Engine Start Problem

[flatdog]

Dear Pete,

I know that this is not directly a question about FSUIPC and quite understand if you do not have time to respond. I am using ProSim 737 with the default FSX 737-800 for my home cockpit. I have a registered version of FSUIPC which is at 4.747. I have a homemade overhead panel. If I start the APU and then (following the check list) start the engines everthing works perfectly (apart from the automatic operation of the fuel cutoff levers which is another matter). If I start the APU and then program the FMC etc (say five minutes) the engines will not start. The engine start valve shows as open in the lower EICAS, packs are off, duct pressure is 40 psi+ but N2 pressure stays at 0. There is a thread ongoing at ProSim about this but noone has come up with a solution and there are plenty of ProSim users who do not seen to have a problem. I have followed suggestions regarding how to create a default startup situation using the default Cessna etc. The only way to correct the problem is to reset the fight but this does reduce the realism somewhat. It is as if something is timing out. I know it is a longshot but I hoped that you might have come accross something similar or at least know which area to start troubleshooting.

Thank you,

Philip

[Pete Dowson]

If I start the APU and then (following the check list) start the engines everthing works perfectly (apart from the automatic operation of the fuel cutoff levers which is another matter).

Why are they operating automatically? You should have to move the switches.

If I start the APU and then program the FMC etc (say five minutes) the engines will not start. The engine start valve shows as open in the lower EICAS, packs are off, duct pressure is 40 psi+ but N2 pressure stays at 0. There is a thread ongoing at ProSim about this but noone has come up with a solution and there are plenty of ProSim users who do not seen to have a problem.

Sounds like there's something wrong in ProSim's logic. Are you losing duct pressure? After you start the APU you need to switch on the APU bleed to build up the air pressure needed to turn the jet rotors. Surely the instrumentation should show you what is wrong?

I know it is a longshot but I hoped that you might have come accross something similar or at least know which area to start troubleshooting.

No, sorry. I've really no idea. Only the ProSim author can really analyse this -- he knows what he's doing. I thought he simulated the systems flow quite accurately? I use PMsystems (or used to -- I've recently changed to Thomas Richter's 737NG system).

Regards

Pete

[flatdog]

Pete,

The fuel control swith problem is apparently a bug with FSX, the relevant post is here: http://prosim737.com/forum/viewtopic.php?f=13&t=783&hilit=fuel+cutoff There is also a post on the PM website here: http://www.projectmagenta.com/2011/06/cutoff/. I have yet to work out if it has any relevance to the ProSim problem.

The APU bleed is on, packs off, duct pressure is good, fuel valve opens but no N2 increase (but only if the a/c has been sitting at the gate for a while).

ProSim is a great piece of software and seems to be very accurate. I did a flight with a BA 747 Captain last weekend and he was stunned by level of detail. The developers are very responsive but these two issues have yet to be fixed.

Thank you for taking the time to reply.

Regards,

Philip

[Pete Dowson]

The fuel control swith problem is apparently a bug with FSX, the relevant post is here: http://prosim737.com...lit=fuel+cutoff There is also a post on the PM website here: http://www.projectma...2011/06/cutoff/.

Odd that I've never suffered from it. Perhaps it's the different starting technique I use, supported by FSUIPC. The engine starter controls in FSx have always been a bit iffy.

The PM reference you quote doesn't really describe the same problem, only the way to make sure the actual FS cutoff switches don't operate until all the right conditions for starting prevail -- because FS doesn't care about duct pressure and so on.

The APU bleed is on, packs off, duct pressure is good, fuel valve opens but no N2 increase (but only if the a/c has been sitting at the gate for a while).

It really does sound like ProSim is doing something odd over time. Can't you monitor the relevant conditions, see what is changing?

Regards

Pete

[flatdog]

OK, I will check what logging options are avaiable in ProSim.

Many thanks,

Philip