Can't exceed Mach 0.82 in 744 at cruise alt....

[JSACKS 0]

Recently I did a flight with some thundery weather in FS9 using the 744. At FL370, I could not exceed Mach 0.82 and N1 was nearly 100% at light weight (about 550K lbs). The aircraft really struggled to get beyond this Mach speed and could not do it. I was appalled; then I realized that the TAT was +7C and wondered, would this kind of temp have caused such an event to happen?Jonathan

[kmanning 12]

>>>Recently I did a flight with some thundery weather in FS9>using the 744. At FL370, I could not exceed Mach 0.82 and N1>was nearly 100% at light weight (about 550K lbs). The>aircraft really struggled to get beyond this Mach speed and>could not do it. I was appalled; then I realized that the TAT>was +7C and wondered, would this kind of temp have caused such>an event to happen?>>JonathanJonathan,I believe mach 0.82 is about the correct mach speed for a weight of 550,000 lbs. This is the weight I usually fly at and my mach speed is usually around 0.837 at FL330. The FMC calculates the best performance speed based on the weight of the aircraft. Since you said you were flying through a thunderstorm, did you pressed the contiuous button on the overhead panel? I usually fly the fair weather but if my memory serves me correctly, whenever there is rain or a thunderstorm, the crew will press the continous button on the overhead panel so that the engines don't flame out. This could have played some factor. Did you have gusty headwinds?Ken.

[michal 44]

TAT +7 is definitely not good at FL370. It will have big impact on engine performance.Michael J.http://www.precisionmanuals.com/images/for...argo_hauler.gifhttp://sales.hifisim.com/pub-download/asv6-banner-beta.jpg

[kmanning 12]

>TAT +7 is definitely not good at FL370. It will have big>impact on engine performance.>>Michael J.>http://www.precisionmanuals.com/images/for...argo_hauler.gif>http://sales.hifisim.com/pub-download/asv6-banner-beta.jpgYou're right Michael. Pretty warm at that altitude. The standard temperature at 37000 feet is about -70 degrees F.Ken.

[JSACKS 0]

I think the OAT on this occasion was a relatively warm and friendly minus 26C.Jonathan

[JSACKS 0]

Wind was not a significant factor. I should have added that I only just managed to reach M 0.82 in the first place. It took quite some time to get there and kept slipping back to Mach 0.80 and then it just got breathless and that was it. I would have expected to achieve Mach 0.84 quite easily at that alt and weight, but it was not to be this time round in these conditions.Jonathan