PilotDAR wrote:
I'm not aware of any light twin which prohibits, or advises against planned Vmc demonstrations at all, though obviously there are appropriate cautions. I'm nervous thinking that a permitted maneuver was not demonstrated by the pilot during training, because there was a fear that the new pilot could not fly the plane with the precision needed to achieve the demonstration, without creating needless risk. If the plane were to be that "on the edge of controllable", it would not be certified. It's "on the edge" is the single engined performance to get over the hedge!

!

From the Pa 44 Seminole POH (edited for brevity)

Section 4.51 Air Minimum Control Speed

Vmc is the minimum flight speed at which a twin engine airplane is directionally controllable as determined in accordance with the FAR's.

Vmc has been determined to be 56 KIAS and is in a stalled condition. The Vmc demonstration approaches an uncontrolled flight condition with power reduced on one engine.

I agree with BPF... but I agree with the "spirit" of what PilotDAR said—pilots need to fly more precisely and have more discipline in their aircraft handling.

The Vmc demo should be done with partial rudder for the reasons BPF states.

Furthermore I think this fixation on Vmc is misplaced. The number that matters is Vyse. Vmc on all the light twins is so far below Vyse that climb performance at or near Vmc will be negative and a significant altitude loss will be required to accelerate the aircraft to a speed that will allow it to climb.

Yes.

This IMO should be the fundamental take away from the concept of Vmc.

Kind of.

Single engine flying (as opposed to not flying) should be focused more on Vyse. However, Vmc should be focused on what it is (which is stated in the name).... the minimum velocity for positive control of the airplane.

You simply can't let the aircraft get any where near Vmc when it is on one engine, especially if you are close to the ground.

Very true! You also cannot let the airplane stall close to the ground... but we teach stall recoveries because pilots do get themselves in those situations. Same with Vmc.

As for encouraging smooth accurate flying, holding Vyse with the ball exactly half out is where I concentrate my practice. The student challenge is to duplicate my demonstrated rate of climb on one engine. It is a great illustration of the requirement to fly accurately and smoothly as even small deviations from the ideal have a dramatic negative effect on performance.

Yes!

From the Pa 44 Seminole POH

Thanks BPF, That's a type I have never been involved with.

The Vmc demonstration approaches an uncontrolled flight condition with power reduced on one engine.

The use of the term "uncontrolled" should be take as a warning that controlled flight may not be possible to maintain, but that does not mean that the plane is suddenly on its back. In a Vmc demonstration, the instant full pedal will not prevent a heading change, "control" (of the heading) is lost. The plane is still flyable, just not on the heading you want. Similarly, during the demonstration of a stall, the instant that the controls reach full nose up, or the nose pitched down, pitch control can no longer be maintained. Again, it does not mean that the plane cannot be flown.

I agree, that those two events occurring simultaneously is a recipe for getting a plane on its back with careless control handling. But "uncontrolled flight" is a warning to the pilot that they will have to recover it, but while that is being [promptly and effectively] done, the plane might remain relatively recoverable (not getting much worse).

I have flown a few single engine aircraft types for which the reaction of the aircraft at the point of becoming "uncontrolled" was to be unpreventably upside down, and getting worse. That aircraft would be uncertifiable for poor handling.

The foregoing is not a challenge to BPF's wise training practices at all. Rather, it is just a reminder to pilots that an aircraft going from "controlled" to "uncontrolled" flight, might be very gentle and subtle, and requires extra pilot attention to recognize, and return to controled with appropriate and gentle control inputs, rather than a panicked waving of hands, and texting "OMG waddoIdo?" on social media! If the plane does not flop on its back instantly, why should the pilot?

Fly the plane....

unpreventably upside down, and getting worse

I find it a bit sad that the unstated assumption
is that as soon as you are upside down, you
are dead.

That isn't quite true. I love being upside down.
Admittedly most straight-and-level pilots when
confronted with this, might pull back and try to
do a high speed split-S, which won't be pretty.

However, if you simply pull both throttles to
idle, and let the nose fall a bit to the inverted
45 downline, and let a little airspeed build (to
help the roll rate) you can then do a very
pretty 1/2 roll to the upright 45 downline.
Feel free to make it a little shallow to reduce
the fear factor.

To me, that's just plain (sorry) fun. And
with a bit of practice, you can even spiral
that maneuver so that you can do it with
entirely positive G.

I remember being told that you can't do a
1/2 cuban-8 without inverted fuel and oil
systems, and that's just silly. All you have
to do is allow the nose to continue to fall
while you 1/2 roll upright on the exit - sort
of a variation on a barrel roll.

So, being upside down in a twin is no big
deal. What is a big deal is allowing yaw to
develop, because of the high PMI. Actually,
if anyone ever does that, could you please
test out my theory for using differential
power to recover from a spin in a twin?
I've always wondered how effective that
would be, but no one ever mentions it.

