Douglas C-133 Cargomaster
The Douglas C-133 Cargomaster was a four-engine turboprop strategic airlifter built by the Douglas Aircraft Company. It first flew on 23 April 1956 and went directly into production without prototypes: 50 aircraft, 35 C-133As and 15 C-133Bs, built between 1956 and 1961. Designed to carry complete ballistic missiles and up to 110,000 pounds of cargo, it served the Military Air Transport Service and Military Airlift Command from Dover and Travis, proved invaluable in Vietnam, and was withdrawn in 1971 as fatigue problems mounted and the C-5A Galaxy arrived. Most were scrapped; a handful survive in museums, and one flew in Alaska until 2008.
Why It Mattered
The C-133 Cargomaster was the first United States Air Force transport powered by turboprops, and it was designed around a load no earlier airlifter could manage: a complete intercontinental ballistic missile. Douglas developed it for the Air Force's Logistic Carrier Support System, as an air transport for America's large missiles, and the hold could swallow a fully assembled Thor, Jupiter or Atlas, or 110,000 pounds of other cargo. For many years it was the only Air Force aircraft able to haul very large or very heavy loads, on routes that spanned the world. Only fifty were built, and fatigue ended the fleet's career in 1971.
Design Notes
The Cargomaster went straight into production as the C-133A; Douglas built no prototypes. Four Pratt & Whitney T34 turboprops — the largest turboprop engines ever built, in the Air Mobility Command Museum's words — powered the aircraft. The cargo compartment ran 97 feet 4 inches in length and stood 13 feet 4 inches high, and it was pressurized, heated and ventilated. The landing gear folded into external blister fairings along the fuselage sides, leaving the hold unobstructed, and freight came in through a two-section rear door whose lower half formed a drive-on ramp, or through a side door in the forward fuselage. The last three C-133As introduced a clamshell rear door that lengthened the compartment by three feet, enough for a completely assembled Titan missile, and the fifteen C-133Bs that followed kept the doors and gained more powerful engines.
Operational History
The first Cargomaster flew on 23 April 1956, and deliveries began in August 1957, when the first C-133As reached the Military Air Transport Service at Dover. In 1958 the fleet began flying MATS routes throughout the world, and two Dover-based aircraft set transatlantic speed records for transports on their first flights to Europe. The type's great loads were missiles: C-133s airlifted several hundred Minuteman and other ballistic missiles between their operational bases, and carried Atlas, Saturn and Titan rockets to Cape Canaveral for the Mercury, Gemini and Apollo programmes. When Apollo capsules came down at sea, C-133s airlifted them from Norfolk or Hickam to Texas or California. The Air Mobility Command Museum records that the fleet of fifty proved itself invaluable during the Vietnam War. Losses were heavy: nine of the fifty aircraft built were lost in crashes and a tenth was destroyed in a ground fire. In February 1970 the last of these losses came when a C-133B disintegrated in flight over southwestern Nebraska, after a hidden skin crack spread catastrophically. Fatigue problems across the fleet brought withdrawal in 1971, when the C-5A Galaxy replaced the type.
Afterlife
Most of the fleet was cut up within months of the final flights to Davis-Monthan Air Force Base in 1971. Three aircraft anchor the type in museums: C-133A 56-2008, which had set a world payload record for propeller-driven aircraft in December 1958, at the National Museum of the United States Air Force; C-133B 59-0527 at the Pima Air & Space Museum in Tucson; and 59-0536, the last C-133 built, at the Air Mobility Command Museum at Dover. One aircraft outlasted them all: C-133A 56-1999, flown as N199AB, hauled cargo in Alaska until 2004 and made the type's last flight in August 2008, to Travis Air Force Base, where it is kept on static display at the Jimmy Doolittle Air & Space Museum. Two further C-133As have remained in storage at Mojave Air and Space Port in California since the 1970s.