Prop ptitch - RPM lever

[gdotts]

Looked through the key commands and can't find the command for operating the propeller pitch - RPM lever. I have the throttle mapped to my thrustmaster but need the Prop-pitch ....please advise. Thank you.

[VincentLaw]

PageUp: Engine RPM Increase

PageDown: Engine RPM Decrease

 

Also called "Engine RPM Setting" under Axis Commands if you wanted to map it to a throttle or something.

Edited April 5, 2013 by VincentLaw

[gdotts]

Trying to get in the fight!

 

It looks backwards to me due to the size of the cockpit levers involved, as I was told you set the manifold pressure first with the larger throttle lever....but actually fly the plane for speed by managing the RPM, with the "smaller" propeller pitch lever.

Just with movies seen and with other planes watched they power-up using a throttle type lever....I had all ways in the past associated the speed and power with a throttle type lever. I guess with the P-51 it is not that way. I have had problems keeping up with anything with the P-51. Now I am trying to regulate a 45@2700 .....It feels like a hot air balloon could out run me. I go for height and dive in on targets but haven't got the timing right then its a loosing chase event. Please advise. Thanks

[VincentLaw]

I have not read the flight manual, but in the training missions, the instructor has you fix the RPM at 2700 during flight and use the throttle to increase and decrease power. It makes more sense to me to keep the RPM fixed because changes in manifold pressure are much more responsive than changes in RPM. You don't have to worry about angular momentum when adding and reducing pressure.

[Cake]

I have not read the flight manual, but in the training missions, the instructor has you fix the RPM at 2700 during flight and use the throttle to increase and decrease power. It makes more sense to me to keep the RPM fixed because changes in manifold pressure are much more responsive than changes in RPM. You don't have to worry about angular momentum when adding and reducing pressure.

 

The P51 has an "Altitude Engine".

 

I'd suggest grabbing FAA-H-8083-25A, specifically search for "altitude engine" and read about " constant speed propellers". Cool, stuff. Oh, you can download the PDF for free from http://Www.faa.gov

[KLR Rico]

The two levers work together.

 

It's not exactly this simple, but think of the throttle lever as the "torque" control, and the RPM as just that. The two of them work together to produce a certain amount of horsepower, as HP = Torque*RPM/5252.

 

Different flight regimes use different settings for efficiency, maximum power, etc., so it's valuable to control the settings independently.

 

BTW, the 45@2700 is just the continuous setting. Feel free to use takeoff power (61@3000) as needed to do what you need to do. Just keep an eye on the temps, maintaining plenty of airspeed (200+) helps there.

Edited April 5, 2013 by KLR Rico

[sobek]

[...]

 

See this thread http://forums.eagle.ru/showthread.php?p=1571752#post1571752

[Der_Fred]

Have a look in some of the RL aviation forums. Here's one such explanation.

A constant speed propeller/governor is not a controllable pitch prop in the sense that the pilot sets the prop control to determine the RPM, not the prop pitch. The governor will adjust the propeller to whatever pitch it needs to maintain the RPM, as long as the prop pitch is not at the high or low stop. Normally the propeller control is set to full forward or full in for maximum RPM. Full throttle and maximum RPM are used for takeoff and climb. In the old days, you would be taught to reduce the manifold pressure and RPM after takeoff and add back manifold pressure as you climbed, for example 25 square, which means set the manifold pressure to 25 inches and the RPM to 2500. This was found to be harder on the engine than leaving the throttle at the wide open position. The reason for this is that the throttle linkage provides for additional fuel at the full forward position and provides extra cooling in the climb. When you retard the throttle, the mixture is leaned, the engine runs hotter, and performance is reduced. Most engines are rated for continuous operation at full power which means full throttle and maximum RPM. Typical maximum RPM values are between 2500 and 2700 RPM. I would recommend a full power climb to altitude and then reduce the RPM to the cruise setting. If you level off at an altitude below 7,000 feet, you may want to reduce the manifold pressure to a cruise setting. Above the 7000 foot point, most engines will be run at wide open throttle. There should be a performance chart that goes with the installation and included in your POH. When you are operating the engine on the rich side of peak EGT, the amount of air you deliver to the cylinder will determine the power setting. The amount of air delivered to the engine is based on several factors, the manifold pressure, the altitude, and the temperature, so you will see these factors in the POH performance table. If you are at full throttle and leveled off, the only control you have to set power is the RPM. A higher RPM will result in more power. One can always reduce power by either reducing the manifold pressure or the RPM or both. If you set a power setting and can adjust both manifold pressure and RPM, the lower RPM with the highest manifold pressure allowed will normally be the most efficient. Most engines have RPM limits for a given manifold pressure, for example on my engine, I can use any RPM down to 2200 with a manifold pressure of 24 inches. Below 2200 RPM, I have to reduce the manifold pressure according to a chart. I never operate at the lower RPM’s because the engine runs smoother above 2300 RPM, in fact my engine has a sweet spot between 2400 and 2500 RPM. So where to run your engine. Follow the POH and use it to determine and set your power. There are more choices than needed, but it is up to the pilot. In my case, I climb full power and after leaving the pattern will just make a reduction of my RPM from 2700 RPM to 2500 RPM for the cruise climb setting. I lean as I climb. When I level off, I let the airplane accelerate and then lean to cruise setting. For me, I don’t touch the prop control for the rest of the flight, with a possible exception to advance it on short final, although that isn’t really necessary as I would have more than enough power for a go around if I needed it at 2500 RPM. If you want to get the airplane anywhere near the service ceiling, you will have to increase the RPM or you won’t have the power to get there. So for me above 12,000 feet I will increase the RPM to 2600 and above 14,000 I will go to 2700 RPM and keep it there for the cruise at high altitude.

