Vmc demo trouble?

[tathepilot]

I'd like to hear stories from mei's doing Vmc demo's and the wrong things happening:

Such as stalling before Vmc

Also, how much do you allow the a/c to roll before you have the student recover.

 

[Groundskprwilly]

I haven't had any close calls during Vmc Demos....the pattern can increase your heart rate.

I always start with good ground briefing. I make sure the student moves the rudder to full travel and I have the student limit the bank during the entry...try to keep the maneuver nice, smooth and safe.

 

[EDUC8-or]

Yikes!

On my MEI ride the DE showed me all of the crazy and stupid things my students will do to me, so I was somewhat well prepared. Stalling before Vmc has happened a few times. Usually the student figures out what they've done wrong and can recover.

Now stalling at about the exact same time as Vmc, that usually gets my attention. I don't like spins in a twin.

 

[Snakum]

Dumb question ...

Are any common twins approved for spins (hey, that rhymes)?

DQ2 ...

Is giving multi dual as hair-raising at it sounds? Just the thought of it scares me a little. Lotsa bad stuff can happen.

DQ3 ...

In your opinions, what is THE safest twin for giving dual (since all models have their quirks)?

Minh

 

[Timebuilder]

#1. No. At least, I never heard of one.

#2. No. You keep your wits about you, use your checklists, and give good briefings before and after. I also used a pack of file cards that contained all of the steps to set up every maneuver, freeing up my mind to be more attuned to the flying, not the "remembering."

#3. Don't know. I never had a problem in the Seneca 1.


I never got to a stall before loss of directional control because you stop at the first indication of the stall, the stall warning. Usually, the warning did not go off until after directional control was lost, meaning that the HI started to move off the heading you were trying to hold. If you are smart, you have already moved your hand to the "operating" engine to prepare to reduce power when control is lost. At that point, you'd recover by smoothly pulling the power on the operating engine and lowering the nose five degrees below the horizon, then when you reach Vmc plus 10, you come back in with power on the "operating engine". DON'T come in with power on both engines.

A few degrees of lost heading are all that is required to demonstrate the loss of directional control. Don't roll the airplane!!!

 

[Jedi_Cheese]

If you don't mind me asking, why don't you come back with power to both engines?

 

[tathepilot]

Re: Yikes!

Stalling before Vmc has happened a few times.
Now stalling at about the exact same time as Vmc, that usually gets my attention. I don't like spins in a twin.

When you stalled before Vmc, what was the a/c type and characteristics when it stalled?

 

[Timebuilder]

If you don't mind me asking, why don't you come back with power to both engines?

I don't mind at all.

When you learn the Vmc demo, you are partially learning it (aside from the experience of losing directional control and making a recovery) in order to perform it for the examiner on your multi checkride.

In the maneuver, you are simulating a situation where you have lost an engine. The idea is to recover with only the "operating" engine, because the other engine is supposedly still "dead."

Make sure you come in with power after you reach Vmc plus 10 to ensure you don't come back in and roll that puppy over on its back.



"Bbbb...Bad thing!" - Rod Machado

 

[labbats]

Stalling before VMC is the instructor's fault. You should be doing some pre-flight charts to see what the VMC and stall speeds are for your current temps and pressures where you will be doing manuevers.

 

[Timebuilder]

He's right.

This is why we lose twins every year in high density altitude environments.

Be careful.

 

[EDUC8-or]

When you stalled before Vmc, what was the a/c type and characteristics when it stalled?

It was a Piper Aztec. There stall horn wasn't going off, and all of a sudden it began to buffett. I recovered before the stall could break and/or we lost directional control. I was curious if the stall horn was working, so we slowed it down and it did. Went and tried another Vmc demo and the same thing happened. That was enough for the day.

You should be doing some pre-flight charts to see what the VMC and stall speeds are for your current temps and pressures where you will be doing manuevers.

That's one lovely thing about training in Florida. It's nice to have some altitude below you, but during a good portion of the year Vmc and stall speed are the same above 4,000'.

