Hurricane Roll Rate

[Kwiatek]

Originally Posted by Kurfürst

The roll chart you posted - from http://mitglied.multimania.de/luftwa...f/rollrate.pdf - above is for the Mark VA W3119 tested by NACA and the report says metal covered ailerons.

See page 2 and 13: http://mitglied.multimania.de/luftwa...pit_flying.pdf

Sry but i dont see any conection with these both raports.

First raport is about Spitifire, Hurrciane, P36 and P40 - with not detail about types and no detail about type of airleons - if it was fabric or metal ones.

Second raport is clearly about Spitfire MVA with metal ailerons - but as i said i dont see conection between both raports.

Very poor roll rates of Spitfire from first raport suggest that it was with fabric covered ailerons. These confirm second roll rate chart which i posted with Spitfire MK V with metal airleons where roll rate is clearly improved over fabric covered ( from first test).

I got also another roll rate chart where roll rate of Spitfire MK V with metal airleons is about 100 deg/sec.

[Kurfürst]

Originally Posted by Kwiatek

Sry but i dont see any conection with these both raports.

Hmm, both reports are made by NACA, both reports are authored by William H. Philips. The first (Spitfire MkV metal ailerons) report dates January 1942. On page 13 it says that at 6000 ft altitude, 30 lbs stickforce, 59 degrees/sec was obtained.

The second (P-40 Hurri, Spit P-36) dates November 1942. Again made by NACA, both authored by the same William H. Philips.The roll chart of P-36, Hurricane, P-40, Spitfire shows ca. 65 deg/sec at 10000 ft altitude (as opposed to 6000 ft in the first report), 30 lbs stickforce. The report also references to NACA 868, the well known lateral control characteristics summary report, which notes that roll rate increases with altitude, and gives the neccessary conversion methods.

Quite simply the second report uses the figures obtained on the Spitfire Mark V with metal ailerons, tested by NACA earlier, and converted it to 10 000 feet.



First raport is about Spitifire, Hurrciane, P36 and P40 - with not detail about types and no detail about type of airleons - if it was fabric or metal ones.

Second raport is clearly about Spitfire MVA with metal ailerons - but as i said i dont see conection between both raports.

Very poor roll rates of Spitfire from first raport suggest that it was with fabric covered ailerons.

Its an assumption, but no, both reports show the same Spitfire with metal ailerons. In fact both reports show the same roll rates obtained.

These confirm second roll rate chart which i posted with Spitfire MK V with metal airleons where roll rate is clearly improved over fabric covered ( from first test).

Indeed the roll chart you posted for another Spitfire Mark V tested in the UK shows far higher roll rate than any other test result or source, UK or US. Its a pity we do not know anything about this Spitfire, but it seems this aircraft was either extraordinary good in this regard, or it had some non-standard aileron setup. We can only guess.

[Viper2000]

Originally Posted by Kurfürst

Indeed the roll chart you posted for another Spitfire Mark V tested in the UK shows far higher roll rate than any other test result or source, UK or US. Its a pity we do not know anything about this Spitfire, but it seems this aircraft was either extraordinary good in this regard, or it had some non-standard aileron setup. We can only guess.

Read the chart. The pilot used 50 lbf rather than 30 lbf. It is therefore hardly surprising that a higher roll rate was achieved because constant helix angle could be maintained to a higher TAS. Agreement between the charts is actually extremely good if you take this into account.

I already pointed this out in my last post, had you but taken the time to read it...

BTW:

• Roll rate is just a function of helix angle and TAS.
• Helix angle is a function of wing design and control deflection.
• Stick force to a first order approximation is proportional to Q.
• Deflection limited roll rate is therefore just proportional to TAS
• Force limited roll rate is inversely proportional to Q
• Roll rate achievable at altitude will vary in proportion to (TAS/EAS)

However, altitude itself doesn't "cause" this; the aeroplane knows nothing about its position relative to the geoid or to MSL. The relationship is simply caused by air density variation, and therefore it's quite possible for roll rate to be affected by the weather.

