Quote:
Originally Posted by TheGrunch
To show that the previous chart he posted was *not* a Spitfire with metal ailerons.
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The two charts assume different stick forces, so it's hardly surprising that they look different. Agreement between the Spitfire Va(?) in the first chart and the full-wing Spitfire Vb in the second chart is pretty good at about 150 mph where both have their ailerons pegged on the stop.
It is also worth pointing out that there is quite a big difference between test roll rate and the roll rates achieved in service because of the nature of test procedure.
In this period, stick forces were generally measured by sending the test pilot into the air with a calibrated spring (often requisitioned from the nearest butcher's shop).
In order to get sensible results, tests need to be conducted under controlled conditions. It is no good just saying "roll as fast as you can", because that will tell you more about the pilot than the aeroplane.
So tests were conducted to a procedure, and the details of that procedure could dramatically affect the results (e.g., you can almost always roll a lot faster with help from the rudder than without it).
Likewise, force measurements needed to be performed with some care. Obviously you can only conduct measurements within the useful range of your equipment. If the scale only reads to 50 lbf then you can't measure 50 lbf properly, because once you hit 50 lbf on the scale, the actual meaning is >=50 lbf.
Of course, these aeroplanes weren't designed for the convenience of test pilots, so finding enough elbow room for constant force roll tests probably wasn't trivial.
All of these factors tend to reduce the measured roll rates somewhat; as such, "conservative" figures need not be the product of any kind of misinformation or conspiracy, and in fact might well emerge even against the wishes of the test organisation.
Comparisons with modern aeroplanes at airshows doesn't really stack up. Most "WWII" aeroplanes you can see flying today are not maintained in original condition (it's unrealistic to expect operators not to embody the latest airframe and engine modifications to reduce their costs and improve safety), and they often don't have guns and ammunition in their wings when performing at airshows
. To get a real sense of this, compare and contrast the BBMF's oldest Spitfire with the Battle of Britain vintage Spitfire in the Imperial War Museum in London which AFAIK has be de-modded to genuine 1940 standard...