Knights of the Sky Foundation

[BMA_Hellbender]

Unf.

[Cynic_Al]

On 12/16/2019 at 8:07 PM, J99_Sizzlorr said:

 

Interesting....for reference a screen from FCs current Dr.I doing roughly 100 mph... notice the elevator deflection...

 

 

You're forgetting something important: In-game the rendered deflection is more representative of the proportion of the force the pilot would be able to apply, not the true deflection that would result.  For level flight, the simulated DR1 may need a rendered deflection of about 15 degrees down, which if achievable in a real plane would have a far greater effect, possibly terminal.

[Chill31]

1 hour ago, Cynic_Al said:

 

You're forgetting something important: In-game the rendered deflection is more representative of the proportion of the force the pilot would be able to apply, not the true deflection that would result.  For level flight, the simulated DR1 may need a rendered deflection of about 15 degrees down, which if achievable in a real plane would have a far greater effect, possibly terminal.

Huh?

[SeaW0lf]

In a way you guys were in tune ? They are going to release both the Fokker F.I and DrI models.

 

[Chill31]

Here is a little data for you....

 

1250 rpm with ~91 inches of pitch on 98 inch diameter prop gives me 98 mph.  I flew a 3 leg triangle GPS track at 1000 feet to get the speed. 

http://www.woodenpropeller.com/S4C.html

 

*****Edit******

This is not full throttle for the engine.  It is merely a datapoint we can use to build an accurate aerodynamic model in FC.  For example. if 777 can hold the Fokker static in the chocks, the full throttle RPM should be 1210 or so.  Then if it is flying at 1250 rpm, it should go 98 mph.  At that point, we have an accurate aerodynamic model into which we can put any other engine and get accurate performance.  

***************

 

The plane would absolutely go faster if my prop had more pitch because I am not able to get full throttle for fear of over speeding the engine beyond 1300 rpm.

 

Considering the speed it has on only 90 hp (my guess since my 80 Rhone has aluminum pistons which should give it about 10 more hp over the original steel pistons), I suspect it would be as fast if not faster than the almost 130 hp Gnome powered Pup.

 

And for anyone who wants to see what goes into flying a rotary powered Dr.I...here ya go.

 

Edited December 27, 2019 by Chill31

[Zooropa_Fly]

I can't believe how well you've modelled that thing on RoF.

 

I pulled the trigger for you a couple of times there - that Camel was toast !

 

Sensational Chill, well done man.

 

Salute !

[BMA_Hellbender]

Amazing footage, thank you!

 

I have two questions:

 

1. Would it historically have been possible to overspeed the engine beyond 1300 RPM in level flight, or could this be limited by a mechanic? If it was possible, then that is likely what we'll need for all rotaries, the ability to (briefly) go into overspeed.
    
2. Is it possible that the 80hp Le Rhone gives higher top speed but a significantly worse climb than the 110hp Oberursel?

[ZachariasX]

5 hours ago, Chill31 said:

Here is a little data for you....

 

1250 rpm with ~91 inches of pitch on 98 inch diameter prop gives me 98 mph.  I flew a 3 leg triangle GPS track at 1000 feet to get the speed. 

 

Nice. You‘re perfectly matching the Thomas Morse two seater S6 with that engine.

 

That one does 97 mph at 1260 rpm with what they say is a 90.5 inch pitch prop and your engine. See here, page 57. In this circular, you find also more detailed info such as climb speed and time to altitude.

 

In the operation manual for the 80 LeRhone they don‘t specify the propeller itself. This means that there was only one type of prop used. And that was what they deemed in 1920 in the USA to be a 90.5 inch pitch prop. It may well be that exactly that one is now labeled as 90 inch pitch. I wonder what the actual manufacturing tolerances are...

 

My take away from this is that for practical purposes, the drag at these low flight speeds is about identical among these scouts and the main determinant is prop pitch and rpm, as drag penalty between aircraft is (for practical purposes) identical. (Pup, Camel, Dr.I, etc.) In other words, if you have this combination for one plane, you can tell with less than 5% error what the speed of another plane will be, especially among the slow aircraft. This only in the intended rpm bracket. Above and below that, prop efficiency drops and you have to factor that in. You can do that, as this can be transferred between alike aircraft featuring the same engine/prop combination.

 

The slip for those biplanes is even slightly lower (as is expected) than in case of for instance a Cessna 172S (IIRC, I‘m not in my library now). This is not surprising as the biplanes here are slower and are under pitched. But even there, this rule of the thumb works out well.

 

It is important though to only compare aircraft in similar weight and power brackets. Above 200 km/h drag increases drastically, whereas (as a rule of thumb) below 200 km/h drag has negligible impact on design. Above that, added speed become a factor for added power requirements. This also applies for designing cars and even trains. 

 

 

Edited December 27, 2019 by ZachariasX

[1PL-Husar-1Esk]

Thanks for great footage. I have question, do you remember at what RPMs does yours Dr.1 start to move forward on the ground or maybe you can't reduce enough RPMs and need to use wheel chocks to prevent moving forward ?

[ZachariasX]

Going through these numbers and using drag and prop efficiency parameters from the LeRhone80 Dr.I with the Clerget Camel, this would put the „officially stated“ (wiki ?) 115 mph for the Camel spot on. It would do this at the rated 1250 rpm of the Clerget.

 

Thus in FC, we‘re definitely revving the Camel way too high, 1400 rpm would put it around 123 mph, drag and prop efficiency considered.

The Clerget Camel not only uses a slightly steeper pitch prop, it also uses a larger one to the degree that we can fairly certain assume identical efficiency at razed power.

 

I don‘t think it is a great idea to overspeed the engines and fantasize what we would get then. The Le Rhone is rated at 80 hp @ 1200 rpm, making it go 1350 rpm will give a 90 hp engine. In effect, you‘re talking about a different engine then, it is a „Le Rhone 90“ then. Until it blows. The only useful information gained from such is if you hear about someone abusing his engine in such a way, you can with great accuracy predict his performance if you know the set values of the aircraft.

[SeaW0lf]

15 minutes ago, ZachariasX said:

Thus in FC, we‘re definitely revving the Camel way too high, 1400 rpm would put it around 123 mph, drag and prop efficiency considered.

