AAF Test Early F4U-1

[justin_g]

Originally posted by Sable
Military power on the P-51B/D was 3000rpm, 61" HG.  The 2700rpm/46" is a reduced power setting, so that explains the poor performance.  It would be the equivalent of using a 2550rpm/45" setting on the F4U.

Interesting. I used UK/RAF data(since I haven't found any US data at anything except WEP performance), which list the power ratings as:

Max. climb & level continuous: 2700rpm & 46"map
Combat 5 mins. limit: 3000rpm & 67"map*
* 61"map may be used for 15 minutes

At 2550rpm & 45"map the F4U-1 would outclimb the P-51B by 250fpm below 7500ft, equal climbrate up to 23000ft, above that the F4U-1 lower by up to 500fpm.

[Sable]

Mike and Neil have a couple of US tests of V-1650-3 equipped P-51B's here  and here.   Unfortunately the first one, while being at the 61" power setting, is tested at 8400lbs, and the second is at the 67" (WEP) power setting.   Page 8 of this document has a chart with a comparison of the F4U-1 and P-51B (as well as the P38 and F4U-4) at their WEP powers.  It seems like they would be pretty close at their normal weights and military power.

[F4UDOA]

Justin,

The Pony in the AAF test is a P-51A/F-6. So the Mil power rating would have been approx 46" MAP. However I have seen that engine run up to 60" MAP in some test. That is why I wonder what MAP it was tested at considering it outclimbed the Hog up to 10K. At 46" there is no way that it could have unless the F4U was running at less than 50".

The Navy test is the P-51B however I have never seen the climb chart for that one. Also the F4U-1's used in thse test both had ADI and a paddle prop. Different ballgame.

[Widewing]

Originally posted by Sable
I think you have to keep in mind that interservice rivalry went both ways.  Note that the F4U-1 in the P-51B test is running a higher power setting, increased water injection flow rate, a different prop, and was drag prepped.  The production F4U-1A, was slower through most of the altitude band.  Also in the test they list both F4Us as having a 750-1000fpm climb rate advantage!  That really makes me wonder what power setting they were using on the P-51 - check out the chart on page 5 of this document.  

I thought about commenting on this last evening, but was simply too tired to bother.

Anyone accepting that Navy test on face value should report to Brooklyn and sign the contract for their bridge. The Navy did just about everything they could to maximize the F4U-1 and minimize the Mustang. This test is useless for anything beyond its amusement value.

When comparing unsullied test data for the P-51B and the F4U-1, you see that the Mustang wins easily in terms of performance. Due to supercharger gearing, the P-51B loses speed gradually until the F4U-1 is close at 20,000 feet. But, go a bit higher and the P-51B's blower shifts and the Mustang disappears like a fart in a tornado.

In terms of climb, the P-51B outclimbs the F4U-1 with ease over 95% of the curves.

All of that said, the F4U-4 more than equalizes the equation.

An added thought: It has always seemed to me that North American and Republic were much faster at incorporating major improvements into production aircraft than Lockheed or Vought. In Vought's defense, the ultra-conservative approach of the Navy to introducing upgraded aircraft may be the cause. There's little doubt that Grumman's F7F and F8F could have been in service many months sooner, but it seems that the Navy was far more accepting of the status quo than the AAF.

My regards,

Widewing

[Bronk]

Originally posted by Widewing


An added thought: It has always seemed to me that North American and Republic were much faster at incorporating major improvements into production aircraft than Lockheed or Vought. In Vought's defense, the ultra-conservative approach of the Navy to introducing upgraded aircraft may be the cause. There's little doubt that Grumman's F7F and F8F could have been in service many months sooner, but it seems that the Navy was far more accepting of the status quo than the AAF.

My regards,

Widewing

Just a thought . Might it because they had to land on a boat and not a runway. Id be a little conservative also.





Bronk

[Saxman]

And yet, this same "progress-minded" AAF decided the status quo did the job just fine and there was no need to push the development of the P-80, which could ALSO have seen deployment during WWII.

[Widewing]

Originally posted by Saxman
And yet, this same "progress-minded" AAF decided the status quo did the job just fine and there was no need to push the development of the P-80, which could ALSO have seen deployment during WWII.

If you research the P-80 you'll see that the aircraft evolved as fast as the technology would allow. The first prototype didn't fly until January of 1944. Even that was delayed due to having to wait for a British engine to be delivered.

The P-80 wasn't adequately debugged until well into 1946. There was zero chance that the P-80 could have seen truly combat ready before 1946. Had the program been started in 1941, then maybe. But the contract wasn't signed until the fall of 1943.

My regards,

Widewing

[justin_g]

Originally posted by F4UDOA
Justin,

The Pony in the AAF test is a P-51A/F-6. So the Mil power rating would have been approx 46" MAP. However I have seen that engine run up to 60" MAP in some test. That is why I wonder what MAP it was tested at considering it outclimbed the Hog up to 10K. At 46" there is no way that it could have unless the F4U was running at less than 50".

The Navy test is the P-51B however I have never seen the climb chart for that one. Also the F4U-1's used in thse test both had ADI and a paddle prop. Different ballgame.

Well, I was only considering the USN comparo - as you can see, I used the Mil power climb chart you posted of one of the F4U-1's used in that trial. The Mustang is from RAF data.

