Fokker Dr.I Discussion

[Chill31]

6 hours ago, Holtzauge said:

On a more serious note, I assume you have a pitot somewhere to get the total pressure and using the static ports on the pitot you have or getting one that has static port and connecting those to your instruments seems like well invested money. In addition, I guess without proper static ports the accuracy of your altimeter will suffer as well?

---The ere are no static ports on the pitot. There is a separate connection on the back of the instrument for the static line.  A lot of guys fly their Dr1s with no airspeed indicator, and i do the same for the most part.  As long as the gunfight is on the horizon or lower, you will keep flying

 

About the rationale for a 10 s stationary turn time in a Dr1: I hear what you are saying about doing extrapolations from the 2:02 to 2:12 s sequence in your video but frankly I think there are to many unknowns right now given that speed was not constant and that the input is shaky since both the GPS GS you have access to is erratic and you seem to have (to put it mildly!) issues with the static input for IAS estimation. 

---The airspeed results are close enough to know that your model should be turning faster, and i think you have factored in a little too much drag.  5 mph difference won't make 4 (38% increase in time) seconds difference. Can you get your model to turn in 10-11 seconds at any speed? 

 

About Old Rhinebeck Dr1's: Check out their site info. They have 3 of them and only one with the Continental. The other two have Le Rhone engines. I will not judge their way of presenting the weights and if they are wrong or not. Anyway it does not matter that much: The weight added by the heavier Continental engine (ca 15% to the assumed T/O weight 575 Kg) is nothing compared to the power added (2.5 times more than the 85 hp you have) and the resulting deltas are as follows: Added weight adds about 3 s to turn time while the power gain cuts 6 s off giving a total gain of 3 s. So, if anything, the "fat girl" looks to be reckoned with and a 225 hp engine in a Dr1 is something I suspect most pilots in the Luftstreitkräfte would have killed for. As they say: "It ain't over till' the fat lady sings" and boy, can that gal sing!

--Hp doesn't translate directly.  Consider this, I am getting almost the same performance from my 85 hp le rhone as I was from 160 hp Lycoming (with a more coarse pitch propeller, I think I would exceed it).  The 220 hp continental has about the same displacemt as the 80 rhone, but it spins a propeller with an finer pitch to get more rpm (horsepower), thus sacrificing thrust by some margin.  So while it does have more hp, it is not producing a proportional increase in thrust.  At any rate, my turns out perform baldeagles numbers by a wide margin, so the only thing that can make such a difference is power to weight.  

 

 

 

 

[Holtzauge]

11 hours ago, Chill31 said:

The airspeed results are close enough to know that your model should be turning faster, and i think you have factored in a little too much drag.  5 mph difference won't make 4 (38% increase in time) seconds difference. Can you get your model to turn in 10-11 seconds at any speed? 

 

Hp doesn't translate directly.  Consider this, I am getting almost the same performance from my 85 hp le rhone as I was from 160 hp Lycoming (with a more coarse pitch propeller, I think I would exceed it).  The 220 hp continental has about the same displacemt as the 80 rhone, but it spins a propeller with an finer pitch to get more rpm (horsepower), thus sacrificing thrust by some margin.  So while it does have more hp, it is not producing a proportional increase in thrust.  At any rate, my turns out perform baldeagles numbers by a wide margin, so the only thing that can make such a difference is power to weight. 

 

No, nothing in your video indicates that I have factored in too much drag. In addition, it’s not a question of how close the speeds are. The issue is that in a sustained turn the speed is held constant. What you posted in the video is a so-called instantaneous or momemtaneous turn in which the speed drops as you turn allowing you to turn faster than is possible in a stationary turn rate turn. As I posted before, the C++ Dr1 model I have can also generate a 10 s turn depending on the entry speed and the assumed speed loss in the turn. But again, that is not a sustained turn but a momentaneous turn, just like the one you posted in your video.

