Hi Uplinker,
If you don't mind, I will refrain from posting an image as this may prove to be copyright material, and I've no wish to infringe that...suffice to say I'll use the diagram located; FCOM-DSC-70-65-GENERAL as an example (of poor illustration in my opinion). The text relating to this image is included on the next few pages (which without the image to hand makes it kind of useless for referral without constant swiping back and forth, but eh - it's an iPad). Text in one page example is thus;
"ENGINE STABILITY
Two air bleed systems (station 2.5 of the LPC and stages 7th and 10th) provide greater compressor stability in the different flight phases.
- The LPC 2.5 bleed valve moves under FADEC control as a function of the low rotor speed, altitude and Mach and is dedicated to improve stall margin during starting, low power or transient operation. The failsafe position of this valve is open.
- The 7th and 10th stage bleed valves are normally closed for most engine operation but fully open for engine starting. Their failsafe position is open. Theses* valves are controlled by FADEC through FMU.
In the two cases, the air is vented to the fan air stream."
the (*) denotes inclusion of typographical error.
Now, okay - without the diagram it may be a tough ask to visualise. Even with the diagram it's tough (for me) to visualise what we are talking about. I appreciate that likely most will say....."this is merely nice to know, it bears little relevance to dealing with failures, use ECAM philosophy etc., etc." - and I would agree - however - If this is the case - then why the hell include it in a
pilot reference document? where and how can I use this information to effect a safe outcome in any instance of failure? I can understand an engineer using it in some scenarios - but a pilot? how? please if I am wrong, I would love to be enlightened here, as I cannot see it. And if Airbus include it in the
Flight Crew Operating Manual, then it must have relevance in some form for an operating pilot of said aircraft, or else it's just pointless and extraneous information that is not needed, and may confuse - which seems a silly thing to do if that is the case. For me the only thing of relevance is likely;
"ENGINE STABILITY
Two air bleed systems provide greater compressor stability in the different flight phases."
Would that not make more sense to a pilot? because there isn't much else here of use to me as a pilot? Airbus have even used mention of a "Station"....I'm sorry, but I get the feeling something is fundamentally wrong in the FCOM that other manufacturers seem able to address, and it seems on face value to want to confuse and mystify? and that's not good in any scenario and desirable outcome. Does this resonate with anyone else, or am I alone and an 'A'
?