An Army HU-1A Bell Iroquois helicopter crashed while on a demonstration flight at Parks Air College, East St. Louis, Illinois, 21 October 1959. The tail boom and the engine tore free at successive impacts, and the roof was crushed into the cockpit and cabin when the helicopter came to rest inverted. The pilot sustained serious injury; the crew chief, minor injury. No other persons were aboard. A crash injury investigation conducted by Aviation Crash Injury Research found that (1) the seat and cushion contributed to the amplification of the crash force imposed upon the pilot; (2) the structure supporting the roof was not strong enough to prevent the roof from crushing into the cockpit and cabin under survivable crash force conditions. The investigation found also that (1) the skids and cross tubes seem to have absorbed a considerable amount of crash force; (2) the doors broke off and allowed large exits for escape; and (3) the fuel cells are located in an area not highly subject to impact damage. As a result of the above findings the attention of responsible military authorities is called to the following recommendations: (1) Immediate steps be taken toward increasing the integrity of the roof structure of this type helicopter. (2) Any seats used should offer their occupants a high degree of energy absorption. (Author).