VMC Demo Question

[ktulu34535]

Okay If a DE were to not block the rudder on a ME airplane doing a VMC demo the most likely thing to happen would be a stall before reaching VMC

However we are taught that a VMC recovery should include reducing throttle on the operative engine so we can lessen the amount of yaw.

So if you reach a stall before loss of control should you add full power or reduce power???

In my mind it is no longer a loss of directional control, it is a stall and therefore you should recover from it as if it were a stall.

 

[Ace757]

We are taught to recover at the first indication of a stall, or the loss of directional control. I would say that you would still reduce the throttle, and then accelerate through 88kts before adding full power. You do bring up an interesting point though. I never really thought about it. But....you are suppose to be demonstrating the VMC demo, so I would go with the power setting the manuver calls for.

 

[Booker]

Well, I guess you're discussing the mighty Semi, so here's the profile where I work: Recovery is taught to be the same regardless of whether the stall warning or control loss comes first. IMO, this is in line with what the PTS requires. Note 2 for the Task states that "recovery should be made at the first indication of loss of directional control, stall warining, or buffet." Objective step 7 states "recovers promptly by simultaneously reducing power sufficiently on the operating engine..." You do make a valid point, however.

Edited to include PTS guidance

 

[Rick1128]

BE CAREFUL

When I was receiving my multi instruction many years ago in an Apache the first time we did a VMC demo the instructor just happened to pick the perfect altitude. The aircraft stalled at almost the same instant I lost directional control. Result, a spin. So do take care when you choice the altitude to do VMC demos.

 

[jdog78]

I agree that recovery from the loss of directional control should be performed in a manner consistent with the maneuver being demonstrated, in this case the VMC demo. So lower the nose and bring power to idle on the operative engine. I can't say that I've been in a situation in the Seminole where I've gotten close to stalling. One thing I did learn doing my MEI was that holding wings level will increase VMC by about 20 knots in the Seminole so I choose to do that rather than block the pedal. That way, when the nose nods off, you're still well above stall speed and you've provided a realistic demonstration of loss of directional control while teaching the importance of banking slightly into the good engine.

John

 

[bobbysamd]

Vmc demo

You do have one engine inoperative. At the first indication of a stall I would still reduce power on the operative engine per the standard procedure. As Rick mentioned, if all things come together at the most inappropriate time, you could wind up in a spin if you do not reduce the power timely.

Of course, stall speed and Vmc in a Seminole are so close together, which makes getting a true yaw difficult, if not impossible. But we're teaching students to be multi pilots, not Seminole pilots. I would execute the procedure in a Seminole the same as if I were flying a Baron. In a Baron, you do get a true loss of control, and fast, if you don't watch for it.

 

[tarp]

ktulu:

Let me use some very important words -

This is a "demonstration" under "simulated" conditions.

Under "actual" engine failure (read not simulated) and the airspeed indicator far below blue line, the question is how will YOU treat that remaining throttle/thrust lever?

Let me say that again in a different way - you have a wounded bird - one dead engine and you are nursing it to the nearest airport. While fumbling for an airport diagram, talking to ATC trying to get help, trying to enter some kind of a pattern to land, you look up just in time to see the airspeed right near the red line and the stall warning light starts flickering.

Do you?

a.) shove in the coals because you are near stall - remember only one engine will respond with thrust.

b.) lower the nose and gain airspeed to Vyse while gently increasing power.

c.) let go of the airplane because somebody said on the flightinfo board that if you just let go, the airplane will recover itself.

Only one answer will result in you not creating a flaming hole in the ground.

What you are "demonstrating" in this "simulation" is that you will be very aware of the tendancy of a twin engine airplane to enter a spin if you apply assymetrical thrust near red line or Vmc. This is a lifesaving maneuver. This is a practical demonstration to show that you understand the snakebite waiting in all multi-engine planes.

Please. Let's be careful out there.

 

[great cornholio]

VMC fun

Tarp is right on track with this one. The DE blocks the rudder to make this demonstration safer than doing an actual VMC. Also you have the option of if you get too scared to put the coals to the "inop" engine. In real life you do not have this option and if you are in a stall and increase the power on the good engine "just because that is how you recover from a stall" then think about what is going to happen. You have to make sure that you think about all possibilities. I think all of us would agree that in a single or a twin with both engines working then puttin the coals to it is the way to recover from the stall. However if you do this in a twin with one engine inop (doesnt even matter if its the critical one or not) then you are buying a one way ticket to pilot heaven. The reason is that this WILL cause a spin. Remember a spin happens when you stall and are uncoordinated. You stall so you add the power on the only engine that works and now you have thurst on just one side of the plane (to put it in signle engine a/c terms SLAM THE RUDDER FULL IN ONE DIRECTION) Now you have yaw and next is the spin. The great thing about twins is that they dont have to be spun during certification so even the test pilots might not have spun the thing. The plane might be so uncontrollable that you will not recover and you will make the 6 oclock news. So the best way to recover from a stall in a twin with one engine inop is to cut both throttles to get rid of the yaw and point the nose down and trade in some altitude for airspeed.

 

[ktulu34535]

thanks

Thanks for all the great replies.

The reason why I posed the question was because an instructor I know told me to recover as if it were from a stall. But from the overwhelming response I have received I would think that this instructor is rather wrong.

Thanks

 

[Mickey]

Block the pedal during Vmc demos!!!