 

About converting the available horsepower to thrust: it’s simply a question of matching the propeller to the power output. Not only that, you need to decide if you want to optimize for speed or climb since the selected pitch will be different producing a different mix of climb and top speed depending on which way you go. This is also why it is sometimes difficult to compare flight test data from two aircraft with the same power. However, unless one is grossly incompetent in selecting propellers, there is no way that a 85 hp Dr1 outperforms a 225 hp Dr1 even if a 170 lb heavier engine and additional structure to carry that is added. Any designer would jump at that opportunity and if Anthony Fokker had access to a 225 hp (be it a 170 lb heavier one than the Le Rhone) he could have designed a Dr1 that would have wiped the floor with the competition.

 

But I think your last statement is correct: It’s all about P/W only you seem to have it backwards: Even with your highest assumed weight 1800 lb (which seems outrageous for adding a 170 lb heavier engine) the 225 hp Old Rhinebeck Dr1 has a much higher P/W ratio than your 85 hp Dr1. And finally, you can’t compare yours and baldeagle’s turns: He says about 18 s for a sustained turn rate turn while you have done a 10 s momentaneous turn rate turn. Apples and oranges.

[emely]

3 hours ago, Holtzauge said:

. Any designer would jump at that opportunity and if Anthony Fokker had access to a 225 hp (be it a 170 lb heavier one than the Le Rhone) he could have designed a Dr1 that would have wiped the floor with the competition.

Fokker could use a reduction gear in this situation, to achieve optimal propeller speed.  However, those who manufacture such aircraft today do not have such an opportunity.

[Holtzauge]

1 hour ago, emely said:

Fokker could use a reduction gear in this situation, to achieve optimal propeller speed.  However, those who manufacture such aircraft today do not have such an opportunity.

 

Yes, a reduction gear could be used but at whatever rpm you run the propeller shaft you will still need more blade area to absorb the increased power so in the end you will still have to work with diameter, pitch, number of blades and blade area to absorb the power today just as it was back then.

[Chill31]

11 hours ago, Holtzauge said:

 

No, nothing in your video indicates that I have factored in too much drag. In addition, it’s not a question of how close the speeds are. The issue is that in a sustained turn the speed is held constant. What you posted in the video is a so-called instantaneous or momemtaneous turn in which the speed drops as you turn allowing you to turn faster than is possible in a stationary turn rate turn. As I posted before, the C++ Dr1 model I have can also generate a 10 s turn depending on the entry speed and the assumed speed loss in the turn. But again, that is not a sustained turn but a momentaneous turn, just like the one you posted in your video.

--so model what you see in my video. Repeat it with your C++ model.  I'd like to see if you can repeat it. If you can, we may be able to provide a starting point for FC devs to modify the Dr.I.

 

About converting the available horsepower to thrust: it’s simply a question of matching the propeller to the power output. Not only that, you need to decide if you want to optimize for speed or climb since the selected pitch will be different producing a different mix of climb and top speed depending on which way you go. This is also why it is sometimes difficult to compare flight test data from two aircraft with the same power. However, unless one is grossly incompetent in selecting propellers, there is no way that a 85 hp Dr1 outperforms a 225 hp Dr1 even if a 170 lb heavier engine and additional structure to carry that is added. Any designer would jump at that opportunity and if Anthony Fokker had access to a 225 hp (be it a 170 lb heavier one than the Le Rhone) he could have designed a Dr1 that would have wiped the floor with the competition.

--Torque is a better way to compare airplane engines, because it takes torque to move air.  The 80 Rhone moves as much air as the 160 hp Lycoming...the 225 conti would need to weigh 420 lbs to have a proportional torque increase for its weight increase over the 80.  All of this is beside the point though.  The point is ORAs Dr.Is are not very accurate examples of the Fokker Dr.I, and relying on them for data is not going to be productive. 

