F4U-4 vs YaK-9U

[renrich]

KK, the crash landing of the XF4U happened when Boone Guyton took the AC out over the Atlantic to run some tests. Because of the speed of the Corsair he went slightly farther than planned and the weather turned bad. He was dodging thundestorms and realised he was running out of gas. He finally decided he was not going to make the field and selected a golf course to land on while he still had power. Boone was a former carrier qualified pilot and executed a full stall to approach landing just in front, if memory serves, of the tee box on a par four. Everything was fine except when he applied the brakes. The grass was wet from the rain and the plane just kept skidding. He finally skidded over the green and into a wooded ravine. The trees ripped the wings off and he wound up upside down hanging from his harness. Was rescued by a passerby. The plane did not catch on fire because the tanks were almost dry. He did not have a par on the hole. I believe it took about 6 months to rebuild the AC. I don't know if the inverted gull wing contributed to the spin characteristics or not. With my limited knowledge of aerodynamics, it seems to me that particular wing design might have an impact on longitudinal stability,(like wing dihedryl.)

 

[renrich]

During the developmental stages of the Corsair, the R2800 engine caused a lot of problems. It was new and the Corsair was one of the first to use it. Among other problems, one of the cylinders (I can't remember which one and the book is packed) kept overheating and causing engine failure. Guyton became proficient at dead stick landings. Once and I believe this was after production had begun, he just failed to make the runway, hit a dike, the plane was totaled and Boone was propelled down the runway still strapped to his seat. He barely survived and spent many months in the hospital. Guyton was 6'4" which explains some of the dimensions of the cockpit. He flew an A6M and could not close the canopy. An interesting point is that Vought spent around 700 flight test hours perfecting the ailerons on the Corsair which showed up in it's roll rate, allegedly perhaps the best of US WW2 fighters. Or course AC which used the R2800 later such as P47 and F6F benefited from Vought's experience.

 

[kool kitty89]

For Roll it was either the F4U or P-47N, inless you count the P-80.


Too bad he didn't take it in for a belly landing, still ended up better than the XP-38 though.

 

[renrich]

Why would the P47N have a good roll rate? With the extended wing span, I would think that the roll rate would be slower than the P47D. The problem with the F4U and roll rate is concerned is that my reference says that very little data exists which quantifies the roll rate of that AC. All there is to go on basically is testimony by pilots who say that it had a very high roll rate with some claiming a two second 360 degree roll at higher speeds. I rolled an L39 twice at 250 knots and the specs say it will do one second rolls. All I can say is that it rolls plenty fast!

 

[HoHun]

Hi Renrich,

>The numbers from your site look good to me as the Corsair is my favorite AC of all time but they look a little suspect.

Hm, they seem to be official BuAer numbers, and if I were BuAer, I'd have checked them before release. However, I'm not BuAer

You could try to contact F4UDOA over here: http://bbs.hitechcreations.com

He has probably seen most data anyone could dig up by perseverant and inspired internet research, and he'll probably be able to give you an accurate assessment of F4U-4 performance.

He might also be your best hope regarding reports on the Corsair's wings - I have not seen anything relating specifically to the inverted gull shape, I'm afraid.

Regards,

Henning (HoHun)

 

[JoeB]

The data I have regarding the armament of the Jak9 differs from your post. Jak-9P: one 20mm ShVAK Cannon
[/QUOTE]
There were two different 'Yak-9P' , one a prototype M-105PF powered a/c during WWII and one the postwar production model, essentially an all-metal Yak-9U, VK-107A powered. The former type per most sources had 2*20mm, but the latter type is the one of interest here since the postwar metal Yak-9P was the only Yak-9 to actually meet F4U-4's in combat, and was again essentially the same a/c as the Yak-9U besides having metal wings.

The armament of the postwar all-metal Yak-9P VK-107 was 1*20mm ShVAK and 2*12.7mm UBS. Captured North Korean documents list the type and serial numbers for the weapons in various individual Yak-9P's in inventory just before the Korean War, so that armament is about 100% certain. It's not 100% certain that the Yak's met later by the F4U's (April 1951) were also 9P's but it's highly likely IMO.

Also, most sources say production Yak-9U's had that same armament, for example Gordon "Yakolev's Piston Engine Fighters", though the prototype had 23mm.

Joe

 

[Kruska]

Hello JoeB,

That is some good and interesting info, thanks.

