The Douglas F3D Skyknight

v1.0.1 / 01 sep 02 / greg goebel / public domain

* The Douglas Skyknight was one of the first purpose-built jet night fighters, which served with distinction in the Korean War and survived to put in useful service in the Vietnam War as well. This document provides a short history of the Skyknight.

[2] F3D-1 / F3D-2 / KOREA


* In 1945, the US Navy began studies for a jet-powered carrier-based night fighter, resulting in issue of a request specifying a two-seat aircraft with long range radar and good performance. Douglas, Grumman, Curtiss, and Fleetwings submitted proposals, with Douglas awarded a contract on 3 April 1946 for delivery of three prototypes with the designation "XF3D-1 Skyknight".

Development was conducted by a team under the well-known Ed Heinemann at the Douglas division in El Segundo, California. The first prototype XF3D-1 made its initial flight on 23 March 1948, with test pilot Russell Thaw at the controls. All three prototypes were sent to Edwards Air Force Base in October 1948 for service trials.

The Air Force was interested in the Skyknight for a time, as the Northrop "F-89 Scorpion" all-weather interceptor was suffering from development problems, but the USAF decided to acquire the Lockheed "F-94 Starfire" interceptor as an interim solution until the Scorpion's bugs were worked out.

The Skyknight was of simple configuration, with a mid-mounted straight wings that folded straight up from the midsection, a conventional tail arrangement, tricycle landing gear with the main gear retracting outward into the wings, and a stinger-type arresting hook. A skid with a tiny wheel on the end was mounted in front of the arresting hook, and could be extended to protect the aircraft from bumping its tail on takeoffs and landings. A hydraulically operated air brake was mounted on each side of the fuselage behind the wings.

The Skyknight was powered by twin Westinghouse J34-WE-22s with 1,360 kilograms (3,000 pounds) thrust each, fitted in nacelles mounted low on the fuselage below the wings. The engines could be easily accessed for maintenance, and dropping them out for replacement was a simple procedure. The F3D-1 was armed with four 20 millimeter cannon mounted in the underside of the nose, with 200 rounds per gun. Internal fuel capacity was 5,116 liters (1,350 US gallons). A 568 liter (150 US gallon) external tank or a 450 kilogram (1,000 pound) bomb could be carried under each wing.

The pilot and radar operator sat in a side-by-side configuration. The ejection seats available at the time could not work safely with such a seating arrangement, and an unusual escape mechanism was designed involving a chute in the floor behind the flight crew. Pulling a lever would blow off the rear half of the chute exit hatch in the belly between the engines, with the front half serving as a windbreak. Each crew member would then pivot around in his seat, grab a vaulting bar behind the seat, kick open a cockpit exit door, and slide out the chute feet-first, one crew member at a time.

Westinghouse AN/APQ-35 radar system was fitted in the nose. The first two prototypes had been fitted with the older SCR-720 radar as the AN/APQ-35 hadn't been available at the time. The AN/APQ-35 actually consisted of two radars, including the AN/APS-21 search radar that could locate fighter-size targets at a range of 32 kilometers (20 miles), and the AN/APS-26 targeting radar, with a range of 3.2 kilometers (2 miles). The AN/APS-21 could be used to locate a target, pass it over to the AN/APS-26 at close range for target tracking, and continue to scan for new targets. It was one of the first "track while scan" radar systems ever developed.

The prototype evaluation was successful, and led to an initial production order for 28 F3D-1 Skyknights in June 1948. The first production F3D-1 flew on 13 February 1950, and the type went into operational service with the Navy VC-3 Squadron at Moffett Field, California, in December 1950.


[2] F3D-1 / F3D-2 / KOREA

* The F3D-1's airframe was similar to that of the XF3D-1, but it was fitted with a stronger tail bumper wheel, and fully operational electronic systems that increased the takeoff weight by over two tonnes. It also featured uprated Westinghouse J34-WE-34 engines with 1,475 kilograms (3,250 pounds) thrust each, with the new engines requiring larger nacelles. A few early production F3D-1s were not fitted with the uprated powerplants due to engines availability problems.

