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rsrandazzo

[04JUN16] PMDG: Killing "Simmerisms" since 1997

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RSR- thank you! Its an absolute now... Im hooked on X-Plane and there is no going back!

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Running FL205 and cowl flaps closed. Engine temp ~200degree C. Is this too much? I thought off closing cowl flaps to gain speed if you are high enough where it's cold.

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Captains,

 

One of our stated aims at PMDG is to provide technically accurate and realistic simulation products for simmers to use, enjoy and learn.

 

With each product release, we generally have to spend a bit of time helping to kill off something we call "Simmerisms."

 

What is a Simmerism?  It is an incorrect understanding of how something is supposed to work.  For example, when we released our 737NG in 2003, we were immediately taken under heavy criticism because users found it very difficult to slow the airplane while descending.  All of their previous simming experience told them that in order to slow down while descending, you simply pulled the throttle to idle...  Which of course- is NOT how it works in the real world...

 

We spent quite a bit of time teaching users the correct technique and how to use the data tables to verify the accuracy of the model- and sure enough 13 years later most simmers understand how it works...

 

The DC-6 is going to be the same.  There are some incredible misconceptions about how these old radial engines behave that come from inaccurate and/or exaggerated sim experiences in the past- lack of knowledge- and lack of experience.

 

So with that- I'm going to throw a few simmerisms into this thread in hopes of helping you to help us to keep people from sounding dumb in public.   :Shame On You: 

 

Simmerism:  "I closed the cowl flaps and the engines didn't overheat."  

 

Good!  They shouldn't. 

 

On some engines the result of closing your cowl flaps MIGHT be an eventual overheat- but generally speaking, that is not going to be the case with a DC-6 unless you have certain, specific, underlying engine health issues at play as well.

 

In the radial engine world- heat is the enemy.  Heat damages your engine by softening the various metals used and allowing the normal operating pressures and forces to damage things such as cylinders and rods at a faster rate than damage accrues at lower temperatures. 

 

If you take two radial engines and rig them in such a way that one engine always runs 50C warmer than the other- I would bet the house on experiencing higher maintenance costs, greater rates of cylinder replacement and an earlier outright failure of the engine that is run at a warmer temperature.

 

Which brings us back to those cowl flaps...  Use your cowl flaps in accordance with the guidelines described in the manual in order to keep your engine temperatures in the optimal range.  If you close them, and sit there running the engines, you will notice that the cylinder head temps climb, and since heat is the enemy- you are in effect doing long term damage to your engine...  

 

But the thing isn't going to explode gloriously aflame like an Independence Day firework display.  

 

The reason we work so hard to keep the engines cool on the ground (By opening the cowl flaps) is so that we can get more work out of an engine if it is needed in the air.  For example, in the DC-3 that we operate, our CHTs with the cowl flaps open normally run around 100C with the cowl flaps open.  When we initially level off at cruise power, our CHTs tend to be around 160C... and then they cool back to 140C and stay there until landing.

 

If I close the cowl flaps and run those engines on the ground, the CHTs will increase 30C on the left side and 45C on the right.  The right engine is older and creates more friction internally...  Thus it creates more heat.  (Yes- we tested this as part of the airplane's initial rigging when we replaced the engines!)  If I then take off, I would expect we will see temperatures around 220C on both engines when we level off at cruise power- and then they will cool back to 145C or so.

 

Now imagine we have an engine failure and have to climb out on one engine...  If we take off with a cool engine- we are going to be able to run it at METO power quite a bit longer than an engine that was 30C warmer at takeoff...  Which is another thing to consider carefully... 

 

So- why allow that amount of heat to accumulate?  Heat is Damage...   Heat is the Enemy.  Heat is Bad...

 

We open the cowl flaps and keep the engines as cool as possible...  You should do the same.  If you leave them closed- you aren't going to see a fireball.  At least... not right THEN...  It will happen some night when fully loaded, taking off into IMC and rising terrain... cuz that is how Murphy's Law works.

 

Okay...  Simmerism "closing the cowl flaps should kill my engine..."   Yeah...  not true... 

 

 

:hi:

Thanks for the in depth explanation Robert! I was skeptical when this "issue" was brought up in a stream. I gueds a little bit of knowledge is dangerous. Will you covering other "simmerisms" in the future?

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Running FL205 and cowl flaps closed. Engine temp ~200degree C. Is this too much? I thought off closing cowl flaps to gain speed if you are high enough where it's cold.

 

Stefan,

 

From page 68 in the POH: 

For normal cruise and descent............................. “CLOSE”; maximum cylinder head temperature 232°C (450°F ); desired, 200°C (400°F)

 

So you are right in the sweet spot!

