View Full Version : Flex take-off question
testpanel
14th Dec 2010, 11:44
Hi all,
Just a question on a T/O in flex.
Do you have to adjust the V1/Vr speeds?
If so, why?
Thanks!
Mad (Flt) Scientist
14th Dec 2010, 11:54
Hi all,
Just a question on a T/O in flex.
Do you have to adjust the V1/Vr speeds?
If so, why?
Thanks!
Yes, you may have to adjust the scheduled speeds (including V2 as well as V1 and Vr).
It depends on the particulars of your aircraft and the degree to which you are trying to optimise the performance from the specific runway.
Suppose, for example, your aircraft is constrained by V2min rather than any Vr-based considerations. You leave V2 set at V2min. But now the a/c is slower to accelerate (lower thrust). So a higher Vr may be required to ensure that the minimum V2 is achieved at the right height. This in turn may permit a higher V1 to be selected, if it was constrained by V1.
SinglePilotCaptain
14th Dec 2010, 21:02
And just remember Flex is a great way to stretch out that engine overhaul to 35000 hours....
Nothing like burning up 12000 feet of runway, flying it to the fence and pulling the nose up...so exciting.
Spooky 2
14th Dec 2010, 21:20
Very dumb answer to an intellegent question.:mad:
Just HOW MANY usernames does this one have?
SNS3Guppy
15th Dec 2010, 02:59
He was Johns7022 (and of course SSG, et al), but it's the same poster...who "outed himself" just today by signing with his other names. He needn't do so, of course, because he's clearly the same cat.
Brian Abraham
15th Dec 2010, 04:57
SinglePilotCaptain, are you really so thick that experience teaches you nothing? I guess the answer is yes.
In an extension to that question....errr...you remember, the original question!
Whether you use maximum power, Derate 1 or Derate 2, for your next takeoff, there is a stabilizer trim setting for each specific t/o power setting.
But you will find that there is no stabilizer setting specific to a Assumed Temp (Flex) power takeoff, that's because the assumed temp power takeoff is not a limiting setting, and the thrust levers can 'legally' be advanced any time during the ground run of the airplane, with the 'normal' stab setting already set, that's no problem!
But, with a combination of not advancing more than the original setting, a normal takeoff, and the fact that the stab trim setting takes into account the 'pitch up' moment created by the applicable power set, in this case it will be a lower power setting (assumed temp), so an amount of out-of-trim (nose down) will be noticeable when rotating at Vr.
Ever noticed that! :ooh:
Brian Abraham
15th Dec 2010, 08:56
EW73, standby for SinglePilotCaptain to tell you you don't know what you are talking about.
Slasher
15th Dec 2010, 16:03
SPC - just look at flex take-offs as a way of protecting the
engines if the next guy happens to lose one, and the only
thing separating him from a violent death is that one and
only remaining engine being operable and not clapped out.