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Vought XF8U-3 Crusader III

1958 COLD WAR X-PLANE

History

The XF8U-3 "Crusader III" was a prototype series of Chance Vought Mach 2 designed to fulfill the role of an all-weather supersonic interceptor for fleet defense, eventually adopted by the famous McDonnell Douglas F-4 as the "" Phantom II". The Crusader III attempted to continue the pedigree of the original F-8 Crusader from 1957, which was eventually adopted by the U.S. Navy and Marine Corps. The Crusaders marked the end of "gun fighter" jets -- the era when American fighter jets consisted only of guns -- as the Navy wanted to use missile-guided aircraft for future defenses. The Crusader III retains some of the recognizable lines of the original F-8 design, but is sure to be an aircraft with an all-new shape, with little in common between the intended successor and the original.

However, the U.S. Navy decided to take a different route than the Crusader III shown, and only five prototypes were eventually completed.

The original F-8 Crusader was later known as "Crusader I" with the arrival of the F8U-2 (F-8C). The F8U-2 later became the "Crusader II" with 2 artillery armament, a J57-P-16 engine with 16,900 lb thrust and an elongated fuselage. The Type II accounted for 187 of the 1,219 Crusaders produced.

With the arrival of the XF8U-3, the Crusader III name was added to the series - first unofficially, then officially.

Early work on Crusader III led to an improved design of the original Vought product. The resulting design was dubbed the "V-401" model by company engineers. The basic Crusader design shape was checked, while a pointed cone component was added. The wings can be rotated at different angles of approach -- called variable-incidence wings -- just like on the F-8. A large ventral band (fin) is added below the tail, and the entrance below the nose has a sharp front lower lip.

The ventral struts are too long for the plane to land or take off, so they are designed to fold flat to provide the required ground clearance. The engine of choice became a single Pratt & Whitney J75-P-5A turbojet, delivering 16,500 pounds of dry thrust and up to 29,500 pounds of afterburner thrust.

Like the original F-8, the Crusader III (the XF8U-3 prototype's serial number) is a traditional inline fighter design with a forward-facing, single-seat cockpit and single-engine setup. The tail is covered by a vertical fin, and the main aircraft is mounted high along the fuselage spine.

The XF8U-3 has several technical features that help it perform as intended. These include radar systems and computer support for fire control. Radar can track multiple targets and engage at least two of them.

The proposed weapon is to retain the original 4 x 20mm gun arrangement but introduce wider support for the AIM-7 Sparrow medium-range radar-guided missile and the AIM-9 Sidewinder short-range missile. The plane will carry them to its seven hardpoints.

Thrust support is also suggested, envisioning an additional 8,000 pounds of thrust by installing Rocketdyne rocket engines for short bursts of extreme speed - helping to reach the target area in a short period of time - although this is an optimistic measure considering the XF8U - 3s conventional airframe design and construction.

Thus, the XF8U-3 prototype flew for the first time on June 2, 1958. In the U.S. Navy's competition with the MacDonald F-4 prototype, the Crusaders demonstrated some key qualities, including speed and control. At least three of the five completed XF8U-3 prototypes flew during testing.

The aircraft that eventually became the Phantom II was chosen before Vought's submission because it offered greater payload capacity and included a second crew member to operate the radar system. Thus, work on the XF8U-3 was completed with the completion of five airframes.

These were then handed over to NASA for high-altitude testing until the airframe was dismantled and destroyed.

During testing, the XF8U-3 had a top speed of Mach 2.39 at 50,000 feet. The stated service ceiling is 65,000 feet, but testing has shown a higher ceiling at 76,000 feet so NASA is interested in the plane.

Cruising speed is about 575 miles per hour and climb rate is close to 32,500 feet per minute. The ferry has a range of 2,045 miles, with an estimated operational range of about 645 miles. Dimensions include a length of 58 feet 8 inches, a height of 16 feet 4 inches and a wingspan of 40 feet.

By comparison, the F-4E Phantom II model has a top speed of Mach 2.23 and a cruising speed in the 585 mph range. The ferry has a range of 1,615 miles and a combat radius of 420 miles. The climb rate is 41,300 feet per minute.

The Model E can also carry a combat payload of 18,650 pounds, including air-to-air missiles as well as air-to-surface missiles and conventionally thrown weapons. Focused on artillery and missiles, the XF8U-3 was only intended to be used as a fleet defense fighter, and its artillery carrying capacity proved to be extremely limited.