is Vmca mean stall speed?

[dolpinsky]

quick search from internet..
MINIMUM CONTROLLABLE AIRSPEED—An airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall.

so are they the same?

[flyboyike]

No, they're not the same. You searched on the wrong internet.

[justasmallfire]

I wouldn't rely on that information,try here
V speeds - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/V_speeds)

Lowest speed that you still have directional control(control surfaces still have an effect)
Any lower speed and you will lose control when asymmetric,then yes you could possibly spin /stall

[latetonite]

He did not only search on the wrong page, he is still on the wrong URL now.

[dolpinsky]

thx guys for the help ;)

[pattern_is_full]

"Vmca" as a published limitation speed applies only to multi-engine aircraft - the lowest speed at which the rudder (or other flight controls) can maintain straight and level flight with one engine failed (asymmetric thrust). Slower than that speed, and the rudder will be at full deflection, and yet still not providing enough yaw force to maintain straight and level flight - whether the wing is stalled or not.

Since there is no such thing as "Vmca" for a single-engine aircraft, even though a SE aircraft will have a stall speed - obviously the two mean different things.

I can see where some confusion sets in, however, since a basic maneuver in (single-engine) flight training is called "flight at minimum controllable airspeed" - maintaining altitude and making gentle turns while on the edge of the stall. But without a failed engine in the equation.

Maneuvering at Minimum Controllable Airspeed (http://avstop.com/ac/flighttrainghandbook/maneuveringatminimumcontrollableairspeed.html)

But "Vmca" - for a multi-engine aircraft* - means something different than paddling a single-engine Cessna or Piper around the practice area with the stall buzzer screeching. Despite the identical wording.

*always excepting the "push-me-pull-yous" like the 337. ;)

[misd-agin]

Pattern is correct.

You won't stall/spin as soon as you slow below VMCA in a MEL. The plane will start to turn in the direction of the failed engine.

[dolpinsky]

ty pattern and misd :)
it really helps a lot ;)

[barit1]

Now check out Vmcg, and its effect on flight planning.

[dolpinsky]

em..min controllable speed on ground

if an multi-engine aircraft is accelerating on the runway and one engine fails, even pilots apply full rudder they would still cant keep the aircraft on the centerline.
so i guess the importance of vmcg is that it gives pilots time to decide whether to go or to abort the takeoff in case an engine fails after vmcg?

please forgive me if i'm wrong

[john_tullamarine]

Since there is no such thing as "Vmca" for a single-engine aircraft

Not often considered but a large engine single aeroplane can have a situation similar to Vmca at low speed and high thrust. I understand that some OTE exercises in the military have considered this.

You won't stall/spin as soon as you slow below VMCA in a MEL

.. but you may be quite close to stall at book Vmca. Also, keep in mind ASI errors and the reduction in real world Vmca for most lighties as altitude increases.

Be careful .. for there be dragons .. best to stay right away from Vmca as there is little value in playing about with it.

even pilots apply full rudder they would still cant keep the aircraft on the centerline.

The aeroplane won't stay on centreline with a failure at low speed. Vmcg is defined in terms of a maximum deviation from centreline. As the failure speed increases, the deviation can be constrained to a smaller value.

the importance of vmcg is that it gives pilots time to decide whether to go or to abort the takeoff in case an engine fails after vmcg?

Vmcg is a certification thing which is used in the determination of numbers to be used by pilots. I suggest, presuming you are early in your career, that you don't worry too much about Vmcg at this stage.

[barit1]

Not often considered but a large engine single aeroplane can have a situation similar to Vmca at low speed and high thrust. I understand that some OTE exercises in the military have considered this.