 

But I think your last statement is correct: It’s all about P/W only you seem to have it backwards: Even with your highest assumed weight 1800 lb (which seems outrageous for adding a 170 lb heavier engine) the 225 hp Old Rhinebeck Dr1 has a much higher P/W ratio than your 85 hp Dr1. And finally, you can’t compare yours and baldeagle’s turns: He says about 18 s for a sustained turn rate turn while you have done a 10 s momentaneous turn rate turn. Apples and oranges.

--1800 lbs is not tough to do. Add brakes, modern instruments, heavy tubing, etc. It adds up quickly.  What is the turn rate at 2 Gs and 55 mph? What is it at 2Gs and 50 mph? It wasn't like I converted 30-40 mph into turn rate. It was maybe 5-7. So run the program at at various speed and see if you get about 10 seconds. I'll do it in a well established turn on my next flight and see what I get, but I doubt it will increase by 80%.

The FC dr1 should be much more docile near stall, and i think that is one of the bigger problems with it.  People would fight it a lot slower if it handled like the real bird.

 

They may have the induced drag model off slightly, but given the level flight speed and the speed at the top of the loop, I think it is not off by too much.  

[emely]

1 hour ago, Chill31 said:

The FC dr1 should be much more docile near stall, and i think that is one of the bigger problems with it.  People would fight it a lot slower if it handled like the real bird.

Chill, you have to buy all the other FC aircraft, and fly on them writing down the parameters in order for them to become "obedient" too :-)) Or do you want only one to become obedient to Dr1 and the rest to be naughty? ?

[Holtzauge]

9 hours ago, Chill31 said:

The FC dr1 should be much more docile near stall, and i think that is one of the bigger problems with it.  People would fight it a lot slower if it handled like the real bird.

 

They may have the induced drag model off slightly, but given the level flight speed and the speed at the top of the loop, I think it is not off by too much.  

 

For sure, as far as I can tell it's only a small adjustment that needs to be done. In addition, it’s not just the Dr1 that is affected but also the Camel since according to Javier Arango's tests the Camel's sustained turn rate time is also longer than it takes in FC.

 

That being said, as far as I can tell from comparing the Dr1 and Camel the relative performance in FC seems to be quite in order since both are turning better than expected. In addition to that I still think that in general it seems like the aircraft in FC should bleed more energy when you manouver but if they adjust the induced drag then that will probably come by itself. Also, I assume the induced drag issue is a general model thing affecting all aircraft meaning they will probably all turn a bit slower if they decide to tune this.

 

Maybe all this comes across as sounding too negative and critical but that is just the nature of engineers: we look for problems and try to solve them, all that is good is never mentioned. And why should it? Our motto is if it works then don’t fix it!

 

Anyway, if they ever make a second installment on FC with new aircraft I will snap it up in a heartbeat. This is a great simulator and I hope they keep developing it.

 

If you have the time, it would be very interesting to hear more about the Dr1 from the pilot’s perspective in terms of stick forces, roll rates and general handling both in air and landing and taxing etc. As an example how is roll rate affected by speed? How difficult is it to counter the torque? I assume it’s OK at most speeds but gets difficult when you go slow and manouver? One thing that I assume the Dr1 has going for it is the benign stall characteristics? IRL a Dr1 pilot would probably feel more confident pushing the envelope than a Camel pilot that risks a nasty stall/spin when pushing the limits?

Edited June 5, 2020 by Holtzauge

[Chill31]

5 hours ago, Holtzauge said:

If you have the time, it would be very interesting to hear more about the Dr1 from the pilot’s perspective in terms of stick forces, roll rates and general handling both in air and landing and taxing etc. As an example how is roll rate affected by speed? How difficult is it to counter the torque? I assume it’s OK at most speeds but gets difficult when you go slow and manouver? One thing that I assume the Dr1 has going for it is the benign stall characteristics? IRL a Dr1 pilot would probably feel more confident pushing the envelope than a Camel pilot that risks a nasty stall/spin when pushing the limits?

