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JiBrady

Help me understand these two controls...

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I would like some help in understanding the function of two controls. Also, if possible, explain the correct method of adjusting them.First is a item called "Condition Lever" and the second is a "Prop Pitch" control. I understand the prop pitch changes the pitch of the prop. I don't know how, or when, to make adjustments to it. I know less about a "Condition Lever". For now, I just leave them fully advanced.Thanks,Jim

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The prop pitch is like you said, it acts like the gear stick on a car, when you are not moving the blades are set to minimum pitch so they dont bite the air, and plane doesnt move, when you are in taxi you can adjust the pitch to bite just enough air to move the plane and contol your speed , especialy in FSX turboprops, when taking off, blades are set to max to bite all the air they can to give maximum pull, once at cruise the pitch can be reduced so the engine doesnt need to work as hard, and that should help reduce the ITT temp, you will need to watch the ITT as you climb, because as the air gets thinner it looses its cooling effect so pitch need to be adjusted to keep the temp out of the red. The conditon lever ( googled it wasnt sure myself ) acts like a mixture lever on a normal engine and simply controls the fuel flow to the engine, on turboprops, it may have indent position like cut off, ground idle and flight idle, some only have cutoff and on, just set it to the appropriate position.

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Generally speaking that explanation is correct, however, for a good many aircraft you probably actually want to be in fine pitch for take off. It is possible to take off in coarse pitch, but you'll generally be right over the other side of the airfield and scraping the boundary fence by the time you get in the air. :( Al

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Ahhh.. the old, "Prop pitch" dilema... The first thing you need to understand, is that we're talking about "Constant Speed" props (hencforth known as CSP). The pilot does NOT control the prop pitch. He controls the prop speed (RPM).I don't know enough about these props, when they're attached to turbine engines, to fully explain them... But the function is close enough to how they function when attached to a piston engine, for me to add input here.When taking off.. you don't select the finest pitch.. you select the best (normally highest) RPM for takeoff. The CSP will then set whatever pitch is needed, to keep the prop at that RPM.For example. Takeoff with the prop control all the way forward, and apply takeoff power. Prop pitch will first be quite "fine".. but as airspeed builds, the pitch goes more "coarse", in order to maintain the selected (constant) RPM (speed).. As you level off and gain airspeed, the prop pitch will coarsen even further.. ALL of this prop pitch change happens without you touching the prop-control. When you DO adjust prop speed for cruise, you aren't selecting a coarser pitch.. you're selecting a lower RPM. Sure, the prop pitch increases as you do this, but only to slow the prop down, by increasing its workload (AoA). If you are now cruising along and pitch up without changing the power setting OR touching the prop-control.. the CSP will lessen the pitch, so that the prop speed can remain "constant". OR.. if you pitched down (not touching the throttle or prop control), the prop pitch would increase, in order to keep the prop speed "constant".Airspeed and power settings decide the prop pitch... all that the prop control does, is decide at which RPM it all happens.

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And moving the prop control foward, will act like a good speed brake; at least in piston planes. I don't have any experience with turbo-props.You can use this braking ability when on approaches after you've already pulled the power back. It moves the prop to a finer pitch. If the throttle (manifold pressure) isn't pulled back, you'll feel it in your stomach, and it can over speed the engine. Not good!C/S props have advanges over fixed pitch, because fixed pitch is usually a compromise between better take off performace, cruise performance, or somewhere in the middle. A C/S in fine pitch/high rpm allows the piston engine to develope as much horsepower as it can on takeoff. While in cruise, the C/S runs at a courser setting which is like a lower gear for freeway driving.As to using the C/S as a brake while flight simming................we're kind of out of luck. Sim planes just don't replicate it very well, if at all.L.Adamson

