Drone vs. aircraft wing testing

[lmel2005]

Please learn the meaning of words before you use them, or misuse them, in this case. Contrary to your assertion above, collisions have occurred. Statistically they may be infrequent, or uncommon, but the statement "statistically they don't" is not only incorrect in this case but also not a correct use of "statistically".

That's what I mean. Collisions are so rare, that their number statistically is not significant.

Sorry if that was not clear.

 

[sar104]

That's what I mean. Collisions are so rare, that their number statistically is not significant.

Sorry if that was not clear.

No one is arguing that they are common events. This test was to evaluate impact damage if a collision were to occur with a light aircraft wing. And, since at least two collisions with aircraft have occurred in the US, we know that it can happen.

As for whether the number is statistically significant, that depends on how many aircraft collisions you regard as significant. If we were to end up with, say, a couple of badly damaged or downed aircraft per year, would you regard that as insignificant? Would it be insignificant to the FAA, who would classify them as aircraft mid-air collisions, not bird strikes. Would it be insignificant to the aviation industry, or the general public? Those are rhetorical questions, of course.

 

[lmel2005]

No one is arguing that they are common events. This test was to evaluate impact damage if a collision were to occur with a light aircraft wing. And, since at least two collisions with aircraft have occurred in the US, we know that it can happen.

As for whether the number is statistically significant, that depends on how many aircraft collisions you regard as significant. If we were to end up with, say, a couple of badly damaged or downed aircraft per year, would you regard that as insignificant? Would it be insignificant to the FAA, who would classify them as aircraft mid-air collisions, not bird strikes. Would it be insignificant to the aviation industry, or the general public? Those are rhetorical questions, of course.

For FAA, or for public, every incident may be significant, but if we measure the number of incidents, per total number of drones (for example), result is statistically not significant.

 

[sar104]

For FAA, or for public, every incident may be significant, but if we measure the number of incidents, per total number of drones (for example), result is statistically not significant.

OK - you don't understand the technical meaning of statistical significance. Statistical significance refers, specifically, to a set of results that indicate that two phenomena are not causally unrelated. Statistically insignificant would mean that they are likely unrelated. It simply doesn't apply to this situation, which is not trying to correlate possibly-unrelated phenomena. Low frequency and statistically insignificant are completely different concepts.

 

[lmel2005]

OK - you don't understand the technical meaning of statistical significance. Statistical significance refers, specifically, to a set of results that indicate that two phenomena are not causally unrelated. Statistically insignificant would mean that they are likely unrelated. It simply doesn't apply to this situation, which is not trying to correlate possibly-unrelated phenomena. Low frequency and statistically insignificant are completely different concepts.

In post #82 I thought we were talking about the same subject, and "significant" meant the same thing for us.

But you're right about technical terms.
2 collisions for all drones of the world, makes a low frequency, a low risk and a low probability.

 

[ac0j]

Oddly, Both reported collisions caused minor damage (I did not say inexpensive) Not even anywhere near the minimal damage portrayed in the OP video, that would not have forced a landing even. (from the actual text of the article that was printed with the video)
I also can say for a FACT that more cars have been destroyed by meteorites than planes have been that are hit with RC toys. (Technically, the aircraft hit the drone in both cases).

Clips from the article that it seems the experts have not read, but make comments any way;

1. "Poormon, whose group routinely performs sponsored bird-strike testing of aircraft structures—such as wings, windscreens and engines—presented test results and video of the drone shot at the fourth annual Unmanned Systems Academic Summit, held in August at Sinclair College’s Conference Center and its National UAS Training and Certification Center in Dayton. "

The motivation for good evidence of possible destruction by a UAV

2. "Drones are similar in weight to some birds, and so we’ve watched with growing concern as reports of near collisions have increased, and even more so after the collision last year between an Army Blackhawk helicopter and a hobby drone that the operator flew beyond his line of site.

Although the helicopter returned home with only minor damage to a rotor, Poormon said it is only a matter of time before a drone strike causes more significant damage to a manned aircraft."

