Vmc demonstrations in a twin.

[oldtimer]

I have been going through both the Metro 2 AFM and now the PA 31 AFM and there are comments about doing a Vmc demonstration during initial mult-engine training. My understanding from a jillion years ago this brought about problems with the PA 30 Twin Comanche. Apparently, in the USA, it was required that instructors actually demonstrate how directioal control is lost as the aircraft slows below Vmc with full power on one engine and one engine feathered or at zero thrust and how altitude affect Vmc due to the power loss at altitude. Also taught was how to regain conrtol. Apparently, with the PA 30, control was lost just as the airplane stalled and the airplane often spun into the ground with fatal results.
I have read about this procedure in the popular press and mention is made in the AFM's but have never seen it done in real life.
Does anyone in Canada ever do this with an ab-initio multi trainee or even during any recurrent training and do they still do this in the USA.
Seems to me to be a scary maneuver that is best discussed over coffee rather than in an airplane.
Your thoughts.

[trey kule]

First of all, IIRC, VMC numbers are done with the most rearward C of G . At less than gross, and a more forward Cof G you can easily get VMC and stall speeds to pretty much match and get in a whole heap of trouble.

Flight safety does the VMC demo in the SIM. The emphasis is on recovery. But the aircraft is configured properly. And if you screw up, only your ego is hurt.

Without the sim, I would go through the whole VMC issue with the student to ensure they understand it and the practical recovery. Before the speed gets that low. Would not even consider demo in a navajo series. Leave that for the "what could go wrong, I am invulnerable" crowd.

As an aside, a crew in SFO years ago were doing a three engine ferry flight, All three killed. From the CVR the only one who seemed to understand what was happening was the FE, though he offered no solution to the problem when it was happening.

[sidestick stirrer]

Is now optional during multi-engine training in Canada, the same with actually feathering a propellor in flight.

[Big Pistons Forever]

It is easy to safely demonstrate this manoever, you simply apply half of the available rudder. This ensure that the Vmc effects, that is the uncommanded roll/yaw occurs at a safe speed. The point of the exercise is not to prove the POH Vmc speed it is to get the student to recognize the symptoms of a incipient Vmc loss of control and to take effective recovery action. It is IMO an essential part of the initial twin rating.

BTW at the risk of being pedantic it is Vmc not VMC

[sidestick stirrer]

What a great idea, may I steal it?

[Big Pistons Forever]

What a great idea, may I steal it?

Since you did not pay anything for it, it is not stealing

[sidestick stirrer]

Thanks!
And to continue with being pedantic, it was not until I "retired" into an FTU that I came across that acronym Vmc.
Heard Vmcg and Vmca for decades, never Vmc...

[Big Pistons Forever]

Thanks!
And to continue with being pedantic, it was not until I "retired" into an FTU that I came across that acronym Vmc.
Heard Vmcg and Vmca for decades, never Vmc...

The FAR Part 23 aircraft mentioned by the OP are not required to demonstrate a Vmcg, and the rules for Vmc are different and less onerous than those used to determine the Vmca of a Part 25 aircraft. So in furtherance of pointless pedantry, Vmc is in fact the correct term for the in flight minimum control speed on one engine for Part 23 aircraft.

[sidestick stirrer]

Hardly pointless, Sir: I am still learning.

[oldtimer]

Swearingen/Fairchild do not consider actually shutting an engine down for training to be a wise move. They strongly advocate setting zero thrust instead.
I was in Walla Walla a few years ago and an air operator from Missoula was complaining that certain FAA types required a complete engine shut down on a Cessna 421 during recurrent training IN THE WINTER. It was near on to impossible to get the engine restarted. The Australian equivelant to the TSB says to not chop the power levers of a King Air. 1900 or Metro 3 to idle power to simulate an engine failure. They claim is not repersentative of an actual engine failure with either NTS or Autofeather. This came after a couple of fatalities during training. Zero thrust accomplishes what is required for the training.
I can see where a Vmc demo may be required but a demo at altitude with a safety margin is the way to go.
Which brings me to my favorite subject, A proper groundschool training program before getting into the airplane. The airplane is not that good a teaching tool. It should be used to put into practice what is learned on the ground.

