Hello; I have a couple questions regarding the bleeds off takeoff procedure. I've seen it in real life here in Mexico City when the plane is heavy, we suffer from hot temperatures and high airport elevation (7320 ft aprox). How do you determine if a bleeds off is required and what is achieved out of this ? Is this simulated in our PMDG aircraft ? Could some one be kind enough to provide the procedure for this... Thank You ! SincerelyJesus H

Usually it is a work of performance engineers. I dispatch 737, 757, 767 and 777 every day and it comes with the flight plan. Sometime we turn bleeds off, some times we don't. We play with the system until we get best payload and sometimes bleeds off takeoff is not a matter. Dispatch system determines whether bleeds off on take off helps or not. It not always helps. Turning bleeds off may kill other aircraft performance so you have to be careful doing that and you have to really understand what you are doing. Especially in airports like Denver, runways are very long but the field elevations is almost 5400 ft and high temperatures. It is a combinations of many things to consider if bleeds off takeoff will help or not. You have to know airplanes performance so deep to understand and to make a right a decision if it helps at all. More over I doubt you will be able to figure out how much credit you will get turning bleeds off. It may give you 3000 lbs of additional payload or just a 100 lbs. System take into considerations very many things, RW length, temps, obstacle clearance, winds, NOTAMS, RW shift and so on. Even if PMDG simulated bleeds off take off, it will not be accurate. There is a procedure for bleeds off take off in PMDG manual. I have tried it few times but I did not find the difference. Ask PMDG. In real world our pilots do not turn bleed off unless they talk to dispatcher and load planner because they will not be able to figure out how much credit they will get. At least this is how it works in our major airline. Good luck.

I believe you can find the procedures in the FCOM Vol 1. Supplementary Procedures and the necessary performance adjustments on Page 614 PI.20.16

I pulled this from another thread.

for 'no engine bleed air TO (or approach) with APU' just remember the 'C'-pattern:- R pack auto- isolation valve closed- L pack auto- L bleed air off (to avoid backpressuring the apu)- Apu bleed on- R bleed air off (on pack is enough) after TO just do it the other way round (but let the cabin rate stabilize before turning L pack on again)!regards,christopher volle

Thank's guys, I'll take a look at the manuals. Cheers !!