PDA

View Full Version : IMPROVE CLIMB


aviatorpk
5th Jul 2001, 23:43
What is improve climb ????

fireflybob
6th Jul 2001, 00:00
I presume you mean "improved climb" in the context of performance.

V2 (the one engine inoperative initial climb speed) is normally 1.2 X Vs (Vs= stall speed). However the best angle of climb speed, in the take off config, is in the range of V2 + 15 to V2 + 25.

In the case where the aircraft is below the "runway" limit, V2 may be increased above the minimum in order to secure a better angle of climb after take off.

However, in practice the procedure of improved climb is used to increase the take off weight so although the use of a higher V2 improves the angle of climb this is countered by increasing weight up to the point where the angle of climb is not less than thw WAT limit (2.4% gradient, I think)!

If V2 is increased then this will generally affect V1 and VR also.

Hope this helps!



------------------

john_tullamarine
6th Jul 2001, 08:31
The improved (often called overspeed V2) climb makes use of spare runway to permit the use of higher than minV2 speed schedules to gain additional RTOW if the AFM so permits.

We are concerned more with climb rate than gradient, although the appropriate WAT or obstacle requirements need to be satisfied. The shape of the climb versus speed curve is such that the best climb invariably occurs at some margin above V2min. As the rate of improvement decreases sharply as the peak climb point is approached, the practical limit for useful overspeed V2 scheduling is around V2min+25.

[This message has been edited by john_tullamarine (edited 06 July 2001).]

mustafagander
6th Jul 2001, 16:22
aviatorpk,

I, too, assume you mean "improved climb".

On the big Boeings at least, V2 is always below Vmd for the T/O configuration. Hence going faster improves climb performance - better L/D ratio. This requires, of course, more field length, higher V1 and Vr speeds and the big one, no high close-in obstacles.

It needs careful analysis, not spur-of-the-moment stuff to ensure that there are no hidden snags like brake energy limits etc.