Drone vs. aircraft wing testing

[LivinLarge]

Pilot error. No warranty for you...

 

[Goof]

In the context of the crash, and assuming you ignore both the deceleration due to air resistance, and gravity pulling the impact vector down by an effectively infinitesimal amount, the drone and the wing are not under any external acceleration.

If you drop a knife on a balloon, the knife is still accelerating due to gravity at the point of impact. 9.8ms^2 in proportion to the mass of the knife, compared to the same value in proportion to the mass of the balloon (in 1/2mv^2) result in two completely different collision scenarios.

EDIT: Yay for people editing their posts straight after posting....

A drone going 200 mph has more "weight" to stop than a stationary drone. A wing hitting a hovering drone, doesnt have to slow the drone down so the drone will be a less heavy target when the plane is the one moving, Right?

If you're in a plane doing 200kts, and the drone is hovering, the closing speed is 200kts. When you hit the drone, the plane wants to accelerate the drone 200kts relative to the plane's forward vector.

This is exactly the same collision as if the plane was stationary and the drone is moving at 200kts. Only this time, the drone wants to accelerate to -200kts to stop.

 

[Chip]

Why would they lie about the speed...

The article says that the research group "routinely performs sponsored bird-strike testing of aircraft." I believe "sponsored" means someone pays them to do it.

Lying is a strong word. There are a thousand shades of gray. But the credibility of "sponsored research" sometimes depends on who paid for and now benefits from it.

 

[ac0j]

In the context of the crash, and assuming you ignore both the deceleration due to air resistance, and gravity pulling the impact vector down by an effectively infinitesimal amount, the drone and the wing are not under any external acceleration.

If you drop a knife on a balloon, the knife is still accelerating due to gravity at the point of impact. 9.8ms^2 in proportion to the mass of the knife, compared to the same value in proportion to the mass of the balloon (in 1/2mv^2) result in two completely different collision scenarios.

I appreciate you staying civil, I am intrigued by this. Since planes hit birds all the time, and I am unaware if birds doing the amount damage shown in this video I have seen dents and maybe tears.
Even in the text that accompanies the video, they did the same test with a bird and it did MORE damage than the drone, but didnt effect the spar.
Relative speeds of the objects is a factor.
so you are saying the Phantom in the video has the SAME Kinetic energy no matter if it is going 200mph into a wall, or the wall is coming at it at 200mph? That is interesting to me! THANKS!

 

[WithTheBirds]

The article says that the research group "routinely performs sponsored bird-strike testing of aircraft." I believe "sponsored" means someone pays them to do it.

Lying is a strong word. There are a thousand shades of gray. But the credibility of "sponsored research" sometimes depends on who paid for and now benefits from it.

Understood... will be interesting to see if the DJI propaganda dept might get them to comply with the demands or if they might sponser their own research....?

 

[Goof]

so you are saying the Phantom in the video has the SAME Kinetic energy no matter if it is going 200mph into a wall, or the wall is coming at it at 200mph? That is interesting to me! THANKS!

Yep Kinda the crux of what I was trying poorly to explain, "inertial frames of reference".

 

[Chip]

Understood... will be interesting to see if the DJI propaganda dept might get them to comply with the demands or if they might sponser their own research....?

Breaking News: DJI Demands Withdrawal of Drone Crash Video

Yes, I was amazed to read DJI's demand letter! I cannot imagine the researchers or university ever agreeing to remove video from the internet without massive fight.

Suzuki sued Consumer Reports magazine years ago for misrepresenting the risk of Samurai rolling over. Suzuki claimed that CR manipulated results by manipulating road conditions. CR said we are trying the best we can to educate the consumer on a matter of public safety and so what if our methodology is not perfect. An epic 8 year legal battle ensued.

 

[ac0j]

Breaking News: DJI Demands Withdrawal of Drone Crash Video

Yes, I was amazed to read DJI's demand letter! I cannot imagine the researchers or university ever agreeing to remove video from the internet without massive fight.

Suzuki sued Consumer Reports magazine years ago for misrepresenting the risk of Samurai rolling over. Suzuki claimed that CR manipulated results by manipulating road conditions. CR said we are trying the best we can to educate the consumer on a matter of public safety and so what if our methodology is not perfect. An epic 8 year legal battle ensued.

Ha Ha! I actually bought 2 brand new 1988 Suzuki Samurais.I was amazed at how fun they were, and how horrible they were to try to keep going over 65mph in any wind! I remember those tests consumer reports did, they were horrible! They put 1000lbs of outriggers out the sides up from the frame to about 10' high. To "protect" the test driver in case of rollover. You could walk up to the thing, grab the outrigger and tip the truck over I bet..... They were very stable, and got a bad rap. Similar to what Nader did to the corvair in the late 60's

 

[R.J.]

