A newbies impression of the 109 and spit

[MiG-3U]

Quoting from the tests of the Spitfire I K.9789:

http://www.spitfireperformance.com/k9787-fuel.html

2. Handling and Flying Qualities.

The aeroplane has been flown at the following loadings and positions of gravity:-

Load for Weight (lb.) C.G. Position (inches aft of datum)
Typical service load ---5819---7.7
Extended aft.---5819---8.6
Forward limit---5338---5.8
...
(v) Stability - The aircraft is laterally stable at all speeds except in the immediate vicinity of the stall when it is unstable. The aircraft is directionally stable engine 'OFF' and 'ON' at all speeds, but on the climb this is difficult to assess owing to insufficient rudder bias. Longitudinally, the aircraft is stable with centre of gravity forward, but is unstable with centre of gravity normal and aft with engine 'OFF' and 'ON'. Longitudinal stability records are attached.

Later limits for the Spitfire 1A & 1B without and with the elevator inertia device (bob weigh):

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

3 With original standard elevator
Elevator inertia device---NIL---3.5 lb.---6.5 lb.
with De Havilland propellers--- 7.9 in.---8.2 in.---8.6 in.
with Rotol propellers---7.5 in.---7.8 in.---8.2 in.

With the Rotol propeller (as was in the Spitfire II and NACA tested Spitfire VA), the typical service load CG of the K.9787 was beyond the later limits without the inertia device (7.7 in. vs. 7.5 in limit). The extended aft CG of the K.9787, 8.6 in. aft the datum point, was clearly beyond the later limit, 8.2 in. even with the heavier 6.5 lb. weigh in the inertia device (with Rotol propeller).

RAE on the NACA stability testing posted by lane:

http://forum.1cpublishing.eu/showpos...&postcount=175

2.2. Stability and control at medium and low speeds. This was covered admirably, with the exception of static longitudinal stability. Trim at two C.G. positions were not done, so that the neutral points remained undetermined.

NACA did not test stability at different CG positions and, as NZtyphoon noted, they had no documentation about the correct CG limits nor accurate drawings.

Over and out