So I'm in my Commercial Training and I'm flying the Piper Arrow. I'm having some difficulties understanding the prop system. It is to my knowledge that when the prop control lever is in the full forward position the airplane is producing the maximum power, High RPM, less oil in the prop, and a low/finer pitch(smaller bites of air)which makes the engine run faster due to less torque. My question is, if we get a low pitch(finer pitch) with the prop control full forward then why do we pull the prop control back to get less drag? I see people pulling the prop back in multi engine planes to feather the prop or people pulling the prop back on power off 180s to extend their glide range. If the propeller is at a finer pitch and taking smaller bites of air at the full forward position then it would be producing less drag because less of an angle of the propeller is running through the air. Right? Can somebody help me out and clarify? Thanks.
Prop System
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midwestpa24
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Imagine the blade is not spinning, but is stopped. Which will create more drag, the blade at fine pitch, at almost a right angle to the wind, or a feathered blade edge on into the wind.
Tom-D
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The prop blade pitch is like the threads on a bolt. fine threads, fine pitch, course threads course pitch. With course threads you will travel farther per revolution.
Fine pitch takes a lessor bite of air, = Less load = higher RPM, Higher RPM = more horse power. better climb etc.
Course Pitch takes a bigger bite of air, this is required at higher speeds, because of the lessor load.
The highest Pitch you can obtain is "Feathered" that is why we pull the prop leaver/knob, out when the engine is stopped.
Fine pitch takes a lessor bite of air, = Less load = higher RPM, Higher RPM = more horse power. better climb etc.
Course Pitch takes a bigger bite of air, this is required at higher speeds, because of the lessor load.
The highest Pitch you can obtain is "Feathered" that is why we pull the prop leaver/knob, out when the engine is stopped.
Croomrider
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Mike
If it's a constant speed prop you are referring to, you set the rpm with the blue knob and the pitch is automatically set by the prop governor depending on the torque/power of the engine. If the power of the motor is pulled back and the rpm is set high, you will have the wind turning to prop to the set rpm instead of the engine, which causes drag. Remember, in a constant speed prop, you don't set pitch, you set rpm, as long as there is enough power to maintain the rpm set.
Cap'n Jack
Final Approach
A caveat- I have no multi-engine experience.
However, I think you may be looking at two different phases of flight.
When the engine is producing power, setting a high pitch makes takes a bigger "bite" of the air (forward position)
Power off (or idle), feathering the prop reduces the drag since the air flow past the propeller causes drag trying to turn the prop. At low (or no) power settings, the engine isn't driving the propeller.
Croomrider's explanation is correct, I'm just attempting to look at it from another point of view.
GrahamC
Pre-Flight
It sounds like there's confusion in terminology to some degree.
I'm going to ask some straight forward questions and then answer them, as I hope you would.
How do you set POWER on the airplane? The throttle.
How do you control ENGINE SPEED? The Prop Control.
Simply, The propeller control does not affect engine power output. It may affect the amount of THRUST that the propeller produces, but Power is a function of the throttle setting.
The propeller is spinning through it's plane of rotation, generally perpendicular to the flight path of the airplane. If that blade has a very low profile relative to its plane of rotation (as it would at "Low Pitch-High RPM") then it must also have a very high profile relative to the flight path of the airplane. It therefore, creates more drag.
Conversely, If you bring the Propeller control back, and command a lower engine speed, the governor will (in most single engine airplanes) send oil to the propeller hub, moving the piston, which in this case increases the blade angle, presenting a HIGHER profile of the propeller relative to its plane of rotation resulting in a lower engine speed. At the same time, it's now presenting a relatively LOWER profile to the flight path of the airplane, resulting in less drag.
*The only edits made to this post have been to grammar and style. The content has not been altered*
I'm going to ask some straight forward questions and then answer them, as I hope you would.
How do you set POWER on the airplane? The throttle.
