JAR-EASA Alternate Planning

[AFD]

Hi bio161, let me correct your writing as your good colleague is anything but me :-)

What i told you is that although we do fly cost index 0,which is equivalent to the best/max range speed as per Airbus "Getting to grips with performance", my company is planning the fuel burn to the alternate on the OFP, with the LRC(long range cruise) speed, not with the normal cruise cost index.Therefore the margin is even higher than the normal cruise,as normally we fly the aircraft from departure aerodrome to destination with a range of cost index which is lower than the LRC.
According to Airbus A320 QRH a long range cruise cost index is 50 for a A319 and 40 for a A320.

I would like you to consider the following scenario.
Let's assume for a while that your company plans your OFP from destination to alternate with the best/max range (cost index 0), how would you be able to determine that particular speed in such a case of a double FMGC failure?

You very well know that the best range speed is very variable,and dependant on factors like temperature,weight,wind etc.
In this situation you will be forced to revert to paper tables,like the one you can find in the QRH/FCOM, and consequently,unless your company provides you with different tables,you will need to consult one of the following tables to determine the speed to go to the alternate:

-FCOM PER-FPL-FLP-ALN-20
"Alternate Planning from Destination to Alternate Airport" based on:

‐ Go-around: 80 kg or 180 lb
‐ Climb profile: 250 kt/300 kt/M .78
‐ Long range speed
‐ Descent profile: M .78/300 kt/250 kt
‐ Approach and landing at alternate airport: 60 kg or 140 lb (4 min)
‐ ISA
‐ CG = 33 %
‐ Normal air conditioning
‐ Anti ice OFF

-QRH FPE-AEO 4/4
"QUICK DETERMINATION TABLE OF ALTERNATE FLIGHT PLANNING" based on Long Range Descent.

In conclusion if you have the OFP calculated with Cost Index 0 (best/max range) and then you fly according to this tables, you will burn more fuel than what was planned and loaded for that particular flight.