Vmc Demo - With or without flaps -

tathepilot

Well-known member
Joined
Oct 5, 2003
Posts
884
Total Time
None
Vmc Demo - With or without flaps - PA34200

PA-34-200 - I'd like to get some insight on this. I have not instructed in a few years. I was taught to teach it with flaps, from a very experienced pilot. A flight instructor at the school, has a problem with the way I'm teaching..

My reason for flaps 25 is to lower the stall speed, I'd hate to stall while doing a Vmc.

What do you think?
 
Last edited:

avbug

Well-known member
Joined
Dec 14, 2001
Posts
7,602
Total Time
n/a
For training, a Vmc demonstration mirrors the certification requirements of the airplane. In certification, Vmc is that speed at which it's no longer possible to maintain directional control at the most unfavorable weight and CG, with the critical engine suddenly made inoperative (and windmilling) and the "good" or operative engine producing maximum available takeoff power. The Landing gear is retracted, and the flaps in the takeoff position.

The airplane must be airborne and out of ground effect. Cowl flaps must be set for takeoff. The airplane should be trimmed for takeoff. A maximum of 5 degrees bank into the good engine is allowed.

Note that the Vmc demo is designed around a worst-case scenario; an engine failure on takeoff. Slow, configured for takeoff, max power. It disadvantages the airplane a little by putting the gear up, removing the stabilizing effect that the gear provides.

Set the flaps as you would for takeoff.

Normally, in a training environment (especially when doing Vmc demos), you won't have passengers in back, and often you won't have an aft CG. You'll be at altitude, where the actual loss of control occurs at a lower airspeed, and so forth...so you're not going to get the absolute worst-case performance. However, you can set up the demo per the standard, because what you're really showing the student is basic handling with an engine out, and most importantly, the need to remove power on the operating engine(s) when aerodynamic control has reached it's limit.

My personal belief is that for safety's sake, there is no need to allow the aircraft to reach the point of departing controlled flight. Blocking the rudder in order to cause the departure to occur a little earlier is a wise move. Give the student some rudder, and as a prudent instructor, you keep the rest.

By allowing the student only so much rudder travel in countering the assymetrical thrust, the departure will occur at a higher speed, and if the student doesn't get the power pulled back soon enough or mishandles the event, you still have rudder available simply by releasing your foot pressure.

Cheap insurance against murphy and students alike, and you're right-minded in considering the relationship to the departure vs. the stall.

There was a time years ago when single engine stalls were practiced as part of the training curriculum, and I still run into those who believe to this day they still ought to be. I'm of the school that believes otherwise (kind of along the same lines that one doesn't need to try cocaine to know it's bad for one and that jumping off bridges could hurt,without actually having to try it). Really the whole Vmc training is as much to show the student why they shouldn't go there as it is to teach any kind of recovery, and that whole effort should be done safely.
 

tathepilot

Well-known member
Joined
Oct 5, 2003
Posts
884
Total Time
None
Great advice avbug! I forgot about blocking the rudder.
 
Last edited:

Tired Soul

Plowing at FL370
Joined
Jul 6, 2004
Posts
257
Total Time
>10000
No flaps, block the rudder.
It is a demonstration exercise where the applicant demonstrates understanding of Vmc and the conditions under which a departure from controlled flight can occur.
It is NOT however an exercise to re certify the airplane. They need to demonstrate understanding and correlation, NOT an actual roll over.
Block the rudder.....
Block the rudder.....
Block the rudder.....
Did I mention to block the rudder?
 

blesko

Well-known member
Joined
Jul 26, 2005
Posts
378
Total Time
7k
the Vmc demo as I have taught it for years has been done with flaps in the takeoff configuration as its to emulate an engine failure on takeoff, with no appropriate recovery. We can block the rudder, I usually keep my hands close to the mixtures as well, as to worst case, shut the motors off and attempt to regain directional control.