I hadn't thought of it in the Vmcg context, but this is very applicable for many prop singles, particularly taildraggers - e.g. Harvard, Mustang, Grummans, etc. Opening the throttle aggressively can result in a ride through the bush long before liftoff speed. And adverse crosswind can be a catalyst! :ouch:

[Linktrained]

I was a "new " Captain on the Car Ferry, so my weather minima had 100ft added to the Company's ie for me it was 400ft.
The a/c ahead had landed a five minutes earlier. At 400ft I was still IFR, so I overshot. Whilst under training I had done a number of overshoots, both two engined and with one feathered.
On this occasion the Starboard propeller went into " Auto coarse" and was feathered.
My speed fell, as |I had started to climb. ( A two engine climb of course)
I had to trade height for speed and got down to 200ft before climbing. I cannot NOW recall my lowest speed.The following day the Chief Pilot said that I had reached Vmcg.
He said that he had not heard of this happening in flight before.
The auto coarsening had been added to the Car Ferry fleet to allow us to operate at 44,000lbs instead of 40,000lbs and had two Pitots to ensure that both engines worked equally on T/O.
I think he ( understandably?) blamed me.
A few months later a similar thing happened and people were killed.
The auto coarsen system was switched off, when not required, after that.

PS
Possibly my having learned and practiced low overshoots in gliders near Toulouse or having a large left foot may have helped. on my occasion.
I see that " engine failure on overshoot" may be practiced on a sim, nowadays. ( Not on a "single - engined "Link Trainer, then.)

[TheChitterneFlyer]

The following day the Chief Pilot said that I had reached Vmcg.

I believe he meant to say Vmca and NOT Vmcg!

[Linktrained]

TCF
You could be right... It was a while ago. ( His, or even my, memory could have slipped a letter !)
We diverted to Lympne, unloaded, had the aircraft checked by GEs and flew a further five trips ( 10 sectors ) with no further problems that day, the weather had improved.
There was no recording of individual flights, CVR etc. then.


I had an early WIREK wire recorder issued to me in the Spring of 1948, but that was heavy and not for an aviation use.

[Old Fella]

Very sadly, those who know of the events leading to the loss of A20-103, a Boeing B707-300 operated by 33 Sqn RAAF, know very well the meaning and implications of Vmca.

Much comment, often misguided, has been on this forum and others over time. As pointed out by Pattern is Full Vmca is that speed below which directional control of the aircraft cannot be maintained with full rudder deflection. For some of we older folk things such as "Dutch Roll Recovery", "Demonstration of Vmca", "Stall Recovery" etc was demonstrated in the aircraft in the days when Simulators were little more than procedural training tools. The first "Simulator" I trained in, a C130A, was a fixed base model with no visual capability. Not so tough for me as a Flight Engineer, but pretty hard work for the pilots.

I have read somewhere that some items in the Qantas B707 FM had not been copied to the RAAF produced B707 FM. I cannot comment, other than to say that the only part of the RAAF B707 FM which was different to Qantas was the cover in the initial period of the aircraft's RAAF service. The publication was, in fact, the Qantas FM in a RAAF binder. Additionally, I have read elsewhere that two engines (double asymmetric) were SHUT DOWN. This, I do not believe. At no time during my association with the RAAF was an engine failure simulated by shutting down an engine. Engines were brought to idle, not closed down. The B707 rudder is the only hydraulically boosted flight control surface on the aircraft. At no time during my B707 experience was practice double asymmetric flight conducted, either in the aircraft or in the simulator. Vmca was demonstrated with one engine at idle, with and without rudder boost at FL150 over Bass Strait, likewise for Dutch Roll recovery.

[HazelNuts39]

The publication was, in fact, the Qantas FM in a RAAF binder.
Just for precision: You are probably referring to the Operating Manual (AOM or FCOM). The AFM is a certification document delivered with the airplane and is not operator-specific.

[Bill Macgillivray]

Never, ever, managed a low overshoot (or any other sort) in a glider! :hmm::hmm::hmm::hmm:

[Linktrained]

Glider low overshoots


Unusual, Uncommon, Agreed.


But at the French National Gliding Centre at Montaigne Noire this WAS a part of my gliding course.


The site was on the top of an E/W ridge with the hangar at the W end and student accommodation at the E. Most "endurance flying" used hill lift., along the ridge. Most landings were to the E. The Low overshoots were so that one could land on one or two fields at the bottom of the hill - unless one wished to continue.


