All Documents | PDF version

Chapter 16
Pneumatic

 16.1 Dual bleed failure

16.1 Dual bleed failure

The historical failure case where supplying two packs from one bleed would overload it and cause it to fail appears to have been resolved. Furthermore, recent airframes have four new ecam procedures associated with dual bleed failure, the variants based on whether neither, either or both bleeds have failed due to a wing or pylon leak on its respective side. The ecams all hand off to a new qrh paper procedure if no successful reset is achieved. Older airframes make do with just the qrh procedure.

Whilst the procedures look complex, the underlying philosophy is fairly simple:

In line with this philosophy, both the ecam and qrh procedures start by shutting the cross bleed and turning off the wing anti-ice. The ecam procedures each then attempt an immediate recovery of any recoverable bleed by cycling the bleed off then on. The qrh attempts an immediate recovery only in the case that both bleeds are potentially recoverable.

If no bleeds are recovered, the bleeds are all turned off and a descent to fl100/mfa is initiated. At this point, the ecam procedures join the qrh procedure.

During the descent the apu is started. If the left hand side of the pneumatic system is available, at attempt to use the apu bleed for pressurisation is made at fl200. If this is successful, the descent is stopped at fl200 and a further attempt is made to reset the engine bleeds.

If apu cannot be used for pressurisation descent must be continued. When level at fl100/mfa, a final attempt is made to restore any available engine bleeds. If unsuccessful, the flight is completed with ram air.

[ air 1+2 bleed fault (left(right) leak (and right leak)),
qrh aep.air, fcom pro.aep.air ]