Steep Turns & Slip Indicator

[emerydc8]

Hi Hardy,

If you get a chance, can you see if the slip indicator on your sim is showing about 1/2 a ball out to the right while doing a steep turn to the left (45 degrees of bank)? Maybe it's my sim. I actually have to step on the rudder opposite the direction of the turn (e.g., left turn -- right rudder) to center the ball. The opposite is happening on a turn to the right. Thanks.
Jon D.

Here is the situ. Just disconnect the A/T, A/P and F/D.

https://drive.google.com/file/d/0B-WRh0Hf7VdZVlJsOWFvNWk5cDQ/view?usp=sharing

[Hardy Heinlin]

Hi Jon,

if I don't pull on the yoke too hard the ball is nearly centered.

If I push the yoke, the ball falls to the ground due to the gravity being stronger than the centrifugal force.

If I pull on the yoke very hard, the ball moves off the curve due to the gravity being weaker than the centrifugal force.

It's indeed not easy too keep the ball constantly exactly centered during steep turns. I wasn't able to achieve this in real life either ...

In any case, you should keep your rudder centered; don't chase the ball with the rudder, I would say.


Regards,

|-|ardy

[emerydc8]

Hi Hardy,

Thanks for checking on this. Maybe it was just the sims that I flew, but I don't ever remember steep turns requiring any rudder to keep the ball centered. The FCTM doesn't discuss it either. From my experiences, this was always a feet-on-the-floor maneuver. Could the yaw damper be compensating for the slip/skid? Maybe Peter can chime in on this too.

[cagarini]

Guys, give up on your balls.... Use a string just like me :-)

I'll have to check later tonight. Interesting point... I always assumed the yaw damper(s) being functional will also play their role, even when the aircraft is "manually" being flown, right ?

Anyway, on one most of the gliders I fly, specially 18m class, most of the time on a coordinated turn, cross controls must be used ( out aileron, in rudder )

[Hardy Heinlin]

Jon, just a thought ... as we all know, maintaining altitude during steep turns is not as easy as during level flight: the elevator in this case is not just an altitude controller but also a heading rate controller. Small altitude fluctuations need to be compensated by larger elevator movements which in return cause large heading rate fluctuations. When the heading rate for the current coordinated bank angle is too low or too high, the ball moves off the center accordingly. The questions are (a) how sensitive the real slip indication is in this situation and (b) how much influence the real yaw dampers have at bank angles greater than 30°. -- I have seen great fluctuations when I was an active private pilot; in real planes and in the sims ...

[cagarini]

Hardy,

observing the "status" page I can see that rudder deflection ( by way of the yaw dampers ) happens only when we enter a sideslip.

As bank is initiated and roll rate still increasing there is initial deflection for coordination, but after that initial deflection the deflection is minimal if any at all, either in the sideslip state or if we pull the yoke.

Pulling the yoke does indeed result in marked "skid of the ball", as if too much rudder was being applied, but indeed the rudders cue seldom moves...

[Jeroen Hoppenbrouwers]

My non-pilot memory coughed up that you pretty much never use the rudders (in a 744), except:

1. To balance forces under asymmetrical thrust (quite static rudder pressure if you don't change thrust settings, more suitable to rudder trim);
2. To de-crab just before a crosswind touchdown (one swift application).
(3. On the runway at higher speeds, especially in crosswind.)

Approximate quote from one of the resident 744 drivers (then, long ago): "Stepping on the pedals is a sure way to totally screw up what was a reasonable approach".


Hoppie

[emerydc8]

I am certain that I never used rudder during a steep turn in any of the jet sims I've flown (DC-8, DC-10, 747, 744) and the ball was never out of alignment. Maybe the real airplane is different (I never tried it there).

I do remember a sim check airman once standing behind and to the right of my seat and showing me how good he was that he was able to do a steep turn using just his right hand and was still able to maintain altitude within 20'. I never touched the rudders while he was doing it and the ball was perfectly centered.