 

The Oberursel 110 manual indicates that, for best results, you should run it at 1360-1380rpm at ground level. The Fokker D8 tested at McCook Field ran at 1390rpm (Oberursel 110) at ground level. The Clerget 9B manual states: 130 hp in normal use (1,200rpm) and can provide 150 hp temporarily in overdrive (1400rpm).

 

So these engines could run at +- 1400rpm (as it appears, depending on the prop?). Every other plane in ROF and FC runs at WEP all the time other than the Pup I think (it overheats in turnfights, you have to bring the throttle back). Then if every other plane runs on WEP, the rotaries should as well.

 

The problem with the Camel, at least here, is that it runs at 1460rpm. Those 60rpm less would bring it back to around 185km/h, which is more realistic as it appears from real data. I never tested the Camel pre-nerfing in ROF, so I'm not sure if it also ran at 1460rpm.

[ZachariasX]

22 minutes ago, SeaW0lf said:

The problem with the Camel, at least here, is that it runs at 1460rpm. Those 60rpm less would bring it back to around 185km/h, which is more realistic as it appears from real data.

 

I just don‘t think those planes were flown regularly at those rpm. I just doesn‘t make sense to rate an engine at given max. power and then recommend everyone adding 15% power for regular use. You don’t have to go up far until you can’t reach more than 1200 rpm. Hence, designing the engine such that it can produce rated power at a somewhat (actually, they flew much higher) reasonable altitude makes sense on the other hand. While I do think that it was possible overspeed the engines down low (the engines rotate slowly, hence timings should still be ok, but centrifugal loads are another animal), I don‘t think it is a plausible common practice, much less to state maximum speeds at non permissible (but sometimes workable) regimes.

 

Besides, 1400 rpm and 115 mph in case of the Camel make no sense. 115 mph isn‘t achieved at any rpm other than 1250. Unless you are very high of course, but then you will not reach 1400 rpm anyway. The Camel would be a terrible aircraft if it only reached 115 mph at 1400 rpm. The laws of physics are the same for both the Dr.I and the Camel.

 

What is clear however, especially in case of under pitched propellers, is that you should easily be able to overspeed your engine in level flight. This is normal behavior of an under pitched setting. It means that you have to limit your airspeed yourself rather than rely in the the increasing of the in drag at higher speeds. And you do it for the simple reason that your mileage tanks if you do not throttle back. In most fixed pitch prop planes, there is little gained with the last 5% rpm, the hit in mileage is just not worth it. But this extra power allows you to reach a good rpm up high where your engine gets starved for air.

 

In case of the Oberursel, where the most known property is the one of being a bad engine that suffers from poor lubrication (and only turns into a good engine once it is replaced by a Clerget along with real lubrication), I just have my doubts about average pilots running their engines constantly far past stated ratings. And if someone did it, oh well. His risk.

 

There were different propellers for the Oberursel, basically pitched between 2,2 meters to 2.4 meters (I guess that this 2.4 meter pitch is the „90“ inch pitch). This means the Dr.I with a Clerget can and will be only be marginally faster than the LeRhone, talking about 1 or 2 mph here at the same 1200 rpm. This because the prop is also larger in diameter.

 

That said, it will make the Dr.I go near 110 mph. If you indeed go up to 1400, you should expect about 120 mph (on the 2.4 meter pitch prop!) for the Dr.I and about 123 mph for the Camel. Then again, I find most frequently 2.2 meter pitch for the Oberursel, making the Dr.I go about 110 mph at 1400 rpm (what I would find a preposterous regime with synthetic lubrication), drag and prop efficiency considered. (There is simply no reason to assume that propeller efficiencies and respective drag differ that much between 100 and 120 mph.)

 

 

 

 

[SeaW0lf]

1 minute ago, ZachariasX said:

I just don‘t think those planes were flown regularly at those rpm.

 

None of the ROF and FC planes were flown regularly balls to the walls, although we do fly all of them at 100% all the time. It is just a matter of consistency, otherwise it would be bias. Since they might never model a proper engine operation in FC, we will continue to fly all the planes at 100% all the time.

 

That's how it is, not how it should be. I would love to see engine management on these planes, but for all of them, not just a select few.

[ZachariasX]

1 minute ago, SeaW0lf said:

That's how it is, not how it should be. I would love to see engine management on these planes, but for all of them, not just a select few.

I‘d love that too, especially the rotaries would get very interesting.

 

But as far as performance goes, a pretty clear picture emerges:

 

This on one side that 110 mph for the Oberursel powered Dr.I and 115 mph for the Clerget Camel are reasonable assumed speeds at maximum rated power. On the other hand, I would expect that down on the deck, you should be able to push those aircraft to 115 or 120 mph (or so) respectively. I should expect corresponding performance from the Nieuports 11 and 17.

 

This probably applies to the inline aircraft as well in some way, meaning that down low, they probably over perform as well, as their engines probably can reach higher power outputs than rated. But for this I had to find good data on them to compare.

 

[BMA_Hellbender]

If the top speed of the Clerget Camel is 117mph, then I expect this to be at at full throttle, in other words: at 1400 RPM (150hp), not at 1250 RPM (130hp).

 

Likewise, the top speed of the Bentley Camel is 125mph, which is likely also attained at max RPM (???hp), not at 1250 RPM (150hp).

 

All according to the manufacturer: https://www.baesystems.com/en/heritage/sopwith-camel

 

 

In other words: all that needs to be coded in for the Camel is an emergency power band above 1250 RPM which causes damage to the engine if held for longer than 10-20 minutes. Something along the lines of the CL.II 200hp being held at full throttle at sea level. In practice nothing much will change, but it will limit the Camel's ability to go fast or to climb for a long time outside of fights.

 

Obviously the Fokker Dr.I needs to have the same emergency band coded in, where it can go up to 1380 RPM for a limited amount of time and reach its pre-nerf RoF figure of 178km/h.

[Todt_Von_Oben]

WEP is an American term from WWII meaning War Emergency Power which implied pushing the engine to additional horsepower for combat.  The P51 Mustang had a wire limiting the throttle lever; break it  and 61% additional power became available for a short time.  Other WEP methods (not just by America) included water injection or water-alcohol injection.  

 

WW1 airplanes had no such provisions and did not operate at WEP.  The concept had not been realized until many years later.  

