Do You Know What Vmc Is?

[ptarmigan]

V1 has to be greater than Vmcg and Vr has to be greater than Vmca. V1 cannot exceed Vr. The description of V2 above is correct, just will add that V2 cannot be less than Vr and yields the shortest distance from the beginning of takeoff roll to a specific screen height. This will be less than Vy in most cases.

 

[threegreen]

I haven't seen a published Vmc speed for the EMB-120. There's no red line (or blue line) on the airspeed indicator. If the critical engine fails at V1, the rudder is on the floor, some aileron deflection is applied, and the gear is raised. It flies just fine, unless the prop didn't feather, then the other pilot has to get it feathered quick or you're pretty fooked.

it's in the AFM... It depends on weight of course but it's something like high 80s low 90ish.

That said, it really doesn't matter what Vmc is provided SOP is followed. At least that's what people tell me.

 

[MauleSkinner]

it's in the AFM... It depends on weight of course but it's something like high 80s low 90ish.

That said, it really doesn't matter what Vmc is provided SOP is followed. At least that's what people tell me.

As long as you've got a fair margin between the SOP operations and Vmc, you're probably right. Individual airplanes may vary

Fly safe!

David

 

[wmuflyguy]

Have a look at this site, It is essentially a summary of what is posted by everyone above, with more definitions.

http://adg.stanford.edu/aa241/performance/climb.html

 

[Ralgha]

it's in the AFM... It depends on weight of course but it's something like high 80s low 90ish.

That said, it really doesn't matter what Vmc is provided SOP is followed. At least that's what people tell me.

Cool, I'll look it up on Tuesday...

 

[time builder]

The E90 in our hangar does show a 7-knot increase in Vmc with the prop windmilling...that's why autofeather has to be installed and operating per modification supplement. This 7-knot increase, by the way, increases Vmc ABOVE the "decision speed" AND rotation speed that our performance charts are predicated on.

David

7 Kts is all? The BE99 I flew had a Vmc of 91, but without autofeather, they said you should plan on more like 130 for Vmc, although I never saw it in writing.

At low altitude (say below 10,000), I don't know that you're going to have a significant difference in your normal Vmc with a turboprop. Remember that one of the key factors in Vmc is engine power output. Unless you're temp limited or something you should be able to get full takeoff power out of your turboprop at significantly higher altitudes than a normally aspriated recip.

With normally aspirated engines, however, you lose manifold pressure with altitude right from the beginning, and thus, your drop in Vmc with altitude due to the loss of engine power.

 

[Alchemy]

On RJ's and most other jets with fuselage mounted engines, Vmc is so far below stall speed that it is never really published. There is no pupblished "VMC speed" for the WSCoD I fly. I asked about this during systems class and that was the answer I was given.

Even on jets with wing mounted engines, I believe the rudders are large enough and the stall speeds high enough that Vmc is not a relevant speed for single engine performance. Not having the P-factor, accelerated slipstream, spirlaing slipstream, and torque issues also helps push Vmc down to a fairly low airspeed.

Now for a 707 or a DC8, I'd imagine that Vmc might be a factor if you lose both engines on one side....can't say for certain though.

 

[MauleSkinner]

On RJ's and most other jets with fuselage mounted engines, Vmc is so far below stall speed that it is never really published. There is no pupblished "VMC speed" for the WSCoD I fly. I asked about this during systems class and that was the answer I was given.

All the jets I've flown with fuselage mounted engines have published Vmc speeds...a couple of them have rudder boost or rudder bias to reduce Vmc, and it needs to be operative as well.

Fly safe!

David

 

[Alchemy]

All the jets I've flown with fuselage mounted engines have published Vmc speeds...a couple of them have rudder boost or rudder bias to reduce Vmc, and it needs to be operative as well.

Fly safe!

David

Interesting, do you recall what the approximate airspeeds were? I assumed it would be 100 knots or less for most types with fuselage mounted engines, which is probably below stall speed for everything except a few citations.

 

[wmuflyguy]

I have been told Vmcg on the RJ is 90kias, I have not come across what Vmca is.

We are jsut told do not fly slower than min-speed appropriate for the aircraft configuration (They are on a plastic card in the cockpit)