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Guest AndrewW

FDE Thrust Decrease with Altitude

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Can someone help me with it?I'm working on a Concorde FDE with AirEd, but I've got a problem with the thrust decrease that happens with altitude. The Olympus 593 produces 31,350 lbs dry, and 37,080 with reheat at SL. The thing is that at around FL500 until FL600 they produce 11,000 to 10,000 lbs. But on FS I'm getting 16,150 lbs at FL510 and 11,769 at FL575. This is causing a SFC of 0,914 and this value is constant between FL490 until FL575 with 100% of throttle. This could mean that the thrust decrease is attached to fuel consumption. The SFC should be 1,15 on Concorde at Mach 2.This excess of power creates a need for big drag at Mach 2 to simulate the Concorde's cruise climb, and consequently changes the L/D ratio, that should be 7,5 and is between 4,5 and 5,1.Are these settings at sections 1506/1507? For an example, dividing 31,350 by 3.676 (the value at Table 1506 for Mach 2.00 and "Turbine Thrust Factor vs N1" at 95 - the N1 I'm getting is 93,6%) I have 8,529.3, but is this calculation correct? What would be the "Turbine Thrust Factor"?L

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>Can someone help me with it? >>I'm working on a Concorde FDE with AirEd, but I've got a >problem with the thrust decrease that happens with altitude. >The Olympus 593 produces 31,350 lbs dry, and 37,080 with >reheat at SL. The thing is that at around FL500 until FL600 >they produce 11,000 to 10,000 lbs. But on FS I'm getting >16,150 lbs at FL510 and 11,769 at FL575. This is causing a >SFC of 0,914 and this value is constant between FL490 until >FL575 with 100% of throttle. This could mean that the thrust >decrease is attached to fuel consumption. The SFC should be >1,15 on Concorde at Mach 2. >Are these settings at sections 1506/1507? For an example, >dividing 31,350 by 3.676 (the value at Table 1506 for Mach >2.00 and "Turbine Thrust Factor vs N1" at 95 - the N1 I'm >getting is 93,6%) I have 8,529.3, but is this calculation >correct? What would be the "Turbine Thrust Factor"? >>>L

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Man!!!Wow! I'm impressed!Yes, I would like to receive this corrected engine model made by Ron Freimuth, as the MoIs too.What is SS? I didn't understand all the codes on the table above, and how you found the thrust. Guess you have used some formulas?The ones I did understand was FL, MN, Thrust and Error. CN1 is the Corrected N1? T/1507 is soemthing about the Air section 1507?I entered the site and downloaded all the material. On it there was something about AirUpdate. I searched for it and found http://www.mudpond.us/ and they have a lot of more info. I'll read it all and try to understand more about the AIRs.Well, please contact me on the private message system so I can send you my email.Thanks a lot,L

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Hi,may be you did not see my notes in the airfile decode section:at http://perso.wanadoo.fr/hsors/FS_Soft/fsdocs.htmlIan Kerr papers 1. Turbojets notes 2. FAQ from airfile decoding forum (updated) 3. Jet engine thrust prediction SS You want item 1 as this is my current explanation.A SS is a SpreadSheet but I am assuming you have MS Excel or something better. Most people seem to mess with them when doing model calculations. FL ___MN_ CN1_ TF__ CFG/S T1507 CFD/S CFN/S CFN ___FN THRUST ERROR %ERROR510 2.000 74.61 2.434 4503 23.589 3467 1034.9 16559 14133 15567 -1433 -9.21OK FL = flight levelMN = Mach NrCN1 is corrected spool 1 speedTF = thrust factor (Rec 1506)CFG/S =corrected gross thrust (lbf)T1507 = Rec. 1507 entry and is the Mass Flow ParameterCFD/S = corrected intake momentum dragCFN = corrected net thrustFN = net thrustTHRUST = the measured thrustERROR = difference between measured and predicted thrust%ERROR = error expressed in terms of a percentage./S = divided by the intake area in square ft in Rec 1501.Ian

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