This just in from across the pond...
Drones will be crashed into passenger jets in mid-air to test safety | Daily Mail Online

 

[sar104]

If you believe that the speed was accurate. I believe that appeared to be in the 1000fps or more range. I find it hard to believe it was the around 300fps they claimed. It was video was slowed down so slow much that a Phantom motor was suspended in the frame throughout the rest of the video almost. and gravity didnt start pulling it down. Yet the Phantom covered the field of view in the same slow motion in a few frames.

There is no ambiguity over the speed. It was approximately 240 mph. You need to apply the standard equations of motion rather than speculating about how it looked.

SECOND, I'll need a Physicist to confirm, but I dont think you get the correct result hitting the stationary wing with a drone at an impossible velocity. It seems to me hitting a flying baseball with a bat, and hitting a flying bat with a baseball at the exact same speed would yield completely different results. or like throwing a bird at a suspended BB

Fair enough. I'm a physicist by training and profession and I can assure you that those frames of reference are entirely equivalent because, in Newtonian physics, velocity is a relative quantity, i.e. all that matters is relative velocity.

 

[sar104]

External acceleration is what I thought they did with the drone.
A drone going 200 mph has more "weight" to stop than a stationary drone. A wing hitting a hovering drone, doesnt have to slow the drone down so the drone will be a less heavy target when the plane is the one moving, Right?

I hate to have to say this, but you are massacring basic physics. It doesn't matter which is moving and which is stationary, because those definitions only apply in the frame of reference of the observer. Imagine, as a simple thought experiment, that you were watching this collision while moving at the same speed as the drone. If all you could see was the drone and the wing then, from your perspective, the drone would be stationary and the wing would be moving. But it wouldn't change the dynamics of the impact.

 

[sar104]

This is where I cant grip it. There is a certain amount of energy gained with speed, that energy has to be expended. I feel a stationary drone hit by a plane at 200mph would not have the same energy as the drone fired from a cannon. In an actual in air collision, the hovering drone would have a certain amount of "give" that is does not have at speed. The stationary wing wont "move"as a result of being hit by a 1.5lb drone, BUT a hovering 1.5lb drone WILL react to being hit by a 1000lb plane. because there is little resistance to overcome.
at 200mph (so the video says) there is some kinetic energy adding destructive power to the moving drone that is not present hovering in free air.

I am thinking If I drop a balloon on a knife, and if I drop a knife on a balloon.

Dropping is different for two reasons. Firstly, the knife will fall faster because it experiences much less aerodynamic drag relative to its weight, and, secondly, because the force of gravity continues to act during the collision, and the knife likely weighs more than the balloon.

 

[ac0j]

I hate to have to say this, but you are massacring basic physics. It doesn't matter which is moving and which is stationary, because those definitions only apply in the frame of reference of the observer. Imagine, as a simple though experiment, that you were watching this collision while moving at the same speed as the drone. If all you could see was the drone and the wing then, from your perspective, the drone would be stationary and the wing would be moving. But it wouldn't change the dynamics of the impact.

I am functioning with half my brain tied behind my back tonight, tired and medicated. BUT After the help here, and a little time to think on it, I understand now. I shoot pistols and rifles a lot, and watch a ton of high speed video, Why too many to even estimate a number. The wing video just really reminded me of what happens in ballistic testing videos. The bullet crosses the field of view over a number of frames, (about the same as the Phantom does)and any debris ejections seem weightless in the videos they are just hovering for many seconds. I realize, the film speed may be different in this film, but the Debris (motor shaft in this case) doesnt seem to know there is gravity for about as many frames as the ballistic videos. That suggests the same frame rate, thus my conclusion is the film is of a drone at bullet speeds 1000fps or more. But someone involved stated they tested at 240ish MPH or 350ish fps so we have no choice but to believe it now that is is print. If it looks like a duck, and acts like a duck..........

 

[ac0j]

Anyway, what is the verdict. Is the result a crashed airplane? NO. Not by a longshot. That plane would keep flying. and for the record, from the text in the original article;

"After calibration work to ensure they could control the speed, orientation and trajectory of a drone, researchers fired a successful shot at the Mooney wing. The researchers then fired a similarly weighted gel “bird” into a different part of the wing to compare results. “The bird did more apparent damage to the leading edge of the wing, but the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”

Conclusion, drone strikes are (roughly) equal to a bird strike, and, what would you guess, 1000 times less likely?

