DVL data on Bf 109 roll rates

[gripen]

Raunio's article on Bf 109 controll forces is out now so here is DVL data on Bf 109 roll rates. I dug this out from the Deutsches Museum years ago and all those people who have got the report from me  can do what ever they want with it from now on. It's free

The values in the chart are in rad/s and TAS (can be checked from the mach number if one wants to argue). Altitude is 3000 m.

gripen


 

[Neil Stirling1]

Thanks Gripen

Neil.

[Kurfürst]

68 degrees/sec at 650 kph. I guess another myth died today.

Though it should be noted the tests were done on Bf 109F-2, so wing torsion effects should be stronger (ie. decreasing roll rate more at altitude) than with the 109G/K wings, which had reinforced main spar, ribs and skin.

Nice work making it public, Gripen.

[OttoJ]

BOO! BOO! ....... oh wait, that's Milo's line.

[Karnak]

What are the stick forces at those speeds?  My German is not nearly good enough to read German charts reliably or confidently.

[Angus]

MeBwerte = measuted values
Umgerechnete werte = calculated value like extrapolated.
Anyway how do you read that thing. Well maybe I'd better zoom a bit more for a better reading.
And what 109????? 109F-2?

[Krusty]

Okay, from the perspective of somebody who doesn't do heavy research into that stuff.... My question is: "So what does that tell us? Does our AH model roll too fast? Just right? Too slow?"

[Karnak]

Krusty,

It depends on the stick forces required fpr those roll rates.  They are higher than in AH, but AH limits stick forces to 50 or 60lbs as I recall, so if those are 90lb stick forces they don't mean anything to AH wheras if they ar 30lb stick forces they mean a lot.

[Krusty]

Okay, I gotcha on the stick forces. HT has mentioned that in the past. Okay, then, just from the rate of roll we have in AH now, regardless of stick force I take it the graph is saying the 109s rolled better? (just from a strict reading of the graph)

[Karnak]

Yes, much better.

[Bruno]

Raunio's article on Bf 109 controll forces is out

Where can I find the article?

[Kurfürst]

What are the roll rates in AH?

You should read the first graph BTW, the thick line (ymax=15) shows the roll rate at 15degrees stick deflection in radians.

The other line Em=15 shows the roll rate at 15 degrees middle value aileron deflection. The Bf 109`s ailerons deflected assymetrically, upwards 22 deg 40', dowards 11 deg 20', middle value being about 16. Appearantly this line shows the max possible deflection, so going by the max aileron deflection values (until limited by stickforce), we get :

Max roll rate of Bf 109F-2, at 30kg/66lbs stickforce :

200 kph = 45 deg/sec (0.8rad)
300 kph = 68 deg/sec (1.2rad)
400 kph = 83 deg/sec (1.45rad)
480 kph = 20kg/44lbs limit
500 kph = 88 deg/sec (1.55rad)
600 kph = 91 deg/sec (1.6rad) - peak value
700 kph = 56 deg/sec (0.98rad)
800 kph = 23 deg/sec (0.4rad)

Considering the aircraft reaches it`s peak roll rate at rather high speed, the stories about the set in cement, ineffective ailerons are really reaching.

To conver radians to degree:
Take the radian reading, divide it by 6.28 (ie. 2phi), then multiply with 360 to get the degree/sec value.



This pretty well agrees with both anecdotal evidence and other measured data :

"Roll performance is similar to a Hurricane or elliptical wing tipped Spitfire.  A full stick roll through 360 degrees at 460kph takes 4 to 4.5 seconds without using rudder, and needs a force of around 20 lbf.   One interesting characteristic is that rolls at lower speeds entered at less than 1g, such as a roll-off-the-top or half Cuban, have a markedly lower roll rate to the right than to the left.  Therefore, I always roll left in such manoeuvres."

-Dave Soutwood on flying Black 6 (Bf 109G-2/trop), 109 Lair
http://109lair.hobbyvista.com/articles/airframes/black6/bk6_flight.htm

Ie.
4-4.5 sec for 360degree roll at 460kph = 80-90 degree/sec roll rate.

And also this doc states ~4.5sec for 360 degree roll at 450 kph, ie. ~80/sec :



The NNW-SSW lines show the stickforce limiting the available roll rate in kg. 20kg = 44lbs stickforce, 30kg = 66lbs stickforce. So if AH models with 60 lbs, the 30kg line is just about compatible, 6 lbs diffo won`t change much.

So is there a roll rate chart for the Bf 109F-G for AH to compare with?

[Karnak]

I don't know the actual roll rate numbers, but the metal aileroned Spitfires easily roll better then the Bf109s.  The Hurricanes utterly dominate both the Spits and 109s in the roll.  I personally think the Hurri is overmodeled in that regard, but haven't tried to dig up the evidence of it one way or another.

[Knegel]

Hi,

as gripen wrote, the datas are in TAS and as the document show the tests are made in H=3km (H = Höhe = altitude).

In in 3km alt :

600km/h TAS = around 510km/h IAS = 91°
700km/h TAS = around 595km/h IAS = 56°
800km/h TAS = around 680km/h IAS = 23°

This values are still better than the statements of absolute stiff alerons at 400mph(643km/h) IAS, but not much better than the datas i have for the 109E!

Actually i often wrote that even the statement of stiff alerons at 400mph(643km/h) are not very important, cause 643km/h (IAS) is far above Vmax of most 109´s. At normal combatspeed of 250-550km/h IAS noone ever wrote that the 109 had bad alerons, even the RAE wrote about very good alerons at this speeds.
That in 6000m alt 643km/h IAS are already 887km/h TAS (above mach 0,7) didnt disturb anyone.

It was a nice trick to let the 109 look worse, strangewise all did 'eat' it. Its like saying: the P51 roll good at 350mph (IAS), but at 550mph(IAS) the alerons are almost stiff, so the P51 cant get used as fighter anymore. Of course thats true at this speeds, but who care, its not the common speed.

Greetings, Knegel

[Kurfürst]

Out of curiosity, how did you convert TAS to IAS, with what variables?

I am still not sure if this is IAS or TAS.
It`s pretty hard to be sure given the rought Mach/kph scale, and that it`s quite effected by tempereture, humidty and altitude...

Simply there`s too much margin for error.