Yaw behavior is totally unexpected!

[Shaderhacker]

All:

 

I must be used to too many arcade flight sims. I've always expected that full rudder left or right will make the aircraft jinx to the left or right. However, with DCS:A-10, when I give it full rudder to either left or right, I end up rolling the aircraft. Totally not what I want. I'd like to jinx the aircraft to straighten it's heading. Even if I put small inputs to the rudder, the plane will alter it's heading but releasing the rudder puts it back to the original heading - again frustrating when trying to land.

 

Any tips?

 

-M

[EtherealN]

It rolls the aircraft since applying full rudder causes one wing to travel faster through the air than the other wing. A wing that goes faster, produces more lift. Thus your lift becomes uneven, and the aircraft rolls.

 

Your rudder is there for getting yourself to coordinated flight, not to turn. Turn through banking the aircraft. ;)

[bluepilot76]

It is known as a "secondary effect" of the control. This sort of thing is common with aeroplane controls. All part of the fun. And useful too; You could fly a whole approach and successful landing without ailerons by using your rudders.

[Pilotasso]

You must use opposite roll to compensate when yawing.

[Leto]

Have a look at the speed your a/c yaws. You can neglect the additional speed one wing has over the other. The lift of the wing on the side you yaw to is reduced due to vortex of the fuselage.

[Supersheep]

And I always assumed that this effect is caused by the rudders position above the center of gravity of the whole plane, so it does not only induce yaw, but also pitch via the created torque vectors...

 

 

Super-

[Pilotasso]

The rudders above the center of gravity actually produces yaw on the opposite direction to what you see. It happens the roll induced by the wings is stronger and predominates.

[Shaderhacker]

Damn. I have a lot to learn.

 

I plan on going to flight school in the Fall. I'm hoping this helps me understand the physics behind it all. I've had physics before, but not concentrated on aerodynamics. I hope the P-51D simulation can give me more of a real world comparison to the Cessna's I'm going to be training in.

 

Wow - just wow.

[Depth]

Only time I ever use the rudder is when lining up an attack run or when taxiing.

 

One (unconventional outside gliders) use of the rudder I sometimes/rarely do is a "slip", where an input of yaw is applied but a roll is also applied to force the frame in the opposite direction. The result is that your nose is pointing away from your actual heading. This gets very hard to control at extreme angles but the increased drag reduces airspeed more than speedbrakes would allow.

Edited May 9, 2012 by Depth

[effte]

'The secondary effect of rudder' is to roll in the the direction of the applied rudder - that's all you need to know.

 

Leto is the one who has it right, for the "interesting facts" part of it.

 

Aircraft are built to roll away from the direction of sideslip. Otherwise, the flight characteristics would be pretty poor. If you started to bank and didn't coordinate it with rudder, you'd sideslip which would increase the bank...

 

The tendency to roll away from the direction of sideslip is called lateral stability.

 

Lateral statility is affected by many factors. High wing aircraft have a higher degree of lateral stability, as the air streaming around the fuselage in a slip will increase the angle of attack of the upwind wing and decrease that of the downwind wing, causing more lift on the upwind wing and a stabilizing moment around the roll axis.

 

Swept wings also contribute significantly to the lateral stability, as the relative wind will be more perpendicular to the length of the upwind wing, creating more lift.

 

Dihedral, the V-shape of the wings, also contributes, as dihedral means increased angle of attack and more lift on the upwind wing. Dihedral is the method usually used to adjust the lateral stability. Thus, low-wing aircraft tend to have more dihedral than high-wing aircraft, and high-wing swept-wing aircraft often have negative dihedral.

 

Depth,

have a look at the ball during banking manoeuvres. Might make you want to reconsider your limited use of rudder. :)

 

Never use rudder to line up a shot. You must be coordinated when firing or your bullets will be off laterally. I don't think this is what you said you are doing, but it could be interpreted that way and cause problems for the unwary.

 

Cheers,

Fred

[EtherealN]

One (unconventional outside gliders) use of the rudder I sometimes/rarely do is a "slip", where an input of yaw is applied but a roll is also applied to force the frame in the opposite direction. The result is that your nose is pointing away from your actual heading. This gets very hard to control at extreme angles but the increased drag reduces airspeed more than speedbrakes would allow.

 

Sounds like very very old gliders to me.

 

Shemmps are WAY more efficient at modifying sink rate - which is actually the important thing, not speed reduction - if you end up having to reduce speed you've done something very weird, but the solution is to nose up a few degrees with shemmps fully deployed (to maintain sink rate), you'll slow down real fast. Faster than some are prepared for - I once felt certain I was about to see a serious accident as a pilot went way too nose-up right before the moment of landing, shot up and was in like 1 second at near-stall. And that's from an original position in the envelop where airspeed was stall+50% (which is the standard final for gliders, here).

 

The only cases where I've seen slipping used has been the veteran planes - when they fly things from the 50's and 60's. And in those cases it is specifically to handle sink rate, not velocity. (Though, it can be used in conjunction with other measures to reduce speed, of course, when you want to ensure you don't climb.)

 

All of that said though - I do use it to control my sink rate when I play Rise of Flight. Very rewarding. It's fun to do in the P-51 as well, as long as you balance it right you can do it pretty aggressively as an alternative to crash-dives (with how fast the P-51 gains speed in a dive, it even feels safer to use the slip. :) )

[effte]

It's great fun in the A-10 as well. :D

[Pyroflash]

..negative dihedral.