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C/S props have advanges over fixed pitch, because fixed pitch is usually a compromise between better take off performace, cruise performance, or somewhere in the middle. A C/S in fine pitch/high rpm allows the piston engine to develope as much horsepower as it can on takeoff. While in cruise, the C/S runs at a courser setting which is like a lower gear for freeway driving.
That's close.. but still a little off-base. The "gear" comparison doesn't work, because different gears mean different RPM for a given speed. The CSP is always trying to find the highest "gear" that a SELECTED RPM will allow. RPMs never change.Like.. when you pull the RPMs back to 2400 for cruise, you aren't selecting a higher gear (which would mean a higher airspeed if the RPMs were not being forced down).. you're "forcing" the engine into a less powerful (more fuel efficient) RPM.If absolute top speed was your goal.. you'd select the highest "gear" (if it were comparible to gears).. However.. if you want absolute top speed with a CSP, you'd leave the prop control set at the highest RPM (all the way forward).. The CSP would constantly select the most aggresive pitch possible (highest gear) for THAT RPM..I know.. it's confusing..lol

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If absolute top speed was your goal.. you'd select the highest "gear" (if it were comparible to gears).. However.. if you want absolute top speed with a CSP, you'd leave the prop control set at the highest RPM (all the way forward).. The CSP would constantly select the most aggresive pitch possible (highest gear) for THAT RPM..As to that statement, I'll reserve a question mark. I have a C/S prop (real life) but never run it at full rpm in cruise. My prop governor is set at 2700 rpm which is red-line for the Lycoming engine. I usually pull it back to 2600 after takeoff, but sometimes leave it full forward in pattern work.I'm going to say, that the highest possible speed is going to be somewhat courser in pitch than full forward. It's the same reason that a courser pitch cruise prop is faster than a finer pitch takeoff prop for fixed pitch airplanes. I'll have to look up some numbers for planes similar to mine that do some racing. Manifold pressure/ rpm's are usually listed.L.Adamson

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I'm going to say, that the highest possible speed is going to be somewhat courser in pitch than full forward. It's the same reason that a courser pitch cruise prop is faster than a finer pitch takeoff prop for fixed pitch airplanes. I'll have to look up some numbers for planes similar to mine that do some racing. Manifold pressure/ rpm's are usually listed.
You're still confused about what the CSP does. (don't worry.. you're not alone..many a CSP owner and/or instructor still have trouble getting it)Full forward is NOT a pitch setting. Pulled slight back is not a slightly coarser pitch. No position for the prop-control is a pitch-setting. When the the prop control is full forward, it's simply the highest RPM. The pitch will be determined by airspeed and the power setting.Unless your engine has worn in such a way that the red-line is not the top of the power-curve (all but impossible), the red-line is where THE most HP is being generated. The CSP will then (depending on airspeed and power setting (MP)), go to whatever pitch is needed, to "keep" the engine at that RPM. If you're cruising along at 23"MP and 2300RPM, and then increase MP to say, 28".. the tach won't budge, the prop will stay at 2300RPM.. but the airplane will accelerate.. because, as you increase MP, the CSP will steepen the prop pitch (to keep it at 2300).. and you didn't even touch the prop-control.You can make a complete flight, never touching the prop control... and the CSP will go from the ultimate climb-prop, to the ultimate cruise-prop, and everything in between.. without you ever laying a hand on the blue knob.Reducing to 2600RPM just after takeoff, is good practice.. it reduces engine wear. Same for reducing RPM for cruise. It's all about economy and wear.

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Try looking at it like this..

My prop governor is set at 2700 rpm which is red-line for the Lycoming engine.
What is it that governs the prop ? What keeps it from going above 2700RPM ?It's the CSP.. It's like a governor where you control the RPMs .. There only two things that make the prop want to go faster. 1)increased airspeed 2)increased MPIn either case.. as the prop "tries" to spin faster, the governor (CSP) just increases it's workload (AoA), to keep it at the selected RPM.Same thing for the reverse scenario. If you reduce MP (or decrease airspeed), before the prop can slow down, the "governor" lessens the AoA so that it can remain at the selected RPM

