What is the purpose of Propellor RPM control in this game?

[kcmo 2]

I assigned propellor rpm to an extra axis on my HOTAS controller expecting to be able to control throttle and prop pitch.

 

I'm thinking there was some attempt to model prop pitch since I can hear the RPMs drop as I pull back on the axis.

 

However, I see no increase in speed.

 

I'm confused....

[toedv 1]

Why would you expect an increase in speed?

[OMGBBQ32 12]

Prop RPM does not really do anything, not saying it does not at all. It does not increase the speed. An increase of fuel flow or thrust as we call it will also increase prop RPM, thus causing the plane/aircraft to travel faster.

 

Doing anything to the prop RPM selector won't do anything unless you want to fly at slower speed. Prop RPM at lowest setting will reduce speed. Prop RPM at highest setting will increase speed, but only if the thrust is adjusted.

[RamonB 449]

First of all, I'm no expert

 

Propeller pitch is used to adjust the blades to accommodate changes in thrust and air speed, thus increasing overall aircraft engine performance and efficiency.

 

The pitch angle of the propeller should be within a range that gets the most HP of an aircraft engine; when an aircraft is equipped with controllable pitch propellers the pilot adjusts the blades to hit the “sweet spot” of the engine.

 

In other words, changing propeller pitch is not used to adjust speed, but to increase engine efficiency.

 

 

Here are very good explanations:

Http://www.pilotfriend.com/training/flight_training/fxd_wing/props.htm

http://centennialoff...rops/Tech14.htm

[RoboRay 126]

The prop control allows more efficient engine operation by decoupling the engine RPM from the amount of torque or power it is producing.

 

If you don't want to fool with it, you can just leave the prop control pushed all the way in and pretend you're flying with a fixed-pitch prop.

[kcmo 2]

Kabronicus, Yeah, I see now the point I missed. Probably MS is simulating a constant speed propellor such that maximum pitch efficiency is automatically adjusted.

 

I, on the other hand, jumped into the game thinking that a flat pitch was locked into the prop unless you elected to change it.

[RoboRay 126]

Kabronicus, Yeah, I see now the point I missed. Probably MS is simulating a constant speed propellor such that maximum pitch efficiency is automatically adjusted.

 

I, on the other hand, jumped into the game thinking that a flat pitch was locked into the prop unless you elected to change it.

 

The prop control does not select a physical blade pitch; it simply chooses your desired RPM. The actual blade pitch is adjusted by an automatic mechanism as the throttle is opened and closed to maintain your desired RPM.

 

See if this helps: http://www.pilotoutl...speed_propeller

 

The term "constant speed prop" is a bit of a misnomer, because you do have the ability to change the speed. The "constant" part comes from the speed remaining constant unless you choose to adjust it with the prop control.

[kcmo 2]

RoboRay, Doesn't the throttle control manifold pressure and the prop control adjusts pitch?

[RoboRay 126]

RoboRay, Doesn't the throttle control manifold pressure and the prop control adjusts pitch?

 

Not directly, no. Technically, there is a mechanical (usually) governor that automatically controls the prop pitch. You influence the governor with the prop control, by telling it what RPM to "seek."

 

NOTE: I am not a CFI and it's been more than 20 years since my PPL written test. Hopefully somebody will correct anything I get wrong.

[jcomm 5,890]

There is also a feedback to MP and RPM from adjusting each other, something FLIGHT doesn't yet model correctly.

 

When you're flying at a given regime (MP and RPM setting, forgeting now abou mixture...) and you reduce RPM, MP will increase. Increasing RPM will cause MP to lower. This is why you should allways reduce MP first an then RPM, and increase RPM first, then MP.

 

Flying straight & level you can actually increase speed by reducing MP (a bit) then RPM, and then readjusting MP. For more or less the same MP setting you had initialy you'll be able to travel faster because of the "bigger bite" of your prop blades. This is evem more noticeable on a non-constant-speed prop.

[kcmo 2]

jcomm, YES - "bigger bite" - that's what I had in mind when I posted.

 

Looks like not modelled in Flight. Perhaps improved fuel consumption is ......

 

I could not detect if drag in a glide is reduced by pulling back on the prop lever.

 

All in fun - not being critical of the game.

[toedv 1]

Kabronicus, Yeah, I see now the point I missed. Probably MS is simulating a constant speed propellor such that maximum pitch efficiency is automatically adjusted.

 

I, on the other hand, jumped into the game thinking that a flat pitch was locked into the prop unless you elected to change it.

Correct. I still fail to see your issue. You change pitch to take advantage of air density and to optimize fuel efficiency. Look at your fuel flow gauge as you adjust pitch and mixture. You are aiming at constant speed at your current altitude with the least fuel burn.

[kcmo 2]

toedy, my only hands-on flight experience has been with fixed pitch props (C152).

 

I'm trying to understand how to fully use prop speed control with MS Flight.

 

For example, I'm wondering why the top speed at level flight is so slow in the Musting. It hits me that maybe the default prop control level position in MS Flight is firewalled (fine pitch) and that, although, this is proper for take off and landing, it won't be the best setting to squeeze the maximize level flight top speed.

 

So the point I missed is that we're not dealing with fully manual prop control. We're modeling consatnt speed props here.

 

My thoughts are that this is entertainment, which is cool, and that, although neither Manifold Pressure or speed budges when I play with RPMs. The fuel flow does react.

 

So I'm ready to install the ferry tanks, set the RPMs, and head north to Alaska...

[LHookins 3,102]

Why is it that I read the articles at these links and I come out feeling like I know less than when I started? It was the same with the VOR information. I already know how to use a VOR, and I understand constant speed props, but the way they're explained seems like they're attempting to produce the most confusion possible.

 

Is there anyone here who understands this topic thoroughly enough to explain it well, and can explain it in a way that doesn't make it harder than it is?

 

Edit: jcomm did a great job. Any chance of a full article, jcomm?

 

Hook

[Oracle427 45]

kcmo,

 

There is no free lunch! :)

 

When you adjust the prop contol to a lower RPM and leave the engine at whatever power setting it is at, the end result is that the prop pitch will increase to get the engine turning at a lower RPM. This does not necessarily translate into more airspeed because the engine is not necessarily producing more power at the lower RPM. Less power = less speed.

 

As mentioned earlier, every engine has an RPM range (however large or small it is) where it will produce maximum power. Being above or below that range will result in less power delivered to the air by the engine via the propeller.

 

In most cases, when reducing RPM it is to avoid prop resonance, increase fuel efficiency and save on engine and propeller wear.