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Correct use of throttle and RPM control


Boris
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I'm still a little unsure on the use of the throttle and RPM control.

 

While the propeller RPM should be fully forward on take-off, how do I handle it in flight?

 

If I understand it correctly, the RPM lever controls the blade pitch whereas the throttle controls the amount of fuel flow to the engine, right?

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I mapped the RPM lever and reduce it to 2700 after T/O...and pretty much leave it alone after that. Then I just worry about MP... but others may manage differently.

 

Lets see what they say...

 

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I'm still a little unsure on the use of the throttle and RPM control.

 

While the propeller RPM should be fully forward on take-off, how do I handle it in flight?

 

If I understand it correctly, the RPM lever controls the blade pitch whereas the throttle controls the amount of fuel flow to the engine, right?

 

The throttle actually controls the amount of boost pressure in the manifold, fuel flow is mostly a result of the level of power demand.

The prop lever does indeed affect the blade angle and this in turn will affect the RPM, full RPM is required for take off and landing and a reduced RPM for cruise/combat to increase efficiency (similar principle to gearing in cars)

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This thread gives me an opportunity to address my questions about this subject. A few days ago someone posted about the oil overheating while in steep climbs for very short times. He posted a track and indeed was only in the climb for a few seconds and the engine started smoking. I myself have had this issue while going air to air with the 109. It seems that the very first time I try to climb with him, I start smoking. I understand that people are saying that going under 180 with my RPM, and manifold too high will do this. But it always seems like an immediate catastrophe. Within 2 or 3 seconds, the engine seems like it's toast. The funny part of it is that I can continue the fight and usually down the 109. But in the end, I'm smoking most of the time. This is not a bit too sensitive?

I know that I have watched videos of others who shoot down the 109 and they do the exact climb that I do to catch it in a stall and their engine oil doesn't seem to overheat. So what is the solution to this? I know that when I'm in a 109 and I encounter a Spitfire, all I do is get a little energy and go straight up. At least 50% of the time the Spitfire will start to smoke. And of course this does not work against the AI for obvious reasons.

I have very few problems flying the Spitfire, but this is a huge problem for me. And, maybe because I'm doing something wrong, but it seems a bit extreme to me. I know that the guy who posted the thread on this gave up in frustration on asking about it because he was told nothing was wrong. So if this is the case, what is the correct way to do this without my engine smoking.

 

Now....When I'm flying the Spitfire. Say I'm climbing at around 1500 FPM. My speed can be up around 220 mph, my Prop is @ 2700-2800, and my Manifold is around say 4-8 (really makes no difference). I look at my oil temp and it's between 85-90. I can reduce my climb rate but it does not seem to affect the oil temps. I can reduce my RPM, and my manifold and everything stays pretty much the same. I can even be in level flight, with my RPM @ 2700, Manifold at 6 and speed at 200, and my oil pressure will still be above 80. Sometimes I look at it and it's just below 80 and I haven't changed a thing. From everything I have read, the Oil temps need to stick around 80. Bottom line for me is that whether I'm a complete ignoramus or the plane is not right, I cannot figure the oil pressure out to save my life because it doesn't have a set behavior pattern the way I'm using my settings right now.

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The throttle actually controls the amount of boost pressure in the manifold, fuel flow is mostly a result of the level of power demand.

The prop lever does indeed affect the blade angle and this in turn will affect the RPM, full RPM is required for take off and landing and a reduced RPM for cruise/combat to increase efficiency (similar principle to gearing in cars)

I might be tottally wrong here but the way that I understood how RPM and boost stettings are affecting aircraft performance is:

1. The RPM setting gives an indication to the governor which RPM level to maintain

2. The boost setting controlled by throttle, affects the engine power output which in return with a fixed RPM affects the prop pitch. In example, a higher boost would result in more power needed to sustain given RPM with increased prop pitch.

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I might be tottally wrong here but the way that I understood how RPM and boost stettings are affecting aircraft performance is:

1. The RPM setting gives an indication to the governor which RPM level to maintain

2. The boost setting controlled by throttle, affects the engine power output which in return with a fixed RPM affects the prop pitch. In example, a higher boost would result in more power needed to sustain given RPM with increased prop pitch.

 

Indeed, it's a constant speed propeller.

