calculating flight times

[Dawger]

Roadblock,

You are confusing things here.

In the Piper Arrow you have RPM and Manifold Pressure.

Aces High has the same setup.

RPM is propeller RPM (and engine RPM on a direct drive engine)

Manifold pressure is Power

Prop lever controls RPM.

Throttle controls Manifold Pressure (or boost for the British)

It works exactly the same in AH as it does in real life (except for the possibility of overboosting and blowing jugs off the engine)

[Roadblck]

Roadblock,

You are confusing things here.

In the Piper Arrow you have RPM and Manifold Pressure.

Aces High has the same setup.

RPM is propeller RPM (and engine RPM on a direct drive engine)

Manifold pressure is Power

Prop lever controls RPM.

Throttle controls Manifold Pressure (or boost for the British)

It works exactly the same in AH as it does in real life (except for the possibility of overboosting and blowing jugs off the engine)

No, I know the difference.  Perhaps I wasn't clear in my original post.  Try this (I can't test it myself at work to be absolutely certain, but I'm 90% sure these are the steps):

Take off in a 190D, climb up to 15k-20K feet. 
Throttle (MP) and RPM (propeller) both to full. 
Let the plane accelerate to 390+ TAS. 
Now, open the E6B and slowly dial back the propeller control to minimum.  Note that the RPM doesn't change, nor does your airspeed, but the fuel burn drops significantly.

I'm asking "is this supposed to happen"?  This is certainly a big no no from what I've been taught (high MP settings with low RPM), so I've never tried in an actual airplane and thus I don't know what actually happens.

[Dawger]

I have located the source of confusion.

There is no RPM gauge on the E6B in game. Those are just a list of power settings for the aircraft. They do not change. Consider it the POH section. E6B is a confusing name for the clipboard performance info.

As for the airspeed changing when you decrease RPM at full power. ...

The airspeed should increase and it does unless you are above the speed that can be sustained by max power and maximum coarse pitch on the propeller. The increase in speed is minor and this holds true in real airplanes as well.

Of course, you only get to pull back the prop with full throttle at higher altitudes where the engine can't overboost itself (non-super or turbo charged).

Climb that Arrow up to 10,000 feet and you will be full throttle and pulling the prop back for cruise. You might get 2 knots extra after about 20 minutes.

[Roadblck]

I have located the source of confusion.

There is no RPM gauge on the E6B in game. Those are just a list of power settings for the aircraft. They do not change. Consider it the POH section. E6B is a confusing name for the clipboard performance info.

As for the airspeed changing when you decrease RPM at full power. ...

The airspeed should increase and it does unless you are above the speed that can be sustained by max power and maximum coarse pitch on the propeller. The increase in speed is minor and this holds true in real airplanes as well.

Of course, you only get to pull back the prop with full throttle at higher altitudes where the engine can't overboost itself (non-super or turbo charged).

Climb that Arrow up to 10,000 feet and you will be full throttle and pulling the prop back for cruise. You might get 2 knots extra after about 20 minutes.

I only referenced bringing up the E6B so you could observe the fuel consumption decrease.

I still don't think I've correctly explained my question.. bear with me!


My understanding of constant speed propeller behavior is as follows (from the FAA Airplane Flying Handbook):

Pulling back on the
propeller control causes the propeller blades to move
to a higher angle. Increasing the propeller blade angle
(of attack) results in an increase in the resistance of the
air. This puts a load on the engine so it slows down. In
other words, the resistance of the air at the higher blade
angle is greater than the torque, or power, delivered to
the propeller by the engine, so it slows down to a point
where the two forces are in balance.

When an airplane is nosed up into a climb from level
flight, the engine will tend to slow down. Since the
governor is sensitive to small changes in engine r.p.m.,
it will decrease the blade angle just enough to keep the
engine speed from falling off. If the airplane is nosed
down into a dive, the governor will increase the blade
angle enough to prevent the engine from overspeeding.


and

The range of possible blade angles is termed the
propeller’s governing range. The governing range is
defined by the limits of the propeller blade’s travel
between high and low blade angle pitch stops. As long
as the propeller blade angle is within the governing
range and not against either pitch stop, a constant
engine r.p.m. will be maintained. However, once the
propeller blade reaches its pitch-stop limit, the engine
r.p.m. will increase or decrease with changes in
airspeed and propeller load similar to a fixed-pitch
propeller. For example, once a specific r.p.m. is
selected, if the airspeed decreases enough, the
propeller blades will reduce pitch, in an attempt to
maintain the selected r.p.m., until they contact their
low pitch stops. From that point, any further
reduction in airspeed will cause the engine r.p.m.
to decrease. Conversely, if the airspeed increases,
the propeller blade angle will increase until the
high pitch stop is reached. The engine r.p.m. will
then begin to increase.

If we don't see an RPM drop when we pull the prop control back, while cruising at high speed, then (to me) that implies the prop blade angle is already at its maximum limit.  If this is true, why does the fuel burn keep decreasing as we continue to move the propeller control back?

If we had a mixture control, and could lean it ourselves, then I could see the fuel burn changing in this way.  The behavior I'm seeing just doesn't make sense to me!
That make more sense?

[Dawger]

I think you have found a bug Roadblock but I doubt it will get fixed.

I went into the DA and dove a 190D and the propeller does not hold its RPM setting (Which is realistic..the wind will drive the prop at high speed) but the fuel flow does not increase with RPM


It took me quite a while to get wrapped around what you were trying to say because I was doing all the testing in level flight and everything was working like it is supposed to. It was only when diving that the issue becomes obvious. RPM increases above setting but fuel flow does not (and it should increase).

I'll write it up in the bug forum but it shouldn't be a high priority to get fixed as it affects very little. You shouldn't be diving with the prop back very often.

[Roadblck]

I think you have found a bug Roadblock but I doubt it will get fixed.

I went into the DA and dove a 190D and the propeller does not hold its RPM setting (Which is realistic..the wind will drive the prop at high speed) but the fuel flow does not increase with RPM


It took me quite a while to get wrapped around what you were trying to say because I was doing all the testing in level flight and everything was working like it is supposed to. It was only when diving that the issue becomes obvious. RPM increases above setting but fuel flow does not (and it should increase).

I'll write it up in the bug forum but it shouldn't be a high priority to get fixed as it affects very little. You shouldn't be diving with the prop back very often.

Thanks Dawger!   

I'm glad to see at least one other person sees something that seems to raise an eyebrow.  I'm not too worried about it getting fixed, honestly.  This game isn't really about cross country flight planning, and calculating fuel burns.

 

[Dawger]

Sorry it took me so long to figure out what you were trying to say.