Paradox of constant speed propeller
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Paradox of constant speed propeller
Hello fellow aviators!
I am quite confused by the principle of constant speed/variable pitch propeller for awhile. After a few days of research I have a good idea about its' purpose and how to achieve it.
But, I don't understand why do we have to have a "rev-up, throttle back" principle.
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
And how do we know if that RPM setting is optimal?
Also, it's saying that propeller setting controls RPM, throttle control MP.
How come when I increase throttle, MP increases, but RPM constant because of the governor? What's next after MP increases? Crankshaft connected to cylinder rotates faster to gearbox, and the gearbox eventually lower the rotation so RPM doesn't increase?
Thank you very much for your professional helping!
Cheers!
I am quite confused by the principle of constant speed/variable pitch propeller for awhile. After a few days of research I have a good idea about its' purpose and how to achieve it.
But, I don't understand why do we have to have a "rev-up, throttle back" principle.
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
And how do we know if that RPM setting is optimal?
Also, it's saying that propeller setting controls RPM, throttle control MP.
How come when I increase throttle, MP increases, but RPM constant because of the governor? What's next after MP increases? Crankshaft connected to cylinder rotates faster to gearbox, and the gearbox eventually lower the rotation so RPM doesn't increase?
Thank you very much for your professional helping!
Cheers!
I'm sure someone will be along with a better explanation but, for the moment:
On poppet valve engines it is normal to increase RPM then boost, throttle or MP.
I believe that his is to prevent overboosting and overheating of the exhaust valves.
When reducing RPM then reduce MP first.
An exception, in my experience, is the Bristol Hercules sleeve valve radial engines where we did the opposite and increased boost then RPM.
As you increase MP, the prop pitch will coarsen in order to absorb the greater power and produce more thrust.
Re optimal settings: there should be guidance in the flight manual.
The plus point, when you make it onto the Dreamliner, is that you don't have to worry about all that stuff
On poppet valve engines it is normal to increase RPM then boost, throttle or MP.
I believe that his is to prevent overboosting and overheating of the exhaust valves.
When reducing RPM then reduce MP first.
An exception, in my experience, is the Bristol Hercules sleeve valve radial engines where we did the opposite and increased boost then RPM.
As you increase MP, the prop pitch will coarsen in order to absorb the greater power and produce more thrust.
Re optimal settings: there should be guidance in the flight manual.
The plus point, when you make it onto the Dreamliner, is that you don't have to worry about all that stuff
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The point of a constant speed propeller is to get maximum efficiency throughout the full range of speeds and power of the aircraft.
If you increase the MP, you increase the power output of the engine, thus the propeller turns faster. The propeller governor (which has nothing to do with a gearbox) detects this, and increases the pitch of the propeller blades. Your blades now have a higher angle of attack, which means more drag, thus reducing the speed of the propeller back to initial value (constant speed). It also means more lift, which gives you thrust on a propeller. You therefore have an increased thrust, which was the initial point of increasing power.
If you have an important manifold pressure, with low RPM (Low RPM means blades have a very high angle of attack, and thus very high drag.), you will exceed the maximum torque supported by the crankshaft and could damage the engine.
If you want an increase in thrust, you must increase the RPM before the MP so that you do not exceed max torque, and the opposite when reducing power, for the same reason.
How come when I increase throttle, MP increases, but RPM constant because of the governor? What's next after MP increases? Crankshaft connected to cylinder rotates faster to gearbox, and the gearbox eventually lower the rotation so RPM doesn't increase?
But, I don't understand why do we have to have a "rev-up, throttle back" principle.
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
If you want an increase in thrust, you must increase the RPM before the MP so that you do not exceed max torque, and the opposite when reducing power, for the same reason.
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While larger engines may have a gearbox to reduce the prop rpm (and thus tip speed), the gears are a fixed ratio (generally between 0.40 and 0.75) and can be ignored when studying the governor operation.
The biggest effect of the governor can be felt whenever the IAS is changing. If you set e.g. 2400 rpm at start of TO roll, and keep the nose down and let the aircraft accelerate to whatever its max IAS may be, the engine will still be turning 2400 rpm. Similarly during aerobatics.
Another note - the tachometer on the panel shows ENGINE rpm; if a geared engine, the prop rpm will be slower than the tach reading.
The biggest effect of the governor can be felt whenever the IAS is changing. If you set e.g. 2400 rpm at start of TO roll, and keep the nose down and let the aircraft accelerate to whatever its max IAS may be, the engine will still be turning 2400 rpm. Similarly during aerobatics.