[Big Pistons Forever]

Oldtimer: You make a very good point. I carry out all training using the throttle to set zero thrust. Thank god TC finally got rid of the stupid requirement to actually shut down and feather an engine as part of the initial multi engine rating.

[PilotDAR]

I was trained, decades ago, in a 310, and included shutting down and feathering, and one engine at zero thrust overshoots. I can see the point of those who say both of these are higher risk than benefit, so I'm not saying that these should be included in present day training.

However, when I am required to test a modified aircraft, I am required to re-demonstrate Vmc. I'm allowed to do it at altitude, with a factor added to the speed for the affect upon the power if it is normally aspirated. I assure that everything else is in my favour during this flying. Generally, I can find a zero thrust value to use, which is acceptable for demonstrating compliance. Occasionally shutting one down is the agreed technique. PT-6's are easy, just feather it while it's at idle.

I have never had an unpleasant surprise doing this, indeed, I have been pleasantly surprised a few times at how docile the plane is, and a Navajo was an example of this for me. I'd heard terrible things about the Navajo, and was delighted at how nicely it flew on one engine.

My experience has been that the loss of control slowing past Vmc was not a sudden roll over on your back and spin, but the beginning of an uncontrollable turn. Okay, you go with it, collect the data, and gently recover. This is certainly not a phase of flight for jerky or excess control inputs, gentle handling is vital. I have found that each type I have tested in this realm gave me lots of warning as to what it was going to do, as long as I payed attention. And, recovery was no problem, as long as I was willing to surrender some altitude.

I have found that aircraft whose Vmc is close to stall speed are about as safe as you can get. If you're on one engine, and you allow the plane to stall too, you really are asking for trouble aren't you? If you don't allow it to stall, you can maintain control too. Perfect!

I think the much bigger risk is pilots who think that they can climb away on one - high expectations! It is the distraction of trying to climb away on one, and failing to maintain flying speed, then loosing control, which is causing accidents, not simply gentle planned flying at Vmc. I recommend this article to bring a dose of reality to that thinking:

http://www.iflypete.com/documents/Always_Leave.html

[sidestick stirrer]

A dose of reality, indeed!
Thanks for the great link.

[digits_]

In Europe it is mandatory to perform an engine shutdown in a twin, and a demonstration of Vmc. I must say it was a real eye opener for me. Of course you study it in theory, but to experience it "for real" really built my trust in the theory.

[Colonel Sanders]

a demonstration of Vmc

Did you do it at a really high altitude, for safety?

[digits_]

a demonstration of Vmc

Did you do it at a really high altitude, for safety?

About 5000 ft AGL. We lost about 300 ft during the demo.

[triplese7en]

Excellent post, PilotDAR!

[pelmet]

As an aside, a crew in SFO years ago were doing a three engine ferry flight, All three killed. From the CVR the only one who seemed to understand what was happening was the FE, though he offered no solution to the problem when it was happening.

Not familiar with that one. What type and airline. I only know of one and it was at Kansas City.

http://aviation-safety.net/database/rec ... 19950216-0

[Colonel Sanders]

Did you do it at a really high altitude, for safety?

No one got my funny

[costermonger]

It is easy to safely demonstrate this manoever, you simply apply half of the available rudder. This ensure that the Vmc effects, that is the uncommanded roll/yaw occurs at a safe speed. The point of the exercise is not to prove the POH Vmc speed it is to get the student to recognize the symptoms of a incipient Vmc loss of control and to take effective recovery action. It is IMO an essential part of the initial twin rating.

This. There's no need to prove the POH speed if they understand how the published number is arrived at anyway, since they should also understand how the various factors affect the 'real' speed in a given situation.

Did you do it at a really high altitude, for safety?

No one got my funny

I did. Years ago a self-described old-timer I used to bump into now and then told me a story about how when he was teaching at a school in Florida in the early 80s, one instructor liked to go up real high and do a 'real' Vmc demo, which almost always led to a spin (Vmc at sea level in one of those things is Vso+1 - it's going to stall first. Always.). He implied (though I didn't press for details) that this caught up with the instructor eventually.