Turn air conditioning off prior to engine star

[Lemond23 0]

Whenever I fly in a 737, I observe the air conditioning is turned off prior to engine start. I imagine this has to do with the pneumatic/duct air pressure to have enough power for the engine start. But what is the real procedure in the overhead panel? What switches these pilots turn on or turn off?Thanks

[scandinavian13 5,192]

The procedure in the tutorial is the procedure used in the real world...

[vlanz 0]

packs off start them up! flaps 5 taxi checks!

[audiohavoc 24]

Pretty simple. Left and right packs off when starting the first engine. It is possible to start the other engine with the running engine's pack and engine bleed on.

[Lemond23 0]

Ok. When APU is on, if I turn both packs off, duct pressure goes down. So, I use to let the right pack on and the left pack off.

Edited February 6, 2012 by Lemond23

[VLJ510 16]

Ok. When APU is on, if I turn both packs off, duct pressure goes down. So, I use to let the right pack on and the left pack off.

It goes down when both packs are off as there is not a demand for bleed air, but when you start the start up process you will see the duct pressure comes back as now there is a engine start demand for bleed air.

[Fabo 213]

What Raven says is true. I will add that this is a bit different from both classics, where bleed air extraction was not demand-driven, and a crossbleed start, where you need to observe the pressure and adjust live engine thrust to have at least 40PSI.

[wisefox7524 9]

At SWA, I believe the procedure is as follows. Turn off the packs, and start the #2. When that is online, close the isolation vavle, and set the right pack to high. Then, start the #1. Once that is online, you can set the iso valve to auto, and then the packs as desired. Getting the right pack on is for pax comfort.

[vlanz 0]

You are correct ^^^

[scandinavian13 5,192]

At SWA, I believe the procedure is as follows. Turn off the packs, and start the #2. When that is online, close the isolation vavle, and set the right pack to high. Then, start the #1. Once that is online, you can set the iso valve to auto, and then the packs as desired. Getting the right pack on is for pax comfort.

You are correct ^^^

Good to know! I've been flying a lot of SWA since the NGX came out. Now I can sim more accurately.Thanks guys! Edited February 6, 2012 by scandinavian13

[vlanz 0]

You dont have to go to High on the #2 pack, Auto is fine. Also, I only start them like this when it is hot out to cool the passengers down. Otherwise I just turn the packs off, start the engines and congure the bleeds and packs on my before taxi flow.