The Italian semi-rigid airship Roma was designed by Celestino Usuelli, the engineers Eugenio Prassone, Umberto Nobile and Colonel Gaetano Arturo Crocco. It was the first project of the Stabilimento Costruzioni Aeronautiche (“Aeronautical Construction Factory”), as the partnership of Umberto Nobile, Usuelli, Giuseppe Valle and Bennetto Croce was known. Originally designated T-34, it was designed for trans-Atlantic crossings and was the largest semi-rigid airship in the world at the tie.

As a semi-rigid design it was built about a rigid keel – though the keel was partially articulated to allow some flexibility. The passenger spaces and control cabin were within the keel. The engines, 400 hp Ansaldos, were mounted outside, angled such that the slipstreams would not interfere with each other. In addition to the 11 cells of hydrogen within its skin, it housed six cells of air, called ballonets, into which additional air could be pumped if the gasbag drooped or flattened.

It first flew in September 1920.

It was purchased by the United States from the Italian government for $250,000 in 1921. After purchase by the US, in March 1921 the Roma flew the 300 miles from Rome to Naples and back carrying the US Ambassador. After transportation to the US, Roma flew on 15 November 1921 with minor problems. When Langley crews unpacked the crated airship that August, they found its fabric skin mildewed and weakened. Six new, American-made Liberty motors, were ordered as replacements for the balky Italian powerplants.

It served in the US Army until February 21, 1922, when it crashed.

The Roma crashed in Norfolk, Virginia on February 22, 1922. The crash was caused by failure of the airship’s box rudder system, which allowed it to maneuver over tight areas. The airship contacted high voltage lines, and burst into flames. A total of 34 were killed, 8 were injured, and 3 escaped unharmed. Among the dead was the airship’s pilot, Captain Dale Mabry.

At 12:45 p.m., the preflight checks complete, 45 souls on the manifest – the crew, a few civilian mechanics, government observers – stepped aboard. The rain had stopped. The temperature had warmed to 46 degrees.
One hundred fifty men gripped lines holding the airship to earth as the Roma’s crew completed last-minute preparations for launch. The Libertys were fired up, then idled. All six worked.
Lines dropped away. The airship swept upward, tail first, then leveled.
At 500 feet, Mabry (the ship’s skipper) ordered cruising speed and, engines roaring, the Roma began making for the Chesapeake Bay. It reached it near the mouth of the Back River. Mabry ordered the ship south along the shoreline, toward Old Point Comfort. The crew waved to people below at Fort Monroe, looked down on the site of the burned Hotel Chamberlin, at crowds on the government pier. The Roma headed out over the water toward Willoughby Spit. The spit was dotted with waving Norfolkians agog at the mammoth craft overhead.
Mabry steered the Roma toward the Navy base.
After passing over the Spit and cruising over the Norfolk Naval Station, crewmembers noticed that the upper curve of the gasbag’s nose was flattening. The Roma, pitched nose-first toward the ground. From far astern came a cry: The keel was slowly buckling. Then another: The tail assembly was coming loose. The Roma began to bullet earthward at a 45-degree angle.
On the ground, sailors and civilian base workers watched the ship’s nose tilt, and warehousemen at the Army’s nearby Quartermaster Depot stepped outside to witness what was, clearly, an airship in trouble.
The skipper could see the greens and fairways of the Norfolk Country Club ahead, beyond the depot and the Lafayette River.
If they could get the Roma that far, they could put it down somewhat safely.
The passengers and crew, meanwhile, began to panic, to toss everything they could get their hands on through the keel’s windows – tools, furniture, spare engine parts. People on the ground watched a shower of equipment fall to earth.
But the Roma’s dive continued. The ground rushing to meet the falling ship was a scrubby field at the depot, split by a small road – and by a high-voltage electric line. The end came in a flash.
The Roma’s nose hit the ground, its massive girth brushed the electric line, and in an instant it was engulfed.
Its gas cells, loaded with more than a million cubic feet of hydrogen, blew to atoms.
The blast set off the ship’s gasoline tanks, creating a pyre of flame and smoke and din that leapt from the field and into the overcast sky.
Depot workers and sailors rushed to the wreckage, but the flames kept them back. Three fire companies spent five hours quelling the blaze, and watched as the Army’s greatest airship shrank to a pile of twisted aluminum that glowed red into the evening.

The event marked the greatest disaster in American aeronautics history at the time. It was the last hydrogen filled airship flown by the US military; all subsequent ships were inflated with helium.

Engines: 6 × Liberty L12, 300 kW (400 hp) each
Length: 125 m (410 ft 0 in)
Diameter: 25 m (82 ft 0 in)
Volume: 33,810 m3 (1,193,000 ft3)
Height: 92 ft
Empty weight: 34,500 kg (76,000 lb)
Useful lift: 19,100 kg (42,000 lb)
Maximum speed: 128 km/h (80 mph)