Do You Know What Vmc Is?

[uwochris]

Hey guys,

Just reading up on some systems/performance info and the metro, and it's gotten me thinking.

For anyone who flies a turbine a/c, do you know what your Vmc is? Seems like an odd question, but it seems that with heavier, more advanced aircraft (like twin turbines), it can be rather difficult to know exactly what your Vmc is at any instant because of the larger variations in CG, weight, etc, as compared with a small piston twin.

Since Vmc can vary from flight to flight, how do you guys constantly keep track of the varying conditions? Do you just have an "idea" of what Vmc is and how it's affected by the changing conditions, or, do you use perf charts to actually calculate it prior to every flight, similar to what we all did during our ME training?

 

[Ralgha]

Don't care what VMC is. We have other speeds that we stick to on one engine, so it doesn't become an issue.

 

[pilothouston123]

My king air has a redline on the airspeed indicator. I am not sure what that means, but I read somewhere that any thing red in the cockpit is bad.

During all single engine ops, We stay above blueline pretty easlily in the 200.

I don't care if people think props are for boats, Kings Airs Rock!

 

[MauleSkinner]

Everything I"ve flown has Vmc published as "a speed", with no way to calculate changes.

Basically, the way I look at it, that's the reason they teach you all the conditions that go into Vmc. If an engine fails before you retract the gear, and you're still planning on going flying, take a second to make sure that the rudder pedal isn't against the floorboard before you retract the gear and make things worse. If it is, add some bank into the good engine to give yourself some margin. Personally, I'd feather the prop before retracting the gear, given the choice. 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.

An additional note along the lines of the supplements...ALWAYS...and I'm gonna say that again, for those who may not be paying attention...ALWAYS be familiar with the mods on your airplane and any additional requirements they contain. Very few of the airplanes I've flown over the last 15 years have been "stock", and some of them include some fairly substantial performance changes. As our fleet of airplanes ages, the mods just increase.

Anyway, that's how I deal with Vmc in my little world

Fly safe!

David

 

[Ralgha]

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.

 

[siucavflight]

I don't care if people think props are for boats, Kings Airs Rock!

Right on dude!!! King airs rock:smash:

 

[AirBadger]

Don't larger turbine airplanes use V2 as the best engine out climb?

 

[wmuflyguy]

Don't larger turbine airplanes use V2 as the best engine out climb?

No.

V2 provides the necessary take-off climb performance for certification, not the best rate of climb.


It is the speed that is flown from 35 feet to whatever acceleration altitude is for your plane (It varys with plane, but can not be less than 400 feet I believe, but can be higher).

At Acceleration altitude Max continuous thrust is set, the aircraft is cleaned up and then accelerated to, Vfs. This is the final segment climb speed and it is held till the end of the takeoff segment (I think it is 1500 Above airport elevation).

for 2 engine airplane
V2 must give 2.4% climb gradient
Vfs or Vt must give 1.2% climb gradient

 

[Snakum]

Kings Airs Rock!

Ohhhhhh YEAH! imp:

 

[Checklist]

My king air has a redline on the airspeed indicator. I am not sure what that means, but I read somewhere that any thing red in the cockpit is bad.

During all single engine ops, We stay above blueline pretty easlily in the 200.

I don't care if people think props are for boats, Kings Airs Rock!

JETS are for hot tubs