Making Turns with rudders

[hinhin]

Have anyone heard of the technique of initate turns with rudder , and followed by ailerons to make a coordinated turn(instead of banking first then the rudder)?!

One of my friends just told me that his FI taught him this way to minimize the diffculties on cross-control during a coordinated turn. Any comments on that?

[maximus610]

Never heard, but I do turns only with rudder when simulating jammed aileron/elevator (helping, of course, with power and trimmer).

[fireflybob]

Some good stuff here:-

Understanding the use of rudder: Its most important use is preventing yaw (http://www.empire-aviation.com/flight-instructors/john-e-mclain/understanding-the-use-of-rudder.html)

[9 lives]

Have anyone heard of the technique of initate turns with rudder , and followed by ailerons to make a coordinated turn

Definitely! I most commonly fly this way. It is my intent, of course, that there be nearly zero delay between rudder application, and aileron, so as to maintain a well co-ordinated turn. If you're sloshing the ball left and right, stop it, no excuses!

This habit came from flying STOL kitted Cessna's and in particular taildraggers, The addition of the STOL kit to a Cessna wing includes aileron gap seals, which make the ailerons more effective, so just cranking the control wheel around without regard for the rudder pedals will create an uncoordinated turn. By leading with a bit of rudder, I find the plane seems more happy.

[MrAverage]

We teach (as I was taught to teach) aileron and rudder at the same time, thereby maintaining balanced flight. This seems to agree with the word coordinated. We mainly use Cessna 152/172 and "Cherokee" types. Surely leading with rudder would immediately upset balance?
I'm happy to be convinced otherwise.

[Duchess_Driver]

Like everything, proper instruction is key here as is aircraft type. Some need rudder, some don't. My boss smacks my head for using rudder in the Duchess... in the Cub - different story. AIrliners, different again....

What I find so difficult to accept is that a PPL with a reasonable amount of time places 'a bootful' of rudder followed (at some stage later) with aileron to 'balance' and co-ordinated the turn. I fear for this pilot being low and slow and then 'conditioning' takes over leading to stall, spin, crash, burn, die.

In essence, I preach and teach coordinated use of both controls. In practice, I often correct 'turbulence' induced roll with a 'touch' of rudder. Hypocritical perhaps....?

[MrAverage]

........and I have read the link.

[hinhin]

Definitely! I most commonly fly this way. It is my intent, of course, that there be nearly zero delay between rudder application, and aileron, so as to maintain a well co-ordinated turn. If you're sloshing the ball left and right, stop it, no excuses!

This habit came from flying STOL kitted Cessna's and in particular taildraggers, The addition of the STOL kit to a Cessna wing includes aileron gap seals, which make the ailerons more effective, so just cranking the control wheel around without regard for the rudder pedals will create an uncoordinated turn. By leading with a bit of rudder, I find the plane seems more happy.


However, isn't there a delay in the ailerons (although its more sensitive than the rudder input )in that case?

when apply rudder followed by ailerons there should be a skidding introduced in the first place?

Btw will instructors have a definition of which technique is correct when it comes to flight grading?

[hinhin]

........and I have read the link.
And I have read the link as well......


Just to clarify is that really a rule of thumb that when making a certain deg of turn, the angle of bank should always be less than that?
Coz quite contrary to what i have learnt in the past is that lets say doing a 30 deg turn first you bank the a/c to 30 deg, then kick the ball in , then apply back pressure so that the VSI reads less than 100-200 ft /min, then adjust the back pressure again...

Anyone can share how to make a good coordinated turn then?

[9 lives]

Unless intended by the pilot otherwise, the ball should be in the middle all the time. A pilot new to an aircraft is entitled a little opportunity to harmonize with the plane. Like cornering a car new to you, you might drift a bit in the lane the first turn or two, while you get the feel for the steering. But after a bit of driving, you should be able to anticipate how much to lead with the steering to stay in the middle of the lane. The same applies to applying the right amount of rudder in a turn. Yes, some planes are none, other planes are lots - your duty as a pilot is to learn what the plane you are flying needs, and fly the plane as you intend - ball in the middle.

Some planes are beautifully harmonized (I like the Bellanca Viking for that), others casual (most Cessnas). Cessnas demand some attention to the rudder to make coordinated turns. If a Cessna's wings have been modified, they will be even less well harmonized. Sometimes the tail of an aircraft will also be changed, but not as often as should be.

