Originally Posted by
sgs233a
I mean, I don't fly them (or any other transport category aircraft), but my interpretation is that they may have just dumbed it down. The question is; in a normal x-bleed start, presumably there wouldn't really be any other bleed consumers on... so the supply and demand side pressures, at least prior to initiating the start should be pretty close to the same, shouldn't they? If so, maybe they just dumbed it down a little - it may be sufficient to just look at supply side... Even if demand side is technically more correct.
The pack valves close when during the starting process, but there are other bleed consumers than the packs. Think of the water reservoir pressure, hydraulic reservoirs etc. Whatever the case, the bleed pressure indicated on the supplying engine is never equal to the receiving engine.
I always interpreted the procedure as start pressure in the receiving engine, just like in any other starting scenario. I agree the wording is ambiguous, but I think the intention is quite clear. Compare it with starting an engine with an air starter. No matter what the ground crew say, you will be looking at the air pressure in the receiving engine, not whatever is indicated on that tired leaky ASU!