Regards
Kruska

 

[kool kitty89]

Well firstly the increase in span of the N over the normal P-47 wing was only 40 feet 9 3/8 inches standard to 42 ft 7 in for the N's wing.

But there's a wole lot more to the story:

Seversky Aircraft and Republic Aviation

Fortunately, Republic had been paying attention to developments with the P-51 and were hard at work on a long range Thunderbolt as early as November of 1943. The same P-47C-5-RE that had been used as development mule for the Pratt Whitney R-2800 C series was fitted with 27 inch long extension inserts in each wing. This was done largely to test the handling of the aircraft. No provision was made to carry any additional fuel in the wings. These tests revealed that the roll rate had suffered and the wings were clipped at the tips and a squared off cap was fitted.






This is the only existing photo of the "unofficial" XP-47M test mule. After being used as a testbed for the Pratt Whitney R-2800 C series engine, it was fitted with 27 inch long wing extensions (at the wing root), and used to test the flight characteristics of the modified wing. When the request for a long range Thunderbolt came along, this fighter was wheeled out, dusted off and presented to the Air Material Command. The photo shows the fighter prior to receiving the modified wing.

In May of 1944, an Expenditure Order was issued and $101,000 was allocated to Republic to develop a "wet" wing to be installed on one of the three YP-47M prototypes. Within 30 days Republic was able to present a test report based upon their earlier testing, along with a full set of drawings as a proposal to the Air Material Command. The new drawings illustrated the new wing design. The inserts were now just 18 inches in length, and contained an integral fuel tank for 100 gallons of fuel. In the contract, the #3 YP-47M was specified as the test aircraft (S/N 42-27387). Twenty hours of flight time were expected after the new wing had been installed. In July, the fighter was officially designated as the XP-47N and the unofficial test mule was re-designated as a P-47C-5-RE once again. The final disposition of the test mule is unknown. It did, however, retain its new wings and the more powerful C series engine for as long as the aircraft appeared on the company inventory.

The modifications to the existing YP-47M were considerable. Aside from simply installing the wing inserts and fuel tanks, the flaps were required to be redesigned, and the ailerons had to be modified to fit with the new squared-off wing tips. Due to spacing the wings out from the wing root, the landing gear track increased by more than 3 feet. The overall wing span had increased to just over 42 ft 6 inches. The empty weight of the fighter had gone up by nearly half a ton to 12,950 lbs.





This wonderful view of the XP-47N shows its new wing planform to great effect. The squared-off wing tips makes P-47N indentification easy. Note that the Prototype fighter does not yet have the dorsal fillet installed.

The XP-47N took to the air for the first time on July 22, 1944. Test comparisons were made with a P-47D-30-RE throughout the early portion of the evaluation period. Much to everyone's surprise, the XP-47N, with its greater wingspan and higher weight actually proved to have better roll performance than the D model. At 250 mph TAS, the N attained a maximum roll rate just over 100 degrees/second. The P-47D-30-RE could manage but 85 degrees/second at the same speed. At higher speeds, the N widened the gap further. In mock combat with a P-47D-25-RE, the new fighter proved to be notably superior in every category of performance. In short, the XP-47 waxed the venerable D model regardless of who was piloting the older fighter. The new wing was part of this newfound dogfighting ability, however, the more powerful C series engine played a role too. The additional horsepower allowed the N to retain its energy better than the older Thunderbolt.

And against the F4U-4:

Chance Vought F4U-4 Corsair

The F4U also rolled well. When rolling in conjunction with powerplant torque, in other words, rolling left, it was among the very fastest rolling fighters of the war. In the inventory of American fighters, only the P-47N rolled faster, and only by 6 degrees/second.

 

[FLYBOYJ]

There were two different 'Yak-9P' , one a prototype M-105PF powered a/c during WWII and one the postwar production model, essentially an all-metal Yak-9U, VK-107A powered. The former type per most sources had 2*20mm, but the latter type is the one of interest here since the postwar metal Yak-9P was the only Yak-9 to actually meet F4U-4's in combat, and was again essentially the same a/c as the Yak-9U besides having metal wings.

The armament of the postwar all-metal Yak-9P VK-107 was 1*20mm ShVAK and 2*12.7mm UBS. Captured North Korean documents list the type and serial numbers for the weapons in various individual Yak-9P's in inventory just before the Korean War, so that armament is about 100% certain. It's not 100% certain that the Yak's met later by the F4U's (April 1951) were also 9P's but it's highly likely IMO.

