A newbies impression of the 109 and spit

[NZtyphoon]

Originally Posted by Crumpp

That is not a Spitfire Mk I load plan and is not applicable at all. The NACA was well aware of the CG limits and capable of performing a proper weight and balance.

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

Yeah right, it says "C.G Diagram" in nice big letters at the bottom so people who can read understand it has nothing to do with the centre of gravity of Spitfire Mk Is.

NACA report Measurements of the Flying Characteristics of the Spitfire Va: As per usual Crumpp has fudged what the report actually says:

(Tests, Results and Discussion, page 5) All of the flying qualities tests were made with the center of gravity at a distance of 31.4 inches behind the leading edge of the wing at the root. The mean aerodynamic chord of 85 inches was computed to be 4.80 inches back of the leading edge of the wing at the root. The center of gravity was therefore at 31.4 percent of the mean aerodynamic chord. Because no accurate drawings of the Spitfire were available, the calculated location of the mean aerodynamic chord may be somewhat in error.

The center-of-gravity location with full military load is not known.

Crumpp has chosen to completely ignore that NACA's own report states that their calculations might have been in error, nor did NACA know what the cg was with full military load. " The NACA was well aware of the CG limits and capable of performing a proper weight and balance." completely wrong.

Originally Posted by Crumpp

Reading is fundamental.

[Kurfürst]

More selective quoting and speculation.

[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

[robtek]

All this writing, or better copy 'n pasting, doesn't change the fact that the stick forces and stick travel for the elevator control in the early marks of the spitfire were too low and that has been changed in the later marks with the "BoB-weights".

If the low forces in connection with the small travel weren't regarded as dangerous, no change would have been necessary!

[bongodriver]

If the low forces in connection with the small travel weren't regarded as dangerous, no change would have been necessary!

not true, it was merely improved, not changed because it was dangerous, was everything that changed with the 109 do so because it was dangerous? I keep hearing how fantastic the leading edge slats were and then they were removed.........

[robtek]

Originally Posted by bongodriver

not true, it was merely improved, not changed because it was dangerous, was everything that changed with the 109 do so because it was dangerous? I keep hearing how fantastic the leading edge slats were and then they were removed.........

Now that will be really, really hard to proof, All Bf109 / Me109 had and still have the slats!

And the rest of your opinion is grasping for straws, imo.

[bongodriver]

And the rest of your opinion is grasping for straws, imo.

IMO all the theories on the spitfire so far are the same.

[Al Schlageter]

Originally Posted by bongodriver

not true, it was merely improved, not changed because it was dangerous, was everything that changed with the 109 do so because it was dangerous? I keep hearing how fantastic the leading edge slats were and then they were removed.........

Some pilots had the slats were wired shut, but that was the exception not the rule.

[bongodriver]

Originally Posted by Al Schlageter

Some pilots had the slats were wired shut, but that was the exception not the rule.

Yes I just realised I meant disabled instead of 'removed', also it was an idea theorised by the americans on how the 109 might be improved after tests on captured aircraft.

[NZtyphoon]

Originally Posted by robtek

All this writing, or better copy 'n pasting, doesn't change the fact that the stick forces and stick travel for the elevator control in the early marks of the spitfire were too low and that has been changed in the later marks with the "BoB-weights".

If the low forces in connection with the small travel weren't regarded as dangerous, no change would have been necessary!

The reason bob-weights were adopted was because several Spitfire Vs had been destroyed through poor loading at squadron level; this has been explained by Supermarine's Chief Test pilot Jeffrey Quill, although some Spitfirephobes consider him to be so totally biased he's incapable of telling the truth Of course we have to believe these "experts' such as Crumpp or Barbi, and not Quill, who was the chief propagandist of the Spitfire:

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....

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)

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 )

To say that they were adopted because of inherent design problems with the Spitfire Is and II is wrong; they were used on the Spitfire III because it had developed cg problems and adopted in Spitfire Vs because of poor loading and increased equipment.