<insert obligatory reference to lorentz field equations to ensure complete incomprehensibility>

One thing I have learned teaching new/low time students is that sometimes they have brain farts and occasionally they do quite unexpected and potentially dangerous things.

An example of this was one day when we were doing the engine failure on the overshoot drill in a Seneca 1. We were at 4000 ft AGL all set up with full flap gear down and at ref speed of 95 mph. I said go around, he pushed up the throttles and I then pulled one back to simulated the feather. At that moment he pulled the control wheel full back. Instead of immediately taking control I tried to talk the student into getting the nose down but in the maybe 2 or 3 seconds I was talking the airspeed decayed to the stall and the aircraft snap rolled. When I took over the aircraft was inverted and about 45 degrees nose down. Fortunately I had completed my aerobatic instructor course 6 months earlier and so while the events were disconcerting I knew what to do to effect a recovery. Had I not had aerobatic training this event had the potential to end very badly

After we leveled out I asked the student why he did what he did and he was at a loss to answer except to say he got mentally overloaded and the lizard brain took over.

I learned a few things about teaching flying in multi engine/ higher performance aircraft that day

1) If you are working near the edge of the envelope and the student is either not keeping up or does something unexpected, take control immediately

2) The retraction time of the landing gear decreases substantially if you are inverted when you select gear up

Big Pistons Forever wrote:I feel I must rebut Pilot DAR on this one because I think his advice verges on the dangerous. It is all fine and dandy to say go take a student and fly at the the for actual real Vmc even though it will often be very close to stall, just fly with skill and precision on speed and with gentle handling. The reality is that many students doing the initial multi rating are in the 100 to 200 hr TT range and have never flown anything bigger than a C 172. They will be nervous and struggling to keep up and an inadvertent large control movement can cause an upset very quickly.

So are you saying it is dangerous for a student, but an experienced pilot can get away with it without any problem ? If that is the case, what's wrong with a demo with an instructor on board ? I don't think anybody is trying to get new students to do this exercise solo. A bit like the spin recovery exercise for a PPL. Potentially unsafe when done solo and with an overloaded mind, but perfectly safe with an instructor on board to guide you through it.

Also, a demo is something that is (normally) planned. This demo can actually be one of the more relaxed parts of the ME rating (at least it was for me): you won't get an unexpected engine failure, you don't have to be set up for complicated ifr approaches and your instructor is taking care of the radio. All you have to do is fly the aircraft, you don't even have to remember any rpm and throttle settings, just use what you need.

2) The retraction time of the landing gear decreases substantially if you are inverted when you select gear up

Not if you're inverted pulling 1G...

One thing I have learned teaching new/low time students is that sometimes they have brain farts and occasionally they do quite unexpected and potentially dangerous things.

Yeah, but this is a separate (and entirely valid) point. Pilots, particularly candidate ones, have very little "wiggle room" to excuse stupid flying with brain fart, or other equally lame excuses. This to me, is a pretty blatant indicator of a candidate not yet ready. Either, they can not prioritize "Aviate - navigate - communicate", or they simply don't have what it takes at all. In either case, they have some skill building to do before they move up.

Yes, I had a "900 hour" CPL right seat to me in a Navajo, and he was flying. When I said calmly, "I'll just do this" and reached over to retard the right throttle, as the plane yawed well over, and he said "What's happening?!", I realized that he was a little further back the learning curve than I expected. Obviously, loading him more was not going to work out well.

But, an unready candidate is not an excuse to not safely demonstrate and co fly real world situations in a proper training environment. I think there are lots of training examples of "I'll demonstrate this, but this is not a solo maneuver". Example, I have an PPLH, and two type ratings, but have never flown a full on autorotation - "watch, but never attempt".

If the instructor cannot safely demonstrate loss of directional control at Vmc or stall, while maintaining safe flight for demonstration, I find this worrisome. I have been extremely inspired by skillful demonstrations of flying presented to me over the decades. It has made my want to be a more skillful flyer, rather than just driving the plane around.

In my opinion, if training is dumbed down so as to be safe, its about the same as taping foam on all the corners of the furniture. Furniture and flying have sharp corners - Brushing them gently reminds you to move carefully around them, and not hit them hard! But, you gotta brush them!

PilotDAR wrote:If the instructor cannot safely demonstrate loss of directional control at Vmc or stall, while maintaining safe flight for demonstration, I find this worrisome. I have been extremely inspired by skillful demonstrations of flying presented to me over the decades. It has made my want to be a more skillful flyer, rather than just driving the plane around.

I'm not sure I understand why the method of Vmc demonstration described in the Instructor Guide for the ME rating is insufficient.

In the twins I teach in, there's a big placard right on the top of the student's panel that says "ONE ENGINE INOPERATIVE STALLS NOT RECOMMENDED". If you dig into the POH, you realize that the spin-recovery for the type is the manufacturer's best guess - they didn't test it. The book also explicitly says you have to knock off a Vmc demonstration when you get any indication of a stall. So my unwillingness to demonstrate the loss of directional control that occurs at the stall may leave my students uninspired, but I still think it's a good idea to studiously avoid the thing I'm teaching them to studiously avoid.

