Airbus performance

[bertie187]

Could anyone kindly explain to me what TREF and Tmax reflect on airbus performance charts. I am a tad confused.
thanks

[NigelOnDraft]

Practical effect is Min and Max Flex you can use... Max Flex in turn I believe is 25% reduction in power, which is max derate allowed (?)

[captain87]

"Could anyone kindly explain to me what TREF and Tmax reflect on airbus performance charts. I am a tad confused."

Hi bertie187,
in fact there are more complications for this topic.
Now the Airbus pilots compute all takeoff data (including Tflex) by using a computer program (Octopus etc.)
But this doesn't means that it's impossible to make a manual calculation ...
Now I shall try to explain the topic starting from giving you some brief notions ...

Tref is a flat rating temeperature based on the flat rated thrust used.
Tmax is a maximum certified temperature for takeoff calculated accordingly to the EGT limits (max thrust reduction of 25 %)

The optimization process (who gives Tflex) calculates the speeds which will produce the maximum takeoff weight or the maximum takeoff temperature for actual weight.
Tref and Tmax are clearly reported on the RTOW (Regulatory Takeoff Weight) charts which are calculated for a specific aircraft version and for a particular runway.

So Tref and Tmax are pre-calculated temperatures taken from the charts (1 Tref + Tmax for 1 chart for 1 aircraft version for 1 runway ).
By selecting the true OAT (Outside Air Temperature) on the RTOW chart, we obtain the MTOW and the max Vspeeds.
Doing it manually, this process would require a lot of time compared to the computer program calulation. Actually all data are calculated automatically by the computer and only a data crosscheck is required by the pilots.

There are more other things to add, but I linger to say this.

Regards

[mutt]

NOD,

Your engine is flat rated to ISA+15, this is your Tmin. Tmax is associated with the maximum rated thrust reduction limitation of 25%.

bertie187,

Google for "äirbus - getting to grips with aircraft performance". Or look in www.wingfiles.com


Mutt

[captain87]

I've added the percentage of reduction in my post !

Kind regards

[Charly]

25 % max reduction:

means between ISA + 41°C and ISA + 45°C

(depending on the types of engines your operator has with the A320family).

[bertie187]

THanks everyone for your input. Its all alot clearer now.

Thanks again

[118.50]

Do all UK operators use Computers (laptops) to calculate Flex and V Speeds ?

I thought that BMI use the charts etc