FreightWaves Classics: The Fairchild XC-120 Was Ahead of Its Time
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On August 11, 1950, the Fairchild XC-120 (also known as the Pack Plane) made its first flight. Without exaggeration, it was among the most unconventional aircraft built in the United States after World War II. Built by Fairchild Aircraft for the US Air Force, the transport plane took off from the company‘s airport in Hagerstown, Maryland, for a 45-minute test flight.
The bottom of the plane
A review of the XC-120’s predecessors will help describe the XC-120. Fairchild Aircraft’s C-119 was a utility military cargo aircraft that first flew in 1947. It was the successor to Fairchild’s C-82 Packet, a military transport aircraft used during World War II to transport cargo. freight, personnel, patients and mechanized equipment. It was also used to drop cargo and troops by parachute.
Informally known as the “Flying Boxcar”, the C-119 had a large fuselage suspended from a twin-boom airframe. The first C-119 made its initial flight in November 1947, and by the time production ceased in 1955, nearly 1,200 C-119s had been built. They participated in the Korean and Vietnam Wars and served with great success in a variety of roles.
The Fairchild engineers who developed the C-119 believed there was untapped potential in the design. As described above, military transport aircraft were equipped to perform a number of missions, such as transporting personnel, transporting cargo, delivering paratroopers, and dropping large loads by parachute. Consequently, the fuselage of the plane had to have characteristics allowing the execution of all these tasks; this meant he had to carry additional weight that might not contribute to a specific mission.
This factor led Fairchild engineers to the idea that a military cargo aircraft could operate more efficiently if equipped only for the specific mission it was performing. They assumed that the best way was for an aircraft to have a specialized fuselage for each mission. Finally, their premise was that the C-119 should be the basis from which to develop such an aircraft.
The engineers’ premise led to one of the most unusual transports to ever fly – the XC-120 Pack Plane. Fairfield engineer Armand J. Thieblot developed the idea for the XC-120 (X for “experimental”; C for “cargo”). It retained the twin-boom configuration of the C-119B, but with an entirely new and significantly downsized center fuselage.
What made the aircraft so completely different from other aircraft were the “removable cargo pods that could be fitted under its fuselage and used in place of an internal cargo compartment”. The twin-engine XC-120 “was designed to serve as an airborne tractor-trailer” – with the ability to pick up and deliver pods full of cargo much faster than a traditional aircraft could load or unload.
The new fuselage had a flat bottom to which a variety of specialized cargo pods could be attached, depending on the mission. For example, cargo pods could be configured to deliver troops or heavy equipment by parachute. Other modules could “serve as portable hospitals, radar stations, command centers or perform other specialized functions”.
Because the XC-120 was intended for deployment at forward landing grounds, it would be able to quickly detach its pod and take off again. This greatly reduced the aircraft’s ground time – when another aircraft was most vulnerable as it had to be unloaded or loaded. With the XC-120, he could land, detach a pod, take off while forward ground personnel began unloading the pod. While unloading the pod, the Pack Plane could make another trip to pick up a new pod. After the XC-120 returned to the forward location, it would drop off a new pod and return to its home base with the first container, now empty.
A key change was the replacement of the C-119’s tricycle landing gear with a very different four-wheel landing gear, with all four components integrated into the twin booms. This meant that the ground clearance of the XC-120 could be adjusted by raising or lowering the height of the landing gear. This allowed the aircraft to accommodate cargo pods of various sizes. Each cargo pod had four small wheels, which allowed it to be easily maneuvered on the ground, also reducing the time the aircraft had to be on the ground. Once positioned under the fuselage, the nacelle was raised into position by electric winches built into the four corners of the fuselage. The pod was then locked in place with ball joints. Finally, the seam between the fuselage and the nacelle was sealed with an inflatable seal.
The XC-120 Pack Plane had a C-119B fuselage; at a point just below the cockpit it was cut away to create space for the removable cargo pod. The wings were raised between the engines and the fuselage, raising the fuselage several feet and giving the aircraft a gull-wing appearance. Smaller diameter “twin” wheels used as nose wheels were installed forward of the main landing gear struts. At the same time, the main struts have been extended further back.
The corresponding “nose” and “main” landing gear were raised and lowered in a scissor-like manner to lower the XC-120 as well as to facilitate the removal of a variety of wheeled pods that needed to be attached under the fuselage to transport goods. Since the cargo had to be pre-loaded into the pods, Fairchild claimed that the cargo could be loaded/unloaded much faster.
The aircraft’s specifications included a length of just under 83 feet and a height of just over 25 feet. The XC-120 had a wingspan of 106.5 feet and a wing area of 1,447 square feet. It was powered by two Pratt & Whitney R-4360 Wasp Major radial engines, each developing 3,250 horsepower for takeoff; its top speed was 258 mph. The aircraft had a five-man crew (pilot, co-pilot, flight engineer, two loadmasters), with a capacity of 20,000 pounds or 2,700 cubic feet of cargo.
The plane’s first flight was observed by an Associated Press (AP) reporter, who described it as follows: “The XC-120 can land, drop off its cargo-carrying ‘pod’ and leave it to ground crews to unload and reload it over time as conditions permit.” The AP article also said, “From a logistical perspective, this will save valuable time, provide greater mobility and reduce potential casualties in the event of an enemy attack.”
After its first flight, the XC-120 was extensively tested by Air Proving Ground Command at Eglin Air Force Base, Florida in 1951. It also appeared at several air shows in the early 1950s Production aircraft were to be designated as the C-128.
However, when the Air Force made the decision not to order a production run of the aircraft, the project was abandoned in 1952. Fairchild made only one prototype of the XC-120; it was later scrapped.
Problems with the plane
During test flights of the XC-120, it flew well when carrying a pod, but was very unstable without a pod attached. The aircraft’s handling was commented on by James Winnie, who served as a flight engineer during the XC-120’s test flights at Eglin Air Force Base. “Glad they only made one,” was his terse comment.
Over time, the stability issues of the XC-120 may have been resolved. However, when the Korean War started, the army needed more C-119s, which were proven and reliable aircraft. Additionally, testing of new concept aircraft became a much lower priority for Fairchild and its military customers due to the war.
As noted above, due to the instability of the XC-120 and the Korean War (which led to increased production of the Fairchild C-119 and significantly changed the focus of the military), the The aircraft’s modular transport design has never advanced.
However, my research on the XC-120 made me think more than once of Malcom McLean, who developed the intermodal freight container a few years later. McLean’s container and Fairchild’s pods looked very similar. While the XC-120 project was shelved, McLean’s intermodal container finally revolutionized the transport of goods by ship, rail and truck.
Consider this – the Pack Plane first flew on August 11, 1950. McLean was developing his ideas and design for the cargo container and container ship from 1952 to 1955; the maiden voyage of his converted tanker (which became the world’s first container ship) did not take place until April 1956.
If the two ideas had overlapped temporally, who knows what might have happened. Granted, the idea behind the XC-120 wouldn’t have sounded so radical.
FreightWaves Classics thanks aviastar.org, history.net, militaryimages.net, transportationhistory.org and Wikipedia for the information and photographs that made this article possible.