So on my Multi-engine Commercial ride, I was asked what happens to Vmc with bank angle? Assume I was in an airplane with counter-rotating propellers. So there is no critical engine
I told him I wasn't sure, but if I were to guess, Vmc would increase with an increase in bank angle. This would be primarily due to load factor, and the aspect that as load factor increases, lift must also increase, increasing induced drag, and from my understanding, every form of drag will increase Vmc.
Does anybody know the answer to this question? I saw that it IS in the AMEL PTS, and I am getting ready for my MEI ride and this is the last thing that is giving me trouble.
Thanks!
Long story, involving some history. The FAA used to publish the Flight Training Handbook (now published as the Airplane Flying Handbook). Prior to the 1980 printing, when discussing Vmc one of the factors affecting loss of directional control was listed as "bank angle
no more than 5 degrees (my emphasis). In the early 1970's, when the original GI Bill was going hot and heavy, multiengine students and instructors were dying at an alarming rate and magazine articles critical of multiengine training and testing were coming out every month. In April, 1976, an FAA test pilot/engineer named Les Berven wrote an internal staff study titled "Engine-out Characteristics of Multiengine Aircraft." In it, he cited flight and simulator testing that he had performed using the current testing standards and presented damning evidence that it was the training and testing standards that were at fault.
When I was training for my MEL in 1968 I was taught to do the Vmc demo with the wings level and the ball in the center; Berven proved that under those conditions actual loss of directional control occurred as much as 15 knots faster than red line airspeed. We did other scary things, like slowing below red line and then killing an engine. Recover before the bank reached 45 degrees and you got brownie points.
In his staff study, he said that training emphasis should be placed on the importance of banking
at least 5 degrees (my emphasis again). He also stated that engine-out flight with the ball centered is never a correct configuration and, in fact, will degrade performance and result in unsafe stall characteristics.
In the 1980 printing of the FTH the words "not more than" were replaced with "at least," and in a different font...just in case anyone thought that it was an editing error.
FAR 23.149, which tells manufacturers, not pilots, how to establish Vmc, still says "not more than..." but that is to keep unscrupulous salespeople from demonstrating an artificially low Vmc by banking more than five degrees. So for pilots, bank as much as you want: increased bank angle does reduce Vmc. It reduces lift, too, which you will realize about the time your bank angle gets past ten degrees.
When I was writing THE COMPLETE MULTIENGINE PILOT, Les Berven worked at the Northwest Mountain Regional Office and made himself available to explain all kinds of arcane concepts in crystal clear language. He died far too young.
Bob Gardner
She also taught me a lot about flying a Travelair since she had a couple thousand hours instructing in them.
