Roll rate

[Francis marliere]

Gentlemen,

I try to guess the roll rate of major WWII aircraft on the following scale :
0 : very bad (less than 10°/s)
1 : bad (about 20-30°/s)
2 : poor (about 50°/s)
3 : average (about 70-80°/s)
4 : good (about 100°/s)
5 : very good (about 120°/s)
6 : outstanding (about 150°/s)

At the first sight I would go for :

(0) : floatplanes and seaplanes, multi-engines bombers.

(1) : most twin engine fighters (Bf110, Mosquitto, Beaufighter), A6M2N, single engine dive and torpedo bombers, some hot twin engine light bombers (A-20G ?).

(2) : early P-38, P-39, F6F, A6M2, Hurricane I/II, Spitfire I, Boomerang.

(3) : Bf109, late war P-38, F4F-3/4, A6M3/5, Spitfire II VB, P-36

(4) : P-40, P-47, Spitfire VC

(5) : F4U, Spitfire MkIX

(6) : Fw190

What do you think about that ? Would you change some things ? How would you rate the following planes :
- US : P-35, P-43, P-51, F2A-3
- Fr : D.520, MS.406, MB.155.
- It : CR.32, CR.42, G.50, MC.200, MC.202, Re.200, Re.2001, re.2002.
- IJA : Ki.27, Ki.43, ki.44, Ki.45, Ki.61.
-IJN : A5M4, J1N, J2M.
- FAA : Fulmar, Gladiator, Skua
- NL : D.XXI, G.1A

Thanks for any help,

Francis

 

[GregP]

Francis,

Roll rates vary considerably with speed. If you take just the F4U-1 Corsair (See: http://www.wwiiaircraftperformance.org/f4u/f4u-1-02155.pdf), the rates of roll during tests (overload fighter, 273 gallons of fuel in fuselage tank, wing tanks empty, full aileron deflection) l, were as follows:

1) right roll: 70° / sec, clean, 150 mph; 84° / sec, clean, 200 mph.
2) Left roll: 70° / sec, clean, 150 mph; 76° / sec, clean, 200 mph.

So your prediction of 120° / sec for the F4U is nearly twice what the aircraft was capable of ... at 150 and 200 mph, with no fuel in the outer tanks. Fuel in the outer tanks will make it roll slower. As a rule, very few WWII fighter could exceed 90° / second. Each must be researched individually, and the rate changes consideraly with speed.

If you want to do a fun simulation, have at it. If you want a realistic simulation, you need to carefully read performance reports from WWII. The thing is, they tested what they tested, not necessarily what we want to know today. They figured, for instance in the report above, that testing the rate of roll at 150 and 200 mph was enough to characterize the aircraft. But what about 400 mph and above? Not shown in the report, and you cannot assume it gets higher because most WWII aircaft rolled slower after reaching some max roll speed that varied by a lot between aircraft types. To be complete, the report also characterized the roll rate in landing configuration at 90, 150, and 200 mph, but that is not a configuration you would use in combat.

The Me 109, for instance, was a pretty good roller at 250 mph. But at 420 mph it was pretty solid in both pitch and roll, and the stick could not even be moved more than about 1/4 deflection to either side due to aerodynamic forces and a very narrow cockpit, making application of much force to the stick a problem. The 109 was designed for combat at 180 - 280 mph and it was a bit out of its element at 350+ mph.

From: http://www.spitfireperformance.com/spit1vrs109e.html :

The Me 109E could roll 45° in 1 second at 200mph, but the same roll at 385 mph took 4 seconds.
The Spitfire Mk I could roll 45° in 1.9 seconds at 200 mph, but at 385 mph it took 3.8 seconds.
It looks like the roll rates of the Me 109E (or Bf 109E) and the Spitfire Mk I were equal at about 330 mph, with the 109 rolling better when slower and the Spitfire rolling better when faster. Neither is anywhere near your projected roll rates above.

Don't go with opinons, go with documented tests. If you can't find them, then making assumptions will render the simulation not vey realisitc, though it still could be fun.

