Why does the King Air have two throttles?
Thread Starter
Join Date: Jan 2011
Location: Pennsylvania, USA
Posts: 130
Likes: 0
Received 0 Likes
on
0 Posts
Why does the King Air have two throttles?
I noticed that King Air's have two different "throttles" (sort of). The primary throttle, and a secondary "idle" throttle. What is the reason for the throttle on the right hand side of the quadrant? I have always wondered this. Thanks for any replies.
Join Date: Aug 2007
Location: Godzone
Posts: 391
Likes: 0
Received 0 Likes
on
0 Posts
the condition lever is simply a means of initialing fuel into the FCU for start, and shutting the engine down. The way that the throttle cams work mean that the power levers (the ones on the left) take over control anything above idle.
the power lever sits in a centre position - there is a forward and reverse component of turbo props, so the power lever cannot sit in a fuel cut-off position.
you can usually taxi at idle, but if you are heavy and need more power you use the power levers to increase %
in answer to your question about putting the condition lever to idle when the 'master' throttle is at full power? nothing will happen. if you go to shut-off though the engine will stop.
the power lever sits in a centre position - there is a forward and reverse component of turbo props, so the power lever cannot sit in a fuel cut-off position.
you can usually taxi at idle, but if you are heavy and need more power you use the power levers to increase %
in answer to your question about putting the condition lever to idle when the 'master' throttle is at full power? nothing will happen. if you go to shut-off though the engine will stop.
Join Date: Oct 2005
Location: USA
Posts: 3,218
Likes: 0
Received 0 Likes
on
0 Posts
PT6 installations use various combinations of power controls. Some use three levers, some use two.
In the King Air series, the power levers control fuel flow in the forward range, and schedule propeller angle and fuel flow in the beta, or ground range. Beta is anything below flight idle.
The propeller levers cover RPM control and feathering.
The condition levers adjust ground idle fuel flow, and are used to shut off fuel.
Some prefer to move the condition lever to high for takeoff and will retard it to low after landing, for taxi. Some prefer to leave it low for all operations.
When the condition lever is in high, faster response to reverse is available on the ground with more reverse, while it also means more residual torque or thrust coming over the fence when landing. If one must go around, keeping the condition levers high on landing keeps the engine spooled up a little more, giving a faster power response.
In the King Air series, the power levers control fuel flow in the forward range, and schedule propeller angle and fuel flow in the beta, or ground range. Beta is anything below flight idle.
The propeller levers cover RPM control and feathering.
The condition levers adjust ground idle fuel flow, and are used to shut off fuel.
Some prefer to move the condition lever to high for takeoff and will retard it to low after landing, for taxi. Some prefer to leave it low for all operations.
When the condition lever is in high, faster response to reverse is available on the ground with more reverse, while it also means more residual torque or thrust coming over the fence when landing. If one must go around, keeping the condition levers high on landing keeps the engine spooled up a little more, giving a faster power response.
Thread Starter
Join Date: Jan 2011
Location: Pennsylvania, USA
Posts: 130
Likes: 0
Received 0 Likes
on
0 Posts
PT6 installations use various combinations of power controls. Some use three levers, some use two.
In the King Air series, the power levers control fuel flow in the forward range, and schedule propeller angle and fuel flow in the beta, or ground range. Beta is anything below flight idle.
The propeller levers cover RPM control and feathering.
The condition levers adjust ground idle fuel flow, and are used to shut off fuel.
Some prefer to move the condition lever to high for takeoff and will retard it to low after landing, for taxi. Some prefer to leave it low for all operations.
When the condition lever is in high, faster response to reverse is available on the ground with more reverse, while it also means more residual torque or thrust coming over the fence when landing. If one must go around, keeping the condition levers high on landing keeps the engine spooled up a little more, giving a faster power response.
In the King Air series, the power levers control fuel flow in the forward range, and schedule propeller angle and fuel flow in the beta, or ground range. Beta is anything below flight idle.
The propeller levers cover RPM control and feathering.
The condition levers adjust ground idle fuel flow, and are used to shut off fuel.
Some prefer to move the condition lever to high for takeoff and will retard it to low after landing, for taxi. Some prefer to leave it low for all operations.
When the condition lever is in high, faster response to reverse is available on the ground with more reverse, while it also means more residual torque or thrust coming over the fence when landing. If one must go around, keeping the condition levers high on landing keeps the engine spooled up a little more, giving a faster power response.
Join Date: Sep 2006
Location: West Coast Canada
Age: 71
Posts: 69
Likes: 0
Received 0 Likes
on
0 Posts
There are 3 levers on the control pedestal of a PT6 powered Beech King Air.
