1951

Jet Engine Testing

One thing engineers have to consider, and we out in consumer land rarely think about, is all of the edge cases. What happens to a product when it is not operating under standard conditions?

One of the most fascinating set of edge cases can be seen when testing jet engines. It is one thing for a jet engine to operate in smooth, clean air at 30,000 feet. But jet engines often operate in very different conditions, and they have to be able to handle these situations with ease. Engineers take these scenarios into account during the design process and then test rigorously to make sure the edge cases do not cause catastrophe.

Take the simplest example: rain. Rain can have a big effect on a jet engine. The engine inhales the rain directly and then pushes it straight into the combustion chamber. The engine needs to handle the water without extinguishing itself, even in hurricanes. Therefore a large jet engine might be tested with 1,000 gallons (3,800 liters) of water flowing in per minute. The same kind of thing applies to snow, hail, and ice testing. Another interesting situation is a sandstorm.

The most surprising thing that jet engines must handle is a bird strike. Birds are common, so a large jet engine might get tested by shooting 5-pound (2.2 kg) chickens into the intake. The front fan blades need to slice the chicken without blade damage, and the compressor needs to digest the chicken slices. The de Havilland Aircraft Company created the first chicken gun in 1951 for testing jets.

There are limits, however, as seen in the famous case of US Airways flight 1549 in 2009. That airplane ran into a flock of Canadian geese at approximately 3,000 feet (915 meters). These birds can have 5-foot (1.6 meter) wingspans and weigh 10 pounds (4.5 kg) or more. The two engines could not process the birds and flamed out. This resulted in the historic landing in the Hudson River, where other engineers had anticipated the problem of plane flotation. The fact that there were no injuries is a testimony to the pilot and the quality of the engineering.

SEE ALSO The Wright Brothers’ Airplane (1903), Boeing 747 Jumbo Jet (1968), C-5 Super Galaxy (1968).

An F119-PW-100 jet engine is tested in a full afterburner state.