This is the answer I received from AIRBUS, hope it's clear for everybody .
We reviewed your query and we would like to provide you with the following information:
As mentioned in the FCTM SI-090 “Supplementary Information – Landing Performance”, with the introduction of the In-Flight Landing Distances, it will no longer be possible to combine In-Flight failures (except for some identified cases) using the paper method.
Two main reasons explain this choice:
1. The first reason is that, in terms of figures, the conservatism in the publication of the combination of at least two failures from two different ATA systems becomes too high.
The purpose of the In-Flight Landing Distance tables in the QRH being to be applicable to all operators, whatever the altitude, temperature, weight, speed and wind conditions, it becomes difficult (if not impossible) to publish one single table covering these scenarios without introducing too much conservatism in the final results.
This aspect is all the more relevant than the conservatism has already been increased with the introduction, in the paper method, of additive corrections instead of multiplicative factors.
Knowing that in case of In-Flight failures, over-conservatism in the table might lead the flight crew to choose a diversion rather than landing at destination, we decided to cover in the QRH only some identified combinations for which the conservatism is reduced (e.g. DC BUS 1+2, loss of two brakes, loss of several pair of spoilers, dual hydraulic failure…)
2. The second reason is that, in terms of probability, the combination of at least two In-Flight failures from two different ATA systems is remote.
Historically, this scenario occurred only twice, and in both cases, it was extremely difficult for the flight crew to make an accurate assessment of the aircraft condition to be used for the computation (more than five failures were impacting the landing performance).
Nevertheless, although it is not possible to combine In-Flight failures using the paper method:
• It is still possible to obtain the corresponding performance using PEP or Flysmart with Airbus (in that case, the computation is run for some specific conditions that do not lead to the paper conservatism)
• It is possible, using the paper (and of course PEP or Flysmart), to combine a MEL item and an In-Flight failure, with both of them having an impact on the landing performance. In that case, for the paper solution, the landing factor given in the MEL must be applied to the In-Flight Landing Distance with failure.
We hope this satisfactorily responds to your request. We encourage you to provide us with your feedback using the questionnaire below, and we remain available for any additional information and assistance.
Best Regards,