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Engineers seek remedies for threat posed by drones

01 November 2015

Increasing use of drones poses a threat to passenger aircraft safety, and engineers are now seeking changes in turbofan engine design to mitigate this threat.

Researchers at the Virginia Tech College of Engineering have created computer animes of what would happen if a drone were pulled into a commercial airliner's turbo fan engine block (image courtesy of Virginia Tech College of Engineering)

Virginia Tech researchers are urging changes in how commercial aircraft engines are designed in the wake of a possible new threat to passenger aircraft safety: the likelihood of drones, or unmanned aerial vehicles, being sucked into turbofan engines at high speeds.

Such an impact – be it unintentional or part of a malicious act - would be devastating to the engine as its blades are ripped to shreds after 'ingesting' the hard-shell centre of a drone’s electronics housing.

Computer-simulated tests completed by researchers at Virginia Tech's College of Engineering show that an eight-pound quadcopter drone can rip apart the fan blades of a nine-foot diameter turbofan engine during take-off in less than 1/200th of a second. The speed of drone debris thrashing about inside the engine could reach speeds of 715mph. Broken blades would also create more fragments as the fan crumbles and warps the engine block housing, contributing to catastrophic engine failure.

“Because the damage is spread to a large section of the engine, it is unlikely that it will be able to maintain thrust,” said Javid Bayandor, an associate professor of mechanical engineering at Virginia Tech and director of the university’s Crashworthiness for Aerospace Structures and Hybrids (CRASH) Laboratory.

Work originated three years ago with Bayandor's group computer modelling advanced turbofan aircraft engine impacts by birds. The group’s efforts switched to drones as news accounts surfaced of pilots spotting unmanned craft in commercial airspace.

“Because of the unprecedented damage a small or even micro unmanned aircraft systems can inflict on a passenger aircraft, pilots cannot risk flying in the same airspace where there are drones,” said Bayandor. “While strict regulations are already in place to isolate drones from operations in controlled airspace, their enforcement have proven challenging, due to the anonymity of drone users.”

US Federal Aviation Regulations require commercial aircraft to adhere to design criteria that help ensure the aircraft’s survival after a midair collision with smaller 'soft' airborne objects, such as birds. However, little investigation has been conducted on the ingestion of drones into larger engines.

Bayandor and his team are exploring various methods that could be used to prevent more critical collisions of drones and aircraft. The team notes that engine failure rates and timing can change with different commercial aircraft and different relative impact velocity between the drone and the aircraft.

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