Thanks for the in depth explanation Robert! I was skeptical when this "issue" was brought up in a stream. I gueds a little bit of knowledge is dangerous. Will you covering other "simmerisms" in the future?

 

Felipe-

 

Fortunately, (or unfortunately, depending on how you want to look at it!), Yes.  I have a few more to address still. 

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I did see that stream, at least the part where he went on and on about the engines and the cowl flaps, if it was the same stream the guy is allegedly an airplane engineer (which is per se a very broad statement, or title) however his explanations seemed to be based on futile expectations fiting the purpose of a basic and general understanding of how a radial works, and indirectly assuming (at least from my point of view) that all the engines are the same. Shame that some people take opinions for facts, especially if It meets the momentum some communities seem to gain related to outsiders, bordering on tribalism...

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.... Yes.  I have a few more to address still. 

 

Thank you for the article, Cpt. Randazzo!

 

Incidentally, some "simmarisms" appear to be platform specific, i.e. the inherited notion among some X-Plane users that all prop planes have inherent lateral instability and those that are stable and can be hand-flown without dropping a wing and constantly juggling the aileron and rudder trim are "unrealistic": a notion that historically follows from the not entirely accurate roll dynamics and torque in earlier versions of X-Plane: a deficiency, that has been since overcome both by the internal development of X-Plane and the efforts of 3rd party addon developers that worked around it in their models. Hope you address that as well. Thanks for an awesome plane!

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Shame that some people take opinions for facts, especially if It meets the momentum some communities seem to gain related to outsiders, bordering on tribalism...

 

It kind of works the same in the opposite direction which you don't seem to see. Shame.

 

Katrín Eiriksdóttir

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It kind of works the same in the opposite direction which you don't seem to see. Shame.

 

Katrín Eiriksdóttir

Enjoying flight simulation in every platform, hoping that all developers publish products for every platform in the market so that our hobby keeps growing. That's what I want. If I'm not mistaken it was one of your posts in which you or someone with the same username was quite vocal about the dc-6 flaws that led me to that particular stream. I personally didn't find many flaws in the airplane despite some minor stuff that requires work, and I've only stated my opinion about that stream, which seemed unnecessarily aggressive towards minor or non existent flaws. In the end all I want is that PMDG keeps developing airplanes for xplane, and FSX, and P3D, as naturally we'll all benefit from it one way or another.
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I did see that stream, at least the part where he went on and on about the engines and the cowl flaps, if it was the same stream the guy is allegedly an airplane engineer (which is per se a very broad statement, or title) however his explanations seemed to be based on futile expectations fiting the purpose of a basic and general understanding of how a radial works, and indirectly assuming (at least from my point of view) that all the engines are the same. Shame that some people take opinions for facts, especially if It meets the momentum some communities seem to gain related to outsiders, bordering on tribalism...

 

Carlos-

 

Thanks for the note.  Tribalism is definitely a factor in PMDG's day-to-day operation.  When we announced in August 2002 that we were planning a release for MSFS2002, we were abused so openly that it was really quite shocking.  When that product released in 2003, the abuse only became worse.  Needless to say, we learned to deal with it- let our product quality speak for itself- and I think many simmers have forgotten that at one time we were outsiders to the MSFS marketplace.

 

Seems we are seeing a bit of that again- but it is human nature.  Some folks just don't like outsiders- and we really are outsiders to the X-Plane market and it brings out a natural tribalism.

 

It is just part of the marketplace.  I think you see it no matter where you go.

 

Our job is to separate facts from opinion.  If someone THINKS we did something wrong, we encourage them to come and ask.  If we are indeed wrong, then we fix it.  If we are correct- then everyone gets to learn something about the airplane in the process.

Thank you for the article, Cpt. Randazzo!

 

Incidentally, some "simmarisms" appear to be platform specific, i.e. the inherited notion among some X-Plane users that all prop planes have inherent lateral instability and those that are stable and can be hand-flown without dropping a wing and constantly juggling the aileron and rudder trim are "unrealistic": a notion that historically follows from the not entirely accurate roll dynamics and torque in earlier versions of X-Plane: a deficiency, that has been since overcome both by the internal development of X-Plane and the efforts of 3rd party addon developers that worked around it in their models. Hope you address that as well. Thanks for an awesome plane!

