Vy and Vyse

[sleddriver71]

I would first have to ask the following....

Why are you below VXse or VYse after 4000ft of rwy have passed?

The #1 priority after the airplane breaks ground is to let it accelerate to either one of those speeds. Takes 4-5 seconds at the most.

Now,(assuming I'm above those speeds) if I'm at a sea level field on a cool day, I would feather it/ climb to a safe altitude and turn back.

In the seminole with two people and full tanks I've gotten 500 feet per min. rate of climb with a simulated engine failure. (Avg is 300ft/min).Airport was practically at sea level though.

If I was departing from an airport or in conditions that cause DA to be above the aircraft's single-engine service ceiling....then I would go for the grass on the field.

And as for the advantages of having the same #value for VY or VYse?

It's easier on the brain but I believe the real intention when they publish speeds is so the pilots fly the proper attitude and angle of attack that will result in the best rate or angle of climb. The speed they publish coincidently provides the proper attitude required for that situation.

Same with Best glide speed on singles.....It's the speed that puts the wings at the best angle for LD/maX.

They try to trick you with speed values but it's really to put you at a certain pitch.

It's a dirty secret that cessna and piper did not want you to know.

That's a good thing to wonder, and you're right, in a normal situation, the airspeed should be at or above Vxse/Vyse. But that's not the point, after all if you're flying a properly maintained and preflighted airplane the engine shouldn't fail in the first place. This is more of a "what do I do if it doesn't go by the book" scenario as often emergencies don't care about "the book." Situations(emergencies) outside of the box do happen and it's important to think about how we are going to deal with them in the best possible manner.

 

[MauleSkinner]

I would first have to ask the following....

Why are you below VXse or VYse after 4000ft of rwy have passed?

I don't actually see where anybody said that 4000 feet of runway had passed...the way I read it, it's simply after liftoff on a 4000-ft runway, with no indication one way or another about how much runway was used to this point.

That's a good thing to wonder, and you're right, in a normal situation, the airspeed should be at or above Vxse/Vyse. But that's not the point, after all if you're flying a properly maintained and preflighted airplane the engine shouldn't fail in the first place. This is more of a "what do I do if it doesn't go by the book" scenario as often emergencies don't care about "the book." Situations(emergencies) outside of the box do happen and it's important to think about how we are going to deal with them in the best possible manner.

...I highlighted the key word here--"shouldn't"...unfortunately, properly maintained and preflighted airplanes DO have engine failures on occasion.

And while you're right, emergencies don't care about the book, the way I read the original 4000-ft runway question, it was asked as a "simple, by-the-book" engine failure (if there is such a thing).

Fly safe!

David

 

[UndauntedFlyer]

Why are you below VXse or VYse after 4000ft of rwy have passed?

Of course normal climb profile in any light twin is Vy to about 1000 feet AGL, and of course Vyse is usually not to far from Vy. (In fact on the Seminole it is the same.) So with an engine failure at 400 feet AGL I think it would be totally normal to see airspeed decay quickly to Vyse or Vxse. That would be a likely situation to be in following an engine failure.

Do you not all agree on this?

So in that case just pitch forward while applying corrective rudder, clean up and feather. Be respectful of Vmc and climb out if you're within the performance envelope.


Comments?

 

[JoaoD]

While Vyse may be the most efficient airspeed for rate once established at that airspeed, it is not always the best airspeed to attain in every situation, at least initially. If you are 5 or 10 knots below Vyse and single engine and lest's say 20 feet off the ground, if you pitch down for Vyse, you will most likely make contact with the ground. In this situation, it is better to initially maintain the slower airspeed (pitching up close to Vmc or stall may be required) instead of pitching down to Vyse. Make sure to immediately (in a controlled fashion of course) add max power (keeping controllability in mind), and clean the airplane up (don't forget zero sideslip - usually half a ball deflection and a few degrees of bank towards the operating engine). Be patient and let the airplane slowly accelerate back towards Vyse.
In regards to the chance of the airplane climbing below Vy or Vyse being 50/50, ummm, there is little to no chance involved. Depending on weight, CG, atmospheric conditions, and pilot technique, the airplane will already be in a condition to climb or not climb and it is up to the PIC to know the current conditions as to whether or not it will climb, it's not chance.

Thats a good point, but Vyse for a prop engine is lower than the normal Vy, so we would not pitch the plane further down, we would actually pitch up to achieve that lower Vyse

Maybe the most reasonable explanation is that Vy and Vyse are so close together that it better to have the standard Vy defined as Vyse

Padpilot -> New item by João