Another note - the tachometer on the panel shows ENGINE rpm; if a geared engine, the prop rpm will be slower than the tach reading.
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I think you're getting your gearboxes mixed up. A CS prop doesn't have a gearbox, it has bob weights that move with relation to prop speed. There's only a limited amount of movement which is why at low throttle openings the prop spins slowly rather than at 2400rpm or whatever you have selected.
I fly a 182 and on take off it's full throttle and fine pitch; get off the ground to a safe height and back to 23 inches on the manifold and 2450 rpm, however the rpm will be at around 2450 anyway so basically you just leave the prop where it is for climb. Cruise is whatever you want although I fly at 22 squared which is 22 inches manifold and 2200 rpm, reducing the manifold first. This gives around 120 kts depending on weight.
The descent is where you have to plan ahead a bit. Reduce manifold pressure an inch and start a 500' minute descent. Every minute reduce the manifold pressure by one inch. Eventually you will get to the point where the prop has reached it's stops and the rpm will start to fall. If you plan this correctly you should just be turning downwind and you know it's safe to go full fine on the prop which is what you want at this point.
The prop control isn't something that's fiddled with throughout the flight, on a normal A to B flight you would probably touch it twice.
The simple way to remember the sequence is PTTP. Power ie an increase in power is pitch then throttle. Decrease in power is throttle then pitch.
You can really feel the effect of a CS prop on a touch and go; normally on a fixed pitch prop say a 172 you feel the the power come, stick in a little right boot and lift it off. On a 182 especially if it's light once you hit around 45 kts there's a real kick in the back as the prop starts to work at it's optimum, you can certainly feel those 235 hp.
I fly a 182 and on take off it's full throttle and fine pitch; get off the ground to a safe height and back to 23 inches on the manifold and 2450 rpm, however the rpm will be at around 2450 anyway so basically you just leave the prop where it is for climb. Cruise is whatever you want although I fly at 22 squared which is 22 inches manifold and 2200 rpm, reducing the manifold first. This gives around 120 kts depending on weight.
The descent is where you have to plan ahead a bit. Reduce manifold pressure an inch and start a 500' minute descent. Every minute reduce the manifold pressure by one inch. Eventually you will get to the point where the prop has reached it's stops and the rpm will start to fall. If you plan this correctly you should just be turning downwind and you know it's safe to go full fine on the prop which is what you want at this point.
The prop control isn't something that's fiddled with throughout the flight, on a normal A to B flight you would probably touch it twice.
The simple way to remember the sequence is PTTP. Power ie an increase in power is pitch then throttle. Decrease in power is throttle then pitch.
You can really feel the effect of a CS prop on a touch and go; normally on a fixed pitch prop say a 172 you feel the the power come, stick in a little right boot and lift it off. On a 182 especially if it's light once you hit around 45 kts there's a real kick in the back as the prop starts to work at it's optimum, you can certainly feel those 235 hp.
Last edited by thing; 16th Aug 2013 at 03:03.
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I think you're getting your gearboxes mixed up. A CS prop doesn't have a gearbox, it has bob weights that move with relation to prop speed.
I would love to see the results if the prop on any TP engine was allowed to run at non-geared engine speed
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I distinctly recall the OP talking about cylinders and crankshafts ...
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Just to clear up any confusion, I was talking about the prop mechanism, it most definitely isn't a 'gearbox'. I assumed from the OP's original post he was talking about SEPs, apologies if I was mistaken.
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You can really feel the effect of a CS prop on a touch and go; normally on a fixed pitch prop say a 172 you feel the the power come, stick in a little right boot and lift it off. On a 182 especially if it's light once you hit around 45 kts there's a real kick in the back as the prop starts to work at it's optimum, you can certainly feel those 235 hp.
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Originally Posted by GearDownThreeGreen
And to say that a CS prop does not have a gearbox is very often wrong.
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A Squared: It is a bit heavier than a 172 but I take your point. I'm referring to the sweet point on the prop pitch/RPM/IAS where the prop really starts to bite. There's a noticeable surge in 'oomph' around 45-50 kts. I fly a 172 as well and there's certainly a difference in prop response at certain speeds, nothing to do with the extra 55 hp, (where do you get 50% extra power from?) which is as it should be otherwise there would be no point in having a CS prop, other than it's a damn sight quieter in the cruise than a fixed pitch.