If you are smart, you have already moved your hand to the "operating" engine to prepare to reduce power when control is lost.

I teach my students to keep their hand on the Vmc lever during the maneuver. I wasn't so strict about this when I started teaching multi students, but it usually makes things less interesting.

 

[bobbysamd]

Vmc demo

What you can do is to first demonstrate one. Then, lead him/her into slowly by blocking rudder and blocking less and less rudder until he/she actually does it.

I certainly would not let the airplane get into a roll, especially if you're training in a Baron. You should be training your students to recover at the absolute first sign of yaw. A Baron can snap over fast if you don't watch it.

Don't assume that more docile twins, such as Seminoles, are safer than Barons, etc. People have died in Seminoles because of faulty and too-daring Vmc demos.

Finally, read the PTS and Flight Training Handbook for the correct way of executing a Vmc demo, known therein as the "engine inoperative loss of control demonstration."

 

[Cat Driver]

Scary stuff this playing in the far end of the control envelope with any twin engine airplane............

........just to prove the fact that departure from controlled flight can be quick and difficult to recover from.

Oh well, we get to read about the unsucessful ones on a fairly regular basis.

You would think that in its self would be a lesson.

Cat Driver:

 

[avbug]

I'm very disappointed to read of so many instructors allowing the airplane to stall while teaching or conducting a Vmc demonstration.

If you let the airplane stall, that's your fault, pure and simple.

Block the rudder; limit the student's rudder input to cause the aircraft to lose directional control earlier at a higher airspeed. You are then left with additional rudder for your own use, the student still gets the feel of the proceedure and the demonstration, and you can conduct it safely, on your own terms.

Why on God's green earth (or above it) would you want to fool around with Vmc close to the stall??

 

[IP076]

Has anyone ever flown a freaking twin at high altitude??? Bobby, I know you have! Good points!

You have to block the rudder to have the airplane roll before it stalls. Does the PTS not say recover at first indication of a stall? So, why not? I've done multiple demos and let the student recover at the buffet, or the horn if it actually went off.

The point is you need to train them for the real life scenario, not the checkride. If they're out there flying with one shut down someday, they need to know that if they get the buffet, or the horn, they're approaching a bad situation, and they need to do something about it. Lower the nose!!!

I've seen DE's that teach a recover from actual VMC without touching the power lever. Just using Pitch.

Here's another question..how much do you reduce power on the operating engine if you experience loss of directional contorl? When do you bring the power back in?

Timebuilder, don't mean to be rude or anything, but why look at the heading indicator? Were you doing this for an IFR Student. I've always covered up the instruments and had the student use a reference point outside, if that point starts to move, its the same thing as the heading indicator moving. Remember, see and avoid. I'd venture a guess more people die each year in Mid-Air Collisions that single engine situations.

Disclaimer: Aircraft used were BE-76/PA-44. Altitudes were in the 9000' MSL range at all temps (company policy to not do these below 4000 agl, good idea!). Most training twins will always stall before Vmc if the instructor does not block a rudder. The lowest altitude I ever tried on at was about 5000 in a PA-44, still stalled first. As a matter of fact, I did one in a 310 at 3000' (Different company) and it still stalled first.

The scary part happens when the student does not recognize the stall, and keeps going. Thats when you intervene, and earn your big bucks.



Oh yeah, by the way, show me that "Single Engine Power On Stall Speed" chart your talking about.

edited for spelling, ooops.

 

[Timebuilder]

Here's another question..how much do you reduce power on the operating engine if you experience loss of directional contorl? When do you bring the power back in?

If you are in danger of the roll, and this is the avoidance you are demonstrating with the Vmc demo, then you want to pull the op engine power to idle. You lower the nose (we used 5 degrees below the horizon) and let the plane reach Vmc plus ten before coming back in with power on the operating engine.

Timebuilder, don't mean to be rude or anything, but why look at the heading indicator? Were you doing this for an IFR Student. I've always covered up the instruments and had the student use a reference point outside, if that point starts to move, its the same thing as the heading indicator moving. Remember, see and avoid. I'd venture a guess more people die each year in Mid-Air Collisions that single engine situations.

