Why is Yaw 2nd effect of Roll? (and explain Trim)

[apollo85]

ummm yeah!!! realise that..
if you read the orginal thread the guy is asking why we dont! trim while airspeed is changing!

try to read between the lines a bit....

: "AS SPEED CHANGES WE NEED A CHANGE IN ATTITUDE >> WE NEED TO RE TRIM."

that is >>> re-trim (once you have set desired attitude as a result of airspeed change).... not trim why our attitude changes!

[ghostwhowoks]

Your original post:

THE REASON WE TRIM IS TO NOT ONLY RELIEVE LOADS ON THE CONTROL COLUMN BUT TO SET THE REQUIRED AOA(I.E WE SEE ATTITUDE) WE NEED.

Trim is not to set either AOA nor attitude (which are not the same). The reason we trim is to relieve loads on the control column. That was my point.

Except of course if you lose all your flight controls and all you have left is trim and engine power! Have a look at this incident http://www.strategypage.com/respect/...y_20041031.asp. These guys know why secondary effects of controls are importance!

Cheers

Edit: added link to incident report.

[apollo85]

think about why u want to fly "hand off"....!?!?!?!?!??!?!

yes the effect it has in the cockpit is to relieve the pressure on the control column.... but this is because it makes it easier for us to maintain the desired attitude!!!

we set our pitch attitude through the elevator - - - - therefore if we balance the lift and drag through this control surface (with the trim tab) we will maintain our desired ATTITUDE by maintain our desired ANGLE OF ATTACK!!!

..... (it isnt just so you can have nice floppy wrist and fly without getting a wrist ache!!!!)

[apollo85]

Ghostwhoworks

MAYBE ITS TIME TO GET THE NOGGIN BACK INTO THE OLD BASIC AEROKNAUTICAL KNOWLEDGE CHAMP!!!

THEY ARE ALL RELATED>>BE IT THEY ARENT THE SAME

YOU MOVE YOUR ELEVATOR>> YOU CHANGE YOUR ATTITUDE>> YOUR WINGS WILL HAVE A DIFFERENT ANGLE OF ATTACK!!!>

[ghostwhowoks]

You say "therefore if we balance the lift and drag through this control surface"
Please enlighten me how we balance lift and drag?

Why is attitude not the same as AOA? Well if you select a higher attitude and increase power to maintain airspeed is your AOA more or less?

BTW, do you have a problem with your caps lock key?

[bothok_teri]

simple answer

1. If the air craft is banking, your rudder will produce lift, so your plane will yaw
2. flight principles, just demonstrate to your student when straight and level flight add power so in a moment the speed will increase and your plane will climb, after that your speed will decrease same as straight and level.... thats called trimmed speed,

[ghostwhowoks]

bothok_teri wrote:
1. If the air craft is banking, your rudder will produce lift, so your plane will yaw

Rudder will only produce lift if either a rudder input from neutral is made or the aircraft is sideslipping.

roll->bank->sideslip or rudder->yaw

[bookworm]

In a conventional design (dihedral and/or sweep back for roll stability) in a steady turn (constant rate of roll, pitch and yaw), there is a requirement to hold some into turn aeileron to maintain the AOB. This causes a (slight) adverse yaw, requiring into turn rudder to remain balanced.

In a balanced turn, the rolling tendency is into-turn, not out-of-turn. Hence out-of-turn aileron would be required. The need for rudder in a steady balanced turn comes from the desire to eliminate the sideslip (which you have correctly identified as contributing to the into-turn yaw).

If the turn is not properly balanced and the sideslip is allowed to persist, the slip-roll coupling (dihedral, sweepback or fuselage position effects) will indeed cause an out-of-turn roll. But in most conventional aircraft it won't exceed the into-turn rolling tendency, otherwise the spiral mode would be stable.

[jamestkirk]

WHAT!

Someone please close this thread before we need therapy, a hug, the samaritans or a painless way to take our own lives.

Or all the above in any order

[bookworm]

Originally Posted by jamestkirk

Someone please close this thread before we need therapy, a hug, the samaritans or a painless way to take our own lives.

One to beam up Scotty, easy on the yaw...

[ghostwhowoks]

the rolling tendency is into-turn, not out-of-turn. Hence into-turn aileron would be required

Isn't that bar$e ackwards?

But you are correct, the sideslip is eliminated by rudder in the balanced turn. After blowing some cobwebs off I remembered it is the increased AOA on the down going wing (constant roll rate) that causes the out of turn roll, and therefore requires into turn aileron.

To those voting closure, you don't have to keep coming back to read it, you know. Some of us weird types find aerody interesting. Trying to explain it makes you remember the bits you forgot (if that makes sense).

[jamestkirk]

for the love of god

Khaaaaaaaaan! Khaaaaaaaan!

[bookworm]

Isn't that bar$e ackwards?

.

Yes :blush: I've corrected it above. I simply didn't write what I was thinking and stand by my point.

After blowing some cobwebs off I remembered it is the increased AOA on the down going wing (constant roll rate) that causes the out of turn roll, and therefore requires into turn aileron.

If the aircraft were rolling, yes, that's roll damping. But in a level balanced turn it is not rolling.

[casccadeair]

cascadeair

When the yoke is moved to roll the a/c, the downward moving aileron generates more lift, and consequentlhy more drag. The upward moveing aileron generates less drag, because producing lift produces drag, and vice-versa. Thus as the a/c rolls, the ascending wing lags behind the axis and yaws the aircraft. Very Simple.

[BEagle]

A plausible description of adverse aileron yaw, but nothing whatsoever to do with the further effect of roll.....

ROLL>>SIDESLIP>>YAW

Is teaching and learning of such utterly basic aerodynamics really so pi$$ poor in today's so-called training world?

[BillieBob]

If the secondary effect of aileron was yaw in the same direction as the intended roll, when you roll wings level, the aircraft should yaw to the left. It wont though

Oh, yes it will! If, from a level balanced 30° AOB turn to the right, left aileron is applied (to roll the aircraft towards wings level) without any movement of the rudder, the aircraft will also yaw to the left as a consequence of the applied aileron.