First, It sounds a little like the "me too movement" also note, the same UAV from the test in a real collision, not catastrophic.

3. “We wanted to help the aviation community and the drone industry understand the dangers that even recreational drones can pose to manned aircraft before a significant event occurs. But there is little to no data about the type of damage UAVs can do.

OMG! you think have they applied for the grant money yet? Of course the damage has to be impressive or NO MONEY FOR YOUR RESEARCH!

4. "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. , but 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 the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”

Conclusion?, not enough data. For now, for anyone but the sky is falling crowd. the ONLY THING THEY PROVED is its equal to or less than a bird strike.
Noted "spar damage" so what, a dent? a scratch? Kind of important information to leave out?

Do 5 drones, and 5 gel birds and get back to us. This time dont use an extra light plane designed for speed, and use a "commercial" aircraft. After all, thats what you want us to call our Hobby flying cameras.

 

[laurens23]

1. "Poormon, whose group routinely performs sponsored bird-strike testing of aircraft structures—such as wings, windscreens and engines—presented test results and video of the drone shot at the fourth annual Unmanned Systems Academic Summit, held in August at Sinclair College’s Conference Center and its National UAS Training and Certification Center in Dayton. "

The motivation for good evidence of possible destruction by a UAV

Tests equipment cost money, experts in this field cost money too. Impact testing is part of certification.

So what happens is that the university/institute has the equipment and expertise to do the tests. Most plane manufacturers need maybe a couple tests per year. Not worth it to buy the equipment and hire experts themselves. So they pay the university/research institute to do the tests for them.

2. "Drones are similar in weight to some birds, and so we’ve watched with growing concern as reports of near collisions have increased, and even more so after the collision last year between an Army Blackhawk helicopter and a hobby drone that the operator flew beyond his line of site.

Although the helicopter returned home with only minor damage to a rotor, Poormon said it is only a matter of time before a drone strike causes more significant damage to a manned aircraft."

First, It sounds a little like the "me too movement" also note, the same UAV from the test in a real collision, not catastrophic.

Nobody said a collision would be catastrophic. This is just to show that collisions can and do happen. Giving relevance to performing the test.

3. “We wanted to help the aviation community and the drone industry understand the dangers that even recreational drones can pose to manned aircraft before a significant event occurs. But there is little to no data about the type of damage UAVs can do.

OMG! you think have they applied for the grant money yet? Of course the damage has to be impressive or NO MONEY FOR YOUR RESEARCH!

Not everything is a conspiracy theory. This is an organisation that is not likely to risk their reputation for this. They are just (professionally) interested in furthering their knowledge and improve safety.

If it was DJI or the AMA who did the tests I would be sceptical.

4. "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. , but 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 the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”

Conclusion?, not enough data. For now, for anyone but the sky is falling crowd. the ONLY THING THEY PROVED is its equal to or less than a bird strike.

Noted "spar damage" so what, a dent? a scratch? Kind of important information to leave out?

There is a lot we can tell even from just this video. The damage profile and associated risks are totally different.

The bird will disintegrate on impact with the skin. This will cause a large damage area on the outside, because most energy is absorbed by the outside. The result is a smashed up leading edge. And maybe bend some ribs. This damage has to be counteracted by the control surfaces of the plane.

The drone penetrated the wing. This means a small hole in the outside skin and lots of energy that needs to be dissipated inside. This can cause damage to electrical wiring, control cables, core structure, fuel tanks. Something that the plane was not designed for.

Then there is the fact that the drone has a battery that could very well catch fire on impact. If the wing caught on fire the damage might very well be catastrophic. If they wanted a sensational test result they would have made sure that it would catch on fire.

Any damage to the spar likely means the plane is scrap or at least a very long and costly repair. A leading edge and some ribs from a bird strike can be repaired relatively quickly and cheap.

Do 5 drones, and 5 gel birds and get back to us. This time dont use an extra light plane designed for speed, and use a "commercial" aircraft. After all, thats what you want us to call our Hobby flying cameras.

Yes, that is why they want/need research money. Which they probably hope to get based on this initial basic and cheap test.