On another note on my check airman soapbox, three things discontinue the demo. Loss of directional control, out of rudder travel, or any indication of a stall, whichever occurs first, so that stall light on the secena before reaching Vmc counts as a successful demo.
 

doog

Well-known member
Joined
Nov 19, 2002
Posts
77
Total Time
~1000
On another note on my check airman soapbox, three things discontinue the demo. Loss of directional control, out of rudder travel, or any indication of a stall, whichever occurs first, so that stall light on the secena before reaching Vmc counts as a successful demo.
Does not reaching published VMC speed count as a successful demo?
 

blesko

Well-known member
Joined
Jul 26, 2005
Posts
378
Total Time
7k
as a textbook answer, yes. However, remember actual Vmc speed can change depends on weight, DA, etc. Chances are you'll experience one of the previous criteria before published Vmc speed. Secondly, its a visual maneuver, keep your head outside the cockpit and dont stare at the airspeed indicator for succussful completion
 

PURPLEHAZE21

Well-known member
Joined
Dec 12, 2005
Posts
212
Total Time
69+
More important...make sure your at a safe altitude...then add a few hundred feet...
 

Amish RakeFight

Registered Loser
Joined
Dec 28, 2005
Posts
8,006
Total Time
.
When I trained for my MEL in a Seminole, we performed Vmc demos in the clean configuration with no rudder blocking.

In a sense, the execution and recovery felt like a power-on stall maneuver. Recovery usually happened at the stall; not the loss of directional control. This of course is dependant upon atmospheric conditions, altitude and AC type.
 

avbug

Well-known member
Joined
Dec 14, 2001
Posts
7,602
Total Time
n/a
Does not reaching published VMC speed count as a successful demo?
No, absolutely not. The purpose of the Vmc demonstration is NOT to observe the red line on the airspeed indicator, and it's not to stall the airplane. that's what stall practice is for. A Vmc demonstration is to show only assymetrical handling conditions on one engine...and specifically to show the point of departure.

This may not be achievable prior to the stall, or it may occur higher..but it's up to the instructor to block the rudder properly in order to positively show the student that a power reduction is required at the point of departure. It's important that the student recognize the change in aircraft handling charactor.

There is no value in simply seeing the published Vmc airspeed and recovering, because nothing has been demonstrated. Let's face it, you can fly the airplane considerably slower than that...big deal. Let's also face it...the actual speed at which the airplane can no longer maintain directional control has NO relationship to the published certification Vmc value. The student should be taught that loss of directional control can occur at a higher speed, a lower speed, and both the recovery techniques in the event a departure is encountered, and the proper training and procedures to prevent it from happening in the first place.
 

brokeflyer

Well-known member
Joined
Apr 12, 2005
Posts
2,374
Total Time
1501
Does not reaching published VMC speed count as a successful demo?
demo yes....VMC spin and die? NO.

VMC demo for traingin is exactly that a DEMONSTRATION.

You dont actully go and do a VMC roll over.....cause then you'd be dead.


block the rudder
 

doog

Well-known member
Joined
Nov 19, 2002
Posts
77
Total Time
~1000
So is the answer yes or no? For the demonstration I was taught to start the recovery at loss of directional control (rudder at the stop), stall indication (horn or buffet) or reaching published vmc speed. I do agree with what avbug said... on my checkride I recovered at published VMC.
 

brokeflyer

Well-known member
Joined
Apr 12, 2005
Posts
2,374
Total Time
1501
So is the answer yes or no? For the demonstration I was taught to start the recovery at loss of directional control (rudder at the stop), stall indication (horn or buffet) or reaching published vmc speed. I do agree with what avbug said... on my checkride I recovered at published VMC.

your lucky to be alive then. your instrcutor shoulda been blocking that rudder so that you "lose" control safely.
 

