This is something that confused me during my brush up at BGS. I had been taught in the states that an increase of weight, decreases the Vmc. During the brush up, I had a feedback question that asked this question and the correct answer given was that Vmc is uneffected by weight. I asked one of the BGS instructors to clarify this.
From what I was told, the JAA does not teach the idea that Vmc decreases because it could lead to a false sense of security. For example, Joe Bloggs loads up of his Seneca to max take off weight thinking that his Vmc will be lower. Only to find when an engine quits, his single engine perfomance is !!!!e and doesn't climb.
From the FAA Multi-Engine oral guide by ASA............
Why does a change in weight affect Vmc?
Vmc is unaffected by weight in straight and level flight. Vmc will be affected by the aircraft's weight in turning (banked) flight. When an aircraft is banked, a component of of the aircraft's weight acts along with the horizontal component of lift to create a more effective slideslip towards the operative engine. For a given bank angle, the greater the aircraft's weight, the lower the aircraft's Vmc.
From what I can see, we are told to bank into the operative engine after an engine failure. If the aircraft is banked, then Vmc will change with an increase of weight. I'm far from an expert in the field and only passing on what I've been told by others.
