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Drone strike

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Old 18th Apr 2016, 16:30
  #101 (permalink)  
 
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Originally Posted by abgd
The hardest parts of a drone are the motor shafts which will be a few inches long and perhaps 5-10mm diameter - they will be made of hardened steel.
For "a few inches" read "under two inches in all but the very largest examples".

For "5-10mm dia" read 3-5mm dia in all but the very largest examples.

For "hardened steel" read "mild steel in all but the very few and rather expensive examples".

All of this information is easily discoverable with a few seconds of research, yet the myths and postulations prevail <sigh>

PDR

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Old 18th Apr 2016, 16:49
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I sincerely hope the culprit is caught and faces prison timer and a eye watering fine.
A throughly irresponsible act that screws it up for everybody else.

The popular 3 makes of drone are DJi - 3DR - Yuneec

These guys dominate the market and their drones are geo fenced, i.e if you try to enter restricted airspace the drone will not enter it. You are blocked from flying into prohibited areas and there is nothing you can do about it. The drone will refuse to fly.
Also the drones require regular connection to the internet to update the OS and the list. Failure to do so results in drone that will not fly.

The culprits doing this stunt were probably using a really old drone of a custom build. I am fairly confident they will be caught once the police recover the remains of the drone.
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Old 18th Apr 2016, 16:54
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they will be caught once the police recover the remains of the drone.
Are the Police looking...??
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Old 18th Apr 2016, 16:57
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I believe so, After impact that thing was toast so if it was above a restricted area i suspect the drone operator scarpered.
If they can recover certain components they may have an idea of previous flights / perhaps even footage.
At the very least they can approach component suppliers as i have said this was a custom drone and they might be able to trace who purchased what.
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Old 18th Apr 2016, 17:34
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The popular 3 makes of drone are DJi - 3DR - Yuneec

These guys dominate the market and their drones are geo fenced, i.e if you try to enter restricted airspace the drone will not enter it.
Nah, they don't come close to dominating the market. Cheaper drones from companies like Hubsan, SYMA, UDI, etc., probably outsell the above by 20:1 if not more in terms of units sold, and most of them are not geo-fenced (or even have GPS!)

Besides it's trivial to bypass geofencing. Plus more and more kids these days are making their own custom drones for cheap. Virtually none of the popular flight controllers enforce geo-fencing. KK, Pixhawk, Multiwii, etc.
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Old 18th Apr 2016, 18:10
  #106 (permalink)  
 
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I have not heard of anyone yet hacking DJi's code, maybe I am wrong and it can be done but nothing on the forums i have seen.
You run the risk of bricking it. I have seen articles of GPS jamming and false GPS signal injection but no hacks yet.

Yes you can build your own with a pixhawk etc, hence i am sure that the drone involved in this episode was a home brew. Do the other drones have the legs or range of DJI's machines, I am thinking of lightbridge, and its a guess the the drone operator in this case wanted to see/film where he was flying (aircraft landing) via his video downlink.
Yunecc's video link is reported to be only 500m line of sight were as DJi can go for a few km.
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Old 18th Apr 2016, 18:23
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Originally Posted by msjh
And, yes, the 400' limit set by government is 400' above ground level. Again, the DJI software enforces that limit by default
The software constrains the height AGL? How does that work in practice?

If the drone is using GNSS height, that implies it must have access to a terrain model to derive height AGL.

If it's using baro height, the same applies, with the added complication that the drone/controller needs to know the QNH.

Both sound a bit unlikely.
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Old 18th Apr 2016, 18:42
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Originally Posted by DaveReidUK
Both sound a bit unlikely.
Perhaps the GNSS height at takeoff height is captured in software and 400 feet is added to that to make the allowable GNSS height?

If so, you could not achieve 400 feet AGL above nearby higher terrain, but you could achieve 400+ feet AGL over nearby lower terrain.
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Old 18th Apr 2016, 18:43
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Originally Posted by DaveReidUK
The software constrains the height AGL? How does that work in practice?

If the drone is using GNSS height, that implies it must have access to a terrain model to derive height AGL.

If it's using baro height, the same applies, with the added complication that the drone/controller needs to know the QNH.

