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Posted (edited)

I am not sure if this is the current engine limitation, or has it been put on hold for fixing until EDGE comes along, but the propeller thickness is way too thin. To the point it just looks ridiculous.

 

It seems as if the propeller is always set to fine (low) pitch which would normally be used on TO. Only when you're cruising the propeller thickness increases, and then again it more resembles an real fine (low) pitch than coarse (high) for cruising.

 

Here is how it looks with engine off and idling:

 

DCS_P-51D_OFF.jpg

 

DCS_P-51D_IDLE.jpg

Few examples on how it looks on real P-51s:

 

 

 

 

 

Then there is TO (actual fine or low pitch):

 

DCS_P-51D_TO.jpg

 

vs. the real thing (image taken from SimHQ):

 

P-51D_propeller_thickness.jpg

Edited by T}{OR

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted
When idling, the prop is on the fine pitch stop. When you bring the power up, the prop starts regulating the rpm by going to a coarser pitch.

 

In my understanding the fine pitch stop prevents the pitch from going past the certain angle of attack in order to prevent negative thrust. Thus when disabled the prop can go to full fine (low) pitch.

 

Developer notes about the governor do not mention anything about fine pitch stop:

 

http://forums.eagle.ru/showpost.php?p=1441842&postcount=92

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted
When idling, the prop is on the fine pitch stop. When you bring the power up, the prop starts regulating the rpm by going to a coarser pitch.

 

Actually, if not for the stop, it would be the other way around.

 

Back to the DCS though, I think it's just a question of sloppy model and animation of rotating prop. With such a wide blade cuffs design used on this particular model of Hamilton Standard unit, it should look much thicker near the hub indeed, even when running in full fine pitch position. The same animation used as a placeholder for paddle-bladed Dora just confirms this observation.

 

I won't be surprised however, if better animation shows up in the future, when more WWII prop planes join the DCS universe.

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Posted

The fine pitch stop decides the minimum pitch the prop can go to - or, to put it another way, it is the lowest pitch available. It's not something you can disable on the Mustang.

 

Actually, if not for the stop, it would be the other way around.

 

Can't get that to make any sense.

 

If there wasn't a mechanical stop there, the governor would keep driving the prop into the reverse range until the prop hub disassembled itself or the engine stalled - whichever comes first.

 

It would still start governing RPM properly as power was applied, provided the above didn't happen.

 

If not for the landing gear, the aircraft would actually flop onto its belly...

Posted

 

"Bringing It All Together

 

The airplane you fly is probably sitting on the ground somewhere as you read this, at rest, with the prop control lever fully forward. What would you expect to see? If it's a single, the prop should be in full flat pitch (spring-driven). We might say, "It's on the low-pitch mechanical stops."

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted
The fine pitch stop decides the minimum pitch the prop can go to - or, to put it another way, it is the lowest pitch available. It's not something you can disable on the Mustang.

 

Can't get that to make any sense.

 

If there wasn't a mechanical stop there, the governor would keep driving the prop into the reverse range until the prop hub disassembled itself or the engine stalled - whichever comes first.

 

It would still start governing RPM properly as power was applied, provided the above didn't happen.

 

If not for the landing gear, the aircraft would actually flop onto its belly...

 

Either someone's confusing fine/pitch terminology or mixing standing plane vs. flying plane scenario (we started with the standing one I believe and I'm still writing about it).

 

The prop governor always uses aero load and counterweight mechanism to adjust blade angle to the optimal value for given forward and rotational speed situation. So when standing on the runway (zero forward speed) and applying power (increasing rotational speed) the pitch will be adjusted to fine setting, not the coarse one as You suggested in Your first post - that's what I was trying to point at, maybe not clearly enough. It can only go coarse when we're already flying and/or reducing power (forward speed goes up, rotational speed goes down). Actually, It's neatly explained in the very Pelican's Perch article You linked to.

 

Back to the standing plane, If there was no fine stop, the blade would go full fine for lowest load on the prop and since it's already a balanced situation, no it would not "keep driving the prop into the reverse range" (unless someone starts pulling the plane backards :D ). That won't happen anyway, because of the fine stops You mentioned - mind You, I'm not arguing about these and neither does T}{OR I reckon.

