Osoaviakhim-1

Investigation

Investigators headed by Prokofiev arrived on site on horseback 24 hours after the crash and issued their first statement on February 1. They acknowledged that the crew died of high speed impact at 16:21 Moscow time; the flight logs, found intact, revealed that the crewmembers were unaware of imminent catastrophe until 16:10, when the balloon descended to 12,000 meters. This moment was marked as the beginning of an irrecoverable dive. Airspeed beyond design limits snapped the suspension cables and tore open the envelope; eventually the gondola completely separated from the falling balloon. There was no evidence of icing despite early reports in Pravda. Autopsy ruled out suffocation or poisoning of the crew; barograph tape indicated normal internal air pressure throughout the flight.

On February 5, a state commission chaired by General Staff deputy chief Mezheninov issued a detailed report that, regardless of later findings and clarifications, provided a stable version of the accident and its causes; the time of impact was changed to 16:23. Later, in 1935, these proceedings were explained at length in a book by one of the commissioners, meteorologist Pavel Molchanov. According to Mezheninov's report and Molchanov's book, during the four-hour-long stratospheric flight the hydrogen inside the balloon was overheated by solar radiation (54 °C above ambient) and expanded beyond the balloon's geometric capacity; excess gas leaked out through safety valves. More gas was lost when Fedoseenko initiated the descent. As the balloon cooled down on its descent, the remaining gas contracted with a catastrophic loss of buoyancy. To stabilize airspeed at safe level the crew would have had to dump 800 kilograms of ballast, but there simply was not that much ballast left. Suspension cables failures started at altitudes above 8,000 meters, where the crew was unable to open the hatch. The commission summarized the causes of the crash by writing:

1. The accident was caused by an increase in vertical descent speed that resulted from changes in lifting gas volume during the extended stay at maximum altitude and subsequent descent into warmer atmospheric medium which further reduced lift. 2. The system failed to withstand shock stress caused by rapid descent and transition into parachuting mode, and began disintegrating. 3. The crew failed to release ballast and dump instruments due to the design flaw that prevented rapid release of ballast. 4. The crew's failure to stabilize vertical speed led to their failure to bail out on parachutes due to erratic tumbling of the gondola. 5. Airtightness and life support systems were in order until the moment of catastrophic fall, as indicated by barometric recorder and Vasenko's log entries ending at 16:13. 6. During the last 9.5 minutes of the fall the crew tumbled inside the rotating gondola, but all crew members remained vertical until the end; their deaths were caused by the final impact. Conclusion: The flight was substantially safe up to 19,500 meters; 20,500 meters was on the edge but presented no imminent danger; ascent to 22,000 meters led to an inevitable accident.

In March the investigators' reports were released to the general public, including the final verdict blaming the catastrophe on the crew's "recklessness in rise for record".