LPC Laptops
A belated answer to post #858 by CONFiture:
YES, you can force the laptop into any approved take-off configuration.
It will provide the applicable figures, if a valid solution is available, or it will make clear that with the selected conditions, take-off is not possible.
Often airline managements will obligate the crews to use the OPTIMUM configuration output, because they fall for the word OPTIMUM.
In the instructions for the performance programs, you can read what the meaning is of the OPTIMUM CONFIG: it is the configuration, which will enable the highest lift capacity under the entered conditions, when using FULL THRUST.
The configuration that is thus determined will also be labelled OPTIMUM under conditions of reduced thrust.
The configuration that is labelled OPTIMUM often, but not always, also provides the highest lift capacity with reduced thrust. However, many times the assumed temperature that rolls out at lower flap settings is the same, or just 1 degree lower, than for the OPTIMUM CONFIG.
Often, the performance based maximum mass that can be lifted off a runway is far above the structural mass limit of the aircraft. Often, the differences between the Optimum and the other configurations amount to just a few hundred or a few thousand kilo’s, with all configuration providing performance far above the structural limit (FULL THRUST condition)
Yes, it is true that a higher performance limited mass gives you more margin in case of an engine failure, but seriously, a few hundred kilo’s difference on a total of more than 350 tonnes is not gonna give you much extra margin.
Realizing that the performance of the lower flap settings is hardly any less ON THE RUNWAY, it may be worthwhile to look at the performance once airborne. The climb performance with CONF 3 (an approved landing flap setting!) of course is abysmal, compared to a climb out with CONF 1.
The management bean counters should have a look at the amount of fuel that could be saved by the better climb performance! Than they would quickly reconsider their insistence on the use of laptop derived OPTIMUM CONFigurations.
Using minimum flap for take-off and only more flap when required for performance, would make it easier for crews to establish a mental reference of what is normal in terms of speeds for a certain mass (but yes, I know that also in fixed flap operations, errors are made).
P.S. This post is not a sneer at Airbus, their performance instructors properly explain the use of the laptop procedures, it is airline managements that order the improper use of the equipment.
Next point.
One important phrase from the ATSB preliminary report is about the use of the laptop(s). One laptop was used, the other was kept as spare, in case of breakdown of the first one. WRONG WRONG WRONG!
If pilot 1 closes the laptop and pilot 2 opens it again, to check the calculation, he will be staring at a screen with all the numbers as filled in by number 1! When glancing over numbers as a check, it is easy to overlook errors.
Pilot 2 should have autonomously filled in numbers on his own laptop and pilots 1 and 2 should have compared the outcome of their respective calculations. In that way, there would have been a comparison of independent calculations.
I do not know what the Emirates SOP’s were with respect to laptop use.