Edit: Error on my part, the 182 has a 230 hp donk so an extra 50 hp.
Edit: Error on my part, the 182 has a 230 hp donk so an extra 50 hp.
Last edited by thing; 17th Aug 2013 at 02:13.
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where do you get 50% extra power from?
182 = 230
230-150= 80
80/150 = 0.533 = 53%
I'm sure that you can point to 172 which have other than 150 hp and 182's with other then 230, but there's a whole bunch with those numbers. Anyway, the point is, generally the 182 has a higher power to weight ratio than the 172.
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Not disputing that, just that the acceleration is not constant on take off. I know that it isn't in a fixed prop either, it's just more noticeable (to me anyway) in a CS a/c. Maybe I have a sensitive seat of the pants. Have you never noticed the surge you get at take off at around 45 knots in a 182 as compared to a 172 ?
The 172 I fly has the A3A donk at 180 hp.
The 172 I fly has the A3A donk at 180 hp.
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I would suggest that the surge you feel is not the prop "really biting" as the efficiency of a constant speed prop plots as a fairly constant curve. ie: no airspeed/rpm/etc regimes where it is dramatically more efficient at producing thrust. Additionally, the prop installed on a stock 182 is most leikely going to be one which is most efficient in the cruise regime (vs the aftermarket seaplane prop on my C-180 which is optimized for low speed thrust)
Rather the difference in push you feel is due to the fact that the constant speed prop allows the engine to turn up to max RPM (and thus produce max power) at low airspeeds, vs the fixed pitch prop where at low airspeeds the engine RPM is necessarily low, and thus power output is also well below max. A fixed pitch prop airplane will not produce max rated power until such time as the airspeed is high enough to allow the RPM to increase to redline. Unless you have a very flat pitch prop, that probably isn't going to happen on the takeoff roll.
Rather the difference in push you feel is due to the fact that the constant speed prop allows the engine to turn up to max RPM (and thus produce max power) at low airspeeds, vs the fixed pitch prop where at low airspeeds the engine RPM is necessarily low, and thus power output is also well below max. A fixed pitch prop airplane will not produce max rated power until such time as the airspeed is high enough to allow the RPM to increase to redline. Unless you have a very flat pitch prop, that probably isn't going to happen on the takeoff roll.
For what it's worth; just a non-technical thought from when I used to fly turbo-props:
I think of the prop pitch being like the gears on a car. To start off, or go 'uphill' you need a low gear (fine pitch). To cruise along the 'motorway' you use a high gear (coarse pitch).
On approach to land, you need fine pitch again just in case you need to go around and climb.
As others have said; a constant speed system keeps the prop RPM constant and varies the blade pitch according to how much power the engine is producing. Turbo props generally have two propeller RPM settings - fast for take-off and fine pitch, slower for the cruise.
I think of the prop pitch being like the gears on a car. To start off, or go 'uphill' you need a low gear (fine pitch). To cruise along the 'motorway' you use a high gear (coarse pitch).
On approach to land, you need fine pitch again just in case you need to go around and climb.
As others have said; a constant speed system keeps the prop RPM constant and varies the blade pitch according to how much power the engine is producing. Turbo props generally have two propeller RPM settings - fast for take-off and fine pitch, slower for the cruise.
Basil.
Hercules 264, Lollipops before Crinkly Chips' to increase power and vice versa to decrease power . Sleeve valve engine, though I never got a good explanation as to "why". Was it to prevent chatter' on the sleeve valve mechanism?
Hercules 264, Lollipops before Crinkly Chips' to increase power and vice versa to decrease power . Sleeve valve engine, though I never got a good explanation as to "why". Was it to prevent chatter' on the sleeve valve mechanism?
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Dreamlinerwannabe
The reason for the change in speed before increase in manifold pressure is to ensure the engine doesn't detonate with the increase in BMEP. This is often refered to as "OverBoosting" the engine - but it can also occur in normally aspirated engines as well.
You can easily achieve detonation in a motor car with a manual transmission - with a slow speed in a high gear push the throttle all the way open and you will hear - and sometimes feel - the engine "Ping". This is detonation and it is very destructive to aircraft engines.
Below is an excerpt from the Pratt & Whitney Engine Operation Manual 01 - 100 that was used in training during WWII.
Page 27 - 29
DETONATION
Normal combustion is rapid, but it is by no
means an instantaneous explosion. The charge
burns evenly and smoothly, the flame front advancing
at a measurable rate-about 35 feet per
second when combustion begins, increasing to
roughly 150 feet per second, and finally slowing
down as the process nears completion.
