Improved Climb

[Denti]

Try a -700 with derate 2 and 60° C ATM (or 40% reduced thrust). Works out at around 75%. Have done it a few times myself.

[BOAC]

Originally Posted by misd

Used when you have long runways(to allow increased V1 adjustment) with -
1. terrain clearance issues after departure

- not in my experience. It has been used to enable an improved climb performance (at a more 'efficient' V2) where runway length permits and there are NO significant obstacle problems, thus achieving the required gradient at a higher weight than at standard speeds.

I'm not comfortable with the concept of using it purely to allow a 'high-speed tricycle' event at a vastly reduced power setting.

[misd-agin]

BOAC - flying out of KEGE(6000'?) 'Improved Performance' is a way of life, especially when the temperature gets to freezing or higher.

Medelin Colombia(6000'?) IMP PERF is a fact of life. San Jose(MROC) Costa Rica(3000'?) sometimes. Don't recall if KGUC (6,000'?) or La Paz Bolivia (13,000'?) used/required IMP PERF.

Come see the mountains from low altitude, they're beautiful!

[Cough]

I've seen high 70's%N1 in a 737-500, mega derate as we were positioning... Always seems daft to be departing with less thrust than you subsequently use to climb but hey ho.

Seem to remember that the PDCS in the 737-200's (ADV!) didn't used to let us do that. Once you went below climb thrust that was that! Price of progress huh!

[Jane-DoH]

I thought with jet-powered aircraft the faster you fly, the faster you climb...

[john_tullamarine]

and there are NO significant obstacle problems, thus achieving the required gradient at a higher weight than at standard speeds.

Very much a case of massaging the numbers to get the closest to whatever you seek.

You can go for

(a) better climb - period

(b) better climb capability - now we can increase the weight to bring the climb back to what you need either for WAT or obstacles

(c) improved obstacle clearance - not for close-in obstacles (straight away they are compromised by the net flight path's being lower initially due to the longer TOD - however, once the overspeed NFP intersects the min V2 NPF, the obstacle profile is enhanced (read either improved clearances or add some weight to reduce the sums back to minimum requirements).

(d) some mix of the above ....

[411A]

(c) improved obstacle clearance - not for close-in obstacles (straight away they are compromised by the net flight path's being lower initially due to the longer TOD - however, once the overspeed NFP intersects the min V2 NPF, the obstacle profile is enhanced (read either improved clearances or add some weight to reduce the sums back to minimum requirements).

Indeed so.
Runway 16 at ZRH is a prime example.
With both the B707 and the L1011, improved climb (or, as it was known then on the 'ole 707...overspeed takeoff) allowed for enhanced payload, for long range ops.
OTOH, BOM runway 14 was not long enough, and besides the obstacle was too close in....however, an emergency turn was available for OEI...left, to avoid the granite.

Improved climb procedure has been in use for many years, with positive success.
IE: nothing new.
Just another tool in the toolbox.

[Stuck_in_an_ATR]

Can the takeoff thrust be actually reduced to below climb thrust setting? I thought it was not allowed?

[mutt]

actually reduced to below climb thrust setting?

Embraer dont allow it, Airbus initially encountered this problem with the A300 and imposed a restriction that reduced couldnt be less than climb, I think that might now apply to all Airbii....

As for Boeing?

Mutt

[PantLoad]

Mutt...

Yes, Boeing as well, as per my old company's SOP.

Fly safe,


PantLoad

[Green Guard]

Can the takeoff thrust be actually reduced to below climb thrust setting? I thought it was not allowed?

SOP may not "allow" it ? Is it because it is not mentioned in SOP ?

It may be confusing if we do not use logic. How can one have enough (reduced) thrust to Take-Off and be "not allowed" to keep SAME (reduced) thrust as Climb Thrust....
even if it is less then Normal Climb Thrust...

Of course it is less because all Reduced calculations are done JUST for Take Off and not for Climb...It may be on AirBus and Boeing
but for example on good 'ole L1011-500 SOP even Climb Thrust was "allowed" to be reduced according to GW.

[Denti]

On the 737 we have three different climb thrust settings, full climb, climb 1 and 2. The FMC automatically selects climb thrust depending on take off thrust selection, however that can be changed manually. And even climb 2 (aka most reduced climb thrust) is more than full reduced take off thrust. That is allowed, at least in my outfit.

[411A]

...but for example on good 'ole L1011-500 SOP even Climb Thrust was "allowed" to be reduced according to GW.

Still is, actually, in five different increments. Other models as well, even the -1.
Very useful.

[mutt]

How can one have enough (reduced) thrust to Take-Off and be "not allowed" to keep SAME (reduced) thrust as Climb Thrust....

Technically there is nothing wrong with keeping the same/lower takeoff thrust, but as people are more used to reducing power for climb, the restriction was placed there to guard against human error.

Mutt

[misd-agin]

Jane-Doh - each aircraft as a 'best rate of climb' speed. Climb at a speed higher than that and you do not climb faster.

The decrease in rate of climb is not that great for the speeds (approx. best rate of climb +20 to +70) that we typically climb at.