AI aircraft seem to go awefully fast...A question...

[Guest abent]

I will look over the chart and make the appropriate adjustments. I thought to myself after I made the first adjustments...why didn't I listen to these guys and try the numbers they suggested the first time? :( The reason I initially tried #'s in the 290 area is that that's what I cruise at IAS in DF734 which roughly equates to, if I'm remembering correctly, about M.77 at FL320. The reduced thrust settings appeared to create a more reasonable climb. Still a bit fast though, so I'll probably drop them a bit lower too.The help is really appreciated!Adam

[KevinAu 441]

Okay, that is fine, I have done the testing for myself. The data points from msfs that I got were closer to what the whiz wheel gave me than a -7 to -9 correction, with one data point exception where the number I got was over 12kts off what it should be. But that's ok, I agree with your point that compressibility is factored into the calculation of the displayed indicated airspeed of player aircraft but that there may be minor discrepancies between the display and what the user expects to see based on own flight computer calculations.My only argument with you was that for the purpose of AI aircraft control, which was the topic of the original thread, the cruise_speed entry needed to be an EAS number, and that you needed to run your magic calculator one more time after turning a Mach number into an IAS to convert the IAS into an EAS before you start advising other people on what number to enter in the cruise_speed line to a obtain a specfic desired resulting TAS/Mach. That was all.

[Guest Ron Freimuth]

>> I investigated the airspeed 'Base' and 'Weighting' >>variables in AIR files. The 'Base' just sets an offset >>needed typically for slower GA AC such as a C172. -10 kts >>was fine. I found the magic value for the 'weighting' that >>set the IAS in the DF Archer very close to the CASIAS >>calibration table in the PoH. Where CAS=IAS only at 90 kts. >>It was close to the MS default for such AC. By changing >>the weighting value I could move the point IAS equaled CAS. >>>>Are you saying that by a combination of the Base and Weight, >you were able to duplicate a typical instrument error >profile on the airspeed indicator with the IAScrossover point and then IAS>CAS at speeds higher than the >crossover point? Yes. However, the default airspeed 'weighting' factor for SEL's such as the C182 is really OK as it is. >> For jets, I found that changing the default airspeed weight >>from -32768 to +32200 and setting the base offset to 0 gave >>IAS readings within a couple of knots of a table over a wide >>range of FL's and speeds. I especially want Mach number to >>be consistent with IAS readings around 250 - 285 kts, which >>are typical cruise values. >>>>What sort of table? I think it was in my Boeing "Performance Engineering Methods". A table that showed the effect of compressability error vs Mach Number or TAS. > Is this again an instrument error table >you are talking about? One thing to remember though about >the jets is that most of the more modern ones will have an >ADC and the IAS that you read off your displays is actually >already corrected for instrument errors and is in reality a >CAS that we read in flight. The CAS vs IAS error for the B727 is essentially zero, at least at 250 kts IAS. >So basically you are saying that the Base and Weight are to >be used for building a true "IAS" profile with instrument >errors. And that the speed indication we get when Base=0 >and Weight=-32768 is CAS with all atomospheric/aerodynamic >effects already accounted for. NO. **** Base=0 and Weight=+32200. ******=========================================== I had been setting Base to -5 kts in my jets, as Stamatis had determined gave a good IAS reading around 250 kts in cruise. However, that gave an error at approach and landing speeds. Stall speeds, Vref, etc would be off by 5 kts! Not good.>Thanks, I've been wondering what Weight was for. Use my numbers in all jets and I bet you will like them. I hope Stamatis also sees this.Ron

[Guest Stamatis]

Kevin,...before you start advising other people on what number to enter in the cruise_speed line to a obtain a specfic desired resulting TAS/Mach.Why this tone?This whole discussion started when in another forum you gave a list of EAS speeds and called them IAS. I simply corrected you, telling you that the speeds you call IAS are not correct. From then on you seem ######. It is not my fault if you can't tell the difference between IAS and EAS, and no, it does not take a "magic calculator" to calculate the corresponding IAS from Pressure Altitude and Mach, it only requires physics and math. No magic involved.So, please chill out, take a flight and keep enjoying flight simming.Personally, I am out of this thread.Best,Stamatis

[KevinAu 441]

It works perfectly. Thank you.

[KevinAu 441]

Please, there is no need to get upset, I did not mean to sound a "tone" there. The only reason I seemed "######" was that I was admittedly annoyed that you were insisting on a stance that was plain incorrect, such as mach having nothing to do with temperature, and the cruise_speed values that would have resulted in up to a 15% TAS/M error.I'm sorry you feel upset about it now, however I think the thread was good because 1. It proved out that the AI's IAS is actually EAS, which should be the value for the cruise_speed line and 2. I've gained knowledge of the use of the weighting entry in the airfile.I guess as long as you're out, I'm out too. Maybe I'll go watch a movie. I think "Changing Lanes" is out on video.