PDA

View Full Version : Fokker D.XXI performance - in game and in reality



TinyTim
05-20-2010, 05:49 AM
Hey gents,

I gave this bird a couple of rides last days. Beautifully built 3D model, fascinating cockpit, very nicely done damage modelling, unique features (random gunsight, tracer option). Bravo and big thanks to TD!

However, since it is eyebrows-liftingly slow in the sim compared to competition, maybe an interesting discussion on whether that was the case in reality too could be made (or, in case it's established wasn't, provide TD with the needed data in order to correct the performance).

I don't know any reliable sources about real D.XXI testing, but the in game Fokker's performance is somewhere on par with biplane fighters with fixed gear and with engines of similar power - Gladiator and Cr.42. In its fastest version (the S3_early) it manages barely over 400kph at optimal altitude, being even a tad slower than a Cr.42.

I certainly wouldn't expect a fighter with fixed landing gear and 850hp engine to be a stellar performer on par with all those new machines with retractable gear (G.50, I-16, Hurri, Morane etc), but there must certainly be a big reason for a monoplane not be considerably faster the biplanes with fixed gear and comparably powerful engine.

They say IL-2 compare shouldn't be taken as a Holy Grail, but as far as speed and climb goes, it's pretty accurate in my experience (this is the best performing XXI version):

D.XXI vs Cr.42:

http://www.shrani.si/f/m/ul/4QBouKjp/xxivscr42.jpg

D.XXI vs J8A (Gladiator):

http://www.shrani.si/f/3x/91/c6GAiB6/xxivsglad.jpg

If we compare the D.XXI to Ki-27, we can see the Nate to be about 60kph (!) faster with considerably weaker engine (650hp) and lower weight:

D.XXI vs Ki-27:

http://www.shrani.si/f/3X/a9/O7nU4r7/dxxivski-27.jpg

I tested these 4 aircraft for ground level speed:

http://www.shrani.si/f/18/Ni/21RkBbLy/1-glad.jpg

http://www.shrani.si/f/2D/4c/3UkgbWU5/2-42.jpg

http://www.shrani.si/f/1q/KW/3JPuHtcv/4-xxi.jpg

http://www.shrani.si/f/3w/e3/4V0KfcVA/3-nate.jpg

So we are left with three possibilities:

1. Everything is modelled as close to historical values as possible.
Thich leaves us with a valid question - why was a monoplane D.XXI not faster in reality, especially compared to Gladiator and Fiat biplane fighters, which both had fixed gear (like the XXI) and similarly powered engine (850hp)?

2. Gladiator and Cr.42 are overmodelled in terms of performance.

3. D.XXI is too slow.

What do you guys think, and more importantly, can anyone provide any sources about real D.XXI testing? I don't have any literature dealing with the D.XXI and I don't understand Finnish (or Dutch for that matter), but, for example, performance data on Wikipedia claims the numbers are from book of Lentäjän Näkökulma & Thulinista Hornetiin. Max. speed is cited as 460khp, which sounds about right compared to the competition (somewhere inbetween the monoplanes with retractable gear and biplanes with fixed gear - all with similar engines). Does anyone have access to this book?

DKoor
05-20-2010, 05:56 AM
Sad truth is... that D21 isn't really considerably faster than contemporary Soviet bombers, but it is quite good for the role of an interceptor. Also as recon fighter.
All other roles such is patrolling, escort, sweep etc. it fails quite a bit... it is slower than Soviet opposition either that or is much inferior in terms of maneuverability thus negating its good sides.

But it sure is fun to fly and one of my fav fighters in spite of everything! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

JtD
05-20-2010, 05:59 AM
I can't check that in il2-compare myself for the moment, but I'd think that the Fokker is the heaviest of the contenders, which might explain the lower speeds.

Also, are the engine hp similarly distributed over altitude, or does for instance the Fokker have the 850 hp at sea level, while the Fiat has it at higher altitude?

