Update on Vmc demo?

[N8632Y]

I've seen older posts on Vmc demonstrations with MEI's and their techniques.
I remember some interesting ideas with MEI's blocking the amount of rudder the student could use.

I'm at that point again in my training and was wondering on getting feedback from some of the seasoned MEI's on technique, tricks, and safety precautions?
thanks in advance.
steve

[Kristin Winter]

Scott,

I think that it depends somewhat on the plane. When I was teaching in a PA-39, I was uncomfortable with the proximity of Vmc, to stall. Vmc first is not a problem. Stall way before Vmc is usually not a problem. It gets interesting when they come together.

As the instructor, be very ready to pull the power back and stuff the nose down if the plane starts to roll on its own. As you are doing that, neutralize the ailerons and jump on the opposite rudder.

I don't like all that drama and it isn't particularly good for the plane. That is why I tended to block the rudders. I haven't done enough Vmc demos in Maggie to have a good technique figured out yet, but I should do that one of these days.

[jeffrey aryan]

Just make sure you are above 5000' AGL. When you practice.

Jeff

[N8632Y]

Kristin,
I've only been the student/pilot performing the Vmc demo, till now.
I've heard of "blocking the rudder"? ok, so, critical engine, left is simulated lost, speed is slowing from blue line, approaching red line, right engine is full forward, plenty of altitude, but not high enough so that a stall will be reached first, ......
and the MEI has their right foot "under" the right rudder to block the amount of travel the student can get, therefore limiting how low Vmc will actually be, so instead of reaching Vmc at theoretically at 90, you reach it at 95 mph, leaving room for recovery.
But in the event of the student passing Vmc, and not reacting, yes, easy to move power to idle, but if your foot is under the right pedal, it will take some dancing to get it out and stomp on top of it? Since i've never done it, this is what i have visualized?
steve

[N8632Y]

Blocking the Rudder? I had a thought, maybe the MEI's are keeping both feet on top of the pedals, but keeping enough pressure on top of the left pedal to limit how far the right can go down? This makes more sense to me.
So exactly how is the rudder blocked?
steve

[Zach Grant L1011jock]

Steve,
Don't block the rudder. You want a repeatable event, and there is no good way to dupicate the same event with the rudder block technique. What is the reference that you are using? The best technique in the twinkie, and the method that was requested to be used by the FAA was to block the ailieron. Put your fist vertically on your right leg under the yoke and there is no way you can stall before the plane rolls away. Not enough aileron to bank into the good engine and the classic roll will ensue rather quickly. This will happen 10+ mph above the first indication of stall every time, and is very safe.. pull the power back and recover.
-Zach

[N8632Y]

Zach,
The reference I was thinking of were a few posts on the subject a few years back when you first came to the ICS. I remember the topic and the mention of tricks MEI's used, but couldn't find the old posts. So I thought I'd reopen the topic.
A "repeatable event", interesting, yes, blocking the rudder will never be exactly at the same place, so therefore the speed at which Vmc occurs will be different each time. Makes sense.....
Block the aileron, makes sense too....so basically you are not allowing to yoke, or aileron to go past level? Do not let the aileron bank 3-5 deg. into the good engine? correct?
When the ICS comes to the NE for training, I will be there.......there are a few things I would like clarification on....next will be RPM management....
Thanks again,
Steve

[Zach Grant L1011jock]

Steve,
I was talking of the reference of the location of the rudder...I understood your not finding the past posts. Sorry. As for allowing the plane to bank into the good engine, absolutly you do, and there is plenty of aileron to do this. Once you get to the point that the yoke is hitting your fist, you have basically cut the aileron travel in half, and the plane will loose roll controll before it runs out of rudder, but it will not maintain directional control without the ailieron, and will thusly lazily roll off to the left. Very benign, and very much like Vmc in much larger more powerful aircraft.
-Zach

[steen]

[Zach Grant L1011jock]

[N8632Y]

[Zach Grant L1011jock]

[steen]

[N8632Y]

[Zach Grant L1011jock]

Steve,
The problem with this whole maneuver is that any increase in altitude for safety sake, as well as any change from the "worst case" (thats in quotes, because it is untrue in some instances) certification conditions for Vmc will cause the Vmc and the stall speed to get closer together, not farther apart, and that is a bad thing. As was stated before the wing with prop wash over it has an artificially reduced effective AOA, and thusly stalls at a lower IAS than the wing with no prop wash that has a true flight path effective AOA. Stall AOA for a specific airfoil does not change! The effective AOA that the wing sees can change for a number of factors similar to changes that can affect the Vmc speed. All of this leads to a situation that theoretically even is a crap shoot based on conditions, and combination of conditions (unless you have a highly instrumented test aircraft...and non of the aircraft we fly come close). Like any marking on the ASI, it is a general target. Simulating the effects Vmc, and all of these conditions, while well away from them is possible, and does show the tendencies of the aircraft in a controlled and safe environment.
-Zach