Turboprop engine controls

[dustoff17]

The condition lever serves as a means to save the prop, brakes and fuel on the ground and to save the plane in the air. It provides two different "IDLE" speeds. Those planes that do not have a condition lever have other system(s) that perform the function of the condition lever. Turbo props for the most part (that is a disclaimer so relax out there) have a "lag" from fuel throttle movement to action of the engine.

If you have a KingAir for example that does not have a condition lever you would only have one "idle" setting when the throttle is against the IDLE stop. Let's say it's a HIGH setting all the time; when you taxi, you have to be on the brakes, in beta/reverse or taxiing pretty darn fast all the time while on the ground; not very desireable. If it were in a LOW setting all the time, it would be manageable on the ground but if you had to perform a Go Around, the engine will "lag" from the input of power to the action of the thrust and this might not be a desireable situation to be in either.

The condition lever prevents all of this by giving you control of the IDLE speed. You want HIGH in the air and LOW on the ground. It's really that simple.

 

[jdlilfan]

The P-180 with PT-6's only has two sets of levers. One for power/beta/reverse and the other set controlled condition and prop RPM. On the combined condition/RPM on the right side of the quadrant, the bottom detents were for idle cutoff, then feather, then ground idle, then flight idle. At ground idle the props rotated around 1300-1500 rpm. At flight idle the prop RPM increased to 1800RPM. If you moved the levers forward of flight idle you had regulation of prop rpm from 1800-2000 rpm just like any other constant speed prop.

 

[Hacker15e]

You want HIGH in the air and LOW on the ground. It's really that simple.

The only time I've ever used HIGH IDLE in the 350 is when doing a battery start.

The B300 checklist, POH, and even the FlightSafety Pilot Training Manual make no mention of needing/wanting to use HIGH IDLE in flight.

 

[N519AT]

The only time I've ever used HIGH IDLE in the 350 is when doing a battery start.

The B300 checklist, POH, and even the FlightSafety Pilot Training Manual make no mention of needing/wanting to use HIGH IDLE in flight.

Same here. I have heard of people using high idle in 200's before. We never do, however.

Interesting thing though: Pilatus PC-12s are the exactly same as he described. Low idle on the ground, high idle (flight idle) just before take off and the whole time in the air.

 

[dustoff17]

The only time I've ever used HIGH IDLE in the 350 is when doing a battery start.

The B300 checklist, POH, and even the FlightSafety Pilot Training Manual make no mention of needing/wanting to use HIGH IDLE in flight.

That's because the 350 (and many others) has "another system that performs the function of the condition lever". It's connected to the WOW switch. When the weight is off the gear, the in-flight idle is designed to not go below "HIGH Idle". When on the ground, it goes to "Low Idle" regardless of the position of the lever.

You still have the lever but it won't allow you to set a ground idle RPM in flight. You might, however, need more power on the ground so you can set a high idle if desired.

Next time make a note of the N1 while on the ground at idle. Then get in the air and do the same check.

 

[inigo88]

On the Beech airplanes with separate condition levers, I used to think it was continuous travel (like a mixture lever on a Piston airplane if that makes any sense). But it's actually just a lever with three detents right? Fuel Cutoff, Low Idle and High Idle. So you couldn't set some idle setting between the two, correct?

 

[dustoff17]

On the Beech airplanes with separate condition levers, I used to think it was continuous travel (like a mixture lever on a Piston airplane if that makes any sense). But it's actually just a lever with three detents right? Fuel Cutoff, Low Idle and High Idle. So you couldn't set some idle setting between the two, correct?

If the airplane has a system that compensates for the condition lever positioning, and as far as the effect on the RPM while on the ground you would have CUTOFF, LOW, HIGH, and any setting in between LOW and HIGH.
As far as the effect on the RPM while in the air you would have CUTOFF. The system sets the idle to HIGH while in flight.

On the older systems (or one that does not compensate), you can adjust the RPM via the lever for the full range but will most likely experience the lag in engine response if you demand high power (Go Around) with the lever in the LOW position. And the response to your demand for power will be dependant on the postion of the lever within the range of LOW to HIGH.