737NG improved climb performance

[kilo]

Just wonderring for 737NG,when obstacle limited,is it ok to use improved cilmb speeds to get greater T/O weight?Thanx in advance.

[JABBARA]

When limited by obstacle limited weight, this means field limited weight is smaller. When field limited weight is smaller, this means balanced field length is smaller than actual field length. When balanced field length is less than actual field length, this means you have excess runway during lift off. If you use this excess runway length for further acceleration you can achieve a greater V2 after lift off. When you achieve a greater V2, this means you can achieve a greater climb gradient. When you achieve a greater climb gradient rate than required for obstacle clearance, this means you have excess climb gradient. When you have excess climb gradient this means you can start the the take off with a greater weight than before.

Regards.

[ManaAdaSystem]

Or, said in a different way, it is OK.

[CaptainSandL]

Yes, but don't forget to try bleeds off figures before improved climb.

[kilo]

Thanks,guys!but it is still confusing,
the purpose of improved climb is to use excess runway to get higher V2 speed,so we can still get the 2.4%climb gradient at 2nd climb segment with greater weight.we should notice that the method is designed to meet the regulation requirement at 2nd segment of climb,not the obstacle clearance requirement.At some high elevation airports with high terrain,if improved climb is used,the new weight may exceed obstacle limited weight,that's the problem.

[john_tullamarine]

First, the problem is not peculiar to any one Type and bleeds off to squeeze a bit more goes without saying ....

Second, it is not a case of "being OK" .. either the sums justify the RTOW and associated speed schedule ... or they don't.

"Winging it" is never easy to defend in court after the accident ... and be VERY sure that you (the crew) will be very much on your own in this case.

If you are obstacle-limited and seeking a little additional weight, it becomes a matter of redoing the sums. Depending on where the limiting obstacle is located, an overspeed (improved climb performance) schedule may (if the obstacle is distant - say fourth segment) or may not (if the obstacle is close - first or second segment) help. It is all a case of matching a longer takeoff distance against better climb performance (all segments, not just second) and seeing where the obstacle is in relation to the reworked net flight path ... some you win ... some you don't ...

Kilo .. if you redo the sums for an overspeed schedule, the previous limiting weights cease to be valid .. each separate speed schedule calculation set stands alone. If the problem is obstacle limits, then chances are that you will be looking for better than WAT-limiting climb performance. Please be wary of concentrating solely on second segment .. each segment has to be looked at to meet the required calculation set.

This all presumes, of course, that no other required case becomes limiting and spoils the overspeed gameplan.

[JABBARA]

Kilo,

Briefly, ICP method is not necessarily to be for 2nd segment climb requirement (2.4 % for dual engine airplanes- with an engine failure. Which is usually known Climb or Performance limited weight). Which ever is more limiting, either 2nd segment or obstacle limited, ICP is used to increase that one.

Jab.

[john_tullamarine]

With a note that, if second segment WAT is limiting, there is the option of getting some extra weight with a higher speed schedule ... but only if there is the spare runway to permit the increased distances required and the takeoff is not obstacle limited....