Both sound a bit unlikely.
It's simpler than that. On power-up they automatically define "here" as the "base" waypoint. The altitude of "here" is defines as zero AGL, and everything is relative to that.

And before people get too fixated with the idea that a small number of commercial ready-to-go drones will control the market - have a look at websites like Hobbyking, where brew-your-own stuff (including control boards) are available for peanuts with websites full of "how to2 pages and videos to show all but the most numpteous how to create your own multicopter with your own tailored FCS software.

PDR
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Old 18th Apr 2016, 19:22
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Drone's debris location

I have been told that the area for the drone's debris is believed to be, at this stage, located in Richmond-Surrey, specifically it is believed that the drone was being flown by somebody operating the device from within Richmond Park.
I guess approximate location reported directly by the pilots (or calculated by distance from runway vs impact time) therefore I think it is only a matter of time before this sort of drone is found by either the Police or locals.
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Old 18th Apr 2016, 19:56
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If the drone was flying from Richmond Park it would have to travel a minimum of a kilometre northish of its launch position in order to hit an aircraft on the 27L approach.
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Old 18th Apr 2016, 19:58
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The CAA
don’t seem to be taking this threat seriously; the only rule for a
drone
operator seems to be that he must keep the machine below 400ft (is

that above ground level or sea level?)


No there are more rules, see ANO166 plus exemption E4049 and ANO 167. Alsosee CAP658 and CAP722. Height is defined as height above point of launch.


Yunecc's
video link is reported to
be only 500m line of sight were as DJi can go for
a few km


To achieve this range would require a video transmitter illegal in the UK(OFCOM IR 2030). To fly beyond visual range would be illegal in the UK(ANO166).
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Old 18th Apr 2016, 20:05
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Any hobbyist can -and often does- build a drone out of a kit with a carbon fiber cross, a few brushless motors and some electronics. In fact, a visit to any photo show will demonstrate that the heavyduty photo drones for pro video cameras are basically custom constructions by smaller firms. These things cannot be legislated out of existence, anymore than the first kit-built cars would be suppressed back in the era of the horse carriage.

Pilots of small planes learnt to share the sky with huge airliners; now huge airliners and GA will need to learn to share the skies in some way with the smalller drones that are going to be used for cargo and surveying tasks in cities and over fields. Farmers who use drones to survey hundreds of square miles of crops in the US midwest, or livestock in South America, have a right to use tools to get their jobs done, just as much as a pilot setting down at Heathrow has a right to land without a laser in his eyes or an idiot with a toy in his path.

The sky hasn't fallen - a new technology has appeared, and sclerotic bureaucrats need a kick in the butt so they start to establish a new set of rules.

Edmund
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Old 18th Apr 2016, 22:06
  #114 (permalink)  
 
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For "a few inches" read "under two inches in all but the very largest examples".

For "5-10mm dia" read 3-5mm dia in all but the very largest examples.

For "hardened steel" read "mild steel in all but the very few and rather expensive examples".

All of this information is easily discoverable with a few seconds of research, yet the myths and postulations prevail <sigh>

PDR
OK, the steel shaft in the DJI phantom 2213 motor is just over 36mm long and 7.9mm diameter which is less than 2 inches but more than 5mm thick.

DJI ESC and Brushless Motor

I can't speak for the DJI motor shafts, but all the aftermarket motors such as scorpions, Emax advertise that the shafts are hardened. I would be surprised frankly if the DJI shafts are not, as it's not a hugely expensive thing to do and has lots of advantages.

S-5525 Shaft Kit - Scorpion Power System
http://www.merqc.com/files/Datasheet/emax.pdf

There will also be an ounce or so of mild steel in the stator. If you know of any certification standards that suggest a jet engine should be able to ingest four of these without becoming very unhappy indeed - or even some smaller steel items - then please post links to them.

Last edited by abgd; 19th Apr 2016 at 07:50.
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Old 18th Apr 2016, 22:15
  #115 (permalink)  
 
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The blanket jamming of a range of frequencies is against international agreements, so would be highly illegal. Law enforcement and the military may exercise limited exemptions when dealing with specific incidents such as suspect packages.