For the AAF trial: The card on the last page claims the F4U-1 climb power was 2700rpm & 50"map(afaik not a standard rating) but with rather high "indicated" climbrates of 2800fpm@5k, 2350fpm@15k & 1950fpm@25k?!.

The BuAer docs for F4U-1 at 2700rpm & 53"map(mil pwr) indicate climbrates of 2200fpm/2050fpm/1250fpm for those altitudes.

AAF docs here indicate that the P-51 at 3000rpm & 46"map would be superior to the BuAer F4U-1(mil pwr) below 12-15,000ft.

[F4UDOA]

The BuAer docs for F4U-1 at 2700rpm & 53"map(mil pwr) indicate climbrates of 2200fpm/2050fpm/1250fpm for those altitudes.

Justin,

Do you have the F4U-1 BuAer charts? I have the Vought charts and the British test but not the BuAer. The numbers you spec are more in line with the Normal power than Mil power (50"+).

Your right the top speed MAP says 53.5" and climb power is 50" but those test were done in February 1943. The test against the Pony were done in May 1943 and at that time the highest MAP reached was 49". I getthe feeling that the Hog was sitting on the ramp somewhere breaking slowly for a few months before they drug it out for testing.

BTW, I know that testwas in Feb because of an British AIR-1777 doc I have that list the AAF results (speed/MAP/HP) and it is dated in February so the test could have even been earlier.

WideWing,

The AAF did the test I posted and besides complaining about the F4U they could not seem to defeat it in close in dogfighting. Why do you think they used a stripped P-38G for testing instead of a combat aircraft?

BTW the results of the test compare very similarly to the Robert Johnson artical you posted a while back.

The performance of the P-51B and F4U-1A with 2250HP are not that far when 100 octane fuel is used below 25K.  The -1A will hold some advantage even in climb as shown by the performance curves. The trick is not to get carried away with the F4U-1 that was configured as a test bed for the F4U-4. The F4U-1A in that test was running at 60" MAP and 2250HP same as production A/C of the time.

[justin_g]

Curve 2 is military power, 2000hp @ s/l & 12,039lbs. From this website

[justin_g]

Btw, just for laughs - who would like a 377mph Mustang I in mid '43?



377MPH AT SEA LEVEL THAT IS!

[Saxman]

The "What we've got is good enough" delays in the USAAF and US military in general went back well before 1943. The US began experimenting with jet propulsion BEFORE the bombing of Pearl Harbor (I think it was roughly around the same time the Brits and Germans). IIRC, the Bell Airacomet first flew under jet power c.1940/41 (not entirely sure of the date there). Not particularly impressive performance, (I think the P-51 and late-model Hogs were faster) but it WAS flying. It's just that after entering the war the US focused its attention on churning out existing designs, rather than moving development on a lot of more advanced projects, focusing on winning the war with what was proven, rather than experimental uberfighters (in part why nothing was made of monsters like the Chain Lightning).

Anyway, my main point was that the USN wasn't the only branch of service guilty of not putting time into R&D (point of order: Wasn't the F6F the ONLY American fighter to begin development AFTER the US entered the war?)

[Widewing]

Originally posted by Saxman
The "What we've got is good enough" delays in the USAAF and US military in general went back well before 1943. The US began experimenting with jet propulsion BEFORE the bombing of Pearl Harbor (I think it was roughly around the same time the Brits and Germans). IIRC, the Bell Airacomet first flew under jet power c.1940/41 (not entirely sure of the date there). Not particularly impressive performance, (I think the P-51 and late-model Hogs were faster) but it WAS flying. It's just that after entering the war the US focused its attention on churning out existing designs, rather than moving development on a lot of more advanced projects, focusing on winning the war with what was proven, rather than experimental uberfighters (in part why nothing was made of monsters like the Chain Lightning).

Anyway, my main point was that the USN wasn't the only branch of service guilty of not putting time into R&D (point of order: Wasn't the F6F the ONLY American fighter to begin development AFTER the US entered the war?)

Bell's XP-59A didn't fly until October 2, 1942, about 15 months before the XP-80 flew. Their YP-59A didn't flying until August of 1943, less than six months before the XP-80 flew. Moreover, it was realized that the YP-59 would never evolve into a viable fighter and were designated as advanced trainers as were the 100 P-59As built and delivered during 1944.

Work began on the XF6F-1 prior to the Pearl Harbor attack, with an order for the prototype being issued on June 30, 1941. I think that the only US fighter that comes close to being designed, developed, built and flown in combat during the US portion of the war was the P-63, which evolved out of the P-39E contract (placed on June 27 of '41) which ended up being cancelled in favor of Bell's XP-63 proposal.

My regards,

Widewing

[F4UDOA]

Justin,

Yeah, I meant the pre-ADI models.I would like to find the BuAer July 1943 document. I have the Vought and British test that are closer to the AAF test

The F4U-1A in that test is slightly heavier and hense the climb is not good at all. It is faster than the older -1's tested I assume because of the drag condition.

[whels]

Originally posted by justin_g
Btw, just for laughs - who would like a 377mph Mustang I in mid '43?



377MPH AT SEA LEVEL THAT IS!

or a Mustang III aka P51B (british modified) used to chase V1s, would do
450mph @ 5k imagine the La7 pilot whines  of being run down lol.