I think that's a reasonable question. Here's my answer.

If you teach the student to judge loss of directional control by means of an outside reference, then a power loss in instrument conditions does not lead to recall of a previous training scenario when and if this happens. If you use the HI, you can see immediately when loss of directional control happens, while properly scanning for traffic and the 1 kt per second you lose as you gently pitch the nose up, and you can begin the recovery immediately. The HI is good for drilling for use in either VFR or VMC, and the outside reference is only engrained for VFR conditions, making the correct response less likely as a result of that training.

If you train to the "first indication" of the stall, you have not yet stalled.

 

[IP076]

Inside vs outside....

Yeah, that makes sense. I've always taught students that went Private/Single to Private/Multi before starting an Instrument Rating....that's why we always emphasize the outside stuff.

Agreed, I was talking "first indication" and I think most people were referring to "Stalling".

Try this....when you're stabilized at Vyse prior to starting the actual Vmc portion of the manuever, note the pitch attitude. Now, pitch up for an attitude that will bleed off airspeed at approximately 1 knot per second. At the first indication of loss of control, reduce the throttle on the operating engine enough to stop the roll and pitch to the attitude you were at when you started the manuever (Holding Vyse). Increase power slowly on the operating engine until full power is again attained. You should be established back at Vyse by then. If you increase the power slowly, you should never reach a point at which the aircraft will roll again.

That's they way we used to teach it (Basically) and it was the method that yielded the "least ammount of altitude loss" that I think we're all going for.

 

[SpocksBeard]

I have to chime in here with a comment because this was a big problem I saw as a check instructor at my old flight school. I found that the reason many students would get a stall buffet before a loss of directional control was because they were preventing the aircraft from rolling by increasing aileron pressure instead of correcting with rudder. I constantly preached that they should initially put just enough aileron in to establish the 5 degree bank at the beginning of the manuever and STOP there. Then only correct for the yaw with the rudder as the airplane slows, and you almost always get a loss of directional control first. Everytime I have demonstrated it this way I NEVER got a stall indication first. If you think of what you are doing with the ailerons otherwise it makes sense. By deflecting the aileron on the good engine's side up to compensate for the resultant roll you are simply deflecting it into mostly dead air - the airflow is mostly separated in front of that aileron as you slow down and increase your angle of attack. That aileron is not helping to keep that wing down to counteract the roll at high angles of attack. The aileron on the bad engine's side is deflected downward. This dramatically increases the angle of attack on this wing which is exactly the wing you DON'T want to stall. I believe this has alot to do with stall/spin scenarios that occur as a result of a VMC Demo. I used to tell students that once the initial amount of aileron you put in was not enough to keep the airplane from rolling towards the bad engine, it was time to recover. That is more than sufficient as a demonstration of loss of directional control. Personally, I never blocked the rudder. If the manuever is done without increasing aileron input as you slow I don't think there is any need to - at least not in a duchess or apache.

 

[tathepilot]

SpocksBeard

this is a good point. I never thought about it that way. By not using full aileron deflection, directional would be lost quicker without using full aileron which prob would ag·gra·vate an im·mi·nent stall.

I'll have to give it a try.

 

[EDUC8-or]

I never thought about it that way. By not using full aileron deflection, directional would be lost quicker without using full aileron which prob would ag·gra·vate an im·mi·nent stall.

That's the way I was taught and the way I teach my students. If you limit the amount of aileron input you will lose directional control before the stall.

However, on my MEI ride the DE wanted me to maintain 5 degrees of bank throughout the maneuver, which meant increasing aileron input until the loss of directional control. Remember, as you slow down your control surfaces become less effective due to the decreased airflow over these surfaces. By the time we began to lose directional control, I believe I had in full aileron and full rudder deflection.

I DON'T teach my students to use full aileron deflection, but the DE wanted me to see how you can lose control in a hurry and how to prevent these situations with my students.