Vy and Vyse

[stlcards]

Does anybody know why and what advantage an airplane would have when Vy and Vyse are the same. For example in the Piper Seminole Vy and Vyse are the same speed, 88kts.

 

[flyboyike]

Well, we know that Vy is that speed at which there is the most excess power available for climbing. On most light twins Vy=Vyse or at least Vy~Vyse, because it is at that speed that there is that excess power, albeit from the only remaining engine.

 

[MauleSkinner]

Does anybody know why and what advantage an airplane would have when Vy and Vyse are the same. For example in the Piper Seminole Vy and Vyse are the same speed, 88kts.

The biggest advantage would be that you don't have to remember as many numbers

Fly safe!

David

 

[sleddriver71]

I think the Seneca II I used to fly had the same Vy and Vyse numbers (89 kias if I remember correctly). I would agree, the biggest advantage is that you don't have to remember as many numbers.

 

[SBD]

Just remember, if you lose an engine below Vy or Vyse good luck. Chances that airplane will still climb is about 50/50.

 

[Metro752]

Just remember, if you lose an engine below Vy or Vyse good luck. Chances that airplane will still climb is about 50/50.

who told you that?

 

[sleddriver71]

Just remember, if you lose an engine below Vy or Vyse good luck. Chances that airplane will still climb is about 50/50.

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.

 

[Tonala2k]

Sleddriver,
Thank you for your input. Very well delivered. You hit a lot of very good points.

As to the original question. I'm sure it is incidental to design and not designed that way. With smaller engines we don't have must thrust in the first place with both engines operating. I'm looking to get check out in a CE-425 Turbo prop. Lose an engine on this bad boy an that's a lot of power loss. Still plenty of excess power, but now where near as much as before. I think that if we really crunched the numbers, true Vy would be slighted different than Vyse, but hey, as it was said before it easier to remember one number, especially when they are so close together.

(Please note, this is opinion only. I have no authority on the matter)
$0.02

 

[Metro752]

you pitch for level flight, not a number, and if you can, get a climb rate after you clean up the airplane, if you can get Vyse, super dooper,

there is no set number since it changes with all variables/conditions

in the seminole its anywhere from 75-80s after you get cleaned up, initially, for level flight, and maybe 100fpm climb

 

[UndauntedFlyer]

Great Post

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.

The above information from Sleddriver is 100% correct and very well said. These are concepts that most multiengine pilots are not taught and do not know. This information can save your life but with some skill involved too. While this concept of pitching to near Vmc can save your life, it can also kill a pilot that doesn't know his airplane. Stall characteristics of the wing is a big factor here. Thanks for posting this information.

 

[MauleSkinner]

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.

Now THAT's one of the best things I've seen in print since I read the "Safety Information" section of Beech POH's...

Know, BEFORE YOU TAKE THE ACTUAL RUNWAY (I think the emphasis is mine...I took this quote out of my Baron Powerpoint presentation), whether you can maintain control and climb out if you lose an engine while the gear is still down. It may be necessary to off-load some weight, or wait for more favorable temperatures.

The rest of the multi-engine flying portion of this document is pretty good, too, btw...I recommend it.

Fly safe!

David

 

[SBD]

" in the seminole its anywhere from 75-80s after you get cleaned up, initially, for level flight, and maybe 100fpm climb," My thoughts exactly. On a hot humid day where you are carrying some weight, the Seminole climbing while under Vyse or Vxse is really a crapshoot. The PIC's skill and knowledge will determine what events will play out. We can all calculate the best Single Engine Climb performance with the charts, but can you honestly tell me that you feel comfortable with that information. There have been times while performing a Vyse demo for students that we couldn't maintain altitude to save our lives.

 

[SBD]

This maybe a little off topic but since we are talking about Vxse and Vyse this might be a good place to ask this. On my MEI FAA ride the DPE asked me this scenario based question. After you rotate on the takeoff you lose an engine on let's say a 4000 foot runway and the only thing beyond the end of the runway is fields and grass. You are below Vxse and Vyse, do you
A) Continue on the climb and try to clean it up, feather, and return for landing?
or
B) Close the throttles and try to plant it straight ahead?

 

[SBD]

Fields grass and trees. Sorry.

 

[MauleSkinner]

This maybe a little off topic but since we are talking about Vxse and Vyse this might be a good place to ask this. On my MEI FAA ride the DPE asked me this scenario based question. After you rotate on the takeoff you lose an engine on let's say a 4000 foot runway and the only thing beyond the end of the runway is fields and grass. You are below Vxse and Vyse, do you
A) Continue on the climb and try to clean it up, feather, and return for landing?
or
B) Close the throttles and try to plant it straight ahead?

Here ya go...the answer is in there somewhere
http://forums.flightinfo.com/showthread.php?t=74653