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You're still confused about what the CSP does. (don't worry.. you're not alone..many a CSP owner and/or instructor still have trouble getting it)Full forward is NOT a pitch setting. Pulled slight back is not a slightly coarser pitch. No position for the prop-control is a pitch-setting. When the the prop control is full forward, it's simply the highest RPM. The pitch will be determined by airspeed and the power setting.Unless your engine has worn in such a way that the red-line is not the top of the power-curve (all but impossible), the red-line is where THE most HP is being generated. The CSP will then (depending on airspeed and power setting (MP)), go to whatever pitch is needed, to "keep" the engine at that RPM. If you're cruising along at 23"MP and 2300RPM, and then increase MP to say, 28".. the tach won't budge, the prop will stay at 2300RPM.. but the airplane will accelerate.. because, as you increase MP, the CSP will steepen the prop pitch (to keep it at 2300).. and you didn't even touch the prop-control.You can make a complete flight, never touching the prop control... and the CSP will go from the ultimate climb-prop, to the ultimate cruise-prop, and everything in between.. without you ever laying a hand on the blue knob.Reducing to 2600RPM just after takeoff, is good practice.. it reduces engine wear. Same for reducing RPM for cruise. It's all about economy and wear.
Actually, I'm not much confused. :( The gearshift analogy isn't perfect, but it gives the general idea. A lot more pep for takeoff, and much like a lower gear for freeway driving or cruise flight. I usually run around 2300 rpm in cruise because I have continuous use prop restrictions between 2000 & 2250 rpm. I'll agree on the 23", 2300 RPM, and 28". But................ the blue knob pushed full forward, is going to slow me down; and therefor not the ultimate cruise prop. The rpms will again rise to 2700 if possible, and just not take as much bite out of the air. If I didn't need to touch the blue knob, I'd have what amounts to almost a FADEC system, sans the mixture control for leaning. If the weather wasn't so lousy tomorrow, I'd verify with exact numbers. Some pilots will even fly a complete flight, less the landing approach with throttle (manifold pressure) at full, and just use the blue knob for airspeed. Usually, I'll never see 28" because I fly out of high altitude airports. At 9,500' msl, I'll usually top out around 22".edit: Here are some numbers for a comparible plane to mine. In this case, full rpms (finer pitch) are getting the highest airspeeds. And then I read farther, and find that others get less efficiency speed wise at the higher rpm settings. So..............?????2450 RPM (heading - speed in knots)360 deg. - 174, 175, 174, 175, 174120 deg. - 170, 170, 169, 169, 169240 deg. - 162, 162, 162, 162, 163Average Speed = 168.72700 RPM360 deg. - 177, 177, 177, 177, 178120 deg. - 172, 172, 172, 172, 173240 deg. - 165, 166, 165, 165, 166Average Speed = 171.6L.Adamson
Try looking at it like this..What is it that governs the prop ? What keeps it from going above 2700RPM ?It's the CSP.. It's like a governor where you control the RPMs .. There only two things that make the prop want to go faster. 1)increased airspeed 2)increased MPIn either case.. as the prop "tries" to spin faster, the governor (CSP) just increases it's workload (AoA), to keep it at the selected RPM.Same thing for the reverse scenario. If you reduce MP (or decrease airspeed), before the prop can slow down, the "governor" lessens the AoA so that it can remain at the selected RPM
I agree..L.Adamson

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Some pilots will even fly a complete flight, less the landing approach with throttle (manifold pressure) at full, and just use the blue knob for airspeed. L.Adamson
Hi Larry,I thought that having full MAP and low RPMs was not advised since it could be stressful for the engine?Marco

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Honest.. I love this stuff. I'm a CFI, and I really enjoy teaching... So, I'm not trying to be argumentative, nor a smart-alec :( But.. you're STILL not getting it... :(

But................ the blue knob pushed full forward, is going to slow me down; and therefor not the ultimate cruise prop. The rpms will again rise to 2700 if possible, and just not take as much bite out of the air.
A CSP is always taking the biggest "bite" possible... ALWAYS. Pushing the knob forward just allows the biting to happen at a higher RPM.. The biggest bite possible AT the top of the power curve WILL yield the highest thrust.It took me a while to get my head around this too..Next time you're up.. fly straight and level with the throttle and prop-control all the way forward. At that time, your engine is at max HP.. and the CSP is biting as much as it can (that's what's KEEPING it from going above 2700RPM). Then bring the prop knob back a little and watch your airspeed drop. You aren't asking the prop to "bite" more, because it CANNOT bite more. If it tried to "bite" more, it would (are ya ready for this ?) force the engine below the peak-power RPM (is it starting to make sense ? )