 

In a small plane, full throttle is generally referred to as METO power: Maximum Engine Take Off power.  

 

And generally, lengthy operations at METO power are discouraged to protect the engine.  

 

In every plane I've ever flown: you take off at METO and then cut back to cruise or cruise climb settings to avoid overheating the engine.  Plus, it just makes good sense from the standpoint of fuel conservation and engine longevity.

 

Do the ROF and FC1 planes overheat if you run at METO continously?  My only experience with that was in 2017 when I tried to keep up with a runaway Flight Leader and toasted my Alby repeatedly.  After that I stopped playing follow the leader and started flying the plane.  No overheating problems since then.

 

CHILL:  I'm like this.  When I see something outrageously cool; I wish I was doing it myself.  But if I can't do it, I'm just as glad to see somebody else who can.  You are living what the rest of us can only dream of and I am living the dream vicariously through the videos.  Was very interesting to see your technique with the throttle and mixture levers.  Thank you!  

 

 

 

 

 

 

Edited December 28, 2019 by Todt_Von_Oben

[ZachariasX]

12 minutes ago, J5_Hellbender-Sch27b said:

If the top speed of the Clerget Camel is 117mph, then I expect this to be at at full throttle, in other words: at 1400 RPM (150hp), not at 1250 RPM (130hp).

 

If that was the case, then these top speeds would be sea level speeds. I doubt that the people back then were as much interested in such as we are now (when not distracted by counting rivets).

 

So far, all actual flight tests don‘t support your expectation. It‘s just not thinkable that in underpitched configuration, an S6 (being very similar in dimensions) scout would do at 1400 rpm what the Dr.I does at 1250.

 

Also, looking at the tests done IIRC with the Roland, Rumpler, D.VII and Dr.I (posted before somewhere in this forum), IIRC they mentioned the corrected top speed of the Dr.I 155,8 km/h at 2300 meters, up to 4300 meters where it supposedly did 138 km/h. There is no mention of any sea level speed. (Not being in my library, I had to look for the document again.) But I’m certain it served our devs as source to calibrate airspeeds.

 

110 mph for the Dr.I, I’d really consider the high water mark and not really representative reflecting the actual engine situation back then. 

 

 

[Garven]

Slightly off topic but what is the best method for converting IAS given in game to TAS that is commonly used in published performance data?  I was using Wolfram Alpha website, but wasn't sure if their method is correct.  

[BMA_Hellbender]

 

29 minutes ago, ZachariasX said:

 

If that was the case, then these top speeds would be sea level speeds. I doubt that the people back then were as much interested in such as we are now (when not distracted by counting rivets).

 

110 mph for the Dr.I, I’d really consider the high water mark and not really representative reflecting the actual engine situation back then. 

IAS or TAS?

 

188km/h (117mph) top speed was likely measured as TAS somewhere below 2000m, which would mean its top IAS/TAS at sea level would be close. 190km/h is not unthinkable. To think that it would go even faster when temporarily throttling up to 1400 seems unlikely. At the very least the manufacturer would use that figure as its top speed.

 

178km/h (110mph) seems like the logical top speed for the Dr.I at 1380 RPM considering the Camel and Dr.I have almost the same top speed at 1200(50?) RPM in RoF.

Edited December 27, 2019 by J5_Hellbender-Sch27b

[Cynic_Al]

2 hours ago, SeaW0lf said:

I would love to see engine management on these planes, but for all of them, not just a select few

 

For the rotaries that would mean having to operate simultaneously two separate variable controls, rendering those planes effectively inaccessible to those without the necessary hardware.

I can think of better selling points.

[ZachariasX]

1 hour ago, J5_Hellbender-Sch27b said:

IAS or TAS?

IIRC TAS.

 

1 hour ago, J5_Hellbender-Sch27b said:

178km/h (110mph) seems like the logical top speed for the Dr.I at 1380 RPM considering the Camel and Dr.I have almost the same top speed at 1200(50?) RPM in RoF.

That would be if the Dr.I got a „speed“ prop with 2,4 meters, yes. That would make sense.

 

1 hour ago, J5_Hellbender-Sch27b said:

190km/h is not unthinkable.

In terms of plain airspeed, it is not. It just would produce rpm that I‘d consider excessive.

 

What bugs me is that the speed trials mentioned put the Dr.I at around 167 km/h max TAS at sea level, and it seems to me that our Dr.I is not just a „nerf port“, but in fact matched to those speed trials.

 

It would also be consistent with a Dr.I featuring a 2.2 meter pitch prop (again, using Chills prop efficiency and drag).

 

We should really watch out what Dr.I exactly we are getting. The fastest will not have the best climb and vice versa.

 

Also that speed trials do not state obtained revs makes it hard to asses what we really have.

 

If we have indeed the 2.2 meter pitch prop (that I think was standard) on our FC Dr.I, then our current Dr.I features correct speeds and they do match the speeds obtained in the trials mentioned above.

 

 

32 minutes ago, Cynic_Al said:

I can think of better selling points.

In „simple engine management“, that could be taken care of as far as access restrictions go.

 

But for people that like those rotaries as they were, I think it could be a selling point.

Edited December 27, 2019 by ZachariasX

[SeaW0lf]

36 minutes ago, Cynic_Al said:

 

For the rotaries that would mean having to operate simultaneously two separate variable controls, rendering those planes effectively inaccessible to those without the necessary hardware.

I can think of better selling points.

 

I think more of rpm management, mixture, radiator, over-rev, that sort of thing. For example, Mikael Carlson has a D.VII article and it has some procedures that are not just taking off and throttle up. It requires some nursing. The rotaries would be nice in coops, the wear and tear of going constantly WEP.

 

Of course we don’t have data or information for every engine, plane, then I think it is not feasible at this point.

Edited December 27, 2019 by SeaW0lf

[Chill31]

12 hours ago, J5_Hellbender-Sch27b said:

Amazing footage, thank you!

 

I have two questions:

 

1. Would it historically have been possible to overspeed the engine beyond 1300 RPM in level flight, or could this be limited by a mechanic? If it was possible, then that is likely what we'll need for all rotaries, the ability to (briefly) go into overspeed.
    
2. Is it possible that the 80hp Le Rhone gives higher top speed but a significantly worse climb than the 110hp Oberursel?