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Posted
Back to the standing plane, If there was no fine stop, the blade would go full fine for lowest load on the prop and since it's already a balanced situation ...

 

Exactly what is happening with DCS P-51D based on the current animation. It is in full fine, even on TO. After TO it is, at best, on fine pitch setting.

 

Like kripzoo said, Dora has the same problem.

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted

I think that Propellor Sickness is not worth a huge discussion for now.

 

1. current simulationengine is from 2008 (IIRC)

2. EDGE2/DCS2.0 is not that far away

 

Oh and BTW more speed = more propellor pitch.

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Posted

Back to the standing plane, If there was no fine stop, the blade would go full fine for lowest load on the prop and since it's already a balanced situation, no it would not "keep driving the prop into the reverse range" (unless someone starts pulling the plane backards :D ). That won't happen anyway, because of the fine stops You mentioned - mind You, I'm not arguing about these and neither does T}{OR I reckon.

 

I guess he's talking about engine settings where the engine torque is not sufficient to drive the prop at 3000RPM even at minimum pitch. The governor, without a boundary condition such as a minimum pitch, would proceed to drive the blade angle into the direction it "thinks" would decrease the required torque.

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Posted

Art,

you need to look elsewhere to find the confusion. I don't think you need to search far, to be honest.

 

Standing, moving, jumping up and down while doing the moves to Nellie the Elephant - the prop governor doesn't care but keeps doing its thing the same way regardless. Airspeed changes the pitch/torque/RPM relationship, but the governor only looks at the RPM and increases or decreases pitch accordingly, not even knowing the current pitch.

 

When idling, there is not enough power to bring the RPM up to the governed range, even with the prop at the fine pitch stop. The governor senses the low RPM condition and attempts to move the propeller towards lower pitch. To reiterate, it has no knowledge of the current pitch setting - all it knows is that low RPM => pump oil towards lower pitch. If there was no fine pitch stop, it would keep driving the propeller to even finer pitch, through flat pitch and into the reverse range - as I described earlier.

 

The prop only comes off the fine pitch stop as you add power. More power (torque) increases the RPM. When it exceeds the set RPM, the governor will start acting the other way, bringing the propeller towards more coarse pitch until it can suck up the increased torque at the set RPM.

 

If you believe the prop will be at the fine pitch stop for take-off, you need to do some serious reading.

 

Ask yourself: Is the governor regulating the propeller RPM when you are at take-off power?

 

How does it regulate the RPM? If you are at 40", will it maintain the set RPM? If you increase to full take off power, will it still maintain that RPM? How will it do that, if the prop is still on the fine pitch stop?

 

The aero loads and counterweights only come into play if the prop governor fails.

 

Just saving others searching through the article you posted.

 

If you intend for that quote to "save" people from reading which is by broad consensus one of the best articles to read if you want to understand CSPs, you must think it is in some way relevant to the discussion. That's what could do with some explaining. But never mind, I think I'm done here...

Posted (edited)

@ Isegrim: as I said in the first post, I don't expect this to be fixed before EDGE comes out and I for one wouldn't spend any resources on it but hoping that devs either spot or confirm this is in the works for fixing in near future (read EDGE).

 

 

When idling, there is not enough power to bring the RPM up to the governed range, even with the prop at the fine pitch stop. The governor senses the low RPM condition and attempts to move the propeller towards lower pitch. To reiterate, it has no knowledge of the current pitch setting - all it knows is that low RPM => pump oil towards lower pitch. If there was no fine pitch stop, it would keep driving the propeller to even finer pitch, through flat pitch and into the reverse range - as I described earlier.

 

As described in the YT video I posted.

 

If you intend for that quote to "save" people from reading which is by broad consensus one of the best articles to read if you want to understand CSPs, you must think it is in some way relevant to the discussion. That's what could do with some explaining. But never mind, I think I'm done here...