The one closest to the pilot – left hand side is the power lever – sometimes abused by calling it a “Throttle” by those oafs who don't know better.
The purpose of the power lever is two-fold – first it controls the fuel schedule by the interconnect from the engine cambox to the fuel control unit. Depending on the model of PT6 you can have different cambox operation – but in most cases the system will increase gas generator speed in the forward direction for increasing power to the maximum limit allowed and also will add gas generator speed when moved into the reverse position.
The second function of the power lever is to control the propeller blade angle (NOT SPEED) when the engine is operated in “Beta”. This is accomplished by the cambox operation through a push/pull cable (Teleflex) control that is linked to the beta valve on the forward face of the propeller governor and the connection for blade angle feedback that is through a carbon block in a beta ring attached to the propeller.
On the Beech King Air “Beta” range is from a degree or two above your prime blade angle – which is significantly ahead of the flight idle position. Beta in the case of the PT6a-42 in a King Air 200 for example starts at about +21 degrees of blade angle all the way to – 14 degrees in reverse. Flight idle is about 11 degrees.
BETA IS DEFINED AS THE RANGE OF ENGINE OPERATION WHERE THE POWER LEVER CONTROLS THE FUEL SCHEDULE AND THE BLADE ANGLE OF THE PROPELLER.
The second lever on the control pedestal is the “PROPELLER” control. It has 2 functions. When pull all the way aft it will feather the propeller. When pushed out of the feather detent it will be in the “LOW” speed or minimum governing setting – and when advanced increases the speed of the propeller to the “MAXIMUM” speed setting. When the power lever is moved from the flight idle gate the gas generator speed is increasing and the propeller blade angle is increasing as it is still in beta mode. Just above the primary blade angle check prop speed and torque for the day condition the system will transition from beta to constant speed mode – sometimes referred to as “ALPHA” mode. In this range the power lever will control only the gas generator speed and the propeller control lever will control the speed of the propeller through the constant speed governor.
The third lever on the control pedestal is the “FUEL CONDITON” lever. The original purpose of the fuel condition lever was to simply shut off or turn on the fuel to the engine. It is basically a HP (High Pressure) shutoff valve system that is operated by the flight crew to start and shut down the engine. It was modified on the Beech – as well as other aircraft – to include a low idle and a high idle position. The original reason for this was the small PT6 engines would bog down if you turned on the generator,bleed air, or the air conditioner compressor with the engine at idle. The extra loading at idle will cause an increase in fuel flow by the fuel control unit to keep the engine at the idle speed. Under this condition with only idle airflow through the engine - the Inter Turbine Temperature will increase to the point that it will cook the engine.
On some installations the flight crew must remember to advance the power lever to 68% or 70% minimum to obtain sufficient airflow through the engine so when loaded with the generator, bleed air, and/or the air conditioner compressor it had sufficient airflow to absorb the extra heat from the increase in fuel commanded by the fuel control unit.
So the fuel condition lever was modified/designed to “Bump” up – mechanically when advanced to the full forward position the linkage at the fuel control to give an easy way for the flight crew to obtain the correct gas generator speed.
The interactions of the 4 governors on the PT6a engine are complex and have overlapping functions to protect the engine and propeller.
The propeller lever has direct control of the propeller governor in the constant speed range.
The power lever has control of the governor section of the fuel control unit as well as a reset capability for the fuel topping governor.
The propeller hydraulic overspeed governor is set for a specific speed and does not have a cockpit control for it's operation. There is a test function to reset the speed down below that of the propeller governor so it's operation can be checked on the ground.
Regards,
Mx Trainer
The one closest to the pilot – left hand side is the power lever – sometimes abused by calling it a “Throttle” by those oafs who don't know better.
The purpose of the power lever is two-fold – first it controls the fuel schedule by the interconnect from the engine cambox to the fuel control unit. Depending on the model of PT6 you can have different cambox operation – but in most cases the system will increase gas generator speed in the forward direction for increasing power to the maximum limit allowed and also will add gas generator speed when moved into the reverse position.
The second function of the power lever is to control the propeller blade angle (NOT SPEED) when the engine is operated in “Beta”. This is accomplished by the cambox operation through a push/pull cable (Teleflex) control that is linked to the beta valve on the forward face of the propeller governor and the connection for blade angle feedback that is through a carbon block in a beta ring attached to the propeller.