Roll rate deteriorates with speed, by how much, i haven't measured.  Adverse yaw increases by a lot too as it slows down.

 

The torque of the engine is not too difficult to counter.  It has about the same torque as the Lycoming 160hp.  The gyroscopic effects are pronounced when maneuvering,  and you can see in this video just how much it really takes to counter it.  

 

 

I haven't flown a Camel, but I have flown a Ryan OTW, which is supposed to have the same airfoil as the Pup or Camel.  It had a relatively easy sta as well.  Contrast that with the fat wing on the RV8 which has a very pronounced stall and nose drop.  For sure, wing shape plays an important role in stall characteristics, but without actually flying the Camel, i couldn't give an accurate answer as to how it stalls. 

 

I can say that the Dr1 lives to fight slow.  I xan only imagine what it will do with 50% more power!

[Canvas25]

Simply awesome. Thank you very much for sharing - you are probably in an unique position here.

 

 

[DakkaDakkaDakka]

We are *all* in a unique position here, thanks to Chill. He not only has an authentic Dr.1 powered by an authentic engine, but he is interested in our goofy little computer flight sim and willing to go out and literally spend time and treasure to QA test our video game.

 

That's pretty amazing, and I'm extremely grateful. I hope we all are!

[Trooper117]

Great little video... the 'Air shoot' video is really nice too!

[SKG51_Siggie]

Ich warte darauf, dass der Dr1 repariert wird!

Kein Flugzeug, weder damals noch heute, würde fliegen oder mit einem Aufzug entfernt werden, der um 45 Grad nach unten gesetzt ist.

Jedes Flugzeug sollte mit einer bestimmten Geschwindigkeit gerade fliegen und nicht klettern oder absteigen. Seit RoF fliegen wir die Dr1 auf diese Weise!


Damals wurde dies mehrfach kritisiert und bewiesen und ist noch nicht behoben. Ich verstehe nicht, warum die Programmierer dies nicht behoben haben.

Es gibt in dieser Hinsicht Literatur über die Dr1. sowie die Grundeinstellung des Flugzeugs zu dieser Zeit.

Warum sind die Entwickler solche Ignoranten?
 

Edited June 10, 2020 by III./ZG15_Siggie

[J5_Adam]

1 hour ago, III./ZG15_Siggie said:

Ich warte darauf, dass der Dr1 repariert wird!

Kein Flugzeug, weder damals noch heute, würde fliegen oder mit einem Aufzug entfernt werden, der um 45 Grad nach unten gesetzt ist.

Jedes Flugzeug sollte mit einer bestimmten Geschwindigkeit gerade fliegen und nicht klettern oder absteigen. Seit RoF fliegen wir die Dr1 auf diese Weise!


Damals wurde dies mehrfach kritisiert und bewiesen und ist noch nicht behoben. Ich verstehe nicht, warum die Programmierer dies nicht behoben haben.

Es gibt in dieser Hinsicht Literatur über die Dr1. sowie die Grundeinstellung des Flugzeugs zu dieser Zeit.

Warum sind die Entwickler solche Ignoranten?
 

 

Please post original documents that support this

[Chill31]

10 minutes ago, J5_Adam said:

 

Please post original documents that support this

I think he is referring to the down elevator deflection in the visual model of the Dr.1.  In this case, he is correct that the depicted elevator position is quite extreme.

 

1 hour ago, III./ZG15_Siggie said:

Ich warte darauf, dass der Dr1 repariert wird!

Kein Flugzeug, weder damals noch heute, würde fliegen oder mit einem Aufzug entfernt werden, der um 45 Grad nach unten gesetzt ist.

Jedes Flugzeug sollte mit einer bestimmten Geschwindigkeit gerade fliegen und nicht klettern oder absteigen. Seit RoF fliegen wir die Dr1 auf diese Weise!


