[NZtyphoon]

Originally Posted by MiG-3U

Ok. lets have a look to the first Spitfire Mk. II manual:

14. This aeroplane is stable, and rock-steady in flight athigh speed. The controls are not ideal, because it will be found that the aileron control become exceedingly heavy at high speed, while the elevator remains comparatively light and sensitive. Individual aeroplanes vary slightly, but in most cases care is needed in the use of the elevator control at high speed, to avoid sudden increases of load factor, or "g". During a tight turn or loop in bumpy conditions, movements of the pilot's body due to bumps are liable to cause movements of the controls and so large and sudden fluctuations in "g". It is then advisable to press the elbow into the side to steady it.
...
(iii) Stability in pitch.- This aeroplane, though just stable in a dive, tends to be a little unstable in pitch (or foreand-
aft) during turns; as the turn is tightened up so the elevator control tends to become lighter, or, at least, fails to increase in weight to a desirable extent. Therefore, care must be used with this control, especially in rapid manoeuvres. When flying in bumpy conditions at high cruising speed, the pilot's body is bumped severely on the seat, and this is very uncomfortable, even for a short time.

Then to the later Mk II manual revision (downloaded from Zeno's):

10. (i) Stability and control - This aeroplane is stable. With metal covered ailerons the lateral control is much lighter than with the earlier fabric covered ailerons and pilots accustomed to the latter must be careful not to overstress the the wings. Similar care is necessary in the use of the elevators which are light and sensitive.

And then aerodynamically similar Spitfire V manual:

10. GENERAL FLYING (i) Stability: The aircraft is stable about all axes.

Aerodynamics wise there is no difference between these and still early version claims the Mk.II little unstable in pitch during turns just like NACA found out in their tests of the Spitfire VA. However, later revisions of the manuals claim these planes stable. So, what's the difference?

Let's have look to the early Spitfire C.G. (center of gravity) diagram:

http://www.spitfireperformance.com/k...cg-diagram.jpg

Note the CG horizontal position 7.6 inches behind the datum line.

Then the later C.G. diagram for the Spitfire I (this was used for another project but CG related parts are unchanged), it's the same for the II and V:

http://target4today.co.uk/_posted_im...11/CoG_Iab.jpg

Note that without elevator inertia device the CG aft limit is 7.5 inches with the Rotol propeller. The earlier CG position, 7.6 inches, was too far aft without inertia device and the Spitfire VA, tested by NACA, apparently had the same problem (their measurements are not based on datum point but if measured from drawing, the CG during test was certainly close the aft limit if not behind it with the Rotol prop).

The claimed unstability in longitudinal axis was caused by CG being too far aft. Proof of this can be found also from Spitfire XVI manual:

41. General flying
(i) Stability
(a) At light load (no fuel in the rear fuselage tanks, no drop tank) stability around all axes is satisfactory and the aircraft is easy and pleasant to fly.
(b) When the rear fuselage tanks are full there is a very marked reduction in longitudinal stability, the aircraft tightens in turns at all altitudes and, in this condition, is restricted to straight flying, and only gentle manoeuvres; accurate trimming Is not possible and instrument flying should be avoided whenever possible.


PS: The later CG diagram for the Spitfire I also explains well the function of the elevator inertia device. The function and the reasons were the same in the P-51.

Over and out

Thanks MiG - I explained all this in an earlier posting but, as per usual Crumpp and co avoided/ignored/pretended it was irrelevant, with nonsense statements like:

Originally Posted by Crumpp

That is not a Spitfire Mk I load plan and is not applicable at all.

and continues to pretend that he knows best about everything...as he has done for years, here and on other forums. *Yawn*