 

https://en.wikipedia.org/wiki/Constant-speed_propeller

 

Although it isn't directly linked to boost per se. Instead the governor just adjusts pitch to maintain a specific RPM based on a feedback process. However changing boost may well change various flight conditions which could affect RPM, the most significant of which is airspeed.


Edited by Tomsk
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I might be tottally wrong here but the way that I understood how RPM and boost stettings are affecting aircraft performance is:

1. The RPM setting gives an indication to the governor which RPM level to maintain

2. The boost setting controlled by throttle, affects the engine power output which in return with a fixed RPM affects the prop pitch. In example, a higher boost would result in more power needed to sustain given RPM with increased prop pitch.

 

1. yes, the governor maintains the desired RPM by altering the blade angle, the levers control of blade angle is indirect but ultimately that is what is being controlled.

 

2.yes, the power output of the engine will not usually affect the RPM because the governor will try to maintain it, it is possible to reach an overboosted situation so not sure about the very last part of your question, boost is power so a higher boost would not require more power but it would require an increase in RPM to prevent overboost. are you saying that an increase in power will cause the blade angle to increase for a constant RPM? in which case yes that is correct.

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The gearing in cars analogy is correct if your car is equipped with CVT transmission. :)

 

The engine produces maximum power at fully open throttle and maximum RPM (unless the boost limiter kicks in). So if you want maximum performance in combat, you need to set the propeller RPM to 3000. Of course this is also the most demanding setting and it will cause the engine to overheat quickly.

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The gearing in cars analogy is correct if your car is equipped with CVT transmission. :)

 

.

 

Not really, the fact that the propeller RPM is manually changed is very much like selecting gear in a manual transmission, the comparison really only applies to how the power is transferred and not the mechanical function, simple way to put it is that max prop RPM is like being in 1st gear, you get plenty of torque and pulling power but wont go very fast and lowering the RPM is like shifting up the gears.

using 3000 RPM in combat would be a terrible idea, much better to use Max climb settings and don't use maximum boost for too long.

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Not really, the fact that the propeller RPM is manually changed is very much like selecting gear in a manual transmission, the comparison really only applies to how the power is transferred and not the mechanical function, simple way to put it is that max prop RPM is like being in 1st gear, you get plenty of torque and pulling power but wont go very fast and lowering the RPM is like shifting up the gears.

using 3000 RPM in combat would be a terrible idea, much better to use Max climb settings and don't use maximum boost for too long.

 

It depends on your / your opponents energy status and capabilities...:-) but the worst idea is to use 3000 +18 at slow turns fighting. :-)

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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I haven't shot down a lot of Spitfires yet. I have however seen plenty of cooked engines, and even more broken wings ... the Spitfire really isn't best suited to following the high speed manoeuvres you can pull in a 190 :)

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Not really, the fact that the propeller RPM is manually changed is very much like selecting gear in a manual transmission, the comparison really only applies to how the power is transferred and not the mechanical function, simple way to put it is that max prop RPM is like being in 1st gear, you get plenty of torque and pulling power but wont go very fast and lowering the RPM is like shifting up the gears.

using 3000 RPM in combat would be a terrible idea, much better to use Max climb settings and don't use maximum boost for too long.

 

Interesting because to reach max level speed you need 3000rpm. Also if you go low RPM and high power you will kill your engine. You need to adjust rpm before changing power.

 

If you want to be most combat effective u have to change the RPM to 3000 as it gives u the most acceleration and enables WEP.

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Interesting because to reach max level speed you need 3000rpm. Also if you go low RPM and high power you will kill your engine. You need to adjust rpm before changing power.

 

If you want to be most combat effective u have to change the RPM to 3000 as it gives u the most acceleration and enables WEP.

 

Well Yo-Yo has already confirmed the last part of your statement is simply not true, there is nothing combat effective about early engine failure.

 

I don't know the Spitfire personally but have colleagues and friends that do fly them in real life and my own experience with constant speed propellers is completely at odds with your initial statement, max level speed cannot be achieved at max RPM and you would not adjust RPM before power if you were intending to accelerate for pretty much the reason you state in the middle as a low RPM at high power is not good for the engine, always set cruise/climb power first then bring RPM down.

