Low alt performance of Big Planes in AH

[funked]

Fishu, water injection on the P-47D was the same as MW 50 on German planes.  Except Republic actually installed it instead of just fooling around with prototypes for 2 years.    

P-47D30 had 2600 hp with water injection, and that power was sustained from sea level up to 25,000 feet.

[This message has been edited by funked (edited 08-10-2000).]

[Fishu]

 

Originally posted by funked:
Fishu, water injection on the P-47D was the same as MW 50 on German planes.  Except Republic actually installed it instead of just fooling around with prototypes for 2 years.    

P-47D30 had 2600 hp with water injection, and that power was sustained from sea level up to 25,000 feet.

[This message has been edited by funked (edited 08-10-2000).]

..and german planes are on their best in low, while P47 gains that higher where germans lack the supercharger...

[F4UDOA]

Badboy,

I was just looking at your last post and I was hoping you could do the same calculation and show the math for the F4U-1D. Top speed at sea level for this A/C should be 359MPH.
The engine delivers the same rated horsepower as the F6F-5 at 2250HP from the manual. I noticed you used 2000HP for your calculation but I'm not sure if you were using BHP or HP. In any case here are the stats for the F4U-1D.

Prop efficiency I don't know but the blade design is different than that used in the F6F-5. The F4U-1D used the 6541A-0 or 6501A-0 which is different from early model F4U's and is said to increase performance as stated in the pilots manual.
Altitude=Sea level
HP=2250HP
Wing Area=314^2ft
Cdo=This is the question to be answered. How low was the F4U Cdo. I unfortunately do not know how to calc. this number as a static value. I know it varies with speed but I don't know how to determine what the "baseline" Cdo of any A/C is. Obviouly it is very low at higher speed to allow the F4U to reach a high speed at low alt. I believe this is mostly because of high wing loading and a low aspect ratio of 5.35.

Thanks
F4UDOA

[wells]

Ok, here's some f values calculated from the Cd0, wing area and data for max speed at sea level, using my spreadsheet that I made available on this board a little while back.

P-51D - 0.0169 * 235.75 = 3.98 sq ft
P-47D - 0.02064 * 300 = 6.19 sq ft
F4u - 0.018 * 314 = 5.65 sq ft
P-38J - 0.02264 * 327.5 = 7.41 sq ft
109G - 0.0258 * 173 = 4.46
190A - 0.02328 * 197 = 4.59

Looks reasonable to me

[This message has been edited by wells (edited 08-10-2000).]

[funked]

You got it Fishu.

So P-47D-30 has about the same speed as a Fw 190A-5 at sea level, but at 25,000 feet the 190 has lost a lot of power, while the Jug still has full power and is much faster.

[Fishu]

 

Originally posted by funked:
You got it Fishu.

So P-47D-30 has about the same speed as a Fw 190A-5 at sea level, but at 25,000 feet the 190 has lost a lot of power, while the Jug still has full power and is much faster.

I think I've known and said that long time ago.. but thing is that P47 low altitude seems to be a beast, which I didn't really mind it to be in WB or real life stories, until above 20k...
Could think that 5k P47 would be dead meat for advantageous 190 or 109, but it performs *very* good against them in AH that low. (at least did?)

[funked]

Fw 190A-5 and all Me 109 variants in AH will out climb and out accelerate the P-47D at 5k.  In my experience they can out turn the Jug too.  Of the Luftwaffe fighters, only the Bf 109F-4 is slower than the Jug at 5k, and only the Fw 190A-8 is outclimbed/accelerated by the Jug at 5k.  The only way the Jug is not dead meat is if he starts higher or uses his superior armament and armor.  Above 5k his diving ability becomes a factor if he needs to escape.

Real life Luftwaffe results were not good against the P-47 at any altitude, so I wouldn't complain.  If anything, the D-30 is conservatively modeled - its performance is close to some data I have seen for D-25 (2300 hp).


[This message has been edited by funked (edited 08-11-2000).]

