Author Topic: Some New Data Carts to chew on (Read 3023 times)

F4UDOA · « **on:** January 03, 2002, 11:03:00 AM »

Heya's,

I posted these docs on my Web page a while ago. However I didn't break out these two pages of comparison charts to be viewed. So here they are.

The first one shows comparisons of Drag Coefficients, Wing Loading, Power Loading etc.

Second is a Performance comparison.

What stands out in these charts to me are these things.

1. The P-38J has two 1600HP engines and has a VMAX of only 415MPH.

2. The Performance of the P-47D. It has outstanding Speed from sea level up to 30K at 440MPH.

3. The Drag Coefficients of these A/C. Based on these and available power I find it hard to believe that F4U does not accelerate better based on available power versus low drag. Could someone expain this?

4. Are AH stall speeds too high accross the board?

5. Based on the Navy's Range calculation the F4U-4 has a longer range than the F4U-1. In AH it has a shorter range. Why?

6. The P-38J has a relatively short range in comparison to other A/C. Why? I thought the P-38 had longer legs. Looking at the P-38 Manual it would seem that it consumed a great deal of fuel compared to the F4U and only carried marginally more fuel.

Any comments?

eddiek · « **Reply #1 on:** January 03, 2002, 11:25:00 AM »

F4UDOA, I am SO glad you reposted this info. I searched for it for hours last week, never found it.
FWIW, I remember someone pointing out the P47D as having the "wrong" engine, which they said accounts for the outstanding speed it gave. BS in my opinion, but that is what they said.
One thing I wonder when look at the charts is if the ones who did the testing on the birds had an F6F with the "revised" airspeed indicator? Grumman chief test pilot tested F6F and Corsair, found that even in formation flying, the Corsair "indicated" about 20 knots faster than the F6F, so they worked on the pitot tube and such til the airspeeds were identical when the planes were in formation. He also said that in testing side by side, the planes had identical performance and speeds at the low and high blower stages from 5K feet up to service ceiling, with the difference in main stage blower being the way the air was routed to the carb in each plane.
The tests were conducted in the summer of 1943, with the planes being an F6F-3 and an F4U-1D serial #17781.
From what I gather reading his summary, the F6F was a 400mph plane just like the F4U, and not 20-odd mph slower like all the tests show, and the sims model.
Just my thoughts and 2 cents worth on the subject.
Sorry I strayed so far off topic......<S>!

batdog · « **Reply #2 on:** January 03, 2002, 11:26:00 AM »

Well... first of all why did they use a P-38 J version. This kind of points at "old" data.
I think the 38's had some serious fuel/range problems to begin with. This is why Lindenburg was sent to show them how to properly trim and use engine management to get much more range out of their planes.

Other than that I quess one of the experten we see such as Widewing and co can comment w/much more Technical info I'm sure.

xBAT

P.S. F4UDO..what is your web page addy? The link on your profile doesnt seem to work.

[ 01-03-2002: Message edited by: batdog ]

Regurge · « **Reply #3 on:** January 03, 2002, 11:57:00 AM »

Neat stuff.

From the weight I would guess that p47D is a razorback. The notes imply it only has 1 dt instead of 3 so I guess its without the wing pylons too. Baugher lists the R2800-63 as 2300hp, not the 2600 here. Maybe this is one of them hot-rod jugs

. Anyway that performance is pretty impressive, even with overload ammo.

Range seems pretty wierd. Unless there is a digit missing it says the P51b has less range than P47!?

<edit> Just noticed internal fuel for the P47 was 305 gallons, which I thought means bubble-top too. So i dunno whats up with that.

Wow, take off run in a Jug is twice as long as f4u/f6f. Is that from flaps, or a big difference takeoff speeds?

[ 01-03-2002: Message edited by: Regurge ]

Widewing · « **Reply #4 on:** January 03, 2002, 12:05:00 PM »

Quote

Originally posted by batdog:
[QB]Well... first of all why did they use a P-38 J version. This kind of points at "old" data.
I think the 38's had some serious fuel/range problems to begin with. This is why Lindenburg was sent to show them how to properly trim and use engine management to get much more range out of their planes.

Other than that I quess one of the experten we see such as Widewing and co can comment w/much more Technical info I'm sure.
QB]

Well, I'm at the office today, so my reference material is not with me. However, I should mention that Lindbergh did not introduce a cruise method that was not already in the P-38 Pilot's Manual! He merely used settings that were already defined, while the rest of the 475th FG preferred to cruise in Auto-rich, at high RPM. This allowed them to respond faster to enemy aircraft, but used up to 30% more fuel.