1. It would definitely be possible to overspeed the engine.  There is no mechanism for limiting RPM other than to throttle back.

2. Not at all.  Mikael Carlson told me the 110 on the Dr.I makes it feel like a rocket ship. 

 

9 hours ago, 1PL-Husar-1Esk said:

Thanks for great footage. I have question, do you remember at what RPMs does yours Dr.1 start to move forward on the ground or maybe you can't reduce enough RPMs and need to use wheel chocks to prevent moving forward ?

It starts rolling around 800-900 rpm.  It depends on the terrain of course, but if it is flat, those numbers are good.

 

6 hours ago, ZachariasX said:

Going through these numbers and using drag and prop efficiency parameters from the LeRhone80 Dr.I with the Clerget Camel, this would put the „officially stated“ (wiki ?) 115 mph for the Camel spot on. It would do this at the rated 1250 rpm of the Clerget.

 

Thus in FC, we‘re definitely revving the Camel way too high, 1400 rpm would put it around 123 mph, drag and prop efficiency considered.

The Clerget Camel not only uses a slightly steeper pitch prop, it also uses a larger one to the degree that we can fairly certain assume identical efficiency at razed power.

 

I don‘t think it is a great idea to overspeed the engines and fantasize what we would get then. The Le Rhone is rated at 80 hp @ 1200 rpm, making it go 1350 rpm will give a 90 hp engine. In effect, you‘re talking about a different engine then, it is a „Le Rhone 90“ then. Until it blows. The only useful information gained from such is if you hear about someone abusing his engine in such a way, you can with great accuracy predict his performance if you know the set values of the aircraft.

Yes, 1400 rpm is very high for continuous power.  I would expect this only in a dive during a dogfight.

 

The propeller pitch really determines the performance.  If you have a high static RPM, you have a good propeller for climbing, but not for going fast.  Likewise, if you have a lower static rpm at full throttle, then you have a good "highspeed" propeller. 

 

The Camel static RPM should be around 1100 -1150 rpm.  We already have data for that prop/engine combo from CAMS: "Our normal camel style one, straight and level 1200 rpm and 110 mph." That is fitted to a 125 hp Gnome and mounted on a Sopwith Pup.

 

 

6 hours ago, SeaW0lf said:

 

The Oberursel 110 manual indicates that, for best results, you should run it at 1360-1380rpm at ground level. The Fokker D8 tested at McCook Field ran at 1390rpm (Oberursel 110) at ground level. The Clerget 9B manual states: 130 hp in normal use (1,200rpm) and can provide 150 hp temporarily in overdrive (1400rpm).

 

So these engines could run at +- 1400rpm (as it appears, depending on the prop?). Every other plane in ROF and FC runs at WEP all the time other than the Pup I think (it overheats in turnfights, you have to bring the throttle back). Then if every other plane runs on WEP, the rotaries should as well.

 

The problem with the Camel, at least here, is that it runs at 1460rpm. Those 60rpm less would bring it back to around 185km/h, which is more realistic as it appears from real data. I never tested the Camel pre-nerfing in ROF, so I'm not sure if it also ran at 1460rpm.

Where can I get this manual???

 

 

4 hours ago, J5_Hellbender-Sch27b said:

If the top speed of the Clerget Camel is 117mph, then I expect this to be at at full throttle, in other words: at 1400 RPM (150hp), not at 1250 RPM (130hp).

 

Likewise, the top speed of the Bentley Camel is 125mph, which is likely also attained at max RPM (???hp), not at 1250 RPM (150hp).

 

All according to the manufacturer: https://www.baesystems.com/en/heritage/sopwith-camel

 

 

In other words: all that needs to be coded in for the Camel is an emergency power band above 1250 RPM which causes damage to the engine if held for longer than 10-20 minutes. Something along the lines of the CL.II 200hp being held at full throttle at sea level. In practice nothing much will change, but it will limit the Camel's ability to go fast or to climb for a long time outside of fights.

 

Obviously the Fokker Dr.I needs to have the same emergency band coded in, where it can go up to 1380 RPM for a limited amount of time and reach its pre-nerf RoF figure of 178km/h.

 

The RPM limits on WWI rotary engines is not so much temperature related as it is centrifugal force related.  They will start failing and coming apart before they over heat.

 

I will ask some Camel guys what static RPM they are getting and get back to the group.  Then we can tell how much rpm it should be turning at any given speed provided it is at full throttle.  1400 rpm seems like a whole lot...I am too chicken to run a rotary that fast without some really solid data to back it up.

 

3 hours ago, ZachariasX said:

So far, all actual flight tests don‘t support your expectation. It‘s just not thinkable that in underpitched configuration, an S6 (being very similar in dimensions) scout would do at 1400 rpm what the Dr.I does at 1250.

 

I think you are right in what you are saying there...

 

For consideration, performance would depend on whether or not the 1250 was at wide open throttle.  For example, if the S6 is wide open throttle and only hitting 1250 because it has too much drag, then it would have less performance than the Dr.I with the same engine/rpm.  My Dr.I will probably hit 1350-1400 rpm in level flight if I did not hold it back.

 

5 hours ago, SeaW0lf said:

 

None of the ROF and FC planes were flown regularly balls to the walls, although we do fly all of them at 100% all the time. It is just a matter of consistency, otherwise it would be bias. Since they might never model a proper engine operation in FC, we will continue to fly all the planes at 100% all the time.

 

That's how it is, not how it should be. I would love to see engine management on these planes, but for all of them, not just a select few.

Regarding the actual management of the rotary, I don't feel like it is too far off in ROF/FC.  

 

What is 100% though??  We need the ability to place the airplane in the "chocks" and check static RPM at full power while the plane is not moving.

someone asked me:

Quote

 

Hi Chill, thanks for the latest data! I was wondering about the fist figure you got with the Le Rhone (173km/h at 1300rpm). Did something change? I guess the guns added some drag, but from 173km/h to 157/km/h seems to be a drastic reduction. And those 1300rpm were off or you did change something to max at 1250rpm?