 

Svilen,

 

That is an astute observation- and one we can certainly agree with.  I pointed out in a different thread that X-Plane has some embedded flight model behaviors that are native to certain types of airplanes, but do not exist for airplanes of this size and design.  Engineering those behaviors out of the flight model of the DC-6 was a monumentally challenging task- and one that I think will keep Chris mumbling to himself in the dark for a few more months at least.  :P

 

Is it perfect?  No.  We know that- because it is a mathematical approximation- so the further you get from the center of the statistical norm, the more variance you can have in the outcome.  That is true even of the sims used to train flight crew- and it is the reason why so many pilots complain that "the sim flies nothing like the airplane."

 

The goal is to get very close- and I think we did that here.  We have some very experienced DC-6 flight crew supporting us on this project and they have been exceptionally helpful in nailing down the normal behaviors of the airplane in flight.

 

When we get Chris' medicine dosage down to acceptable levels again- perhaps I can talk him into writing a piece about the techniques we developed to convince X-Plane to stop acting like a large-bore horizontally opposed single engine prop and more like a large bore, huge-chord, fire breathing dragon that is the DC-6....

 

Perhaps...  but the meds are still pretty heavy.  :wink:

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[...]Is it perfect? No. We know that- because it is a mathematical approximation- so the further you get from the center of the statistical norm, the more variance you can have in the outcome. That is true even of the sims used to train flight crew- and it is the reason why so many pilots complain that "the sim flies nothing like the airplane."[...]

Ah this made laugh. I'm a train driver and believe it or not we do spend a good amount of time inside of full size simulators which mimic the real train cabs, we regularly have to go for checks were we might spend time practicing procedures, doing train handling, emergencies, dealing with faults and failures etc etc... And you would think that a train, being something that goes on rails would be easy to simulate considering the millions it costs for a single one of those simulator units. However I've yet to meet a train driver which will claim that the simulator handles like the real train, I can assure you it doesn't. If it is so hard to simulate a train and its behaviour, I can only imagine how hard it must be to simulate an airplane which will run on my personal computer and make it feel similar to the real thing.

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Ah this made laugh. I'm a train driver and believe it or not we do spend a good amount of time inside of full size simulators which mimic the real train cabs, we regularly have to go for checks were we might spend time practicing procedures, doing train handling, emergencies, dealing with faults and failures etc etc... And you would think that a train, being something that goes on rails would be easy to simulate considering the millions it costs for a single one of those simulator units. However I've yet to meet a train driver which will claim that the simulator handles like the real train, I can assure you it doesn't. If it is so hard to simulate a train and its behaviour, I can only imagine how hard it must be to simulate an airplane which will run on my personal computer and make it feel similar to the real thing.

 

 

 

Wow thanks for the insight Carlos, very interesting stuff. The most obvious thing to do if you feel the model is lacking is come to the forums and explain your issues. That way as Robert has pointed out everyone can learn. The worst is complaining about something and then not trying to help in the process to improve it, especially for this particular case.

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Carlos-

 

Yes!  To fly the 747-400 sim, you would think the airplane is unpleasant to fly by hand, which really isn't the case.

 

I recently completed qualification in a CE550 and the sim was so bad that I had to close my eyes and look down whenever starting or stopping motion, or it would make my inner ear rotate so badly that it would induce vertigo.

 

The FAA examiner griped at me during the checkride- so I had to pretend to sneeze or sniffle or wipe my nose right at that moment instead- just to keep him from making an issue of it. 

 

The 744 sim is quite a bit better, but it is very over sensitive in pitch and under-sensitive in roll...  I try to dismiss it as the manufacturers way of making the real airplane easier and more enjoyable to fly...

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Wow thanks for the insight Carlos, very interesting stuff. The most obvious thing to do if you feel the model is lacking is come to the forums and explain your issues. That way as Robert has pointed out everyone can learn. The worst is complaining about something and then not trying to help in the process to improve it, especially for this particular case.

I have nothing to complain about the Dc 6 model, I've never flown a real one, and it seems amazing to me. I was just saying that the life size train simulators in which I do regular checks behave nothing like the real life counterpart, and if it is so hard to simulate a train, I can only imagine how hard it must be to simulate an airplane, which in my opinion PMDG did fantastically well! I'm sorry if my post came the wrong way, I was in no way complaining about the airplane or even talking about it, just sharing my real life experience with expensive full size simulators!

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I have nothing to complain about the Dc 6 model, I've never flown a real one, and it seems amazing to me. I was just saying that the life size train simulators in which I do regular checks behave nothing like the real life counterpart, and if it is so hard to simulate a train, I can only imagine how hard it must be to simulate an airplane, which in my opinion PMDG did fantastically well! I'm sorry if my post came the wrong way, I was in no way complaining about the airplane or even talking about it, just sharing my real life experience with expensive full size simulators!

 

Carlos sorry I wasn't talking about you! My mistake!

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