Drone hobbyists find flaws in “close call” reports to FAA from other aircraft
usatoday.com
usatoday.com
Links to both the FAA's press release and the AMA's response in this AMA blog post.
http://amablog.modelaircraft.org/amagov/2015/09/14/ama-respo...
The UAV in question was spotted at ~10,000ft above sea level, but it was only about 800-900ft above the local ground level at the time.
Multi-rotors using BLDC motors cannot really be compared to small general aviation aircraft with infernal combustion engines.
"Reasonable duration" is a nebulous phrase. Some of the airframe configurations we use here couldn't manage more than about 10 minutes at 100ft, whereas others could quite happily carry a gopro at 10,000ft for 10 minutes (assuming it didn't have to climb from sea level!)
>Multi-rotors using BLDC motors cannot really be
It's got nothing to do with the type of motor or fuel.
>"Reasonably duration" is a nebulous phrase. So
So is "quite happily carry". I'll admit that it appears that it's not impossible for such a flight, but I don't agree that any drone is "happily carrying" anything at that altitude.
I don't have time to run the model for this specific case, but from a similar case with a lower air density of 0.71kg/m^2 (40c at 4km altitude) a simple quad uses ~20% more power in a stationary hover than at sea level.
Interestingly at high flight speeds (15-20m/s) you could actually start to see power savings at this altitude, as the parasitic drag of the vehicle body is reduced.
https://i.imgur.com/Z5toIVm.jpg
Assuming air pressure at 10000 ft is ~69kpa, and sea level is ~100kpa, there really doesnt appear to be much of a difference, except for medium-sized props, which had very interesting thrust outputs- gaining efficiency at low rpm and loosing a lot at high rpm.
Anyway, point being is a 250 class quad could pretty easily fly at 10000 feet. Not particularly well, but considering 1:4 (or even 1:8) thrust ratios arent uncommon with 250 class quads they could still pull it off.
Now, idk about bigger quads like the phantom/iris, their props have quite different geometries which probably act quite differently.
Do you mind if I ask where you are getting that pressure value from?
The ICAO Standard Atmosphere gives a value of 70kPa for 10,000ft.
Not really... you need to move the same MASS of air, just more air VOLUME. Bigger props solve that problem, at the expense of moving a large prop (greater moment of inertia, slower acceleration).
Most small drones these days are electric, so that doesn't happen. It's a bit harder to generate lift from the props in thinner air like that, but you also experience less drag, which balances that out to a large extent.
I'd really love to see the math on the probability of a tiny quad intersecting the flight path of a firefighting aircraft at 3km altitude though. They are small and that's a LOT of open space. I can barely spot one against the open sky at a few hundred feet up. If these guys spotted one they must have amazing superhuman vision or amazing luck to have come within a very close distance.
Personally I put most of the sightings into the mass-hysteria camp. I know there are idiots out there flying in controlled space, but I also think things are being blown way out of proportion.
Edit: I found a site that did the speed/climd rate calculations. My numbers are bit off. The DJI, a common platform, could hit 3km in about 5.5 minutes and a 250 racing quad could do it in about 5. With about 20 minutes of battery power that leaves maybe 5-10 minutes of loiter time.
DJI Phantom 2 Vision+: flight speed of 17 m/s (61 km/h) and a maximum climbing rate of 9 m/s
250 FPV Racing Quad: maximum flight speed of 18.5 m/s (67 km/h) and a maximum climbing rate of 10 m/s
I think it's a certainty that one would/should have a video system for operating without line-of-sight. Video systems are common in high-end equipment.
>Personally I put most of the sightings into the mass-hysteria camp. I know there are idiots out there flying in controlled space, but I also think things are being blown way out of proportion.
Yeah. Agreed.
>>I found a site that did the speed/climd rate calculations. My numbers are bit off. The DJI, a common platform, could hit 3km in about 5.5 minutes and a 250 racing quad could do it in about 5. With about 20 minutes of battery power that leaves maybe 5-10 minutes of loiter time.
10,000 ft seems right at the edge of what the things can even do. They aren't going to be stable or easy to fly/land like a fixed wing aircraft would.
edit: forgot part of my post.
>I'd really love to see the math on the probability of a tiny quad intersecting the flight path of a firefighting aircraft at 3km altitude though. They are small and that's a LOT of open space.
"Big Sky" theory doesn't give me as much comfort as it ought to.
>I can barely spot one against the open sky at a few hundred feet up. If these guys spotted one they must have amazing superhuman vision or amazing luck to have come within a very close distance.
This. I have a difficult time spotting full-sized aircraft in the air, and I have pretty good vision.
Its "only" a 25% reduction in density, you can still get a fair amount of flying done at that altitude. My colleagues have been to Ecuador twice for field work and had no issues flying quads in Quito (9,300ft), no need to change control gains or anything like that. So I know its perfectly possible.
Basically you can go 3k up then stay a minute and free fall down.
Bigger quads can fly longer - albeit going up always takes most energy and many big quads also need energy to go down / can't free fall without crash
Thing is, I seriously doubt many people fly their quadcopters that high. It's not much fun (not more fun than, say, 500ft), you don't have line of sight, and the wind will blow it away so if you don't track where you're going you're likely to lose your craft.
Plus at that range, we're talking some serious long-range equipment. Ready-to-fly consumer drones max out at approx. 1 mile range. If you buy this stuff, you probably understand (you should!) what you're doing.
It's possible alright, but not very likely.
Exactly what does the FAA think hobby kits include now? A complete knock down kit for a RQ-4 Global Hawk?
edit: corrected post, see reply below.
You can get ballons to fly that high but not much anything else at an affordable price.
Part of me applauds the stricter rules. It's just so easy for some knucklehead to buy a quadcopter from China and fly it around the White House or an airport or over someone's backyard. Unfortunately, these people destroy the hobby, giving it a bad name.
On the other hand, the rules we have had for decades (don't fly near airports or restricted zones, don't fly too high, don't fly over crowds, etc.) are perfectly fine and reasonable. We don't need stricter rules and regulations, we need common sense from drone pilots.
Secretly I hope that drones are really a fad, and the interest will fade away. That leaves the hobby for the real enthousiasts.
Use your expertise to start a club with exorbitant fees or teach exclusive weekend beginner classes (Bring Your Own Drone).
AKA: Start selling pick axes to the new gold miners.
"Common sense" is mostly social norms (usually starts out as "hard-earned wisdom" until the culture forgets how it was acquired), when there's a huge continuous influx of new participants the "old culture" can't keep up, neither can its "common sense". Doubly so when a hobby lends itself to nefarious uses and mindless fuckups as much as drones do.
sound of explosions
"Aw, will you look at that, Dave. They nearly missed."
"Yes. But not quite!"
-- George Carlin
The point where you go from colliding to a near miss is the point where the two things don't touch. There's no exact point where you go from a near miss to a regular sort of miss, since it's not a precision term.
This isn't just to be pedantic; there's lots of redundant or incorrect language out there which Carlin talks about at length.
While Carlin -- as comedians often do -- used the manner in which natural language idioms are irregular as the basis for some of his humor, the irregularity of natural language idioms is not incorrectness. It may be aesthetically displeasing to people who have a strong preference for regularity -- a preference which is probably overrepresented in the HN audience -- but that's a different issue.
Therefore "near miss" could be read as "close to, but not quite a miss" and it would be more accurate to say a "near hit" meaning "close to, but not quite a hit". In this context, a "near miss" is a collision - that almost didn't happen and a "near hit" would be a collision that almost happened but didn't.
Edit:
If trying to collide, it would be appropriate to call a collision that almost didn't happen a "near miss".