 

[WithTheBirds]

Anyway, what is the verdict. Is the result a crashed airplane? NO. Not by a longshot. That plane would keep flying. and for the record, from the text in the original article;

"After calibration work to ensure they could control the speed, orientation and trajectory of a drone, researchers fired a successful shot at the Mooney wing. The researchers then fired a similarly weighted gel “bird” into a different part of the wing to compare results. “The bird did more apparent damage to the leading edge of the wing, but the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”
Conclusion, drone strikes are (roughly) equal to a bird strike, and, what would you guess, 1000 times less likely?

I haven’t seen any numbers on probability. I would think a bird is significantly better at avoiding flying in front of an aircraft than many donkey’s who fly UAV’s might be. Easy to buy, less than a couple days pay for most people, no training or certification required and virtually no skill required to fly. DJI knows all this and that’s why they will do anything to avoid sale and use being banned or tightly controlled.

 

[sar104]

I am functioning with half my brain tied behind my back tonight, tired and medicated. BUT After the help here, and a little time to think on it, I understand now. I shoot pistols and rifles a lot, and watch a ton of high speed video, Why too many to even estimate a number. The wing video just really reminded me of what happens in ballistic testing videos. The bullet crosses the field of view over a number of frames, (about the same as the Phantom does)and any debris ejections seem weightless in the videos they are just hovering for many seconds. I realize, the film speed may be different in this film, but the Debris (motor shaft in this case) doesnt seem to know there is gravity for about as many frames as the ballistic videos. That suggests the same frame rate, thus my conclusion is the film is of a drone at bullet speeds 1000fps or more. But someone involved stated they tested at 240ish MPH or 350ish fps so we have no choice but to believe it now that is is print. If it looks like a duck, and acts like a duck..........

There is nothing strange about this result. Anyone who has done impact testing on composite structures would have predicted the outcome reasonably accurately. Based on the video properties I can pretty much guarantee that it was taken with a Vision Research high-speed video system, such as the Phantom 1212, running at 10,000 frames per second.

 

[ac0j]

I haven’t seen any numbers on probability. I would think a bird is significantly better at avoiding flying in front of an aircraft than many donkey’s who fly UAV’s might be. Easy to buy, less than a couple days pay for most people, no training or certification required and virtually no skill required to fly. DJI knows all this and that’s why they will do anything to avoid sale and use being banned or tightly controlled.

I looked it up once, there is a very large number of bird strikes by aircraft each year, probably 100 Times more than I would have guessed. I cant recall the number, but I remember being shocked.
NOW, as you stated, I think a bird WOULD have a better chance to avoid it, but they dont always.
Now we have to compare the number of birds in relation to drones in the sky at any given time, and figure out if it is even an issue, or just a politicians pet project.

 

[ac0j]

There is nothing strange about this result. Anyone who has done impact testing on composite structures would have predicted the outcome reasonably accurately. Based on the video properties I can pretty much guarantee that it was taken with a Vision Research high-speed video system, such as the Phantom 1212, running at 10,000 frames per second.

If we were absolutely SURE of that, there is a chance I know someone that could figure the exact speed of the phantom just by knowing its measurements......

 

[sar104]

Anyway, what is the verdict. Is the result a crashed airplane? NO. Not by a longshot. That plane would keep flying. and for the record, from the text in the original article;

"After calibration work to ensure they could control the speed, orientation and trajectory of a drone, researchers fired a successful shot at the Mooney wing. The researchers then fired a similarly weighted gel “bird” into a different part of the wing to compare results. “The bird did more apparent damage to the leading edge of the wing, but the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”

Conclusion, drone strikes are (roughly) equal to a bird strike, and, what would you guess, 1000 times less likely?

The Phantom did significantly more structural damage. Whether or not it would have resulted in a crash is secondary to the simple observation of the damage. Would you be comfortable with your situation on that aircraft after such a collision?

I don't understand the attitudes on display here. Ever since the threat of drone strikes on engines, wings, control surfaces etc. became a discussion topic there was incessant whining that it was pointless to worry about it without some actual testing. So now we have some carefully conducted testing and the response, from the same people, most of whom are clearly completely unqualified to comment on the technical merit of the work, is basically to shout "fake news"?

If an aircraft in this scenario crashed then the outcome is clearly catastrophic. Even if the aircraft lands safely, the damage is still extremely expensive to fix. Neither outcome is sufficiently acceptable that we should not worry about it. That the probability of collision is low doesn't change the validity of the tests, which are attempting to answer the question - "if a collision occurs, what is the damage?".

 

[sar104]

If we were absolutely SURE of that, there is a chance I know someone that could figure the exact speed of the phantom just by knowing its measurements......

I used reverse logic. Given the dimensions of the Phantom and the measured speed of 238 mph (106 m/s), that leads to a calculated frame rate of almost exactly 10,000 frames per second. As a regular user of those cameras, I can tell you that 10e4 fps is a common frame rate (the frame rate is set in the software via a dropdown menu), so that is entirely plausible.