Beechcraft B350 Will Not Slow Down

[idahosurge]

I have been flying jets mostly for at least five years and I jumped into the Beech King Air 350 today.

When coming in for a landing the plane will not slow down. Even though throttles, prop and conditioner levers are set to the lowest setting, gear down, flaps set to full and desending to the runway the plane will not slow down. I have to tilt the nose up to get the thing to slow down and I am not in a steep desent.

I use to fly this all the time in FS2000 and FS9, I never had this problem as far as I recall. I flew the Beechcraft Baron 58 today after the King Air and it will at least slow down and I have to add throttle to go ahead and land.

Any ideas why the King Air will not slow down?

 

[falcon409]

I assume this airplane has an Autopilot, if so, check to be sure the "Auto-throttle" isn't engaged. I've been the victim of that on occasion.:salute:

 

[LonelyplanetXO]

turboprops are basically crap in FSX. Implementation is very buggy. Theyre about as accurate as helicopters.

LPXOI

 

[warchild]

Who's 350 do you have??? I'll check it out if youd like..

 

[expat]

Make sure the AP is off AND that the two condition levers are on "low idle" - just above the idle/cut off point.

 

[Motormouse]

Make sure the AP is off AND that the two condition levers are on "low idle" - just above the idle/cut off point.

Wrong for a PT6; low idle on the fuel conditon lever is only used on ground;during start-up. Stops ham-fisted pilots overtemping the EGT. You need to use the props as a 'brake' by going to 100% rpm, this allows them to pitch back to the 'Beta' minimum angle of @ 11 deg for a PT6.

Reducing Props to minimum too has opposite effect, they will not reach 'Beta' minimum angle so your 'Flight Idle' thrust will be too high and you won't slow down.

See below posted on PPRUNE which will explain it better; however there is a little error in the aircraft cfg which needs to be corrected too

in this section

[Propellor]
 
[COLOR=red]Change this line to read ---->[/COLOR]
 
beta_min                = 11.0

Microsoft had it set way too high; as a rough example; 1 deg of blade angle =
@ 5% extra thrust when at flight idle.

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.

Here's a nice web-site with pictures --->

http://www.pilotoutlook.com/airplane_flying/split_shaft_free_turbine_engine


ttfn

Pete

 

[stansdds]

Yes, leave the condition levers in high idle and push the prop levers fully forward. This will flatten the pitch of the blades and they will give a little braking action. Once speed drops to about 180 KIAS dial in one notch down flap, that will also slow you, then when you lower the landing gear you will really slow down. And yes, turbo props are the worst in MS flight sims.

 

[idahosurge]

Yes, leave the condition levers in high idle and push the prop levers fully forward. This will flatten the pitch of the blades and they will give a little braking action. Once speed drops to about 180 KIAS dial in one notch down flap, that will also slow you, then when you lower the landing gear you will really slow down. And yes, turbo props are the worst in MS flight sims.

To Stansdds - This is what I thought I was doing and even with the gear down the plane hardly slows down on level flight and will not slow down desending to the runway. Anyway I will try it again and see what happens.


To Warchild - it is the default FSX Beechcraft King Air 350.

 

[warchild]

I dont know what relevancy this has, but on the P-61, with the prop levers pushed all the way forward, the prop is in fine pitch and is where we get the highest speed. To land the P-61 you pull back on the prop lever till it goes into course pitch which reduced the RPM and the speed. Next is to lower the Manifold pressure, but i dont think you have that on the B350.. Simply chop the throttle and the prop and you should slow down.. Lots..

 

[idahosurge]

I changed beta_min to 11 under prop and that did help, but it still does not seem right to me. Maybe it is because I only flew props back in FS2000 and before and back then when you set the throttle to zero the plane would slow down.

There is no autopilot in the FSX King Air that I can see so I do not think autothrottle is on. I see no keyboard command to disable it if it is on.

Prop RPM will not drop below 1500 while in the air even if the throttle and prop levers are at zero and the condition lever is below low idle. Would this be why I seem to always have power? If it is how do I get the Prop RPM to drop while on approach and desending? If I have the throttle at zero and the prop and conditioning levers all the way forward that does not make any difference either (any place in between also does not seem to matter).

Thanks for the help so far, at least now it does slow down more than last night.

 

[stansdds]

I dont know what relevancy this has, but on the P-61, with the prop levers pushed all the way forward, the prop is in fine pitch and is where we get the highest speed. To land the P-61 you pull back on the prop lever till it goes into course pitch which reduced the RPM and the speed. Next is to lower the Manifold pressure, but i dont think you have that on the B350.. Simply chop the throttle and the prop and you should slow down.. Lots..

That doesn't sound right for a round engine. You usually keep the pitch fine, close to full RPM, for the R-2800 around 2200-2300 rpm, and pull the MP back to no less than 23 in.Hg. Pulling the prop back to a low RPM can result in a cooked cylinder head at low speeds and the prop blades will not provide any wind resistance to give a braking action.

 

[stansdds]

I changed beta_min to 11 under prop and that did help, but it still does not seem right to me. Maybe it is because I only flew props back in FS2000 and before and back then when you set the throttle to zero the plane would slow down.

There is no autopilot in the FSX King Air that I can see so I do not think autothrottle is on. I see no keyboard command to disable it if it is on.

Prop RPM will not drop below 1500 while in the air even if the throttle and prop levers are at zero and the condition lever is below low idle. Would this be why I seem to always have power? If it is how do I get the Prop RPM to drop while on approach and desending? If I have the throttle at zero and the prop and conditioning levers all the way forward that does not make any difference either (any place in between also does not seem to matter).