 

On the propeller, I get this post from the Aerodrome regarding the Dr1:

 

One of the propellers used on Fokker Dr.I (e.g. Baubeschreibung, Nov 1917) is AXIAL EDUL ZUG 110 PS OB UR II D 262 ST 230 Diameter 2.62 m, Pitch 2.3 m, Chord 230 mm, 1200 rpm Regards, Yavor

P.S. Good source is R.C.Gardner's data base on German propellers

 

Regarding the runs, could it be due to the runs at 1000 feet? That flyby you did on your maiden flight was, as it appears, in a well secluded runway, sided by trees. I imagine it would give a better controlled environment for some measurements, to make runs from both sides? It is also closer to sea level. Or do you think it is better to make runs in the open?

 

Anyways, thanks for all the info!

 

 

I tried to pick an RPM that was high AND sustainable.  I don't want to keep it at 1300 rpm for very long...

 

On my previous test, I did not do a 3 leg pattern to account for wind, so I don't consider it to be overly reliable.  Also, this is NOT the fastest the Dr.I will go with this engine...it is only as fast as the propeller will go.  If I give it full throttle, it will easily hit 1350 rpm, maybe more, and I cannot afford to damage this engine.  That is why I chose 1250.  I suppose it might be misleading, so I will go make it clear on the post.

 

As it is, my data is not representative of the Dr.Is CAPABILITY, but only of what it does in this configuration.  If 777 replicated what mine does, they would have an accurate aerodynamic model into which they could place a "bigger" engine such as Oberursel URII and get accurate performance.

 

[SeaW0lf]

3 minutes ago, Chill31 said:

Where can I get this manual???

 

I linked the post a while back. I imagine that you, having a Dr1 with a Le Rhône,  would have no trouble to ask him a scan of the manual. If I recall correctly, he translated the post from German.

 

Quote

1400 rpm seems like a whole lot...I am too chicken to run a rotary that fast without some really solid data to back it up.

 

It is just a guess, but I think that in the military, especially back then, they didn't care much about the pilots, not so much about the engines, but I assume they handled it differently from a collector. The quotes are true, at least the Clerget one and the Oberursel on the D8, then I imagine that they ran it at max rpm during tests and replaced the engine in case of failure.

 

Quote

What is 100% though??

 

Here in FC or in ROF, full throttle. On the Camel, it gets to 1460rpm on the deck. You can run that way forever, the same way we go full throttle with the D7 and all other planes. If I recall correctly, just the Sopwith Pup requires some throttle back in turnfights or steep climbs to don't overheat and seize the engine - the same that was happening with the Dva bug (that was recently fixed).

[ZachariasX]

11 hours ago, Chill31 said:

For consideration, performance would depend on whether or not the 1250 was at wide open throttle. 

 

One can cross check that with climb settings. There, you should have throttle fully open. The S6 starts the climb at 1130 rpm, reaching 6500 ft in 10.3 minutes, still doing 1125 rpm. (In 23.7 min it reached 10‘000 ft., still doing 1110 rpm. 42.2 minutes to service ceiling at 12‘900 ft., going at 1080 rpm) Looking at how small the power drop is, I think they were also holding back power down low in some way.

 

Comparison of static/climb rpm should yield direct comparison of power output between your engine and the one used in the S6.

 

But for the time being, my working hypothesis regarding Dr.I flight speed is:

 

Initially, with the 2.2 meter prop, it is a 100 mph plane. With the 2.4 meter pitch prop, it got to be a 110 mph plane. Some unicorns that had their engine (and propeller!!) exchanged for a hunted Clerget were 115 mph planes. Jacobs plane springs to mind.

[BMA_Hellbender]

On 12/27/2019 at 9:41 PM, Chill31 said:

The Camel static RPM should be around 1100 -1150 rpm.  We already have data for that prop/engine combo from CAMS: "Our normal camel style one, straight and level 1200 rpm and 110 mph." That is fitted to a 125 hp Gnome and mounted on a Sopwith Pup.

 

Well, that pretty much confirms that I'm wrong in my assesment of top speed at 1400 RPM instead of 1200, and that the Camel performs even better than it does today, since even if its top speed is slightly lower, it can go up another 200-300 RPM in dogfights (engine failure currently happens at 1500).

 

It also means that the RoF Camel and FC Camel are both equally wrong, that no amount of RPM reduction or "emergency take off power" trickery is going to fix the underlying issue and that pretty much all Clerget/Le Rhone rotaries, Camel, Dr.I, Pup, N17, N11, even the HD.1 need full FM reviews.

 

I'm sure that the devs can't wait to get started on those.

 

 

Or maybe we can just stay in Wonderland, not touch the Camel with a ten foot pole and just have the Fokker Dr.I go up to 1350-1380 RPM, and reach 178km/h that way, the way it used to in RoF pre-1.034. I'm sure this is literally 5 minutes of work.

[Chill31]

13 hours ago, ZachariasX said:

 

One can cross check that with climb settings. There, you should have throttle fully open. The S6 starts the climb at 1130 rpm, reaching 6500 ft in 10.3 minutes, still doing 1125 rpm. (In 23.7 min it reached 10‘000 ft., still doing 1110 rpm. 42.2 minutes to service ceiling at 12‘900 ft., going at 1080 rpm) Looking at how small the power drop is, I think they were also holding back power down low in some way.

 

Comparison of static/climb rpm should yield direct comparison of power output between your engine and the one used in the S6.

Wow! 1130 rpm in the climb? The static RPM must have been around 1100-1130. That means my Dr.I would definitely be faster than the S6 with the same propeller. 

 

I don't think they are holding it back down low, because those are the kinds of numbers I was hoping for on my own engine/prop combo.  A max power climb at 1100-1150 leaves a lot more room for speed to increase.  

 

I am climbing the Dr.I at 1200 rpm and 65 mph. I level off and get 98 mph at 1250 rpm. Imagine if I had another 100 rpm available for acceleration before I hit the rpm limit (albeit an arbitrary limit on my part, though I base it on the power charts I've seen for the 80 Rhone as well as the experience of other pilots). 

16 minutes ago, J5_Hellbender-Sch27b said:

 

Well, that pretty much confirms that I'm wrong in my assesment of top speed at 1400 RPM instead of 1200, and that the Camel performs even better than it does today, since even if its top speed is slightly lower, it can go up another 200-300 RPM in dogfights (engine failure currently happens at 1500)

 

The top speed is likely in the 1200 range. And 1400+ rpm is something one would only achieve in a dive.

