在A350双引气失效程序中，有3中情况会需要下降到 FL100/MEA-MORA， 但只有最后一种情况中，也就是第一次引气自动复位不成功，下到 FL250之后 APU 引气不可用，最后下到 FL100/MEA-MORA，第二次引气自动复位也不成功时，才会要求 RAM AIR ON 以及 CAB FAN OFF。为什么在其他两种情况下不要求呢？
空客的第一次回复没有解释清楚，在第二次回复中承认 CASE 2 的情况下也应该要求 RAM AIR ON 以及 CAB FAN OFF，后续会修改程序。
在各种需要下降到 FL100/MEA-MORA 的程序中，有的要求 RAM AIR ON 以及 CAB FAN OFF，有的仅要求 RAM AIR ON，针对这一点，空客也做了回复。
另外在模拟机中这个 ECAM 警告会在执行程序的过程中可能会消失，这就是在自动复位，如果复位不成功，警告又会再次出现。
具体请参考 TechRequest 原文：
Q: AIR ENG 1+2 BLEED FAULT
There're several cases in which we have to descent to FL100/MEA-MORA. Why only for the last case it requires to use RAM AIR? Is it a layout mistake?
A:
Airbus confirms that the indentation of the procedural lines "RAM AIR…ON" and "CAB FANS…OFF" are correct.
The procedure lines "RAM AIR…ON" and "CAB FANS…OFF" will display on ECAM due to several conditions:
- Aircraft is not on ground
- Differential pressure < 2
- FL < 100/MEA-MORA
- INHIBITED if no bleed reset authorized or if at least one side has been recovered
- INHIBITED if APU bleed has been running at least once and is not failed.
From the conditions and layout of the ECAM procedure, the “RAM AIR…ON” and “CAB FANS…OFF” are indented in the FCOM.
Q_2:
Accodiong to INHIBITIED condition for "RAM AIR…ON" and "CAB FANS…OFF". CASE 1 is "no bleed reset authorized". However I can't understand the condition for CASE 2. There's the authorization, and no bleed recovered, and APU bleed has not been running.
And furthermore, what's the difference in trigger condition between both "RAM AIR…ON" and "CAB FANS…OFF" and only "RAM AIR…ON". For exemple, in AIR PACK 1+2 FAULT, in both condition, 2 PACKs are OFF, but only second condition wiil trigger CAB FAN OFF.
Another example, in ENG ALL ENGINES FAILURE, when BELOW 10000FT AGL, only require RAM AIR ON, without CAB FAN OFF.
A_2:
After further investigation, we confirm that in “CASE 2”, as illustrated in your mind map, further ECAM actions will trigger. When the aircraft reaches FL 100/MEA-MORA and the engine bleed is not recovered and the differential pressure is less than 2 PSI, the “RAM AIR…ON” and “CAB FANS…OFF” will trigger.Airbus confirms that the AIR ENG 1+2 BLEED FAULT procedure in A350 FCOM will be updated to reflect this change.
The purpose of the procedure line “CAB FANS…OFF” is to avoid unacceptable temperatures in case of“RAM AIR…ON”. When in very cold or very hot environment, the cabin temperatures could reach unacceptable level for crew and passengers if the cabin air is recirculated. However, in AIR PACK 1+2 FAULT, for the case of pack overheat, the “CAB FANS…OFF” is not applied because this could lead to a pack restart. For the case, of ALL ENGINE FAILURE, “CAB FANS…OFF” is not applied because the flight crew will have to land as soon as possible and will not be exposed to extreme temperatures for long periods.