Rollrates

[Sorrow[S=A]]

F4u- 190 was so superior because it's short fueselage and thick stubby wings made it extremely unstable in the rolling vector. IE think of what resists a roll: Inertia, since the 190 had no high inertia to overcome to start rolling it spun fast! Also it's short wings had almost no wing twist/torsion, it had a full metal skin as well.

Better question (and harder to explain) how does the F4U have such a great roll when it has almost none of these characteristics? (err, short of the metal skin). I am not sure how they made the F4U so unstable- it has always made me curious if the Gullwing helped.

(BTW "unstable" is a term that does not imply poorness- the more unstabe a plane is a vector the less force it needs to change it's state.)

[F4UDOA]

Sorrow,

My guess would be the aspect ratio of the F4U being very low made the wing more rigid and less prone to twist. Modern fighters all have a very low aspect wing as well although I'm not sure of the cause of the benefit. The gull design probably had something to do with it as well. It seems when looking at an F4U in flight that it is riding on the air as a duel hull racing boat would ride above the water. I have a pretty good book on aerodynamics I refer too when I have a question but eventually I just ask Wells to explain it to me.

Wells???

[Daff]

F4U, do you have a source for those stick forces?. (Not that I doubt them, I just want to get my dirty little hands on them)

Daff

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CO, 56th Fighter Group
"This is Yardstick. Follow me"

[F4UDOA]

Daff,

No prob.

In 1989 a group of military test pilots known as the the "Society of Experimental test pilots" tested the F4U-1D, F6F-5, P47D-40 and P-51D all loaded to combat weight and using modern evaluation tactics for the purpose of determining the best WW2 fighter. They published the report in the 1989 Symposium and is entitled "End of the arguement". I contacted them on there web site and they sent out me a copy (no charge). The report is a book containing test data on the Harrier, F15, B-58 Hustler and others. Very serious guy's. In the end their conclusion was it "It depends on the mission" .

But just as a tease I will leave you with their conclusion on the F4U.

   

Quote

In a turning fight the FG-1D emerged with a slight advantage over it's rivals. Light and comfortable stick forces, good performance,  adequate stall warning and docile behavior at the stall made it the "weapon of choice" among those tested

So much for those who say the F4U can't maneuver.

   

[This message has been edited by F4UDOA (edited 01-05-2001).]

[This message has been edited by F4UDOA (edited 01-05-2001).]

[F4UDOA]

Almost forgot

 http://www.netport.com/setp/

[danish]

F4UDOA;
Links dosnt seem to work.Thx anyways :=)

danish

[Jekyll]

I must say I'm surprised that no-one has yet has done any kind of comparison of AH rollrates with those in the NACA report.

So I did it instead  

 

I haven't tested all the aircraft as yet, and there are bound to be discrepancies between the NACA data and AH test results, e.g.

We don't know what model of Fw190 was tested,
We don't know what Spitfire (normal wing) was tested,
The report lists the F6F-3, while we have the F6F-5.

My testing was done in the following manner.  Load aircraft with full internal fuel and no stores.  Climb to 10,000 feet AGL.  Perform 5 rolls to left, and 5 rolls to right at the indicated airspeed.  Time each 360 degree roll with stopwatch and take average rollrate from the 10 rolls at each airspeed.

Results?  Interesting to say the least.  Based on the NACA data, each AH aircraft rolls too fast, except for the 190 (now why isn't THAT a surprise).  The 190 actually seems to be up to 40 degrees per second too slow at some airspeeds, while it appears to roll too fast at high speed.

Each other AH aircraft tested rolled too fast.  The Typhoon was as much as 40 deg/sec too fast at some airspeeds, the Spit IX some 35 deg/sec too fast at high speed and the F6F was a modest 15 deg/sec too fast at some airspeeds.

I'll be testing the P51-D and P47 varients next.  Now, if only we had NACA data on the CHog and N1K2  

Pyro, can the 190's have their 40 deg/sec back please?  

