Yaw is no Yawning Matter

[djpacro]

Very good article in AOPAA's Australian Pilot magazine this month by Rob Knight.

 

For nearly 45 years I have been teaching effects of controls, and for 15 years assessing other pilot's aircraft handling skills. During this time I have recognised that too many pilots find flying in a straight line is a difficult manoeuvre.

[poteroo]

Rudder is the most useful control in turbulence and we teach its' use for this very early in ab initio training. It makes keeping wings level on approach a heap easier to achieve and allows the student to focus on their aiming point without 'snaking' all over the place.

 

Couldn't agree more with his sentiments. Wish he'd summarised the article though, so the take-home message was emphasised.

 

happy days,

 

 

[dutchroll]

Rudder is the most useful control in turbulence .......,,,,It makes keeping wings level on approach a heap easier to achieve and allows the student to focus on their aiming point without 'snaking' all over the place.

Depends what you're flying! I have to take that cassette out and tuck it safely out of sight & mind in the bottom drawer when I go to work! ;)

 

 

[facthunter]

You've got yaw dampers to do it for you, so you are spoilt. The clever CM2 that snapped the rudder off an Airbus didn't understand the inertia forces involved with yawing a big aircraft. Using rudder is very important but like all things must be understood. Further effect of rudder is something that should be fully understood, including flying with misrigged airframe or out of balanced rudder use. Nev

 

 

[DrZoos]

Yawn...zzzz

 

 

[facthunter]

Hardly encourages one to contribute more, does it? Nev

 

 

[dutchroll]

I think he was joking (given the title of the thread). Or at least I hope......

 

 

[Contact Flying]

I don't have access to Rob's article so forgive me if he has already covered this. We instructors need to teach good rudder usage countering adverse yaw in coordinated turns. In 31 years of teaching flying, however, I have found that students and flight review (every two years in US) pilots do have problems with keeping the longitudinal axis aligned with a target in cruise, on the localizer, and on the final to landing visually in a no wind or with the wind right down the runway landing.

 

First, why does this longitudinal alignment problem not come up as often in a side slip to a crosswind landing? Is this a clue to what is being done wrong in calm air. Too many pilots try to make coordinated turns on final. This causes the snaking Poteroo mentioned.

 

Engaging a target, enemy on the ground, numbers, distant true course feature, centerline on takeoff, etc., requires that we align the longitudinal axis of our aircraft with the target using rudder only. The use of coordinated aileron is what is confusing the issue and causing snaking. Just like in the side slip to counter drift with a wing banked into the wind, we hold the nose (between our legs in side by side aircraft) on the centerline with rudder. It is like patting your head while rubbing your tummy. Or like using a backhoe effectively or hovering a helicopter.

 

This rudder control, except in an upset by gust or whatever, needs be dynamic and proactive. If we just push a rudder and then release, static and reactive, the wing opposite the rudder pushed will speed up in the yaw and rise a bit. That is not a problem, in smooth air, if we move the rudders to make the nose go just left of target, just right of target, repeatedly all the way off in takeoff or all the way down final and rollout in landing. It is this dynamic, proactive rudder or anti-torque pedal movement while locking the wing or tip path plane level with aileron or cyclic, this uncoordinated control usage, that makes us a pro on takeoff, keeping the wing level in cruise or on the localizer, and on landing.

 

 

[facthunter]

You are preaching to the converted as far as I'm concerned, Jim. If you have a tailwheel it's part of your training, but may nonetheless have not been fully explained. T/W these days are somewhat of a rarity. Some of the more basic U/L designs have a lot of adverse yaw which you might like to address. Nev

 

 

[djpacro]

Contact, I wish you had been around a few years ago to participate in a discussion on the instructors forum here. I got beaten up severely for making comments consistent with yours. I no longer have access to that forum so I'm unable to repeat my own comments here.

 

 

[Contact Flying]

djpacro,

 

I am not popular with those in positions of power here either. As instructors, we are obliged to justify what we teach. Finding it in a manual somewhere is not sufficient. If what we are teaching is not consistent with what is actually happening, we owe it to our students to find a technique that will address their concerns and physical reality.

 

Because the techniques used by we who work low level every minute of every hour don't fit comfortably with the school solution taught at the airport, we crop dusters and pipeline patrol pilots have become, to the Federal Aviation Agency, "those of whom we do not speak."

 

 

[Garfly]

The Instructors Only thread that djpacro refers to spilled over into the general forum here:

 

http://www.recreationalflying.com/threads/steering-on-final-with-rudder.112345/

 

 

[knirob]

I don't have access to Rob's article so forgive me if he has already covered this. We instructors need to teach good rudder usage countering adverse yaw in coordinated turns. In 31 years of teaching flying, however, I have found that students and flight review (every two years in US) pilots do have problems with keeping the longitudinal axis aligned with a target in cruise, on the localizer, and on the final to landing visually in a no wind or with the wind right down the runway landing.First, why does this longitudinal alignment problem not come up as often in a side slip to a crosswind landing? Is this a clue to what is being done wrong in calm air. Too many pilots try to make coordinated turns on final. This causes the snaking Poteroo mentioned.