JG53Frankyboy
05-20-2010, 06:07 AM
http://www.sci.fi/~ambush/faf/fokkerdxxi.html (http://www.sci.fi/%7Eambush/faf/fokkerdxxi.html)

it does fit the numbers of the link, in general....... sure, it depends on what "sources" you read, i also found higher numbers in performance.


what annoyes me most is that this game seems to have proplems with fixed propellers , planes with them have a realy bad acceleration and loose fast enginerevolutions in any manouver http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

TinyTim
05-20-2010, 06:27 AM
Take off weight, from IL-2 compare:

Fokker S3_early: 1970.01 kg
GladiatorMk1-J8A: 2016.01 kg
Fiat Cr42: 2200.8 kg
Ki-27-Ko: 1515 kg

I have no idea about altitude dependance of power output, so we can limit ourselves to ground level. We can see the Fokker is about as fast as heavier and considerably more draggier Fiat. I believe we can agree that top speed is much more affected by drag than by weight.

Guys, I don't want to give an impression I'm claiming a priori that sim is wrong. It may be correct, but then the question remains - how come the D.XXI wasn't faster in reality? There are sources that indicate D.XXI indeed was a poor performer, like the one Frakyboy posted. Why so? Where do these sources come from? There's however also sources claiming D.XXI could do 460kph at optimum altitude...

WTE_Galway
05-20-2010, 06:41 AM
Why assume becasue its a monoplane it should be faster than a comparable biplane ?

Check this link for example ...

http://www.flightglobal.com/pd...1932%20-%201079.html (http://www.flightglobal.com/pdfarchive/view/1932/1932%20-%201079.html)

Blackburn tested two virtually identical aircraft in 1932, same fuselage, some fixed undercarriage same engines, but one was configured as a monoplane and the other as a biplane. Test results showed that the estimated top speed of the biplane at sea level was 123 m.p.h. (198 km./h.), and that of the monoplane 124 m.p.h. (199 km./h.).

TinyTim
05-20-2010, 06:51 AM
Originally posted by WTE_Galway:
Why assume becasue its a monoplane it should be faster than a comparable biplane ?

Because that's what's generally true. Monoplanes generally were faster than biplanes, especially the ones that were of otherwise similar layout (fixed/retractable gear, similar engine(s) etc...). Speed was the main reason for conversion, despite the lower maneouverability.



Originally posted by WTE_Galway:
Check this link for example ...

http://www.flightglobal.com/pd...1932%20-%201079.html (http://www.flightglobal.com/pdfarchive/view/1932/1932%20-%201079.html)

Blackburn tested two virtually identical aircraft in 1932, same fuselage, some fixed undercarriage same engines, but one was configured as a monoplane and the other as a biplane. Test results showed that the estimated top speed of the biplane at sea level was 123 m.p.h. (198 km./h.), and that of the monoplane 124 m.p.h. (199 km./h.).

Interesting, thanks for sharing. Still,

firstly, it's just one instance. You can find a boat that's faster than a certain plane, yet you can't generalize it - planes are generally still faster than boats are. Biplane might have been built with a very thin and small wings, and monoplane with a big and thick one, so yes, in theory I agree, it's possible. But show me 1 example (apart from the one discussed in this thread) from WW2 era where comparable monoplane isn't considerably faster than a biplane.

secondly, from the article:
As the two machines have not yet been through their tests at martlesham, actual performance figures are not available, but the estimated performance figures are of interest...

M_Gunz
05-20-2010, 07:01 AM
Sources? Actual original sources?

JtD
05-20-2010, 07:03 AM
Thanks for the weight info, TT.

Googled the engines in the meantime, both the Gloster Gladiator and the Fokker D.XXI used the same engine, a Bristol Mercury VIII. So it might make the most sense to compare these two.

Regarding the weight, lift dependent drag does have a considerable influence, though it's not the major one. But on a lightwight plane with a bigger wing you'll gain more speed as you go higher than with a heavy one with small wings, since the increase in drag is smaller.

Eventually, looking at your il2-compare data of the Gladiator and the Fokker D.XXI - these two look quite reasonable in relation to each other.