How do you control ENGINE SPEED? The Prop Control.
Simply, The propeller control does not affect engine power output. It may affect the amount of THRUST that the propeller produces, but Power is a function of the throttle setting.
The propeller is spinning through it's plane of rotation, generally perpendicular to the flight path of the airplane. If that blade has a very low profile relative to its plane of rotation (as it would at "Low Pitch-High RPM") then it must also have a very high profile relative to the flight path of the airplane. It therefore, creates more drag.
Conversely, If you bring the Propeller control back, and command a lower engine speed, the governor will (in most single engine airplanes) send oil to the propeller hub, moving the piston, which in this case increases the blade angle, presenting a HIGHER profile of the propeller relative to its plane of rotation resulting in a lower engine speed. At the same time, it's now presenting a relatively LOWER profile to the flight path of the airplane, resulting in less drag.
*The only edits made to this post have been to grammar and style. The content has not been altered*
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Don't confuse the poor guy more. Both manifold pressure and engine RPM are used to set power. Look at a power chart for any piston airplane with a CS prop and you'll see that the same power rating can obtained at various RPMs and manifold pressures.
GrahamC
Pre-Flight
Perhaps that statement could be interpreted as an oversimplification, but there is some distinction that needs to be made between the direct result of each control setting.
Yes- Performance charts have various MP/RPM settings, but the OP's statement directly relating Propeller control setting to Power needed to be addressed.
Yes- Performance charts have various MP/RPM settings, but the OP's statement directly relating Propeller control setting to Power needed to be addressed.
hindsight2020
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From a systems description and function, the OP may or may not know that CS props in twins and singles are usually spring loaded opposite of each other. So loss of oil in the hub (by blue knob manipulation or otherwise) yields coarse pitch in twins, and fine pitch in singles.
As to the aerodynamics:
Here's some pretty pictures to help you understand the difference forward motion makes in the aerodynamics of a propeller and effective angle of attack, which I suspect is what's tripping you up. To be concise: the forward component of aircraft velocity affects the angle of attack the propeller sees, and the blue knob is utilized to compensate for these losses as a function of the specific phase of flight (i.e. phases of flight with low forward velocity, vs phases of flight with high forward velocity, and the third case, windmilling/power loss/autorotation propeller aerodynamics). Happy reading!
As to the aerodynamics:
Here's some pretty pictures to help you understand the difference forward motion makes in the aerodynamics of a propeller and effective angle of attack, which I suspect is what's tripping you up. To be concise: the forward component of aircraft velocity affects the angle of attack the propeller sees, and the blue knob is utilized to compensate for these losses as a function of the specific phase of flight (i.e. phases of flight with low forward velocity, vs phases of flight with high forward velocity, and the third case, windmilling/power loss/autorotation propeller aerodynamics). Happy reading!
denverpilot
Tied Down
I'm going to answer the question you posed and remove all the systems stuff about HOW the lever does it, to see if it helps with visualization.
Think of the prop handle in grossly overly simplistic terms as a lever to set the angle of the prop. Full forward is flat, full back is angled back toward you.
Now spin the flat blades around. What does that look like to the oncoming air in front of the airplane if you were just idling? A big flat plate... a trash can lid... lots of drag when the relative air is pushing against that flat blade.
Now what does it look like when it's angled back toward you? A knife edge. The air can go right past it. In the extreme, "feathered". (Your Arrow prop won't fully feather, but it'll angle back toward you a whole lot.)
Disclaimer:
The above is a description to help you see the drag aspect, it's a bad way to describe the prop SYSTEM and the HOW part of how it works.
It also doesn't cover what happens when you add rotational power by pushing the throttle up. Then you're forcing the prop to go around faster, and the flat blades (fine pitch) can be accelerated easier vs trying to swing a sideways paddle (coarse pitch).