 

Engaging a target, enemy on the ground, numbers, distant true course feature, centerline on takeoff, etc., requires that we align the longitudinal axis of our aircraft with the target using rudder only. The use of coordinated aileron is what is confusing the issue and causing snaking. Just like in the side slip to counter drift with a wing banked into the wind, we hold the nose (between our legs in side by side aircraft) on the centerline with rudder. It is like patting your head while rubbing your tummy. Or like using a backhoe effectively or hovering a helicopter.

 

This rudder control, except in an upset by gust or whatever, needs be dynamic and proactive. If we just push a rudder and then release, static and reactive, the wing opposite the rudder pushed will speed up in the yaw and rise a bit. That is not a problem, in smooth air, if we move the rudders to make the nose go just left of target, just right of target, repeatedly all the way off in takeoff or all the way down final and rollout in landing. It is this dynamic, proactive rudder or anti-torque pedal movement while locking the wing or tip path plane level with aileron or cyclic, this uncoordinated control usage, that makes us a pro on takeoff, keeping the wing level in cruise or on the localizer, and on landing.

G'Day,

 

I don't have access to Rob's article so forgive me if he has already covered this. We instructors need to teach good rudder usage countering adverse yaw in coordinated turns. In 31 years of teaching flying, however, I have found that students and flight review (every two years in US) pilots do have problems with keeping the longitudinal axis aligned with a target in cruise, on the localizer, and on the final to landing visually in a no wind or with the wind right down the runway landing.First, why does this longitudinal alignment problem not come up as often in a side slip to a crosswind landing? Is this a clue to what is being done wrong in calm air. Too many pilots try to make coordinated turns on final. This causes the snaking Poteroo mentioned.

 

Engaging a target, enemy on the ground, numbers, distant true course feature, centerline on takeoff, etc., requires that we align the longitudinal axis of our aircraft with the target using rudder only. The use of coordinated aileron is what is confusing the issue and causing snaking. Just like in the side slip to counter drift with a wing banked into the wind, we hold the nose (between our legs in side by side aircraft) on the centerline with rudder. It is like patting your head while rubbing your tummy. Or like using a backhoe effectively or hovering a helicopter.

 

This rudder control, except in an upset by gust or whatever, needs be dynamic and proactive. If we just push a rudder and then release, static and reactive, the wing opposite the rudder pushed will speed up in the yaw and rise a bit. That is not a problem, in smooth air, if we move the rudders to make the nose go just left of target, just right of target, repeatedly all the way off in takeoff or all the way down final and rollout in landing. It is this dynamic, proactive rudder or anti-torque pedal movement while locking the wing or tip path plane level with aileron or cyclic, this uncoordinated control usage, that makes us a pro on takeoff, keeping the wing level in cruise or on the localizer, and on landing.

Hello Contact Flying,

If you want a copy of my piece on the evils of inadequate yaw training, contact me on [email protected] and I will forward one to you. Rob Knight.

 

 

[Contact Flying]

Thanks Rob,

 

I emailed you for it and also sent you "Safe Maneuvering Flight Techniques."

 

Best regards,

 

Jim

 

 

[Contact Flying]

Rob,

 

I read your article and totally concur with you on the need to teach proper rudder usage for yaw control in many situations in addition to adverse yaw control. Rudder is the best trim control on the airplane and the least used.

 

I soloed in a 90 hp Super Cub. No ADF, VOR, GPS, etc. With my fists filled with Sectional map and E6-B wis wheel, learning to keep the wings level with rudders only was a snap. Before the Practical Test Standards made the flight test a basic instrument flight test, we were taught to maintain longitudinal alignment with rudder only on final. Later in Army Cobra Gunship School, I learned that we keep our pipper on the target using anti-torque pedals and fore/aft cyclic only. WWII bombardiers used the rudder trim only to accurately put the Norden bomb sight radical on the target. Finally crop dusters make rudder turns in ground effect using aileron only to keep the wing level. Like you, I have observed many students and flight review pilots wing wagging all the way down final approach.

 

Unfortunately the rub our tummy while patting our head thinking that works so well for pilots using the side slip to counter crosswind drift doesn't easily transfer to the no wind or direct headwind approach. Pilots are fine with keeping the wing level with aileron while keeping the center line between their legs with rudder in a crosswind. But they go back to balanced turns on calm days. And what about those pilots using the crab to counter drift to round out and then put a wing down into the wind and use opposite rudder to the side slip. Many of those also wag the wings on final rather than keep the wing level with aileron and keep the offset pipper (directed course of butt to numbers) going down the center line. The same with gust upsets while cruising with or without a crab.

 

Anyway, it was great to find another instructor working hard to teach students the fine finesse and many useful abilities of the rudder.

 

 

[dutchroll]

Use (and usefulness) of rudder is very aircraft type-dependant.

 

As I've said previously, I have two flying cassettes: the "use that bloody rudder!" cassette, and the "don't touch that bloody rudder!" cassette. It's been that way most of my career. I have failed to change them over once or twice, with uncomfortable results either way.

