Researchers at Virginia Tech’s College of Engineering say drones as small as 8 pounds will have “devastating” effects if sucked into the turbofan engines of commercial aircrafts.
Computer-simulated tests showed an 8-pound drone would rip apart the fan blades of a a 9-foot diameter turbofan engine during take-off in less than 1/200th of a second. Furthermore, the tests discovered that drone debris thrashing about inside the engine could reach speeds 715 miles per hour and could lead 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,” says 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.
Bayandor and team started three years ago researching the impact of bird-strikes on commercial aircraft engines. However, their research switched to drones as news accounts surfaced of pilots spotting drones in commercial airspace. They’re now pushing for changes in how commercial aircraft engines are designed to prevent a potential disaster if a drone is sucked into a plane’s engine.
“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,” says 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.”
“The engines have to be designed and certified for foreign object impact, but I think now we have the definition of foreign object changing,” 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.
Currently, he said turbofan engines are designed to handle the potential ingesting of birds, hail and small runway debris such as tire fragments.
“We never—in the design of these systems decades ago—thought about an actual rigid object as big as a drone flying next to the engine and being ingested by it,” Bayandor said. “Today they can potentially pose a new type of threat altogether. It’s opening a new avenue in foreign object studies and understanding.”
Bayandor and Michael O’Brien, professor of mechanical engineering at Virginia Tech, said they also plan to study the effects of sUAS in a collision with a helicopter.
The computer simulation created by Virginia Tech’s College of Engineering demonstrates what could happen if an eight-pound quadcopter struck a nine-foot diameter turbofan engine of an airliner taking off.
According to the research, the speed of drone debris thrashing about inside the engine can reach speeds 715 miles per hour. Broken blades also create more fragments as the fan crumbles and warps the engine block housing, contributing to catastrophic engine failure.
“A jet engine is a very delicate system and the tolerances are minute,” Bayandor said. “If you introduce an unbalance to the system through the impulse that a drone brings with it and then cause even one blade to move a little bit off-center, everything around the shroud will be affected by it.
“The engine starts wobbling severely and then with the blades hitting back and forth to the wall of the casing, it causes even further damage—even though the main culprit might not have been the drone itself,” he noted.
The high velocity of the airliner times the mass of the drone generates the magnitude of the impulse. With the turbofan blades spinning at 2,200 RPM, the impact of the impulse creates shock and vibration throughout the system.
“We also showed that if that mass of the drone is substantial and you have a very heavy core with batteries and cameras then that, on its own, can cause more blades to break off and sheer off,” Bayandor said. “That causes even bigger deformation. The entire casing is now deforming into a shape that you can’t really recognize as a circular casing any more. What happens after that is that your entire engine gets stuck and you may not be able to get any thrust out of it.”
The research began three years ago computer modeling showing the effects of bird impacts on advanced turbofan aircraft engines. The engineering group’s efforts switched to drones as news accounts surfaced of pilots spotting unmanned craft in commercial airspace.
Bayandor and his team are exploring various methods that could be used to prevent more critical collisions of drones and aircraft, noting that engine failure rates and timing can change with different commercial aircraft and different relative impact velocities between the drone and the plane.
A product is currently on the market called Ping which can help preclude these types of concerns…and at the very least, make airline pilots aware of the presence of small drones. Ping is a miniature ADS-B. It’s slightly larger than a postage stamp and weighs 3 grams. It will fit on even the smallest drones, can be “seen” as far away as 20nm transmitting position and altitude, and can save drone power by only activating above 500 feet AGL or if the drone flies into controlled airspace. At less than $300, why wouldn’t every aircraft (manned and unmanned) want one?
This “PING” device would be a great asset but will it not overload the current “system”? Millions of new UAS are expected to hit the market in the next 2 months which would add considerable “noise” to an already taxed ATC system.
I’m not against it just tossing my thoughts out there.
Also at the same time to think that there would be NO possible damage to a Turbine Engine ingesting a UAS of anything but Micro is purely ignorant. These engines operate with such tight tolerances and anything with rigid mass (birds are sliced up pretty easily) will cause major damage and the turbine engine will quickly and catastrophically fail and basically destroy itself in a matter of 1/2 second or less.
aLLEN, I agree with your assessment that any object with a rigid mass will affect damage to a jet engine. It’s why we do FOD-walks at airfields. Regarding the Ping overloading the system, if it only transmits when the drone is flying where it shouldn’t be, it shouldn’t overload the system with clutter. Further, I would think an airline pilot would prefer “too much information” over “no information”. You have to wonder how many drones weren’t spotted by pilots. As I understand it, the Ping can also be used for “geo-fencing”. I think what the FAA would want to see is have them integrated directly into a drone’s operating system in a tamper proof manner rending the drone inop if one tries to remove it or bypass it (likely for devious utility).
Do you have a link for this product? I’ve never seen a transponder that weighs less than 300 grams. Are you sure it’s only 3 grams? That would have been newsworthy since Dianne Feinstein in California is proposing to have these things as a requirement on all drones – even paper airplanes. ::Rolls Eyes::
For the commercial use of drones, the ping system makes sense and is affordable enough that a serious commercial operator wouldn’t think twice of adding one to each UAS they operate.. The hobbyists however, are a different kind of drone or UAS operator , often assembling their aircraft from multiple components and parts.. And I don’t see them adopting the ping system unless compelled by FAA.. And that looks unlikely due to the FAA reathorization act of 2012 where congress included a law preventing the agency from promulgating new rules on model aircraft operators.. But we will see.. The mood in congress has changed and so might the laws in order to protect the national airspace.