standards limit the bank angle to "no greater than 5 degrees", the optimum is around 3 degrees
4Dogs, JTs comments are correct on this.
You are infact talking about two completely different things.
One is an attempt to minimise Vmca.
The other is where the aircraft performance (ie rate of climb) is best.
They are two separate objectives. Vmca will, in nearly all aircraft, continue to DECREASE a little more as bank increases above 5 degrees towards 8-10 degrees. As JT said, this is not practical, so certification places a restriction on the manufacturers that Vmca can not be at more than 5 degrees angle of bank.
It is also important as people have said, that during certification, speed is slowly and in a very controlled manner reduced back onto Vmca. The current type I fly at a minimum speed takeoff, requires aggressive and sudden application of full rudder and 60-70% aileron during rotation. Once at the required pitch attitude, these can be reduced very slightly. This is in complete contrast to a nice, slow and controlled walk back into Vmca.
Vmca could be considered somewhat of an irrelevant speed in flight operations (important conceptually, of course). When was the last time you had a V1 cut, and rotated the aircraft into the air with 5 degrees angle of bank?
All this discussion about min speeds is all well and good, but not particularly relevant. The main causes IMHO were:
1. Should have been in a sim
2. Autofeather failure with a V1 cut is a ridiculous scenario to train for. How many times has this actually happened vs. how many people have been killed training for it? ABSOLUTE waste of time.
3. The checkie made some fundamental errors when it turned to
.
a) He should have been trained by CASA to have a strict set of criteria (a maximum heading change, speed change, controllability change) upon which he terminated the exercise immediately by no method other than advancing the power lever of the failed engine.
b) He should have been trainined by CASA that in the event of pushing the "failed" power lever forward, if things were still not improving, that the live engine should have been pulled back to ensure directional control, even if this required a temporary loss of altitude.
Both crew most probably could have given quite a good rundown in the briefing room on what Vmca is, under what conditions it is certified, and what that speed was for their aircraft.
But that knowledge meant nothing when the exercise was not immediately terminated when it went pear shaped, and when the power on the live engine was INCREASED, not reduced.
Anyone CASA approves to complete ME aircraft training needs to be extensively trained and examined on the following before being let loose:
1. Be absolutely confident in their head which engine they are going to pull and what actions will be required
2. Guard the "wrong" rudder just prior to the failure to provide protection against incorrect rudder application
3. Have a STRICT set of SMALL tolerances, beyond which they commit themsleves to IMMEDIATE termination of the exercise
4. Where exercise termination is required, do this by immediately advancing the "failed" engine
5. Where this does not resolve the issue immediately, reduce the live engine power to ensure directional control (sometimes at the expense of altitude)
6. Immediately takeover control of the aircraft.
Another two (from all reports) nice guys of aviation who have paid the ultimate price because of archaic, 1960s training ideologies & methods.