Another visualization for the no power scenario, think of being in a small boat on water and it's moving and you want to slow the boat down. If you stick the oar in the water knife edge, the boat will keep going nearly as fast as it is (coarse pitch, angled back toward you). Twist the oar flat, and the water hits the broad edge and slows you down, lots of drag (fine pitch, flat).
Help any?
I think that is more in line with what you were asking than the SYSTEMS answers about how it works that you're getting.
Think of the prop handle in grossly overly simplistic terms as a lever to set the angle of the prop. Full forward is flat, full back is angled back toward you.
Now spin the flat blades around. What does that look like to the oncoming air in front of the airplane if you were just idling? A big flat plate... a trash can lid... lots of drag when the relative air is pushing against that flat blade.
Now what does it look like when it's angled back toward you? A knife edge. The air can go right past it. In the extreme, "feathered". (Your Arrow prop won't fully feather, but it'll angle back toward you a whole lot.)
Disclaimer:
The above is a description to help you see the drag aspect, it's a bad way to describe the prop SYSTEM and the HOW part of how it works.
It also doesn't cover what happens when you add rotational power by pushing the throttle up. Then you're forcing the prop to go around faster, and the flat blades (fine pitch) can be accelerated easier vs trying to swing a sideways paddle (coarse pitch).
Another visualization for the no power scenario, think of being in a small boat on water and it's moving and you want to slow the boat down. If you stick the oar in the water knife edge, the boat will keep going nearly as fast as it is (coarse pitch, angled back toward you). Twist the oar flat, and the water hits the broad edge and slows you down, lots of drag (fine pitch, flat).
Help any?
I think that is more in line with what you were asking than the SYSTEMS answers about how it works that you're getting.
Its a constant speed prop (within limits, it varies in speed a bit in reality). That means if you pull the throttle back a bit, the prop govenor keeps the prop rotating at a constant speed (again, there will be a slight drop in rpm, but thats small). So the pitch of the prop is changing with throttle even if you dont change the prop knob.
For a single engine constant speed prop, when the power is pulled, the prop goes full flat for maximum drag. Its sort of like gearing in a car. When you go downhill, you will coast faster in high gear than in low gear. With a constant speed prop you will decelerate more when you pull the power back with the prop knob all the way in (low gear).
And twins have a different kind of constant speed prop than singles. They feather to full pitch (opposite of full flat) so they present the LEAST resistance to the wind and slow the plane down as little as possible. This is so the other engine can keep the planes airspeed up and help the plane fly on one engine.
Finally, you lean the engine with a constant speed prop the same way you lean with a fixed pitch prop. Pull the mixture back until you get an RPM drop, then richen a bit.
For a single engine constant speed prop, when the power is pulled, the prop goes full flat for maximum drag. Its sort of like gearing in a car. When you go downhill, you will coast faster in high gear than in low gear. With a constant speed prop you will decelerate more when you pull the power back with the prop knob all the way in (low gear).
And twins have a different kind of constant speed prop than singles. They feather to full pitch (opposite of full flat) so they present the LEAST resistance to the wind and slow the plane down as little as possible. This is so the other engine can keep the planes airspeed up and help the plane fly on one engine.
Finally, you lean the engine with a constant speed prop the same way you lean with a fixed pitch prop. Pull the mixture back until you get an RPM drop, then richen a bit.
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dmspilot
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Well, yes. But no. You are conflating two distinct ideas:
- rotational "drag", i.e. drag on the propeller with respect to its rotation
- drag on the airframe
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hindsight2020
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I know you were trying to help the OP visualize drag, but that description I'm afraid is not aerodynamically correct. The reason a windmilling prop has a lot of drag is not due to a higher frontal area of the blades facing the relative wind of the aircraft. You just merely described the parasitic (form drag) component of the physical blades when stopped in different angles towards the aircraft's relative wind. That contribution of drag is much much smaller than the aerodynamic (induced) drag contribution of an autorotating (windmilling) propeller blades, which implies of course their chordwise flow is not stalled and thus extracting work from the forward motion of the aircraft. This is multiples higher than the equivalent flat plate disc area's worth of parasite drag of the propeller arc. This is an often cited visualization, the suggestion that windmilling drag is equivalent to a solid disk's worth of parasite drag, with the same diameter as the prop. That is not an accurate representation of either the value of the drag force, nor the physical dynamics of the source of aerodynamic drag in a windmilling prop.