The plane they used represents probably 70+% of General Aviation (basic metal wing), General aviation has the biggest risk not only are there a lot more GA flights taking place, they are also within reach of drones for most of the flight. Airliners are only inside the same envelope as a drone during takeoff and landing.

The drone is from DJI who have ~50% market share and the phantom they used is pretty representative in weight to most drones out there.

I agree the velocity of the impact is on the higher end of the scale.

Some rough numbers for the USA on flights taking place per day: 30.000 airliners and 60.000 General aviation flights 5000 military flights.

320.000 registered manned aircraft, slowly declining, (near) 100% registration rate.

1.000.000 registered drones, exponentially increasing, roughly 30% registration rate.

 

[ac0j]

With every method of travel there is risk. This still isnt even close to the risk people driving cars face every minute of every day. Or motorcycles, bicycles, skateboards, or even on horseback.

If drone pilots agree to stay below 500' above average terrain, and stay well away from airports and helipads. AND if manned aircraft stay above 500' above average terrain (unless over a population Then remain above 1000') like they are SUPPOSED to. Make this LAW, and that is all that is needed.

The drone pilots that break the laws need to be issued tickets, the manned aircraft pilots that fly lower than they are supposed to should have to accept some risk and responsibility as well.

Get rid of the 336 and 107 all together. Because come on, Taking pictures and selling them???? REALLY? Let the IRS worry about who is making money. And keep the FAA stick with alocating NATIONAL airspace for EVERYONES use.
And how in the world does 336 or 107 relate to piloting skills, or making choices about flights?

If there is an accident, find who is responsible and address it the way all other personal or property damage accidents are dealt with.
If you are a pilot afraid of drones, dont fly. If your a drone pilot afraid of getting hit by a plane, dont fly.

 

[newt2u]

Why do people post total nonsense like this on subjects that they know nothing about?

A 1st degree in Maths and aeronautics perhaps shows some knowledge of the subject. What are your qualifications?

 

[sar104]

A 1st degree in Maths and aeronautics perhaps shows some knowledge of the subject. What are your qualifications?

Ph.D physics, not that it's relevant, because if you ever took an aeronautics or mathematics course then you need to ask for a refund - you don't show any knowledge of the subject. You stated that the air flow would suck a projectile over the wing. That is incorrect on so many levels it's hard to know where to start.

Firstly, the air, a compressible fluid, has an initial density of around 1 kg/m³. The drone is a rigid body (before collision)and has a density at least 3 orders of magnitude higher - let's conservatively say around 1000 kg/m³. It's not going to be measurably deflected by the bow wave in front of the wing. As pointed out above - that's why birds and other objects, like rain drops, hail stones and insects hit wing leading edges - they do not simply follow the streamlines and they are less dense than drones. And that's still ignoring that the drone (or bird) is likely to span streamlines that diverge around the wing. Decisions, decisions...

Which leads to the second problem - why over the wing? So you are suggesting that the incoming air, or most of it, deflects over the wing? Just think briefly about the resulting pressures above and below the wing if that were to happen, and what that would mean in terms of lift. That's not how lift is generated. You shouldn't need your aeronautics texts for that question.

 

[Chip]

Sar have you ever considered trying to make a point without a personal insult or with claim of intellectual superiority?

 

[newt2u]

Well Sar, you have to look at the context of the response. I responded to someone saying that it was the same if the wing was stationary or moving. Clearly that is not the case. As for the the over comment. If you aim the drone at a moving wing leading edge ( as was clearly the case in the video), the lower pressure above (Lift) will tend to suck anything up. Notice I say tend to, I did not say it would get sucked over.

 

[sar104]

Well Sar, you have to look at the context of the response. I responded to someone saying that it was the same if the wing was stationary or moving. Clearly that is not the case. As for the the over comment. If you aim the drone at a moving wing leading edge ( as was clearly the case in the video), the lower pressure above (Lift) will tend to suck anything up. Notice I say tend to, I did not say it would get sucked over.