 

[Juha]

Hello Francis
try to find NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
REPORT No. 868
SUMMARY OF LATERAL-CONTROL RESEARCH

it is somewhere in the net and will give some answers

 

[Jabberwocky]

Apart from NACA 868, there are several other sources of comparative roll performance:

The NACA also did a comparison of early Spitfire, Hurricane, P-40 and P-36 rolls rates across various speeds.

There are a few other lateral control tests of the period with comparative roll rate tests. The RAF did roll rate tests for the Tempest V, Spitfire Mk XII and Mustang X - all of these are available online, most at Mike William's Spitfireperformance.com/ww2aircraftperformance.com.

There is Joe Smith's lecture on the history of the Spitfire, which gives roll rates for the Mk V with various types of aileron hinge and different types of skinning at various speeds. He also compares Spitfire Mk I, V and XXI roll rates.

There are some German tests of Bf 109G roll rates - I think they are available on Kurfurt's 109 site.

There is an graph of RAAF tests with Spitfire, Typhoon, Mosquito, various Mustangs, P-40 (Tomahawk), Boomerang and Hamp rolls rates. There is also a RAAF test comparing P-40 roll rates with the Spitfire V and Zero, although I can't recall if these are across the speed range or just peak values.

There is a German test of 109s and 190s against various Italian types that gives some commentary on comparative roll rates. The Italian aircraft generally rolled slower than 109s.

Data on Soviet, Italian and Japanese aircraft is generally harder to come by. Most of the information we have (at least, in the English speaking world) comes from the comparative tests of the air forces of the various western powers on captured aircraft. Therefore, there can be no guarantees as to the accuracy of the tests - look at the problems the USN had with FW 190 roll rates in their comparative tests with the F6F/F4U.

 

[renrich]

With the help of "Mrs Sills Sea Sick Pills" Boone Guyton spent many hours in roll tests with the Corsair. Eventually, at combat speeds, throwing the stick hard against the full stop would roll the airplane more than 180 degrees per second. And the stick force was light. Page 85, "Whistling Death" by Boone Guyton.

 

[GregP]

I've never seen a US Navy report listing the Corsair as anywhere near 180° per second at any speed.

Then again, I haven't read them all yet either.

Can anyone supply a link to such a report?

 

[renrich]

If you read Dean's "America's Hundred Thousand" he says that there were many reports of the high roll rates exhibited by the Corsair but only scanty test data available about that roll rate. The Corsair was a continual work in progress and unlike many other WW2 AC the later models always had better performance than the early models. In Guyton's book, there were many, many test flights to improve the Corsair's roll rate. I don't doubt Guyton's statement about the one second-180 degree roll but that was probably under optimum conditions( light fuel load, no guns or ammo, no external stores, best direction to roll) and I would not expect the operational Corsairs to be able to do that well. However, there are many reports about the beautiful ailerons of the Corsair. I rolled an L39 twice at 250 knots TAS. It's published roll rate is >300 degrees/second @ 250 knots and I don't doubt it.

 

[post76]

The Corsair was eventually fitted with boost tab ailerons, as was the P-38.
This would increase the rate of roll.
I've heard the Corsair was one of the better rollers, matching Fw190.
A lot of that also depends on airspeed and stick force.

 

[renrich]

The stick force on the late Corsairs was light even at high speeds and the control force about all axis was very well modulated, according to Linnekin in "80 Knots to Mach Two."

 

[GregP]

The very late Corsairs ... F4U-5 and later, didn't make WWII and the F4U-4 didn't fully equip even one Naval squadron until 4 months before the end of the war. So, the bulk of F4U Corsairs used in WWII were F4U-1 models, with the 85° - 90° per second roll rate. Improved versions , with much hgher roll rates, showed up at or after the end of the war.

I added this simply because Francis is trying to do a simulation and might as well use the values that were true for the bulk of the war, and maybe allow faster speeds and roll rates only when the date is later than an introduction date for such an improvement for a specific type.

 

[davebender]

A Soviet evaluation gave the He-100 their highest rating for aileron effectiveness. I suspect it rolled very well but have not seen any numbers for roll rate. That data must exist somewhere.

