I have quite a few take offs in the NG and never had to use bleeds off take off yet. I have used flaps 25 and bump thrust but never the need yet for bleeds off. Its the last resort dispatch will use to get you off the ground. In fact I havent had any of my friends at our company use bleeds off yet. But I am sure there are some runways out there that require them.

Usually high and hot such as Denver at 95 degrees.

Isn't it done in certain situations to enable one pack on bleed instead of both to preserve thrust?

I have quite a few take offs in the NG and never had to use bleeds off take off yet. I have used flaps 25 and bump thrust but never the need yet for bleeds off. Its the last resort dispatch will use to get you off the ground. In fact I havent had any of my friends at our company use bleeds off yet. But I am sure there are some runways out there that require them.

Isn't it done in certain situations to enable one pack on bleed instead of both to preserve thrust?

The APU provides pressurization/air conditioning in this case and to the left pack only.

Isn't it done in certain situations to enable one pack on bleed instead of both to preserve thrust?

Don't get a "bleeds off" take off confused with "packs off". Packs off take off don't really exist. Engine bleeds take off do.

Actually packs off takeoff do exist, however not in 737s so you are correct. I have seen however packs off takeoffs being done in a 777-200ER in MMMX.

Actually packs off takeoff do exist, however not in 737s so you are correct. I have seen however packs off takeoffs being done in a 777-200ER in MMMX.

That's why we are in the 737 forum!!