Climb limit on airbus family

[mauri3xx]

I have a question to submit:
during slat retraction (flap lever from 1 to 0) the climb limit changes.
On A319 increases about 2/3% and on the others (A320-321) increases about 1/2%.
Anybody knows why?
Thanks in advance

[hawk37]

Well, I'm not familiar with your or Airbus's terminology, but for all aircraft I know of, retracting the flaps and or slats will produce less drag, as long as you're not too far below the minimum drag speed for that new configuration. Less drag means more thrust available, hence a higher climb gradient if you were to fly not too far off that minimum drag speed.

[Old Smokey]

Just what type of Climb Limit are you referring to mauri3xx ?

Are you talking of Climb Thrust N1 limit ? (Makes sense, particularly if the hydraulic system has bleed air driven pumps).

Are you talking of a Pitch Attitude limit ? (Makes sense because of the new configuration, although the reference would be degrees and not %).

My guess is that you're not speaking of any Climb weight limit, as you're describing a dynamic in-flight situation, where the weight cannot be changed, so cross that one from the list.

A little further information please

Regards,

Old Smokey

[mauri3xx]

You're right Old Smokey!
I'm sorry about that... I was speaking about climb limit N1 ...

Originally Posted by Old Smokey

Just what type of Climb Limit are you referring to mauri3xx ?

Are you talking of Climb Thrust N1 limit ? (Makes sense, particularly if the hydraulic system has bleed air driven pumps).

You're right! I'm sorry about that... I was speaking about climb limit N1

Are you talking of a Pitch Attitude limit ? (Makes sense because of the new configuration, although the reference would be degrees and not %).

My guess is that you're not speaking of any Climb weight limit, as you're describing a dynamic in-flight situation, where the weight cannot be changed, so cross that one from the list.

A little further information please

Regards,

Old Smokey

[Getold]

Originally Posted by mauri3xx

I have a question to submit:
during slat retraction (flap lever from 1 to 0) the climb limit changes.
On A319 increases about 2/3% and on the others (A320-321) increases about 1/2%.
Anybody knows why?
Thanks in advance

If this occurs when using FLEX TO thrust, it is because the flex temperature used brings the TO thrust below CLB thrust. This is not allowed under certification rules, so initial CLB thrust is reduced. Once clean, thrust gently increases to "normal" climb thrust.

[hetfield]

What is "initial" climb thrust?

Regards

[Getold]

Originally Posted by hetfield

What is "initial" climb thrust?
Regards

Total thrust reduction may not be more than 25% of TOGA, nor less than climb thrust. So to further reduce FLX thrust, when thrust levers are pulled back to CLB detent, initial CLB thrust is less than certified. Once flaps are retracted, thrust again increases to certified CLB thrust.

[hetfield]

@Getold

Thx for the explaination.

...initial CLB thrust is less than certified.

So certification rules had been adjusted accordingly.

[mauri3xx]

thx to evrybody!

Originally Posted by hetfield

@Getold

Thx for the explaination.

...initial CLB thrust is less than certified.

So certification rules had been adjusted accordingly.

[Clarence Oveur]

......nor less than climb thrust....

Sure it is not less than cruise thrust? On my Airbus we can certainly flex to less than climb thrust.

[Max Angle]

Have noticed the same on our 319s, is it really worth doing the take-off at such a large flex that a few minutes after TO the power is higher than it was
in the first place. Seems like a waste of time really, why not just take climb power at the start of the roll.

[Getold]

Originally Posted by Max Angle

Have noticed the same on our 319s, is it really worth doing the take-off at such a large flex that a few minutes after TO the power is higher than it was
in the first place. Seems like a waste of time really, why not just take climb power at the start of the roll.

Engine life is directly proportional to peak EGT. Period. Proof - so much effort goes into maximising FLX TOs.

[Max Angle]

I agree but I would have thought that peak EGT is occuring after take-off once the new climb power setting is reached not during the take-off roll, certainly fuel flow is much higher during this phase. I will make a note the EGT next time I fly one of the little suckers and see when it peaks, pretty sure it won't be during take-off.

[antonov_124]

The wing design. It changes. Plus the aero dynamics. The learjet 45L ceiling is about 45 000 ft. the boeing 737's is about 38-39 000 ft. Its all in the aerodynamics man. At least thats what i think./..