This nuance is illustrated here
Note the yuge/bigly differences in drag contribution between a windmilling prop and a stopped prop, specifically while the windmilling prop is not stalled (around the 20 degree mark or lower).
Now, the correct reason a windmilling prop in fine pitch creates so much drag, is the negative angle of attack resultant of the much much higher component of forward velocity on the part of the aircraft, versus the now unpowered prop and its greatly diminished rotational speed around the hub. The vector sum of this relationship yields a a propeller relative wind so slanted towards the RW of the aircraft that it creates said negative AOA on the propeller blades. The blades are not stalled however, not even close, and they are now lifting (thrusting) ....in the undesired direction. So lift is going the wrong way, bigly, the airfoil "drag" component of that lift resisting the rotational speed of the prop of course. The resultant steady state rotational windmilling RPM of the prop will be a function of the effective angle of attack, which is itself a function of BOTH the blade angle (if able to be manipulated by the pilot) and the forward velocity of the aircraft, aka no different than a conventional windmill. That aerodynamic explanation is compared below, with top illustration showing a propeller under engine power (aka rotational speed much more dominant than aircraft forward speed), and the bottom illustration a propeller under windmilling conditions. Make note of the angle of attack as the culprit in this dynamic, and how that explains the first graph regarding why a spinning windmilling propeller has so much undesired drag.
To reiterate, frontal area of a fine pitched blade against the aircraft relative wind is NOT the reason for drag increases in a windmilling prop, nor its effective flat plate area. It is the aerodynamic lift acting in the wrong direction while the blades have non-stalled chordwise flow that create the resistance you wished to describe for the OP. When the prop is stopped, then your "stick your paddle out at varying degrees" analogy would be correct.
I understand the oversimplification offered of demonstrating that higher frontal areas do in fact have higher parasitic drag, and getting it conflated with the aerodynamics of rotating propellers. It is a very common misrepresentation I used to fall for myself, until I got two degrees in aerospace engineering and they made me look at these things with so much detail that it made me hate it because I can't see the misprint and not have to post a dissertation of junior level subsonic propulsion aerodynamics 300 course. My apologies for the novel.
Now back to our regular programming of blowing the mind of the OP for daring to ask about pandora's box
James331
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It's been a while since i flew the arrow, but your point is pointless in the arrow
If you have a engine failure you're not going to be making good oil pressure, this the counterweights are going to put that prop into full forward regardless of what you do with that little blue knob.
But yeah, ideally in a engine failure you'd want to pull the prop back, think of taking one of those blade and pulling it through water, one you have the lever full forwards and more of the flat face of the blade presented to the wind, the other you have more of the edge of the blade presented to the relative wind, the one with more edge than face is going to be easer to pull through water right?
Again, in the arrow in a real engine failure it's going to default full forward, so mute point.
If you have a engine failure you're not going to be making good oil pressure, this the counterweights are going to put that prop into full forward regardless of what you do with that little blue knob.
But yeah, ideally in a engine failure you'd want to pull the prop back, think of taking one of those blade and pulling it through water, one you have the lever full forwards and more of the flat face of the blade presented to the wind, the other you have more of the edge of the blade presented to the relative wind, the one with more edge than face is going to be easer to pull through water right?
Again, in the arrow in a real engine failure it's going to default full forward, so mute point.
MAKG1
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This is backwards. To a decent approximation, engine power is RPM*MP. If you want to make rules of thumb, RPM is how fast you spin the prop, MP is how hard you push each rotation. Power is the product of the two.