The Fiat, being powered by an engine of similar power yet possible quite different characteristics, looks different. It is a bit more streamlined than the Gloster, so it might be a bit faster at the same power. The Fiat engine is quoted to reach 820hp at altitude, so maybe it was poor down low, which would explain the large increase in relation to the Gloster, and also the higher speed at altitude. But that's speculation, someone else may want to fill in here.

TinyTim
05-20-2010, 07:07 AM
Originally posted by DKoor:
Sad truth is... that D21 isn't really considerably faster than contemporary Soviet bombers,

It's even slower than a He-111 at certain altitudes, and has trouble catching up with Stukas, being only 15 or so kph faster. Watch not to take the Sarja4 - this one is even slowerr than Stuka due to different engine!

It's slow for sure, but indeed beautifully built plane, TD did a great job with it.

FatCat_99
05-20-2010, 07:17 AM
Originally posted by TinyTim:
I gave this bird a couple of rides last days. Beautifully built 3D model, fascinating cockpit, very nicely done damage modelling, unique features (random gunsight, tracer option). Bravo and big thanks to TD!
Thanks.



I don't know any reliable sources about real D.XXI testing. Finns tested them and results have been published in various books.
Here is our target performance for S3 Early

<pre class="ip-ubbcode-code-pre">
Level Speed
342 Kmh TAS SL
370 2000m
418 5000m
=============================
Cruise speed 330Kmh at 2000m
==============================
Climb
3min 27sec to 3000m 14.5m/s avg
6min 23sec to 5000m 13.1m/s avg (11,36m/s from 3000-5000m)
</pre>

FC

TinyTim
05-20-2010, 08:37 AM
Thanks a lot FatCat, I was hoping for someone from TD would stumble across this. http://forums.ubi.com/images/smilies/25.gif

So I think this excludes the sim from the discussion - the numbers from the sim appear to be very accurate, hats off again to TD!

About the real D.XXI - I would however expect it to be a lot faster than a Gladiator, which, powered by the same engine and having nearly the same weight, managed a very similar top speed of about 415kph, despite being a biplane and thus a lot more draggy.

Any ideas as to why the D.XXI wasn't faster, or as to why my reasoning is wrong?

JG53Frankyboy
05-20-2010, 08:37 AM
the plane is indeed very , very nice modelled - congratulations.

anyway, we died in hundreds in a Winterwar campaign in the online war VOW against soviet Polikarpows and Tupolews - every mission was Suicide/Kamikaze, but we laughed a lot in Teamspeak http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif
not without reason the finnish pilots were ordered to avoid combat with enemy fighters and concentrate on intercepting bombers. the plane that should fight the enemy fighters was the Gloster http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

EJGrOst_Caspar
05-20-2010, 08:59 AM
Italian planes are well known for their good aerodynamics. This is a weak statement without any numbers, I know, but you know, a good shaped fuselage can bring right a few km/h.

JtD
05-20-2010, 09:04 AM
Judging from sea level top speed the Gloster has an about 15% higher cdo. Might be even more, it's just a quick guess.

Romanator21
05-20-2010, 09:37 AM
How do the Dutch and Danish Fokkers compare?

TinyTim
05-20-2010, 10:35 AM
Originally posted by Romanator21:
How do the Dutch and Danish Fokkers compare?

Danish is slower than Gladiator, nearly exactly as fast as Stuka (at Fokker's optimal altitude of 5000m). Dutch is faster, but still slower than S3 early.

The S3_early discussed above is the best Fokker performer.


As I digged deeper into this, I found out that the 460kph figure (often cited online) comes either from initial specification requirements either from prototype testing, which did manage to reach 460kph, but with no radio, weapons and ammo, and only after aerodynamic refinements (initial "clean" prototype managed only 445kph). Properly equipped it achieved about 415kph - in Finnish and in Dutch tests, which corresponds wonderfully with the sim.

