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.”
Any type of screen is not practical - low density mesh or otherwise:
Disrupts airflow into the engine, and if damaged, the mesh becomes ingested debris itself, making the potential damage even greater.
I dont understand why they dont fit low desity mesh over intakes to deflect larger debris or objects.
Kind of glad this simulation was done. I'm really getting tired of hearing people compare a "Bird" to a "Quad". How many "Bird" species do you know of that have aluminium bones? Or Lithium-ion polymer stomachs that can burst into flames when pierced?
ANY debris into a jet engine is bad. Period! The only argument I will give in to is the probability argument. What are the chances, etc.. But hey, if you like to take a chance every time during take off, so be it. I prefer one less statistical variable on my way to my vacation during take off.
Not sure why this is such a hot/sore topic with the media and cowboy drone enthusiasts. I guess it's the entitled culture we live in. And it's the few rare, bad apples that are ruining it for the rest of us. Maybe we should put more effort into educating them, so that they don't give the media more fodder.
Going to go play with my "quad" in a safe and quiet area, preferably not near an airport or above cars and people. #CommonSense #DoYouReallyNeedToBeTold?
GE used to test their engines by throwing frozen chickens into them, surely that would do more damage than a quad. John is correct though it will never be a good idea and the problem is the people who are deliberately flying near aircraft (eg. hovering near airports). On the bright side unlike a flock of birds there are highly unlikely to be multiple uavs in the same place at the same time so multiple strikes taking out multiple engines are far less likely.
Well first I agree - FOD and aviation in general not a good mix.
Also, I liked the research done earlier posted here that probability of UAV meeting the Airliner is 1 in 1.8 million years, which I believe is very close to truth.
In 70+ years of RC and model aviation how many lives were lost?
It is much more dangerous to buy a brand new car where they factor-in a calculated risk for every part (instead of making it better) as it is cheaper to buy an insurance then making a car safer. Remember Toyota run-aways a few years back.
Now, this Government funded research company (calling them a smart folks) telling general public what to believe.
I am talking to my neighbor asking him what he thinks about drones - the answer is: "The should be banned everywhere because one can drop a bomb on a neighbor.." - I did not think I needed to continue the conversation.
We need educated people to run the industry and sometimes we get quite an opposite.
It is interesting with the hype that has surrounded the drone in the jet discussion that apparently not one engine manufacturer, the FAA or the military seems to have actually felt compelled to give it a try.
Hell give me a flame suit and a good exit point and I'll even be happy to toss the Phantom in the intake.
(And run like hell!)
I do suspect all will not end well for either the Phantom or the Engine.
Guys, the entire 'will a quad damage the jet engine' question is an circular logic argument that only helps solidify the perceived danger of drones in media. Don't play into it.
Solid objects aka FOD, should never enter turbine engines. End of that discussion.
The only real question is, how likely is it that a quad will get sucked into a jet engine. And how does this danger compare to other already established threats like bird strikes etc.
@ Mike i do agree.
I know early days (70's) pratt and whitney engines kept running for 24 hrs on full power with rock and ash thrown at them. I have a very hard time believing that my quad is going to disable a commercial jet engine..
Having looked at some of Dr. Byandor's work in some detail, it is apparent that these simulations leave a great deal to be desired. First, the materials being used to represent multicopters have a great deal more steel and non-flexible plastic in them than what is really the case. In addition, the batteries were assumed to be very rigid objects, which Li-Polys are not. In some of his simulations the collision geometry used was physically impossible. In others, he was using over 700mph as the collision speed, failing to indicate that the only time a commercial airliner can get anywhere close to that speed (most can never go that fast) is at altitudes of around 40k ft. Finally, it needs to be said that precisely NONE of the simulations run have, in any way, been validated with real test data of any kind.
I recall one of GE's commercials/ads were touting that a GE-90 swallowed a step ladder whole and kept running. (I suspect while it may have kept running, it was damaged enough to take it out of service until stuff got replaced.) I think the notion that a predominately foam and/or plastic airframe, whether fixed-wing or multicopter, really doing significant damage to a large commercial airliner is laughable. That having been said, what the community as a whole needs actual, physical, testing of sUAS vs. various airplane parts. Problem is, particularly with large commercial airliner engines, is that it would be really, really expensive, particularly if you do end up breaking something.
Unfortunately, pseudo-science like this feeds into the media-hyped "danger of drones" nonsense.
Irresponsable people are not going to stop with any law, responsable Rc pilots are the only complicated :(