Just to be sure, I have asked a few others who would probably know. Still hoping to hear from Peter, though.

[Hardy Heinlin]

You need not use the rudders in PSX either. If there's something not perfect enough during steep turns then it's the ball indication, not the aerodynamic coordination. In one of the last updates I fine-tuned the elevator effectivity; perhaps this had a side effect on the "ball" instrument model. I don't know. I'll check that later ... My to-do list is now endless ...

[emerydc8]

Thanks, Hardy. Now that you mention it, I think this skidding/slipping during steep turns wasn't always like this in PSX or I think I would have noticed it earlier; so it very well could have been from an update.

I just heard back from a friend who is a B747-200 fleet standards captain. It is funny that he spends over 100 hours a month in the sim and I think his answer demonstrates how easy it is not to notice something when you're not looking for it. I suspect Peter can relate.

Yes, we do the steep turns with the feet on the floor. I have personally never watched the ball, to see if the turn was coordinated. I am usually too busy watching their altitude and airspeed, plus giving direction, to ever notice. Next time I will take a look. I am sure part of the reason we don't care is, because no one has stick and rudder skills from flying tail draggers anymore.

[Britjet]

As I think we all know, messing about with rudder input on a big jet us not a good idea (side loads etc).
In flight, the rudders are really a footrest unless asymmetric etc. As for steep turns, I understand what Jon's contact says about not noticing any rudder effect.
I'm afraid I haven't noticed what the sim does, and of course I have never tried it in the real aircraft.
I would say that it shouldn't go in the opposite direction though :-)
If I get chance I will try it in the sim.

Peter

[Will]

What about using the rudder in an upset condition? Is recovery from an upset also "feet on the floor?"

On the one hand, the rudder might bring the ship back under control, but on the other hand, aggressive rudder use led to the separation of the vertical stabilizer on AA 587 (Queens, New York).

[Britjet]

For upset situations - feet on the floor - most definitely. If you feel you are getting too fast in the dive it doesn't hurt to press the toe-brakes, however ;-)
Airliners are instrument platforms, built for comfort etc. They aren't designed to be aerobatic in any way.
A conversion course might spend at most 2 minutes doing steep turns - any more would be a waste of training resources and the pilots will never fly them for real.
PSX - and indeed full flight sims - aren't designed for such extreme flight envelopes.

Peter

[emerydc8]

Thanks for the input and confirmation, Peter.

What about using the rudder in an upset condition? Is recovery from an upset also "feet on the floor?"

In the sim, I have never needed rudder to recover from an upset. Most of us have seen the AA training video on youtube where they discuss using top rudder to keep the nose from dropping as you roll from an inverted attitude; but in the sim, altitude loss isn't as much an issue because you are usually not close to the ground when they give you the upset. You can recover without rudders and just lose a bit more altitude. Unfortunately, there is no time to experiment with minimizing altitude loss on upset recoveries in the sim -- You just do it and move on.

It would be nice, though, to be able to program a few unusual attitudes into PSX, like in the Level-D (nose high, nose low, inverted, etc.). But like Hardy said, his to-do list is getting endless and I know there are more important issues.

[CarlBB]

2. To de-crab just before a crosswind touchdown (one swift application).

Just been practicing from a saved situation with that in mind (one swift application) using a challenging crosswind. Yep.... really got there this evening - it bought a smile to my face and served as a reminder why A/P off in this is just sooooooo satisfying and rewarding 

Carl

[Britjet]

I just did a steep turn with up to 65 degs bank in the big sim. Balance remained exactly central throughout.
The VSI didn't move either...:-)
Peter.

[emerydc8]

Thanks for checking, Peter.

[Hardy Heinlin]

Modification now available in PSX 10.0.9-beta17:

http://aerowinx.com/board/index.php?topic=3685.0


|-|ardy