The Helicopter Aircrew Breathing Device or HABD (also known as a HEED or SEA [1]) is a piece of military survival gear which was adopted in order to increase the chances of survival for embarked troops and aircrew trapped in an aircraft which has ditched (crashed into a body of water.) Similar in function to SCUBA gear, it consists of a small cylinder pressurized with atmospheric air and first stage regulator worn in a pouch on the user's flotation vest; a pressure gauge; an air hose and a special second-stage regulator (the part that delivers air via the user's mouth). The regulator is on-demand (it only delivers air when the user breathes in) and is designed to be highly rugged in order to survive impacts associated with emergency ditchings.
Since a full-size SCUBA cylinder would be prohibitively bulky, especially for troops already laden with full combat gear, the HABD must be small and thus limited in capacity. It provides roughly two minutes of air at the surface. This decreases rapidly with depth and with the heightened breathing rate that accompanies stress. Still, even a few breaths in such a situation can mean the difference between life and death.
Helicopter ditchings usually come with little warning, often while the pilot is attempting a ship landing or other low-altitude maneuver. Because they are top-heavy, ditched helicopters invariably flip upside-down upon hitting the water. The crew and embarked troops will be bombarded with violent jerking motions and several tons of incoming water, which causes unsecured gear to fly uncontrolled throughout the cabin and can knock troops unconscious. Jet fuel and hydraulic fluid often seep into the cabin and can cause blindness to open eyes and lung damage if inhaled. Troops unfortunate enough to find themselves in a ditched helicopter will be upside-down, disoriented, often in the dark and in a rapidly sinking bird. Immersion in cold water evokes a "gasp" response in humans, which limits their breath-holding ability to as little as 15 seconds. Panic is fatal. The HABD, properly used, provides troops with an invaluable tool to help ward off panic and buys them precious extra time to escape.
The Helicopter Emergency Egress Device (HEED) was introduced to the USAF by MSgt Andre' K. Leamons after losing a helicopter and crew off Kadena Japan in the late 1980s. Sergeant Leamons was the Life Support Superintendent for Air Rescue Service and introduced the HEED bottle to be included on crewmember survival vest for all Air Rescue Service members who flew over water. In the event of ditching, the HEED would provide additional time to escape from a submerged helicopter. MSgt Leamons found that the helicopter would turn over because the weight of the motor and rotor blades and sink upside down until it reached neutral buoyancy, which would leave the aircraft just below the surface. The HEED bottle would supply about 2–3 minutes of air, just enough to allow the crew to escape the aircraft and swim to the surface.