It should be noted that when using max range power settings in the P-38 (J or L), your airspeed was bog slow. Yeah, it had comparible range to the Mustang, but you arrived later. Another issue was the need to step up speed and get those props into fine pitch BEFORE you found yourself in a fight. In the ETO, this typically happened once the fighters crossed into known enemy operating areas, or about 2/3rds of the way to the target. OTOH, the Mustangs cruised at higher speeds and were always better prepared (in terms of aircraft power and prop settings) for sudden combat. Having to power-up well in advance of combat diminished the Lightnings range by at least 10%. Things improved for the P-38 when the L arrived, because of "single lever" powerplant controls, which made getting the props and engines pushed up a far less complex and time consuming procedure (when seconds count, no one wants to be fiddling around with seperate prop and throttle controls). Still, the extended range cruising speed remained well below that of the P-51. As you all know, it is vitally important to enter a potential combat area with plenty of airspeed. The Mustangs could and did, the Lightnings could, but wouldn't if they wanted to have enough gas to get home. All of this factored into the general data used by the 8th AF to decide on which fighter would become the principle long-range escort.

Another fact: Lindbergh spent time with P-47 groups and Marine Corsair squadrons teaching them how to extend the range of their fighters as well. Here again, the pilots tended towards high speed cruising in Auto-rich.

My regards,

Widewing

[ 01-03-2002: Message edited by: Widewing ]

bolillo_loco · « **Reply #5 on:** January 03, 2002, 12:44:00 PM »

I thought the P-47D-30 and 40 which had the 2,595/2,600 hp rating with water injection had 370 gallons of internal fuel? were the planes not filled to full internal capacity? is there more data on the a/c that goes along with this chart? thanks F4UDOA

Regurge · « **Reply #6 on:** January 03, 2002, 01:07:00 PM »

Oops bolilo just reminded me the incresed fuel load in bubble-tops was 370, not 305 gallons. So i guess it is a razorback.

HoHun · « **Reply #7 on:** January 03, 2002, 02:05:00 PM »

Hi F4UDOA,

>1. The P-38J has two 1600HP engines and has a VMAX of only 415MPH.

The P-38J also has the highest drag coefficient, which counters its high power. Here's the list sorted for cubicroot(P)/Cd, which gives an impression of top speed relations (at sea level, since power is given at sea level):

F7F
F2G-1
XF8F
F4U-4
P-51B
F4U-1
P-47D
F6F-5
P-38J

(F6F-5 and P-38J are sperated by a big gap from the rest.)

>2. The Performance of the P-47D. It has outstanding Speed from sea level up to 30K at 440MPH.

It's interesting to compare the effect of the P-47D's turbosupercharger to that of the engine-driven supercharger of the P-51B: The P-51B is faster at low altitude and around each supercharger stage's critical altitude, but slower in the middle between the critical altitudes. The P-47D has no such performance "valley".

>3. The Drag Coefficients of these A/C. Based on these and available power I find it hard to believe that F4U does not accelerate better based on available power versus low drag. Could someone expain this?

Drag determines top speed. Power to weight ratio determines acceleration at zero airspeed. At low airspeeds, power to weight ratio dominates, at high airspeeds, drag dominates. Here's the list sorted by power (at sea level) to (gross) weight ratio:

XF8F
F2G-1
F7F
F4U-4
P-38J
F4U-1
P-47D
F6F-5
P-51B

Note that of the "2nd generation" fighters, the P-38J is at the top while the P-51B is at the bottom.

Regards,

Henning (HoHun)

Sundog · « **Reply #8 on:** January 03, 2002, 03:23:00 PM »

Just out of curiosity F4UDOA, when you refer to the range of the F4U-4 vs the F4U-1, are you relating both to their max range engine settings? I haven't tested it, just looking for some clarification is all. Thanks.

F4UDOA · « **Reply #9 on:** January 03, 2002, 04:51:00 PM »

HoHun,

I agree completely (Like I have a choice weather I can agree with the laws of Physics).

But having said that the brick wall of drag really hurts the P-38 even in the thin Air up high. You can tell based on it's climb at high alt. that it is certainly not lacking power. But as you said with high drag top speed is limited.

The Acceleration of the F4U really has me befuddled. I need to break out my Aerodymics book to get the equation but with a Power to weight slightly worse than the P-38J and a Cdo of .020 I would expect the acceleration to be very good. It's climb suffered because of some CLmax problems until a Paddle blade prop was adopted but the requirements for acceleration are fairly simple. Power to weight minus drag. Based on this I would expect the F4U-1 to be close to the P-38L in acceleration. I will throw some numbers around and post them.

