Very few people in or out of the Air Force can answer that question now. Some will ask if the C-133 was a variation of the C-130. Old C-133 hands will tell you that it was the box the C-130 came in. But, the C-133 was far more than that. It was the first true heavy airlifter of a young United States Air Force, bridging the gap between the World War II-era transports and the C-5 Galaxy.
The Douglas C-133 Cargomaster first flew on 23 Apr 56 and served in three squadrons from 1957 to 1971. These were the 1st and 39th Military Airlift Squadrons (MAS) at Dover AFB, DE, and the 84th MAS at Travis AFB, CA. For seventeen years, C-133s carried every imaginable outsized cargo to destinations around the world. The C-133Bs were especially valuable to the growing intercontinental ballistic missile (ICBM) force and the American space program, because they were the first transport aircraft specifically designed to carry an entire missile from the factory to operational bases.
The lineage of the C-133 does not include its immediate Douglas predecessor, the C-132, which took form only as a single full-scale mockup. The C-132 is most easily visualized as a C-5 fuselage with a single conventional tail and swept high wings with four 15,000 hp turboprops. The wingspan was 177’6”, length 179’3” and height 57’11”. Gross weight was projected to be 408,000 lb with a 400 mph cruise.
The actual progenitor of the C-133 was the Douglas C-124 Globemaster II, built between 1950 and 1953. The Air Force’s first step was a contract for the YC-124B, a single airplane with T-34 turboprop engines and a pressurized flight deck. Douglas studies in 1951 confirmed that a pressurized fuselage would be severely overweight. Over a two-year period, the design moved through several permutations until, in 1952, the Model 1333 was defined. It had a high wing, rear loading to a truck-height cargo bed and full pressurization. On 10 Aug 53, the Air Force advised Douglas that this new logistics carrier would be designated the C-133A. The first airplane rolled out on 31 Jan 56, with its maiden flight a 1 hr 35 min trip to Edwards AFB, CA on 23 Apr 56.
Douglas Aircraft Company built 52 C-133 airframes, of which 50 actually were procured by the Air Force and went into squadron service. Of these, 32 were C-133A models and 18 were designated by the Air Force as C-133B. Three B-models were actually hybrid A/Bs, because they incorporated features of both. They were designated as Bs largely because the fuselage incorporated the aft clamshell doors specific to the missile transport mission and the B-model engines. Beginning in 1959, Douglas modified thirteen C-133As to match the configuration of the fifteenth and follow-on aircraft. Thus, all C-133s became capable of loading and hauling ICBMs. Two airframes remained at the factory in Long Beach, CA, for use in structural testing.
At Dover AFB, the 39th Air Transport Squadron (ATS), later the 39th Military Airlift Squadron (MAS), was activated on 28 Aug 57. The first C-133A was delivered to Military Air Transportation Service the same date. A second squadron, the 1st ATS, was added at Dover on 7 May 60, and a total of 32 C-133As were assigned to Dover. The 84th ATS at Travis AFB, CA, began its conversion to C-133As in late 1958. The first B-model was delivered to Travis in April 1959 and the last airplane on 4 Nov 61.
The C-133 was a big airplane, the largest production transport until the C-5 came on line. Wingspan was 179’8”, length 157’6” and height 48’3”, with a normal maximum takeoff gross weight of 286,000 lbs (C-133B). It featured a pressurized cylindrical fuselage, high wings, a single tail fin and tricycle landing gear with the main landing gear mounted in external pods similar to the C-130, C-141 and C-5. Design life was 10,000 hours, but extension programs took most of the fleet to 19,000 hours.
The cargo deck was 50” off the ground, accessed through clamshell doors and a ramp at the tail and a 106”x100” side door on the left forward fuselage. The C-133B could load and carry fully assembled ICBMs. Other cargo carried over the years included propeller shafts for navy ships, diesel submarine motors, aircraft and helicopters and nearly anything else that would fit through an aft entry approximately 159” high by 142” wide, and on a cargo deck nearly 82’ long.
Four Pratt & Whitney T34-P-9W turboprop engines producing 6,950 shaft horsepower (shp) powered the C-133B, up from 6,000 shp on the C-133A. Takeoff power could be augmented by water-alcohol injection, which was very effective, especially in tropical conditions. Cruise speed was 300 mph at altitudes up to a maximum of 35,000’ when lightly loaded. Most missions were flown in a step-climb profile between 18,000’ and 28,000’, depending upon gross weight. The engines drove Curtiss fully feathering reversible-pitch three-bladed turboelectric propellers 18’ in diameter.
