Vmcg is the speed where you can't maintain heading with the
critical engine failed and there is not enough rudder or
tire steering. Yaw is most severe at low speed because the
rudder is ineffective and some airplanes have steering
problems with tire geometry.
Vmca is the airborne speed that is what most people thing of
when you mention Vmc. Reduction in power lowers the speed
as does having the downward prop blade being close to the
fuselage. But when Vmca is close to or at Vs, loss of
heading and the stall happen at the same time, that leads to
a spin.
Closing the throttles regains control since there is no Vmc
without the asymmetric power. But the pilot must be willing
to cut power and dump the nose to a glide attitude or a
stall will happen and that leads to crashes. Even in a
single, after an engine failure on take-off, with the nose
5-15 degrees above the horizon you must push the nose down
to 2 or 3 degrees below the horizon or it will stall too.
But once you do that to retain control in a twin, you can
fly away to a crash site of your choice, often back to the
airport for an emergency landing.
To get the benefit of a twin, you plan for an engine failure
all the time and only fly in the critical parts of the
envelope when you have other options. On take-off, abort
for any indication below Vmca. After that, rotate at Vmc+5
and accelerate to Vyse. Don't retract the gear if there is
runway ahead you can land on (below 50 feet, you need about
4000 feet in Duchess) if you have practiced an airborne
abort before.
Once you have run out of runway and retracted the gear get
to circling minimums (400 feet) ASAP.
Remember Vyse is the speed target that allows you to
take-off or approach and land with a margin. When landing,
approach at Vyse allows a safe go-around. Once landing is
assured, you will reduce power and land.
--
James H. Macklin
ATP,CFI,A&P
"swag" <***@yahoo.com> wrote in message news:***@i3g2000cwc.googlegroups.com...
| Jim, I need help. What are vmca and vmcg?
| --and with regard to Vmc, I thought that that was the
minimum
| controllable airspeed with one engine not operating and
the other one
| at full power. With reduced throttle on the operating
engine, Vmc goes
| down. So in the case of a landing aircraft, it is
actually possible to
| approach and rotate below Vmc without loss of controll.
The closer you
| get to a deadstick landing, the lower the rotation speed
could be.
| Obviously there are reasons not to do this--I am just
commenting on
| control issues. But please help me on vmca and vmcg.
|
| Jim Macklin wrote:
| > The first speed that comes to mind should be
reprogrammed to
| > be Vyse, you'll live much longer.
| >
| >
| >
| > If you look at an old multiengine manual, such as the
Beech
| > BE 95-55 they advertised very short take-off and landing
| > distances and the plane will do them. But you would
rotate
| > 10 knots below Vmc and fly the final at about Vmc. If
the
| > engines were running, no problem. Loss of an engine
meant
| > almost immediate crash unless you were very quick and
lucky.
| >
| > Modern POH says, rotate at not less than Vmc+5,
accelerate
| > to Vxse-Vyse quickly. Gear remains down until Vyse or
| > you're out of runway to land straight ahead or you reach
| > circling minimums. On landing, maintain Vyse until
landing
| > assured.
| >
| >
| >
| >
| >
| >
| > "Emily" <***@yahoo.com> wrote in message
| > news:***@comcast.com...
| > | Jim Macklin wrote:
| > | > I didn't mean to say that either. Vmca (Vmcg too)
are
| > very
| > | > important, but Vyse is the first performance number
for
| > a
| > | > light twin [along with Vxse], similar to V2 for a
| > transport
| > | > category aircraft.
| > | > Vyse is shown by the blue line and that is the
target
| > | > airspeed.
| > | >
| > | >
| > | I have a multi rating, thank (two of them, actually).
| > |
| > | I was simply throwing out the first airspeed that came
to
| > mind.
|