What Would Actually Happen If a Drone Hit an Aircraft

There's a been a lot of back and forth in recent years about the risk drones pose to airplanes and the type of damage they could possibly cause if an impact were to occur, but little true research has been done. This video follows a research team that used an air cannon to fire a drone at an airplane wing to study the damage that occurred.

Coming to you from Aviation International News, this interesting video shows a research project that aims to investigate the sort of damage that a drone might cause to an aircraft. Whereas a lot of the focus has been on a possible collision with a large jetliner, smaller general aviation aircraft aren't always anywhere near as rugged and could possibly be at substantial risk if they were to experience an impact with a drone. As the researchers mention, their solution is to build drones to break into fragments in such situations to reduce the impact damage. Of course, that likely wouldn't please drone owners would wouldn't want their expensive equipment shattering in other more routine impacts, but if it were to prevent a major accident, I would certainly be all for it. 

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29 Comments

Michael Rapp's picture

The wings and fuselage, even the windshield aren't the issue.
The main problem is the engine air intake!
Some of the blades go at supersonic speed with very little play in the workings. Tossing in a few pounds of hardware is bound to cause some damage.
Worst case, it causes an engine to stall during takeoff - fully fueled, just off the runway and not enough altitude to hunt for landing sites.
But, even in best case, the plane and the engine are grounded for an overhaul and check. Which has no problem running a 5 digit tab.
So don't worry about the wings, think engine instead.

Those engines are designed to take a turkey in and not bring down the plane. I don't see why the drone should be more dangerous apprt from it's increase occurence around airport (if that's actually true to begin with..).

The engine can be taken off and another one put in to let the plane keep going with minimal down time.

Can't do this with a wing.

None of what you said is actually a concern or as big a concern as you think.

Davide Zerilli's picture

Funny enough I’ve asked the same question to an engineer that works on jet engines and to an army helicopter pilot as well. Guess what? Both pointed out that a turkey has nothing made of steel/iron etc.
A supersonic turbine will ingest and probably destroy little empty bird bones into pieces. While a single screw, would actually bounce around and probably destroy everything and cause a disaster to the engine. It’s just not designed to substain a hit by little metal shattered components.
This doesn’t means it’s a bigger or less important damage in comparison to a wing hit. It just is a different damage.
Have a look, in this simulation it looks like it could actually explode completely... an airplane can maybe fly with one engine only, I doubt it will fly with 1 wing only or without a portion of tail:
https://m.youtube.com/watch?v=4773V-bEboY

https://www.economist.com/gulliver/2018/01/26/why-drones-could-pose-a-gr...

One link is a simulation the other uses "could" in the title. Hardly evidence that a wing would explode if a drone got in the engine...

Davide Zerilli's picture

Just to point out that it is quite a concern indeed, no one wants a burning engine on a people carrier with hundreds of souls in it...

One engine isn't bad. 2 is disturbing but very rare and still flyable. A third one is extremely rare but the plane will still land (If the plane has 4 to begin with obviously...).

Just look at how infrequent these are on wikipedia... Only 1 (US only stats) in 2016 out of how many flights in and out of the US?

Davide Zerilli's picture

Ok you’re right, it’s not a problem, it’s not a big concern. They will just turn around, extinguish the fire, take out the poor dead passenger (one of the last time an engine exploded in an airplane, it landed safely a part for the poor 7 people that died) swap the many m$ engine with the spare one and off they go. Not a big concern. But don’t, don’t hit the wing, that would be a real concern.
I’m just saying that I can’t possibly understand how you can state that a drone in an engine is not a problem, just a big turkey.
Even when it gets shown to you that actually iron parts will be way worst than fragile bird bones, (by the way this can be seen also in the wing video) you still say that it’s just a simulation and it’s not evidence (and therefore still not a concern?). Ok, what do you want me to answer, you’re right, completely right. Not a concern at all.

Davide Zerilli's picture

https://www.nap.edu/read/6265/chapter/5#26 Read and get to the point with graph showing statistic, one of the biggest cause of accident is indeed engine failure. Sure it’s not a hull loss, but many times it involves injuries and deaths.

Alex Cooke's picture

Every commercial jet in the world is designed to take off with one engine inoperative.

