Turbo-fan idle at high speeds, will air speed up fan speed?

If N1 idle is 30%, will flying idle at very high speeds force the fan to go higher than 30%? (for example idle while descending fast)

And if no, why not?

• yes it will, because then it will create less drag. Sep 3, 2017 at 17:10
• When an aircraft is descending at idle, some engine controls actually keep the idle speed (rpm) high, at least in military aircraft. Sep 4, 2017 at 12:47

1 Answer

Yes, N1 should increase as the plane reaches higher speeds. This means that the blade speed will increase, therefore, increasing N1. Now because the engine setting is constant (throttle), this means that only a slight increase in the amount of thrust will happen.

• Why does N1 increase with increasing airspeed? Sep 6, 2017 at 21:42
• N2 doesn't increase does it? Sep 6, 2017 at 21:57
• @Koyovis you can refer to this to see what N1 is: aviation.stackexchange.com/questions/14690/what-are-n1-and-n2 It's basically self-explanatory because as the airspeed is greater, the fan will speed up. Sep 10, 2017 at 18:41
• You can read the post above as well @Invariant . The N2 will increase as it is once again, the speed of the blades in the high-pressure shaft whereas N1 is the speed in the low-pressure. Either way, both should increase. Sep 10, 2017 at 18:46
• @SethDeegan I know what N1 stands for, that wasn't my question. Sep 10, 2017 at 19:30