***image1***WWII-era American cargo airplanes were simply airliners with the passenger seats ripped out. They sat high off the ground and the cargo went in and out through an enlarged passenger door on the side. Most were “tail draggers” with a sloped cargo deck that was hard to load. Later aircraft like Douglas C-124 had nose doors and tricycle landing gear, but aircraft was almost 14 feet high and the drive-up ramps were slanted up 45-degrees – very tricky for heavy cargo. In the early 1950’s, the U.S. Air Force issued a request for its first strategic airlifter but decided to wait for an all-jet cargo plane (this would become the C-135). However, with the development of intercontinental ballistic missiles (ICBM), an urgent new requirement appeared for a strategic airlifter able to carry the first US ICBM, the Atlas, a requirement that could not wait for the new jets.
Thus was born the Douglas C-133 “Cargomaster.” While the C-133 was a new airplane, Douglas had participated in the 1951 competition for a shorter range transport that became our beloved C-130 “Hercules.” The C-133 was clearly a product of the completion, and as one can see from the picture above the C-133 seems to be, at first glance (and second glance, and third … ) simply a scaled up C-130. The C-133, like the Hercules, had it wings on top to keep the main spar from entering the cargo area. The main landing gear was placed in pods on the side of the cargo hold to allow the cargo floor to be as close to the ground as possible and it was powered by four turboprop engines – all like the C-130. But the C-133 was much larger − half again as long, with a 40’ greater wingspan and could carry more than twice the payload of the C-130. Indeed, the C-133’s circular fuselage was essentially “fitted” around the 80 feet long, 18 feet diameter of the Atlas, with an 86’10” long cargo bed and about 20 feet in diameter.
One usual feature of the C-133 was the angle the wing was set into the fuselage. Since the C-133 was designed to carry the Atlas missile, it was very long and, with the low landing gear, could not rotate the nose or the back of the aircraft would scrape the ground. Thus the C-133 wings were canted up at a slight angle to allow it to take off and land with a much lower fuselage pitch angle than a normal aircraft.
The C-133 entered service in the late 1950’s, and 50 were delivered to the U.S. Air Force The C-133 was the only plane that could haul the Atlas, Titan and Minuteman ICBMs from the factory to bases across the US, which is was much quicker and, in some ways, safer than driving them. C-133s also carried ICBMs modified as launch booster rockets to Cape Canaveral for the Gemini, Mercury and Apollo space programs. C-133s carried recovered Apollo capsules back to their home bases for refurbishing and later in its career was used to move large and outsized cargo back and forth from the U.S. to Vietnam.
The C-133 was not a poster child for flying safety. Its airframe was originally intended for 10,000 hours, but later this was extended to 19,000 hours. Severe vibration had caused critical stress corrosion of the airframes resulting in wing cracks, and electrical problems were also common. Ten of the 50 C-133s were lost in accidents, nine in crashes — many unexplained, two in the vicinity of the Bermuda triangle − and one was destroyed in a ground fire. But since the C-133 was viewed as a stopgap before the arrival of all jet airlifters like the C-5 and C-141, most of the fixes were not long term. The last C-133 was retired in 1971, but several exist in museums, including one at the U.S. Air Force Museum and one at the Air Mobility Command Museum. (For questions and comments, e-mail firstname.lastname@example.org)