Michael Rapp's picture

Especially commercial jets, true. Smaller Lear Jets - let's just say I woudn't be the happiest passenger riding in one.
But even the bigger RR engines would require service after a bird impact.
Also, brids don't pack a quater pound of Lithium Ion blocks, which also may react funny when exposed to air.

I'm guessing you didn't watch the video.

Michael Rapp's picture

Did. But I was leaning towards the fact that most of downed commercial airplanes are due to bird strikes into the engines and less to the leading edges of the wings.

So let me get this right, you watched it and still said "the wings...aren't the problem". Bearing in mind the speed was intended to simulate the rate of closure of a recreational aircraft.

There is a famous statistical analysis during the war that proves your reasoning is flawed.

Basically bombers were coming to base riddled with holes and mechanics were reinforcing the places where bullet hit. But (I can't remember the name) one mathematician propose to reinforced zones that weren't hit since evidently the bombers that were hit there didn't come back.

It worked.

So while most airliner get "downed" because 1 engine was damaged, it doesn't mean this is the main point to focus on for safety and reliability.

I'm guessing you don't work anywhere near planes or engineering.

Alex Cooke's picture

Abraham Wald.

Michael Rapp's picture

Wrong guess. Long history of ppl flight and some time in helicopter maintenance. Now running a cnc machining shop.
And yes, I do remember that riddle/ statistical analysis propbelm. But your argumentation is flawed, too, since this problem was from ww2, with no flight records whatsoever, those planes came back or they didn't
So fault analysis was pretty much guesswork.
btw, I love quoting that example too, for advanced problem solving skills.
But I digress. With current bird impacts it is known what kind of bird hit what engine at precisely what time.
And with "downed", I don't mean "lost", I use that word to indicate that the plane wasn't able to carry out its flight according to its flight plan.

Problem is, newer airliners are made of carbon fiber. Even older airliners have carbon fiber critical components.

The reason bombers returned is because older aircraft are made of spars which have sheet metal (aluminum) covering those spars. The strength comes from the spars/frame, not the actual skin. If something were to penetrate the skin in a non critical part, nothing would happen.

Regarding the wing, keep in mind that the majority of fuel is stored in bladders in the wing. Literally potentially tens of thousands of gallons.

Michael Little's picture

I'm just curious. Where did you get your information that most down aircraft are due to bird strikes? Did I read that correctly?

This is the list of the 5 most common reasons that commercial jets crash and bird strikes isn't one of them...

http://theconversation.com/the-five-most-common-reasons-for-airliner-dis...

Michael Rapp's picture

My bad. I missed out in pointing out "in between fuselage strikes and engine strikes." As far as I know, no commercial airliner has been forced to land after a fuselage bird strike, but I kind of remember that tere is an upper limit as to how many bird strikes an engine is cleared to take before having to undergo a major inspection.

Michael Little's picture

I figured. Thanks!

As indicated in the video, this study was done on light aircraft, generally piston engine powered, which do not have the engine air intakes that turbojet and turbo fan aircraft have. Piston engine aircraft have much smaller engine air intakes, many of which are shrouded behind a cowling or structure.

The wing tested, A mooney M20 wing, is a substantial sheet metal construction that has a cruise speed of around 200mph, the speed used to do this test. The reported impact, and the images, report that the wing structure, including the wing main spar which suffered buckling, was damaged. The spar is the main structural member of the wing, and any buckling to it in flight has the potential of causing catastrophic structural failure in flight. The aircraft seats 4 people, who in all probability would not survive such an in flight failure of the wing.

Also, as indicated in this clip, the impact force squares with speed, a 1lb drone at 200 mph has a force of almost 200lb, A larger aircraft traveling at twice this speed get hit with around 200lbs squared [200 times 200 = 40000], you do the maths for that impact on a larger aircraft. would you want to be a passenger in an aircraft that struck a drone with such force?

The issue is with drones operated illegally. not with drones themselves. If your drone operation is done legally then what is the issue? If you think the regulations do not apply to you, then there is probably no point entering a conversation with you in the first place.

I have worked in the aviation industry for many years and have repaired many aircraft that have struck birds, suffered hail damage and experienced accidents. Damage to a wing like in this video would probably cost so much, this aircraft type would be written off if it survived the flight. If the drone struck the windscreen of a light aircraft, it could cause serious injury or death to pilot of passenger as the windscreen is a thin plastic material, not a bullet proof shield that commercial aircraft that fly at high altitudes have.

