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Comment by ars | Hacker News Reader

It made a hole and caused internal damage. But would not have taken down the plane.

Recommendation to make drones "frangible", so they break on impact and do not penetrate into the wing.

In comparison a bird crushed the wing surface but did not cause internal damage.

The drone penetrated the wing and broke spars. It is very easy for such an impact to also destroy control surface cabling, wiring, or hydraulics which certainly can cause a plane crash.

Dented the front spar and some compression members. It probably reduced the wing's margin for maneuvering, but should still have been manageable to get down safely. Not to downplay the danger, but let's not exaggerate it either.

What if the drone was heavier or impacted somewhere else more critical? Drone is pretty much a mini aircraft so it has to be regulated somehow.. which i believe is being done already!

I am not exaggerating. Several years ago, a bird strike in Alaska resulted in a fatal crash of a 172. Does it happen often? Probably not, but a large heavy drone can easily take down a small civilian aircraft.

I'm just pointing out your exaggeration of the result of this test, not the danger in real life, which I believe you assess accurately.

That was enough to take down a plane easily. Wings don't just sit there on the ground like in the video, they support the fuselage of the plane against serious aerodynamic forces.

They are under load, it's like taking out a bunch of columns at the ground floor of a building. Not to mention that wings are full of fuel, as well as the cables or hydraulic lines connected to the control surfaces.

The engineer that conducted the test concluded that the plane would have been able to survive the impact. However, he said that if the test were conducted on a faster aircraft like a business jet, the results could be worse.

Realizing I should go watch the video, did he say at what height it would be recoverable?

For example, there's been at least one high-profile plane crash in the past (Lauda Flight 004) where a thrust reverser (diverts the jet output forward instead of backwards, used to slow you down quick during landing) deployed mid-flight. That should have been recoverable, but turns out Boeing only projected outcome at low speeds and altitudes. The outcome at cruising speeds/altitudes turned out to be far different and the plane went down.

While cruise wouldn't be an issue (don't think they get up that high!) I'd expect the outcome of a drone hitting a flight control surface might vary between takeoff, landing, and lowish-altitude holding.

You’d be shocked how little of the wing is actually supporting the entire structure. Typically there is one main spar that holds up the entire wing and the skin and ribs only hold a fraction of the load which is distributed to the spar. As you might imagine the spar is going to be a pretty heavy duty piece of aluminum and not easily damaged by something like this. A wing can sustain a fairly large hole as long as the spar isn’t damaged.

Control cables would be a concern but hydraulics and fuel aren’t typically going to be a concern. Fuel isn’t as combustible as everyone likes to think. There are also additional tanks. Hydraulics offer redundancy on aircraft that use hydraulic control surfaces.

I’ve seen a Cirrus SR20 hit a deer at takeoff speed and leave a 2.5 ft hole in the skin of the wing the went as deep as the reinforced fuel tank. The aircraft continued flight and came back around and landed just fine. Even flew to the repair airport after cleaning up some loose fiberglass.

Personally what worries me more is what would happen if they fired this thing at the plexiglass windscreen. In a GA airplane that would likely be fatal.

Now also imagine the drone hit the windscreen, and not the wing. Or went into the prop / engine. Or hit the tail and damaged the rudder.

The leading edge of the wing is likely the best case scenario. All others probably result in far more serious consequences.

Wings also hold fuel, so it can catch on fire.

We're looking at a collision between a big kerosene-tank and a fist-sized Li-Po battery.

Yeah... the fuel in many GA aircraft is usually inside of a relatively thin rubber bladder inside the wing. It does not self seal. If it leaks, it’s going to run down the back of the aircraft and may drain into the cabin. In some aircraft with engines mounted on the rear of the aircraft it can run towards or into the engine.

Now, on top of dealing with an emergency that has disabled control surfaces like ailerons and flaps that pass through the inside of the wing, damaged the leading edge which is critical for generating lift, and potentially having a wing come off if you hit a rough patch of air with a damaged spar, the pilot may have to deal with a fuel leak that would endanger the people in the cabin or cause a midair fire.

Not good.

Most piston aircraft run on gasoline, which is far more flammable than Jet-A/kerosene.

Sounds like a fun time.

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