The F3D-1 was still definitely underpowered, and only the initial batch of 28 were produced. The F3D-1s remained stateside and were used for training flight crew for the definitive Skyknight variant, the F3D-2.

The F3D-2 was ordered in August 1949. The F3D-2 was originally planned to be powered by twin Westinghouse J46-WE-3 turbojets with 2,090 kilograms (4,600 pounds) thrust each. Unfortunately, development of the J46 proved troublesome, and so the F3D-2 was completed with still further uprated J34-WE-36/36A turbojets with 1,540 kilograms (3,400 pounds) thrust each, less powerful than the J46s but still an improvement.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                15.24 meters        50 feet
   length                  13.87 meters        45 feet 6 inches
   height                  4.9 meters          16 feet 1 inch

   empty weight            8,240 kilograms     18,160 pounds
   max loaded weight       12,180 kilograms    28,850 pounds

   maximum speed           910 KPH             565 MPH / 490 KT
   service ceiling         11,650 meters       38,200 feet
   range                   1,930 kilometers    1,200 MI / 1,040 NMI
   _____________________   _________________   _______________________

The first F3D-2 flew on 14 February 1951. The F3D-2's most visible external difference from the F3D-1 was larger engine air intakes, provided to allow greater airflow for the planned J46 turbojets. A spoiler system was added to permit tighter turns and a higher roll rate, and an AN/APS-28 tail-warning radar was also fitted. This was a relatively sophisticated sensor, with a range of 6.5 kilometers (4 miles) and the ability to give range, azimuth, and elevation information. Other improvements included a General Electric G-3 autopilot, thicker windscreen armor glass, and more effective air conditioning.

* A total of 237 F3D-2s were built, with the last produced in March 1952. The Skyknight served with a number of US Navy and Marine squadrons, generally off of land bases. It was nicknamed "Willie the Whale" for its less than sleek appearance. Marine Squadron VMF(N)-513 was sent to Kunsan, Korea, with their Skyknights in the spring of 1952, where the type served with distinction.

The USAF had operated Boeing B-29 Superfortresses on daylight raids over enemy territory early in the war, but suffered excessive losses to North Korean MiG-15s, and so the bombers switched to night attacks. However, by late 1951, the enemy had refined their ability to direct MiG-15s against the Superfortresses using ground radar control, and losses began to rise again.

USAF F-94B Starfire night fighters were put into service to protect the bombers, but for various reasons they did not prove satisfactory in this role. Marine Skyknights were pressed into service as night escorts instead and performed the mission very well.

While the SkyKnight was not as aerodynamically advanced as the sleek MiG-15 and did not have an excess of engine thrust by any means, its radar system was extremely advanced for the day, its four cannon packed a hefty punch, and it could easily out-turn a MiG-15 whose pilot was foolish enough to get into a turning contest.

On the night of 2 November 1952, a Skyknight piloted by Marine Major William Stratton, accompanied by radar operator Master Sergeant Hans Hoagland, shot down what they reported from the exhaust pattern to be a Yak-15 fighter, though the type was not known to be operated by the North Koreans. The kill was confirmed as the Skyknight flew through the wreckage of the target, narrowly evading damage. This was the first night kill of a jet by another jet.

Five days later, on 7 November, another Skyknight under the command of Marine Captain O.R. Davis with radar operator Warrant Officer D.F. "Ding" Fessler shot down a MiG-15.

On 10 December 1952, a Skyknight piloted by Marine Lieutenant Joseph Corvi with radar operator Sergeant Dan George spotted a "bogey" on radar. They could not establish visual contact, but as no "friendlies" were supposed to be in the area, they fired on the target. A kill was confirmed when Sergeant George spotted a wing tumbling past them. This was one of the first times when an aircraft destroyed an enemy that the crew could not see. It turned out to be one of the little Po-2 biplanes used by the North Koreans to harass UN forces at night. The Po-2 was a difficult target, since it flew low and slow and its mostly wooden construction did not show up well on radar.

The Marine Skyknights claimed a total of at least six kills, most of them MiG-15s, and no B-29s under their escort were lost to enemy fighters. Two Skyknights were lost in combat for unknown reasons.



