Quote:
Originally Posted by Crumpp
Longitudinal Instability and the Pitts elevator are not comparible. There is a huge difference between the minimal stability exhibited by a Pitts and a dangerous instability exhibited by the Spitfire.
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Yeah Right, the Spitfire was so dangerous that pilots dreaded flying the machine and it was roundly condemned by the A&AEE, the RAE and by Supermarine test pilots, and has since been banned by the FAA and other aviation authorities worldwide.
No doubt Kurfurst will bring up the Spitfire V crashes described in Shacklady and Morgan...pp 160-161 (I think)
Or he'll post the attached paper and claim that this proves how dangerous and unstable the Spitfire was because so many of them broke up in flight.
So, to save all our time from his predictable arguments here's what Supermarine Chief Test pilot Jeffrey Quill had to say about the "dangerously unstable" Spitfire (Spitfire:A Test Pilot's Story. John Murray, 1983):
"In a high-performance fighter, lack of stability can be exceedingly dangerous in the course of manoeuvring at high speeds...Therefore, in aeroplanes such as the Spitfire, which were entirely manually controlled, any inherent instability was unacceptable and potentially dangerous....
There were other factors which affected the aerodynamics of the stability of the Spitfire. For example the aerodynamic characteristics of the elevator itself (as opposed to the fixed tailplane) also had a major influence on stability and at Supermarine we exploited this and
increased the stability margins as we moved from one mark of Spitfire to another. (229-230)
In general configuration the Mk I and Mk II production aeroplanes were almost identical to the prototype and
so there was no problem with their stability. (231-232)
The Mk III Spitfire did not go into production, but the success of the bobweight experiment in curing its instability...opened up the possibility of its use for later marks of Spitfire....which was just as well as we had to...respond to a nasty situation which developed in 1942.
The Mk V aircraft was...in full service with Fighter Command and,...a fair amount of additional operational equipment had gradually crept into the aircraft, most of it stowed within the fuselage. The aftmost acceptable position for the aircraft's centre of gravity had been fixed in the normal course of flight testing by the firm and by the A & AEE....Any rearward movement of the centre of gravity in service, for whatever reason, would begin to destabilise the aircraft. Therefore, for each sub-variant of the Mk V detailed instructions for the correct loading of the aircraft were issued to squadrons....However the importance of these loading instructions was not generally appreciated in squadrons and in the daily round of operational activity they tended to be disregarded." (pages 232-233 -Quill goes on to describe 65 Sqn's Spitfire Vbs which were found to be dangerously unstable)
There was thus a real chance that, as of that moment, in almost every squadron in the Command Spitfires were flying in a dangerous state of instability....Up to that time there had been a distressing and increasing incidence of total structural failure of Spitfires in the air, which was causing great concern in the MAP and especially at Supermarine. (pages234-235)
....our aerodynamicists at Hursley Park thought that an even more effective answer could be obtained by enlarging the horn balance of the standard elevator and this we did in stages. The effect was astonishing.
At last a way had been found to improve the basic stability of the aeroplane, thus giving more flexibility in centre of gravity movement, without our having resource to any enlargement of the fixed tail surfaces....The enlarged horn balance of the elevator produced a slightly unpleasant 'feel' of the aeroplane at low speeds...This effect was trivial by comparison with the
gains in stability margins." (p 237)
Once the bobweights had been introduced and, in later marks, the modified mass balances on the elevators...it was statistically established that, as soon as the longitudinal stability of the Spitfire was thus brought under control, the problem of the unexplained breakings-up of aircraft in mid-air,...'softly and suddenly vanished away'. (page 238 )
Note the comments that stability margins increased over the course of Spitfire production; with the introduction of the Griffon engined Spitfires, and especially the five bladed propellers of the 65 series the size of the tail surfaces were increased to help cope with the bigger blade area and extended nose - there were some marginal instability problems, but not enough to make the aircraft dangerous. There were problems with the early Spitfire F. Mk 21's control characteristics, but these were ironed out with further developments in the elevator balance weights and configuration. The Mk Vs breaking up in flight were badly loaded with extra equipment in squadron service, with their cg pushed too far back, thus they were dangerously unstable, but this was not an inherent problem with the airframe.
No doubt Crumpp will try to claim that with his vast aviation experience he knows better than Jeffrey Quill and there'll be other smokescreens by another Spitfirephobe who has posted here but the fact is that All claims about the Spitfire being inherently dangerously unstable are quite false and not worth bothering with.