I've found some claims that Fokker did everything he could to get the Dutch operational planes to 460kph at 5000m as required - and did some aerodynamic refinements, but according to some claims it still managed only about 435kph with full military gear. The IL-2 one (Dutch version) manages about 410khp at 5000m. Bottom line - 460kph is a pure fantasy number! 415 is what most geared up operational Fokkers with Mercury VIII managed.

The more I'm reading about this, the more it's becoming evident that Team Daidalos did it very accurately. Numbers appear to match the test figures to a couple kph at largest!

M_Gunz
05-20-2010, 12:50 PM
You know the engines but don't say about the props which can make a big difference.
Fokker D.XXI I see some had Ratier propeller and the Finnish had a Hamilton Standard, I assume CSP.
Nothing I can find says more than the names of the propellers but for all that weight just look at
the climb! Perhaps optimized for climb, not speed?


what annoyes me most is that this game seems to have proplems with fixed propellers , planes with them have a realy bad acceleration and loose fast enginerevolutions in any manouver

Fixed propellers are lousy compromises compared to even 2-speed props. Only part of the blade is optimal at
any one speed, the length of the blade covering the entire speed range of the plane and of course it needs
enough power for takeoff which limits the top speed -- IAS not TAS.

TinyTim
05-20-2010, 03:37 PM
M_Gunz, good point. In the sim the only Fokker with adjustable pitch is the Sarja_4, but it appears to be the worst performer of them all. Probably due to different engine.

On the other hand - Gladiator MkI (J8A) also has a fixed pitch prop.

M_Gunz
05-20-2010, 04:02 PM
The only Fokker D.XXI's I saw while surfing that might have used fixed prop were trainers listed as having
wooden props.

The Finnish D.XXI's with top TAS 418kph had Hamiltons, why bother with all that weight and mechanism if they
could get the same speed by bolting a wooden fixed prop on the front?

hamilton Standard history -- CSP since the early 30's. (http://en.wikipedia.org/wiki/Hamilton_Standard)

The others had Ratier props, fully adjustable pre-WWII. The D.520 used a Ratier prop.

Is the Il2 model a fixed prop or is it that you can't adjust it manually? If Ratier, maybe should only be manual....
The speed is right for CSP/VSP, a game error would be in reporting/treating it as fixed prop IMO.

TinyTim
05-21-2010, 08:59 AM
Correction, not only Sarja4, but also the Dutch version has a variable pitch propeller. This version however has the Mercury VIII engine (as opposed to the Wasp equipped S4).

Weird thing is, it performs worse than a fixed pitch Sarja 3 with the same engine.

JtD
05-21-2010, 09:03 AM
Both in climb and speed? Tested in game or just il2-compare data?

What's the weight difference? Any other differences between the variants?

Kettenhunde
05-21-2010, 11:28 AM
Weird thing is, it performs worse than a fixed pitch Sarja 3 with the same engine.


Something is wrong with that. A fixed pitch propeller will never outperform a CSP of the same blade design.

One thing to check is the number of blades. In General, a three bladed propeller will out climb a two bladed propeller of the same design. The two blades will have a faster Vmax and cruise performance.


why was a monoplane D.XXI not faster in reality, especially compared to Gladiator and Fiat biplane fighters

The explanation is not hard and since nobody has explained what is going on aerodynamically, I will help you out.

This is where you have to understand the difference between, powers, forces, and coefficients.

A biplane has some unique features over a monoplane and there are some very good reasons why they were the design of choice for so long.

You can have a wing that not very efficient with high coefficient of induced drag that just does not produce much power of induced drag. In fact what is called Aspect Ratio is the major characteristic for determining the efficiency of a wing. The higher the Aspect Ratio, the more efficient the wing.

A monoplane in general has a higher aspect ratio than a biplane.

So how is a monoplane more efficient but winds up at the same speeds??

Wingloading....those biplanes in general have more wing area and are producing less force per wing because the force on each wing is lower.

The relationship of the power of induced drag to velocity is the power of induced drag varies at an inverse relationship to the first power with velocity.

Pri <1> / Pri <2> = V2/V1

The downside in the Biplane is the additional parasitic component of drag of the additional structure. The power of parasitic drag varies at a direct relationship to the cube of velocity.