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Hi Larry,I thought that having full MAP and low RPMs was not advised since it could be stressful for the engine?Marco
That's what we always heard in the olds days, and much had to do with WWII radials. But things seemed to have changed, as there are so many people experimenting. Lyc still doesn't recomment running LOP (lean of peak), but apparently it truely does work better for many engines (fuel injected).L.Adamson

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Hi Larry,I thought that having full MAP and low RPMs was not advised since it could be stressful for the engine?Marco
I think Charles Lindberg himself established that this is not necessarily the case in world war two...I'd have to look at his bio again-but he got better performance/fuel economy by not going full Map and low rpm-but doing a little of that....

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Oh my.. now we're off on a tangent..

Hi Larry,I thought that having full MAP and low RPMs was not advised since it could be stressful for the engine?Marco
This is true.. that's why we're not to allow the prop-rpm/100 to fall below the MP in inches.. I.E. 25"/2500 (25/25) is OK.. but 25"/2300 is bad. And the engine will let ya know it... it will vibrate and even "buck" a little.That's the old, "square it off" method ( 23/23 24/24 25/25 ).Now, of course this MP/RPM relationship changes for turbocharged or supercharged engines (the engines are built accordingly), but the theory is the same. High MP and low RPM = bad
I think Charles Lindberg himself established that this is not necessarily the case in world war two...I'd have to look at his bio again-but he got better performance/fuel economy by not going full Map and low rpm-but doing a little of that....
This is the bonus advatage to a CSP.. it allows the pilot to save fuel AND engine wear.

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Honest.. I love this stuff. I'm a CFI, and I really enjoy teaching... So, I'm not trying to be argumentative, nor a smart-alec :( But.. you're STILL not getting it... :(
I'll always argue with CFI's..................and sometimes I'm right! :( In the meantime, I'll research this farther, since I'm not getting a full consensus one way or the other. There would seem to be variables when it comes to available engine power, etc.In the meantime.............what causes lift? Is it pitch for speed or throttle? Or both? LOP or ROP? B) L.Adamson

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Guest KenS

Jim,I don't Know if your question was answerd, but if the controls you refer to are for a TurboProp AC then the condition lever is for speed control of the jet engine. It runs at two speeds and the middle detent is generally ground idle and the upper detent is flight idle. The RPM lever is to limit the maimum speed of the prop(s). The throttle is essentially a prop pitch control.This is a somewhat simplified explanation and I hope it helps.Have a good day and happy flying.Ken

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This is true.. that's why we're not to allow the prop-rpm/100 to fall below the MP in inches.. I.E. 25"/2500 (25/25) is OK.. but 25"/2300 is bad. And the engine will let ya know it... it will vibrate and even "buck" a little.That's the old, "square it off" method ( 23/23 24/24 25/25 ).
Nope. That's an old wives tale, and is refuted by Lycoming and many POHsFor sure there are MP/RPM combinations that set up bad resonances and need to be avoided, but these are usually stated in the POH, and it's not a general principle to say 23"/2300 bad. If it's in the POH you can fly it and expect it to work (our club Tobago POH allows for 24.4"/2350 as a 75% power setting). Similarly if the POH says don't fly it...

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I need to jump in here because this has never been clear to me.When I take off I have throttle and pitch all the way forward.Is this correct?If so when I reach altitude which do I pull back first,throttle or pitch to get proper RPMS?Thanks,Ron

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Nope. That's an old wives tale, and is refuted by Lycoming and many POHsFor sure there are MP/RPM combinations that set up bad resonances and need to be avoided, but these are usually stated in the POH, and it's not a general principle to say 23"/2300 bad. If it's in the POH you can fly it and expect it to work (our club Tobago POH allows for 24.4"/2350 as a 75% power setting). Similarly if the POH says don't fly it...
23"/2300 is not bad.. it's perfectly "squared", which is ideal. And, 24.4/23500 (24.4/23.5) is pretty darn close to squared ( 0.9 difference). Every engine/prop combination is different.. Turbo-normalized engines have they're own scales and MP/RPM relationships.The rule of thumb is no wive's tale.. High MP + low RPM is bad. Call Lyc up and ask them what happens if you fly a C182 at 28" / 2300RPM (if you can even do it). Now.. obviously, at takeoff and into a climb, you can run 28" at 2600 RPM.. but that most DEFINATELY is hard on the engine. If you leveled off at 3000msl and cruised like that, you cut the engine life WAY down.Here's the "rule": If it's in the POH, you can do it. But you won't find any settings in the POH where the settings are more than 1 or 2 units apart. Sans POH, the rule is, you "can" do what ever the engine won't complain about.. again.. you won't get more than a unit or 2 apart before problems start. And even brushing the edge of that is counter-productive. Even IF the engin doesn't balk.. you ARE putting undue stress on it AND the prop.