MAKG1
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Not true.
Some types of failures spill all the oil overboard, and then the blue knob/handle doesn't work. But MOST of them do not. The single biggest cause of engine failure is fuel starvation, and a windmilling prop will make the same oil pressure as a powered prop will at the same RPM. Then, you have no problem pulling the knob backwards.
James331
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Not [always] true
I agree, if you have a failure try to pull her back, just don't always plan on having that ability.
In my case, all the oil was rapidly leaving the engine. However, I didn't give much thought to trying to pseudo feather the prop. I was going down.
labbadabba
Pattern Altitude
It takes a bigger bite when spinning due the AoA of the propeller blade. When it's not spinning, the AoA is altered by nearly 90 degrees. When you feather the prop, it turns the prop into the the wind and decreases the AoA and thus drag.
GrahamC
Pre-Flight
Perhaps I could clarify further. My previous statement is now clearly and unequivocally over simplified. I would not however characterize it as "backwards." If you're in level flight and wish do begin a descent- in order to reduce the power produced by the engine, would you reduce the propeller control or the throttle? If you mean to say that you set power with the propeller control, then we should start another thread to continue that discussion. I'm not intending to define the different kinds of power that an engine can be measured by. Rather, I'm trying to address what seemed like a misunderstanding by the OP in his first post.
MAKG1
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If power were the only issue, you could reduce it with the prop control.
However, RPM controls the lubrication system, and low RPM/high throttle increases cylinder temperatures, making detonation a problem. For those other reasons, you use throttle rather than prop.
Now, if you can find an "approved" combination in the performance tables, you can indeed lower RPM to lower power, while leaving the throttle alone. But in general, the combinations are only available for small changes.
GrahamC
Pre-Flight
It doesn't seem like we're going to come to a middle ground here. Suffice it to say that in every plain language instructional resource that I've seen the FAA put out, Throttle is described as controlling Power, while Prop Control is described as controlling Engine RPM. Is power ever truly constant? No. But for the purposes of this discussion, I don't think we need to start throwing out the formulas for calculating three different kinds of power.
To Lazy, If you're still even reading this, I hope we haven't confused you too much. I try to put things in more simple terms- and while its not usually the whole picture, it does the trick. Best of luck in your commercial training.
To Lazy, If you're still even reading this, I hope we haven't confused you too much. I try to put things in more simple terms- and while its not usually the whole picture, it does the trick. Best of luck in your commercial training.
MAKG1
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Perhaps not, but if the prop setting doesn't affect power, why do you suppose we push the prop full forward for takeoff and go-around? Why not just cram the throttle in like we do for fixed pitch?
You also should refer to your favorite airplane's performance charts. You'll quickly discover that higher RPM at fixed MP yields more true airspeed, more %power, and higher fuel flow (if the mixture is also left fixed). Properly leaned fuel flow is directly proportional to engine power being produced at that instant, at a rate of about 0.5 lb/hr/HP (slightly less for 100 octane, slightly more for 87 due to the detonation limit).
Your problem is that you're using a colloquial use of the term "power," which isn't correct. It has a very specific meaning. Actually two of them in this context (neither of which is controlled purely by throttle).
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GlennAB1
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Variable pitch propeller aircraft I'm familiar with have a standpipe in the oil tank which reserves a quantity of oil solely for prop feathering.
In the Gulfstream 1 accident I posted in "Lessons Learned", had the crew manually feathered #1 engine, and not armed water meth, they may have had a different outcome.
