Aero-Terms!

Aero-Terms are designed to be a daily reminder of the terms, names, acronyms and explanations of the unique language that populates the aviation world. Aerospace, sport aviation, fixed wing, helo, you name it... it's all fair game.

Aero-Terms should serve as a quick but intriguing reminder of the terms you may use every day, or an introduction to an aspects of the Aero-World you may not yet be familiar with. ANN also encourages readers to go beyond the FMI link, and further research any intriguing terms.

Suggestions for future Aero-Terms are ALWAYS welcome, as are additions or discussion of the explanations given for each Aero-Term.

Armstrong Limit

Often called Armstrong's Line, is the altitude that produces an atmospheric pressure so low (0.0618 atmospheres), that water boils at the normal temperature of the human body: 37 °C (98.6 °F). It is named after US Air Force surgeon Harry George Armstrong, who first described it. The altitude is variously reported as being between 18.9-19.4 km (62,000-63,500 feet or about 11.8 miles). At or above this point, exposed human fluids will boil without a pressure suit, and no amount of breathable oxygen, delivered by any means, will sustain life for more than a few minutes. A human would, eventually, boil in their own body fluids (a process known as ebullism), though death from asphyxiation would occur first, as the barrier of the skin and control of blood pressure would prevent blood from boiling immediately.

FMI: www.geoffreylandis.com/ebullism.html