Designing a new airplane is a time-consuming and methodical process. It took Boeing nearly a decade to design the 787, and it took Airbus nearly 15 years to design the A380.
Testing is one of the most time-consuming processes when developing a new airplane. The U.S. Federal Aviation Administration (FAA) requires new airplane designs to undergo rigorous testing before their first flight. Ground vibration tests, for instance, are necessary for airworthiness certification. Only airplanes that have passed a ground vibration test can be certified and, thus, authorized to fly.
What Is a Ground Vibration Test?
A ground vibration test is exactly what it sounds like: a ground-based test that exposes an airplane or aircraft to vibrations. Also known as a shake test, it’s typically performed in a specialized hangar.
During a ground vibration test, devices known as vibration exciters are attached to key points of the airplane, such as the wings, tail and fuselage. These devices will physically shake the airplane at varying frequencies. While this happening, a collection of sensors will record the airplane’s response.
Engineers use the data from ground vibration tests to map out patterns of vibrations across the airplane. In other words, they look to see how the airplane flexed and whether any part responded unexpectedly. If the test data differs from that of the simulation data, engineers can take action to make the necessary adjustments. Modifying the airplane’s weight distribution or dampening characteristics may fix problems identified in a ground vibration test.
The Importance of Ground Vibration Tests
Ground vibration tests are important because they ensure airplanes are able to withstand forces similar to those that they will experience during flight. Engineers typically use computers to simulate how airplanes will respond during flight. Simulations, though, don’t always align with real-world testing,. This is why vibration tests are performed. They mimic the vibrations and mechanical stress that airplanes will experience during real-world flights.
Engineers use ground vibration tests to predict flutter. Flutter involves the self-oscillation of an airplane. If an airplane’s own vibrations or “frequencies” interact with the aerodynamic forces to which it’s exposed in a particular way, flutter may occur. With ground vibration tests, engineers can identify potential flutter in a controlled environment so that it doesn’t happen in the air.
Of course, ground vibration tests are also necessary for certification. Only new airplane designs that have passed a ground vibration test can be deemed airworthy.