 

If I start at 1200 rpm in level flight, I think a dive speed increase produces about 10 mph per 100 rpm if I don't touch the throttle. I will do some detailed experiments to be sure though.  Of course, one could probably dive at 150 mph going straight down with the throttle at idle.

[ZachariasX]

10 hours ago, Chill31 said:

Wow! 1130 rpm in the climb? The static RPM must have been around 1100-1130. That means my Dr.I would definitely be faster than the S6 with the same propeller. 

I would expect both your Dr.I be faster and your engine to be more powerful than what they commonly had at hands 100 years ago. This is especially common with car engines. (Even today you don‘t want to put your car on a rolling road to measure actual power, chances are that you won‘t like your car anymore.)

 

For the example with the S6, it seems quite clear to me that the engine has less power than your LeRhone. Both speed chart and climb rpm indicate to me a throttle in a full forward position. Whatever „full forward“ actually is. It is a trainer aircraft, so limiting power (and rpm) would certainly ease things regarding maintenance.

 

The only way to compare actual power output is to compare static rpm with a similar prop. What is your static rpm? 1250? We might well be comparing your 80 hp to 70 hp on the S6. (I would also have guessed that static rpm of that S6 to be ~1100.)

 

For the purpose of guessing flight speeds, this does not matter, as the aircraft is entirely agnostic to the engine and its respective fitness. All that matters is prop dimensions and actual rpm. And in this respect, in throttled back condition, we have a match, indicating drag and prop efficiency. And they turn out to be „perfectly natural and normal“ as they can be expected from any decent aircraft.

 

In order to compare aircraft, we always need prop dimensions and rpm, as engines have a rather large variation of power output. Having a specified prop and rpm nullifies that, as it standardizes actual torque and hence matches power output. It is moot to compare aircraft when one does 10 hp more than the other that you don‘t know about.

 

In operational use, engine fitness is of course an issue, but one should only look at that when aircraft performance as such is known. Then it allows you to predict the effect of added/lost hp on flight speed. I generally allow myself a 5% margin on predictions. Hence, a „110 mph aircraft“ might well be doing 105 or 115 mph.

 

I see your aircraft with a perfect engine as the high water mark for a Dr.I running that prop at that rpm. Same goes for todays Camels. That they do sometimes 120 mph is perfectly in line. They should be on the fast side. They are lighter than average (no ammo, tanks not 100% full) and have a perfect engine. Conversely, I doubt that the war horses back then full with ammo and fuel would reach that speed, but did settle for the lower end of their speed bracket.

 

 

It is amazing how little interest fixed pitch propellers get in the discussions here when musing about airspeed. It seems everyone is thinking in line of constant speeds propellers that are drastically superior propositions. The selection of your fixed pitch propeller sets your top speed, more than anything. All that matters is how fast you crank it. By which mean you crank it is entirely irrelevant. Prop selection also determines your climb. For the same(!) Cessna 172, flight speeds can vary from around 90 to 120 knots, depending on selected prop pitch; the fast one having roughly half the climb of the slow one. And yes, you’ll know how fast you will go before installing a certain propeller.

 

 

11 hours ago, J5_Hellbender-Sch27b said:

Or maybe we can just stay in Wonderland, not touch the Camel with a ten foot pole and just have the Fokker Dr.I go up to 1350-1380 RPM, and reach 178km/h that way,

They much rather could document what kind of Dr.I we exactly have. They would need to state the propeller for that. So far they don’t. In fact, all they had to do is state in the description that it has the 2.2 meter prop and they wouldn’t have to touch the FM at all. Thus, they actually could sell us three Dr.I or make propeller/engine mods available (Now THAT would be cool!). As of now, we just have the slowest one, the „early bird“. As we have a late war scenario in FC, having the faster (and maybe more rare; as said, I find few references for the 2.4 meter pitch prop) that can do 110 mph would be suitable. But:

11 hours ago, J5_Hellbender-Sch27b said:

It also means that the RoF Camel and FC Camel are both equally wrong, that no amount of RPM reduction or "emergency take off power" trickery is going to fix the underlying issue and that pretty much all Clerget/Le Rhone rotaries, Camel, Dr.I, Pup, N17, N11, even the HD.1 need full FM reviews.

This!

 

I‘m sure everyone at 777 put this as no.1 priority for 2020. ?

[BMA_Hellbender]

2 hours ago, ZachariasX said:

They much rather could document what kind of Dr.I we exactly have. They would need to state the propeller for that. So far they don’t. In fact, all they had to do is state in the description that it has the 2.2 meter prop and they wouldn’t have to touch the FM at all. Thus, they actually could sell us three Dr.I or make propeller/engine mods available (Now THAT would be cool!). As of now, we just have the slowest one, the „early bird“. As we have a late war scenario in FC, having the faster (and maybe more rare; as said, I find few references for the 2.4 meter pitch prop) that can do 110 mph would be suitable. But:

This!

 

I‘m sure everyone at 777 put this as no.1 priority for 2020. ?

 

We know exactly how willing they are to do full FM reviews, so let's keep expectations realistic and down to a minimum. I'm not saying that they don't want to (even the D.IIIau engines were on the table at some point, but again quickly forgotten), just that there are no man-hours set aside for it. Quick and dirty is what we'll get regardless of how accurate Chill's measurements are.

 

So what I think is most important to produce is the top IAS at sea level, or the top TAS at any altitude.

 

 

At the moment I have this:

 

 

I'm assuming 165km/h TAS at 4000m, as 165km/h IAS at that altitude would make it a rocketship indeed.

 

For the record: this is the same book that has the Halberstadt CL.II at 165km/h at 5000m, although it does take 40 minutes to get to that altitude.

 

 

And in Flying Circus:

 

 

 

So we're off by some 5km/h TAS at 4000m, which I would assume is some 10km/h IAS/TAS at sea level. Hence, Chill's original estimation of 175km/h at sea level appears to be spot on. So bring back the pre-nerf Dr.I (178km/h) and we're all set. Work required: 5 minutes of coding, one week of testing and we can have it in the next update.

 

And sure, the RPM will be wrong compared to measurements made today, but at this point there's enough conflicting data (in the manual provided by @SeaW0lf) to have plausible deniability.