[Citabria]

no one realizes that the p47 is just as slow as the p38 on the deck in AH  

[ispar]

Niklas,

I don't know if you've already been corrected. You said way back:

"The Jug? Try to bring 15000 pounds into a roll motion"

Ahem. It has been said often enough to you that weight matters very little in aerodynamics. The T-Bolt had the best roll rate of any USAAF fighter, bar none, and the second best roll rate in the ETO. Only the FW-190 out rolled it. How could weight possibly effect?
The weight of the fuselage is lifted at all, and the weight of the wings doesn't matter because rolling is function of increasing the lift on one wing and decreasing it on another. Pure aerodymanics. Weight effected the dive of an airplane. Period. Bye.

------------------
"If I told you that there were a squadron of fighters waiting to pounce the moment you fired at me, would you believe me?"

"No."

"Er... how about just one then?"

[wells]

I think he was talking about roll acceleration, where weight is a factor.  The wings, landing gear, guns and ammo only weigh about 3500 lbs in the P-47.

[niklas]

ispar, you´re absolutly right if you only compare sustained max. roll rate. I said myself later with the "example"of the 747 that weight is not important for a max. roll rate. But like for the topspeed you must first accelerate to the max. roll rate, and here DOES weight play a roll, in the acceleration progress (not only weight but where the mass is or how far it is outside of the center of gravity). In a scissor manoevre for example, roll acceleration is important too- scissors in a slow fight against a P38 work fine usually   . And now it depends on the test method.
Btw, if you´re convinced that the P47 outrolled the F4U than adress your posting pls to F4Udoa - now, after F4Udoa admitted that the F4U is only superior compared to other american aircrafts at ultra low speeds and very very high speeds you can be right for the usual combat speed range. But you have to clarify that with him, not with me
niklas

[wells]

actually, the P-47's roll rate kinda sucked
 http://naca.larc.nasa.gov/reports/1952/naca-tn-2675/

but it could definitely outroll a 109 at high speeds

[F4UDOA]

Niklas,

I have data on the rolling ability of the F4U, P-47 and all other American types. In comparison testing the F4U was said to be equal to the FW190A5. These test were not documented by NACA so I will not debate the fine rolling qualities of the FW190.
However the P-47 was less than a steller rolling A/C. I have however seen some mention of the P-47 being an exceptional rolling A/C. However I do not now where this information durives. The factors that affect roll positively are some of the that affect range negatively. They are

1.Aspect ratio. It seems that A/C with a high apsect ratio have a purpose build for range. IE P-38, A6M-5 Zero and your 747 Niklas. But these long narrow wings take a long time to get moving. I believe the Spit also suffered from this but It's range also seemd to lack from small internal fuel stores. The Spit is an airplane that baffles me completely.

2. Area of Aileron.  This seems to be the down fall of the P-47. Either the ailerons are not far enough out on the wing on the are displaced is just to small. If you cannot deflect enough air you will not have positive aileron response.

3. Stall speed. If the P-47 had the best ailerons in the world it would make a difference at low speed. With a stall speed as high as the Tbolts you don't have to deflect your ailerons very far before your on your inverted heading for terra firma.
In anycase they would appear ineffective.

4. Weight. Not total weight but distribution of weight. The F4U after the very early model carried no fuel in the wings so it had very little to slow down the start of a roll. By contrast the P-38 would have a hard time entering a roll especially at low speed where the airflow is much less.

It seems like there is a inverse relationship between range and roll. It is hard to have both. The Mustang is the exeption to that rule as there are exceptions to all rules of aerodymamics. The Laminer wing of the Mustang made for great range while the relatively low aspect ratio allowed for a high rate of roll although it suffered at low speed. By contrast the Grumman F6F had a low aspect ratio large ailerons and rolled well at low speeds but was only in the range of a P-47 at high speed, go figure.

Later
F4UDOA

[wells]

All other things being equal, roll rate is only dependant upon wingspan.  You can have a wing of any area or aspect ratio, but the higher span will roll slower.  The thing with the Spitfire and P-47 with their elliptical planforms, is that the ailerons have to be 'inboard' a tad and the hinge line is at an angle, both of which reduce the rolling authority.  The elliptical planform is good though, for lower roll inertia.

[F4UDOA]

Wells,

Why was the F4U's rolling ability so exceptional? It had quite the wing span.

Do you have any NACA docs on it??

Thanks
F4UDOA