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=357th Pony Express=
Aces High Training Corps

[Glunz]

conspiracy !  

[Jekyll]

Update:  P51 tested and chart updated.  Pretty close to the NACA results, averaged only 7 deg/sec too fast across the speed range.

Testing continues  

------------------
=357th Pony Express=
Aces High Training Corps

[danish]

Appreciate it Jekyll ;=)
It may be possible to discuss details, but the overall pattern seems convincing.

danish

[Jekyll]

Yup, the testing revealed some obvious anomolies.

You can see that the AH Spitfire IX has a faster roll rate across the entire speed range than the F6F-5.

Does ANYONE believe that?

------------------
=357th Pony Express=
Aces High Training Corps

[RAM]

those tests will silent some guys that were yelling stupid things about warprolling Fw190s...when it should be rolling 33% faster than it does now  

[Jimdandy]

YES and end to squeaking with out facts!!!!!!!! YES, YES! Real data! Now we can talk and not just hear babble and opinion posture. Like you said we don't know all of the particulars about each plane but we're much much closer. No more of this uneducated "The F4U couldn't do this or that" crap! Now we have a very good idea how some of these planes compare to the game with hard facts! Thanks for posting it. It will start a whole new round squeaking but at least it will be backed with hard facts! Sorry I'm yelling   . I just got so tiered of people hacking the game without data like this. You hear so many people blah blah blah about this plane and that plane. As I said in a different posting, I'm a mechanical engineer (I see there are a lot of engineering types on hear) and I can't just say AH has it all wrong. Come on! With out this kind of data all you have to go on is the spec listed in some books. Not that it's all bad but that tells so little about how they really flew. You can assume that the average (given that the books very a little on stats) top speed, rate of climb, etc better be close on the sim or something is wrong. I don't have any complaints about the flight model as it is on AH but I would be disappointed if they didn't incorporate these facts into the flight model in the future.

PS Don't you just love reading this old stuff. This is real old fashioned engineering. These guys used their calculus! I have a slide rule I keep to remind me that people didn't always dump the problem into a computer. It is what these people did that gives us the computer programs we relay on today. I worked for an irrigation district and did some consulting for another. I loved looking back through these old documents that went back over 100 years. I got to see how engineering changed from the 1870's to the present. I have a great respect for what the people from the pre computer age did with the tools they had. The engineers I've meant that went to school and worked pre computer and moved into the computer area have a very good understanding of numbers and what they are really telling you. They don't just take for granted that the computer said it was so. Anyway I wax poetic   Thanks again for the posting.

[This message has been edited by Jimdandy (edited 01-06-2001).]

[niklas]

thx Jekyll, great work.

The really interesting result of you test is that the trend of many aircrafts, like the AH-190 and P51, are equal.

I mean where did pyro know from that he has to model a peak for the 190 at exactly 250mph, which is the same like in the Naca report? Where did he know from that the trend of the p51-rollrate is completly different?

I really would like to bet that this report, or some individual reports where this report is based on, is not new for Pyro  

Of course there remains the question why he models the 190 worse and other fighter better... honit soît...

And concerning the F4U: 4.5 sec@250mph, just look in the naca-chart where you are with this rollrate. you also can estimate where you are at 200mph or at 350mph when you don´t exceed the stick force limit or structural limit of the wings / ailerons (deformation)

niklas

[Jigster]

I believe the roll rate for the P-51D vs P-51B is pretty much on, when the D model was introduced they added a canvas panal connecting the leading edge of the aileron and the trailing edge of the wing to correct the bleed over with the B models that was said to improve roll rate marginally through about 350 mph

Whether it improved that much, I dunno.

It would make sense that all planes might have proportionally decreased roll rates for lag reasons but, them actually being higher is rather strange.

Does say alot about the work HTC put into their data, even with suposed errors it's very close.