Fw-190 Dora-9 vs P-51D Mustang

[davparlr]

Originally Posted by Soren

Chingachgook,

It wasn't my intention to put you down at all, so I apologize if thats what I achieved. My intention was to tell you not to rely on Mike Williams for German fighter performance data, as he's got the habbit of showing the worst possible figures he can find while trying to acquire the best possible for Allied a/c. That having been said, Mike's site is a good resource for data on Allied a/c.

Davparlr,

Eventhough the 109K-4 is superior to the P-51 over nearly the whole height band, its still interesting to note that they've got almost exactly the same ceiling, having only 66 ft between them.

Fact is the reason for the 109K-4's superior performance was its light weight and small size, cause engine wise the Merlin certainly did better at the extreme altitudes.

PS: If you're interested in 109 performance I can PM you the charts you need.

I am certainly interested although I don't know what PM is.

[lesofprimus]

PM is short for Private Message...

[davparlr]

Originally Posted by lesofprimus

PM is short for Private Message...

Ah, so. Thanks

[dtshedd]

The statistics don't explain why the P-51, which not only fares worse at the factors below (with the exception of the thickness), but was also heavier (Fw-190 Max. Weight: 4,839 kg versus P-51D Max. Weight: 5,489 kg) and had less power (Fw-190 2,240 HP versus P-51D 1,790 HP) , able to fly at roughly the same max speed (Fw-190 Max. Speed: 704 km/h. versus P-51D Max.Speed: 703 km/h), and rate of climb (Fw-190 Max. Climb: 1110 m/min versus P-51D Max. Climb: 1011 m/min)?

Airfoil Thickness Ratio - Higher is better.
Fw-190: Root= 15.3% Tip= 9% .
P-51D: Root= 14.8 or 15% Tip= 12%.

Wing Aspect Ratio - Higher is better.
Fw-190: 6.02.
P-51D: 5.81 .

Lift-loading - Lower is better.
Fw-190: 154.33 kg/sq.m. (31.5 lbs/sq.ft.)
P-51D: 181.73 kg/sq.m. (37.18 lbs/sq.ft.)

Power-loading - Lower is better.
Fw-190: 1.91 kg/hp. (4.22 lbs/hp.)
P-51D: 2.81 kg/hp. (6.2 lbs/hp.)

[davparlr]

Originally Posted by dtshedd

The statistics don't explain why the P-51, which not only fares worse at the factors below (with the exception of the thickness), but was also heavier (Fw-190 Max. Weight: 4,839 kg versus P-51D Max. Weight: 5,489 kg) and had less power (Fw-190 2,240 HP versus P-51D 1,790 HP) , able to fly at roughly the same max speed (Fw-190 Max. Speed: 704 km/h. versus P-51D Max.Speed: 703 km/h), and rate of climb (Fw-190 Max. Climb: 1110 m/min versus P-51D Max. Climb: 1011 m/min)?

Airfoil Thickness Ratio - Higher is better.
Fw-190: Root= 15.3% Tip= 9% .
P-51D: Root= 14.8 or 15% Tip= 12%.

Wing Aspect Ratio - Higher is better.
Fw-190: 6.02.
P-51D: 5.81 .

Lift-loading - Lower is better.
Fw-190: 154.33 kg/sq.m. (31.5 lbs/sq.ft.)
P-51D: 181.73 kg/sq.m. (37.18 lbs/sq.ft.)

Power-loading - Lower is better.
Fw-190: 1.91 kg/hp. (4.22 lbs/hp.)
P-51D: 2.81 kg/hp. (6.2 lbs/hp.)

I'm not sure what your question is. The Fw-190D-9 is clearly superior to the P-51D at altitudes below 25000 ft. After that, power drops off significantly and the P-51D has both airspeed and climb superiority over the Fw-190D-9.

[davparlr]

Originally Posted by Soren

While I agree completely with almost all of what you have said Davparlr, I must contest your claim that the P-51D ruled the skies over 25k before the advent of the Ta-152, for it certainly did not. The Bf-109K had a considerable performance advantage at both low and high alt over the P-51D.

Bf-109K performance at alt:

25k ft = 720 km/h (447 mph) / Rads open: 13.5 m/s (2,657 ft/min) - Rads closed: 15.5 m/s (3,051 ft/min)

30k ft = 702 km/h (438 mph) / Rads open: 9.7 m/s (1,909 ft/min) - Rads closed: 11.7 m/s (2,303 ft/min)

33k ft = 690 km/h (431 mph) / Rads open: 7.5 m/s (1,476 ft/min) - Rads closed: 9.5 m/s (1,870 ft/min)

35k ft = 679 km/h (424 mph) / Rads open: 6 m/s (1,181 ft/min) - Rads closed: 8 m/s (1,574 ft/min)

Service Ceiling: 12.7 km (41,6k ft)

Still looking for the Me-109K data. I got some from spitfireperformance and also a contradicting argument. The K-4 does seem to have some pretty good performance capability, especially at higher altitudes.

[Soren]

Originally Posted by davparlr

Still looking for the Me-109K data. I got some from spitfireperformance and also a contradicting argument. The K-4 does seem to have some pretty good performance capability, especially at higher altitudes.

