B737 NG Questions.

[brown_eyes]

Just looking at the 737 CBT, it does not cover the questions below. Could somebody please assist.

1. If the APU is u/s on the NG. Do you need conditioned air, high pressure air and a GPU to get going or can a airstart machine provide the high pressure for the start and still be used to send air through the packs for air conditioning?
2. What sort of pressure would the source providing the conditioned air and the high pressure air for starting operate at?
3. What is the temperature range for the conditioned air?
4. If the APU was u/s which engine would you start first?
5. What is the minimum duct pressure required for starting?

Thanks in advance.

BE.

[Blinkz]

Can try and answer your questions:

1) You need an air start and a GPU. Technically the Air start can be used to power the packs but this isn't usually done as its very inefficient, in fact some of the air start units aren't designed to give high pressure air for that kind of continuous usage.

2) you need around 40 psi to start an engine. I don't know what the conditioned air pressure would be, not that high since the air is pre-condition and delivered straight into the mix manifold, it doesn't go through the packs.

3) its just normal conditioned air, so around 22degs.

4) you start no. 1 engine first as the GPU and air start are on the right hand side next to no. 2! You then disconnect the GPU and air start and push back. Once clear of anything behind you do a cross-bleed start from the started engine. You have to be a little careful with whats behind you as you have to increase thrust on no. 1 engine to around 35-40% to give the required pressure to start no. 2.

5) like I said you need around 40 psi to start an engine, the air start will not provide air for bother, when starting the engines from the APU you turn off the packs as well remember!

Hope that helps.

[TolTol]

You need an air start and a GPU

Do you really need a GPU? Why not a battery start?

[LeftHeadingNorth]

You can't start a 737 with battery start. Air start only...

[Blip]

TolTol.

You can start the B737 using just battery power rather than external AC power but it is rather messy as there are many systems that will not be powered up (such as the IRS's) until after the first engine is started (using external air source) and the generator is on the buses.

If you have external AC power available, much of the preflight preparation is identical right up to the point of starting engines.

[Capt Ted Crilly]

just a little tip

when starting on stand remember to put the number 1 gene on line before removing the ground power as this is not included in the checklist for some reason, this should be done before moving onto the engine crossbleed start.

blinkz, if memory serves me correct my NG only need 30psi to ensure engine start with a max of 60psi allowed. you will find the info in the supp procedures.

737 queen of the skies

hope this helps brown eyes,everything else blinkz says is spot on :ok:

[Blinkz]

Blip is right you CAN start it with just an air start and on battery power but as said its not a nice way to start it as its pretty messy!

Ted, yup your right its 30psi, not sure where I got 40 from!

[Capt Ted Crilly]

hey blinkz,

no worries thats why there is two of us at the pointy end.

ode to be flying the 73 again.:ok:

[TolTol]

Of course its much prettier to use a GPU, I just remembered reading about a battery start in the FCOM.;)