Assumed/flex Temp Effect On TORA And ASDA
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Join Date: Dec 2006
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Assumed/flex Temp Effect On TORA And ASDA
Hi...
The following is an excrept from HANDLING BIG JETS page 204,(a)
[ The assumed temperature method of reducing thrust to suit T/O weight does so at constant thrust/weight ratio and the actual T/O distance TORA and ASDA at reduced thrust are less than at full thrust and full weight by approximately 1% for every 3 degrees centigrade that the actual temperature is below the assumed temperature]
can this statement be validated,and if so,should this reduction/correction be applied or is it already accounted for in the runway analysis chart?
bf
The following is an excrept from HANDLING BIG JETS page 204,(a)
[ The assumed temperature method of reducing thrust to suit T/O weight does so at constant thrust/weight ratio and the actual T/O distance TORA and ASDA at reduced thrust are less than at full thrust and full weight by approximately 1% for every 3 degrees centigrade that the actual temperature is below the assumed temperature]
can this statement be validated,and if so,should this reduction/correction be applied or is it already accounted for in the runway analysis chart?
bf
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Generally, already applied in the runway analysis chart....at least the ones I have used, anyway.
A very deep derate (L1011-200, +50C) at nearly max weight, will use every bit of the 13,000 feet at JED (34L), for example, while still meeting the second segment climb requirement.
Up close and personal with the far end of the runway....
A very deep derate (L1011-200, +50C) at nearly max weight, will use every bit of the 13,000 feet at JED (34L), for example, while still meeting the second segment climb requirement.
Up close and personal with the far end of the runway....
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Thanks 411A.....we too operate to and from JED, will try a high flex T/O from JED at the upcoming hadj season when we're fully loaded and then some
see if i can take all the adrenalin...
see if i can take all the adrenalin...
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1% for every 3 degrees
On 411A L1011, a deep derate was limited to -25%, on modern Airbus this can be upto -40% depending on type/engine combination.
Mutt
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Remember that the quote comes from some time ago. Modern performance calcs/capabilities can muddy the picture.
Derate is available on the 777 300 er to 40% and assumed temps of 72 degrees C are not uncommon.
Also, the optimisation of V2 can change the picture, V1 being increased to "almost" balance the field and Vr increaseing to take advantage of any spare runway length, so increasing V2 and climb performance/wt available.
So a small change in the assumed can give a relatively large change in speeds or a change in optimum flap for the same wt/runway.
Derate is available on the 777 300 er to 40% and assumed temps of 72 degrees C are not uncommon.
Also, the optimisation of V2 can change the picture, V1 being increased to "almost" balance the field and Vr increaseing to take advantage of any spare runway length, so increasing V2 and climb performance/wt available.
So a small change in the assumed can give a relatively large change in speeds or a change in optimum flap for the same wt/runway.
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Mutt,
A bit off topic, but having seen a few of "yours" using Surabaya, was wondering if you stuck to your normal procedure and used Balanced Field, or used SWY and CWY?
We don't from there, but we're not travelling anywhere near as far as you do.
Just wondering........
Regards,
Old Smokey
A bit off topic, but having seen a few of "yours" using Surabaya, was wondering if you stuck to your normal procedure and used Balanced Field, or used SWY and CWY?
We don't from there, but we're not travelling anywhere near as far as you do.
Just wondering........
Regards,
Old Smokey
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OS, last time that i visited Surabaya, they had removed the clearway from their documentation, we therefore stopped using it, this resulted in a 4000 kgs reduction. We dont use the stopway. Luckily, the resulting takeoff weight is just enough to make it non-stop most of the time.
Mutt
Mutt