 

[renrich]

Actually I believe the Corsair which was considered the nicest flying was the F4U4. It was just barely a WW2 fighter. However the improvements that were made on the Corsair, such as ailerons, seat height , landing gear bounce, right wing spoiler, cowl flap actuators, canopies, water injection, etc. were ongoing and not always limited to the latest model to go into production. A four second 360 degree roll was considered quite good in WW2. I believe that comparative tests of an F4U1 and a FW190A4 showed them to be equal in roll.

 

[GregP]

Could be. I haven't seen that comparion, but could be.

 

[Siegfried]

A couple of notes on your roll rate figures:

Bf 109E versus the Latter Me 109F/G/K. The entire Me 109 series had ecellent roll rates at low/medium speed which reduced at high speed due to aileron stiffening.
However from the Me 109F onwards a new wing with "Friese" ailerons was fitted to reduce the control loads and so the Me 109F/G/K must have had a higher roll rate at speed.

The Spitfire Mk 22 received a new wing structure to increase roll rate since the thin single spar Spitfire wing would twist and tend to reverse the roll under some situations of high speed.

The P-51A had a modest roll rate however from the P-51B on 'internal balancing' was fitted which used pressure from control surface deflection to pressurize a bellows to reduce loads and this aircraft developed a high roll rate. Worked well with the thick laminar profile wings which had space for such things.

P-39 and P-63 had a high roll rate, the P-63 (with laminar profile) probably the fastest US roller of the war, P-40 also had a high roll rate.

Late war Hellcats and Corsairs had geared spring tabs added to reduce control forces improve high speed roll rate (at the expense of low speed roll rate)

The FW 190D-12, a few saw service, received hydraulic boosted ailerons, it was intended to fit this to the Ta 152 as well. The Do 335 also had hydraulic boosted ailerons.

Me 262 and Arado 234 used spring tabs to reduce aileron loads. For their future jets (P.1101, P.1112, Ta 183) the Germans though they might need hydraulic boosted controls.

 

[Siegfried]

The Corsair was eventually fitted with boost tab ailerons, as was the P-38.
This would increase the rate of roll.
I've heard the Corsair was one of the better rollers, matching Fw190.
A lot of that also depends on airspeed and stick force.

P-38 received a hydraulic boost assist around 1944, the pilot providing only 18% of the load. The late war US Navy fighters received geared spring servo tabs. The latter are difficult to design as they may cause flutter and tend to cause degradation of low speed roll since the tabs reduce aileron area. The FW 190D-13 (Goetz's Yellow 10) did receive hydraulic boost so 190 and ta 152 roll rate was due for a further climb. This was found when the aircraft was being refurbished and it was realized a D9 wing had been mated incorrectly to the airframe. The He 162 may also have had hydraulic boost.

 

[Ratsel]

Some Me109G's/K's had boost tabs on the aileron/elevators/rudder which significantly reduced the pressure needed to move the ailerons/elevators/rudder at high speed.

 

[Siegfried]

Some Me109G's/K's had boost tabs on the aileron/elevators/rudder which significantly reduced the pressure needed to move the ailerons/elevators/rudder at high speed.

The balance tab on the rudder of the Me 109 came in with the tall tail , this replaced the rudder horn balance. It was tested as early as 1942 but didn't seem to make it to service till 1944. There is a test report on the Kurfurst site.

The tall rudder balance tab seemed to solve the problem of dangerous rudder over balancing in High Mach dives. I suspect it is the tall tail that lead to reports of Me 109 recovering control from dives earlier than P-51D. Horn balances aren't the best thing for high Mach speeds.

Some Me 109G6, apparently built by WNF, had spring balances on the ailerons and supposedly some Me 109K-4. Little seems to be known of these devices.

 

[Ratsel]

Differential ailerons too...

 

[Altea]

A Soviet evaluation gave the He-100 their highest rating for aileron effectiveness.

What soviet evaluation? Have you got any link or references?

 

[davebender]

Obtained from the Kurfurst Me-109 forum. The original Russian language version is also available.