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Guest rici

Condition Levers

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Hello,I just wondered if anyone could explain to me why on turboprops such as the Cheyenne and King Air the fuel condition levers have a 'high' and 'low' idle setting? I know the end result, that the idle Ng at low might be about 53% and at high maybe 64% or something. But whats the point in having two idle settings and when would you use them?Cheersrich

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The word "condition" might best be explained as a question asking the pilot what condition does he want the engines in? Ground idle or Flight idle. This of course depends on what his intentions are.Turbine engines are noted for their lag time in rpm response to throttle up and throttle down conditions because of the rotating mass of the turbine as opposed to piston engines. Because of this and other factors the fuel control has two different idle rpms.The thrust generated from a piston engine is directly related to engine rpm whereas the thrust from a turbine (turboprop) is directly related to prop pitch (power lever).Ground idle has a lower "idle NG" because the slower thrust response time isn't needed for ground Ops. Also, on some engine/prop configurations, because the props aren't turning as fast in ground idle there is less centrifugal force which allow the beta locks in the prop hub to engage each blade. Beta locks restrict prop blade movement on the ground at low idle Ng.Upon taking the runway for take-off the condition levers are advanced to "flight idle". This increases Ng to the bottom of the rpm range for flight conditions. As the props start spinning a little faster the beta locks withdraw from the additional centrifugal force. This allows the full range of blade movement including reverse pitch.If you notice on the AFG Beech 300 which uses PT6 engines (note where the exhausts are located), when the engines are shutdown the blades go into feather. They go into feather because of the lack of engine oil pressure. This should occur on all PT6 engine airplanes in flight sim but they don't (aeroworx B-200) and conversely the airplanes powered with Garrett engines (exhaust at the rear of the engine) should shut down with the blades locked in beta (0 pitch)and not feather. Examples of Garrett engine airplanes are the Cessna 441 and the Aero Commander 690.

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This is probably not the case in the real world but in FS, I have had some turboprops that allowed me fine control of taxi speed using the condition levers. Many FS turboprops creep forward at idle and tend to speed up during taxi while still at idle. If this happens to you, try setting et the trottles to minimum and controlling taxi speed with the condition levers.R-

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Excellent post and thanks for sharing the info.BTW, the exhaust on a PT-6 IS at the rear of the engine, the front of the engine is pointed at the rear of the plane.cheers,

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In addition, on Pt6's that idle at 52% such as a king air 100, require 63% N1 if you place a high load demand on the generators such as using air conditioning. Therefore you would have to bump up the condition lever until you obtained at least 63%.

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>This is probably not the case in the real world but in FS, I>have had some turboprops that allowed me fine control of taxi>speed using the condition levers. Many FS turboprops creep>forward at idle and tend to speed up during taxi while still>at idle. If this happens to you, try setting et the trottles>to minimum and controlling taxi speed with the condition>levers.>>R-That is the way the real King Air's operate and taxi. Set about ~200 lbs. torque with the condition levers, advance the power levers until you get rolling and then bring the power levers back to idle and that should give you a nice taxi speed. Use beta range on the props, if needed, to slow you down to minimize use of the brakes.

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