Prp <1> / Prp <2> = (V1/V2)^3

So while our biplane produces less induced power required, parasitic drag power rises rapidly with velocity.

The end result if they are going the same speed with the same power is the same amount of power required as a monoplane.

The forces required are the same.

You can see that in WTE Galloway's example:


Blackburn tested two virtually identical aircraft in 1932, same fuselage, some fixed undercarriage same engines, but one was configured as a monoplane and the other as a biplane. Test results showed that the estimated top speed of the biplane at sea level was 123 m.p.h. (198 km./h.), and that of the monoplane 124 m.p.h. (199 km./h.).


Hope that helps to lend some insight!

All the best,

Crumpp

TinyTim
05-21-2010, 05:13 PM
JtD,

I compared the Dutch version and Finnish Sarja 3 early version. Dutch one has adjustable pitch prop, Finnish has fixed pitch, both props are 3 bladed.

I tested them for max speed: Finnish Fokker outperforms the Dutch one despite fixed pitch prop. At optimal altitude (5.000m) I could get Finnish Fokker to 417kph and Dutch one to 408kph - not much of a difference. At the ground level however I only managed to get the Dutch one to 330kph, with Finnish running at 350kph - this corresponds excellently with IL-2 compare:

http://www.shrani.si/f/R/8B/3V8WxuH3/chart1.jpg

I didn't test climb values, because I don't exactly know how to do it consistently. However, according to IL2Compare on the upper graph Finnish version climbs a lot better. Also - IL2 compare states that Dutch version is lighter than Finnish one for about 100 kilos.


Crumpp,

thanks for insight. I understand, you can find or construct two otherwise similar planes, one monoplane and the other biplane with biplane being faster (if the monoplane is not built for speed). I could completely understand it if high top speed was somewhere on the bottom of the priority list, but this is intriguing exactly because atrocious speed was what plagued D.XXI from the beginning, and design team did everything they could to make it faster and get it from 410kph to 460kph which was required. They never succeeded, I don't really believe they "forgot" to take a look at the wing. What in your opinion could be optimized on the D.XXI to make it considerably faster than biplane Gladiator (keeping similar features intact - fixed gear, fixed pitch prop, similar TOW, same engine) and why didn't Fokker think of that?

Such an example that crosses my mind would be I-153 and I-16 type 18 - both have M-62 with 800hp, retractable gear, two bladed CSP, similar TOW, yet I-16 is roughly 60kph faster than I-153 at all altitudes.

JtD
05-21-2010, 05:25 PM
Hi TT, the il2-compare climb performance for the Finnish Fokker is wrong. It actually climbs worse than the Dutch version. It would look like it does if you weren't considering low prop efficiency due to fixed pitch. In game the S3 climbs a little bit slower than the Dutch version.

M_Gunz
05-21-2010, 06:55 PM
Originally posted by TinyTim:
JtD,

I compared the Dutch version and Finnish Sarja 3 early version. Dutch one has adjustable pitch prop, Finnish has fixed pitch, both props are 3 bladed.

How you know this?

I see on some places wooden prop is taken to mean fixed pitch which is not necessarily true!

Kettenhunde
05-21-2010, 07:15 PM
What in your opinion could be optimized on the D.XXI to make it considerably faster than biplane Gladiator (keeping similar features intact - fixed gear, fixed pitch prop, similar TOW, same engine) and why didn't Fokker think of that?


It is hard to say with any real certainty. I don't know that much about the Dutch Design teams of that time period.

What I do know.

The Fokker was designed in a transitional time period. There was a revolution in aerodynamics in the mid 1930's and our knowledge increased 10 fold. In the 5 years after the design of the Fokker D XXI we came to have a much better understanding of high speed aerodynamics as well as stability and control. Compressibility for example was hardly recognized in 1935 but by 1942 theory began to exploded on it.

The term "critical speed" came about from a 1926 investigation using oil plots. It was not known what caused it but the reason for the loss of lift and increase in drag at high speed was identified as flow separation.