[Chill31]

Quote

 have the LeRhone 9Jb 120hp in my Dr1 and an exact copy of the original Axial propeller and that gives me static rpm of around 1200 my rpm pointer is flexing 50 rpm up and down. Flying I operate between 1200-1300 rpm and in maneuvers going down I just reduce the throttle by feeling. But it looks like the the rpm is always between 1200-1300 when flying what ever position i put the throtlle

This from Mikael C

 

 

[unreasonable]

Replying to @J5_Hellbender-Sch27b above: Far too many heroic assumptions, making deniability not very plausible.  

 

132 kph CAS (GUI - presumably some generic BoX calculation) converts to 161.3 TAS at 3999m,  (using https://aerotoolbox.net/airspeed-conversions) your dial is reading past 160. When I run this on autolevel at 1280 rpm - the max I can get - I am reading 132 on the GUI and the dial  reads ~162 (better lighting than your screenshot).  So we are not off your 165 datum by 5 kph but nearer 3

 

More importantly, I am really not sure what that "conversion" is supposed to be: at 100m I get 158 on the GUI and 158 on the dial.  So the 4000m TAS is, compared to the SL, ~162/158, ie  1.025 times: it  is higher.  So if you want to convert an extra 3 kph TAS/anenometer speed at 4000m to SL value, should it not be less, not more?   3/1.025 = 2.9  

 

Essentially the FC Dr.1 is currently ~ 3kph off your datum, ie 1.8% lower,  It is the pre-nerf Dr.1 that is off. Barring a wholesale change of attitude towards FC by the developers it is hard to see any changes being made.  As of now I am not confident that there will be any more FC at all: but who knows.

 

 

 

 

 

 

 

 

Edited December 29, 2019 by unreasonable

[Garven]

34 minutes ago, unreasonable said:

132 kph CAS (GUI - presumably some generic BoX calculation) converts to 161.3 TAS at 3999m,  (using https://aerotoolbox.net/airspeed-conversions) your dial is reading past 160. When I run this on autolevel at 1280 rpm - the max I can get - I am reading 132 on the GUI and the dial  reads ~162 (better lighting than your screenshot).  So we are not off your 165 datum by 5 kph but nearer 3

Out curiosity I wanted to see the result I got using a different online conversion tool that I was using to calculate TAS for the SPAD 13 and this one is giving me 166.6kmh TAS.   https://www.wolframalpha.com/input/?i=idicated+airspeed+calculation&assumption={"F"%2C+"IASToTAS"%2C+"v"}+->"132kmh"&assumption="FSelect"+->+{{"IASToTAS"}}&assumption={"F"%2C+"IASToTAS"%2C+"H"}+->"3999m"  

I'm confused by the different results I'm getting.

[unreasonable]

That is quite a big difference! The Wolfram Alpha calculator you are using is showing slightly different values for the atmosphere than I get looking at  https://www.digitaldutch.com/atmoscalc/  so either they are using a different definition of standard atmosphere and/or a different formula for those values. I have no idea if that is enough to explain the difference.  That page also does not show the actual formula used: aerotools does.

 

Given that the aerotools calculator corresponds to the values in FC I assume the game is using the same formulae so I plan plan to stick with that.

[ZachariasX]

4 hours ago, J5_Hellbender-Sch27b said:

I'm assuming 165km/h TAS at 4000m, as 165km/h IAS at that altitude would make it a rocketship indeed.

 

This is indeed much faster than what they measured in the trials mentioned above. The problem I have with such a source that it  is very specific on the airspeed and at the same time gruesomely imprecise about the most important factor, the power plant.

 

In this sense, your source doesn‘t tell you anything of value, other than the author  being good at making up plausible numbers. This is like stating the „Bf-109“ top speed as 389.3 mph when powered either with a DaimlerBenz or a Merlin engine.

 

If you are specific about what you want in terms of speed, you should also say what you have hardware installed as hardware. The faster you let it go, the slower it will climb. You cannot just cherry pick your data just they originate „from a Dr.I“, when in fact you could be comparing effectively different aircraft.

 

This is especially wrong if you have a Clerget instead of a Uberursel. The Clerget will give you more torque at the same rpm, hence they installed not only a larger, but also a steeper propeller and both can translate added torque in added thrust. Thus a Clerget Dr.I is as similar to an Oberursel Dr.I as a DB603 Bf109 is to a DB605 powered one.

 

 

Edit: I have to correct myself. The numbers stated in your source are not plausible. 103+ mph at 4000 meters would give it a sea level speed of nearly 125 mph. No way.

Edited December 29, 2019 by ZachariasX

[unreasonable]

57 minutes ago, ZachariasX said:

 

 

 

Edit: I have to correct myself. The numbers stated in your source are not plausible. 103+ mph at 4000 meters would give it a sea level speed of nearly 125 mph. No way.

 

What conversion are you using to deduce that?

 

Current Dr1 does 162kph anenometer speed at 4,000m, 158 at 100m at the best rpm I can get. Ie TAS/amenometer speed is only a little different through the altitude range, and actually lower at SL. 

[BMA_Hellbender]

3 hours ago, unreasonable said:

Essentially the FC Dr.1 is currently ~ 3kph off your datum, ie 1.8% lower,  It is the pre-nerf Dr.1 that is off. Barring a wholesale change of attitude towards FC by the developers it is hard to see any changes being made.  As of now I am not confident that there will be any more FC at all: but who knows.

 

I agree, though I believe that a -3kph TAS at 4000m for the Dr.I is far more significant than a +2kph IAS at sea level for the Camel, which is currently the case.

 

I have to tell you: I have very little bias towards a faster Dr.I, due to the whole Voltol debacle, the fact that all Central planes carry parachutes that deploy without failure, that action should be taking place over Central lines rather than Entente lines (this largely up to mission builders, really) and that we absolutely cannot have a Fokker Dr.I that is perceived as "better" than even the vanilla Fokker D.VII, which MvR was begging to receive right before he died.

 

 

1 hour ago, ZachariasX said:

Edit: I have to correct myself. The numbers stated in your source are not plausible. 103+ mph at 4000 meters would give it a sea level speed of nearly 125 mph. No way.

 

I think you're mixing up TAS and IAS. IAS = TAS at sea level, but the difference becomes larger as altitude increases and pressure decreases and the difference between IAS at sea level and TAS at altitude becomes larger as speed increases.

