747-400

[Airbrakes 0]

Which begs the question, where is the bad TAT coming from? I use ActiveSky using real time WX. But, I WAS out over the Pacific when I reached cruise...boy that takes awhile when near gross wt. Only after cruise did the problems start and expect there were no WX stations in the immediate vicinity. The thick plottens....

TAT = SAT + ram rise. Ram rise is the build up of air particles in front of the airframe as it travels through the air. The higher the SAT, the higher the TAT will be. Atmospheric pressure will effect the EPR (Engine Pressure Ratio) as the air velocity exiting the nozzle needs to be higher than the air pressure in the nacelle for the engine to produce thrust. The LP and HP spools can be firewalled, but not produce as much thrust in that scenario. The SAT can be checked on the FMC's progress page 2. This effects all turbines, BTW.You can add enroute WX stations via AS, but that will come at a cost of reducing frame rates.

[Guest crash_geh]

Oh my. I'm getting technical answers that are all accurate and well thought out but are missing the point of my question. When a person...me...tries 10 times to make a flight on 5 different days, you can't tell me...well you can, but I'm not likely to listen, that I should continue to encounter my air speed bleed off. Good gracious, if this happened with such frequency in real life, 747's would be dropping from the sky. As to ASv6.5. I use the options that give me real time weather. On the ground, in the air, at high altitude. My desire...go figure...is to have a realistic...to the extent possible...flight in a 747.When all is quiet and suddenly I watch airspeed just bleed away for no apparent reason, at least none that make sense, I have to wonder why. So many people have apparently had the same experience and each has dealt with the problem in a different way. What gives? I'm flying on autopilot. I'm step climbing when the FMC instructs me to (for good cause, like the plane has burned off enough fuel to warrant a climb). I'm using ASv6.5 to give me the most realistic weather that it can provide. I'm using FSUIPC for wind smoothing.As to frame rates, I have all the features in FS9 full on. My frame rate averages 50+fps and only on night landings with lots of clouds does it get down to 15 plus or minus. ALL in-route wx stations are turned on. I build the flight plan in FSBuild 2.3, run ASv6.5 against the flight plan and run FSBuild again as it now has the winds aloft available to better figure fuel burn.Very helpful opherben...guess my language wasn't as colorful as in a real cockpit when the situation is turning to ....(fill in your own expletive). Ever listened to the black box tapes of a plane going down. Think crap was putting a polite edge on the issue.So again I ask, what might I be doing wrong...over and over and over again? Can the 747 fly consistent flights in the flawed FS9/FSX simulation environments? Does the flawed FS9/FSX wx engine make consistent flights possible?

[Airbrakes 0]

If your airspeed is bleeding off for no apparent reason, it's more likely related to the weather. Next time you get a high TAT/SAT, you can change the weather manually from the drop-down menu. Press "ALT" and go to World--->Weather. Just click on "OK" and the weather will refresh itself. Bit pedantic but the EEC's (Electronic Engine Control's) configure the maximum thrust rating based on calibrated ISA, or ICAO Standard Atmosphere and engine limitations. The TMC (Thrust Management Computer) sets the thrust setting for the A/T based on the FMC selection. When the Low Pressure (LP) spool, which is N1, and the High Pressure spool, which is N2 (applies to the GE and P&W engines as the RR RB211 is a 3 spool, N1 fan and Intermediate Pressure (IP) spool, N2 LP spool and N3 HP spool) are maxed out to the TMC setting, they are firewalled, yet Engine Pressure Ratio (EPR) will bleed off if the air pressure at the nacelle is higher than normal. Turbofans work by drawing in outside air through the N1 fan, and compressing the air as it passes through the LP and HP stages. The LP and HP compressors are a series of foils, or fan blades, that are linked to a turbine on a shaft which pull in air from the previous stage and push it to the next, compressing the air as it passes the stage. From the HP compressor, the air is mixed with fuel in the burner and ignited, then extracted through the turbines and nozzle. It's pretty much the same concept in reality, but real weather doesn't act like the weather in the default MSFS engine. Weather related thrust issues are magnified in MSFS. There are also other countermeasures you can take, such as selecting a new thrust mode.