Factors affecting Vmca

[john_tullamarine]

LRT,

I suggest that the effect of systems operations (gear, flaps, etc) will vary from one aircraft to another. Unless someone bothers to do the tests and determine the actual Vmca for any given set of conditions, then you are unlikely to end up with much in the way of illumination. I would be far more interested in seeing pilots worry about bank control at low speeds .... let the bank angle go the "wrong" way .. and you might get a very salutory surprise ..

Vmca, as published, certainly is conservative for most operations although I wouldn't talk in terms of "absolute worst case scenarios". Like most things in aerodynamics, there are many exceptions to consider when talking about rules ....

One needs to be a little careful in extrapolating from the typical endorsement "static Vmca" demonstration exercise. It has not a great deal to do with the published Vmca figure, is of very little practical training value and may well be counterproductive. If performed at altitude it sets the pilot up for a possible stall and spin departure situation .... not a nice set of circumstances.

Could I ask you to give some explanation on circumstances where the static Vmca demo is likely to give a problem ABOVE the AFM figure ? If the configuration is as published, I would have been surprised to see a problem presenting at a higher speed ... provided that bank is controlled appropriately ?

Then again, if I may relate the tale of a colleague some years ago ..... Being mindful of the problems and hazards, and when faced with having to do an unwanted endorsement to effect an instrument rating renewal, eventually, when asked by the instructor to do such a demo, he held on a restricted rudder displacement. The instructor, apparently, was mightily confused by the resulting higher than usual speed at which heading control was lost. My colleague, on the other hand, was much more relaxed than he would have been had he been silly enough to play with full rudder during the exercise.

The published Vmca is, most definitely, a hard and fast figure for the conditions specified and a fair bit of flight test effort goes into making the determination. The real world day to day figure, for any given set of circumstances, will, of course, vary from the book figure.

Perhaps I misread your earlier post .. I was only enquiring if you were suggesting that there was some relationship between Vmca and Vyse ?

Tempo's question includes its answer .. there exists conflicting tales because there is no definitive story to tell. As DJP (a very experienced aerodynamicist and light aircraft pilot) in another thread elsewhere some time ago said, in paraphrase, ... "tell me the observation and I can give you an explanation ... but don't ask me to work it the other way around".

I shall be interested in seeing where this thread may lead ....