Sundog,

No, I'm not basing it on Max rated settings. I'm looking at the bottom of the second chart posted where it shows based on the Navy's range calculator that the F4U-4 has a longer range than the F4U-1. The formula is shown at the bottom of the page.

Eddiak,

Do you have that test between the F4U and F6F done by Grumman? I have never seen a full copy. I do believe the F6F was a 400MPH fighter. I have my doubts about it being as fast as the F4U at 20K altought I know it close. In the test with the Zero and FW190 the F6F-3 and F6F-5 both reached 400MPH. The F6F-5 reached 409MPH at 20K with the F4U-1D hitting 413MPH. The F4U's big advantage is at sea level.

Bolillo and Batdog,

Here is the link to my homepage. The entire report is posted there. the is some more info on the P-38J also. Charts, HP, Manifold pressure etc. it is under the F4U comparative analysis link. It is 6 meg and in Adobe form. I would download it first if I were you

F4UDOA's web page

Hooligan · « **Reply #10 on:** January 03, 2002, 04:58:00 PM »

F4u-4 and F4U-1 ranges. If I read that chart correctly it says 237 gallons for the F4u-1. I believe the AH one is an earlier model with an additional fuel tank that carries 361 gallons internally.

Hooligan

[ 01-03-2002: Message edited by: Hooligan ]

Hooligan · « **Reply #11 on:** January 03, 2002, 05:04:00 PM »

Pyro told me part of the F4U acceleration puzzle at the con.

Sometime during the -1d production run they switched to a fatter "paddle-type" propellor. The propellor on -1s and early -1Ds did not have very good efficiency in the climb speed range. The new propellor resulted in slightly less top-end speed but markedly better climb and low-speed acceleration.

So, to some extent earlier F4Us have disapointing acceleration and climb due to poor prop efficiency at lower speeds.

Hooligan

HoHun · « **Reply #12 on:** January 03, 2002, 06:00:00 PM »

Hi F4UDOA,

>Based on this I would expect the F4U-1 to be close to the P-38L in acceleration.

Acceleration depends on specific excess power, which is expressed as a climb rate.

Fortunately, for the aircraft in the F4U-4 comparison, we have specific excess power for 1 G flight at best climbing speed recorded in shape of the climb rate graphs :-)

Based on this, I can say that the P-38J will accelerate faster from its best climb speed than the F4U-1. (A slight inaccuracy may result from different speeds of best climb, but at sea level the P-38J has 3700 fpm specific excess power available to compared to just 3100 fpm of the F4U-1. The P-38 is clearly ahead there.)

Another specific excess power data point is provided by the top speed in 1 G flight - obviously, when no further acceleration is possible, the plane has no excess power available.

In other words, at 338 mph will F4U-1 will out-accelerate the P-38J since the latter won't accelerate at all :-)

Somewhere in between in the break-even point, where the lower drag of the F4U-1 will begin to pay off and overcome the power advantage that enabled the P-38J to accelerate faster initially.

Regards,

Henning (HoHun)

M.C.202 · « **Reply #13 on:** January 03, 2002, 07:15:00 PM »

All the numbers point to a need for a one plane Air Force....

The F7F

Bombs, torps, rockets, cannon, .50cals, radar for night work, speed and power

Yeh, I know "But it did not see combat". I still want it , designed, production line built (yep small #'s) in WWII, and not a jet.
Yes, with perk points.

F4UDOA · « **Reply #14 on:** January 03, 2002, 08:47:00 PM »

Hooligan,

I'm surprised Pyro said that. The prop change has been my personal battle cry of the F4U for almost a year. The new prop blade design albeit three bladed was the 6501A-0 as listed in the charts. It says right in the front of the F4U manual that the new prop design increases performance over previous models and should be used whenever possible. If you look at the F4U Vrs P-51 or FW190 test it mentions the prop change and the increase in performance there as well. It just took until Version 1.08 to make it into AH. However acceleration is another subject.

HoHun,

I have seen the charting method for excess power to climb. One line represents Horsepower available and the next is HP used to attain a certain speed. The gap between the two is climb. My issue is that climb has more variables than just Thrust-Drag/ Mass.
Climb has Lift coefficients. And the P-38 has a high Max Cl because of high aspect ratio where as the F4U has a relatively moderate Max Cl(no Flap with prop in case Niklas is reading) of 1.48. This reduces the climb of the F4U in relation the P-38. So the 3100FPM vrs the 3700FPM are really not directly proportion to acceleration. So if you calculate Thrust-Drag / Mass at a given speed say 150MPH I am will to bet that F4U does almost as well as the P-38 despite not being able to climb.

Any thoughts?