Range/Temp/Alt-Jets

[jtr]

Speaking in terms of jet transport and temperature, will a higher temp be more beneficial wrt specific air range?

i.e. if its ISA+50 at 330, won't the benefits of better mach/tas ratio outweigh the -ive of reduced engine efficiency?

[BigHairyBum]

As I understand it, for a given mach, TAS will increase as temperature lowers. So cold air is better for engines and speed.

[jtr]

Local Speed of Sound = 39 x Sqrt of local temp(k)

Higher temp = higher TAS

[BigHairyBum]

ok maybe I should read the books again. However, the engines are more limiting. Less power means lower crusing alt and lower performance. Will try to find a chart of optimum cruise levels vs temperature.....

[SuperRanger]

jtr,

you are right. with higher temp, you get higher TAS but at the same time the air is less dense as a result the engines are less efficient. dont know what is the cut off point, i guess should be ISA+15 or the flat-rated temp.

SR