The X-56B unmanned aerial vehicle, which is able to suppress flutter, crashed during tests. According [...] to the NASA Armstrong Flight Research Center, it was damaged in flight as a result of an anomaly, but no details were reported. No one was injured in the accident, but the drone was destroyed.
Flutter is a self-excited, undamped self-oscillation of the aircraft structure that occurs when it reaches a critical speed. It is dangerous, because aircraft with the resonance of self-oscillations of the structure can collapse. The developers calculate the design of the aircraft so that the flutter occurs at a speed higher than the limit, but in a dive or in a strong wind, it can occur at lower speeds.
For the first time, aircraft designers encountered flutter in the 1930s: with the advent of new engines and propeller designs, the maximum speeds of aircraft were constantly increasing. After the development of jet aviation, flutter became the cause of a growing number of accidents. Today, pilots are taught techniques to prevent it, but they do not always work.
The program to create a drone that can suppress flutter started in 2005. The first two samples for NASA were built by Lockheed Martin. They were called X-56A and were designed according to the "half-wing"scheme. This is a variation of the flying wing, but with massive root inflows in the tail part of the fuselage. The X-56A wing is elongated, flexible and swept-equipped with large wingtips. They allow you to increase the lifting force at the end and reduce the vortex resistance that occurs when the air flow is disrupted.
The X-56A first flew in July 2013. In 2017, NASA decided to modernize the drone and equip all ten movable elements of its wing with position sensors. To track the movement of each section of the X-56A wing, 15 accelerometers were also installed in it.
In 2019, the X-56A tests were completed, and the X-56B was built to replace it. It has the same body as the X-56A, but different wings. The X-56B is made according to the "mixed wing" scheme: its fuselage is clearly defined and, due to smooth inflows, passes into triangular wing consoles. Flight tests of the X-56B began in April.
The X-56B crashed during testing on July 9. They were held at the NASA Armstrong Flight Research Center in California. Shortly after takeoff, the drone "collided with an anomaly" and fell to the ground. No one was injured in the accident, but the X-56B was destroyed. It is not known what this anomaly was and what caused it. It is also not specified whether NASA has other samples of the X-56B and whether the tests will resume.
While NASA is trying to suppress the flutter, the Brazilian company Embraer is working on a system for predicting it. It consists of a network of tension and pressure sensors and a computing unit. Earlier we wrote that its tests were recognized as successful.
Vasilisa Chernyavtseva
