B777 MEL 36-11-01 PRSOV
 

Hi Guys,

a quick question for the B777 genius.
Do you have any clue why applying the following MEL 36-11-01 PRSOV (Bleed not used) there is a penalisation in regards to the Performance Limited weight?

Let's assume the failure is on the right hand side.
The right hand bleed will be OFF (and locked closed) while the Left Bleed will be providing pressure only to the Left Pack, and the APU (ON as per the MEL) will be feeding air to the C1/C2 Hyd Demand Pump (Air Driven), so my understanding is that the right Pack will be not receiving air from any source as both L & R ISOLATION VALVES are OFF as per the MEL.

Hope to get some clues from you guys
thank you

Hello flapsupdown this is exactly the explanation i gave to myself this morning, and makes complete sense as i believe the in single pack operations the demand from that pack is way higher than the same pack in normal ops

flapsupdown

I don't specifically recall if the 777 is the same, but on the 767, with one engine bleed or pack INOP, the remaining engine/pack goes to "high flow" - and there is a higher debit to the max rating for high flow bleed.

I asked the same question and was given a thought provoking answer involving the TAC. Apparently if you have an engine failure just as you retract the gear, the hydraulic demand is so high that it requires the full output of the air demand pump - that in turn requires lots of air. And hence the reason AP U to Pack operations are prohibited. Not sure if it is true, but makes sense intuitively.