Full RPM

[RonnieDuck 10]

I see some strange behaviour of the 4 blue lights. It looks like the lamps are responding to the RPM handle and not to the props rpm.

As soon as the handle is in full all 4 lights turn on, but you still hear that the props are getting in full rpm mode.

I always thought they should respond to the props RPM and not to the handle?

 

Regards Ronald van Ingen

[downscc 1,327]

The blue lights indicate when the governors are in either end point of control (e.g., highest or lowest RPM control).  I assume you mean the master prop control (cue ball) when you say RPM handle.  The blue lights function as they should, however, there are elements of prop control that are not realistic and PMDG made a decision not to pursue this any further.  It is not something anybody in either the XPL or P3D world has mentioned yet..., and you have to be doing the full propeller checks and understand the propellers to catch the problem.  But as far as basic operation of the cue ball and blue lights it is correct.

[RonnieDuck 10]

Yes I mean the Master Prop Control. But the blue lights should indicate the governors position and not the handle position. If I move the Master Prop Control very rapid to full forward it takes some time for the governors to get into full RPM. But the blue light is already lite up. But as I understand, this is not further inplanted in this DC-6. Thanks for the answer.

Regards Ronald van Ingen

[downscc 1,327]

44 minutes ago, RonnieDuck said:

If I move the Master Prop Control very rapid to full forward it takes some time for the governors to get into full RPM. But the blue light is already lite up.

Valid point; however, I believe that the blue light comes on when the governor reaches the lowest fine pitch set point regardless of propeller RPM.  Otherwise, the blue lights are direction indication of RPM and not governor control.  Are not the lights controlled by switches on the speeder spring rack and pinion actuator?  POH 171 "An indicator light is mounted adjacent to each selector switch and illuminates when the corresponding propeller governor has reached its high- or low-rpm limit." This doesn't say the lights turn on or off a specific RPMs... but are tied to the governor itself.

In your example, when you push the cue ball forward (and there is sufficient power) the governor step motor will turn the rack and pinon driving the speed spring against the flyweights. The blue light comes on at the end point of the rack and pinion whereas the RPM increases over a longer time period until it reaches the point where the flyweights and speed spring are in equilibrium.  You are claiming that the blue lights shouldn't come on until full fine pitch equilibrium is reached, and I'm not sure how you would implement that without tachometer switching.

[randomTOTEN 13]

It sounds like he might be saying that there is a time delay for the motor to drive the pinion gear of the governor valve to it's limit... not the wait for the actual propeller pitch.

Robert Toten

[downscc 1,327]

10 hours ago, randomTOTEN said:

It sounds like he might be saying that there is a time delay for the motor to drive the pinion gear of the governor valve to it's limit... not the wait for the actual propeller pitch.

Robert Toten

Perhaps, I'm not sure how fast the stepper motor rotates the pinion.  My Uncle was a brown shoe prop mechanic on C-118s in Germany, he had some pretty good stories a few of which were related to the aircraft.  Decades later, he was still haunted by the memory of the men and aircraft lost due to a run away prop, highlighting how serious he took his job.  I'd love to ask him about this specific topic but we lost him earlier this year.  Needless to say, I have a special interest in anything having to do with these props and willing to learn more.

EDIT:  Brown shoe refers to the early days of the USAF when they still wore USAAF brown shoes before the AF got to black shoes.

[TheFinn88 13]

There is also a different behaviour of the blue lights between the master prop control and the individual governor switches. When I pull the master RPM-lever full back, the blue lights extinguish instantly when the lever leaves the full forward position, and they light up again as soon as I reach the full backward position. When I do this with the individual prop-pitch switches (prop sync in manual), the blue lights take some seconds until they extinguish, and they never light up again (I assume that they dont reach the lower limit in manual control?). And when I increase the pitch in manual mode, it takes again some seconds until the blue lights come on.

