The tragedy unfolded unusually slowly for an aviation catastrophe: The crew fought to control the USS Macon for more than an hour. US naval officers threw fuel canisters overboard in an attempt to reduce the weight of their vessel. The canisters imploded on their way to the ocean floor. Meanwhile, the Macon -- the largest rigid airship ever constructed in the United States -- sank inexorably downward, the safety of the Moffett Field hangar just within reach.
The Macon hit the water surface only five kilometers (three miles) off the Californian coast, along the latitude of the Point Sur lighthouse near Monterey, on Feb. 12, 1935. The zeppelin broke apart and sank into the deep water. Two of the 83 crew members died -- the low number of deaths is likely due to the fact that the Macon sank in slow motion.
Neither enemy fire nor sabotage was to blame for the giant airship's doom (and a giant it was: longer than three 747 jets parked nose to tail). A heavy storm above the picturesque stretch of Californian coast known as Big Sur tore off the Macon's vertical tail fin. The airship's structural framework was so badly damaged that the Macon broke apart when it hit the water.
A riddle at the bottom of the ocean
Why and how that happened is the question an interdisciplinary research team now wants to answer. While an investigative commission formed by the US Navy following the catastrophe was able to determine that shoddy repair work was to blame for the crash -- a test flight above Texas had led to damage to the structural framework earlier -- the results reached by the commission were never definitively proven. The commission's researchers had to content themselves with speculation -- after all, the evidence for their hypothesis lay 450 meters (1,476 feet) below the ocean surface. Scuba divers are still unable to reach that depth today, although treasure hunters and dealers in military paraphernalia are sometimes equipped to go there. However, the location of the wreck was kept secret precisely in order to prevent plundering.
It was only in June 1990 that Chris Grech, the deputy director of the Monterey Bay Aquarium Research Institute (MBARI) discovered the first pieces of wreckage on the ocean floor. Several high-tech searches had been unsuccessful during the 1980s. Grech finally discovered the Macon's remains in the middle of a deep-sea reservation area. Its existence is the only reason why what Grech calls a "unique time capsule from another era" has remained untouched for more than 70 years. If commercial fishing had been allowed in the area, dragnets would long since have destroyed the ghostly remains at the bottom of the ocean.
In late September of this year, scientists from MBARI and the National Oceanographic and Atmospheric Administration (NOAA) joined forces with the US Navy. They left Monterey on board the research ship Western Flyer in order to systematically survey the area. Until then, the scientists had to work with low-resolution sonar images of the wreckage, but now an underwater robot, the remotely operated vehicle (ROV) Tiburon, was able to explore the Macon's final resting site -- and take close-up pictures.
A chapter in the history of military technology
"The primary goal of the mission is to conduct comprehensive documentation of the site of the USS Macon's loss that can be used to evaluate the archaeological context of the craft," according to a NOAA statement. But the scientists are also secretly hoping to find the Macon's tail fin -- the part that turned out to be the weakest link in the construction, during the airship's final, ill-starred ocean flight.
Grech, the project's director, says he's noticed changes since his last visit. "A lot of the wreck is covered up," Grech told the New York Times. "It's easy for sediment to build up over time, and some large objects have moved."
Water currents along the Californian coast could pull the Macon's remains so far apart that they would become useless to historians. That's why the September expedition documented every detail of what it discovered, producing a mosaic of photographs. Paradoxically, the most easily recognizable objects on the photographs are the remains of four small Curtiss F9C-2 "sparrowhawk" fighter planes. The airship was intended to function as an airborne aircraft carrier -- an enormous, cigar-shaped vessel that would carry the small, agile biplanes much further into the airspace above the Pacific Ocean than they would ever have been able to venture themselves. The propeller-driven fighters were meant to fly reconnaissance flights above the ocean. As early as the 1920s, the US Navy was preparing for a war in the Pacific.
"The planes don't look damaged," Grech told the New York Times, pointing out that the wings of the planes are intact and that their bright yellow color and blue and white Navy star are visible. What is more, five of the Macon's giant Maybach engines can also be seen lying on the ocean floor off Point Sur, along with parts of the airship's canteen and the officer's quarters. An aluminium chair, a metal cabinet, a desk and several shelves offer insight into the interior design preferences of the 1930s military.
No tail fin, no corpses
The Macon consisted of a rigid framework made from aluminium alloy; the framework supported a canvas hull. Inside the hull, helium tanks ensured the overall construction was lighter than air. While the giant airship's overall weight was more than 200 tons, the lightness of its construction materials has turned out to be the very factor that poses special difficulties for today's underwater archaeologists.
Only two thirds of the wreck have been discovered and mapped, according to Grech. When they returned to the port of Monterey, the scientists had to face up to the fact that the Macon's missing tail fin -- the decisive component of the crashed airship -- has yet to be discovered. "It's either buried under sediment or in one of the canyons," Grech told the New York Times. Nor was any sign of the two victims of the crash discovered. Bruce Terrell, a marine historian at NOAA, told the New York Times that the researchers "had not seen any indication of human remains."
The loss of the USS Macon in 1935 marked the end of the US Navy's dirigible program, which already had a 20-year history then. The program had long been criticized for the high costs involved -- costs especially well exemplified by the USS Macon, the most expensive aviation object of its time. Following the Macon's crash, concerns about costs were compounded by security-related arguments, and the aviation program no longer seemed justifiable. And yet the airship the New York Times called the "high-tech wonder of its day" was off to a good start: The construction was considered especially safe, since it contained no flammable hydrogen, but only helium, which cannot explode.
Two years later, the most famous of all airship disasters demonstrated just how dangerous the use of hydrogen -- which is lighter and cheaper than helium -- can be: On May 6, 1937, the German airship LZ 129 Hindenburg caught fire on the Lakehurst airfield in New Jersey, where the USS Macon had been stationed for a brief period of time as well. Filled to the brim with hydrogen, the Hindenburg caught fire while landing on the airfield -- 36 of the 97 persons on board died. That day, military strategists lost whatever interest they may still have had in the use of airships for military purposes.