In fact it was not until 1934 that MIT Graduate John Stack took the worlds first schlieren pictures of normal shock formation. That set the wheels in motion as we finally began to understand the physical changes and mechanism of compressibility. Relating that however to aircraft behaviors did not occur for almost a decade.

I suspect that the issue in the Fokker DXXI was one of unrealized flow separation causing excessive drag at higher velocity. This is quite common in the time period and even in the familiar later designs of WWII. The Spitfire's windshield slope and radiator intake, the P51 radiator intake, and the FW-190D9's windshield slope are some common examples.

Today we slope and size intakes and surfaces based on normal shock formation.

That is just a guess, however.

You have to realize too that Fokker was out on a limb in 1934 even designing a monoplane with an enclosed cockpit. The Leadership in most air forces and many pilots were of the opinion that a open cockpit was essential to safe flight. There was also a popular line of thought among military theorist that the speeds a monoplane fighter could attain would preclude it from effectively dog fighting. The human pilot just would not be able to withstand the acceleration forces.

mortoma
05-21-2010, 09:15 PM
Speaking of the random gun sights, sometimes you get one with no wheel boots too. Or wheel pants, whatever you call them. How about wheel fairings? It seems to be rare, as I only flew one with bare wheels once.

JuHa-
05-22-2010, 02:54 AM
Originally posted by Kettenhunde:
unrealized flow separation causing excessive drag at higher velocity. ... the P51 radiator intake... some common examples.


The early P51 radiator intake did suffer from this, but during the tests the "rumble from below" was investigated and intake modified. End result (for production models) was a pretty efficient cooling intake. Or so Mr. D. Lednicer says in his article "World War II Fighter Aerodynamics" (EAA 135815). I'm willing to bet that this article is familiar to you?

If I remember correctly, the Me109F series also modified the cooling system to take advantage of the better understood flow separation.

Kettenhunde
05-22-2010, 06:59 AM
The early P51 radiator intake did suffer from this,

That is correct Juha.

Almost all of the aerodynamic problems by the time WWII came around get solved in most designs.

We just knew so much more about the mechanics of high speed flight by then compared to what we did in 1934.

It is highly unusual for one to go unresolved no matter what airplane we are discussing.

Bremspropeller
05-22-2010, 09:17 AM
The Fokker was designed to be a "no frills" aircraft for Dutch East India - not for european air-superiorrity.

Nonetheless, it did astonishingly well in Europe.

tmp190
05-22-2010, 10:00 AM
Originally posted by TinyTim:
1. Everything is modelled as close to historical values as possible.
Thich leaves us with a valid question - why was a monoplane D.XXI not faster in reality, especially compared to Gladiator and Fiat biplane fighters, which both had fixed gear (like the XXI) and similarly powered engine (850hp)?

2. Gladiator and Cr.42 are overmodelled in terms of performance.

3. D.XXI is too slow.


I think Fokker speed are pretty close to what was measured in Finnish Air Force.
Gladiator seem to be some 20 km/h too optimistic.
No data of the other planes

tmp190
05-22-2010, 10:12 AM
In the "compare" -program I assume that:
100% = Maximum continuous power" ?
Max= "War emergency power" ?

JtD
05-22-2010, 10:33 AM
No, 100% means an in game power setting of 100% and 110% means the maximum available power, including WEP active.

How 100% translates into real life figures depends on what the programmer made of it. It isn't always the same for each and every plane.

M_Gunz
05-22-2010, 10:38 AM
Originally posted by Bremspropeller:
The Fokker was designed to be a "no frills" aircraft for Dutch East India - not for european air-superiorrity.

Nonetheless, it did astonishingly well in Europe.

The Polish did astonishingly well for the short time they lasted in air.
That's because it wasn't the planes, it was the pilots that mattered.

I'm not aware of any planes that automatically made whoever flew them great, but always seeing it was this plane
or that one that "did" <adjective-here> or "got kills". Maybe that's why so many players think they can pick a
plane and expect results due to that plane?

tmp190
05-22-2010, 10:42 AM
Originally posted by JtD:
No, 100% means an in game power setting of 100% and 110% means the maximum available power, including WEP active.

