VYSE VXSE questions

aviategw

aviategw

Well-Known Member
Single engine absolute ceiling is defined as the altitude at which Vxse and Vyse are equal. If this is the case, why is Vxse and Vyse listed as the same (85 KIAS) in the POH for the BE-76 Duchess?
 
Would it be safe to assume that the speeds are so close at SL that they just rounded up/down to make them the same? Single engine service ceiling for the PA-44 @ MGTOW (3800lbs) is 3800ft. I can't imagine the absolute ceiling being that much higher. In the Seminole, Vxse is 82 and blue line is 88. Not that much of a difference.
 
Thus my question-- the single engine service ceiling isn't all that high on the Duchess, but I know it's higher than sea level, especially on a standard or colder than standard day.

Anyone else have any guesses? I don't know the answer to this one.
 
Don't flame me for guessing here, because all my books are 1,400nm away and I'm not an MEI, but...

Vxse = aircraft still gains altitude, but only at a rate of about 50' per minute (service cig. single engine)
absolute cig. = aircraft will not climb any higher

So, how can Vxse/yse be = to absolute cig?

Forgive me it may be the Turkey kicking in....but my brain has shut off.
 
aviategw said:
Single engine absolute ceiling is defined as the altitude at which Vxse and Vyse are equal. If this is the case, why is Vxse and Vyse listed as the same (85 KIAS) in the POH for the BE-76 Duchess?
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Those weights are for maximum gross weight. At Sea Level on a standard at max gross...a Duchess cannot climb. So...the speeds are the same because at max gross the SE absolute ceiling is on the ground.

This should be part of a pilots preflight planning. Under these loading conditions, a pilot should understand that if an engine fails after takeoff...the situation should be treated the same as in a single engine airplane.
 
B767Driver said:
This should be part of a pilots preflight planning. Under these loading conditions, a pilot should understand that if an engine fails after takeoff...the situation should be treated the same as in a single engine airplane.
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Can't it be treated a little differently? Because if you lose an engine in a single, you've lost everything, so let's say you're descending at -600fpm... In a twin, you've only lost your excess thrust (and a little bit more) so you may be descending at -50 fpm, so the turn back to the runway might be more possible? I'm just asking because I really don't have much experience in single engine ops...
 
If you loose one engine on a airplane where VXSE = VYSE then you can still hoold altitude maybe not totally in a turn because of increased force vectors in the turn but it would be a lot safer in a max gross weight engine failure at takoff and you should be able to turn back for runway alltho you could loose 500 ft easily I would think... Anyone have more input??
 
Chris_Ford said:
Can't it be treated a little differently? Because if you lose an engine in a single, you've lost everything, so let's say you're descending at -600fpm... In a twin, you've only lost your excess thrust (and a little bit more) so you may be descending at -50 fpm, so the turn back to the runway might be more possible? I'm just asking because I really don't have much experience in single engine ops...
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Well you should have a real good idea before takeoff what the expected level of performance should be should you lose an engine after takeoff. But, your procedure after an engine failure should have you spending a second or two to evaluate the actual performance of the airplane. If you are maintaining altitude or climbing slightly...you could have the performance to fly an abbreviated pattern back to the runway...or at least away from obstacles or populated areas. So, you're right...even though you know expected level of performance from your preflight performance analysis...always evaluate your actual flight path and proceed from there.

However, if I was descending and not at least maintaining altitude...I'm looking for the most favorable landing spot and heading towards it. Because now...I'm pretty much a single engine airplane...even though it has a slow descent rate. Set up blue line...which if you aren't climbing ....is your slowest rate of descent...and set up a good off airport landing.
 
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