 

The basics of operating a constant speed prop are (I obviously will not include the Spitfire due lack of personal experience):

 

Take off:

set Max RPM, max power (usually a 5 minute limit)

 

Climb:

set Max continuous power, set Climb RPM (slightly reduced from max with no time limit but watch those temps)

 

Cruise:

set Cruise power, set Cruise RPM (further reduction from Climb and power must be limited to prevent strain on the engine)

 

Descent:

set descent power, no need to change RPM

 

Approach:

Max RPM, power as required to maintain vertical profile and or speed.

 

in event of missed approach:

Max RPM should already be set on approach thus allowing safe use of max power.


Edited by bongodriver
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The gearing in cars analogy is correct if your car is equipped with CVT transmission. :)

 

The engine produces maximum power at fully open throttle and maximum RPM (unless the boost limiter kicks in). So if you want maximum performance in combat, you need to set the propeller RPM to 3000. Of course this is also the most demanding setting and it will cause the engine to overheat quickly.

 

CORRECT

 

 

 

Not really, the fact that the propeller RPM is manually changed is very much like selecting gear in a manual transmission, the comparison really only applies to how the power is transferred and not the mechanical function, simple way to put it is that max prop RPM is like being in 1st gear, you get plenty of torque and pulling power but wont go very fast and lowering the RPM is like shifting up the gears.

using 3000 RPM in combat would be a terrible idea, much better to use Max climb settings and don't use maximum boost for too long.

 

the part i marked in bold is NOT CORRECT

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I haven't shot down a lot of Spitfires yet. I have however seen plenty of cooked engines, and even more broken wings ... the Spitfire really isn't best suited to following the high speed manoeuvres you can pull in a 190 :)

 

It depends on bad/good habits...:-)

 

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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not my opinion, physics mate.

 

you can try yourself at full boost see how flat out fast you get with either 2700 or 3000 rpm

 

First of all....mate....my opinion is based on the physics I experience in the real world, yours seems to be based on the sim, now we need to establish if we have found a bug.

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Not really, the fact that the propeller RPM is manually changed is very much like selecting gear in a manual transmission, the comparison really only applies to how the power is transferred and not the mechanical function, simple way to put it is that max prop RPM is like being in 1st gear, you get plenty of torque and pulling power but wont go very fast and lowering the RPM is like shifting up the gears.

using 3000 RPM in combat would be a terrible idea, much better to use Max climb settings and don't use maximum boost for too long.

We're getting slightly off topic but the CVT transmission could be used as a good illustration for constant speed propeller. The only slight difference would be that the pilot has an authority over governor max RPM setting while in case of CVT transmission the electronics also take care automatically about the highest needed RPM value.

In a car with manual gearbox, by controlling the accelerator the driver is directly operating the engine RPM which directly affects the speed. Switching a gear obviously affects RPM but also the engine power output required to maintain RPM or accelerate. In other words the manual geer box could be compared to a plane with fully manual throttle and pitch controls where chaning a gear works like manually setting the prop pitch while throttle directly controls RPM and power output needed to sustain it.

In case of CVT the electronics are maintaining the most optimal, quite often constant RPM. Kind of like the governor with already mentioned difference that in a plane pilot has a direct authority over the expected RPM value. The throttle also indirectly affects a gear = prop pitch setting.

The CVT may seem quite unnatural at the beggining as when accelerating from 0 to max speed the engine will mostly keep a constant RPM while how high the RPM value is will depend on how fast the driver wants to accelerate.

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First of all....mate....my opinion is based on the physics I experience in the real world, yours seems to be based on the sim, now we need to establish if we have found a bug.

 

Check tests of airplanes u are talking about. At lower RPM you cannot go faster than at higher RPM. In both Spit and P51 you need 3000rpm to gain max speed. All best performances for the Merlin engine are at 3000.

 

If DCS is correct. Our engines quit after a bit of abuse while we have IRL reports of way longer abuse and just engine damage not loss. For example I've read that R2800 was tested on WEP 2300hp for 24h (constant operation). Engine was sitting on the ground. Test concluded engine was damaged but it didn't quit.

 

Sure we don't have a radial, but I am pretty sure those engines should start running rough and loose power and not just die 100% of time.

[sIGPIC][/sIGPIC]In 21st century there is only war and ponies.

 

My experience: Jane's attack squadron, IL2 for couple of years, War Thunder and DCS.

My channel:

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