The lower pressure is above the wing - incoming objects don't see it, even if they were sufficiently low density to be affected. Nothing "tends to get sucked over the wing" either unless it is above the wing to begin with.

 

[sar104]

Sar have you ever considered trying to make a point without a personal insult or with claim of intellectual superiority?

It wasn't me who pulled the "look at my qualifications" card, and if people choose to post nonsense and then claim obviously bogus qualifications to back it up, then my patience is fully exhausted.

 

[newt2u]

The lower pressure is above the wing - incoming objects don't see it, even if they were sufficiently low density to be affected. Nothing "tends to get sucked over the wing" either unless it is above the wing to begin with.

Just because you say it is so does not make it so. Density is not the issue here, that just affects the degree of action. That there is action can be seen from the laminar flow lines around an aerofoil, which when generating lift, i.e. has an angle of incidence or camber, these lines flow from beneath the wing over it.

Take a look here... exaggerated angle of attack but you can see flow from beneath up and over at the leading edge.

I have tried to keep this discussion technical. Its a shame you can not.

 

[sar104]

Just because you say it is so does not make it so. Density is not the issue here, that just affects the degree of action. That there is action can be seen from the laminar flow lines around an aerofoil, which when generating lift, i.e. has an angle of incidence or camber, these lines flow from beneath the wing over it.

Take a look here... exaggerated angle of attack but you can see flow from beneath up and over at the leading edge.

I have tried to keep this discussion technical. Its a shame you can not.

You haven't introduced an iota of technical discussion prior to that post - you have simply ignored all the points made by both me and others that show why you are wrong.

So let's talk about the airflow visualization you posted. Exaggerated is fine, because it doesn't change anything fundamental about the problem; even in the high angle of attack situation you can clearly see streamlines going over the wing and under the wing, and there is also a stagnation zone between the two which forms the origin of the detached compressive wave in subsonic flight.

And no - just because I say it does not make it so, any more than you denying makes it incorrect. What makes it so is that it should be trivially obvious to anyone who has just a slight grasp of compressible flow that even relatively entrained material does not follow the streamlines. How you can say that density doesn't matter because it only affects the amount of deflection is beyond me; that's exactly why it matters. Gas, or even smoke particles, would follow the streamlines. Larger particles three orders of magnitude denser will not follow the streamlines because the forces on them are far too small, and that's not even taking into account the question of a dense rigid object that spans streamlines going over and under - which way will it go?

And you are still completely ignoring the obvious, that has been pointed out multiple times now, that birds and other objects regularly do hit leading edges and control surfaces. Or consider your car windshield - all the streamlines go up and over that, and yet birds, insects and other small, less dense objects impact it at speed.

 

[newt2u]

Thanks, Sar, you have now completed my argument. You agree that fixed wing/moving wing scenarios are not the same, which was the point I was making.

I note that you are very good at the straw man mode of argument, i.e. say something I never said or implied and then refute it, e.g. I never said more dense objects would follow streamlines, I was just refuting what you had claimed earlier.

 

[newt2u]

p.s. I'm bored, as I imagine are others on this thread. Please do not respond further on this.

 

[ac0j]

If pilots can see with detail, at speeds, drones and birds approaching them from supposedly up to a mile away, why cant they use a little control input to evade it? A leading edge would only have to move a couple of inches above or below a hovering object to avoid puncture?
OR is it that they CANT see what they claim they see, and these events are more like the bugs on the windshield example. You cant have it both ways.

 

[sar104]

Thanks, Sar, you have now completed my argument. You agree that fixed wing/moving wing scenarios are not the same, which was the point I was making.

I note that you are very good at the straw man mode of argument, i.e. say something I never said or implied and then refute it, e.g. I never said more dense objects would follow streamlines, I was just refuting what you had claimed earlier.

Nice - yet another post devoid of any technical understanding. I didn't complete your poor attempt at argument at all, I debunked it, and I did not make any straw man arguments - your entire, short, point was that the test was flawed because, in the real scenario, the drone would tend to be sucked over the wing. It's far too late to say you didn't mean that. My original assessment of you was correct, and I'm glad to hear that you won't be back.