B737 improved climb

[Jimmy The Big Greek]

I would like to know if it is allowed to use both "Improved climb speeds" and "assumed temperature" at the same time. If anyone has any document regarding this I would be very grateful.

[bucket_and_spade]

Don't see why not - we do it all the time in the B757! No reference for you I'm afraid though.

[Nightrider]

Using the Flygprestanda TL charts does not restrict the use of assumed temperature when following the improved climb speeds.

The Boeing Performance Tool for the computer allows for the same procedure.

As a matter of fact, the BFT gives you very high speeds always as it prefers the improved climb speeds. A lot of temperature reduction reduces the "sweating" for the engines. In the upper temp range I saw that 1 degree assumed gives about 5 degrees reduction in the engine, a lot when you think about 10 - 20 degrees assumed temp reduction, as is often possible.

[Jimmy The Big Greek]

I spoke with a captain and he told me that it is not good to use assumed temperature and improved climb together. The reason for that is because with assumed temperature, the accelaration will be slower thus when reaching the already high v1 from the improved climb there will not be enough runway to stop in case of an emergency.

[john_tullamarine]

he told me that it is not good to use assumed temperature and improved climb together

The calculations consider these points. On paper the problem is addressed. If, on the day, performance is similar to the paper calculation, likewise.

[BOAC]

Despite a bit of prodding,. 'Asparagus Airways' (well, they are owned by an Icelandic fruit and veg man:)) strictly forbade the combination on the 737.

[Rainboe]

No wonder you were canned by AA! Sounds embittered to attack them like that!

[Denti]

We use all combinations of derate, assumed temperature, improved climb, alternate MAC forward to either get the highest reduction possible or carry the highest possible load out of every field. All that is calculated using the boeing performance tool, so it is actively supported by boeing.

Even back in the days of paper tables we used to have improved climb tables for assumed temperature calculation, so it is not really a new thing.

[411A]

Going back even further (B707) engine derate (not flex, as it was not developed at that time, as I recall) and improved climb speeds were allowed, weight depending.
L1011?
About the same, flex and improved climb together are allowed.

Improved climb was/is especially useful at many airports, ZRH runway 16, for example.

[john_tullamarine]

not flex, as it was not developed at that time, as I recall

If not the first to use flex .. Qantas' Wal Stack (lovely chap) was an early player with this game on the 707s. I recall a lecture at Uni (he was an Industry guest lecturer for the odd course) wherein he described the raised eyebrow response of a crew at the start of flex ops .. the pilots were a tad surprised to see the F/E push the throttles up to set climb power after T/O. Thereafter he specified climb power as the min flex for T/O.

[BOAC]

JT - I'm a bit 'on side' with Wal there. In my blissful ignorance I have long thought that should be the 'bottom line'. It does, however, now start to get complicated when we get the option of 'CLB 1' and 'CLB 2' on our playstations:)

[411A]

... now start to get complicated when we get the option of 'CLB 1' and 'CLB 2' ....

Or, in the case of the L1011, CLB 1, CLB2, CLB3....and a further derate of two more on the latter...and this from the beginning with FMS ops, circa 1976 or thereabouts.

[Old Smokey]

There's no reason from a performance perspective why reduced or derated thrust cannot be used with Improved Climb V2 speeds.

It was originally a Boeing SUGGESTION that a Standard Flap setting be used for each aircraft type, with V2 min speeds, with which Reduced / Derated thrust was acceptable and preferred.

The SUGGESTION went on to say that if it was necessary to (A) Use a lesser than 'Standard' Flap setting, (B) Use Packs OFF, or (C) Use Improved Climb V2 speeds to extract the last Pound or Kilogram of Takeoff Weight, then no messing around chaps, use Full Thrust. (In other words, if you have to resort to a few trickeries to carry the weight, don't fiddle with the thrust).

Then along came the EFB and OPT (Onboard Performance Tool) which uses Improved Climb AND Reduced / Derated Thrust, and the SUGGESTION went out the window.

Along the way, many operators (including my own) adopted the SUGGESTION as a SOP.

History lesson over, back to the latest slanging match forum, hmmm, which one was that???

Regards,

Old Smokey

[BOAC]

Indeed, OS, and the problem is often that to get those extra few kg of RTOM you have to go to Imp Clb, and then you have far in excess of the required RTOM, so not allowing a reduction is using up engine time unnecessarily. Good to see that commonsense eventually rules!

[john_tullamarine]

Whether we like it or not .. the bean counters have a significant say. Given that this Industry has dreadful bottom line stats (who, in their right mind, would invest money in scheduled operations, outside a monopoly ?) we just cannot afford to be overly conservative for mum and the kids .. and hope to retain a paid position of employment.