David Pavlich's picture

There's other factors as well. We know that a commercial airliner can ingest a bird into one of its turbofans and continue to fly without a flame out, however, when that happens, the engine is required to be dismantled to ensure that no damage was done to the internals.

Same goes for a prop strike on a general aviation aircraft like a Cessna 172. If there is a prop strike, the engine has to be torn down to ensure that the crankshaft hasn't been damaged. The prop is connected directly to the engines crankshaft of the majority of piston engined aircraft. While Delta can absorb an engine tear down easily, the owner of said Cessna 172 might have to park his plane until he can get the cash to do a tear down. It's not cheap. It has to be done by a certified mechanic which you won't find at your local Canadian Tire.

The crux of the matter is that 99% of drone owners are or will be responsible pilots. It's that 1% that screw it up for everyone else....typical of this sort of thing.

If you want to keep this in check, make the first offense of flying a drone in protected airspace a $50,000 fine and 5 years in jail, period.

Excellent points, all, but I kinda doubt your 99% claim. Certainly a majority but 99%? Doubtful.

Michael Rapp's picture

No need. Just make license plates mandatory (like cars) and send them the repair bill. Although, most would settle for the $50K fine.

That I agree with you. Registration and insurances.

Normally I just passively read post, but as an airline captain (airbus a350), I thought I'd chime in.

I highly doubt a drone could bring down an airliner, but perhaps a small general aviation aircraft, or more so, helicopter. Not enough studies have been done yet, but surely parts on a drone (metal electric engine) are much harder than tests done with birds. Bombardier accidentally tested windshields with frozen turkeys which went clean through windshields.

I can imagine a metal electric motor of a done being much harder than parts of a bird - more akin to a bullet. Imagine that hitting a windshield or any other part of the aircraft!?

Aircraft above a certain weight (airliners) are certified to take off and climb with one engine failed (twin engine aircraft). While a over $30 million USD engine may be written off, the flight would be ok. However, therein more plausable problems arise, such as a potential catastrophic engine malfunction happening before it's shut down (and systems isolated), leading to an uncontrolled fire (extreme scenario (you could also be hit by lightning) but possible).

What happens if a damaged part (ie - engine part), falls to the earth and hits someone?

What really concerns me is the callous attitude many individuals have towards flying drones dangerously. More education is required, in addition to strictly enforced [severe] laws. Why are we always swinging for the extreme? ie - someone has to die. The collateral cost alone should warrant swifter action, and more responsibility.

There has to be some type of [better] licensing and tracking system for drones. It's as simple as that. Right now it's the "wild west", and while there are laws, which are enforced, the enforcement part gets very difficult considering any "Joe" out there can go out and buy a drone, to fly virtually anywhere.

Matt Rennells's picture

First of all, I have a BS of Aeronautical Engineering from Purdue -- just for background. This test is not indicative of what would happen if a plane in flight struck an unmanned aerial vehicle. In this case, the drone is moving rapidly and the airplane wing is not moving. In reality, the wing would be moving and disturbing all of the air around the wing and the chances of a drone hitting it exactly square like this is almost impossible. In subsonic flight, there is a large region of high pressure air just in front of the wing than then is rapidly accelerating either up or down over the wing. The chances are that a drone in flight would have more of a glancing blow and be deflected above or below the wing. As well, this region of pressurized air would cause a massive shift in the attitude of the drone so that it would not strike square like this. As that pressure hits one propeller of the drone, it would cause it to pitch violently and more likely be deflected by the wing. I can go through the physics of it, but the "real world" example would be of trying to cut something by throwing it at a knife instead of slicing through it.

Also, you could think of an airplane like a human body. There are regions that are more critical than others to damage. This impact was in an area between the ribs of the wing and the center of mass of the drone appears to be perfectly aligned with the centerline and angle attack of the wing -- the worse possible scenario and highly unlikely.

Very insightful in theory, but in reality it's quite different. There are bird strikes all the time on leading edges of wings, engines and pretty much every part of the fuselage. I've experienced this first hand. These bird strikes are also at altitudes that drones may be flying. While you're points are valid, the comprehensibility of air is just not enough.

To take it a step further, smaller, more dense objects such as hail have also struck aircraft, and not necessarily in mass quantities.

Valid points though.

alan christie's picture

"actually"