If you compare the dorsal fins of early, mid life, and late manufacture Cessna 180 and 185, as an example, you can see a grown of understanding as to optimizing rudder effectiveness. The dorsal fin changes are not so much for "ball in the middle" characteristics, but do very much affect rudder effectiveness. Then consider the further requirement for a ventral fin with some floatplane modifications, but not others - on the same aircraft type.

There is a lot of testing and design behind this, and then you the pilot must be aware of, and master the last bit. But, in all cases, you must be aware of slip/skid, and apply rudder as required - no lazy feet!

[rotorfossil]

There is no one size fits all technique for the use of aileron/rudder on entry to turns. A lot depends on the amount of adverse aileron yaw exhibited by a particular type. Some earlier types with non differential ailerons and gliders with very long wings do need to lead (slightly) with rudder. As an extreme example, on most WW1 fighters, rudder was the primary control due to the huge adverse yaw. Another variable is the yaw stability or lack thereof, particularly noticeable on some seaplane conversions where coordinated rudder/aileron is necessary for a tidy entry an rollout. In the end, you learn what works on a particular type. Generally as understanding has advanced, the most modern types require very little rudder for coordinated turns.

[s4ex]

I'm not an FI, and just received my PPL(A) this summer, but hope to be working towards FI for the next few years, so don't get too agressive if my words don't make much sense now.
I suggest, that the FI, telling to initiate turn with rudder, would possibly try to teach student always remember about the rudder, as opposed to the ordinary situation, when students do forget it, using alilerons only. In general, I wouldn't consider it a good technique, though, since starting with rudder might already bring the aircraft out of balance during the entry if the ailerons are delayed (even though corrected after aileron application). But for a student who just starts flying, it might give a better feel for the rudder in a turn, provided that a proper theoretical explanation is given. On the other hand, not being properly explained, it is a high risk of developing bad habits and wrong understanding of flight controls.

The article is good, btw, thanks. Will try it out, next time I go flying to convince myself it works :)

[hugh flung_dung]

I must be getting even older and crustier than I thought. What a load of bolleaux.
Adverse yaw is caused by differential drag which (mostly, in this case) results from differential lift; adverse yaw is counteracted with rudder. The end.
Different aircraft require different amounts and timing of rudder input (personally, I found the Tiger Moth and Luscombe a bit tedious in this department) but the feet quickly learn what to do if the owner of the feet looks over the coming while making aileron inputs. A very good way to train the feet (or the owner of the feet) is to visually hold heading while banking one way and t'other at a range of speeds.

Apropos of not very much: as a guide, for smooth parting of the air molecules and non-spillage of drinks, the bank angle should equal approximately half the heading change.

HFD

[BigEndBob]

"the bank angle should equal approximately half the heading change"

that's sounds like fun, will try it tomorrow :)

[Cole Burner]

"the bank angle should equal approximately half the heading change"

that's sounds like fun, will try it tomorrowJust don't try it on a 360 - could end in tears :E

[Big Pistons Forever]

I think people are over thinking this. You want to turn ? Then roll the aircraft into a banked attitude and while you are doing that you put in the appropriate amount of rudder to keep the airplane balanced. Not turning fast enough, bank more......simples

[9 lives]

the bank angle should equal approximately half the heading change.

So if I want a heading change of 180 degrees, my angle of bank should be?

I don't think I'm grasping the concept.....

[hugh flung_dung]

Hmmm, emailing and "foruming" while relaxed in a hotel room is never a good idea :\ ... I missed the (hopefully obvious) bit at the end : "up to your bank angle limit".
I found that some studes had the idea that they always needed to use 30 degrees (or bank for rate 1 when I/F) and using a guide of "half the heading change" seemed to help them.

HFD

[9 lives]

The only "limit" which may be imposed upon bank angle of which I am aware would be that of my national (Canadian) regulations, where greater than 60 degrees is defined as "aerobatic". Otherwise, bank angle is not limited, that I am aware.

I think I see the concept now, though I'm always cautious about expressing "limits" where the are not imposed from aircraft limitations or regulation. An example of this would be crosswind "limits", which 99% of the time are not actually limitations, just a required statement in a Flight Manual. They are guidance, but not actually limiting.

[Consol]

I seem to remember being told to turn a Maule by rudder first then ailerons to balance. It worked, kept the ball nearish to the centre. Not suitable for most aircraft of course.

[hugh flung_dung]

The limiting bank angle will depend on a large number of things, speed and airframe being the major ones. If you are teaching PPL studes then 30 degrees might be appropriate. If you are on instruments I assume you're familiar with the formula for R1 bank angle. Anything else can be found in the standard FI manuals.