 

The proper term is Anhedral, though tehcnically negative dihedral is also correct. Also, don't forget the polyhedral (part of the wing is anhedral, while another part is dihedral) wings that aircraft such as the F-4 sported.

 

Never use rudder to line up a shot. You must be coordinated when firing or your bullets will be off laterally.[/Quote]I think what you meant to say is to not use rudder in order to line up the shot, but not be afraid to use it for correcting once you are lined up. A task isn't worth aborting because you made one mistake if you have the ability to compensate for it by other means. Otherwise 90% of flights would never take place, as no pilot that I have ever met has had a flight that has ever gone perfectly according to plan.

 

 

Again, not trying to pick at it, but this is a new guy, and incomplete information can only hurt his progress. It is important to let him know that he WILL make mistakes, but that it is possible to recover from those mistakes and not be discouraged by them.

 

Interesting information about the swept wings though. I never considered that they would be more stable.

Edited May 9, 2012 by Pyroflash

[effte]

Pyroflash,

negative dihedral and anhedral are synonymous terms, yes. Neither is more 'proper'. Well done.

 

I meant to say exactly what I said - do not use rudder to line up a shot, as it will cause your bullets to hit somewhere else than where you are aiming.

 

That you can use rudder to e g walk your fire or correct your fire if you didn't manage to line up properly is true, but I didn't mean to say that as I felt it would only confuse matters at this point. Feel free to add it to the discussion though, but do it without attempts at mindreading please.

[Pyroflash]

Then what am I going to do with this degree in psychic activity?

[Shaderhacker]

All you real pilots have already confused me.

 

Please talk to me as if I know nothing about "slip", lining up shots, etc.. I'm just trying to land properly at this point and trying to figure out the behavior of using rudder.

[yallu]

One (unconventional outside gliders) use of the rudder I sometimes/rarely do is a "slip", where an input of yaw is applied but a roll is also applied to force the frame in the opposite direction. The result is that your nose is pointing away from your actual heading. This gets very hard to control at extreme angles but the increased drag reduces airspeed more than speedbrakes would allow.

 

Gimli Glider. Unconventional? Yes... Working? Absolutely... :D

[effte]

All you real pilots have already confused me.

 

Please talk to me as if I know nothing about "slip", lining up shots, etc.. I'm just trying to land properly at this point and trying to figure out the behavior of using rudder.

 

The primary function of the rudder is to keep the nose of the aircraft pointed in the direction you are going. There are a number of reasons why the aircraft will not do that by itself, but you really don't need to know all the theory of 'why' at this point (even if it will help, eventually).

 

In real life, it is easier as your pilot-aircraft interface* contains a sensor telling you if you are going sideways through the air. In real life and in the simulators, we have an instrument helping us. On the dash you have a turn rate indicator, a small white spade moving left and right, and below that a ball in a curved glass tube. If you are using the rudder right, that ball will be centered in the tube. If you are going sideways through the air, that ball will drift out to the upwind side.

 

To coordinate the aircraft, you simply need to 'step on the ball' - i e push the pedal on the side where you find the ball. With practise, you start anticipating the need for rudder and doing it automatically.

 

Power changes and aileron use are the big drivers of having to coordinate the aircraft through use of rudder.

 

Uncoordinated flight will mess up your shooting, reduce your speed, acceleration and climb rate and turn stalls into spin entries, so it is rather important.

 

Best regards,

/Fred

 

*) Also known as your 'butt' or your 'behind'. You feel what the aircraft is doing by the seat of your pants. :)

[Rusty_M]

This thread reminds me of a time a couple of years ago, when I had to use rudder to make it all the way back home in IL2 1946 (so somewhat less relevant I know) with no aileron controls.

 

That was not easy on a twist-stick!

[Cedaway]

....

*) Also known as your 'butt' or your 'behind'. You feel what the aircraft is doing by the seat of your pants. :)

 

Is that why we should 'center the ball?' :lol:

 

(I was thinking about a joke based on 'call the ball' but that's for another time...):pilotfly:

[cichlidfan]

Uncoordinated flight will mess up your shooting

 

Oddly enough, I just read something rather related to this point.

 

This a quote from the after action report filed by Lt. Bill Whisner, P-51 pilot, on 30 April 1944.

 

I began closing rapidly, so I centered my ball, and began firing from dead astern at 100 yards.

Edited May 10, 2012 by cichlidfan

[Pyroflash]

On a slightly related point, a useful maneuver (the slip), performed in reverse, becomes a skid (roll and yaw in the same direction), which is a maneuver that could potentially set you up for a deadly spin if the aircraft stalls. The reason that this is dangerous, is that a skid will give the perception of an increased turn radius at a decreased angle of bank, which some pilots (especially new, or student) will attempt to do to prevent going over arbitrary bank limits when turning during a pattern phase. The combination of a low airspeed and high angle of attack will surely set one up for a spin (which would be almost unrecoverable at that height, especially for new or student pilots as it is usually unexpected) when combined with an uncoordinated skidding turn.

[Harzach]

Oddly enough, I just read something rather related to this point.

 

I just finished reading Scarface 42 (memoir of a Marine helo pilot in Vietnam). The author mentions this several times in relation to setting up for rocket runs. One pilot he flew front seat for tended to fire his rockets during uncoordinated flight, endangering ground troops, prompting the author to learn how to do it correctly.

[jacksos101]

 

I must be used to too many arcade flight sims.

 

 

There is no such thing as an 'arcade flight sim' :no_sad:

 

It's either one or the other...

[SimFreak]

Another unconventional way is to use split throttle.