Vmc roll - recoverable?

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Joelsweet

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Joel
I have recently learned/spoken with some folks about Vmc rolls, specifically in Seminoles/PA-44s....

The synopsis I have gotten is this:

It is impossible to recover, regardless of how many thousands of feet AGL one is, without the plane falling apart.

The question is this:

Is that true? I don't like to think in absolutes.... I feel that it may be possible. I don't plan on testing my hypothesis. Let me know what you think / have found on this topic. I couldn't come up with much.
 
Of course it is recoverable. The airplane is slow during a VMC roll, so the aerodynamic forces are not enough to destroy the airframe. The solution is to pull back the power on the good engine, then recover from the spin.
 
kyleb said:
Of course it is recoverable. The airplane is slow during a VMC roll, so the aerodynamic forces are not enough to destroy the airframe. The solution is to pull back the power on the good engine, then recover from the spin.
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:yes::yes::yes:..

All it takes is enough altitude.....:rolleyes:
 
The Vmc roll itself can be recovered from if done at a high enough altitude. This is part of the reason why you're supposed to practice Vmc demos several thousand feet off the ground, just like stalls.

If you're in a normal location where a Vmc roll occurs (which is low altitude on approach or departure), then it's not recoverable. Your best bet is you recognize it as it's starting, pull the good engine back, and recover.

Best of all is just not to get to that corner of the envelope in the first place.
 
obviously this is an academic exercise. A seminole will stall before it will run out of rudder.
 
The Seminole is usually pretty docile with the 180 hp engines,.if recognized with some altitude it should be recoverable.
 
It is impossible to recover, regardless of how many thousands of feet AGL one is, without the plane falling apart.
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Hyperbole designed to (perhaps wisely) instill a healthy respect of the maneuver?
 
more BS by single engine pilots...of course its recoverable w altitude, just like stalls.
 
On most of our general aviation twins a VMC roll is because of asymmetrical thrust and a lack of rudder authority at a slow speed. Usually because of the direction the props turn on most twins, the left engine is the critical engine. Meaning if you lose the left at low altitude and a slow speed, like just after TO, you can get yourself into a VMC situation. This speed is marked as a red line on the ASI.

In training when you recognize the start of the VMC roll, you pull the power back on the good engine and recover similar as you would to a stall. If your unconscious and you let it develop in to a full VMC roll, it will go over on it's back, done at low altitude it's usually fatal.

I believe I was told years ago that the Seminole will not do a real VMC demo as it will stall first, but I've never flown one. I did all my initial ME training in Aztecs.

The people you talked to are either pulling your leg, or they're full of BS and know absolutely nothing.
 
Tx_Flyboy said:
more BS by single engine pilots...of course its recoverable w altitude, just like stalls.
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As a twin pilot, this is my thought: I suppose it depends on your definition of 'VMC roll'. In other words, how far you let it go.

VMC demonstrations done during multi-engine training and checkrides are not VMC rolls. You stop the maneuver and recover before the roll actually develops. An actual VMC roll is more like a spin than a stall. Yes, stalls are recoverable, not all aircraft can recover from a spin however, regardless of altitude.

For the vast majority of twins, no one really knows if a true VMC roll is recoverable because it is never tested. There are a few airplanes who have recovered from actual VMC rolls, but those are few and far between.

I can say this - there has been at least one B-25 that recovered from a VMC roll. It happened near Douglas, AZ where my grandfather was training. It took over 10,000 feet to do it and IIRC, the airplane was not usable again.

Keep the blue side up my friends!
 
champ driver said:
I believe I was told years ago that the Seminole will not do a real VMC demo as it will stall first, but I've never flown one.
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Most light twins used for training (Seminole, Duchess Twin Comanche, even my NA Baron) will not actually VMC roll at the altitudes we train at these days. Unless you are flying turbos, the engine won't develop sufficient power to overcome the rudder and you will stall first - which is why most MEIs have to 'block' the rudder to make the demo possible.
 
Fearless Tower said:
Looks more to me like he starts making an intentional turn to the left and then gets too slow.
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The Vmc on a Queen Air is 95 mph. Stall speed (clean) is 83 mph. It looks like a textbook example of a Vmc roll to me. When we do Vmc demos during training it's carefully choreographed - blocked rudders, slow entry, recovering immediately at the first indication of a yaw. And rightfully so.
 
Dead Stick said:
The Vmc on a Queen Air is 95 mph.
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Remember what the definition of VMC is. 95 MPH is the published VMC at full power on the operating engine. He is nowhere near full power on the good engine in that video. Actual VMC would be considerably less and while the stall speed will remain unchanged.

That is the same reason we aren't able to achieve actual VMC in non-turbo trainer twins when the demo is done at altitude (the stall happens before VMC).
 
Fearless Tower said:
Remember what the definition of VMC is. 95 MPH is the published VMC at full power on the operating engine. He is nowhere near full power on the good engine in that video. Actual VMC would be considerably less and while the stall speed will remain unchanged.

That is the same reason we aren't able to achieve actual VMC in non-turbo trainer twins when the demo is done at altitude (the stall happens before VMC).
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We'll never know what his power setting was and we don't know what his weight was. I've never flown a Queen Air (and King Airs don't count) but I have had an actual engine failure immediately after takeoff in a Cessna 411 which is a pretty comparable airplane. It took nearly full power on the remaining engine just to maintain altitude with the one caged. Due to the audio quality, it's impossible to say what the power was on the his good engine. We may have to agree to disagree, but it's obvious that he let it get too slow and ended up spinning it in.
 