Also, most sources say production Yak-9U's had that same armament, for example Gordon "Yakolev's Piston Engine Fighters", though the prototype had 23mm.

Joe

If I remember a post war production model that was captured during the Korean War was sitting in a museum on the east cost somewhere....

 

[kool kitty89]

Also note that removing the wing tanks from the Corsair (present on all F4U-1's iirc) increased its roll rate. As did the continual aileron improvements.


And the higher speed figure should be for the F4U-5 with the reduced drag at high speed due to the all metal construction.


iirc the F4U-1 used wooden (high strength plywood) ailerons, flaps and elevators, and a fabric covered rudder. (along with the fabric covered outer wing pannels)

I don't know if the control surfaces changed changed in the F4U-4 though (the F4U-5 being all metal of course). But the wooden surfaces should work as well as metal covered ones. (both free of the deforming problems of fabric)

 

[JoeB]

If I remember a post war production model that was captured during the Korean War was sitting in a museum on the east cost somewhere....

A Yak-9P was captured by the Marines at Kimpo a/f during the Inchon campaign in September 1950, shipped back to the US for study (at Cornell) and a later flight test program (of around 23 hrs in 16 flights) at Wright-Patterson AFB. AFAIK though it was junked in the late '50's, unfortunately. Other Yak-9P's still exist in former east bloc countries though and one is a prominent display in the 'Victorious Fatherland Liberation War Museum' in Pyongyang.

Joe

 

[Soren]

KK,

Regarding the F4U-4's control surfaces, I'm fairly certain they're all metal.

Also the F4U-4 was or could be equipped with ailerons boosters IIRC.

 

[kool kitty89]

Ok so the only fabric left was on the wings then. And no wood. (even the flaps) ?

 

[Graeme]

AFAIK though it was junked in the late '50's, unfortunately.

North Korean Yak-9P, thought to be manufactured at State Factory No. 286 at Kamensk-Uralsk. Captured, as you mentioned, and given a USAF serial. T2-3002. Books of the late 60s and early 70s vintage, illustrate this photo describing it as "on display at the USAF Museum at the Wright-Patterson Air Force Base".

 

[FLYBOYJ]

Ok so the only fabric left was on the wings then. And no wood. (even the flaps) ?

I believe the trim tabs were made of wood up to the -5 models - we had this conversation previously.

 

[renrich]

Thanks, KK, good info.

 

[JoeB]

North Korean Yak-9P, thought to be manufactured at State Factory No. 286 at Kamensk-Uralsk. Captured, as you mentioned, and given a USAF serial. T2-3002. Books of the late 60s and early 70s vintage, illustrate this photo describing it as "on display at the USAF Museum at the Wright-Patterson Air Force Base".

I read it was disposed of in 1958 (someone on web quoting a book), but the USAF Museum doesn't have it now or any time in the last 20 years or so at least. A number of Russian sources say the Yak-9P was only produced at Factory 153 in Novosibirsk. I would like to review the original evaluations of the captured one, see if and why they concluded otherwise, haven't gotten around to that. The tail numbers of NK a/c were apparently a simple sequence based on when the a/c arrived from the Soviet Union, so this as single digit was one of the earlier ones. If as appears it's 9, it was already on inventory in February 1950 with the 1st Bn of the Fighter Regiment. Many of the initial OOB of Yak-9P's were received only from March 1950. A smaller number of 1944 production Yak-9M's left behind by Soviet occupation units leaving NK ca. 1948 were also still on hand just before the war (they had their own separate tail no. sequence).

A less often seen photo of the same plane as captured:

Joe

 

[renrich]

I saw a Yak at some air races. Not sure which model but seems like it had a radial engine. I have a photo but it is packed somewhere. He was in the Gold (unlimited) class. He had an engine problem and did not get off the ground. I believe that "Dago Red" won the race.

 

[Marcel]

I saw a Yak at some air races. Not sure which model but seems like it had a radial engine. I have a photo but it is packed somewhere. He was in the Gold (unlimited) class. He had an engine problem and did not get off the ground. I believe that "Dago Red" won the race.

Probably a Yak11?
http://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Jak_11_D-FYAK.jpg/300px-Jak_11_D-FYAK.jpg

 

[Marcel]

I saw a Yak at some air races. Not sure which model but seems like it had a radial engine. I have a photo but it is packed somewhere. He was in the Gold (unlimited) class. He had an engine problem and did not get off the ground. I believe that "Dago Red" won the race.

Probably a Yak11?