 

I've only extracted that part to point at the fine pitch stop (EDIT: in reference to the screenshots from the first post). Not sure what is the cause of this attitude but I do not intend to dissipate any energy on it. Those who are interested will read, and those who aren't will not.

 

 

 

In the mean time, here are some more shots of the coarse pitch, first two from most likely a high speed pass and the last one showing fine pitch during taxiing:

 

Going through my pics for the F104 I came across these from the NATO Tiger Meet 2009 at KB airbase Belgium.

 

_DSC1054.jpg

_DSC1055.jpg

_DSC1087.jpg

Edited by T}{OR

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted
When idling, the prop is on the fine pitch stop. When you bring the power up, the prop starts regulating the rpm by going to a coarser pitch.

 

True

 

Note that DCS TO pitch actually looks a bit thicker than when idling. Based on my knowledge the opposite should be happening.

 

False

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Posted
If you believe the prop will be at the fine pitch stop for take-off, you need to do some serious reading.

 

Ask yourself: Is the governor regulating the propeller RPM when you are at take-off power?

 

How does it regulate the RPM? If you are at 40", will it maintain the set RPM? If you increase to full take off power, will it still maintain that RPM? How will it do that, if the prop is still on the fine pitch stop?

 

The aero loads and counterweights only come into play if the prop governor fails.

 

 

IF I read / understood the article correctly, the missing detail from this remark is the position of the prop RPM lever:

 

Runup

 

Most Continental direct-drive engines are run up at 1,700 RPM, and most Lycomings specify runup at 2,000 RPM. There is no magic about 1,700 or 2,000 — it's more tradition than anything else — but such mid-range RPM settings do provide a little room to exercise the prop, and also provide a modicum of power to check out the ignition system. The tests and checks will be just as good at 1,500, 1,800 or 2,100, so there is no real need to be precise in setting exactly 1,700 or 2,000 for the runup.

 

At runup RPM, the prop lever is still fully forward, the prop governor is still calling for redline (2,400 to 2,700 in most cases), and the prop blades will still be on their low-pitch mechanical stops. Now, we pull the prop lever back. It doesn't really matter how quickly or how slowly you do that, but for our purposes here, let's say you do it very slowly, perhaps an inch at a time, stopping along the way to see the results. The first inch will reduce the speeder spring pressure, and perhaps it will call for 2300 RPM. Since runup RPM is lower than this, the flyweights are still fully "in" and the system is still trying to increase the RPM by driving the prop blades "flat." The blades are still on the low-pitch mechanical stops, and the governor still sees an "underspeed" condition.

 

Pull the lever back some more, to the point that might call for exactly runup RPM (1,700 or 2,000). Now, at last, "something happens." Moving the prop lever that far will reduce the speeder spring pressure enough that the centrifugal force on the flyweights is "enough" to move them "out" to the "balance point," where the centrifugal force on the flyweights is exactly balanced by the speeder spring pressure. Still, nothing happens at the prop, because the governor is calling for 1,700 (or 2,000), and we've got 1,700 (or 2,000). The blades will still be on the mechanical low-pitch stops, but barely so.

 

Finally, pull the lever all the way back. This further loosens the pressure on the speeder spring and runup RPM is now more than enough to make the flyweights open out. We call this an "overspeed condition," as the prop is (momentarily) turning faster than the governor wants it to. The flyweights open up, porting high-pressure oil into the the prop dome (or for twins, letting oil flow out of the dome), and at last, the prop blades come off the low-pitch mechanical stops and move towards the "coarse" position. Since we have changed nothing but the prop control, this will reduce the RPM, proving the system works as advertised. Many POHs will specify what the lowest RPM should be on runup, and this is important, as it shows "full range." If your POH doesn't list this figure, check it out for yourself, and note it for future runups. The prop does not necessarily go all the way to the high pitch stops, it only goes far enough to satisfy the governor.

 

 

...