On the Beech King Air “Beta” range is from a degree or two above your prime blade angle – which is significantly ahead of the flight idle position. Beta in the case of the PT6a-42 in a King Air 200 for example starts at about +21 degrees of blade angle all the way to – 14 degrees in reverse. Flight idle is about 11 degrees.
BETA IS DEFINED AS THE RANGE OF ENGINE OPERATION WHERE THE POWER LEVER CONTROLS THE FUEL SCHEDULE AND THE BLADE ANGLE OF THE PROPELLER.
The second lever on the control pedestal is the “PROPELLER” control. It has 2 functions. When pull all the way aft it will feather the propeller. When pushed out of the feather detent it will be in the “LOW” speed or minimum governing setting – and when advanced increases the speed of the propeller to the “MAXIMUM” speed setting. When the power lever is moved from the flight idle gate the gas generator speed is increasing and the propeller blade angle is increasing as it is still in beta mode. Just above the primary blade angle check prop speed and torque for the day condition the system will transition from beta to constant speed mode – sometimes referred to as “ALPHA” mode. In this range the power lever will control only the gas generator speed and the propeller control lever will control the speed of the propeller through the constant speed governor.
The third lever on the control pedestal is the “FUEL CONDITON” lever. The original purpose of the fuel condition lever was to simply shut off or turn on the fuel to the engine. It is basically a HP (High Pressure) shutoff valve system that is operated by the flight crew to start and shut down the engine. It was modified on the Beech – as well as other aircraft – to include a low idle and a high idle position. The original reason for this was the small PT6 engines would bog down if you turned on the generator,bleed air, or the air conditioner compressor with the engine at idle. The extra loading at idle will cause an increase in fuel flow by the fuel control unit to keep the engine at the idle speed. Under this condition with only idle airflow through the engine - the Inter Turbine Temperature will increase to the point that it will cook the engine.
On some installations the flight crew must remember to advance the power lever to 68% or 70% minimum to obtain sufficient airflow through the engine so when loaded with the generator, bleed air, and/or the air conditioner compressor it had sufficient airflow to absorb the extra heat from the increase in fuel commanded by the fuel control unit.
So the fuel condition lever was modified/designed to “Bump” up – mechanically when advanced to the full forward position the linkage at the fuel control to give an easy way for the flight crew to obtain the correct gas generator speed.
The interactions of the 4 governors on the PT6a engine are complex and have overlapping functions to protect the engine and propeller.
The propeller lever has direct control of the propeller governor in the constant speed range.
The power lever has control of the governor section of the fuel control unit as well as a reset capability for the fuel topping governor.
The propeller hydraulic overspeed governor is set for a specific speed and does not have a cockpit control for it's operation. There is a test function to reset the speed down below that of the propeller governor so it's operation can be checked on the ground.
Regards,
Mx Trainer
Join Date: Sep 2006
Location: West Coast Canada
Age: 71
Posts: 69
Likes: 0
Received 0 Likes
on
0 Posts
Is that solely for taxi purposes?
What happens if you are at full (master) throttle and pull the fuel condition lever to idle?
Nothing!!!
Fuel condition lever can only bump up to the 70% gas generator speed. If the power lever is set to a position that is greater than the high idle selected it will simply pick up on the fuel control linkage and increase gas generator speed from that point.
If the fuel condition lever is in low idles - retarding the power lever to flight idle will give you a low idle condition.
If the fuel condition lever is selected to the high position then the power lever will bring the idle speed down to high idle when retarded to the flight idle position.
Mx Trainer
What happens if you are at full (master) throttle and pull the fuel condition lever to idle?
Nothing!!!
Fuel condition lever can only bump up to the 70% gas generator speed. If the power lever is set to a position that is greater than the high idle selected it will simply pick up on the fuel control linkage and increase gas generator speed from that point.
If the fuel condition lever is in low idles - retarding the power lever to flight idle will give you a low idle condition.
If the fuel condition lever is selected to the high position then the power lever will bring the idle speed down to high idle when retarded to the flight idle position.
Mx Trainer
Join Date: Mar 2008
Location: Blighty
Posts: 84
Likes: 0
Received 0 Likes
on
0 Posts
I've never seen anything in our 350 manuals for using high idle for take-off. We use it for every battery start and for when doing short field landings. The rest of the time they are in low idle (except when shutdown of course)
Extract from the checklist for a battery start (also known as cross generator start)
3. Right Ignition and Engine Start.......................................ON
(R IGNITION ON) - ILLUMINATED
(R FUEL PRES LO) - EXTINGUISHED
4. Right Condition Lever (after 12% N1 minimum).............LOW IDLE
5. Right ITT and N1.......................................................... MONITOR
6. Right Oil Pressure.................................................... .....CHECK
7. Right Ignition and Engine Start (at 50% N1 or above)....OFF
8. Right Condition Lever....................................................HIGH IDLE
9. Right Generator................................................... ..........RESET, THEN ON
There is a generator limitation that the load can only be up to 75% with an N1 between 62% - 70%. In order to get 100% from the generator we need the N1 above 70% and by selecting HIGH IDLE the N1 increases to above 70%. We're then in a position to start the other engine.
