Air starter no pressure

[30K 72]

Hi all,

I simulated an APU bleed inop event. So I connected the air starter, to get some air, via the fs actions menu and got no duct pressure. 

Config:

PACKS both OFF, Isolation valve OPEN.

Something I missed?

 

 

Edited August 20, 2018 by 30K

[downscc 1,327]

FCOM SP.7.5  the first thing I noticed is your APU bleed is open. Perhaps that is where your air is going?

[30K 72]

The screenshot was taken before having a look into the FCOM to be sure I do it right. 

I closed it later on. I actually tried every combination and I never got the pressure.

[30K 72]

Okay, I restarted the sim and tried it again and it worked. I have no clue what exactly was the problem.

Btw. it worked with APU bleed on and off.

[MarkJHarris 128]

There's a non return valve and a pressure controlling valve also in the APU bleed duct. This is why the APU bleed switch position doesn't affect plenum pressure.

On the -4/8/900 these is a large mix manifold under the fuselage. The bottom of this manifold is where the ground conditioned air flap valve is positioned. the high pressure air also goes into the ducts. As long as the pack valve switches are off, there should be enough pressure to start the engines. Normally the checklists call for starting the No2 engine from Air Starter unit, then disconnect it. Connect generator, disconnect GPU, and finally push onto centreline to prepare for crossbleed start of No1. 

It's frankly a pain in the word not allowed- be nice to your APU!  At 55'c degrees in deepest rural Turkey.... it is essential to keep your cool in every way! 

[30K 72]

14 hours ago, MarkJHarris said:

There's a non return valve and a pressure controlling valve also in the APU bleed duct. This is why the APU bleed switch position doesn't affect plenum pressure.

On the -4/8/900 these is a large mix manifold under the fuselage. The bottom of this manifold is where the ground conditioned air flap valve is positioned. the high pressure air also goes into the ducts. As long as the pack valve switches are off, there should be enough pressure to start the engines. Normally the checklists call for starting the No2 engine from Air Starter unit, then disconnect it. Connect generator, disconnect GPU, and finally push onto centreline to prepare for crossbleed start of No1. 

It's frankly a pain in the word not allowed- be nice to your APU!  At 55'c degrees in deepest rural Turkey.... it is essential to keep your cool in every way! 

Thanks, I asked one of the tech guys at our airport. Said the same.

When I am a wing walker for a cross bleed start and required air starter, we use the start sequence 2 then 1. Depends on the position though.