Inadequate bleed pressure? Options

[Charlie Reed]

Hi everyone,

Yesterday I had a flight all set up to fly from Stockholm to Madrid, but being Stockholm the temperature was a long way from tropical (although a little warmer than one may expect) at -3C, now having pushed back with APU running and ready for start, I was already aware of a lack of bleed air, having, in the gate been able to run only one air conditioning pack. So as I pushed back, I was not surprised to find my N2 only reached 18%, and so I shut the ignition down aware that this would cause a hot start. Now at this point my computer froze, so I had no opportunity to test other possibilities, but in this situation am I supposed to start in the gate with a high pressure starter unit or perhaps one of these in conjunction with APU bleed air?

Also, when I pushed back, a message on the alerting panel at the bottom of the overhead remained; "GROUND POWER DOOR OPEN" or something to that effect, so how do I get this to close?

Just to say, this is my first experience of cold weather ops. using the MadDog, I've spent the rest of my hours flying around southern Europe, so haven't has
anything like this before.

I look forward to hearing from you,
Thanks in advance,
Charlie Reed

[Olivier Moens]

Hi everyone,

Yesterday I had a flight all set up to fly from Stockholm to Madrid, but being Stockholm the temperature was a long way from tropical (although a little warmer than one may expect) at -3C, now having pushed back with APU running and ready for start, I was already aware of a lack of bleed air, having, in the gate been able to run only one air conditioning pack. So as I pushed back, I was not surprised to find my N2 only reached 18%, and so I shut the ignition down aware that this would cause a hot start. Now at this point my computer froze, so I had no opportunity to test other possibilities, but in this situation am I supposed to start in the gate with a high pressure starter unit or perhaps one of these in conjunction with APU bleed air?

Also, when I pushed back, a message on the alerting panel at the bottom of the overhead remained; "GROUND POWER DOOR OPEN" or something to that effect, so how do I get this to close?

Just to say, this is my first experience of cold weather ops. using the MadDog, I've spent the rest of my hours flying around southern Europe, so haven't has
anything like this before.

I look forward to hearing from you,
Thanks in advance,
Charlie Reed

Hi,

Can you confirm that the APU mode switch was on "norm" position and not "ECON"? .

Colder air temp should not have such influence on bleed air ,and even I would say that colder is better for bleed air and engine operation, including APU efficiency.
Normal air conditionning operation on APU is with only one pack open. Apu don't produce enough bleed air flow to work with both packs open if of course corresponding crossflow valves are open .
Don't forget to shut down the active pack before starting engine.

Don't worry about ground power door, the ground crew will close it without action from your part.

This post has been edited by Olivier Moens: 19/03/2011, 21:01

[VulcanB2]

Hi,

Bleed air pressure should be indicating >40 psi for start (instrument is next to start switches).

Prior to engine start:

* APU Mode: NORMAL
* APU Bleed Air: ON
* Air-Con Packs: BOTH OFF
* Thrust Levers: IDLE
* Fuel Valves: CUTOFF
* Cross-Bleed Valves: BOTH OPEN
* Bleed Air Pressure: CHECK (>40 psi)

Best regards,
Robin.

This post has been edited by VulcanB2: 07/04/2011, 4:16