Dead Stick said:
We'll never know what his power setting was and we don't know what his weight was. I've never flown a Queen Air (and King Airs don't count) but I have had an actual engine failure immediately after takeoff in a Cessna 411 which is a pretty comparable airplane. It took nearly full power on the remaining engine just to maintain altitude with the one caged. Due to the audio quality, it's impossible to say what the power was on the his good engine. We may have to agree to disagree, but it's obvious that he let it get too slow and ended up spinning it in.
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Don't take this personally - I'm not picking on you. I just feel that we as a community do a terrible disservice to multi engine students in the way we talk about and train for VMC demos.

In a VMC accident, the good engine at full power will overcome any control inputs the pilot may make. This causes the wing of the good engine to lift/climb and the airplane literally rolls over onto its back. Contrast that with an uncoordinated stall where one wing stalls before the other and drops. That is what I believe you are seeing in that video. The left wing dropping vice the right wing climbing over the top. It may sound like semantics - The end result in a twin is usually the same - fatal. But the recovery is a little different. Which is why I think it is important to differentiate.

VMC demos that we train for and perform on check rides are really not representative of what actually happens in a VMC accident. Many MEIs train students to wait for the loss of directional control and then the student responds with pulling the power back and lowering the nose to regain blue line.

That sounds great.....but it won't work in a real life VMC accident. You will not have that time. You have to be disciplined to pull the power and set it back down as soon as you have any loss of power. The good news is that in the majority of GA twins, your actual exposure to the VMC danger zone is really quite small (a few seconds at most if you fly a conservative departure profile). A VMC accident if it happens, is going to occur while still over the runway between 0 and about 25' AGL. You can't wait for the loss of directional control - it will happen too fast. It won't be anything like a VMC demo.

You are far more likely to lose control and die if you get too slow with one caged - but unlike SEL stall recoveries, you can't let it go all the way to the stall with asymetric thrust and expect to be able to recover - you have to initiate the recovery at the first indication of pending stall (buffet or ideally stall horn). Which IS what we are supposed to do per the PTS for the VMC Demo. My beef is that we should be treating it as a stall avoidance-recovery maneuver and not trying to pretend it is simulating loss of VMC by either name or blocking the rudder.

Anyway, back to your regular programming.
 
Fearless Tower said:
Don't take this personally - I'm not picking on you. I just feel that we as a community do a terrible disservice to multi engine students in the way we talk about and train for VMC demos.

In a VMC accident, the good engine at full power will overcome any control inputs the pilot may make. This causes the wing of the good engine to lift/climb and the airplane literally rolls over onto its back. Contrast that with an uncoordinated stall where one wing stalls before the other and drops. That is what I believe you are seeing in that video. The left wing dropping vice the right wing climbing over the top. It may sound like semantics - The end result in a twin is usually the same - fatal. But the recovery is a little different. Which is why I think it is important to differentiate.

VMC demos that we train for and perform on check rides are really not representative of what actually happens in a VMC accident. Many MEIs train students to wait for the loss of directional control and then the student responds with pulling the power back and lowering the nose to regain blue line.

That sounds great.....but it won't work in a real life VMC accident. You will not have that time. You have to be disciplined to pull the power and set it back down as soon as you have any loss of power. The good news is that in the majority of GA twins, your actual exposure to the VMC danger zone is really quite small (a few seconds at most if you fly a conservative departure profile). A VMC accident if it happens, is going to occur while still over the runway between 0 and about 25' AGL. You can't wait for the loss of directional control - it will happen too fast. It won't be anything like a VMC demo.

You are far more likely to lose control and die if you get too slow with one caged - but unlike SEL stall recoveries, you can't let it go all the way to the stall with asymetric thrust and expect to be able to recover - you have to initiate the recovery at the first indication of pending stall (buffet or ideally stall horn). Which IS what we are supposed to do per the PTS for the VMC Demo. My beef is that we should be treating it as a stall avoidance-recovery maneuver and not trying to pretend it is simulating loss of VMC by either name or blocking the rudder.

Anyway, back to your regular programming.
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I'm not taking it personally and I agree with what you said up to a point. For the record, I am a current ATP/CFII/MEI and I've given several hundred hours of dual in multis including most of the popular light piston twins, MU-2s, Lears, G100s, G200s, Falcon 50s and 900s. Unfortunately, not all multiengine aircraft have Vmca close to or less than their stall speeds. Some popular multiengine aircraft have significant spreads between the two speeds - Vmca being significantly higher than the stall speed. (That's what killed a bunch of MU-2 pilots over the years before they got a handle on pilot training.) You need to initiate recovery at what ever happens first - the first indication of loss of directional control or at the first indication of a stall.

Most guys get their initial ME rating in something like a Seminole that will stall before the rudder looses effectiveness, but few pilots who get their ME ratings in light twins go on and make a career out of flying them, it's usually on to "bigger and better" stuff. Stuff that will lose directional control before it stalls. It's the same principle that we run into when we're teaching CFI applicants spins in a Cessna 172. Skyhawks are quite spin resistant and will pretty much recover on their own if you just let go of everything. Try that in some popular light aircraft and you'll ride it in all the way to the ground. That's why you teach the full meal deal when it comes to spin recoveries - even if you do your training in a 172. The same principle applies to Vmc demos in Seminoles. You can't minimize the loss of directional control aspect just because you're training in a Seminole.
 
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There's this whole fallacy of not "turning into the dead engine" in an OEI scenario. This is nonsense. Turns can be made any way, and with any engine out, as long as you keep above Vmc. But here's where this guy messed up: Vmc will increase with load factor as the lift changes on the wings. So as you load the plane up in a turn, you need to increase your Vmc speed accordingly.

I would urge anyone to look at how stall speed increases with load factor. At a 45 degree bank angle, the load factor, and therefore the stall speed has increased 40%. Same with Vmc.
 
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