 

 

Takeoff

 

Returning to our takeoff, you should now be starting to understand what is happening here. At full power, brakes locked, the prop is fully flat, and the governor is calling for "more," or 2,740 (speeder spring is fully compressed, flyweights "in".) As the speed increases after brake release, the "load" on the prop decreases ("windmill effect"), and the RPM kicks up to 2,740. At this point, the flyweights move out to the neutral position, and everything is "in balance." As the speed continues to build, the RPM will rise slightly above 2,740, but the flyweights will "open up" a tiny bit, and allow oil to flow to the prop hub to twist the blades off the low-pitch stops, cutting the RPM back to 2,740. Repeating this process, it should keep the RPM right at 2,740 until otherwise set.

 

Immediately after liftoff, gear coming up, altitude and airspeed increasing, I'll reach over and pull the prop back a bit, perhaps two turns on the vernier control. This loosens up the pressure on the speeder spring, which allows the flyweights to move "out" (overspeed condition), porting oil to "coarsen" the blade pitch, reducing the RPM. As the actual RPM matches the "requested" RPM, the flyweights move back to neutral, returning to the "on-speed" condition.

 

How much of this applies to the P-51 prop I can not comment. What is also missing from earlier TO pitch descriptions is the part of which one was referring to - brakes on and full power, or lift off.

 

False

 

My original remark is pretty much pointless since finding TO and idle pitch visual difference in DCS is more or less like splitting straws - if there is one.

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WWII bomber formations | DCS P-51D: [TEST] TO distance / gross weight / temperature

Posted

I keep re-reading this discussion hoping I can chime in with some helpful insight (8 years experience as a C-130 engine troop), but I can't seem to tell what the argument is. :D

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Posted (edited)

After watching drawings and diagrams of how usual Hamilton Standard prop works, I think I understand what Effte was after and I admit I was wrong. What got me confused is the fact that centrifugal twisting moment always tries to rotate the blades to full fine and not any further, so concept of prop trying to go into reverse all by itself didn't seem to make much sense. I didn't take into account fact that CSP unit in underspeeding HS is so stupid it apparently tries to pump oil into the prop dome until the end of the world :D. Fortunately low pitch stops prevent it from doing so. Same thing with the concept of prop going coarse on power up. Sounds silly, because It won't at first, but then eventually it will, after reaching set RPM.

 

The fact that half-oil, half-spring-driven McCauleys and Hartzells have piston operation reversed compared to HS doesn't help in understanding it all either.

Edited by Art-J
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Posted (edited)
I am not sure if this is the current engine limitation, or has it been put on hold for fixing until EDGE comes along, but the propeller thickness is way too thin. To the point it just looks ridiculous.

 

It seems as if the propeller is always set to fine (low) pitch which would normally be used on TO. Only when you're cruising the propeller thickness increases, and then again it more resembles an real fine (low) pitch than coarse (high) for cruising.

 

Here is how it looks with engine off and idling:

 

DCS_P-51D_OFF.jpg

 

DCS_P-51D_IDLE.jpg

Few examples on how it looks on real P-51s:

 

 

 

 

 

Then there is TO (actual fine or low pitch):

 

DCS_P-51D_TO.jpg

 

vs. the real thing (image taken from SimHQ):

 

P-51D_propeller_thickness.jpg

 

Note that DCS TO pitch actually looks a bit thicker than when idling. Based on my knowledge the opposite should be happening.

 

As far as I got you right :). DCS replaces the rotating blades with just a flat rotating plane(s) having a motion blurred texture ... up to a certain speed the propellers are set to invisible and the plane, I mentioned, to visible.

Same for the helicopter's Tail and mainrotor. Actually the motionblur for objects is given but it's too performance consuming.

Edited by The_Fragger

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Posted
After watching drawings and diagrams of how usual Hamilton Standard prop works, I think I understand what Effte was after and I admit I was wrong.

 

One of the differences between an amateur and a professional is that the latter knows he or she will at times be wrong, and is prepared to admit it once thoroughly (and, usually, repeatedly) convinced of the fact.

 

I promise I will do the same in the unlikely event that it ever happens. ;)

 

Rep inbound! Edit: Er, no. It says I can't. You'll have to get by on the warm, fuzzy feeling of the intention!

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