Sorry Davparlr, I havent had the time lately to PM you the documents - I'll correct that soon. Infact if I get some spare time later I'll PM you them today

[davparlr]

Originally Posted by Soren

Sorry Davparlr, I havent had the time lately to PM you the documents - I'll correct that soon. Infact if I get some spare time later I'll PM you them today

Thanks, I would appreciate that.

[Sarge714]

One thing left out in the discussion is the effect on inertia coupling by the radiator placement on both aircraft.

The Fw-190D, with the radiator out front (causing the nose extension) plus the rear fuselage plug adds to inertia coupling. The P-51’s layout with the radiator below the wing and close to the cg actually slightly counters inertia coupling.

So in a high speed, high AoA, violent rolling fight the Fw-190D is at a major disadvantage.

[Parmigiano]

Originally Posted by Sarge714

One thing left out in the discussion is the effect on inertia coupling by the radiator placement on both aircraft.

The Fw-190D, with the radiator out front (causing the nose extension) plus the rear fuselage plug adds to inertia coupling. The P-51’s layout with the radiator below the wing and close to the cg actually slightly counters inertia coupling.

So in a high speed, high AoA, violent rolling fight the Fw-190D is at a major disadvantage.

.. but the 190 had weapons and ammo close to the centeline, while P51 had all this weight in the wings, so the inertia should put her at major disadvantage in every roll...

[Soren]

Originally Posted by Sarge714

One thing left out in the discussion is the effect on inertia coupling by the radiator placement on both aircraft.

The Fw-190D, with the radiator out front (causing the nose extension) plus the rear fuselage plug adds to inertia coupling. The P-51’s layout with the radiator below the wing and close to the cg actually slightly counters inertia coupling.

So in a high speed, high AoA, violent rolling fight the Fw-190D is at a major disadvantage.

Sarge714,

The radiator placement has no effect on enertia coupling. And besides this phenomenon only occured at VERY high speeds, speeds unaccesable to any WWII prop fighter.

And btw, the Dora's nose extension was a result of a switch from a radial to an inline engine. The radiators take up little space, and the weight isn't much either.

[lesofprimus]

Gotta agree with Soren and Parm on this one....

[Sarge714]

ReRead up on what Inertial Coupling is. It’s really interesting reading as they tried to figure out what was going on in the early 1950’s.

Speed is an important contributor because the faster you go the faster the roll rate, until you run out of stick force for the WW2 aircraft. It was more noticeable on aircraft like the F-100 because it had a 3000psi irreversible hydraulic control system so the pilot could obtain very high roll rates at high subsonic speeds. The key is a majority of weight distributed along the fuselage and a high roll rate at max AoA.

I’ll try to explain it. Put the aircraft at max AoA. Now add full aileron and roll the aircraft while maintaining max AoA. As the aircraft rotates, the nose traces a circle about the axis of rotation. The weight in the nose spinning around this circle is creating a centrifugal force that is countered by the tail surfaces. The faster you roll, the greater the centrifugal force, which can surpass the ability of the tail to over come it. Likewise, adding weight to the nose increases the centrifugal force. The resulting accelerated stall could (and has been) cause of in flight breakup.

The P-51 has around 800lbs of water and plumbing for the radiator. Having a larger engine most likely the Fw190D would need just as much if not more to help cool the engine.

The Fw190D with a heavier engine, radiator and possibility ballast in the tail to offset the nose weight all along the fuselage is a very good candidate of an aircraft with an inertia coupling issue.

[FLYBOYJ]

Originally Posted by Sarge714

ReRead up on what Inertial Coupling is. It’s really interesting reading as they tried to figure out what was going on in the early 1950’s.

Speed is an important contributor because the faster you go the faster the roll rate, until you run out of stick force for the WW2 aircraft. It was more noticeable on aircraft like the F-100 because it had a 3000psi irreversible hydraulic control system so the pilot could obtain very high roll rates at high subsonic speeds. The key is a majority of weight distributed along the fuselage and a high roll rate at max AoA.

I’ll try to explain it. Put the aircraft at max AoA. Now add full aileron and roll the aircraft while maintaining max AoA. As the aircraft rotates, the nose traces a circle about the axis of rotation. The weight in the nose spinning around this circle is creating a centrifugal force that is countered by the tail surfaces. The faster you roll, the greater the centrifugal force, which can surpass the ability of the tail to over come it. Likewise, adding weight to the nose increases the centrifugal force. The resulting accelerated stall could (and has been) cause of in flight breakup.

The P-51 has around 800lbs of water and plumbing for the radiator. Having a larger engine most likely the Fw190D would need just as much if not more to help cool the engine.

The Fw190D with a heavier engine, radiator and possibility ballast in the tail to offset the nose weight all along the fuselage is a very good candidate of an aircraft with an inertia coupling issue.

I think you're confusing inertia coupling with torque roll. Inertial Coupling is a phenomena that occurs at higher mach numbers with aircraft with real heavy fuselages and light wings (F-100, X-1A, X-2 and F-102 all had inertia coupling problems). The 190D didn't come close to the speeds required to induce inertial coupling.

[lesofprimus]

So endeth the lesson...