* An F3D-3 with swept wings and J46 engines was planned, with a contract placed for a large number of aircraft. Unfortunately, the delays in the J46 program meant that the J34 engine would have to be used, and studies demonstrated that with J34 engines the F3D-3 would show little performance improvement over the F3D-2. The order was cancelled in early 1952. There was no further new production of Skyknights.

The Skyknight was clearly a first-generation jet fighter, and as such was quickly pulled out of first-line service after the Korean War, to be replaced by more sophisticated aircraft such as the Douglas F4D Skyray. However, the type was updated and converted to special uses:

* In 1962, the US military consolidated their aircraft designation schemes, and Skyknight variants still in operation were redesignated as follows:

   F3D-1:    F-10A
   F3D-1M:   MF-10A
   F3D-2:    F-10B
   F3D-2Q:   EF-10B
   F3D-2T2:  TF-10B
In 1965, the US began to ramp up the air war against North Vietnam, and the US military found itself short of countermeasures aircraft to protect strike packages. The EF-10B was one of the few assets available, and in April 1965 a handful of them were sent to Da Nang airbase in South Vietnam to support both US Navy and Air Force raids over North Vietnam.

There were never more than about ten EF-10Bs available, and they were sent on numerous "Fogbound" missions, pinning down the locations of enemy radar stations and passing off their coordinates for attack by defense-suppression aircraft, or blinding the radars with chaff and electronic jammers. Despite their age, the EF-10Bs were very effective, and they were heavily tasked well into 1966. By late 1966, "RB-66 Destroyers" were taking over the countermeasures role for the Air Force, and the "EKA-3B Skywarrior" and later the "EA-6A Prowler" took over countermeasures for the Navy.

The Marine EF-10Bs nonetheless flew in Vietnam until 1969. The type was finally removed from operational service in 1970.

A number of TF-10Bs were used as test and trials platforms into the early 1980s. These aircraft were the victims of bizarre Frankenstein modifications, with noses of other aircraft such as the Skyhawk grafted on to perform tests of radar systems. No Skyknights are now in flying condition, though a number are in static display in museums and US military bases.



* Despite the fact that most sources speak highly of the Skyknight, one US Marine familiar with the aircraft from his Vietnam days said on an Internet bulletin board that it was known as the "Drut", a term whose meaning can be deciphered by reading it backwards.

Although the lack of ejection seats probably did not make flight crews happy and the low-slung engines were an invitation to foreign object damage, it seems plausible that this unaffectionate nickname was awarded less for any inherent defect in the aircraft than for the fact that by the mid-1960s the type was antiquated, underpowered, and likely decrepit. The Marines are the last priority for defense procurement, and as a result they make a habit of hanging on to weapons that the other services would have thrown away long before.

* All my aviation documents are written from secondary sources, and while this is adequate to give a fairly clear description of an aircraft, there's generally a few contradictions and fuzzy points.

In the case of the Skyknight, descriptions of the AN/APQ-35 radar system are confusing and contrary, particularly since it actually consisted of two separate radars, the AN/APS-21 and AN/APS-26, working in conjunction, and only one document actually made a specific connection between them all. Range figures are particularly baffling, since most sources say that the AN/APQ-35 had a range of 125 miles, while more detailed sources say that the AN/APS-21 search radar component had a range of 20 miles.

Admittedly, the operation of RF systems like radar is strongly dependent on everything from the phase of the Moon to the operator's digestion, but it still seems that somebody slipped a digit someplace. 125 miles seems like a long range for a fighter radar of that period, particularly since the F-94 Starfire's radar had a range of 20 miles, and 125 miles and is well in excess of the range of the latest radars being developed for the F-16. I decided to be conservative and have used the 20 mile figure here.

By the way, the name "SkyKnight" is very commonly misspelled as "SkyNight", and in fact I think I found more references to "SkyNight" than "SkyKnight" when I did a search for the type on the Web. I was surprised to see that Dr. Rene Francillon, one of the finest aviation writers around, made this booboo. Even the best of us screw up sometimes.

* Sources include:

A very thorough website document on the Skyknight by aviation enthusiast Joe Baugher was also consulted for additional details.

* Revision history:

   v1.0   / gvg / 01 feb 01
   v1.0.1 / gvg / 01 sep 02 / Minor cosmetic update.