I like this explanation. Lengthy, but reasonably correct.
https://www.advancedpilot.com/downloads/prep.pdf
https://www.advancedpilot.com/downloads/prep.pdf
denverpilot
Tied Down
I know you were trying to help the OP visualize drag, but that description I'm afraid is not aerodynamically correct. The reason a windmilling prop has a lot of drag is not due to a higher frontal area of the blades facing the relative wind of the aircraft. You just merely described the parasitic (form drag) component of the physical blades when stopped in different angles towards the aircraft's relative wind. That contribution of drag is much much smaller than the aerodynamic (induced) drag contribution of an autorotating (windmilling) propeller blades, which implies of course their chordwise flow is not stalled and thus extracting work from the forward motion of the aircraft. This is multiples higher than the equivalent flat plate disc area's worth of parasite drag of the propeller arc. This is an often cited visualization, the suggestion that windmilling drag is equivalent to a solid disk's worth of parasite drag, with the same diameter as the prop. That is not an accurate representation of either the value of the drag force, nor the physical dynamics of the source of aerodynamic drag in a windmilling prop.
This nuance is illustrated here
View attachment 51635
Note the yuge/bigly differences in drag contribution between a windmilling prop and a stopped prop, specifically while the windmilling prop is not stalled (around the 20 degree mark or lower).
Now, the correct reason a windmilling prop in fine pitch creates so much drag, is the negative angle of attack resultant of the much much higher component of forward velocity on the part of the aircraft, versus the now unpowered prop and its greatly diminished rotational speed around the hub. The vector sum of this relationship yields a a propeller relative wind so slanted towards the RW of the aircraft that it creates said negative AOA on the propeller blades. The blades are not stalled however, not even close, and they are now lifting (thrusting) ....in the undesired direction. So lift is going the wrong way, bigly, the airfoil "drag" component of that lift resisting the rotational speed of the prop of course. The resultant steady state rotational windmilling RPM of the prop will be a function of the effective angle of attack, which is itself a function of BOTH the blade angle (if able to be manipulated by the pilot) and the forward velocity of the aircraft, aka no different than a conventional windmill. That aerodynamic explanation is compared below, with top illustration showing a propeller under engine power (aka rotational speed much more dominant than aircraft forward speed), and the bottom illustration a propeller under windmilling conditions. Make note of the angle of attack as the culprit in this dynamic, and how that explains the first graph regarding why a spinning windmilling propeller has so much undesired drag.
View attachment 51641
To reiterate, frontal area of a fine pitched blade against the aircraft relative wind is NOT the reason for drag increases in a windmilling prop, nor its effective flat plate area. It is the aerodynamic lift acting in the wrong direction while the blades have non-stalled chordwise flow that create the resistance you wished to describe for the OP. When the prop is stopped, then your "stick your paddle out at varying degrees" analogy would be correct.
I understand the oversimplification offered of demonstrating that higher frontal areas do in fact have higher parasitic drag, and getting it conflated with the aerodynamics of rotating propellers. It is a very common misrepresentation I used to fall for myself, until I got two degrees in aerospace engineering and they made me look at these things with so much detail that it made me hate it because I can't see the misprint and not have to post a dissertation of junior level subsonic propulsion aerodynamics 300 course. My apologies for the novel.
Now back to our regular programming of blowing the mind of the OP for daring to ask about pandora's box
I understand and appreciate the description, but you probably just confused the hell out of the student forever with that. LOL.
denverpilot
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Interesting. Never seen one. How would it retain the oil if the tank drained? Filled by gravity from the top?
GlennAB1
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There's no provision in case of complete oil tank draining in flight. I think that's of lowest probability.
GlennAB1
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Maybe that wasn't clear. Normal oil feed from the tank is taken through a standpipe. Oil for propeller feathering is taken from below the level of the standpipe. The standpipe ensures an adequate feathering reserve.
