APU won't start ?

[Stiganovski 0]

Hi guys,

 

Here is the setup:

737-BBJ (Or any 737 for that matter)

Cold and dark

No ground power start - APU start

Follow the startup sequence to the letter and the APU refuses to start. I get the "Low oil pressure" lamp but no start.

If I use fs2crew the APU still doesn't start.

So, switch to a ground power start. All fine except...

Engine 1 and 2 generators don't generate any power :s

So, cross bleed start the APU and have to use the APU gen to run the plane.

 

So, before I uninstall it all and reinstall is there anything I can do to test anything further out?

 

Cheers,

Craig

[Spin737 102]

Screen caps will help.

[Stiganovski 0]

Gotta love posting, it's the guaranteed way to fix it!

Decided to give it one more go and make more notes and this time it worked fine :s

Very odd.

If I can get it to replicate again I'll post some grabs up.

 

Cheers,

Craig

[Steven_Caffey 23]

Well, the engine generators won't provide power if the engines are not running. That's how they work. As for the APU, if it won't start check in the CDU for failures. I have had a problem where loading a certain panel state causes the APU to fault.

[davierosoft 13]

There is some confusion about how the APU works, it is not possible to cross bleed start it as the starter for APU is electrical.

To connect AC power you need either engines or APU running AND switch the generator/s online, there is no automatic function for them.

The APU switch is a 3 position switch, to turn the APU you must click twice from OFF as it will firstly go to On, and then you need to click it again to move to the START position.

Remember that you need fuel in the left tank OR you need the left fuel system pressurized (one of the right pump plus crossfeed open and aircraft already powered)

Procedure will be:

Battery on,

stby power on

apu starter to ON

apu starter to START for 1 second

wait to see if starter engages (select BATT on the DC meters and see if current is drained, caution, this is valid only from cold and dark), EGT must increase.

Wait until EGT stabilize

wait the blue light APU GEN OFF BUS to become bright.

Switch both APU gen switches to ON position to power the aircraft with APU

Switch one left pump to help feeding the APU or use one of the right pumps plus crossfeed

...

[rgamurot 1]

The fact that you can't start it even with FS2Crew seems strange. Make sure for FS2Crew you start with the cold and dark panel save before you hit the preflight actions. As far as a manual start, as Andrea said above, it's a three way switch. You should get a low oil pressure light and then about 5 to 15 seconds later (depends on OAT) the EGT should start to rise.

 

Also...

Here is the setup:

737-BBJ (Or any 737 for that matter)

Are you sure this is the PMDG 737? The BBJ won't be released till after the 777.

[Stiganovski 0]

Steve - Sorry wasn't very clear, the engines were running. Switched generators on and no power. It would trigger the A/P master warning. Switch the APU gen on and all was well again.

 

Andrea - That's what I thought was so strange. With the engines already running the APU would start. I know that the circuit for the APU is seperate to the engines, again, I was innaccurate in my description sorry.

Yes, I followed the checklist precisely and it still wouldn't start. I am yet to replicate the issue again. It happened for a period of a few days and approx 10 attempts. After a reboot (the PC basically sleeps so no reboot for a while)and another try the other evening it now works fine. I blame zombies.

 

Ryan - Yep very strange. Again though, since the reboot all is well in the land of milk and avgas.

 

I am putting down to something hanging within Windows causing the fault.

It's nothing life threatening, I fly for a living but nothing like these birds. It's mainly to get a slight glimpse into the procedural aspect etc as I'll have to leave the military one day lol

 

Thanks for the feedback guys. Very much appreciated.

 

Cheers,

Craig

[davierosoft 13]

Check for failures, APU will not start if started too early (just few minutes) after the last APU shut down, also check for other failures.

[lowlevel 0]

Here is the setup:

737-BBJ (Or any 737 for that matter)

 

I am pretty sure there is no BBJ version of the PMDG product (yet). Are you sure you did not messed iFly with PMDG?

[falcon999 24]

There is some confusion about how the APU works, it is not possible to cross bleed start it as the starter for APU is electrical.

To connect AC power you need either engines or APU running AND switch the generator/s online, there is no automatic function for them.

The APU switch is a 3 position switch, to turn the APU you must click twice from OFF as it will firstly go to On, and then you need to click it again to move to the START position.

Remember that you need fuel in the left tank OR you need the left fuel system pressurized (one of the right pump plus crossfeed open and aircraft already powered)

Procedure will be:

Battery on,

stby power on

apu starter to ON

apu starter to START for 1 second

wait to see if starter engages (select BATT on the DC meters and see if current is drained, caution, this is valid only from cold and dark), EGT must increase.

Wait until EGT stabilize

wait the blue light APU GEN OFF BUS to become bright.

Switch both APU gen switches to ON position to power the aircraft with APU

Switch one left pump to help feeding the APU or use one of the right pumps plus crossfeed

...

 

I have seen similar flaky issues like this when switching from one type of NGX to another during the same flight session (big no no). Could this have been it?

[davierosoft 13]

I have seen similar flaky issues like this when switching from one type of NGX to another during the same flight session (big no no). Could this have been it?

It is possible that sometimes switching the plane, loading the other in C&D when the other was powered could give an overtemperature start and this will give a missed start.

I never had these issues so I cannot help more than giving tips.

1) follow correct procedures for starting

2) check panel state, some issues start from an old, or damaged, panel state, using another one could help.