Once the other engine is stable the condition lever is put back into LOW IDLE for the remainder of the flight.
The other phase of flight which they are used is for short field landings. Again by selecting HIGH IDLE the N1 is kept above 70% minimum giving maximum reverse performance. We very rarely have a need for short field landings and just use reverse in LOW IDLE and still get decent braking action from the reverse range.
With regard to using HIGH IDLE for take off, as said there is nothing I can see in the 350 POH, but it may be used in other models (200, 90).
Cheers
Extract from the checklist for a battery start (also known as cross generator start)
3. Right Ignition and Engine Start.......................................ON
(R IGNITION ON) - ILLUMINATED
(R FUEL PRES LO) - EXTINGUISHED
4. Right Condition Lever (after 12% N1 minimum).............LOW IDLE
5. Right ITT and N1.......................................................... MONITOR
6. Right Oil Pressure.................................................... .....CHECK
7. Right Ignition and Engine Start (at 50% N1 or above)....OFF
8. Right Condition Lever....................................................HIGH IDLE
9. Right Generator................................................... ..........RESET, THEN ON
There is a generator limitation that the load can only be up to 75% with an N1 between 62% - 70%. In order to get 100% from the generator we need the N1 above 70% and by selecting HIGH IDLE the N1 increases to above 70%. We're then in a position to start the other engine.
Once the other engine is stable the condition lever is put back into LOW IDLE for the remainder of the flight.
The other phase of flight which they are used is for short field landings. Again by selecting HIGH IDLE the N1 is kept above 70% minimum giving maximum reverse performance. We very rarely have a need for short field landings and just use reverse in LOW IDLE and still get decent braking action from the reverse range.
With regard to using HIGH IDLE for take off, as said there is nothing I can see in the 350 POH, but it may be used in other models (200, 90).
Cheers
Join Date: Oct 2005
Location: USA
Posts: 3,218
Likes: 0
Received 0 Likes
on
0 Posts
A number of different turboprop aircraft using PT6A engines have significant idle thrust at 70% Ng, such that landing over the fence at low idle works well to reduce residual thrust. Where maximum reverse is desired, the levers can be put forward on touchdown, or even after entering beta.
It's a matter of technique. Much like setting props forward; I prefer not to have to hear them wind up, and that's best done at a low power setting. Works great for visual landings, overhead patterns, etc. Sometimes the use of high idle is also useful for braking effect, such as holding a high airspeed on a long final to a busy field. Some airplanes slow down better than others, and there are times when keeping high idle up is a good idea, but it's a matter of technique to adapt one's practice to the circumstance.
I've done a lot of low altitude work in mountainous terrain in single engine PT6 powered airplanes, where a fairly rapid power response is necessary, or may be necessary; keeping high idle on the idle descents down a steep slope or inside a canyon is important because of the faster power response. In gusty conditions when landing, the same may be true, even though the PT6 doesn't respond all that quickly and one still must anticipate and lead. There's nothing like being in a tight turn in a narrow canyon in gusty conditions and having the bottom drop out, and calling for power and getting that long, agonizing lag.
It's a matter of technique. Much like setting props forward; I prefer not to have to hear them wind up, and that's best done at a low power setting. Works great for visual landings, overhead patterns, etc. Sometimes the use of high idle is also useful for braking effect, such as holding a high airspeed on a long final to a busy field. Some airplanes slow down better than others, and there are times when keeping high idle up is a good idea, but it's a matter of technique to adapt one's practice to the circumstance.
I've done a lot of low altitude work in mountainous terrain in single engine PT6 powered airplanes, where a fairly rapid power response is necessary, or may be necessary; keeping high idle on the idle descents down a steep slope or inside a canyon is important because of the faster power response. In gusty conditions when landing, the same may be true, even though the PT6 doesn't respond all that quickly and one still must anticipate and lead. There's nothing like being in a tight turn in a narrow canyon in gusty conditions and having the bottom drop out, and calling for power and getting that long, agonizing lag.