On a related note, the reduced helix angle associated with any given absolute roll rate as TAS increases is responsible for the reduction in roll damping at high altitude; again, the underlying mechanism is the TAS/EAS relationship, which means that roll damping is also a function of the weather conditions.

NB, the simplistic relationships explained above deliberately ignore the effects of compressibility upon stability & control. In particular, shockwave formation can dramatically reduce the effectiveness of control deflections by reducing the ability of control deflections to influence the flowfield upstream of the shock; stick forces are not reduced in proportion to the reduction in control effectiveness, and therefore pilot reports tend to read as though the controls have suddenly become heavier, when in fact they've just become less effective. But I digress...

[b101uk]

Viper2000

Its worth remembering the >30lb < 50lb used are designed to replicate the strength of the average right arm trying to pull the stick to the right in a right hand roll, in a left hand roll with the same right arm you can literally double the force applied to the stick in a left hand roll so in the region of 60lb to 100lb or if you use both hands you are realistically looking at up to 150lb both ways and that’s without the affect of adrenalin wile being shot at and Its certainly not undocumented pilots pulling high speed direction and orientation changes etc using both hands.

[Viper2000]

Originally Posted by b101uk

Viper2000

Its worth remembering the >30lb < 50lb used are designed to replicate the strength of the average right arm trying to pull the stick to the right in a right hand roll, in a left hand roll with the same right arm you can literally double the force applied to the stick in a left hand roll so in the region of 60lb to 100lb or if you use both hands you are realistically looking at up to 150lb both ways and that’s without the affect of adrenalin wile being shot at and Its certainly not undocumented pilots pulling high speed direction and orientation changes etc using both hands.

I'm just saying that the 2 charts are in agreement with each other when the different stick forces upon which they are based is taken into account.

I'm not suggesting that either figure is representative of the limit of pilot capability. Indeed, as I have already stated in this thread, you can't measure the limits of capability, and you certainly couldn't do so in a repeatable fashion across a variety of types because you'd see different forces for each as a function of cockpit design etc..

[TheGrunch]

Originally Posted by b101uk

Its worth remembering the >30lb < 50lb used are designed to replicate the strength of the average right arm trying to pull the stick to the right in a right hand roll, in a left hand roll with the same right arm you can literally double the force applied to the stick in a left hand roll so in the region of 60lb to 100lb or if you use both hands you are realistically looking at up to 150lb both ways and that’s without the affect of adrenalin wile being shot at and Its certainly not undocumented pilots pulling high speed direction and orientation changes etc using both hands.

Regardless of this 50 lbs is the maximum we can pull in CoD in every direction, I'm afraid.

[madrebel]

how come nobody is complaining about the unbalanced pitch control of the spitfire? you know, the control being so light that it is possible to exceed CLmax in all conditions of flight if you aren't careful.

instead we're worrying about how much force a pilot hopped up on adrenaline can apply to the heavy aileron but not mentioning how easily that pilot could rip his own wings off if not careful.

[TheGrunch]

As far as I know that's right...the Spitfire is very well known for having a ludicrously light elevator especially by comparison with its heavy ailerons.

[Kurfürst]

Originally Posted by Viper2000

I already pointed this out in my last post, had you but taken the time to read it...

I don't quite see why are you addressing this to me, as I was commenting on the origin of your 'Spitfire' - which we now know to be a Spit VA with metal ailerons, not a canvas covered one. You're storming a castle with open gates..

[Viper2000]

Because I don't think that the fast rolling Spitfire is actually any faster than the other; I think they're basically the same and differ only in the stick forces applied. Therefore I don't think that there's anything particularly "exceptional" about the results.

If you look at the curves in the deflection limited region, you'll see that the roll rates are basically the same, so the difference is simply caused by the different stick forces applied in the tests.