Thanks for the help so far, at least now it does slow down more than last night.

There is no auto-throttle in the B350, but there is an autopilot. One big thing to remember with turboprops is that they do not respond as quickly to throttle inputs as piston driven props. Think of them as jets with props. There is a significant lag in engine response, so plan deceleration and descents well in advance.

 

[warchild]

That doesn't sound right for a round engine. You usually keep the pitch fine, close to full RPM, for the R-2800 around 2200-2300 rpm, and pull the MP back to no less than 23 in.Hg. Pulling the prop back to a low RPM can result in a cooked cylinder head at low speeds and the prop blades will not provide any wind resistance to give a braking action.

I'm not certain FSX pays attention to wind resistence to be honest.. at least, not as for as the props are concerned.. Until we aquired the pilots handbook for the P-61C we didnt fully understand just how slippery it was, and didnt know that it could take twenty to thirty miles to slow it down. Typically, to get it down to 110 mph from 300 mph can take over twenty miles.. but flaps can be lowered to the first step at 250 mph, and that helps dramatically.. But, it was ignorant and desperate times, and landing this thing was a major headache.. Your of course correct in everything you say.. For me however, it became a matter of lowering the rpm, which wouldnt lower unless you changed the pitch of the props, so that was the practice i was using..
Considering how slippery the B350 is, and taking into account that its a turboprop, I figured there just might be a possiblity of there being something related there.. But it seems from the last couple of posts, that i'm incorrect..

I'll fire up FSX after i wake up and see if i can duplicate the situation. Perhaps i can figure something out here..
Pam

 

[expat]

Wrong for a PT6; low idle on the fuel conditon lever is only used on ground;during start-up.

Agree with this re real world PT6 operation + have read from other King Air pilots that you actually want the condition levers on High before touch down where you want the reverse thrust to be most effective. Also have read that, aside from the loading issue on startup, the King Air can operate in Low idle setting.

Problem is - as you also point out - FS makes a mess of turbo prop simulation, causing one to resort to trying things contrary to real world procedures to stop the blasted plane rushing off into the woods or buildings on start up and also slowed down to a reasonable approach speed for landing. I need to try changing the beta setting on all of mine (big fan of prop-jets). Saw this tweak recommended reading Bill Ortis's (Lionheart) web site recently, as the "mad rush" on start up in FSX is worse still on water, e.g. in the Kodiak or PAD Turbo Otter.

Was a big user of the Aeroworx B200 in FS9. Shame I can't get that one to port to FSX without so many problems. Several real world B200 pilots on the Awx boards also discuss the fine points of PT-6 operations including avoiding the brutally expensive "hot start" error. THAT was quite nicely modelled in the Awx King Air.

Thanks for your info and welcome any further pointers or your pointing out any errors with what I have said (am a student pilot but piston only - so far . . ).

 

[idahosurge]

There is no auto-throttle in the B350, but there is an autopilot. One big thing to remember with turboprops is that they do not respond as quickly to throttle inputs as piston driven props. Think of them as jets with props. There is a significant lag in engine response, so plan deceleration and descents well in advance.

Where do I find the controls for the autopilot, under view autopilot is not listed.

Also does auto feather have anything to do with prop RPM since, if so where is that switch. When the gear is up the auto feather caution light is off and with the gear down it is on.

 

[idahosurge]

I found the auto feather switch.

I made another approach and landing, not great, but better. I guess at this point I just need to practice and know that it takes longer to slow the King Air down than what I am used to.

 

[Motormouse]

Also have read that, aside from the loading issue on startup, the King Air can operate in Low idle setting.

It can; as can all the modified PT6 installations; wasn't just King Air that had the problem; by complex operation of governors and cams; the fuel schedule is switched to
'flight' by movement of power lever. Just in case 'Biggles' forgets to move the other lever before take-off.

If you have it try Bill (Lionheart's) Epic LT / Dynasty; I know he had to do some
bespoke gauge work to get that PT6 powerplant to work correctly.

ttfn

Pete

 

[stansdds]

Where do I find the controls for the autopilot, under view autopilot is not listed.

Also does auto feather have anything to do with prop RPM since, if so where is that switch. When the gear is up the auto feather caution light is off and with the gear down it is on.

The autopilot in the MS King Air is just a group of 8 small buttons located near the center of the main panel. The autofeather is a safety system that automatically feathers a prop if its engine RPM suddenly drops more than a predetermined amount. It should have nothing to do with slowing down the B350 and it should be armed during takeoff and landing.

 

[idahosurge]

The autopilot in the MS King Air is just a group of 8 small buttons located near the center of the main panel. The autofeather is a safety system that automatically feathers a prop if its engine RPM suddenly drops more than a predetermined amount. It should have nothing to do with slowing down the B350 and it should be armed during takeoff and landing.

Thanks!

 

[Motormouse]

The autofeather is a safety system that automatically feathers a prop if its engine RPM suddenly drops more than a predetermined amount. It should have nothing to do with slowing down the B350 and it should be armed during takeoff and landing.

Senses engine torque pressure and compares it to the opposite engine; uses two pressures switches one set @ 6 psi and one @ 12 psi;IIRC. In each case the combination of an 'open' or 'closed' pressure switch pair determines if autofeather will happen; its not much of an issue on PT6 as prop has a big spring to assist it to feather anyway.

ttfn

Pete