Damals wurde dies mehrfach kritisiert und bewiesen und ist noch nicht behoben. Ich verstehe nicht, warum die Programmierer dies nicht behoben haben.

Es gibt in dieser Hinsicht Literatur über die Dr1. sowie die Grundeinstellung des Flugzeugs zu dieser Zeit.

Warum sind die Entwickler solche Ignoranten?
 

The Dr.1 ALWAYS flies with some nose down elevator.  I am working on a stability demonstration video of my Dr.1.  It behaves like the aircraft in FC/ROF, but the elevator does not appear to be deflected in such an extreme way.  

[J5_Adam]

15 minutes ago, Chill31 said:

I think he is referring to the down elevator deflection in the visual model of the Dr.1.  In this case, he is correct that the depicted elevator position is quite extreme.

 

The Dr.1 ALWAYS flies with some nose down elevator.  I am working on a stability demonstration video of my Dr.1.  It behaves like the aircraft in FC/ROF, but the elevator does not appear to be deflected in such an extreme way.  

 

I realize that about the visual elevator deflection. What he's incorrect about is how he says, all aircraft are designed to fly a certain way. All I've heard about the Dr1 is that you always have to be flying that aircraft or it flies you! Take your hands off the control column of many WW1 birds and they'll loop on you. 

 

I don't understand all of the silly complaints in here. Just fly FFS

[Cynic_Al]

3 hours ago, Chill31 said:

I think he is referring to the down elevator deflection in the visual model of the Dr.1.  In this case, he is correct that the depicted elevator position is quite extreme.

 

As I've tried to explain previously,  the control deflection rendered in-game is purely a representation of the force being applied to the joystick,  it does not imply that amount of deflection would be needed or even possible in flight.  The game could be programmed to compensate for airspeed, so that the faster the plane flies,  less control deflection is needed and less deflection can be achieved.  While such functionality would be more realistic, inevitably it would cause players to think something were not working properly,  so best left as is.

[SKG51_Siggie]

Sie müssen nur in eine Bibliothek
gehen, wo Sie genügend Informationsmaterial finden.
Außerdem gibt es genügend Filmmaterial auf YT, um mich zu bestätigen.
Es ist auch meine Aufgabe, und seit über 30 Jahren, Flugzeuge fliegen zu lassen.
Was die Programmierer ignorieren, wird in der ersten Sesmester Aerodynamik gelehrt.

[LukeFF]

38 minutes ago, III./ZG15_Siggie said:

Sie müssen nur in eine Bibliothek
gehen, wo Sie genügend Informationsmaterial finden.
Außerdem gibt es genügend Filmmaterial auf YT, um mich zu bestätigen.
Es ist auch meine Aufgabe, und seit über 30 Jahren, Flugzeuge fliegen zu lassen.
Was die Programmierer ignorieren, wird in der ersten Sesmester Aerodynamik gelehrt.

 

Please post your replies here in English, so we can understand what you are saying.

[BMA_Hellbender]

4 hours ago, Cynic_Al said:

As I've tried to explain previously,  the control deflection rendered in-game is purely a representation of the force being applied to the joystick,  it does not imply that amount of deflection would be needed or even possible in flight.  The game could be programmed to compensate for airspeed, so that the faster the plane flies,  less control deflection is needed and less deflection can be achieved.  While such functionality would be more realistic, inevitably it would cause players to think something were not working properly,  so best left as is.

 

I'm curious to know why you would think that. If less control deflection can be achieved at higher airspeeds, as is already the case on the WWII machines in this game, it would lead to less extreme player inputs and wing failures under g load.

[Cynic_Al]

1 hour ago, J5_Hellbender said:

 

I'm curious to know why you would think that. If less control deflection can be achieved at higher airspeeds, as is already the case on the WWII machines in this game, it would lead to less extreme player inputs and wing failures under g load.