 

Currently in Flying Circus the Dr.I has a TAS of 161km/h at 4000m and a TAS=IAS of 165km/h at sea level. 

 

The source states 165km/h TAS at 4000m, which would optimistically give us a TAS=IAS of 170-175km/h at sea level.

 

 

Again, I'm not in charge of anything here (though recently you could make a case that I actually am the so-called "key player" I've been accused of).

 

What I would do, still, is follow @SeaW0lf's suggestions, who flies both of these machines, and have the Camel's RPM adjust to 1400 (down from 1460) and the Dr.I to 1250-1300 (up from 1230) to appease everyone.

 

 

This would look like this, all speeds at sea level.

 

Sopwith Camel:

 

FROM 117mph (188km/h) @ 1460 RPM

 

 

TO 113mph (182km/h) @ 1400 RPM

 

 

 

Fokker Dr.I:

 

FROM 165km/h @ 1230 RPM 

 

 

TO 170-175km/h @ 1250-1300 RPM (speed measured in a shallow full throttle dive from around 100m)

 

 

 

This is all ballparking and done to avoid needing actual FM reviews to fix the rotaries, although you will find top speed figures for basically all the figures listed above, both the 188km/h and the 182km/h Camel, as well as the 165km/h and the 175km/h Dr.I.

 

P.S. With apologies to Chill for hijacking his thread, but let's just say it keeps bumping his amazing videos to the top.

Edited December 29, 2019 by J5_Hellbender-Sch27b

[ZachariasX]

32 minutes ago, unreasonable said:

What conversion are you using to deduce that?

Taking from the LeRhone airspeed curves on the S6. At least we have consistent data there, something that is often missing. And there speed differences are ~20% between 13‘500 ft. and sea level. I‘d expect similar rotaries performing relatively alike.

 

If you assume the speed delta to be smaller, say just 110 mph for sea level speed, you‘d actually make the Dr.I have more drag. And I don‘t think it is that bad in this department. Chills Dr.I is actually handsomely efficient at 100 mph. We‘re clearly nor aerodynamically limited at that speed. Thus I am not even that generous in giving the Dr.I the same speed for added power as the S6 exhibits. I would expect the Dr.I being somewhat better.

 

 

8 minutes ago, J5_Hellbender-Sch27b said:

What I would do, still, is follow @SeaW0lf's suggestions, who flies both of these machines, and have the Camel's RPM adjust to 1400 (down from 1460) and the Dr.I to 1350 (up from 1320) to appease everyone.

I see your point and it makes perfect sense to me. I‘m definitely not against mending this issue in a way that you guys suggest. Even if it is done with the sledge hammer.

 

Personally, I‘d love having fixed pitch prop physics properly modeled. It would greatly help FC. In other sims (no, not that one), exchanging props and having different performance is with us for some time now and its a nice thing to have.

Edited December 29, 2019 by ZachariasX

[unreasonable]

I was not assuming anything, just saying what top speeds I could get in the FC Dr1 in level flight autopilot, at mix for max rpm, throttle fully forwards, reading from the anenometer, which is TAS in the game (no instrument errors).   Edit: actually I am assuming one thing: when the developers give maximum speeds they are using the game's level autopilot to generate them.

 

100m = 158kph  4,000m = 162kph   maybe someone with a lighter touch on the mixture lever might get a bit more.  I have to assume that sources that give top speeds, if they have any meaning at all (discuss  ) must be referring to speeds in level flight and not in a shallow dive.

 

Edited December 29, 2019 by unreasonable

[SeaW0lf]

13 minutes ago, J5_Hellbender-Sch27b said:

What I would do, still, is follow @SeaW0lf's suggestions, who flies both of these machines, and have the Camel's RPM adjust to 1400 (down from 1460) and the Dr.I to 1350 (up from 1320) to appease everyone

 

These planes have their own rpm / speed ratio. For example, the ROF Camel gets to 1220rpm at sea level and 168/km/h. If you bring the FC Camel to 1220rpm, it will run roughtly at 160km/h. So we can't ask them to reduce the rpm to get to what we want. The results are not in accordance.

 

And 180km/h for the Camel seems to be for the 110hp one if we take into account the data we are getting from Chill's engine / prop. They could rename the Camel and call it Camel Le Rhone 9J 110hp, and I'm sure some people would love it, but then are we getting the Camel 130hp at some point? I assume we will never get it, then what turns to be is a nerfing just like the last one, which the aggravation of making it a Dr1 fodder if they ever unerf the Fokker.

 

What I said was in the context of real life engines, that 1460rpm was unthinkable, then they should bring it back to +-1400rpm (it matters in shallow dives, since currently it is a glass engine) and tweak it to 185km/h.

 

I would wait for Chill's developments, but they could bring the Camel to 185km/h as of now in my opinion, preferably reaching 1380-90rpm.

[ZachariasX]

51 minutes ago, J5_Hellbender-Sch27b said:

What I would do, still, is follow @SeaW0lf's suggestions, who flies both of these machines, and have the Camel's RPM adjust to 1400 (down from 1460) and the Dr.I to 1250-1300 (up from 1230) to appease everyone.

Hmmm. I wouldn‘t touch the Camel. I don‘t see the need and I fly both of the machines.

 

And the appeasing part is a slippery slope we‘ve been down before (and the devs came to regret). I still like the „nerf patch“ because it made RoF a much better MP game. The nerf patch was needed to mask general shortcomings of RoF’s general way of creating flight models. Giving certain planes documented speeds made them able to pull obscene maneuvers. It was just silly. Mileage on this varies of course.

 

As said, you could just feature engine mods for the Dr.I and peeps can choose what they like. We have that on other planes as well.

 

6 minutes ago, SeaW0lf said:

What I said was in the context of real life engines, that 1460rpm was unthinkable, then they should bring it back to +-1400rpm (it matters in shallow dives, since currently it is a glass engine) and tweak it to 185km/h.

They should adjust it to actual rpm reflecting real propellers. What we have now in rpm/airspeed looks like a relatively arbitrary combination to reach certain performance figures. RoF differs internally from BoX, so it looks logical that rpm/airspeed relations get skewed.

 

Edit: bloody merge...

Edited December 29, 2019 by ZachariasX