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

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


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.
 
davparlr said:
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.
Click to expand...


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
 
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...
 

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.
 
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.
 

I don't think you understand what Inertia Coupling is. Calc the physics involved and I think you'll be surprised what you see with the Fw190D.

From High Speed Flight

A few of the experimental aircraft encountered a new type of behavior known as inertia coupling, a behavior that was not fully appreciated until the F-100 and F-102 also encountered it. Inertia coupling resulted from the tendency of the new generation of high-speed aircraft to concentrate most of the weight in a long thin fuselage, a departure from the distribution of subsonic fighters. The X-3 configuration is an excellent illustration. Even though its high-speed performance was disappointing, the X-3's unanticipated susceptibility to loss of control from inertia coupling contributed to understanding the problem. With much less weight in the wing and tail, the dynamic motion in a maneuver could cause the inertia of the fuselage to overpower the aerodynamic stabilizing forces of the wing and tail. In the worst cases the pilot lost control and the resulting abnormal air loads caused airframe structural failure. The early F-100A models are remembered as a classic example of susceptibility to inertia coupling, although the initial F-102A models also encountered the problem.

From Cornell tam.cornell.edu/~tuhin/Aesi.prn

The prediction and analysis of airplane spin characteristics and design of recovery strategies has been of great interest to designers since the beginning of aviation. This problem has assumed more importance in recent years on account of significant losses that have occurred to military and general aviation aircraft because of out of control motions associated with spin. Modern day combat aircraft are required to perform maneuvers at high angles of attack. The aerodynamics at high angles of attack is nonlinear. In addition, there are nonlinearities due to inertia coupling during rapid roll. These nonlinear phenomena can cause stall and then spin departure.

From NASA Report NASA-TP-1538 1979-12

A real-time piloted simulations has been conducted to evaluate the high-angle-of-attack characteristics of a fighter configuration based on wind-tunnel testing of the F-16, with particular emphasis on the effects of various levels of relaxed longitudinal static stability. The aerodynamic data used in the simulation were based on low-speed wind-tunnel tests of subscale models. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative low-speed combat maneuvering. Results of the investigation showed that the airplane with the basic control system was resistant to the classical yaw departure; however, it was susceptible to pitch departures induced by inertia coupling during rapid, large-amplitude rolls at low airspeed. The airplane also exhibited a deep-stall trim which could be flown into and from which it was difficult to recover. Control-system modifications were developed which greatly decreased the airplane susceptibility to the inertia-coupling departure and which provided a reliable means for recovering from the deep stall.

----------------

There are more tech reports out there in Inertia Coupling. It's a real interesting area and something that can be applied to WW2 aircraft in predicting their performance.
 
I could assure you I know what Inertial Coupling is, I worked at a flight test facility for 3 years. Links are Interesting, but the point here is the -190D was never a subject of Inertial Coupling and your sources never discuss WW 2 aircraft. The low speeds spoke about in the article are still high mach numbers when compared to WW2 aircraft. The 190D was never reported to experience this is any form, even at altitude, and for that matter any WW2 aircraft. Here is a copy of the USAAF flight test report from Wright Patterson on this aircraft, not even a hint of anything related to Inertial Coupling is remotely mentioned.

http://www.wwiiaircraftperformance.org/fw190/wright-field-fw190d-9.pdf

Again, Inertial Coupling came to the forefront during the development of early turbine aircraft where they had large heavy fuselages with large engines coupled with little or light wings...

Here....

Dryden Online Education - Introduction to Flight Testing - Aileron Roll

"Fighter aircraft with high roll rate capability often experience another coupling phenomenon known as "inertial coupling". Inertial coupling may occur if there is a large difference between the roll moment of inertia and the yaw or pitch moments of inertia for the airplane. This is often the case for fighters which have short stubby wings (low roll inertia) and long fuselages with heavy engines, electronics, fuel, etc. (high pitch and yaw inertia). When such an airplane is exposed to high roll rates along the fuselage axis, the high mass concentration along the fuselage may cause it to behave like a "dumbbell". The centrifugal force due to the roll will cause the nose and tail to try to swing out perpendicular to the rotation axis. "

The X-3, one aircraft notorious for Inertial Coupling didn't experience the condition until mach .92

NACA X-3 supersonic research flight

My father in law is a retired test pilot and actually worked at Edwards AFB for a number of years - I'm going to get his take on this...
 
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