For me, skill = precision. I want my demonstrations to be accurate to the knot, foot, degree, etc. But I'm not very interested in doing something the manufacturer clearly thinks is a bad idea so that I can inspire a student with my prowess.

But I'm not very interested in doing something the manufacturer clearly thinks is a bad idea so that I can inspire a student with my prowess.

And yes, I quite agree. The manufacturer's recommended practices should prevail.

PilotDAR wrote:

But I'm not very interested in doing something the manufacturer clearly thinks is a bad idea so that I can inspire a student with my prowess.

And yes, I quite agree. The manufacturer's recommended practices should prevail.

I think depending on the student there could be a high risk of them deciding, "That looks easy. I'm going to give it a try."

Which could actually be more likely if you do it well enough to make it look easy.

Further I believe there are some things that should just be accepted such as Vne speeds. Do you demo them to show it can be done? Just because there is a bit of room for error, does not mean I should check it out.

If you want to be a test pilot that is a good thing but in my opinion you should have the support of a full test program.

I would be happy if multi students simply knew
that there are two problems with engine-out:

1) control (red line)
2) performance (blue line)

and that they have absolutely nothing to do with
each other. In fact they are completely opposed.

Keep It Simple, Smart guys. Pilot don't need to know
string theory or even quantum mechanics.

My multi doesn't have a red line....

Does ATC give you much static about the
250 knots below 10k rule?

Oh yeah, multi students also need to learn
about janitrol heaters.

I feel the need to state here. I do dumb things beyond the written limitations of machines sometimes.
Last week I rode my heritage soft tail just over 8.3 miles in five minutes.

So yeah. Sorry if I'm sounding preachy today. That's not my intention.

iflyforpie wrote:My multi doesn't have a red line....

Yes but it is so ugly you have to wear a paper bag over your head so people can't recognize you

Seriously though the C 337 has the most sensible arrangement of engines for a light twin, unfortunately most pilots want the "sexy" look of the engines on the wings even though this arrangement gives less performance and is less safe......

PilotDAR wrote:



In my opinion, if training is dumbed down so as to be safe, its about the same as taping foam on all the corners of the furniture. Furniture and flying have sharp corners - Brushing them gently reminds you to move carefully around them, and not hit them hard! But, you gotta brush them!

"safe" to me means that for every part of the flight the pilot knows the risks vs rewards of what he has done and has made a conscious decision that the rewards justify the risks. In the context of flight training I think "safe" should not mean take no risks, it should mean that risk are intelligently managed. Teaching that appreciation and management of risk should be integral to the flight training program and as the sophistication of the training increases so should the sophistication of risk management decision making.

In the context of this discussion if you are flying a piston engine twin and you have a real engine failure than allowing the airspeed to be anywhere near Vmc will as the accident record clearly shows, likely result in an accident. It is important to show how flight below Vmc will kill in two ways

First failure to take action to recover will result in the aircraft entering uncontrolled flight and the second and equally important point is that even if you regain control the aircraft performance will be so degraded that you are going to crash if you are any where near the ground.


So back to the "safe" argument. I can easily demonstrate both of the above points by demonstrating the Vmc at an the artificially higher speed that results with a limited rudder demonstration. The symptoms of a Vmc upset and the correcting actions required are going to be exactly the same than if the aircraft was operated at the intersection of the stall and the true Vmc. The abysmally low climb performance of all the light twins will still result in a pretty good demonstration of the performance loss at a much below Yvse airspeed. To me this represents a reduction in overall risk with exactly the same reward.

Like I said earlier I place the emphasis in multi training not on exploring the very far corners of the SE flight envelope but of the absolute necessity to attain and maintain Vyse in all circumstances if you have a real engine failure. I also emphasis the critical importance smooth and accurate flying has on achieving the most performance from an aircraft which will at its best barely climb.

If that is "dumbed down training" then I guess I am guilty as charged....

ps As a kid I bet you were the one who jumped off the top of the barn to prove you couldn't fly by flapping your arms.

The theoretical: http://www.avweb.com/news/airman/184438-1.html

The practical: http://www.pittspecials.com/articles/MultiTakeoff.htm

Don't do this: http://www.youtube.com/watch?v=YqmomTUVsAw

This might be of interest to some on here: http://i.imgur.com/9zSPzyS.jpg

Two things I would point out.

1) "After ensuring proficiency in controlling the airplane at Vsse, it is permissible to slow down with one engine inoperative toward Vmca to further increase the trainee's awareness, proficiency, and confidence."

2) "WARNING - FAIRCHILD AIRCRAFT RECOMMENDS THAT THE INHERENT SAFETY MARGINS OF SIMULATING ENGINE FAILURE, RATHER THAN ACTUALLY RENDERING IT INOPERATIVE, BE USED DURING PILOT TRAINING."