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Comment by Jeff_Brown | Hacker News Reader

Do drones really move fast enough to puncture a helicopter? If that's what happened, should they not have found at least some of the drone inside the helicopter afterward?

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Helicopters regularly cruise at over 120 mph, and the skin is around 1.27 mm thin. The stuff gets SHREDDED in a crash [1], it's generally not load bearing and acts as an aerodynamic fairing for the rest of the helo. The tail boom contains a truss space frame to do the literal heavy lifting. You see those "NO STEP" marks on commercial jet wings, because a human walking on some spots can cause damage. It's very plausible that a 5 lb rigid object (which is also how much a brick weighs), could do significant damage when striking skin at 100+ mph.

Add.: A better photo shows it's the leading edge of the horizontal stabilizer that was damaged: https://cdn.abcotvs.com/dip/images/5734793_120419-kabc-11pm-... The puncture location on the upper surface of leading edge corresponds with a nose-down pitch of the helo in forward flight.

[1] This is something I notice wrong in CGI aircraft crashes, where it breaks into big solid chunks that bounce. In reality, aircraft crumple, disintegrate, and smear into tiny pieces on impact, leaving a long trail of small debris.

> [1] This is something I notice wrong in CGI aircraft crashes, where it breaks into big solid chunks that bounce. In reality, aircraft crumple, disintegrate, and smear into tiny pieces on impact, leaving a long trail of small debris.

I recently came across a very good example of this, barely anything left. Scroll for photos: https://avherald.com/h?article=495997e2

Well the heli was moving too. Plus, the damaga is not that crazy looking. Totally believable

The damage is on the side of the tail. How fast can a helicopter move sideways?

Not as fast as they move forwards, but still pretty quickly[1]. I think 50mph is doable.

[1]: https://www.youtube.com/watch?v=WGp2okWpyJg

it can rotate, and thus sweep the tailaround, quite fast

It looks like it's the leading edge of the horizontal stabilizer, but it's not totally clear from the photo. A leading edge impact is definitely indicative of a forward flight collision.

Edit: Much better photo: https://cdn.abcotvs.com/dip/images/5734793_120419-kabc-11pm-...

Yes it's the h-stab. Upper surface of leading edge corresponds with a nose-down pitch of the helo in forward flight.

The closest example that comes to mind was done by the University of Dayton

https://giphy.com/gifs/48LkLrgh9AKmcFUVxe/html5

That simulated an aircraft's wing vs a drone at 238 mph. I was actually kinda surprised by the amount of damage inflicted.

If only the skin was damaged, what effect would that have on the ability to land a typical passenger jet?

Also, did that simulation mostly damage just the skin, or did it also get the machinery inside the wing?

Machinery inside. They simulated a bird strike too and found that to damage the internals less, so they suggested that future drone development might take that in to account and crumple closer to a bird strike.

I would think the object touched a rotor blade and got converted into shrapnel.

Tail rotors on helicopters move fast enough such that anything that touches it can puncture it.

Is that what was punctured?

The article says that it was the tail of the helicopter that was punctured; they don't say anything about a rotor. I was assuming by "tail" they mean the narrowest (fixed) part of the body toward the rear, not one of the rotating blades. The article includes a picture of the damage, but that's not clearing up the ambiguity to me -- it's not tapered like a tail, and it's too fat to be a rotor.

Looks like it hit and punctured the horizontal stabilizer rather than the tail rotor. Since this is a front-facing part of the helicopter it is quite feasible that the helicopter was moving faster than the drone, adding to the energy of collision.

There is a secondary vertical rotor on the tail, for yaw.

Ever seen a bird strike? And a drone is heavier than most birds.

I find it hard that a drone could puncture and dent a 3mm thick sheet of metal. Racing drones can move up to 100 km/h or so, but good luck hitting the moving tail of a helicopter at that speed.

Racing drone owners are generally very responsible, in my experience, and don't fly that far/high anyway. Photography drones don't go anywhere near that fast, and have altitude limits.

Photography drones have regulatory altitude limits. Nothing stopping somebody from flying higher than that other than the threat of a fine if caught. It's the relative speed of the two objects colliding that matters, not just the speed of the drone.

> Nothing stopping somebody from flying higher than that other than the threat of a fine if caught

And the built-in software limit that physically prevents the drone from flying higher.

And what ubiquitous built in software would that be?

You're aware there are myriad non DJI options for drone photography platforms yea?

"Software limit." On Hacker News. Used unironically. These are truly the end days.

Luckily that hasn't stopped people who know nothing about a subject from opining.

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