We were also taught how to do a short down wind AND up a steep slope landing, where the glider could be turned around for short take off into the wind again.


It may have been an unusual site. They appeared to teach those who were not all novice pilots ( for whom a flit site might be better).



LT

[Old Fella]

Point taken HazelNuts39, however in the RAAF the C130H model Flight Manual was issued by Lockheed, titled "Flight Manual for RAAF C-130H Airplanes" with the "Lockheed Publication Number FM 382C-71D". This publication was our Operations Manual. So I guess it depends where you are, which type you fly or for whom you fly. The B747's I operated on came with Operations Manuals produced by Boeing, with the rider that in the event there were any differences between the Boeing Operations Manual and the FAA approved Flight Manual, the FM would take precedence.

Regardless of what the manual is called, the RAAF B707-338C publication used in the initial instance was simply the Qantas Operations/Flight Manual inserted into a RAAF binder. What transpired after I had left the RAAF I do not know.

Seasons Greetings.

OF

[dubbleyew eight]

some kind soul bent the ground adjustable trim tab on a Cessna 150 of all things.
a mate was PIC and we went out for a fly to a local restorer of Tiger Moths.
on the flight back my mate asked me to put my foot on the right rudder so that he could give his leg a rest.
at my questioning it eventuated that he had lost muscle control of his right leg and had quietly poked his left foot on the right rudder. when this eventually also gave out he had both feet on the right rudder and both his legs had lost muscle control.
my right leg lasted a few minutes then I had both legs on the right rudder and finally we flew the aircraft with both of us with both legs pressed on the right rudder.
all because the little ground adjustable trim tab on the rudder had been bent to about twice its angle.

so Vmca is one thing. the elephant here is the question of just how long you could actually push hard on the rudder. the need doesnt diminish but the ability of human muscles to push sure diminishes.
...I'll go back to sleep....

[bubbers44]

Falcon 20 training IWas required to Maintain altitude at max power but knowing what would happen, reduced power on the good engine and maintained control.

[bubbers44]

Of course we descended but didn't go below VMC so maintained control. The drill was of course was to demonstrate getting beLow VMC.

[A Squared]

At no time during my B707 experience was practice double asymmetric flight conducted, either in the aircraft or in the simulator.

Really? It's a required semi-annual event at a US airline. I've held commands on 2 4engine types and flight on 2 engines (on the same side) is a required item for every left seat checkride. I've done it in both the airplane and the simulator, and while I can understand not doing it in the airplane, I can't imagine why you'd avoid it in the sim.

Maybe I've misunderstood you.

[Old Fella]

A Squared, my omission. What I failed to include in my post was Vmca. i.e. we never practiced double asymmetric flight in the B707 in the aircraft or in the simulator in relation to demonstrating Vmca. Given that you fly the C130 (L382) I can understand that you would look at double asymmetric in the Simulator, not so sure that I would agree with practicing the configuration in the aircraft. I know we did not practice it in the C130 other than in the Simulator. I assume you do not practice it in the aircraft at low altitude or at a speed anywhere near Vmca2. I also trust that in your aircraft practice you do not shut down the engines but come back to, or slightly above, flight idle.

[A Squared]

Old fella, thanks. Makes more sense when you include "demonstrate VMCA" You are correct, we do not shut down engines, rather use a throttle setting close to flight idle which simulates a feathered engine. No, we do not get anywhere near VMCA2, and the simulation ends at MDA. I have seen 2 engine VMCA, but that was in the sim on a scenario with losing a second engine on a 3 engine ferry takeoff.

[Linktrained]

It was more than 60 years ago, when I did my gliding, as related above, as accurately as I can recall. (See # 13. # 15 or #19 above.)

Time has moved on and the French National Gliding Centre at Montaigne Noire, near Revel seems to have gone too.




The lessons that I learned there, may have been of help when I was having to trade height for speed following one propeller auto coarsening on overshoot at weather minima. To have attempted to retain all height might have led to a stall. My speed got awfully slow.