Start Up Question

[soleverris]

Hey Everyone,

 

Got a question on the start up procedure....I have completed the start up training scenario several times now (writing down the step by step directions) and always hit something I don't believe is correct. After the left engine starts it's spin up, I get a master caution and the APU gen light lights up on the caution annunciation panel. I must be doing something wrong because I doubt that alarm is supposed to ring the whole time the left engine spins up then the right engine. After that you check speed brakes, elevator, rudder, etc are tested. Finally you shut off the apu generator and the apu start silencing the master caution. I have played through the training double checking the steps I wrote down and don't see any mistakes. So is the training start up wrong or does the master caution stay on that whole time? Any help is appreciated. :helpsmilie:

[EightyDuce]

I've only been playing this game for a couple of days, but from what I understand once the left engine spins up you no longer need the APU gen since at that point your left engine is providing the power via generator. Alternatively, you can just hit the the master caution button to manually silence the warning.

 

However, as I said, I've only been playing for a few days so I may very well be off base here.

[Snoopy]

You can silence the master caution by pressing it. Check out the link in my sig for checklists/guides bases on real world A-10 training/checklists.

[soleverris]

Thanks for the quick response I will try that as soon as I finish typing this. The only reason I was leaving the apu gen switch on until the right engine spun up was that's what the training mission said to do lol. I thought maybe it had to be on to start the engine. Thanks for the help.

[Snoopy]

You need to leave it on as long as the APU is running. Just press the master caution and the light and horn will turn off. What it is telling you is the APU generator is no longer supplying power.

[soleverris]

Paulrkiii awesome checklists :thumbup: Thanks for the link and all the work you did on those.

[Elwin]

What I do is I leave engine generators off until both engines are up and running (after engine startup cycle light goes off), then I switch them both on and immediately turn off APU GEN and APU itself. This way the warning beeps only for about 2 seconds and I don't have to mute it manually.

 

Reason why I do it this way is following: I have turned on left engine and when the right engine began to start up, I have engaged left engine generator and turned off APU generator. The right engine then couldn't get started properly, it was trying to start but never got past 20% RPM. After several right engine restarts, I engaged APU GEN again and then it started normally.

 

So I figured one engine generator does not provide sufficient power to crank up second engine, and to avoid listening to the pesky master caution I simply switch the generators when both engines are already running :-)

[Eddie]

What I do is I leave engine generators off until both engines are up and running (after engine startup cycle light goes off), then I switch them both on and immediately turn off APU GEN and APU itself. This way the warning beeps only for about 2 seconds and I don't have to mute it manually.

 

Reason why I do it this way is following: I have turned on left engine and when the right engine began to start up, I have engaged left engine generator and turned off APU generator. The right engine then couldn't get started properly, it was trying to start but never got past 20% RPM. After several right engine restarts, I engaged APU GEN again and then it started normally.

 

So I figured one engine generator does not provide sufficient power to crank up second engine, and to avoid listening to the pesky master caution I simply switch the generators when both engines are already running :-)

 

Engine generators should be enable before you start the engines (or even the APU) as part of your cockpit check, they will not actually start working until the relevant engine is up to speed. And as said previously, the APU Gen stays on until just before APU shutdown. The APU generator has no function in starting the engines, it is only providing electrical power, engines are started via APU bleed air.

[Elwin]

Still, I was not able to start the engine until after I turned APU GEN on again. Then it worked. This has only happened to me once, but I will test it tonight. Maybe it relates to something else.

[Kaiza]

The APU generator has no function in starting the engines, it is only providing electrical power, engines are started via APU bleed air.

 

The APU does provide power to the ignitors which start the engines though.

 

Still, I was not able to start the engine until after I turned APU GEN on again. Then it worked. This has only happened to me once, but I will test it tonight. Maybe it relates to something else.

 

This seems a little strange. Perhaps your engine generators weren't on. From the bus diagram in the manual, it appears that if either engine driven generator is operating it will power the ignitors. If the engine sits on starter RPM like you describe its probably not getting either fuel or fire.

[Elwin]

I also remember that one engine generator should be enough to power the whole aircraft.

 

Well after a quick search I suppose it was missing the bleed air from APU...

[Eddie]

The APU does provide power to the ignitors which start the engines though.

 

The ignitors are on the AC Essential BUS which is supplied by either engine generators, APU generator or the battery via the inverters. The only electrical source required to start the engines is the battery.

[ivanwfr]

About APU helping (to say the least) to start right engine, here is a quote of Flight Manuel (P437):

 

Figure 318. Right Engine Start

1. Once the Left engine has stabilized, move the Right throttle from the OFF to the IDLE position to start that engine.

The APU bleed air will also be used to start the second engine and not bleed air from the first engine as you might assume

.

 

So, it's not that it helps, it is required.

[sobek]

Yes, one engine must run at least at 85% (?) core speed to be able to provide enough bleed air to start the second engine. With only one engine idling, it is not possible to bleed enough air to start the second engine.

[Eddie]

About APU helping (to say the least) to start right engine, here is a quote of Flight Manuel (P437):

Figure 318. Right Engine Start

1. Once the Left engine has stabilized, move the Right throttle from the OFF to the IDLE position to start that engine.

The APU bleed air will also be used to start the second engine and not bleed air from the first engine as you might assume

.

So, it's not that it helps, it is required.

 

Unless the running engine's Core RPM is over 85%, in which case there will be enough bleed air to start the second engine.

[ivanwfr]

And why should we do that ?

 

Main engine at 85% just to blow some air and has you hanging on the brakes to preserve EGI Alignment ?

 

But, maybe I'm missing something, and there are some good reasons why not simply use the right tool for the task at hand?

 

It's not that I need to state the obvious, it's rather that it's precisely with this kind of argumentation that things that make sense get in place.

[EtherealN]

In-flight engine restart is one case.

[Eddie]

And why should we do that ?

 

Main engine at 85% just to blow some air and has you hanging on the brakes to preserve EGI Alignment ?

 

But, maybe I'm missing something, and there are some good reasons why not simply use the right tool for the task at hand?

 

It's not that I need to state the obvious, it's rather that it's precisely with this kind of argumentation that things that make sense get in place.

 

For ground start there is no reason whatsoever not to use the APU. However you said that the APU is required to start the right (second using the normal start procedure) engine. As you can see, procedures aside, this is not the case.

 

And no one is arguing. So a bit confused by that comment.

[Elwin]

Again I learned something new, this time about bleed air from engines and APU, thanks.

[ivanwfr]

Well, maybe argumentation was the wrong word (i'm french so arguing, argument, argumentation may collide in my head):

 

Agument:

An exchange of diverging or opposite views, typically a heated or angry one.

 

Argumentation:

The action or process of reasoning systematically in support of an idea, action, or theory.

 

Topic being "Start Up Question", emergency procedures could be considered as side notes.

 

So, I take using APU while starting both engine and provide electrical power until you think you can shut it down safely is good enough as a simple understanding of what to do as a routine.

 

Engine restart is a stressful situation where any trick may change the issue when you know how and when to use one. And I would not consider these procedures from the same point of view where simple is often best.