How 100% translates into real life figures depends on what the programmer made of it. It isn't always the same for each and every plane.

In compare program there is no "110%" only "MAX". Is it the same thing?
110%=MAX=WEP in compare?
100%=Depends (Normal/Maximum continuos/Military) ?
If so any comparison with RL data is hard, IMO.

Bremspropeller
05-22-2010, 11:04 AM
I'm not aware of any planes that automatically made whoever flew them great

P-51 http://forums.ubi.com/images/smilies/winky.gif

JtD
05-22-2010, 11:10 AM
Originally posted by tmp190:

In compare program there is no "110%" only "MAX". Is it the same thing?
110%=MAX=WEP in compare?
100%=Depends (Normal/Maximum continuos/Military) ?
If so any comparison with RL data is hard, IMO.

Yes, in all points. Best comparison can be made with in game 110% vs. real life WEP/Notleistung/Forzash/MAX/whatever.

Kettenhunde
05-22-2010, 11:24 AM
If so any comparison with RL data is hard, IMO.


That is true.

It is the thrust independent performance points that give the aircraft its dog fighting characteristics.

Kettenhunde
05-22-2010, 11:28 AM
What are the major design changes between the Fokker DU and Fokker S3.

That is a tremendous shift in the L/D curve. That is just not correct without some serious redesign.

A new airfoil, wing design, and major changes to the fuselage perhaps?

We re-engine aircraft on occasion. When going from a 150 hp O-320 fixed pitch to a 200hp CSP does not represent an L/D curve shift. It represents a thrust increase. The L/D curve remains fixed and the thrust dependent points shift to the new thrust available.

When you add thrust to an existing design without major changes, only the thrust defined performance points change.

tmp190
05-22-2010, 11:30 AM
Originally posted by JtD:
Yes, in all points. Best comparison can be made with in game 110% vs. real life WEP/Notleistung/Forzash/MAX/whatever.

Thanks. The specific number for the Finnish Fokker D. XXI:
350 km/h OTD, 415 km/h at 5000m.

Gladiator:
330 km/h OTD, 400km/h at full throttle height. Typical used plane was 20-30 km/h slower.

I believe both planes were with fixed pitch propellers.

JtD
05-22-2010, 12:02 PM
Thanks for providing numbers - but where are they from? Finnish testing?

Kettenhunde
05-22-2010, 01:26 PM
What are the major design changes between the Fokker DU and Fokker S3?

Edited as I did not put the question mark..

M_Gunz
05-22-2010, 06:28 PM
Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I'm not aware of any planes that automatically made whoever flew them great

P-51 http://forums.ubi.com/images/smilies/winky.gif </div></BLOCKQUOTE>

For killing Tiger Tanks, right?

tmp190
05-23-2010, 06:53 AM
Originally posted by JtD:
Thanks for providing numbers - but where are they from? Finnish testing?

That is correct.

TinyTim
05-23-2010, 11:09 AM
Originally posted by Kettenhunde:
What are the major design changes between the Fokker DU and Fokker S3?


I don't think there are/were many apart from the propeller. Dutch version has all 4 machineguns in the wings outside of prop arc, while Finnish one has two in the wings and two synchronized in the fuselage shooting forward between cilinders. Other changes are probably minor enough not to change the aerodynamics or weight by much (if at all) - different gunsight, slightly different rear canopy design. This is all nicely modelled in the sim.

BTW, I tested the climb of both ingame versions (S3 early and Dutch) - I kept the TAS as constant as I could (190kph), and I got virtually identical climbing speed for the fixed pitch Finnish and adjustable pitch Dutch version.

Kettenhunde
05-23-2010, 12:24 PM
and I got virtually identical climbing speed for the fixed pitch Finnish and adjustable pitch Dutch version.


Ok, that sounds right. The L/D curves are going to be correctly fixed if you are getting the same climb speed. The rate should improve with additional power at the same speed.