doog

Well-known member
Joined
Nov 19, 2002
Posts
77
Total Time
~1000
your lucky to be alive then. your instrcutor shoulda been blocking that rudder so that you "lose" control safely.
Are you saying that flying down to published VMC is recklessly dangerous even if it happens before the other indications? My instructor blocked the rudder and so sometimes loss of rudder authority came first, but on my checkride I hit published VMC with enough rudder so I recovered. Here is another instructor that teaches it this way:

http://www.dodgenaircraft.com/TrainingVmcDemo.htm

I'm not arguing in my limitted experience that this is how it should be taught, it's just a little unclear.
 

nosehair

Well-known member
Joined
Sep 22, 2003
Posts
1,238
Total Time
24/7
VMC demo for traingin is exactly that a DEMONSTRATION.
The word 'demonstration' is a poor word to be used in flight training, or at least in the context of training objectives.

In this context, it has to mean that the student multi-engine pilot must demonstrate proficiency in recognizing and recovering from an engine out at the Vmc of the airplane.

Kinda like a student single-engine pilot must demonstrate the ability to stall, or land, or execute a forced landing in a single; you know, the stuff he needs to survive a flight.

We don't demonstrate a landing to a student and expect he will be able to do it; he must practice.

The multi-engine student must practice Vmc recognition and recovery just the same as a beginning single-engine student must practice real stalls, and landings, and forced landings. These are fundamental.

The Vmc demo is a fundamental practice maneuver to get the feel of aircracft directional control in the Vmc region - like slow flight is to stalls.

Blocking the rudder is a good initial training exercise, like doing slow flight as a lead-in to stalls.

But, eventually, the pilot must experience and learn to control the airplane as he approaces real Vmc and recognizes and recovers a loss of directional control.

In training aircraft, where Vmc is at or below stall, rudder blocking is good to show, and practice, the loss of directional control of larger/faster airplanes since the ME rating is not make/model specific.

However, the student multi-engine pilot should also take these airplanes to the stall indications without rudder blocking, too.

The bottom line is that the ME student should be trained and have demonstrated proficiency in recognizing and recovering from the Vmc area in actual practice.

This is not dangerous stuff. The airplane is certified to do it. It's like stalls and spins in light single-engine trainers. If you're uncomfortable approaching Vmc, reaching full rudder travel, losing the heading and retarding the throttle, get some more training. Really.
 

brokeflyer

Well-known member
Joined
Apr 12, 2005
Posts
2,374
Total Time
1501
lol go ahead and do it however you want....the plane will win someday. I knew 2 very experienced pilots out doing training in a 414 doing exactly what your doing. They didnt make it back. VMC and a stall can happen very quickly. They rolled over and spun in.

Teaching this is required, however, i ALWAYS blocked the rudder. Reaching the published speed is not the objective, you can make an speed you want to. if the published speed is 90....then say "today its gonna be 100kts OR loss of directional control, which ever occours first."

any other way is just asking for trouble. Just my method of doing it. Whenever I used to give ME checkrides I did the same and I briefed the applicant as such. most were familiar with that because that is how their instructot taught them.

Do it however you want, just don't do it over my house.
 

gulfstream2345

Well-known member
Joined
Dec 30, 2007
Posts
83
Total Time
17000
Blocking the rudder should be done for the demo only. When the applicant goes for the ride they must be able to show knowledge of VMC and demonstrate the recovery from VMC without the examiner/inspector blocking the rudder. As a check airman, CFI, examiner, FAA Inspector, I never blocked the rudder for a demo or checkride. I have given many hundreds of checks in all types of aircraft and have never had a problem. That doesn't mean it can't happen obviously but you have to let the applicant do the task. Of course I had to recover a G3 from unintended inverted flight with an applicant but that is another story.
 

doog

Well-known member
Joined
Nov 19, 2002
Posts
77
Total Time
~1000
Blocking the rudder should be done for the demo only. When the applicant goes for the ride they must be able to show knowledge of VMC and demonstrate the recovery from VMC without the examiner/inspector blocking the rudder.
Well that's consistent with my experience. Did you expect applicants to recover at published VMC if it came before the other indications?
 
Top