How are Airplanes Tested?

Before a new airplane ever makes its voyage flight, it undergoes dozens of safety tests to ensure airworthiness. Engineers endeavor to put new aircraft through all the environmental stressors it will face as part of standard operating conditions, and in addition, they push planes to their limits by subjecting them to extraordinary conditions. This blog will discuss the various stress tests aircraft must undergo before holding passengers or cargo.

Anybody that has been a passenger on a flight before can appreciate the discomfort, if not fear, that comes with turbulence. While the cause and severity of turbulence can vary, the ability of the wings and the fuselage to withstand even the most chaotic turbulence events. In order to test the resilience of the wings, they undergo tests that make them bend up to 90° to find their breaking point under pressure. In the past, engineers would sacrifice entire wings by causing them to break, but digital systems can predict the breakpoint with current technology.

Since there are so few operational aircraft failures, manufacturers study each incident and build upon their tests to account for even more scenarios. One risk that has garnered media attention in the last decade is the threat of birds or water entering the engine. The FAA estimates roughly 13,000 bird strikes per year with an annual cost of $1.2bn in repairs. In order to evaluate the engine’s resilience in bird-related hazards, manufacturers conduct a test that might seem ridiculous to some: They load dead chickens into a compressed air cannon and shoot them at the running engines. This test is beneficial as the birds can be launched at speeds up to 350mph, reflecting the realism of such an occurrence in flight. The other obvious hazard that engines must fly through is a significant amount of water. To mimic this stressor, a continuous amount of water and hail are run through the engines to ensure they do not stall.

Modern aircraft fly in extreme temperatures and are sometimes forced to reach a very high altitude. The strain put on systems in these conditions is enormous and must be replicated in the testing environment. When testing a new design, manufacturers will bring the aircraft to places like the arctic that regularly have subzero temperatures and run through taxi and flight scenarios in the snow and frigid air. The landing gear and brakes are sensitive to these temperature and weather conditions and, as such, are tested here as well. As the gradient in air pressure between the fuselage and atmosphere increases at high altitudes, the risk for a violent decompression event becomes very high. If the airframe were to fail at a high altitude, there would be a sudden equalization of air pressure which would be devastating to passengers and components. Despite normally operating between 31,000-38,000ft, aircraft in testing are brought into simulation chambers that can mimic up to 100,000ft in elevation, allowing manufacturers to test the airframe durability at an extreme elevation. 

Airplanes are apparent targets for lightning strikes, and even though thunderstorms are avoided when possible, many planes are struck by lightning each year. Lightning could discharge an incredibly powerful current on the airframe and could be devastating if the aircraft were not designed to withstand it. Multiple safeguards protect aircraft against lightning strikes, and the first one is the hull itself. Modern aircraft skins are made from aluminum and composite materials that conduct electricity very well, and after lightning has passed through the hull, it will exit out an extremity such as the tail. This shell of conductive material is also the reason the passengers are protected. This protection method is similar to a “Faraday Cage” and is used in many different systems to protect against currents. Furthermore, the potentially combustible aircraft elements such as the fuel tanks and fuel lines are not positioned in places where lightning is likely to strike. Lastly, electronic components are designed and tested to withstand the effects of a lightning strike.

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1. sofia jonas
2. Posted on August 26, 2021
aviation safety