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Engine Start


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7 replies to this topic

#1 Inactive Member_jshyluk_***

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Posted 11 September 2008 - 01:13 PM

@ loop-n-roll:Yes. What you are describing makes the 737 seem like a golf cart, where you press the pedal, the engine starts and the thing goes. The real world 737 is nothing at all like that. There's a starter and there's fuel intake for the engine. If you open the cut-offs too soon, you dump fuel into an unstarted engine, which results in a condition similar to engine flooding, except with the possibility of more explosions. The real procedure has you spool up the engines one at a time with the starter and then open the cut-off at N2=80 (I think? Can't recall for sure.) Also, computerized starters can help the pilot time this procedure.FSX doesn't easily model engine wear, so it allows you to start in a variety of unhealthy ways. Check out the Learning Center in FSX to find out more about the 737. It has a pretty good start-up and shut-down checklist in the kneeboard, too.If you want to look for a more realistic sequence, you can try the PMDG 737, but that works for FS9, and is not fully functional in FSX. If you can find a manual for that aircraft, it's very instructive.Beyond that, you can search the AVSIM library for Boeing 737 checklists. Again, you will find more stuff in the FS9 area, but the checklists are just text files,and make interesting technical reading. As for the effect of shutting down and starting the FSX B737 engines, I am pretty sure that if you shut off the engines, let them spool all the way down, and then shut off the battery, then you will need to use the ignition switches to re-start the engines.Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

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#2 Gypsy Baron

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Posted 11 September 2008 - 12:40 PM

>Thank you both for the explanation. I can now get the default>737 started and airborne. However, the engine starts as soon>as I open the bleed valves and shuts down again if I close>them. And it seems opening these valves is all that's needed>to start the engines and keep them running. I assume this is a>shortcoming of the default plane and that more realism demands>another, more complex, model. Am I right? The default B737-800 engine start XML code is what needs to be changed to get a more realistic engine start. I changed mine way back at the beginning of my FSX experience when I was changing the code for many of my FS9 imports that would not start because of changes in the way FSX handled the starter 'toggle' event. The XML changes involved creating at least one new 'gauge' to reset the starter code once the engines spooled up as well as changes to the starter logic, a couple of new bitmaps for new starter switches, etc. Enough changes, made long ago, to make it impractical for me to describe then in detail or post the changes. I believe I went through a similar exercise with the A321 as well. Paul

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#3 loop_n_roll

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Posted 11 September 2008 - 06:31 AM

Thank you both for the explanation. I can now get the default 737 started and airborne. However, the engine starts as soon as I open the bleed valves and shuts down again if I close them. And it seems opening these valves is all that's needed to start the engines and keep them running. I assume this is a shortcoming of the default plane and that more realism demands another, more complex, model. Am I right?

#4 Inactive Member_tcable_***

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Posted 10 September 2008 - 01:03 PM

I'm not really familiar with the default- but here's the spiel that's grounded in reality.First, you are shutting down properly- you are cutting off the fuel to the engines (the correct shutdown) The engines under normal conditions do not require continuous ignition, its just a jet of flame in the combustors.You require four things to start a jet engine, Fuel, Air, Rotation and Ignition. Fuel comes for the fuel tanks, air can come from the apu bleed source or an external high pressure source (a start cart or other ground air. Even a bottle of compressed air is sufficient providing it meets the specs for engine start- volume and pressure). Ignition comes for having electricity on the airplane and the ignitors energized. In modern jets this is automatic when you engage the starter.On the 737-800, Start the APU- takes a minute or 2. Once online make sure the apu bleed valve is open (probably not modeled on the default!) and that the generator is online and feeding the busses.Now you have air and power. Check that you have fuel sufficient for flight. IRL this is done well before now, but this is a game. So we have all 3 sources for the engines, now we need to bring them together.Turn on the fuel pumps for all tanks that have fuel in them- The APU feeds from the left wing tank, and automatically starts a fuel pump to feed itself even if you do not have the pumps on (cool, huh?) Verify that the APU is providing enough duct pressure. I forget the figure, 35 PSI- I think. Turn off the packs (the pressurization and air conditioning) so that they are not using the bleed air. Then turn the start switch on the proper engine to start and release. Once the engine spools up to 15% N1, open the fuel cutoff switch to run. This will open 2 valves- the wing valve and spar valve to allow fuel into the engine. Once stable at idle, repeat the start process (from start switch on down) in order to start the second engine.With both engines online, make sure the engine generators, engine bleed valves and packs are on. turn off the apu. After a cooldown period, it will shutdown- don;t be surprised if this takes 2-3 minutes before it shuts down.Time to taxi out and fly :)It's a simplistic version of the engine start sequence, and generally this process is similar for all modern jets- even Airbus or biz jets. The 747 is very similar, but has pull to start switches and you flip on the fuel cutoff immediately and let the computer sequence the start. The only difference in a small jet is that some small jets use either an electric motor to start the engine or even accumulated hydraulic pressure instead of air pressure..Have fun!Tim

#5 Inactive Member_jshyluk_***

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Posted 10 September 2008 - 12:52 PM

It's been a long time since I have played with the default 747, so I don't think there's one "right" way to start it. What I mean is, that the start up sequence is abstract compared to the real-world procedure, so you have a lot of leeway in how you do it.Apart from what other checks you want to do:1)Make sure the parking brake is SET (this doesn't affect your engines, but it will stop your aircraft from rolling).2)Turn the Battery switch ON3)OPEN the fuel cut-offs (the small levers just below the throttles, labelled 1 & 2)3) Engine start switch IGNL to start #1, then to IGNR to start #2. Re-ecenter the switch to BOTH after the N2 numbers stabilize on the engine display in your dashboard display.That's about it, although its a far cry from how to start a real 737.The other switches are for show, but you can include them in your start-up sequence.To shut down your FSX 737, just cut off your fuel using the switches in Step 2, and turn off the battery.If you've loaded in another aircraft in a previous session, you might find that your fuel cut-offs and/or battery don't work properly. Just jiggle the switches and it should work.If all else fails, CRTL-E.Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

#6 loop_n_roll

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Posted 10 September 2008 - 06:46 AM

Would someone tell me the engine start sequence for the default 737? Once I shut the engines down by pulling back the mixture lever (probably not the right way to do this either) I can't seem to find the correct way of starting up. Help is appreciated.

#7 Inactive Member_jshyluk_***

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Posted 15 September 2008 - 05:59 PM

Definitely, Werner Schott is the guru of sim pilot checklists! You can't go wrong with his stuff. This looks like an interesting link.I remember adapting some of his checklists for my own use into Flight Sim Commander. The only downside was that I felt I had to move the battery checks around because the MSFS battery dies very quickly without a generator to back it up.Jeff ShylukAssistant Managing EditorSenior Staff ReviewerAVSIM

#8 loop_n_roll

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Posted 13 September 2008 - 06:38 AM

Thanks to all. I've found starting with the engines off is more fun and after all, that's what it's about. I found these which also help.http://freechecklist...mchecklists.asp





   
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