Drone hit a news helicopter

[Deleted member 109934]

This should help....

(Not my calcs I'm copy/pasting from a post on another forum from @sar104 )
*********** Start Quotation ************
Take an arbitrary helicopter - I'm choosing a Sikorsky UH-60, which has a maximum takeoff weight of 10,000 kg and a rotor diameter of 16.4 m, sweeping an area of 211 m².

To support its weight the downthrust has to be 100,000 N, and so the downward pressure below the rotors needs to be of the order of 500 N/m².

The cross-sectional area of a Phantom is around 0.25 m², and so the downward force on the Phantom would be, at most, 125 N.

Acting on a mass of 2 kg, that will yield a downward acceleration of 62.5 m/s².

The UH-60 flies at 150 knots (78 m/s), and so the time taken for even a stationary Phantom to pass the 16.4 m under the rotors, front to back, would be 0.2 s.

Applying the standard equations of motion, vertically, to the Phantom, it will be deflected downwards by 1.4 m in that time, not even nearly the height of the aircraft.

But, since the fuselage is positioned such that only around one half the length of a rotor blade extends ahead of it, the time that an incoming Phantom would be exposed to the downforce before striking the aircraft would be roughly one quarter of the estimate above - i.e. 0.05 s. In that time the deflection will be around 7 cm. Barely noticeable - it's still hitting the windshield.
*********** End Quotation ************

Did it hit the windshield? Damage on photos was to the stabilizer all the way at the back, according to the above calculations it would be impossible deflection would be much stronger.

 

[BigAl07]

Did it hit the windshield? Damage on photos was to the stabilizer all the way at the back, according to the above calculations it would be impossible deflection would be much stronger.

No it struck the hoz stabilizer and tail rotor but I was quoting from another thread depicting how the rotorwash would not merely deflect a UAS where-by keeping it from striking the helicopter.

 

[sar104]

Did it hit the windshield? Damage on photos was to the stabilizer all the way at the back, according to the above calculations it would be impossible deflection would be much stronger.

Those were rather back-of-the-envelope calculations but agreed - if it passed completely under the main rotor then the deflection downwards should have been greater. Whether it is actually enough to prevent a collision with the rear stabilizer is not completely clear.

 

[25Vettes]

The issue here is not where the helicopter was hit or whether it could have been affected by the main rotor downforce.
The issue at hand is that it IS blamed on a drone and that puts the burden of proof on anyone that tries to discredit the accusation. If they DON'T find debris, the investigating agency will most likely leave it classified as a "possible" drone strike and most readers will omit the word "possible" when judging what happened.

 

[sar104]

The issue here is not where the helicopter was hit or whether it could have been affected by the main rotor downforce.
The issue at hand is that it IS blamed on a drone and that puts the burden of proof on anyone that tries to discredit the accusation. If they DON'T find debris, the investigating agency will most likely leave it classified as a "possible" drone strike and most readers will omit the word "possible" when judging what happened.

There has been no official blame apportioned. The news station that owned the helicopter stated that they believe it was a drone. That's their opinion, based on limited evidence, and they are entitled to it. The readiness of the general public to accept that explanation is due, at least in part, to the bad press that some drone pilots have, quite reasonably, attracted and a more widespread nervousness about flying cameras. It goes with the territory, and there is little point simply lamenting unbalanced news coverage. The LA Times reported the incident, accurately enough, as a possible drone strike.

 

[Capt KO]

Not UAS it’s a UFO. My guess is as good as there’s.

 

[Mavic Mac]

Any object hitting a helicopter is going to cause significant damage. The size and speed of the object hitting the helicopter are immaterial, when compared the helicopter. The size and speed of the helicopter are what determined the amount of damage. It's purely an exercise of F = m * v.

WOW !! The pictures in the link are amazing

 

[R. Howard Trembly]

If it was a bird strike there will be evidence where it hit the aircraft, I know from experience. In 1973 I was flying home to Salem, Oregon at around 8 pm in a Mooney and as I got closer I told my passenger to look out for geese over the river after I turn my landing lights on, just before making a 45 degree descending approach to downwind for runway 34 at McNary field. My passenger said " geese don't fly at night." (He wasn't the brightest thinker) He hardly got that out when in an instant there were a flash of three geese ahead of me. They tried to get away and died trying. The impact rocked the plane and immediately flames started pouring out of the engine compartment (The tower, after I called in the emergency, said the flames were trailing about sixteen feet behind the plane. I made a very short midfield landing, and as soon as I shut down the engine the flames want out. One of the geese had wound up in the engine compartment and broke the primer line and the gas pouring out acted like a torch until the gas stopped flowing. The next morning I went to the airport to inspect the damage. The leading edge of the wings were un-dented but there was goose guts over the top of the wings. If you think Gorilla Glue is strong you never had to clean goose guts off a wing. So what I'm saying, if it wasn't a drone but a bird strike, there will be plenty of evidence to show that fact.

 

[pftarch]

As much as I don't WANT it to be a drone, the scuff marks sure look like something hard dragged across the stabilizer. I agree that it doesn't look like a bird strike at all because of the lack of gore. I'm curious about the deep puncture to the right of the big scuff marks. Anyone here good at judging the scale/distance between the puncture and the scuffs?.

I ask that because to me it looks like the puncture (which appears to me to have been caused be something/part small and hard, i.e. motor/battery) is a fair distance away from the scuff (which to me appears like the body of a drone).

My initial thoughts are that it was a fairly big drone based on the distances, (but who knows what kind of craziness happens at high speed impact). To my untrained eye it appears that some part that was hard and dense (like a good sized motor) entered/made the clean puncture and the rest of the drone followed to left making the scuff. But, if my sense of scale is right it would have to bigger than a Phantom to do that.I am assuming that the stabilizer was the first contact for this to have occurred. If the drone smashed into something forward of the stabilizer and pieces were strewn to the rear the damage pattern could be anything, but I didn't see any pictures of damage forward of the stabilizer.