 

 

[Contact Flying]

dutchroll,

 

You are correct, of course. After many years and many hours flying normal airplanes that all flew well and crashed well, I lost my right eye when a windscreen blew out on my pipeline C-172. Rather than go for a waiver, I did the Light Sport thing. I crashed an Ultraflight Challenger II because at about 100' in a steep energy management turn I found out the rudder didn't work to help get the wing back up. In John Boyd's terminology, I came "unglued" and it didn't crash well. Broken back, crushed leg, etc. etc. I had lost engines low in spray and pipeline planes ten times breaking two without missing a beat or hurting myself in any way. This one got my attention.

 

That said, we can expect and teach some common control techniques in certified airplanes and homebuilds built to certified standards. It is not responsible on the part of governments or instructors to just let the kids learn this stuff by hard knocks.

 

 

[facthunter]

I think the Challenger is subject to aileron reversal, due to insufficient wing resistance to twist. Not a plane I recommend. There are a few planes out there with dangerous quirks. Flapperons introduce special handling issues too.. Downwind situation base turns onto final, have to be watched for illusions of skidding. Nev

 

 

[djpacro]

CASA's MOS has lots of specs on required flying tolerances but nought on balance that I can see apart from words like "balance and trim the aeroplane accurately". First of all the instrument has to be accurately mounted in the panel. Secondly, consideration of the behaviour of the ball in dynamic conditions - refer the text in the attached photo.

 

 

Worth repeating that first sentence: "Many pilots are under the mistaken impression that coordinated flight and ball-centered flight are always synonymous" with the result that, unless absolutely steady conditions, they fly down final in a state of perpetual uncoordination. The Pitts standard instrument package does not include a slip ball yet it can easily be flown accurately in balance - except normal landings when many of us prefer to sideslip just so that we can see the runway.

 

As for flying the approach in calm conditions or direct headwind vs a crosswind - the discussion is irrelevant as there is always a crosswind component, its just that sometimes it is NIL.

 

 

[Contact Flying]

djpacro,

 

I like the idea that there is always a crosswind. Good emphasis of the need to control drift with bank angle and control longitudinal alignment with rudder, even in calm air.

 

Good description of how the slip/skid ball instrument. To emphasize the need to contact fly a visual approach with our eyes outside, I teach slip/skid using the visual horizon. When we are late with rudder to start a turn, a slip, the nose first goes away from the bank and then hangs up, moving too slowly for the angle of bank. There is relative wind noise, vibration, and pressure in the butt toward the turn. This is a very common thing.

 

We need to first have the student stomp a rudder in the desired direction of turn, a skid. We point out that the nose yaws quickly the way we pushed the rudder and the nose moves too quickly for the angle of bank. There is relative wind noise, vibration, and pressure in the butt cheek away from the turn. This is very uncommon.

 

Thus we need to use the lead with rudder mind set. No, not so proper, but gets thing going in the right direction. We need to help the student keep his head out of the cockpit and use rudders to make the nose move across the horizon at the proper speed for the angle of bank. In steep turns, the nose should move quickly across the horizon and then across the earth below the horizon in the energy management turn. In a shallow turn, the nose should move slowly across the horizon.

 

Thanks again for the lesson,

 

Contact

 

 

[facthunter]

Aircraft equipped with differential spoiler do it right. Lower L/D on the wing to lower on the inside of the turn. Warping wings and aileron aren't perfect. ALL of these controls use energy. Just a point in passing, as does requiring more lift in the turn. Nev

 

 

[Contact Flying]

Nev,

 

That makes a lot of sense. Stinson and one of those Cub clones are the only spoiler airplanes I have flown. Both flew well. Much agree that we don't need to load the aircraft and bleed energy in the level turn. Zoomies, jet jocks, can keep putting in more thrust until they pass out, but not us little guys.

 

Jim

 

 

[facthunter]

For aerobatics they ( ailerons) will stay no doubt, to work inverted. Throw those"frise" ailerons in the bin, though. Nev

 

 

[aro]

Secondly, consideration of the behaviour of the ball in dynamic conditions - refer the text in the attached photo.[ATTACH=full]39541[/ATTACH]

I had to google to find the context of that extract.

 

I hesitate to nitpick Rich Stowell, BUT he is describing an exercise rolling between 30 degrees bank each way while keeping the nose on a point on the horizon as coordinated flight.

 

I do not consider banking without turning - even temporarily - as truly coordinated. Rolling from 30 degrees one way to 30 degrees the other the nose SHOULD be moving across the horizon. As you roll through 15 degrees, the nose should be moving at the correct rate for a 15 degree banked turn etc. If you doubt it I am sure a glider or pusher aircraft with a yaw string would show it. I suspect the yaw string would show the ball to be surprisingly accurate.

 

The rate of turn for a particular bank angle increases with slower airspeeds, so the slower the aircraft, the more uncoordinated it will be if you hold the nose on a point as you roll into the turn. For a fast aircraft, it might be effectively undetectable.

 

 

[facthunter]

Your lift from the wings acts vertically from a line from wing tip to wingtip. If you incline that lift vector to one side by banking the aircraft, it moves (accelerates) towards the way the lift is tilted. It has commenced a turn because of the applied force. Nev