Yes, crosswind is "max demonstrated" and not a limit. It is perfectly possible to operate beyond max demo with a range of techniques, including differential thrust.

HFD

[BigEndBob]

Maule, what ailerons, dreadful aeroplane, well at least the one I have flown.

[Centaurus]

My boss smacks my head for using rudder in the Duchess

That sort of boorish behaviour by an instructor should be reported to the CFI who should take action to discipline the instructor by immediate dismissal. In fact you should return the compliment in spades by hitting the prick back. Never tolerate idiots like that.:mad:

[Tee Emm]

They are guidance, but not actually limiting.
http://www.pprune.org/images/statusicon/user_offline.gif http://www.pprune.org/images/buttons/report.gif (http://www.pprune.org/report.php?p=9600729)


But be very wary of ignoring the guidance published in the manufacturer's flight manual or POH. If you prang the aircraft because you deliberately chose to disregard the official advice then the insurers won't pay up and their lawyers will be after you real quick.

[Thud105]

Use of the rudder is very dependent upon the airplane flown. Maybe the OP's friend's FI was an old F-100 or F-4 jock? Old habits can die hard.....................

[LOMCEVAK]

In general terms, control inputs are made either as a reaction to a cue, in this case an observed yaw or slip ball deflection, or in anticipation of a predictable response. In a well coordinated turn the rudder input should be coordinated with the aileron input such that no yaw occurs. If the yaw due to aileron is excessive such that a significant adverse yaw rate is generated rudder free the there may be an advantage in 'leading with rudder' because less rudder will be needed because it is only the yawing moment due to rudder that needs to be countered and not also a yaw rate that needs to be stopped.

If an aeroplane has low static directional (weathercock) stability then at a constant bank angle rudder will be needed into the turn to keep the slipball central but this is a different aerodynamic requirement to that for opposing aileron induced yaw.

In aeroplanes that have low aileron power but strong lateral stability (dihedral effect) it may be optimum to use rudder to generate sideslip and thus a rolling moment in the direction of turn in addition to rolling with aileron. This is not a coordinated turn but a specific technique for some aircraft. And then there is the F4 above 17 units AOA ....

[9 lives]

But be very wary of ignoring the guidance published in the manufacturer's flight manual or POH. If you prang the aircraft because you deliberately chose to disregard the official advice then the insurers won't pay up and their lawyers will be after you real quick.

Not so fast.... If you had an accident while operating the aircraft within its limitations, and with diligence, you should not be expecting adversery from insurers nor lawyers. The aircraft manufacturer is required to state a "demonstrated crosswind" value, which must be at least 0.2Vs0 (FAR 23.233). Manufacturers don't typically publish a higher value, because they are not required to. It is also worth noting that the demonstration of crosswind capability at 0.2Vs0.

It is worth noting that this requirement must be met without unusual pilot skill - so it must be easily achieved. So if a pilot can apply extra skill, and accept a more intense crosswind, without being negligent, they can be confident that they are not exceeding a limitation of the aircraft.

If in doubt, fly the approach. If you can maintain the runway centerline down final, landing should be within you skill. If you cannot maintain the centerline, and smooth control of the aircraft, you should not attempt to land on that runway in those winds.

Modern flight manuals /POHs are written in a particular format, with a distinct limitations section, which is limiting, approved sections, which are obviously approved, but may not be limiting, and unapproved sections, which are or information. It's wise to be familiar.

For those wanting a very good treatise on the aerodynamics of Cessnas, I highly recommend: Cessna Wings for the World, by Thompson. It will tell you what you want on know about using the rudder in a Cessna.

[9 lives]

So after four hours of plowing snow from my apron and runway, and sweeping off my 150, I rewarded myself with a flight today. It's a straight out of the box 1975 150M, with a Horton STOL kit.

When I rolled into a rate one turn, with the objective of not exceeding rate one, to a 30 degree bank, the ball would be more than one ball out by the time that the 30 degree bank angle was achieved, if I did not apply pro turn rudder within two seconds of applying the aileron. If I lead the turn by one second with rudder, or the application of rudder and aileron were simultaneous, the turn could be co ordinated by modulating the rudder which had been applied. Leading with rudder did un coordinate up the turn, though leading with aileron would.

The STOL kit on my 150 does affect these characteristics, so I would agree that not all 'planes are the same. But this is the characteristic of one of mine.