Re: [Flightgear-devel] 747-400 cruise information
Andy Ross writes: > > From looking at the code > > Bless you, my brother. :) I promise I'll come back eventually. You'll > probably want to check those notes into the YASim README file too, > while you're at it. Already done. It could use more TLC, though, if you ever have a chance. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] 747-400 cruise information
David Megginson wrote: > From looking at the code Bless you, my brother. :) I promise I'll come back eventually. You'll probably want to check those notes into the YASim README file too, while you're at it. > I've discovered that YASim assumes a thrust-specific fuel > consumption of 0.8 by default, so there's your problem. In fact, > the following comment appears in Jet.cpp: I'm as surprised by that default as you are, actually. The A-4 was my first jet, so presumably I went with what I knew. The reason the 747 never got updated with a fixed TSFC is that its configuration predates the implementation of fuel consumption. :) Andy -- Andrew J. RossBeyond the OrdinaryPlausibility Productions Sole Proprietor Beneath the Infinite Hillsboro, OR Experience... the Plausible? ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] 747-400 cruise information
David Culp writes: > I asked a 747-400 pilot what was the fuel flow per engine at > cruise. He said about 6000 lb-per-hour. Assuming a TSFC of 0.5 > (I've seen 0.318 and 0.348 for the PW4060, but I don't trust these > numbers) that would mean each engine is developing 12000 pounds of > thrust. Therefore the total drag on the airplane at cruise is > 48000 pounds, and total fuel flow is 24000 pph. >From looking at the code, I've discovered that YASim assumes a thrust-specific fuel consumption of 0.8 by default, so there's your problem. In fact, the following comment appears in Jet.cpp: // Initialize parameters for an early-ish subsonic turbojet. More // recent turbofans will typically have a lower vMax, epr0, and // tsfc. You can tune these with attributes on the element in the YASim config file. For example, in $FG_ROOT/Aircraft-yasim/747.xml, you can change to and effectively double the 747's range (repeating for all four engines). Here are all of the attributes Andy uses for the element, together with defaults where I could figure them out: x y z mass thrust afterburner [0] rotate [0] n1-idle [55] n1-max [102] n2-idle [73] n2-max [103] tsfc [0.8] egt [1050] epr [3.0] exhaust-speed [800] Play with these, and you should get the engine of your dreams. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] 747-400 cruise information
Erik Hofman wrote: You can find the numbers here: http://www.bh.com/companions/034074152X/appendices/data-b/table-2/default.htm Oh, and by the way, here's the aircraft info: http://www.bh.com/companions/034074152X/appendices/data-a/table-3/table.htm Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] 747-400 cruise information
David Culp wrote: I asked a 747-400 pilot what was the fuel flow per engine at cruise. He said about 6000 lb-per-hour. Assuming a TSFC of 0.5 (I've seen 0.318 and 0.348 for the PW4060, but I don't trust these numbers) that would mean each engine is developing 12000 pounds of thrust. Therefore the total drag on the airplane at cruise is 48000 pounds, and total fuel flow is 24000 pph. These are very approximate numbers, but they might help locate the fuel burn problem with the Yasim 747 model. The pilot said he would take some notes on the next flight and email the numbers to me, so we'll have better data to go on (although I think we still have to guess the TSFC). You can find the numbers here:http://www.bh.com/companions/034074152X/appendices/data-b/table-2/default.htm Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] 747-400 cruise information
> I asked a 747-400 pilot what was the fuel flow per engine at cruise. He said > about 6000 lb-per-hour. Assuming a TSFC of 0.5 (I've seen 0.318 and 0.348 > for the PW4060, but I don't trust these numbers) that would mean each engine > is developing 12000 pounds of thrust. Therefore the total drag on the > airplane at cruise is 48000 pounds, and total fuel flow is 24000 pph. Well. The YaSim model seems to burn something like 2000-4000 GALLONS per hour (depending on altitude and weight) during normal cruise (>33000ft) per engine. Go figure. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] 747-400 cruise information
I asked a 747-400 pilot what was the fuel flow per engine at cruise. He said about 6000 lb-per-hour. Assuming a TSFC of 0.5 (I've seen 0.318 and 0.348 for the PW4060, but I don't trust these numbers) that would mean each engine is developing 12000 pounds of thrust. Therefore the total drag on the airplane at cruise is 48000 pounds, and total fuel flow is 24000 pph. These are very approximate numbers, but they might help locate the fuel burn problem with the Yasim 747 model. The pilot said he would take some notes on the next flight and email the numbers to me, so we'll have better data to go on (although I think we still have to guess the TSFC). Dave Culp ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