For me it looks like that when in synched-mode, the blue governors lights are "watching" the position of my hardware master-RPM lever (which is set to an axis on one of my saitek throttle-quadrants). And when in manual mode, the blue lights are "watching" the actual pitch of the propellers in the sim.

[paulopp 56]

On 26.11.2017 at 7:55 PM, downscc said:

The blue lights function as they should, however, there are elements of prop control that are not realistic and PMDG made a decision not to pursue this any further.  It is not something anybody in either the XPL or P3D world has mentioned yet..., and you have to be doing the full propeller checks and understand the propellers to catch the problem.

Can you elaborate with evidence?

[downscc 1,327]

9 hours ago, TheFinn88 said:

There is also a different behaviour of the blue lights between the master prop control and the individual governor switches. When I pull the master RPM-lever full back, the blue lights extinguish instantly when the lever leaves the full forward position, and they light up again as soon as I reach the full backward position. When I do this with the individual prop-pitch switches (prop sync in manual), the blue lights take some seconds until they extinguish, and they never light up again (I assume that they dont reach the lower limit in manual control?). And when I increase the pitch in manual mode, it takes again some seconds until the blue lights come on.

For me it looks like that when in synched-mode, the blue governors lights are "watching" the position of my hardware master-RPM lever (which is set to an axis on one of my saitek throttle-quadrants). And when in manual mode, the blue lights are "watching" the actual pitch of the propellers in the sim.

Ding ding ding ding.... we finally have the first one to notice that the propeller control is not accurate since the original RTM in XPL.  If you step carefully through the propeller controller checks in the POH you'll find that PMDG simplified the logic for whatever reason, one reason told to me was "it was this way in XPL and no one complained."  The control in automatic is reasonable, but run through the manual checks and the flaws are revealed. A quick one easy to check is that you should have some control over the propeller RPM even in automatic, within a specified speed band, but this is lacking from the simulation.

[randomTOTEN 13]

Like it's A2A cousin, those of us that have really delved deep into these aircraft have found a lot of Microsoft parts are still bolted to these engines. I suspect that the propeller hubs may be such a case. **coughcoughandsuperchargerscoughcough**

On 11/27/2017 at 11:56 AM, downscc said:

Needless to say, I have a special interest in anything having to do with these props and willing to learn more.

You'll really get a kick out of this story relating to Wright R-3350 engine failures then.
http://www.enginehistory.org/Piston/Wright/Kuhns/TC18BDF/TC18BDF.shtml

Robert Toten

PS: It's kind of funny that PMDG chose to model the DC-6B on the assumption that it's 'mechanical' systems would present an easier learning curve for XPlane then a modern EFIS turbine aircraft. And yet, there is a never ending abyss of detail regarding the simulation of these graceful machines. The more they model.. the more their users learn.. and the more detail they can discover. It's a never ending process really.

Also, I'm a bad sim pilot in that I never check the individual governor switches on these 4 engine piston aircraft. I have a strong hunch that the FE would actuate all four switches at the same time, and my inability to do so makes me skip the entire check during the run-up.

[serviceceiling 135]

On 26.11.2017 at 7:55 PM, downscc said:

 It is not something anybody in either the XPL or P3D world has mentioned yet...

Pretty sure A2A have done it. Their propeller simulations on all their aircraft are all physically accurate and correct to the point. Happens when you take things out of the sim and make them external...

[randomTOTEN 13]

9 minutes ago, serviceceiling said:

Their propeller simulations on all their aircraft are all physically accurate and correct to the point.

Load the L-049 and ensure all four engines are shut down. Establish electrical power, then actuate the master governor switch (or I suspect any of the FE prop switches). Observe the Hydromatic propellers change blade pitch with no oil pressure being provided by an oil pump, or accumulator.... and in defiance of the physics of their propeller governors. The developers have stated that the detail of engine physics changes among their aircraft, depending on the focus of the product.

That's Microsoft control logic you're looking at

It also has faulty supercharger behavior (while their warbirds model it correctly) and the developers have admitted it's default Microsoft behavior (those darn MS engine parts again!)

Robert Toten