THE crack dirigible of the Germany army, the semirigid “M III.,” was partially destroyed by fire Just before the end of the “Kaisermaneuvers,” in which it had rendered valuable services on the “red” side, The circumstances of this accident are interesting and instructive. The “M III.” was of the Gross-Base-nach German semi-rigid system, which differs from the original French semi-rigid Lebaudy system in separating the gas bag from the stiffening frame, making the latter part of the suspension, and dividing it into three separate sections better to withstand shocks in landing and facilitate dismantling. The envelope is similar to that of the Parseval system, having two ballonets fore and aft, with a distributing valve for the air between, to assist the vertical steering, which is done principally by shifting water with a pump between two tanks at the extremities of the combined stiffening frames. A seemingly slight, but as the accident has shown essential, defect was traced to the pos'tion of the blower for the ballonets. It is not carried in the car, but far above it, next to the frames, and driven by rope transmission to reduce the drag in the air of a long hose connection between car and envelope. The “M III.” displaced 240,000 cunic feet, had a length of 300 and a beam nf 88 feet. The car was 40 feet long, and the distance between the bottom of the car and the top of the envelope stood 07 feet. The horse-power was 300, furnished by four Koerting motors, driving two propellers. The “M III.” was equipped with wireless telegraph apparatus, and armed with apparatus for discharging explosives. In the maneuvers the whole crew of seven was furnished with rifles, kept in a special rack. Five of the crew were required to handle the ship, and two were observers. All hut the engineers were army officers. In this year's army maneuvers in Mecklenburg, Uckermark. and Pommerania, from September 7th to 14th, the “M 1IT.” had successfully performed all its alotted tasks, and, after ascending from Dem-ming, Pommerania, in the morning of September 13th, was cruising in steady, certain flight over the villages of Golchen and Clempenow, when suddenly the rope transmission to the blower snapped. The gas bag began to lose its shape, and repairing in the air being not feasible on account of the blower's position, a landing became imperative. The dirigible was then drifting with useless motors toward a broad stretch of meadow on both banks of the Tollense River, a. tributary of the Peene. From the air, m consequence of a well-known optical illusion, this meadow was apparently perfectly level and an excellent landing place. The pilot was evidently not an experienced airman, for he failed to recognize that the land formed a shallow valley, into and across which a lively “ground breeze” was sweeping The descent, gentle at first, became suddenly very rapid when the airship caught in the descending current. The shock on striking the ground was quite violent. The ponderous envelope and framing continued to come down after the car had struck; fortunately, the wind carried it to the side of the car. From previous experiences with spherical balloons and investigations. it appears practically certain that the tremendous momentum of the heavy flabby mass of rubberized doth of the gas bag and air ballonets, weighted with the framing and, in consequence of the quick descent, carrying a charge d atmospheric electricity, produced minute electric sparks through friction during this violent commotion; for theweather was very dry and hot. The shock at striking the ground also must have started leaks in the valves. The concussion instantly produced a certain quantity of explosive mixture of air and gas (normally the gas bag of a dirigible, unlike the envelope of a spherical, is hermetically sealed against the atmosphere by its safety valves), for there was a dull heavy report immediately after the envelope struck the ground, which shook the windows in the village of Gross below, and a column of flame shot up, which quickly consumed the gas bag with the planes, the framing, and the balky blower. Fortunately, the crew could easily escape by jumping from the car on the opposite side, and the car with the motors and propellers was little harmed. The accident is very instructive in showing how greatly the safety of a dirigible depends on the airmanship of the pilot, and that the facility to deflate and collapse, in place of being a guarantee of security, may, on the contrary, become a source of danger.
This article was originally published with the title "The Burning of the German Military Dirigible “M III”" in Scientific American 105, 15, 312 (October 1911)