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I need to jump in here because this has never been clear to me.When I take off I have throttle and pitch all the way forward.Is this correct?If so when I reach altitude which do I pull back first,throttle or pitch to get proper RPMS?Thanks,Ron
Yes.. that's correct. You want max MP and max RPM for takeoff. As soon as the climb is established, it's good practice to back prop-RPS back just a tad.. The slight reduction of RPM add up over the hours of takeoff power settings. In a non turbo-charged airplane; the MP will take care of itself. It will fall off as altitude increases. All you need to do is to make sure the difference between MP and RPM never get too large.In fact.. using a C182 as an example.. if your flight will have you cruising above 6000msl, you'll firewall the throttle at takeoff.. and never touch it again (assuming a direct climb to altitude). At aprox. 6000msl, full-throttle will give you 23-24" of MP.. which is right at most cruise settings.As for which to do first ? For accelerating or climbing; adjust the prop first. Like.. if you're cruising at 23/23.. increase RPMs first, so that the MP doesn't get too high above RPM.Conversely.. as you descend.. pull the power back first..

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Here's the "rule": If it's in the POH, you can do it. But you won't find any settings in the POH where the settings are more than 1 or 2 units apart. Sans POH, the rule is, you "can" do what ever the engine won't complain about.. again.. you won't get more than a unit or 2 apart before problems start. And even brushing the edge of that is counter-productive. Even IF the engin doesn't balk.. you ARE putting undue stress on it AND the prop.
One thing for sure, is that numerous rules and POH standards are getting thrown out the window. Running lean of peak is a good example. Lycoming has been dead set against it, but facts keep emerging that it's great. Lycoming has even backed down a bit in regards to what's in their manual. On the subject of running the C/S prop at full foward to gain the fastest speed; I brought this up this morning during breakfast with a few pilots who own constant speeds. The general thought was, that pulling the prop back a bit would yield the highest airspeed. But there was no proof since none of us run our engine/prop combos that way...................because fuel consumption would be on the high end.However, after reading several prop & speed reports with various RV's that we fly, it seems apparent that these particular aircraft DO fly faster with the prop at full foward. The bottom line for us, will be to try it.. :( edit: Turns out by chance, that this subject just came up on our RV builders forums. First guy say's to run the C/S prop at full throttle and 2700 max rpm to find the fastest airspeed. The next guy says "not so", as his prop's happy place is around 2600 rpm. Then the third guy say's he agrees with reply number one. :( L.Adamson

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Don't just love the ambiguity ?We can filter through it all though.. because (unless there's some sort of malfunction).. a prop at its the highest RPM, held AT that RPM because of its pitch.. WILL yeild the most thrust. This isn't opinion.. this is physics... LOLAnd yeah.. POHs are filled full of liability dodging "errors". The last Bonanza POH I read, called for NO flaps during short-field takeoff. A coiuple years ago, a heavily loaded Bonanza crashed after failing to climb..We (myself, several pilots (one a Bonanza owner), another instructor, a 30,000 pilot) all agree that the POH is wrong.. We watched video of the fatal takeoff attempt, and the consensus was that a notch of flaps would have saved the day.

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I should add, that some high-time engines end up with their torque curve altered a bit. If the engine's red-line is no longer the peak of that curve, then indeed a slightly lower RPM could yield more thrust,, because the twisting power being greater means that the blade pitch needed to "govern" that twisting force, could yield more thrust.. but this is not the norm (and probably a sign that an overhaul is called for)

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