LongRoadBob
Cleared for Takeoff
I know you were trying to help the OP visualize drag, but that description I'm afraid is not aerodynamically correct. The reason a windmilling prop has a lot of drag is not due to a higher frontal area of the blades facing the relative wind of the aircraft. You just merely described the parasitic (form drag) component of the physical blades when stopped in different angles towards the aircraft's relative wind. That contribution of drag is much much smaller than the aerodynamic (induced) drag contribution of an autorotating (windmilling) propeller blades, which implies of course their chordwise flow is not stalled and thus extracting work from the forward motion of the aircraft. This is multiples higher than the equivalent flat plate disc area's worth of parasite drag of the propeller arc. This is an often cited visualization, the suggestion that windmilling drag is equivalent to a solid disk's worth of parasite drag, with the same diameter as the prop. That is not an accurate representation of either the value of the drag force, nor the physical dynamics of the source of aerodynamic drag in a windmilling prop.
This nuance is illustrated here
View attachment 51635
Note the yuge/bigly differences in drag contribution between a windmilling prop and a stopped prop, specifically while the windmilling prop is not stalled (around the 20 degree mark or lower).
Now, the correct reason a windmilling prop in fine pitch creates so much drag, is the negative angle of attack resultant of the much much higher component of forward velocity on the part of the aircraft, versus the now unpowered prop and its greatly diminished rotational speed around the hub. The vector sum of this relationship yields a a propeller relative wind so slanted towards the RW of the aircraft that it creates said negative AOA on the propeller blades. The blades are not stalled however, not even close, and they are now lifting (thrusting) ....in the undesired direction. So lift is going the wrong way, bigly, the airfoil "drag" component of that lift resisting the rotational speed of the prop of course. The resultant steady state rotational windmilling RPM of the prop will be a function of the effective angle of attack, which is itself a function of BOTH the blade angle (if able to be manipulated by the pilot) and the forward velocity of the aircraft, aka no different than a conventional windmill. That aerodynamic explanation is compared below, with top illustration showing a propeller under engine power (aka rotational speed much more dominant than aircraft forward speed), and the bottom illustration a propeller under windmilling conditions. Make note of the angle of attack as the culprit in this dynamic, and how that explains the first graph regarding why a spinning windmilling propeller has so much undesired drag.
View attachment 51641
To reiterate, frontal area of a fine pitched blade against the aircraft relative wind is NOT the reason for drag increases in a windmilling prop, nor its effective flat plate area. It is the aerodynamic lift acting in the wrong direction while the blades have non-stalled chordwise flow that create the resistance you wished to describe for the OP. When the prop is stopped, then your "stick your paddle out at varying degrees" analogy would be correct.
I understand the oversimplification offered of demonstrating that higher frontal areas do in fact have higher parasitic drag, and getting it conflated with the aerodynamics of rotating propellers. It is a very common misrepresentation I used to fall for myself, until I got two degrees in aerospace engineering and they made me look at these things with so much detail that it made me hate it because I can't see the misprint and not have to post a dissertation of junior level subsonic propulsion aerodynamics 300 course. My apologies for the novel.
Now back to our regular programming of blowing the mind of the OP for daring to ask about pandora's box
Wow...great reply. At least I think it is. I have to reread it (yet again) slowly (I may even be mouthing the words here and there) and plan on rereading a number of times to make sure I have the many points you are hitting here. I very much appreciate posts like this, as a student. There was a similar one for oil pressure in a thread where someone took the time to really go into detail. This is some great stuff...
Just wondering what the "RW" stands for?
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hindsight2020
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Relative wind.
Dave S.
Pre-takeoff checklist
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- Feb 28, 2017
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thetexan
As you reason this out remember that the prop setting is not "producing more power" so to speak. The prop is transferring power from the engine into the atmospheric medium. The engine is producing the power and the prop transfers the power. Therefore the prop should be analyzed in terms of its effectiveness in transferring the power from the power producing engine for the given task at hand. Ask yourself how prop angle changes the effectiveness of the power transfer (for any given MP).
tex
tex
MAKG1
Touchdown! Greaser!
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- Jun 19, 2012
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MAKG
No, the engine spinning faster at the same throttle really is producing more power. There may also be an efficiency factor, but that's just how engines work.