throttle:Manifold vs Engine rpm

[eilif]

not all early WWII planes had constant speed props, it would spice things up if they were taken off some of the early planes we got.  And i dont think they are working correctly on all our planes, the p40 for example, you couldnt just fire wall it on take off, the prop would stall out, same with the p51 and many other planes. I think the constant speed propelors we got in ah are actualy an ai as well that automaticaly adjusts the prop pitch manualy to keep things working right, or its just not coded acurately.

[Golfer]

It's actually more perfect than a real airplane ever would be because it's not bound by any mechanical laws.  It's instant...can't ask for more than that.  We also don't get fun failures for the sake of ease of use.

If this game was too "real" we might as well get the FAA in here to certify the users...sometimes I think that's what some people want.

For instance...you don't have to deal with a governor that's a POS.  A hub which could use replacement or a nitrogen recharge.  Worn out springs don't exist.  The annoying overspeed/underspeed noises that is constant when one of said airplanes is the one you're flying.  In P-38's and other multiengine airplanes you don't need to sync props in order to maintain your sanity.

It's not all bad.

[Vad]

Originally posted by Hades55
I was speaking about the *numbers keypad + and -* not the keyboards ones who needs shift.

To make it simpler the + and - at numbers keypad is like the gas pedal of
your car.  You control the rotation of your engine. More RPMs more gas needed but also more HP (horse power).

Now, Throttle controls the pitch, means the angle of the wings of the propeller who they cat the air, as the prop turns.
More angle more air goes back more power pull your plane frond.

You can have Full RPMs at your engine but when your pitch is 0 no air goes
back so your plane dont move.

I would say that everything is exactly opposite.

Throttle is your gas pedal. It controls the amount of fuel-air mix going to the engine.
"+" and "-" is pitch control, controls RPM.

[USHilDvl]

Throttle controls manifold pressure, which is an engine function.  Throttle does not control prop pitch.

RPM change (numpad +/-) alters prop speed.

Not the other way around.  You are crossing your terms up all over the place.

You can have Full RPMs at your engine but when your pitch is 0 no air goes

Essentially right, but still not quite...You are right that when the engine is at full throttle (full manifold pressure), but zero prop RPM (which equals zero prop pitch), you would have minimum airflow induced by the prop.  But, we have no engine RPM guage...only prop RPM, so the statement is still confusing.  We have no engine RPM control, either...we adjust for manifold pressure, and engine RPM is a function of that pressure.

The throttle controls the engine.  The RPM adjustment controls the prop pitch.  It's just not the other way around.

[Golfer]

Originally posted by Hades55
Now, Throttle controls the pitch, means the angle of the wings of the propeller who they cat the air, as the prop turns.
More angle more air goes back more power pull your plane frond.

You can have Full RPMs at your engine but when your pitch is 0 no air goes
back so your plane dont move.

The throttle still doesn't control the pitch.  I get what you're saying but the throttle lever is connected via virtual cable to the virtual throttle in the virtual engine.  At no point does moving the throttle directly change the propeller.  The throttle only only only only only is there for engine power which you'll find indicated in manifold pressure.  The propeller system is completely independent of the throttle.

Also...it's more of an airflow thing rather than a power thing.  If you're in a climb and level out, the prop is going to want to go to an overspeed condition which automatically goes away by the governor (depending on airplane type...we'll say single engine) pumping more oil into the hub to let the prop take a bigger bite of air.  If you go from level flight into a descent without touching the throttle...same deal an overspeed condition because now you're moving faster and there is more air passing by...the prop needs to take bigger bites of air in order to reduce the RPM.  This happens automatically and more oil is pumped into the hub by the governor.

When you level off from your descent now our propeller is in an underspeed condition.  Oil is allowed out of the hub which will increase the rpm (decrease pitch) which takes a smaller bite of air.




While it is true that when you move the throttle, one of the byproducts is a change in blade pitch it is only because the propeller system wants to maintain a constant RPM setting...not because your throttle said to.

[Golfer]

Originally posted by USHilDvl
but zero prop RPM (which equals zero prop pitch), you would have minimum airflow induced by the prop.  But, we have no engine RPM guage...only prop RPM, so the statement is still confusing.  We have no engine RPM control, either...we adjust for manifold pressure, and engine RPM is a function of that pressure.

The throttle controls the engine.  The RPM adjustment controls the prop pitch.  It's just not the other way around.

With zero prop RPM you've got zero airflow.

With the blades at Zero pitch they can spin all they want and they're not going to make the airplane move.

Engine rpm is not a function of manifold pressure.  The Prop RPM and Engine RPM (for our purposes) are one and the same.  The prop is bolted to a plate which is part of a crankshaft which is the keystone piece of the engine.  You don't get zero prop rpm without zero engine rpm.  You can get zero pitch (what Hades said) and still have the engine turning.

It also doesn't matter where you get your tach indication from.  In some airplanes that measurment comes from the engine others the prop.  In the FW-149D for instance, I had a hard time wrapping my head around how the heck a big 3 bladed prop could spin as fast as it did.  On departure we'd pull back the prop and still be over 3200rpm.  Not until I learned a little more about the GO-480 (Gear Driven, Horizontally Opposed 480 cu.in.) that the tach indication comes from the motor and not the prop which is probably spinning something more sane on the order of 2300rpm.

[USHilDvl]

You're right about my zero RPM = zero pitch statement...my mistake.  I meant to say what you did...that zero pitch equals minimum prop thrust.  Definitely do not get zero prop RPM without zero engine RPM.

I would probably debate to some degree that manifold pressure is not related to engine RPM.  One might argue that, in a given engine, one cannot increase engine RPM without sufficient manifold pressure...therefore they are related.  Taken to the extreme, no manifold pressure assuredly equals no engine RPM.  I'd have to learn more to convince me that they are not relational functions of one another.

In truth, the real message I was trying to convey is that the throttle does not control prop pitch, and that in AH the RPM guage (according to the help files) is specifically a prop RPM indicator, not engine.  Your point re: the FW is a good example of RL, but I am operating under the assumption that in the game, the guage is reading the prop.  Doesn't matter, tho...I  think we agree on the key point..the virtual throttle is not virtually linked to the virtual prop...only to the virtual engine.  I think your last explanation probably made the point more clearly than I did.