as the title says, can you?did they mean the engine packs? didn't know its possible.

The question is would you take off with the packs on? It's common practice if not procedure to take off with the packs off and turn them back on when climb thrust kicks in.

I'd argue it varies depending on the SOP, but yes, you certainly can depart without the packs on. If you have the MD-11, you'll note the takeoff ref page has a PACKS ON or PACKS OFF option. It ensures all of the engine thrust (or a larger proportion of it) is dedicated to getting you moving forward, instead of conditioning/pressurizing the aircraft.

Edited January 12, 201214 yr by scandinavian13

I can say the myriad of flights I have taken in my life, I can only remember the packs being on for one TO. It was at DEN on an A319 on the full-length 17R with maybe a 60% pax load. So yeah, I'm sure a super low N1/EPR. Really no reason to take them off-line, but certaintly not the norm.

The packs are heavy bleed users, to have more thrust the packs can be turned off for te take off.It depends from runway.If the runway has sufficient lenght to make an entire take off with all loads, te packs could be mantained on (so the pressure controllers will be able to do the pre-pressurization when throttles are advanced for take off)

The question is would you take off with the packs on? It's common practice if not procedure to take off with the packs off and turn them back on when climb thrust kicks in.

Standard in the MD-11 maybe, but not the 737.

To the OP - packs off actually gives you MORE thrust. It sounds like you're thinking the packs are a vital part of the engine's thrust-developing capability or something - not true, the bleed air load they place on the engine actually reduces thrust by a substantial amount. If the plane is heavy or the temperature and/or altitude is high, the packs usually get turned off for takeoff so that the engines develop more thrust.

Okay, there is continued confusion.Packs OFF = unpressurized.ENG Bleeds OFF = more thrust.You can do either, but why? If you want to takeoff with the ENG Bleeds OFF, it will give you more thrust. However, you will typically use the APU bleed for pressurization/air conditioning.Both procedures are in the supplemental section. You would only need to take off unpressurized if you needed the extra performance and the APU was INOP.

Hey , thanks all,i thoughts engine bleeds are pumping pressure for vital systems like APU AND ENGINES, and the packs are controlling on the pressurization and air conditioning, am i right here?

To the OP - packs off actually gives you MORE thrust. It sounds like you're thinking the packs are a vital part of the engine's thrust-developing capability or something - not true, the bleed air load they place on the engine actually reduces thrust by a substantial amount. If the plane is heavy or the temperature and/or altitude is high, the packs usually get turned off for takeoff so that the engines develop more thrust.

Ryan, out of curiosity. Is this simulated? Obviously the procedure is, but is performance changed if bleed air devices are used. ie Packs, de-ice

Edited January 12, 201214 yr by ZachLW

So the most correct procedure would be:- AC packs ON- Eng bleed OFF- APU ON with APU bleed ONI have always had the APU off the eng bleed and ac packs on but am starting to doubt wether this is correct?Rich

Sounds like I've being doing this wrong then as I always have the packs and bleeds on after start-up? Time to start reading the manuals but hoping this will all be covered in Tutorial #2 also.

Sounds like I've being doing this wrong then as I always have the packs and bleeds on after start-up? Time to start reading the manuals but hoping this will all be covered in Tutorial #2 also.

No, having them on is fine and normal procedure. Having them off allows for balanced field (Accelerate/decelerate distance) at shorter runways. I can't remember where the bleeds off takeoff procedure is covered off the top of my head. Just remember to do the after takeoff or else pressurization will not happen!

Edited January 12, 201214 yr by ZachLW

on the checklist written after start up: packs... on, one bleed.....on

Okay, there is continued confusion.

I was gonna say. You have more respected word, though, so thank you for chiming in.

Packs OFF = unpressurized.ENG Bleeds OFF = more thrust.You can do either, but why? If you want to takeoff with the ENG Bleeds OFF, it will give you more thrust. However, you will typically use the APU bleed for pressurization/air conditioning.Both procedures are in the supplemental section. You would only need to take off unpressurized if you needed the extra performance and the APU was INOP.

Can be quite uncomfortable for the ears, by the way.