off the front of the ball. Great post.

 

[Farmboy]

Inner pirate….embraced. [emoji16]


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[DJ]

Does gyroscopic effect not make a big difference between left and right level rudder turns? Maybe I missed that detail. Seems there would be some. It would be pushing the nose down in a right turn if I'm not mistaken.

 

[flagold]

Does gyroscopic effect not make a big difference between left and right level rudder turns? Maybe I missed that detail. Seems there would be some. It would be pushing the nose down in a right turn if I'm not mistaken.

Excellent. There may be some - but none I ever noted to any degree. Perhaps being in ground effect covers for that - I hadn't thought it down to that fine a point. In the practical it seems the rudder is supercharged when on the ball and turning is very easy (even too easy with a big rudder - you have to watch over shooting your mark) in ground effect.

Good on you for thinking it down that far. Makes me glad I didn't have to face flying a rotary . . .

 

[flagold]

First: The ones of you that wanted to learn this, you all have it down - no problems. I do occasionally get questions on YT though and this question was pertinent to post:

DB536: "Does being cross-controlled increase stall speed in a situation like that?"

Matt Mattson: Yes it does. Never try this close to your stall speed - we learned it at altitude and when we demonstrated ability to do it without losing altitude we were cleared to go down low (with an instructor), then we demonstrated it solo on the runway, and then we demonstrated it to their satisfaction in the field.

DB536 - Don't know if you're on the SuperCub.org site but there's a discussion on this and other low level and flying techniques in the art & science of flying. Have a great time with your aviation adventures!
__________________
I send people to "The Art & Science Of Flying" frequently since you guys are now the experts in my opinion.

Safe skies.

 

[flagold]

Just try to keep the wings as level as possible.

 

[flagold]

If any of you stall practicing this: stay in ground effect and handle it - do not climb out until control is regained.

As soon as you recognize the stall:

1. Full Power - we're going to power our way out of this
2. Keep Wings Level & Rudder Neutral - keep it that way until it starts flying again (momentarily in ground effect)

Good luck and safe skies!

 

[flagold]

This would be the full exercise:



As said above: we would do this at altitude with an instructor (usually Chuck Coe or Joe Rogers) in a 450 Stearman and then we were cleared to go low with Johnny Neile and then by ourselves in the field with the AgCat. The Cubs, Huskies, etc., being lighter are friskier in the the wind so alway have your hand on the throttle if you touch a tire or ham handle it like I did and stall. Power is your friend - use it immediately.

Steve: if these things are to large - just delete them. I'm good with it.

Safe skies to you. MM