SPHL:
I'll revisit this point. But while I'm away, could someone repeat the estimated temperature of the bleed air in the ducts.
Good question. Except during ground starting only (see below) the bleed air is at ambient temperature, where the ducts are outside of the engine fire zones. Inside the engine fire zones (where there are hot gas leak detectors, firewire and extinguishers) the air inside the ducts can reach 500C and 288psi at max engine rpm. I suggest that this is not unusual in any modern aircraft where air is ducted to start the engines.
During ground starts, when we have to open the crossfeed duct, the engines are all kept below 80% by the pilots, which prevents the bleed air reaching more than 150C, which is well below the auto-ignition point of both hyd fluid and fuel.
Regarding the flash point: OK, I was approx 7 degrees out, but I don't normally have my Def Stan book of fuels at home. My thanks to Phil Rigger for the accurate info to keep us on a factual path.
I'm looking forward to reading SPHL's views on the flash point of kerosene vapours.
Regards
Ed Sett