 

Rendered Deflection != Effective Deflection.  That was my point.

[unreasonable]

7 hours ago, Cynic_Al said:

 

As I've tried to explain previously,  the control deflection rendered in-game is purely a representation of the force being applied to the joystick,  it does not imply that amount of deflection would be needed or even possible in flight.  The game could be programmed to compensate for airspeed, so that the faster the plane flies,  less control deflection is needed and less deflection can be achieved.  While such functionality would be more realistic, inevitably it would cause players to think something were not working properly,  so best left as is.

 

The deflection required from the Dr1 elevator is affected by speed - the faster you fly, at a given altitude, the more forward stick pressure you need to stay level.  This is because with a CoL in front of the CoG the more lift you add the more the nose will pitch up.  This may be countered by the tail moment to an extent but not equally.  I can fly level (slight phugoid) with zero forward or backward  stick pressure in the FC  Dr1 from about 200m to 7.500m, if I find the right rpms.  When I do that the elevator visually is slightly down.

 

The CAS shown on the HUD in each case is about the same. The ~TAS shown on the wing anemometer increases with height. 

 

The most likely explanation is not that the developers are all idiots,  omitting basic aerodynamic forces, as you and our new German speaking friend would have us believe, but that the balance of the game Dr.1 is a more tail heavy than that of Chill.  

 

 

 

Edited June 11, 2020 by unreasonable

[Cynic_Al]

11 minutes ago, unreasonable said:

The deflection required from the Dr1 elevator is affected by speed - the faster you fly, at a given altitude, the more forward stick pressure you need to stay level.  This is because with a CoL in front of the CoG the more lift you add the more the nose will pitch up.  This may be countered by the tail moment to an extent but not equally.  I can fly level (slight phugoid) with zero forward or backward  stick pressure in the FC  Dr1 from about 200m to 7.500m, if I find the right rpms.  When I do that the elevator visually is slightly down.

 

The CAS shown on the HUD in each case is about the same. The ~TAS shown on the wing anemometer increases with height. 

 

The most likely explanation is not that the developers are all idiots,  omitting basic aerodynamic forces, as you and our new German speaking friend would have us believe, but that the balance of the game Dr.1 is a more tail heavy than that of Chill.  

 

 All I can say to that is read what I actually write, not what you think or wish I'd written.

[unreasonable]

7 minutes ago, Cynic_Al said:

 

 All I can say to that is read what I actually write, not what you think or wish I'd written.

 

"The game could be programmed to compensate for airspeed, so that the faster the plane flies,  less control deflection is needed and less deflection can be achieved. While such functionality would be more realistic,...."

 

You could program everything to fly straight and level all the time, but it would not be more realistic.  Very simple - if the CoG is behind the CoL, the faster the plane flies at a given altitude, the more control deflection is needed to fly level. 

 

Given that you have previously made the preposterous assertion that precession is not modeled in FC/Box,  you will perhaps understand why your pronouncements on what might be more or less realistic should not be taken seriously.  How people treat my pronouncements is entirely a matter for them.

[Atomic_Spaniel]

3 hours ago, unreasonable said:

 

The deflection required from the Dr1 elevator is affected by speed - the faster you fly, at a given altitude, the more forward stick pressure you need to stay level.  This is because with a CoL in front of the CoG the more lift you add the more the nose will pitch up.  This may be countered by the tail moment to an extent but not equally.  I can fly level (slight phugoid) with zero forward or backward  stick pressure in the FC  Dr1 from about 200m to 7.500m, if I find the right rpms.  When I do that the elevator visually is slightly down.

 

I had always wondered if some of the nose-up pitching was also from the drag of the top wing producing a couple around the CoG?

[WolfPack_Wngover]

On 7/22/2018 at 3:26 PM, Chill31 said:

  I think that is the weakest part of the pitch model and could probably be satisfied by doubling whatever figure they are using for horizontal tail incidence.

??