Rollrates

[Pyro]

The top row of the chart looks like it says 180 but if you check the scale, you'll see that it's really 160.  

Also, not all NACA or other evaluation reports corraborate each others data.  So it's not possible to be in agreement with all the good data out there.

Different models can yield different results due to changes such as on the F6F with and without the spring tab ailerons so you have to make sure you're dealing with an apples to apples comparison.  Sometimes you have two very differing sets of data for two variants that should be very similar if not identical because of a lack of any changes that would have an effect there.  That certainly murks the waters a lot.

Roll rate also varies with the direction of your roll.  Some charts plot both left and right hand roll rates while some leave it ambiguous.  

The Typhoon sure jumps out at me because it was known for being a poor roller and I can't recall of the top of my head where I got the information I used on it.  I'm actually surprised that it rolls that well in AH.  I'll have to take a look at that when I get a chance.



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Doug "Pyro" Balmos
HiTech Creations

[Jimdandy]

Looking at Jekyll's data a little closer I'm thinking the NACA data was taken in the direction of torque. The average of both (for example the 190) is flatter. Maybe if Jekyll preformed the test again this time only in the direction of torque it my be closer. As Pyro and Jekyll stated we don't know all the particulars of each plane and exactly how the data was collected. But AH is very close considering those things.

I forgot to add this. To F4UDOA's question on the ability of the F4U to roll I would guess that it was the gull wing. A good example of this is the F-104. The wings on the F-104 were angled down to decrease stability and increase roll response. The F4 Phantom had a similar wing arrangement. Think of the wings as being a peace of Hotwheels car track and the center of gravity of the plane as a car on the track. Bend the track down at both ends and try to balance the car at the top of the arc. Then bend the track up a try to balance the car in the trough at the bottom. Obviously balancing the car at the top of an arc is harder than letting it set in the trough. The angle of the wings to the hull places the force vector in such a way as to stabilize the plane with lift or destabilize it. I hope this makes since and if your already way past me on this forgive the simplicity.  
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[Luke Skywalker]

I dont remember where I read that anhedral angled wings improve rollrat and dihedral angled wings worsens it.

F4U has both anhedral and dihedral wing parts, so I dont know why does that mean that the plane rolls that good. (I'm not saying that it rolls too good, I only say that I dont understand the inverted gull wing as an explanation)

 

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Hey, dont shoot me! I'm on the light side!!
   

   


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[Jimdandy]

Actually I'm just guessing. Maybe in some way gull wing helped. Other wise I see no explanation other than the roll in the direction of torque was real good. If I remember right the F4U had one of the largest props on any fighter (Thus the gull wing btw. They had no idea that the gull wing would give it the benefits it turned out to do. They just needed ground clearance for the prop.) With a large prop and high torque engine the roll in the direction of torque might be the answer. Or as someone said the wings may have been very ridged. I also remember something about the F4U having some very advanced control surfaces. I can't remember the features. If anyone knows please tell me. Tell me I'm wrong if I am. I've been there before  

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

[F4UDOA]

Gents,

I am surprised that there isn't more info on the rolling ability of the F4U. It was supposed to be very good compared to other American mounts. As for the gull wings helping it roll I am just guessing like everyone else.

However I am always doing research. My latest venture is with the Vought company itself. I have contacted someone in Dallas at the old Vought plant who has access to there micro-phish(SP). He has promised to look through some of the old files for me. Specifically anything involving the rolling performance.

As a side note he did mention if I was in Dallas that I would be welcome to help him poke around. So if HT, Pyro or anyone else in the area is interested let me know and I will try to hook it up.

The truth is out there.

Later
F4UDOA

[Pyro]

The Corsair rolls so well because it has a well designed aileron system that uses balance tabs to reduce stick force.  If you look at the ailerons of the F4U, you'll see the trim tab in the center of the left aileron but you'll also see another tab on both ailerons at the most inboard position.  Those are the balance tabs.  They work on the same principle as trim tabs but they automatically move opposite to the direction that the ailerons are moving.  This imparts a force on the aileron to help it move or hold in that direction.  The downside to this system is that it can get overbalanced at high speed.  Because of this F4U was placarded against using full aileron deflection above 300 knots.



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Doug "Pyro" Balmos
HiTech Creations

[Jekyll]

OK, added data for the Mitsubishi Zero and P47.  Also added data for the AH N1K2-J for comparison purposes.

Corrected the error regarding Fw190 roll rate at 250mph.

Anyone out there have roll data for the Hog or other AH planes across this speed range?

 

Summary so far?

