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-   -   Climb limit on airbus family (https://www.pprune.org/tech-log/225741-climb-limit-airbus-family.html)

mauri3xx 12th May 2006 19:47
Climb limit on airbus family
 
:confused:
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 12th May 2006 21:31
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 13th May 2006 01:49
Just what type of Climb Limit are you referring to mauri3xx ? :confused:

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 :bored:

Regards,

Old Smokey

mauri3xx 13th May 2006 06:13
You're right Old Smokey!
I'm sorry about that... I was speaking about climb limit N1:bored: ...


Originally Posted by Old Smokey
Just what type of Climb Limit are you referring to mauri3xx ? :confused:

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:bored:

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 :bored:

Regards,

Old Smokey

Getold 13th May 2006 06:43
Originally Posted by mauri3xx
:confused:
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 13th May 2006 07:58
What is "initial" climb thrust?

Regards

Getold 14th May 2006 07:07
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 14th May 2006 08:20
@Getold

Thx for the explaination.

...initial CLB thrust is less than certified.

So certification rules had been adjusted accordingly.;)

mauri3xx 14th May 2006 09:12
:) 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 14th May 2006 09:36
......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 14th May 2006 10:18
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 14th May 2006 14:51
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 14th May 2006 15:28
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 15th May 2006 02:19
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./..


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