If sufficiently heated and compressed, any
combustible mixture of gasoline vapor and air
will catch fire. Accordingly, if the temperature
and pressure of the unburned portion of the fuel-air
charge reach critical values, combustion
will begin spontaneously and simultaneously
throughout the unburned charge. The result is
a sudden and violent explosion known as detonation.
Detonation occurs so quickly that even high
speed cameras, which slow down normal combustion
to a snail's pace, fail to retard its progress
sufficiently for exact analysis. It is accompanied
by an abrupt pressure rise and violent
pressure fluctuations of extreme rapidity. The
engine is unable to turn into useful work energy
so explosively released. The recurring shock
pressures are carried to piston, cylinder, and
hold-down studs, and the fatigue stresses set up
in the materials quickly lead to the failure of
these parts.
Detonation also causes a rapid rise in cylinder
temperatures, and thereby aggravates the very
conditions which produced it. These high temperatures
can rapidly destroy the piston, cylinder
head, exhaust valve and guide, and damage
other parts by burning and erosion.
Similar in its results to detonation, and frequently
accompanied by it, is pre-ignition. The
latter is caused by uncontrolled ignition of the
charge ahead of the normal flame front, because
of contact with some "hot spot" in the combustion
chamber, such as an incandescent spark
plug. As a result the timing is too far advanced;
the engine loses power and overheats ; local temperatures
at the hot spot rise rapidly; and the
engine may be damaged, if it is not quickly
stopped.
Detonation-free operation is altogether normal
and entirely possible over the full range
of rated engine performance, even under the
most adverse conditions. Nevertheless, detonation
is the most likely as well as the most destructive of
the possible consequences of improper engine operation.
CONDITIONS LEADING TO DETONATION
Among the conditions which may lead to detonation
the most important are :
1. Excessive manifold pressure. As manifold
pressure is increased, so is the pressure of
the charge entering the cylinders. The latter
is multiplied many times during compression
and combustion, and, if the initial pres-
sure of the charge is too great, a critical
value may be reached which will result in
detonation. Excessive manifold pressure may
be caused by too wide a throttle opening or,
on some engines, by the use of too great a
degree of supercharging.
2. Excessive carburetor air temperature (c.a.t).
As the temperature of the charge air at the
carburetor is increased, so is the temperature
of the fuel-air mixture entering the cylinders.
The latter is further raised during compression
and combustion, and, ' if the initial
temperature of the charge is too high, a critical
value may be reached which will also
result in detonation. Hot "free air" entering
the induction system, inadequate inter-cooling
in the case of multiple stage superchargers
or too much carburetor pre-heat, may
cause excessive c.a.t. High impeller speeds,
the consequence of high engine rpm or of
improper operation in the "high" impeller
gear ratio, will cause a sharp heat rise -
through the supercharger, and, as a result,
the charge will not be sufficiently cool when
delivered to the cylinders.
3. Excessive cylinder head temperatures. The
temperature and, indirectly, the pressure of
the unburned portion of the charge may be
raised to critical values as a result of excessive
cylinder head temperatures alone.
4. Improper grade of fuel. If the fuel used has
an anti-knock rating (i.e., resistance to detonation)
lower than that called for by the rating
of the engine, detonation will follow any
attempt to operate in the high power range.
5. Malfunctioning of the ignition system:
Whenever the engine is operated in the high
power range, detonation is likely to occur if
the timing of the spark is too far advanced.
It may also occur during high power operation
in a cylinder where only one of the two
plugs is functioning.
6. Lean Mixtures. The tendency to detonate
varies with the fuel-air ratio, and mixtures
at or near best power are the ones most
likely to detonate. Combustion chamber
temperatures may be lowered most effectively,
and detonation thereby most readily
inhibited by enriching the mixture beyond
the best power setting.
Detonation imposes one of the most important
limitations on engine performance, and the operator
must at all times so control conditions as to
avoid any which might lead to detonation and
the consequent damage to his powerplant.
Page 101
TRANSITION FROM TAKE-OFF
TO CLIMB
As soon as the field and surrounding obstacles
are cleared, reduce power at least to
Normal Rated. With constant speed (variable
pitch) propellers the reduction should be accomplished
in steps as follows:
1. Retard throttle to reduce manifold pressure
to about 2 in. Hg below that for Normal
Rated power (with fixed part throttle,
manifold pressure will rise as rpm is reduced).
