Why did the U.S. navy reject the F6U Pirate?

It's easy to forget that the planes we are so fascinated by in World War II represented merely a snapshot in time, a frozen barely-more-than-a-moment in a period of extremely rapid technological advance. At the beginning of the war, those cool front line fighters—Bf-109s, Hurricanes, Wildcats—were almost all replacements for wood and fabric biplanes. OK, the P-40 replaced the monoplane P-36, but the P-36 was one of the very first widely-produced monoplanes, with its first deliveries to an operational unit happening in 1938, replacing the biplane P-26 "Peashooter." Meanwhile, the F4F Wildcat itself started out on the drawing board as a biplane, gradually morphing into a monoplane as Grumman worked on it.

At the other end of the war, a blink of an eye later, we see jets beginning to take over, with the Me-262 flying in actual combat while the P-59 and P-80 were in the air, the one not quite capable enough to make it to the front lines, and the other destined to become a front line fighter, but not quite in time for the war. And late in 1944 the U.S. navy put out a request for a proposal for a jet fighter. And here is where it gets interesting, with questions raised to which I don't know the answer, and am wondering if somebody out there does.

Vought replied to the September 1944 solicitation (one month before the Battle of Leyte Gulf) with the F6U Pirate. The navy expressed interest, and the first XF6U prototype flew on October 2, 1946. But the Pirate was greeted with disappointment. According to Wikipedia:

"The judgment from the evaluation was that the Pirate was unacceptable for operational use. Naval aviators disparagingly called the F6U the 'groundhog.' On 30 October 1950, BuAer informed Vought of the Navy's opinion of the Pirate in terms both bureaucratic and scathing: 'The F6U-1 had proven so sub-marginal in performance that combat utilization is not feasible.'"

Pretty harsh words for a plane that could fly close to 600 mph and. . .well, here are the specifications (undoubtedly based on the most-developed version):

maximum speed: 596 mph
rate of climb: 8,060 fpm
service ceiling: 46,260 feet

So the navy passed on the Pirate. But shortly thereafter they decided to accept the Grumman F9F Panther (the prototype of which first flew more than a year after the first Pirate flight) and eventually they made it their primary carrier-based fighter. That might lead one to think that the Panther had better performance than the unacceptable Pirate. However, here are the specs side by side:




So, did the navy go with the Grumman product simply because the navy had a "special relationship" with Grumman, or was it something else? Clearly it wasn't about the numbers, so what was it? Is there anybody out there who can shed some light on this matter for me?

The aircraft were completed at Hensley field and in flight test, it was found that the 5200 foot runway was barely adequate to get them airborne.....Should tell you about their performance level. They would never be carrier capable.

I think there is a major typo in the climb figure for the Pirate. That or the plane was running nearly on fumes when the test was done.
The engine in the Pirate was rated at 4225lbs thrust in after burner (late 40s afterburners were a little on the sketchy side)
The engine the Panther (F9F-2) was rated at 5750lbs thrust, by they time they got to the F9F-5 they had engines ranging from 6250-7250lbs of thrust depending on exact model of P & W J-48 engine and water injection. NO after burner.
Jet engines were in a real state of flux in the late 40s. Many of the F9Fs were supposed to have used Allison J-33 engines of 4600-5850 lbs thrust (F9F-3 and F9F-4) but most/all were actually completed with P & W engines.

The Westinghouse J34 engine was an axial compressor engine and was about 27in in diameter.
The P&W J-42 in the F9F-2 was a licensed copy of of the RR Nene of 49.5 in diameter and the J-48 was a licensed RR Tay of 50.5 in diameter.
P&W asked RR to make a more powerful engine than the Nene and RR came up with the Tay. RR never actually made the Tay as a production engine but they did license it to Hispano-Suiza.

Quoting Boone Guyton, Vought's chief test pilot, in his Whistling Death – The Test Pilot's Story of the F4U Corsair, page 231, regarding the F6U:
"The Pirate, a small underpowered, straight-winged airplane, was Vought's first jet. They would rather forget it. Outdated, and with low performance, its singular claim could be that it was the first production aircraft equipped with an afterburner (an engine device added to increase power). It never came close to being operational and I devoted a given amount of time, during contact trips, describing its one good feature – the afterburner – with a sense that knowledgeable pilots were yawning."

