A newbies impression of the 109 and spit

[Crumpp]

Obviously a pilot would not or only in dispair engage in a manoeuver that he would be certain to break his plane with. Nevertheless his plane might not have broken up against all odds, if he was really lucky.

Absolutely. Failure points are a range and outliers exist. You can be a lottery winner on either end of that range.

I am sure every poor soul who has looped his aircraft into the ground was hoping to be a lottery winner in the last moments of their life.

[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

[Crumpp]

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

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.

Read the Pilots Operating Notes as you posted:

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.

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?

Bob-weights......

[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*

[Kurfürst]

Selective quoting. My favorite sin!

[Crumpp]

NZtyphoon

Reading is fundamental.

[Crumpp]

I noticed that is MIG's first post....

[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