What happened
On 21 August 2023, a C-17A, tail number 10-000215, operated by the 437th Airlift Wing, conducted a high-altitude simulated airdrop mission off the coast of Alaska. The flight was part of a planned seven-hour test of ranges involving a medium range ballistic missile payload. During the mission, the aircraft was fully depressurized to 24,900 feet mean sea level, with all personnel utilizing oxygen systems.
Following the successful execution of the test pass and the subsequent closure of the cargo doors, a civilian specialist assigned to the Missile Defense Agency (MDA) began exhibiting symptoms of distress. The individual reported profuse sweating, shortness of breath, and pain in the right arm. Physiological technicians on board provided initial assistance for hyperventilation.
Upon the aircraft's return to Joint Base Elmendorf-Richardson (JBER), emergency medical services transported the specialist to the base emergency room. While undergoing treatment for decompression sickness and awaiting transfer to a hyperbaric chamber at a local hospital, the individual suffered a cardiac arrest. The specialist was pronounced deceased on 22 August 2023.
The investigation
The Air Force Accident Investigation Board (AIB) examined the circumstances surrounding the medical emergency and the flight profile of the mission. The investigation reviewed the aircraft's environmental and oxygen systems, maintenance records, and the physiological state of the personnel involved. The board also consulted subject matter experts in high-altitude airdrop physiology and helmet equipment.
Findings
- The death was caused by decompression sickness resulting from the unpressurized portion of the high-altitude military test mission.
- A significant contributing factor to the mishap was the individual's pre-existing medical conditions, specifically obesity, hypertension, and atherosclerotic cardiovascular disease.