F4U-4 vs YaK-9U

[kool kitty89]

For the F4U-1

F4U Performance Trials


F4U-4
http://www.wwiiaircraftperformance.org/f4u/f4u-4.pdf

And the 2,250 hp figure was for the F4U-1D iirc (or w/out water injection), the F4U-4 had 2,450 with water injection.

Soren's 2,800 hp fig is for the R-2800-57 of the P-47M/N (and XP-47J) not used on the F4U.

[renrich]

KK, good tech stuff in your post. However 14000 pounds for a F4U4 is pretty high. A combat load would be 12420. That would be full internal tank of 1404 pounds, 720 pounds of ammo, basic wgt. is 10076, the rest is water/alcohol, oil. Fighter with one external tank would be 13350 pounds.

[kool kitty89]

Yeah, but the top speed chart in that PDF of the repot seems low. (as does the cret alt, which should be ~24,000 ft)

I think the 14,000 lb weight is full internal load clean configuration, which is more than normal combat config.

[renrich]

KK, the critical altitude for F4U4 at military power is about 27500 with a TAS of 425 mph. The CA at combat power is about 25500 with a TAS of almost 450 MPH. The bomber wgt. with 1000 pound bomb and 2 external tanks is 14515.Bomber with 2000 pound bomb and one external tank is 14412. All info from "America's Hundred Thousand," by Dean. The author's sources are given as Navair bulletins and manufacturer data.

[claidemore]

Like the F4U-4, the Yak 9U also had two different weapon choices, the 20mm ShVAK + 2 x 12.7mm UB or the NS-37mm cannon +2 x 12.7mm UB (Yak 9UT, 282 produced).

The modern Yak 9U-M, with Allison V1710 is listed as doing 434 mph. Thats 1500 hp and the VK-107A was 1650 (takeoff) 1500 normal, so pretty much the same. Some sources state 700kmh for Yak 9U (437mph), others show 672 (420mph).

Climb rate was 5 min to 5000 meters(16400 ft), or 3280 ft/min. Thats a wee bit better than the F4U4's time to 16,000 ft of 5 min at normal power and a wee bit less than the F4U4 time to 16k at Military power. About equal in the climb department.

According the the charts from Chance Vought, dated 1947, the highest speed I can see is 394 mph @ Combat power. Don't know much about Corsairs, and maybe I'm missing something, but thats what that chart says.

F4U Performance Trials

[FLYBOYJ]

The new Yak 9s must also weight way less - just think about the radios.....

[kool kitty89]

renrich, then the speed charts are even further off, look at the PDF.
Same for the power ratings. (they seem to be for the F4U-1A, but other pars seem the -4 it's weird)


Wait, it's knots not mph... oops


And the maybe the engine ratings on the 1st page are at low blower, or maybe intermediate, that would make more sense, granted only normal and MIL power listed not WEP or with water injection. (the F4U had 3 blower settings, first the integral single stage single speed one, then add the engage the aux supercharger stage at low speed, then 3rd the aux at high speed)


And the document shows a top speed of ~450 mph at ~20,500 ft, and a max climb of ~4,800 ft/min from SL to ~11,000 ft. (according to the charts)

In the notes, Vmax is listed as 403 kts (463 mph) at 20,600 ft. in clean configuration.

[claidemore]

Originally Posted by FLYBOYJ

The new Yak 9s must also weight way less - just think about the radios.....

True, empty weight original was 5526, modern is 5000, so lighter radios/avionics and no guns?

Propeller is different on modern Yaks as well, not sure what effect it has.

Of course, the 'old' Yak 9U speeds are still listed as somewhere between 420 and 437 regardless of the performance of the modern ones. I would tend to go with the 420 figure for the 9U, as the 437 lines up with the Yak3 with VK 107 engine. But that's just a logical guesstimate. lol

Interesting that the climb rates are apparently so similar on these two planes. The Soviets considered the Yak a much faster climbing plane than the FW 190, and in the tests of FW190 vs F4U-1 the 190 outclimbed it. I wish we had a nice graph with the Yak climb rates like we do for the F4U-4.

I ended up voting for the Yak in any case.

In the words of German fighter ace Gerhard Barkhorn (301 victories) " I fought against all types of Soviet fighter, including those supplied under Lend-Lease (spitfire, hurricane, P-40, P-39, P-51), and the Yak-9 was the best".

[claidemore]

Ahhh, the dreaded knots! No wonder. Duh.

[KrazyKraut]

I never heard of Soviet lend-lease Mustangs, though.

I vote F4U, though it's kind of odd to rate the two against each other.

[JoeB]

Originally Posted by KrazyKraut

I never heard of Soviet lend-lease Mustangs, though.

