PPRuNe Forums - Approach speed vs Rotate speed

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Approach speed vs Rotate speed

For aeroplanes is Vr ever greater than Vapp?
Why?

(I’m, for a specific reason, assuming the answer to the first question is “no” btw....but just want to check my assumption!)

Perhaps I should add...in given wind conditions for the same runway?

Quote:

Originally Posted by TangoAlphad (Post 10298966)

The problem is there is a million variables to take into play.. thrust derate / assumed temp / company V1 policy etc however at a quick play..

Boeing 737-800 Short Field Performance

LGW EGKK 26L Calm Wind Isa Day
62000kg
Flap 30 Vref = 143kts

Take off: 22'000 lbs thrust de-rate, assumed 44°c with no improved climb gives at Flap 5 Vr 136.

Improved climb and Flaps 1 = Vr 149.

Interesting, in a bad way, for my theory. However, it’s interesting you mention the short-field performance 737...as I was basing my assumption on an airfield with a considerably shorter runway than EGKK...

Very kind offer TA...I suspect I should consult with the airlines and aircraft types concerned (with a very specific - and limiting - airport in mind).

But thanks for your input. If I have any further questions I’ll give you a shout :ok:

Not sure what your theory is going to say, but the problem you're going to run into - and have done so, in fact, with the example given - is that takeoff and landing are radically different configurations, and the rules for setting speeds associated with the speeds are also different as they address different considerations, and those two speeds don't even address the same factors. Any aircraft with a very "clean" takeoff configuration will need correspondingly high takeoff speeds, including Vr. The same aircraft in a very dirty highest-lift configuration could have very low landing speeds. In fact, since you can do all kinds of configuration changes, they are almost two different aircraft, in some ways.

i am wondering, from some clues in what you've said, if there is a constraint in your question that you've left unspoken? Are you asking about the case where both the takeoff and landing performance is equally limited by available runway length? (Almost certainly at different weights for almost any aircraft...)

Quote:

Originally Posted by Mad (Flt) Scientist (Post 10299401)

i am wondering, from some clues in what you've said, if there is a constraint in your question that you've left unspoken? Are you asking about the case where both the takeoff and landing performance is equally limited by available runway length? (Almost certainly at different weights for almost any aircraft...)

Thanks Mad

You’re quite correct in your wonderings. In fact the runway is so specific that I will need to address my question to those operators.

I was a little naive in my original question by having this airport in mind rather than considering all factors for all airports.

Cheers for your reply :ok: