John Tullamarine
Our worthy moderator has raised 6 points for clarification concerning the complexities of asymmetric handling.
Rather than repeat them item by item which would make this a lengthy rendition I ask participants and other parties of interest to refer back to JT's post hoping that it is not now on a separate page. Damn just saw that it is on the previous page.
Item 1.
In seeking a comprehensive definition of sideslip the term "normal to the vertical axis" was included only for completeness knowing full well that the sharp minds viewing the post would likely be critical of a definition which only related to our strictly horizontal determinations. We well may have to defer to our aerodynamics potentate whoever that may be for the absolute precise definition. Let us agree for now on the simple version applicable to the horizontal.
Item 2.
Don't think that quote was mine but I recall I did respond to it. To have "skidding zero rudder deflection" we must necessarily have bank to cause the skid. The skid is creating the force to stop yaw. Use of rudder to reduce the skid changes the force and immediately puts us back into unbalance. There is NO way to go with rudder and stay in balance unless we readjust the bank angle.
Item 3.
Answered by Item 2 above I believe and I think you have answered your own question correctly. We do play with the bank angle to readjust our rudder position. For any bank angle there will be a precise rudder position for balance. You cannot change one without changing the other as you have said in Item 4..
Item 4.
Airflow directions? That's a curly one and I think too complex for a definitive statement. Instinct from experience tells me that the variations to sideslip as we vary our relationship between bank and rudder will be so infinitesimal that we can confidently say there will be insignificant change in the small range of bank angles of any worthwhile use. Somewhere in there may well be the minimum drag combination we want but then the flatness of the drag curve here may mean that it is of no consequence. We are now into the realms of instrumented flight test or wind tunnels. Would be great to hear from someone who has been there.
Item 5.
The statement is applicable to any condition of balanced flight. Of course we often change the drag vector but usually take care to balance one side of an aircraft with the other. If we install a drag producing device on one side only we have a total drag line offset from the fore and aft axis. We have then created an inability for that aircraft to be able to fly balanced directly in line with its fore and aft axis. If the delta drag is small then the sideslip to compensate will be minuscule and indiscernible to a pilot but it will be there nevertheless. Where it is very discernable though is when we have an engine out causing a large drag line offset.
Item 6.
Why is it that one cannot input rudder to achieve the force desired? John that is precisely what we do. The force desired is that which makes up the total from the tail to offset the yaw. It is a precise amount to achieve balance. Move the rudder that nat's whisker (or should it be gnat's?) either way and you go into unbalance. And yes the same with elevators and ailerons. For any balanced condition there will be a precise position/angle for both. We try to trim to those positions.
What now ? Strong coffee maybe !
Ohhhhhhhhhh now I have a whole new set of items from JT amongst others all waiting with baited breath !
Watch this space.
Keith.Williams
We have been consistently trying to handle an asymmetric twin with its left engine shut down whilst being flow by a succession of terribly mixed up pilots .
In your last post you say " we are talking about a situation in which the aircraft is sideslipping to the left. YES or NO?"
A huge NO NO NO Keith. We are sideslipping to the RIGHT to generate that sideforce to oppose the yaw to the LEFT. They balance out don't you see?
Then "And isn't this sideslip to the right? YES or NO?"
YES by banking into the live right engine.
Now , having recognised your incorrect perceptions above, you will clearly see that there is no way we can get to a condition of zero sideslip.
You must now be my first disciple.! or do I have to prepare more sermons.?
Have you ever flown asymmetric?
SR 71
Cannot see the path of your proposed logic SR 71.
You have blinded me with science to the extent that I am unable to achieve a decode.
Put it in the simple terms directed at the asymmetric twin which is fast running out of fuel!!
Last edited by Milt; 21st Sep 2004 at 02:43.