Originally Posted by
megan
Not a multi FW rated guy, but any single engine work means keeping Vmca uppermost in mind. Manuals I've read suggest 5,000 as the minimum altitude for Vmca demonstration.
Megan, the trouble with Vmc demontrations is that they are usually a demonstration of a speed which is anything but Vmc.
As you will know, Vmc is a speed precisely defined by the aircraft certification requirements, and determined during certification flight testing.
Some of the thing you need to know during this determination are engine power, rudder force, rudder angle, actual weight and cg, sideslip angle, bank angle, heading. Depending on the aircraft, aileron force and aileron (spoiler) angle may also be handy. A continuous time history of bank angle and heading will be required for determining exactly when Vmc occurs.
A very conservative test plan is developed and flown for this determination.
If, as an instructor, you plan to demonstrate "Vmc ", as well as loading the aircraft correctly you will need to obtain the manufacturers Vmc bank angle and information on which is the limiting case ie static Vmc or dynamic Vmc. Even then, flying at "Vmc" is no guarantee of controllability if the wrong bank angle, rudder force, rudder angle is used.
If you are demonstrating a loss of control speed, be very careful that the (possibly) reduced maximum power at the demonstration altitude doesn't lead to low speeds, never experienced during the certification testing, which could reduce controllability.
Real Vmc determination or demonstration is a hazardous area of flight, some sort of departure from controlled flight should be expected at some stage, a very clear recovery procedure developed and practised at safe altitudes and speeds.
I don't know if instructors and flight examiners continue to practise being test pilots, even if unwittingly.