Suffice to say it doesn't end well, for drone or engine. Why did the researchers use an 8-lb drone, when the typical drone weighs less than half that? The researcher responded:
"This is the drone size that one European country has sanctioned for their postal services to deliver packages to high altitudes. The work is not based on any organization’s request. We are able to model a variety of different drone sizes and models. We chose this model as a demonstrator, because it was one of the larger size commercial drones available that is capable of carrying large weights and reaching higher ceilings."
Excerpt from the full story:
...The smart folks at Virginia Tech’s CRASH (Crashworthiness for Aerospace Structures and Hybrids) lab have been working hard to answer these questions. Founded and directed by Professor Javid Bayandor, the team at the CRASH lab’s latest endeavor has been to build simulation models for turbofan engines, drone components, and basically smash them into each other to see what happens. From a Virginia Tech press release,
An 8-pound quadcopter drone can rip apart the fan blades of a 9-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 715 miles per hour. Broken blades also would create more fragments as the fan crumbles and warps the engine block housing, contributing to catastrophic engine failure.
So there is little doubt that a drone of this large size would cause catastrophic engine failure. This sort of damage would be consistent with the type of damage that occurs regularly with a ingestion of a large bird. However thanks to FAA standards for aircraft engine design, the failure and detachment of a rotor blade is anticipated, and must be contained within the engine. Failure to contain a blade could obviously lead to other damages, from structural parts, to fuel tanks, electrical controls, or even death or injury. It has happened on older designs, such as Delta 1288, a MD-88 that failed and engine parts entered the passenger compartment, killing 2 (this was a 1963 designed engine).
An 8 lb drone is not the type that one would get for Christmas and be used by a younger, less responsible person however. Without crunching the numbers, I suspect a smaller DJI Phantom sized drone at 13″ and 2.6 lbs would be more likely to be the first to actually get ingested into an engine. The Phantom seems to be the ‘go to’ drone for people first entering the hobby, and is most likely to be operated by those without any real knowledge of airspace or air safety.
Our plans are to study a full array of drone sizes, with different materials, weights, and configurations.
adds Professor Bayandor. Materials is also one of the topics that the CRASH team is studying. Currently, “The drone is composite, but the core is made of denser metal alloys.”. As we know, drones built from carbon fiber and alloys are not the only type we will see. Google has previously demonstrated a delivery drone in a wing form, made primarily from foam.
However, he adds, “In this early stage of the study, it seems that battery packs and on-board cameras can cause most damage. ”
I posed the question of what materials are likely to cause the most damage to the turbofan engine? Carbon Fiber tubes and plates, aluminum parts such as motor shells, circuit boards, LiPo battery packs? Professor Bayandor reports, “At this point, we are still formalizing our material modeling matrix, but the materials mentioned are among the general candidates considered.”