Any thoughts from the group?

Again, I don't WANT it to be a drone strike, but it sure looks like one to me.

Peter T.

 

[Deleted member 109934]

not a drone, not a bird... could it be one of Santas gifts fell of the sled? After all, Christmas time is coming. If we don't want to upset old man, let's blame it on the elfs.

 

[sar104]

As much as I don't WANT it to be a drone, the scuff marks sure look like something hard dragged across the stabilizer. I agree that it doesn't look like a bird strike at all because of the lack of gore. I'm curious about the deep puncture to the right of the big scuff marks. Anyone here good at judging the scale/distance between the puncture and the scuffs?.

I ask that because to me it looks like the puncture (which appears to me to have been caused be something/part small and hard, i.e. motor/battery) is a fair distance away from the scuff (which to me appears like the body of a drone).

My initial thoughts are that it was a fairly big drone based on the distances, (but who knows what kind of craziness happens at high speed impact). To my untrained eye it appears that some part that was hard and dense (like a good sized motor) entered/made the clean puncture and the rest of the drone followed to left making the scuff. But, if my sense of scale is right it would have to bigger than a Phantom to do that.I am assuming that the stabilizer was the first contact for this to have occurred. If the drone smashed into something forward of the stabilizer and pieces were strewn to the rear the damage pattern could be anything, but I didn't see any pictures of damage forward of the stabilizer.

Any thoughts from the group?

Again, I don't WANT it to be a drone strike, but it sure looks like one to me.

Peter T.

That's a Airbus AS350 B2. The rear stabilizer is about 1 meter in length. The distance between the dents and the hole is around 15 cm. For comparison, the diagonal size of a Phantom 4, motor to motor, is 35 cm.

 

[pftarch]

That's a Airbus AS350 B2. The rear stabilizer is about 1 meter in length. The distance between the dents and the hole is around 15 cm. For comparison, the diagonal size of a Phantom 4, motor to motor, is 35 cm.

Well, the stabilizer is smaller than I thought it was. (And, if my math is right, a Phantom motor/prop/frame arm leading the impact and puncturing to the right, followed by the rest of it bumping/scraping/dragging to the left might very well be possible) In addition, even a Mavic with arms extended could do the same thing, but I would think the prop arm would snap before it made that big of a puncture. Of course I'm not going to buy an Airbus AS350 and fire MY mavic into it's stabilizer just to be sure, so I'll leave it to investigators to make the call.

Thanks for the info SAR.

Peter T

 

[sar104]

Well, the stabilizer is smaller than I thought it was. (And, if my math is right, a Phantom motor/prop/frame arm leading the impact and puncturing to the right, followed by the rest of it bumping/scraping/dragging to the left might very well be possible) In addition, even a Mavic with arms extended could do the same thing, but I would think the prop arm would snap before it made that big of a puncture. Of course I'm not going to buy an Airbus AS350 and fire MY mavic into it's stabilizer just to be sure, so I'll leave it to investigators to make the call.

Thanks for the info SAR.

Peter T

The NTSB guys have requested the airframe components (i.e. the stabilizer at least) for inspection. They'll doubtless be looking inside for indications.

 

[WithTheBirds]

I am having some trouble believing a drone did that damage and would not have been effected by the wind produced by the helicopter propellers.

Out or pure curiosity- what might you be prepared to believe may have caused the depicted damage?

 

[AMann]

I wouldn’t be surprised if it was a large drone, even an official drone, like a Matrice 200 or something like that. LAPD or some other agency perhaps? Someone has some ‘splainin to do!

 

[sar104]

I wouldn’t be surprised if it was a large drone, even an official drone, like a Matrice 200 or something like that. LAPD or some other agency perhaps? Someone has some ‘splainin to do!

I'm pretty sure that a Matrice would have taken off the entire stabilizer. And no official agency is going to be flying UAVs that illegally.

 

[AMann]

I'm pretty sure that a Matrice would have taken off the entire stabilizer. And no official agency is going to be flying UAVs that illegally.

Uh... glancing blow could have done it- also as they mentioned being jolted when struck. And I’m not going to say who did it, but I’ve seen an official department’s drone footage that was obviously taken during an illegal joy ride made by some department members. Just sayIng someone wasn’t following regulations that night, and it may not necessarily have been a civilian drone. We just don’t know.

EDIT: I just saw your post about how long the horizontal stabilizer is, and it appears that you’re right given the scale of the stabilizer. OK so maybe it was a phantom, it just looked like whatever it was is wide and had a lot of mass-do you suppose that hole was caused by the battery?

 

[sar104]

Uh... glancing blow could have done it- also as they mentioned being jolted when struck. And I’m not going to say who did it, but I’ve seen an official department’s drone footage that was obviously taken during an illegal joy ride made by some department members. Just sayIng someone wasn’t following regulations that night, and it may not necessarily have been a civilian drone. We just don’t know.

EDIT: I just saw your post about how long the horizontal stabilizer is, and it appears that you’re right given the scale of the stabilizer. OK so maybe it was a phantom, it just looked like whatever it was is wide and had a lot of mass-do you suppose that hole was caused by the battery?

Or a motor?

 

[pmshop]

 

[Cymruflyer]

not a drone, not a bird... could it be one of Santas gifts fell of the sled? After all, Christmas time is coming. If we don't want to upset old man, let's blame it on the elfs.

Maybe it was a drone Christmas gift that fell off Santa's sleigh, that would at least remove the responsibility away from a drone flyer. Though I hate to throw blame at the sleigh driver. We could still blame the elves for poor package securing.