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Could a bird-sized consumer drone be digested by a jet engine, and not be recognized as a drone, mistaking it as a bird strike?

I'm thinking of the situation during the flight - like an engine making a short unusual noise, but works OK; not sure that can even happen eating a small bird?

As was pointed out, the debris of the object will look different in obvious ways when checking the engine after flight

I would assume a major factor is how the engine handles the drone, in terms of defects or running anomalies.

The battery comes to mind, hitting a turbine blade might be a problem - depending on the battery size.

There are certainly drones with very small batteries, that I assume will do no obvious harm, and certainly ones with batteries big enough to do harm for sure.

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    $\begingroup$ No. Engine bird strikes leave a lot of evidence, as would a drone. Post your edit - any drone going into a running engine is going to do damage. $\endgroup$ – Simon Apr 27 '15 at 15:12
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    $\begingroup$ Bird strikes leave bits of bird in the engine. Drone strikes wouldn't. $\endgroup$ – cpast Apr 27 '15 at 15:15
  • $\begingroup$ Good point - I was thinking of the situation during flight; Indeed there is a difference in what sticks to the exhaust edge - like lithium or liver ;) $\endgroup$ – Volker Siegel Apr 27 '15 at 15:16
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    $\begingroup$ @VolkerSiegel during flight all they know is "something is not right, land ASAP." They will probably not be asking "is it a bird, is it a plane", but may assume a bird strike unless they saw something different. $\endgroup$ – fooot Apr 27 '15 at 15:23
  • $\begingroup$ FYI, that "evidence" or "debris" from a bird strike is technically known as "snarge" The etymology does not bear repeating... $\endgroup$ – DJohnM Apr 28 '15 at 0:16
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A small drone, like those commercially available, is not much bigger than your average raptor or even a goose, but the material it's made of is much harder. Not very many geese have aluminum shoulders affixed with stainless-steel screws and supporting carbon-fiber wing struts. As such, a drone will do much more damage to the turbine blades (or the windshield or any other leading surface). This is one of the big reasons for current restrictions on UAV operations; current rules treat them similarly to model aircraft, and that means a ceiling of 400 feet and a no-go zone five miles from any controlled airspace unless you have comms with the tower for the space you enter.

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Would one be able to tell the difference before landing? Not likely in many scenarios.

Case 1: Bird hits windshield: blood & guts are immediately visible. Drone hits windshield, cracks are visible but not much else. The crew CAN immediately figure out, if they've ever see a birdstrike on the windshield, that this was something else. (Of course, it could just be a shattered outer pane -- those do fail sometimes, not necessarily due to any collision. Never had one go in flight, so I don't know if the sound of the pane shattering might be mistaken for a collision {or vice-versa}, or not.)

Case 2: Bird hits near the cockpit but NOT on a windshield. Sounds like a sharp crack, like a piece of gravel hitting your automobile windshield at highway speeds. If a drone did the same, it would probably sound pretty similar, and without the blood/guts to see (or not see), the ability to notice what's missing may not be there.

Case 3: Bird hits the engine, and it starts running poorly. Sometimes you will smell the guts cooking in the core of the engine (i.e. they get into the bleed air system & thus into the air conditioning), and that's a clear sign that your engine ate a bird. But the bird CAN miss the core and still cause problems with the fan blades. Most birds that miss the core are chopped up by the fan blades & the crew had no idea until after landing that anything happened, but a big enough bird can cause damage that way. So if the engine starts running rough, hot, and with some vibration, the absence of "cooked goose" odor isn't necessarily going to drive the conclusion that the collision had to be with something other-than-a-bird. One might suspect that a lot of damage with no smell seems unlikely to be a birdstrike, but there are cases where some engine component has failed & caused engine damage (ranging from barely noticeable up to catastrophic), and you can't really know much about causality for the engine doing what it's doing until you're on the ground.

Now, all of this assumes that the crew doesn't see the object that they hit. Which they very well might. Everything in that case is obviously an entirely different discussion.

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It's really dependant on 1) size and 2) type. I.E. if it's a DJI Phanatom, then it will just get shredded as its made out of plastic, possibly doing damage to the engine. On the other hand, if its a large multi rotor that's made of metal/carbon fiber, then the engine will most likely be damaged pretty badly.

So, TL,DR: if it's a consumer one, probably won't be much evidence, about as much as a bird, but with less blood. Of its large, then imagine a crane made of carbon fiber.

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  • $\begingroup$ I'm trying to visualize the contact of a small Li-ion accumulator with a 45 k$ titanium single crystal turbine blade... $\endgroup$ – Volker Siegel Sep 3 at 7:19

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