[Der_Fred]

Gaud.. that look awfull (editor problems) let me try again

 

A constant speed propeller/governor is not a controllable pitch prop in the sense that the pilot sets the prop control to determine the RPM, not the prop pitch.

 

The governor will adjust the propeller to whatever pitch it needs to maintain the RPM, as long as the prop pitch is not at the high or low stop. Normally the propeller control is set to full forward or full in for maximum RPM.

 

Full throttle and maximum RPM are used for takeoff and climb.

 

In the old days, you would be taught to reduce the manifold pressure and RPM after takeoff and add back manifold pressure as you climbed, for example 25 square, which means set the manifold pressure to 25 inches and the RPM to 2500. This was found to be harder on the engine than leaving the throttle at the wide open position.

 

The reason for this is that the throttle linkage provides for additional fuel at the full forward position and provides extra cooling in the climb. When you retard the throttle, the mixture is leaned, the engine runs hotter, and performance is reduced.

 

Most engines are rated for continuous operation at full power which means full throttle and maximum RPM. Typical maximum RPM values are between 2500 and 2700 RPM.

 

I would recommend a full power climb to altitude and then reduce the RPM to the cruise setting. If you level off at an altitude below 7,000 feet, you may want to reduce the manifold pressure to a cruise setting. Above the 7000 foot point, most engines will be run at wide open throttle.

 

There should be a performance chart that goes with the installation and included in your POH. When you are operating the engine on the rich side of peak EGT, the amount of air you deliver to the cylinder will determine the power setting.

 

The amount of air delivered to the engine is based on several factors, the manifold pressure, the altitude, and the temperature, so you will see these factors in the POH performance table.

 

If you are at full throttle and leveled off, the only control you have to set power is the RPM. A higher RPM will result in more power. One can always reduce power by either reducing the manifold pressure or the RPM or both.

 

If you set a power setting and can adjust both manifold pressure and RPM, the lower RPM with the highest manifold pressure allowed will normally be the most efficient.

 

Most engines have RPM limits for a given manifold pressure, for example on my engine, I can use any RPM down to 2200 with a manifold pressure of 24 inches. Below 2200 RPM, I have to reduce the manifold pressure according to a chart. I never operate at the lower RPM’s because the engine runs smoother above 2300 RPM, in fact my engine has a sweet spot between 2400 and 2500 RPM.

 

So where to run your engine. Follow the POH and use it to determine and set your power. There are more choices than needed, but it is up to the pilot. In my case, I climb full power and after leaving the pattern will just make a reduction of my RPM from 2700 RPM to 2500 RPM for the cruise climb setting. I lean as I climb.

 

When I level off, I let the airplane accelerate and then lean to cruise setting. For me, I don’t touch the prop control for the rest of the flight, with a possible exception to advance it on short final, although that isn’t really necessary as I would have more than enough power for a go around if I needed it at 2500 RPM.

 

If you want to get the airplane anywhere near the service ceiling, you will have to increase the RPM or you won’t have the power to get there. So for me above 12,000 feet I will increase the RPM to 2600 and above 14,000 I will go to 2700 RPM and keep it there for the cruise at high altitude.

[Merlin-27]

...In my case, I climb full power and after leaving the pattern will just make a reduction of my RPM from 2700 RPM to 2500 RPM for the cruise climb setting. I lean as I climb.

 

Doesn't that create a surge of manifold pressure if you reduce RPM before MP? And if you have the pressure maxed isn't that a recipe for engine troubles? Just trying to get a good grip on the best procedures since there seem to be many opinions. I personally have tried my best to adopt the RPM then MP on the increase and MP before RPM on the power decrease. Seems to be serving me well.. hardly ever brick an engine now except for the occasional pursuit where I forget to un-glue my eyes from the gunsight.

[Der_Fred]

That is a quote from a real aviation forum. What plane the guy is flying I'm not sure, as he doesn't mention it - definitely not a P51 :) Anyway he does mention that if you have the engine performance chart (does on exist for the game P51?), you can work this all out. Maybe someone can link it if they find it.

[Yo-Yo]

Nobody sees something looking like engine chart in the cockpit? :)

 

Anyway, advanced throttle, high MP and low rpm bring the engine to its final very soon. So let the throttle be a leader when you reduce power and let it lag in opposite case. For example, you climb at 3000/61" (Watch the coolant and oil temperatures! And increase IAS or decrease MP if they are not OK!) and then reduce power to cruise. Reduce MP first then rpm. It could be necessary to adjust MP after rpm is changed.

Edited April 11, 2013 by Yo-Yo