The F6F-5 averages 14 deg/sec too fast
The Fw190 averages 6 deg/sec too slow (1)
The Typhoon averages 37 degrees too fast
The Spitfire averages 11 degrees too fast (2)
The Mustang averages 7 degrees too fast
The Zero averages 19 degrees too fast
The P47 averages 15 degrees too fast

(1)The Fw190 averages 16 deg/sec too slow below 300mph, and 9 deg/sec too fast over 300mph
(2) The Spitfire averages 11 deg/sec too slow below 225mph, and 15 deg/sec too fast above 225mph



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=357th Pony Express=
Aces High Training Corps

[Jimdandy]

Thx Pyro thats what I was trying to remember.

 

Originally posted by Pyro:
The Corsair rolls so well because it has a well designed aileron system that uses balance tabs to reduce stick force.  If you look at the ailerons of the F4U, you'll see the trim tab in the center of the left aileron but you'll also see another tab on both ailerons at the most inboard position.  Those are the balance tabs.  They work on the same principle as trim tabs but they automatically move opposite to the direction that the ailerons are moving.  This imparts a force on the aileron to help it move or hold in that direction.  The downside to this system is that it can get overbalanced at high speed.  Because of this F4U was placarded against using full aileron deflection above 300 knots.

[RAM]

Great info, Pyro. I also wondered why did the Corsair had historically such a good rollrate. Now I know  

The tiffie's rollrate doesnt surprise me. I already thought it was a bit too fast,  not as much as it seems it is,but indeed faster than what I expected.

What strikes me is the Zeke. I knew that at high speeds it was hard to roll...but didnt had a clue on it having such bad low speed roll performance.

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[Jimdandy]

Sounds like fun! Good hunting.

 

Originally posted by F4UDOA:
Gents,

I am surprised that there isn't more info on the rolling ability of the F4U. It was supposed to be very good compared to other American mounts. As for the gull wings helping it roll I am just guessing like everyone else.

However I am always doing research. My latest venture is with the Vought company itself. I have contacted someone in Dallas at the old Vought plant who has access to there micro-phish(SP). He has promised to look through some of the old files for me. Specifically anything involving the rolling performance.

As a side note he did mention if I was in Dallas that I would be welcome to help him poke around. So if HT, Pyro or anyone else in the area is interested let me know and I will try to hook it up.

The truth is out there.

Later
F4UDOA

[Jekyll]

 

Because of this F4U was placarded against using full aileron deflection above 300 knots.

Something else for 1.06 Pyro?  

Maybe 1.07

BTW  

230MPH
-------------Roll left---------Roll Right
P-47D-40-----5.9sec61dps-------4.9sec 74dps
F4U-1D-------4.9sec73dps-------4.5sec 81dps
F6F-5--------5.9sec61dps-------4.6sec 78dps
P-51D--------5.1sec71dps-------4.8sec 75dps

AH F4U1-D results

230 mph, 10,000 feet.

Roll left 3.72 sec, 96.77 deg/sec
Roll Right 3.91 sec, 92.07 deg/sec

Interesting that the AH Hog rolls left faster than it rolls to the right, completely at odds with above test results.

Would not engine torque provide an advantage when rolling to the right?

AH's missing torque strikes again?

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

[niklas]

Pyro do you mean the F4U had a Flettner Rudder??

If so why has the G10 the same aileron characteristic like the other 109? It was also equipped with a Flettner Rudder.

Flettner Rudder was just one possibility to decrease stickforces. Frise type ailerons had the same effect, but worked different.

I´m wondering myself at the moment why the 190 reaches 50lb stickforce already at 250mph. All sources i read so far about the 190 said it had very light aileron controls up to high speeds. Sure, they became harder at very high speeds, but 50lb at 250mph??? Strange.

niklas

[wells]

The f4u didn't get spring tabs on the elevator or rudder until the F4u-5.

[Pyro]

That's interesting Jekyll but not for the reason you think.  The F4U in that case is the only one showing a stronger roll in the direction of torque which if you threw out everything else would indicate stronger torque, not weaker.  I'll have to try it out and see what's going on.  It's most likely something in the way that trim is modeled.

Niklas, I was just pointing out the Corsair had mechanically assisted ailerons.  There's other factors that affect the rollrate but that one seemed obvious and overlooked.



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Doug "Pyro" Balmos
HiTech Creations

[Zigrat]

hi

it seems that with the exception of the fw-190 almost all aircraft roll too quickly?

especially looking at the high speed comparison of 190 v spitfire for esxampe, the real naca difference between 190 and spit is double the aces high difference


the 109 is not listed on this chart, but i have long believed the 109 rolls too well at 400 mph, if it was included on this chart i think it would also be rolling too quickly compared to naca findings