The Curse of the Cargomaster

Readied to transport the first U.S. ICBMs, the Douglas C-133 had a peculiar habit. It kept crashing.

In the 86-foot-long cargo bay, former crewmen recall the hardware a C-133 could lift. (Mark Duehmig)
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Delivering outsized cargo all over the world, Cargomaster crews were flying thousands of uneventful hours. Still, the drumbeat of accidents continued. “There was sort of a mystique around the aircraft,” says Nakagawa. “It had a reputation as mysterious, since a lot of them just disappeared.”

If you were headed home on leave and waiting in a passenger terminal to fly space-available, would you take the seat on the Cargomaster running up outside, or wait for whatever came along next? “There were a lot of people who were really scared to fly in it,” says Nakagawa. “And there were people who [did] even though they were apprehensive.” But Cargomaster crews, says Nakagawa, “wanted to make it work. They were dedicated to it.”

“I was never scared of it,” says Burnett, who instructed many of the crews at Dover. “It seemed to me that the more we could learn about it, the better we’d be. But I respected it.”

In 1963, a full-scale investigation of the Cargomaster, the first of many, was convened at the Warner Robins Air Materiel Area in Georgia to help Military Air Transport Services study the five C-133 crashes. “They convened everybody,” says Cal Taylor, a former Cargomaster navigator and perhaps the airplane’s most knowledgeable historian. “The airplane builder, MATS… [they got] everybody involved to figure out what was going on.”

“We had some of the best minds in aeronautics working on the problems of the C-133,” says Sandstrom. “I took an airplane down to Warner Robins and while it was down there, they tore it completely apart. They put it all back together, and I was sent down there to preflight it. It flew just like it did when we flew it down there. They didn’t figure out anything.”

Roy Isaacs was a young structures engineer at Douglas when the first C-133 rolled off the line in 1956. He remembers one Air Force requirement stating that the airplane, when fully loaded, would be able to clear a 50-foot obstacle at the end of a 10,000-foot runway. “We had to redesign all the sections of the airplane three times,” Isaacs recalls, “and we had to lighten [the airframe] and get the weight down to accommodate the engines. Consequently, it made the airplane have a bunch of problems. That engine is the downfall of the C-133.”

That engine was the Pratt & Whitney T34, the only turboprop available at the time that could get an airplane as heavy as a fully loaded Cargomaster off the ground. During cruise, the engines ran at a constant speed. To vary the thrust, a governor inside the propeller’s nose case (located aft of the propeller blades) changed the blade pitch. When the pilot pushed the throttles forward to increase power, the governor angled the propeller blades to take a bigger bite of air. The mechanism in the nose case was in turn governed by a complex, electrically controlled system that synchronized blade pitch among the four engines.

“You could have a prop malfunction, and a number of things could cause it,” says Ken Kozlowski, a former C-133 crew chief who served as chief mechanic and flight engineer on a privately owned Cargomaster that flew until 2008. Through monastic devotion to understanding every system on the C-133 and by developing his own maintenance procedures, Kozlowski kept the civilian Cargomaster flying as a bush airplane—and slamming onto remote Alaska gravel runways—nearly 40 years after the Air Force let it go.

Minute changes in engine performance, coupled with changes in altitude, airflow, or synchronization, kept the nose case mechanism constantly working to maintain optimum blade angle. At higher altitudes, the props had to increase pitch to move the same amount of air; at lower altitudes, the pitch needed to be reduced. Thomas Kaye, who was an Air Force hydraulic mechanic stationed on Midway, remembers seeing Cargomasters arriving from Japan that had been four-engine transports on takeoff but had only three engines operating by the time they landed. Once, a C-133 showed up with only two engines. It had been able to stay aloft only because the flight engineer injected a water-alcohol mixture (a standard takeoff booster) when the airplane was threatening to head toward the waves.

“The nose case [governor] would go,” says Kaye. “The pitch was constantly changing to keep the [propellers] phased, and it was constantly loading and unloading the gearing in the nose. What they did later on was put a little time-delay relay and slowed the pitch changes down, which relieved the excessive load on the nose cases.”

About John Sotham
John Sotham

A former associate editor of Air & Space, John Sotham is a hopelessly nearsighted frequent flyer, with thousands of hours logged in exit rows worldwide. He is a retired U.S. Air Force Reserve colonel and a former crew chief on the F-4D Phantom II and A-10A “Warthog.” He started collecting aviation books when he was eight years old. Any opinions expressed are solely the author’s.

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