I think he ought to know.

FWIW, ironically, Guyton's last flight as a Vought test pilot was in a F6U, a scheduled flight to Socorro NM which ended instead at Holloman AFB in a no power, no hydraulics landing. Guyton spends a little over six pages describing the adventure of piloting a jet with no hydraulics at idle power some 35 miles to the nearest field.

Swanborough shows F6U max speed at 20,000 feet as 564 mph.

Naval Fighters number nine by Richard Koehnen has much detail on the F6U-1. A chart in the book gives max speed @ sea level 518 knots & 429 knots @ 22000 ft. An interesting comment: "Because the runways at Vought were too short, the prototype was disassembled, wrapped and flown to Muroc in a C-82."

I guess answer to the OP question is: "The F6U-1 has proven so sub-marginal in performance that combat utilization is not feasible." -J.H. Cassdy (sic) , Deputy Chief of Naval Operations (Air).

The early USN jet fighters, in production appearance order,

McDonnell FH/FD, wing folding, twin engine, long service career,
2 prototypes ordered 30 August 1943,
100 ordered 7 March 1945, 30 more added but 70 cancelled V-J Day
60 built December 1946 to May 1948

North American FJ-1, no wing folding, short service career,
3 prototypes ordered 1 January 1945,
100 ordered 28 May 1945, contract reduced by 70 probably V-J day,
30 built October 1947 to April 1948, "service test order"

McDonnell F2H-1, wing folding, long service career,
3 prototypes ordered 2 March 1945,
30 ordered 29 April 1947, 26 more added later,
56 built, 1 acceptance in August 1948 then 55 from November 1948 to July 1949,
(F2H-2 production order for 179 on 22 April 1948, with 14 becoming the night fighter version, production started in November 1949, 17 accepted by end 1949)

Grumman F9F, wing folding, long service career,
2 F9F-2 and 1 F9F-3 prototypes ordered 22 April 1947,
30 F9F-2 and 54 F9F-3 ordered 1 July 1947, another 17 F9F-2 added later,
production started in December 1948, 54 F9F-3 to end October 1949, 99 F9F-2 to end December.
(Next production order on 23 April 1948 for 244 (plus 73 added later) F9F-2 and 100 F9F-3.)

Vought F6U, No wing folding, no service career,
3 prototypes ordered 12 October 1945,
30 ordered 26 February 1947,
production started in January 1949, 5 accepted to end November, 17 in December, remaining 8 in the first 3 months of 1950.
(The next design, the XF7U, 3 prototypes ordered 25 June 1946, the first F7U order was for 19 dated 18 June 1948, another 88 ordered 23 September 1949 were cancelled 6 December 1949)

Giving the F6U as the third prototype ordered, third ordered into production, last to be built and by the time the first F6U was accepted McDonnell and Grumman held large orders for their designs, while Vought had an F7U order.

1947 production comments, FH-1 schedule based on engine deliveries, 5 airframes awaiting engines. FJ-1 grounded on 11 December 1947 as a result of J-35 rear main accessory bearing failures. Temporary fix to protect pilot during canopy jettison approved, change request for power operated emergency canopy opening system initiated.

1948 production comments, XF6U-1 progress extremely slow, same for XF3D with "problems not readily soluble", F6U-1 three aircraft to be made at Stratford, 27 at Dallas, but all details to be made at Stratford, the contract had called for all aircraft to be accepted by end April 1949, the revised 1949 schedule had last acceptances in September.

Angellucci and Bowers F6U climb rate 4,560 feet per minute, service ceiling 40,900 feet.

Gentlemen

For your information.

Eagledad

eagledad said:

Gentlemen

For your information.

Eagledad

Click to expand...

Excellent information.
I note that it confirms that a climb rate figure of 8,000 fpm is accurate, not a typo as suggested above, but only at sea level. But it is still around 5,000 fpm at 20,000 feet, and nearly 4,000 fpm at 30,000 feet, which seems not bad at all.

OK, I was wrong.
Performance of the F6U-1 is based on calculations.
Performance of the F9F-5 in the provided document is based on NATC flight test.
Perhaps some of the different load outs were based on calculations but at least they were based on something real.

Gentlemen

No other info on the F6U.

Information on other Navy aircraft can be found at:


Eagledad