What is "normalair"

Normalair Garrett Limited (NGL), or Normalair, was a British manufacturing company based in Yeovil, Somerset, England. It manufactured high altitude life support equipment for the aerospace industry. It is now a wholly owned subsidiary of Honeywell International Inc known as Honeywell Aerospace Yeovil (HAY).

The company originally grew out of the Westland Aircraft Company who in 1933 enabled the Houston Everest expedition to make the first ever flight over Mount Everest, using oxygen and heating systems - precursors of the systems that would eventually be produced by Normalair.

Westland Aircraft produced a cabin pressurisation control valve in 1941 for use in the Westland Welkin high altitude fighter bomber aircraft. Though the Welkin never got into full-scale production the same valve was used in Mosquito, Wellington and Spitfire aircraft.