Flight idle?

[Pace152]

Hey there,

I was just doing some research into stall speeds and found out that the stall speed is calculated with the engine (on a prop) at flight idle.

Can someone please explain to me what is meant by flight idle (on a prop)?

I apologise if this is a really dumb question ;)

[Rainboe]

Minimum power. High power from a prop increases airflow over the wing and delays wing stall to a lower speed over a lot of the wing, so the stalling speed decreases significantly. So if you specify a stalling speed for a prop driven plane, you should really specify at what weight and power on/off.

[cwatters]

I'm only a glider guider but..

I suspect the minimium recommended flight idle rpm is higher than the minimium recommended ground idle rpm.

[DraggieDriver]

Flight idle is the prop pitch that the prop is limited to in flight. Ground idle is a finer pitch (resulting in more drag, thus unsuitable for use in flight), usually available only after weight on wheels and time delay on landing (the extra drag reduces landing roll).

[FROMAIBTOBOEING]

In jets, the flight Idle is the minumum thrust so can select in flight to ensure no flame out of the engine. Ground Idle is always smaller. I guess a turboprop will work the same.

[Pace152]

Thanks for that, I was getting abit confused as I was thinking they calculate the stall speed with the aircraft at constant height and normal cruise attitude but of course they can't because then it wouldn't stall would it :rolleyes:

Thanks again.

[barit1]

Ground idle (for turbines) is usually set to meet a very low thrust level for taxi, but it generally takes a long time to spool up.

Flight Idle is set to meet a spoolup time requirement (xx seconds from flight idle to TOGA); ergo F.I. is a higher rpm that G.I.

Recip engines generally don't have thus issue and so "one size fits all". :}