The majority of drones use the same band of frequencies as wifi internet routers, so jamming the airwaves around airports would deny local residents use of wifi. In any case the drones use complex software algorithms to be able to receive (and transmit) control signals through heavy interference. Even the cheapest toy drones will automatically tune to the clearest, most interference free radio channel while pairing with a controller. Most will also automatically change frequncy to another channel if the control signal is lost for any reason.

The actual radio transmitters and receivers used are mass produced and not particularly well tuned. Tolerances are a bit broad as you might expect with items built to the lowest cost. However these shortfalls can be countered by using software to filter out the wanted signals from interference and jamming. It is far cheaper to write some computer software than spend money on tight engineering design.

Jamming signals are just not effective in modern digital radio systems.
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Old 18th Apr 2016, 23:44
  #116 (permalink)  
 
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p.s. utter tosh. The risks are to the cockpit or engines. The stabiliser will be structurally fine.

I am well aware of the risks of birdstrikes

my fair share including birds that have got through the metal of my aircraft on occasion

The only new bit of info is that in at least this case it caused no damage.
Not quite. Subject to more information, what we know is that this incident may have resulted in damage that did not result in a cancelled, or significantly delayed flight.
The actual damage caused may well have been temporarily handled within the scope of the MEL/CDL (or whatever relevant document)
The costs incurred may well be paid for after this subject is no longer news worthy
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Old 18th Apr 2016, 23:50
  #117 (permalink)  
 
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I have not heard of anyone yet hacking DJi's code, maybe I am wrong and it can be done but nothing on the forums i have seen. You run the risk of bricking it.
No firmware hack required. Simply cover the GPS antenna with tin foil and fly in Atti mode.

Also I believe with the upcoming GEO System firmware users will be able to "self-certify" that they have authorization to fly near an airport (>1.5mi), and deactivate geofencing themselves via a code from DJI's website. All you need is a DJI account which can easily be set up anonymously.

Similarly on DJI's larger, "pro" oriented drones / flight controllers (e.g., A2) one can simply turn off geofencing.
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Old 19th Apr 2016, 07:34
  #118 (permalink)  
 
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Honestly I'm trying to post this TIC but given some of the posts I've read this seems somewhat appropriate. You know who you are....

Drone pilot furious after ?uninsured? passenger jet crashes into him
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Old 19th Apr 2016, 07:52
  #119 (permalink)  
 
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This, if anything, suggests that the doom mongers are over-egging things.

Drone hits plane.
Plane not damaged.
Initial indications from an initially miniscule research set suggests that drone strikes do not hurt aircraft. As more collisions happen, I'm quite sure that eventually one will go down an engine. That will be more indicative of whether there is actually a problem.
Ummm...NASA used similar logic twice with less than impressive results.

Solid Rocket Booster partial O-Ring burn throughs happened on several occasions early in the shuttle programme. Flagged up by engineers and other "doom mongers" such as John Young as an accident waiting to happen but not acted on: Result was the Challenger accident and FWIW Richard Feynman's statement that "nature cannot be fooled"...

Foam strikes damaged Shuttle orbiter tiles on multiple occasions..again engineers, no doubt again being "doom mongers", had serious concerns.. but that problem was not acted upon because it was inconvenient and difficult to do so. It was only after the Columbia accident that it was decided to run a full scale test of a block of insulating foam hitting a wing LE at a representative velocity....

I don't want to see a ban on drones, but I'm finding it hard to understand the apparent reluctance of some to accept that it might be not be a good idea for unregulated drones to be sharing the same airspace as commercial air traffic.

Last edited by wiggy; 19th Apr 2016 at 08:22.
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Old 19th Apr 2016, 08:22
  #120 (permalink)  
 
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"Incident was harmless"

[QUOTE=Kitiara;9347149]This particular incident appears to have been harmless.

But it does serve to further underline the issue that drones present a very real and immediate danger to commercial aviation.

Like I say, this incident was harmless, but it doesn't take too much imagination to consider what a person with malicious intent and an armed drone could achieve.[/QUOTE
A few feet left or right could easily have resulted in engine ingestion. Costing a carrier a couple of quid (£s). There but for the grace ........" Harmless?
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