Only 4 actual Lend Lease Mustangs (Allison Mustang I's via the Brits) plus some USAAF P-51's left behind in the 'shuttle raids' to and from Ukranian bases, and tested by the Soviets. The former were evaluated in an operational unit in '42 but disliked and not used in combat, per "Red Stars Vol 4" by Guest and Petrov.

However, the Germans, and Finns, apparently mistakenly thought they encountered Mustangs in Soviet hands in some cases. And USAAF P-51's, on shuttle raids or 15th AF a/c from Italy, were being encountered by German units nominally in the 'East' by mid 1944.

Joe

[Kruska]

claidemore; Like the F4U-4, the Yak 9U also had two different weapon choices, the 20mm ShVAK + 2 x 12.7mm UB or the NS-37mm cannon +2 x 12.7mm UB (Yak 9UT, 282 produced).

Hello claidemore,

I voted for the F4U-4 for being the overall much better a/c.

The data I have regarding the armament of the Jak9 differs from your post. I am not aware of a Jak-9UT with a 37mm plus two 12.7mm. From which source did you retrieve your info? I am not saying that this would not be correct, but I have no info on this.

Jak-9UT: 37 mm Nudelman-Suranov Canon and two 20 mm Berezin Cannon
Yak-9T: with one Nudelman-Suranov 37mm-Cannon and mountings for 5.5 pound bomblets
Jak-9U: one 23-mm-Cannon WJa-23 and two synchronized Beresin 12.7-mm-MG’s plus mountings for 2 x 100kg bombs.
Jak-9P: only one 23-mm WJa-23
Jak-9K: with 45 mm Cannon
Jak-9P: one 20mm ShVAK Cannon
Jak-9: one 20mm Cannon and two 12.7mm
Jak-9D: one 20mm Cannon and one 12.7mm
Jak-9TD: one 37mm Cannon and mountings for 4 x 50kg bombs
Jak-9B: 4 vertical pipes behind cockpit with 100kg bombs each or 3.3 pound bomblets

Regards
Kruska

[renrich]

KK, I don't believe 463 mph for F4U4. Every good reference I have including Boone Guyton's (the test pilot for Vought) says 446 mph. Perhaps a specially prepared AC could go faster. The 463mph could be the F4U5 as I have seen 465-470 quoted for it as it had a different engine and supercharger set up than the 4. The Corsairs had a two speed two stage supercharger. The first stage compressed the fuel air mixture and worked whenever the engine turned over and was called neutral blower. It sufficed for takeoff and low altitude operation. The second stage had to be manually switched on by the the pilot, compressed the air going from the outside to the carburetor after going through an intercooler and had two speeds. Low blower was used from about 5000 feet to 18000 feet. High blower was used from 18000 feet up. Thus the charge air was compressed by two blowers, one ahead of the carb and one after it. It seems odd to me that the pilot in a Corsair had to manually switch modes when , for instance, in the Merlin Mustangs, the switching was all automatic. My suspicion is that the Navy was all into reliability and did not want to risk any auto stuff. Kind of like if I am on a serious 4-wheel drive trail, I want to be able to grab a lever and manually shift the tranny into low range, not push a button or have it be automatic.

[HoHun]

Hi Renrich,

>KK, I don't believe 463 mph for F4U4.

Maybe these datasheets are of interest:

Untitled Document

Maximum speed for the F4U-4 is given as 728 km/h @ 6250 m, which is slightly short of 463 mph. However, it appears that the presence of "two capped pylons" lowered the speed a bit below the maximum for a clean airframe.

Regards,

Henning (HoHun)

[Soren]

KK,

The F4U's wing doesn't achieve nearly as high a Clmax as the FW-190's, the reason being the F4U's wing isn't as clean a design (Big LE intakes at roots and gull shape), and doesn't utilize the optimum TR's as the FW-190's wing does. (16 - 9%)

Also note that the wing root TR is actually 18%, outside the optimum.

The F4U's wing most likely has a Clmax ranging between 1.49 - 1.51, still higher than the Yak's but lower than the 190's.

Now as for wing & power-loading, there isn't the difference Bill suggests:

F4U-4
Gross weight: 12,500 lbs (5,600 kg)
Wing area: 29.17 m^2
Power: 2,450 HP
___________________
WL = 191.7 kg/m^2
PL = 2.28 kg/hp

Yak-9U
Gross weight: 3,230 kg
Wing area: 17.2 m^2
Power: 1,500 HP
__________________
WL = 187.7 kg/m^2
PL = 2.15 kg/hp

So the difference in wing loading amounts to 2.1%, however the F4U's higher Clmax makes up for this. Meanwhile the difference in power-loading is 6%, however I'd suspect that F4U-4 prop is more efficient.