John Tullamarine and my faithful intriguing respondents.
Should have set up the ground rules up front to avoid the confusion which has been flowing back and forth. Perhaps they should preferrably be called air rules.
Thank you JT for your intervention. Yes I had my time as a QFI and RAAF CFS staffer plus other things.
Firstly what are we ON about. It's Asymmetric Handling and an examination of the forces acting..
The overriding fact to be determined initially is whether an aircraft having any angle of bank and in steady straight balanced flight can achieve that condition without sideslip. This is the area causing the greatest confusion. Please can anyone nominate a circumstance now or forever hold your peace.
That should be a very simple determination, should be instinctive to a pilot and remain an uncomplicated fact provided my definitions agree with yours.
So herewith the definitions I am using and listed in response to JT's (a) to (c)..
These definitions are off the top of the head and almost from the heart. They should be consistent with text books.
(a) Balanced Flight. Any condition of flight when there is a continuing state with all forces acting on the aircraft in equilibrium.
Slip = Sideslip.
(b) My 'aerodynamic slip vector' (don't like the term) is that force normal to the line of flight generated by sideslip acting through the lateral centre of pressure.
Explanations. 1. Force Generated by Sideslip. The difference in the lateral aerodynamic forces resulting from differing airflows on each side of the fuselage.
2. Lateral centre of pressure. Similar to wing lift centre of pressure but instead the point through which horizontal side forces act.
No force without sideslip. Rudder force not considered seperately as it is included in total side force.
(c) Why would I bank to zero rudder? I wouldn't except when IAS is close to Vmca. In some cases there may be a trade off between the total drag wings level and banked.
Explanation. 1. Rudder central may be more efficient with rear fuselage only generating the sideforce.
2. Zero rudder allows for decreased Vmca.
(d) (e) Later coverage. Will only overly complicate at this time and further complicated by published Vmca having included a 2 second delay before taking recovery action.
(f) No definition here and we are splitting hairs which are all having a strong tendency to stand out straight! Simplest explanation I can offer is :-
Roll on bank to produce the horizontal sideforce. Immediately we have departed balanced flight. Initially the unbalanced sideforce is now overcoming aircraft inertia and slowly accelerating the aircraft sideways in the direction of the sideforce until the build up of the force due to sideslip balances that lift sideforce. Now we are back in balanced flight/equilibrium, having established a yawing couple by the two sideforces which balances out the opposing yawing couple by the offset thrust and the total drag. The resolved lift sideforce act through the total lift centre of pressure (almost coincident with the cg) and the sideslip force acts through the lateral centre of pressure which will have moved further aft as the sideslip angle increases. Incidently if the lateral centre of pressure moved forward of the total lift centre of pressure the aircraft would have a strong desire to turn around to go backwards.
Damn it I didn't want it to get that complicated again so soon but I don't know how to avoid it.
Are you having problems with the concept of a lateral centre of pressure? It doesn't generally get too much of a mention. Has more significance with boats than aircraft EXCEPT for our present subject and for those wanting to do 4 point slow rolls at low altitude !
Tear me to bits if you can or have I recruited a few disciples?.