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How Pressure Relief Valves Made The World’s Fastest Airliner


Most of the time, vacuum relief valves are fitted to tanks and machinery that are safely placed on solid ground. Even tanker trucks with valves are firmly and safely secured to the ground as they travel from a secure location to their destination.

Aircraft are far more complex because the conditions that their payloads are subject to change dramatically owing to the changes in atmospheric conditions as an aeroplane ascends. 

Nowhere are these challenges more evident, however, than with the world’s fastest passenger airliner: Concorde.

At the time it was being developed, there were a lot of concerns about whether it was even possible, and perhaps because of the complexity and compromises required, only two supersonic jets (Concorde and the Tupolev Tu-144) would ever be used for passenger flights.

There were many compromises made to make a plane capable of reaching a cruising altitude of 60,000ft that would make supersonic flight possible safely, and the use of several pressure valves was part of this process.

One of the biggest dangers of flying at this altitude was a need for a much greater cabin altitude pressure than a subsonic aircraft in order to counteract the considerably thinner air near the edge of space.

According to Heritage Concorde, Concorde was pressurised at an atmospheric equivalent of 5,500 feet, which is the same elevation as Johannesburg South Africa or Denver, Colorado. This can still be considered a relatively high altitude, but most passengers can handle it.

If the atmospheric pressure is too high, the safety valve opens to release some of this pressure and preserve the safety of the cabin crew and passengers, although with exceptionally strict limits as the lower the air pressure, the more difficult it can become to breathe.

If there is a complete loss of cabin pressurisation, such as if a window broke, most people would only be able to remain conscious for seconds before the lack of oxygen would take effect.