2. Retard the rpm control to Normal Rated
rpm.
If a further reduction in power is desired,
proceed as follows:
1. Lower manifold pressure by 2 in. Hg.
2. Lower engine speed by 200 rpm.
Continue in successive alternate steps until
the desired engine speed is reached, finally adjusting
the throttle to the desired manifold pressure.
This is not to be construed to mean that the throttle
should never be advanced with a low rpm. The engine -
is not affected by the position of the throttle.
It is affected by the manifold pressure resulting from the
throttle position.
Bold and Italics for emphasis are mine.
Hope this helps
But, I don't understand why do we have to have a "rev-up, throttle back" principle.
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
And how do we know if that RPM setting is optimal?
Also, it's saying that propeller setting controls RPM, throttle control MP.
Why do we have to do this? Why sometimes we have to select RPM first, then MP?
And how do we know if that RPM setting is optimal?
Also, it's saying that propeller setting controls RPM, throttle control MP.
You can easily achieve detonation in a motor car with a manual transmission - with a slow speed in a high gear push the throttle all the way open and you will hear - and sometimes feel - the engine "Ping". This is detonation and it is very destructive to aircraft engines.
Below is an excerpt from the Pratt & Whitney Engine Operation Manual 01 - 100 that was used in training during WWII.
Page 27 - 29
DETONATION
Normal combustion is rapid, but it is by no
means an instantaneous explosion. The charge
burns evenly and smoothly, the flame front advancing
at a measurable rate-about 35 feet per
second when combustion begins, increasing to
roughly 150 feet per second, and finally slowing
down as the process nears completion.
If sufficiently heated and compressed, any
combustible mixture of gasoline vapor and air
will catch fire. Accordingly, if the temperature
and pressure of the unburned portion of the fuel-air
charge reach critical values, combustion
will begin spontaneously and simultaneously
throughout the unburned charge. The result is
a sudden and violent explosion known as detonation.
Detonation occurs so quickly that even high
speed cameras, which slow down normal combustion
to a snail's pace, fail to retard its progress
sufficiently for exact analysis. It is accompanied
by an abrupt pressure rise and violent
pressure fluctuations of extreme rapidity. The
engine is unable to turn into useful work energy
so explosively released. The recurring shock
pressures are carried to piston, cylinder, and
hold-down studs, and the fatigue stresses set up
in the materials quickly lead to the failure of
these parts.
Detonation also causes a rapid rise in cylinder
temperatures, and thereby aggravates the very
conditions which produced it. These high temperatures
can rapidly destroy the piston, cylinder
head, exhaust valve and guide, and damage
other parts by burning and erosion.
Similar in its results to detonation, and frequently
accompanied by it, is pre-ignition. The
latter is caused by uncontrolled ignition of the
charge ahead of the normal flame front, because
of contact with some "hot spot" in the combustion
chamber, such as an incandescent spark
plug. As a result the timing is too far advanced;
the engine loses power and overheats ; local temperatures
at the hot spot rise rapidly; and the
engine may be damaged, if it is not quickly
stopped.
Detonation-free operation is altogether normal
and entirely possible over the full range
of rated engine performance, even under the
most adverse conditions. Nevertheless, detonation
is the most likely as well as the most destructive of
the possible consequences of improper engine operation.
CONDITIONS LEADING TO DETONATION
Among the conditions which may lead to detonation
the most important are :
1. Excessive manifold pressure. As manifold
pressure is increased, so is the pressure of
the charge entering the cylinders. The latter
is multiplied many times during compression
and combustion, and, if the initial pres-
sure of the charge is too great, a critical
value may be reached which will result in
detonation. Excessive manifold pressure may
be caused by too wide a throttle opening or,
on some engines, by the use of too great a
degree of supercharging.
2. Excessive carburetor air temperature (c.a.t).
As the temperature of the charge air at the
carburetor is increased, so is the temperature
of the fuel-air mixture entering the cylinders.
The latter is further raised during compression
and combustion, and, ' if the initial
temperature of the charge is too high, a critical
value may be reached which will also
result in detonation. Hot "free air" entering
the induction system, inadequate inter-cooling
in the case of multiple stage superchargers
or too much carburetor pre-heat, may
cause excessive c.a.t. High impeller speeds,
the consequence of high engine rpm or of
improper operation in the "high" impeller
gear ratio, will cause a sharp heat rise -
through the supercharger, and, as a result,
the charge will not be sufficiently cool when
delivered to the cylinders.