Early C-133s set several world records and caused great comment at such international appearances as the Paris Air Show. On 4 Jan 58, two Dover C-133As set a non-stop trans-Atlantic record for cargo airplanes, hauling 80,000 lbs of cargo to Chateauroux, France. In Sep 58, another C-133A record was 85,000 lbs of cargo from Dover to Burtonwood, England, with two stops. Over the ensuing 15 days, five C-133As delivered 600,000 lbs of cargo. In Dec 58, a C-133 set a weight to altitude record with 117,900 lbs to 10,000’.
The first round-the-world trip by three C-133s took place in Jan 59. A record distance was set on the Midway Island to Travis AFB leg of 3,253 miles. This later became a routine transit on Pacific missions. Later, another C-133 eclipsed that record with 4,526 miles from Wake Island to Travis. Perhaps the most notable event in 1959 was the C-133’s appearance at the Paris Air Show. There, the pilot made a two-engine pass before a reviewing stand including French President Charles DeGaulle, who was reported to have called it “Formidable!”
Over the next twelve years, the C-133 carried outsized cargo to destinations all over the world. It participated in numerous major operations where its load-carrying capabilities were essential to success of joint and combined forces. Individual missions carried relief supplies to hurricane-stricken Caribbean islands, helicopters to Peru for earthquake rescue, and deployments to India during the 1962 Sino-Indian border war. NASA employed C-133s many times to move satellite tracking stations and a variety of research facilities to such destinations as Ascension Island, Madagascar and Brazil. One aircraft, C-133A 54136, was placed on permanent loan to NASA on 9 Jun 65.
Once the United States became fully involved in Vietnam, the C-133 was part of the MAC fleet supporting the war in Southeast Asia. The C-133 and C-124 carried outsized loads while the C-135 and C-141 were devoted to higher-priority cargo. In four major strategic airlift unit deployments between 1965 and 1970, the C-133 flew hundreds of missions to carry vehicles and other equipment that would not fit into the C-141. As the war progressed, one of the standard missions for the C-133 was that of redeploying helicopters and aircraft from Vietnam to depots in the United States. Other missions included transport of armored equipment into and within the combat theater to support key campaigns.
For a short time, C-133s and the new C-5A Galaxy overlapped as outsized cargo transports. This situation did not continue for long, though, for the C-133s were simply wearing out. Initially designed for a 10,000-hour airframe life, several major life extension programs carried most airplanes out to 19,000 hours. Fatigue and stress corrosion had become critical issues that were forcing decisions about retiring the C-133. Air Force studies beginning in 1968 looked at the possibility of further service life extensions to as much as 25,000 hours, but there were serious impacts upon MAC’s operational capabilities. By 1970, the final decisions were essentially made to retire the C-133 in fiscal year 1971.
The necessity for such a decision was tragically emphasized with the tenth (and last) C-133 crash on 6 Feb 70, in Nebraska. An existing undetected stress crack in the forward fuselage propagated dramatically, causing skin to fly into number three engine. Earlier crashes dated back to 13 Apr 58, during a local flight at Dover AFB. Of the remainder, four happened overwater shortly after takeoff, with causes never determined. A Travis C-133B crashed during a local flight and a Dover C-133A crashed on departure from Goose Bay, Labrador. A Dover airplane was destroyed in a refueling fire. Only one aircraft was successfully ditched, near Okinawa in 1967, with all crew rescued. Despite the 20% loss rate over its lifetime, the overall accident C-133 rate (accidents per 100,000 hours) was below the USAF average over its 14-year operational history. Though not conclusively proven, one most likely cause was aircraft stalls in different flight conditions. Other contributing factors may have been errors in basic weight and center of gravity measurements. Problems with propeller electrical systems were definitely a factor in the Okinawa crash.
With its retirement in 1971, the C-133 rapidly passed into obscurity, though five airframes are in civil registry and some still fly specialized cargo missions. Four airplanes are preserved at the Air Force Museum, the Pima Air Museum, Chanute AFB, and (by mid-2000) the Air Mobility Command Museum at Dover AFB, DE. A fifth museum aircraft at Bradley Field, Connecticut, was destroyed by a tornado in 1980. Thirty C-133s are listed as scrapped, but several partial hulks were at Davis-Monthan AFB, AZ, as late as 1999.
Though most C-133s are gone, they are far from forgotten by those who flew and serviced them. These magnificent airplanes fulfilled a vital mission for the Air Force during the transition from World War II designs to modern jet transports. They could carry cargo that would not fit into any other airplane, especially the ICBMs, delivering it to operational locations around the world. The C-133 established records for weight lifted and distance flown that soon became routine operations for its squadrons. In its design and testing process, new innovations in testing, instrumentation and equipment were developed that later became standard on many other airplanes.
So, in answer to the child's question, one can say that the C-133 is an unsung giant that served the United States Air Force well in a role no other airplane could fill.