3. Excessive cylinder head temperatures. The
temperature and, indirectly, the pressure of
the unburned portion of the charge may be
raised to critical values as a result of excessive
cylinder head temperatures alone.
4. Improper grade of fuel. If the fuel used has
an anti-knock rating (i.e., resistance to detonation)
lower than that called for by the rating
of the engine, detonation will follow any
attempt to operate in the high power range.
5. Malfunctioning of the ignition system:
Whenever the engine is operated in the high
power range, detonation is likely to occur if
the timing of the spark is too far advanced.
It may also occur during high power operation
in a cylinder where only one of the two
plugs is functioning.
6. Lean Mixtures. The tendency to detonate
varies with the fuel-air ratio, and mixtures
at or near best power are the ones most
likely to detonate. Combustion chamber
temperatures may be lowered most effectively,
and detonation thereby most readily
inhibited by enriching the mixture beyond
the best power setting.
Detonation imposes one of the most important
limitations on engine performance, and the operator
must at all times so control conditions as to
avoid any which might lead to detonation and
the consequent damage to his powerplant.
Page 101
TRANSITION FROM TAKE-OFF
TO CLIMB
As soon as the field and surrounding obstacles
are cleared, reduce power at least to
Normal Rated. With constant speed (variable
pitch) propellers the reduction should be accomplished
in steps as follows:
1. Retard throttle to reduce manifold pressure
to about 2 in. Hg below that for Normal
Rated power (with fixed part throttle,
manifold pressure will rise as rpm is reduced).
2. Retard the rpm control to Normal Rated
rpm.
If a further reduction in power is desired,
proceed as follows:
1. Lower manifold pressure by 2 in. Hg.
2. Lower engine speed by 200 rpm.
Continue in successive alternate steps until
the desired engine speed is reached, finally adjusting
the throttle to the desired manifold pressure.
This is not to be construed to mean that the throttle
should never be advanced with a low rpm. The engine -
is not affected by the position of the throttle.
It is affected by the manifold pressure resulting from the
throttle position.
Bold and Italics for emphasis are mine.
Hope this helps
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Dreamlinerwannabe
Quote from Basil
"The plus point, when you make it onto the Dreamliner, is that you don't have to worry about all that stuff
"
Actually you still have a constant speed propeller in the form of a RAT on the 787.
You won't have to worry about manifold pressure or propeller pitch control unless they further develop a variable pitch fan.
Variable pitch turbofan : Patent US3946554 - Variable pitch turbofan engine and a method for operating same - Google Patents
A good read here for operation of the 787 RAT:
Boeing 787: A Pilots Perspective
The Rat Part!!
If 3 of the 4 engine drive generators fail in flight, the APU will start automatically. Two APU generators can be operated to the certified ceiling of 43,000 feet. If all four generator fail in flight, the Ram Air Turbine will deploy (RAT) will deploy and power only essential buses and, if necessary, hydraulic power to the flight controls (should the RAT itself fail, standby power will ensure continued use of the autopilot, captain’s flight director and instruments, FMC, 2 IRSs and VHF radios in addition to some other essential instruments).
Ram Air Turbine: Ram air turbine - Wikipedia, the free encyclopedia
So even the basic theory of the constant speed propeller is still applied to a modern aircraft.
Quote from Basil
"The plus point, when you make it onto the Dreamliner, is that you don't have to worry about all that stuff
"Actually you still have a constant speed propeller in the form of a RAT on the 787.
You won't have to worry about manifold pressure or propeller pitch control unless they further develop a variable pitch fan.
Variable pitch turbofan : Patent US3946554 - Variable pitch turbofan engine and a method for operating same - Google Patents
A good read here for operation of the 787 RAT:
Boeing 787: A Pilots Perspective
The Rat Part!!
If 3 of the 4 engine drive generators fail in flight, the APU will start automatically. Two APU generators can be operated to the certified ceiling of 43,000 feet. If all four generator fail in flight, the Ram Air Turbine will deploy (RAT) will deploy and power only essential buses and, if necessary, hydraulic power to the flight controls (should the RAT itself fail, standby power will ensure continued use of the autopilot, captain’s flight director and instruments, FMC, 2 IRSs and VHF radios in addition to some other essential instruments).
Ram Air Turbine: Ram air turbine - Wikipedia, the free encyclopedia
So even the basic theory of the constant speed propeller is still applied to a modern aircraft.