Terrorists and UAV’s: reader feedback and further issues

In reader comments to yesterday’s post about terrorists planning to use UAV’s against aircraft, I feel that a few very important points are being missed.

The first is that our opinion of whether or not such low-powered, quadcopter UAV’s have any chance of success is basically irrelevant.  ISIS terrorists do not share that opinion.  They have already ‘weaponized’ such drones and used them against enemy ground forces in Iraq and Syria.  They see no reason why they should not do so in the West as well.  Furthermore, it has now been demonstrated that they intend to try to use them against aircraft.  Thus, it’s irrelevant whether we think they can or will be successful in the attempt.  They are going to try anyway. They just did, in Turkey.

Second, attempted attacks are perhaps even more important to terrorists than successful attacks.  The mere existence of such terrorist-operated UAV’s will force airlines to suspend operations in affected areas until the threat is removed.  They simply cannot afford to operate there, no matter how often airports and security authorities play down the chances of success.  Let there be just one successful attack, killing a hundred or more passengers and crew, and the resultant lawsuits against the airline will probably be enough to cripple, if not bankrupt it.  Just think of the legal liability it will incur if it flies its aircraft into or out of an airport where there is known to be a threat of terrorist UAV activity.  It can’t plead an ‘act of God’ or an ‘act of war’ or whatever.  It chose to operate there;  therefore, it knowingly exposed itself to liability.  That’s a legal death sentence.

In that light, consider that an attack only has to frighten off potential passengers.  What if a terrorist flies a UAV, carrying a small explosive device, close to the inbound flight path of an arriving airliner, and detonates it where passengers in the air, and passersby on the ground, can see the explosion?  Instantly, a huge proportion of the passengers flying into and out of that airport will cancel their flights, and cargo shippers will seek alternate facilities.  They’d be fools not to do so, after all.  The terrorist won’t have to actually damage or destroy an aircraft to produce an effect just as deadly to all the commerce and industry depending on that airport.  In exchange for a cheap, home-built UAV and a few ounces of home-brewed explosive, the perpetrators will inflict millions of dollars in economic damage.  That’s a worthwhile exchange, from their perspective – and it’s one we can’t afford.

Thirdly, a number of commenters suggested that it would be very difficult indeed to fly a UAV into the path of an incoming airliner.  However, I think that’s looking at the problem from the wrong direction.  Remember, flight paths approaching and departing from a runway are widely known – in fact, they’re published for all pilots (and other interested parties) to read for themselves.  Courses, angles of approach, radio beacons, guide slope signals, etc. are all out there for anyone to see.

A terrorist (or a pilot who can advise and/or train terrorists) will know that he only has to put his UAV inside a narrow window of space, through which he knows an airliner must and will fly, in order to threaten it.  The glide path is a known factor.  If he can put his UAV within a few hundred feet of that path, vertically and/or horizontally, he’s guaranteed to pose a threat to any aircraft;  and if he can position it more or less exactly on the glide path, the threat increases even more.  Many aircraft now follow that glide path slavishly under computer control, not relying on pilots to do so (because computer control is more precise, and crowded airspaces require greater precision).  Therefore, the odds of a collision go up exponentially.

What’s more, if a terrorist or terrorists can put multiple UAV’s into the same narrow window of space and time, the threat to aircraft using the glide path increases even further.  All it will take is a few hobbyist drones, a few small packages of home-made explosives, and a few operators with remote control units, who might be a couple of miles or more from the scene of action.  I suggest airport security authorities will find it extraordinarily difficult to prevent or deal with such an attack.

Some readers suggested terrorists would be better advised to fly a drone into power lines, or use an explosive-laden drone to attack critical infrastructure like airport radar systems and the like.  I think such attacks are very likely.  I recently mentioned the problem of, say, a series of UAV’s attacking transformer stations scattered around a city.  That would lead to widespread blackouts, with predictable results.  However, I don’t think that the greater ease of such attacks should blind us to the terrorists’ need for spectacle.

One crashed airliner will attract headlines and screams of panic around the world.  It will only take one . . . and the airline and travel industries will be devastated.  To the terrorists, that’s a result worth striving for.  They can afford dozens, even hundreds, of failures.  They only have to succeed once.



  1. Peter, there's a key aspect you're missing.

    Replace Drone with Firearm.

    Does a strict control on a particular tool stop terrorists and criminals? Or if the tool become hard to reach does it then transfer over to other methods?

    How does mandatory registration of X stop criminal misuse of X?

    It's not like every drone's parts are micro stamped with the SN. There's a SN on the body that, iinm is a barcode that can be scraped off. The FAA N Numbers for drones are something the user applies. There's no registration at the point of purchase.

  2. Peter is absolutely right on. These are TERRORISTS. They don't NEED a kill. Their goal is disruption of our culture, our economy and our ability to influence THEIR culture. Stacking bodies is a side benefit.

    Additionally, I'm pretty sure that an aircraft could be legitimately harmed with the creative use of UAV/RPV/RC/Drone technology. I'm not going to speculate on specific methodologies in public (I'm pretty sure the FAA wouldn't think it was funny, and they know where I live) but there has been plenty of speculation in public already. 'nuff said.


  3. Its funny how Radical Islam will denounce the West as too modern, but will use the West's technology against us at the drop of a hat.

    Our host is right – success is not highly important. Its the example that their people are making the attempt that is supposed to encourage other Muslims that these attacks occur.

    They want more martyrs, plain and simple.

  4. As others have already pointed out, they don't need a total success, even though they'd welcome one. Disrupting normal life, costing time, money, and inconvenience counts as a "win" from the terrorist's viewpoint.

    Your point about "known glide paths" is spot-on. There was recently a near-crash in San Francisco when an airliner mistakenly started a landing approach on a taxiway rather than on the runway that it paralleled. From the news stories, the apparent cause was that the pilot *hadn't* slaved his approach to the automation, and the proposed fix is that *all* approaches must be under computer control. Not only does it make their paths more predictable, it slows any response to unexpected attacks since the humans need to take back control before dodging. I'm also, perhaps cynically, quite certain that pilots will be less likely to detect problems since "that's the computer's job".

  5. The same complaint is true of having airliners themselves, as demonstrated on 9/11/01.

    So civilization has a simple choice: get rid of airliners, UAVs, guns, and everything else terrorists will use. Down to rocks and pointy sticks.

    Formerly Great Britain is trying that exact approach.
    Anyone thereabouts should file a success report at their convenience.

    Or, we can get rid of terrorists.

    I know which one I'd choose, even at the cost of the occasional, even spectacularly so, failure.

  6. I pooh-poohed the likelihood of little consumer-grade drones having any realistic chance of success at actually bringing down an airliner. Terrorism to me means causing actual terror, not inconvenience, concern, and economic impact. It's a kind of guerrilla warfare, for sure, but not terrorism. But I also said that they would be great at that. At least once. And I don't think anybody said anything about jihadist nutjobs with Wile E. Coyote-like imaginations not wanting to try, or not being too dumb to realize there are better ways to try to down a plane. There's certainly no glory in shutting down a runway for period of time, even if you manage it more than once. And THAT capability has been around for decades with R/C planes. There's a threat, but it's mostly nuisance. How big a drone would be needed to reliably fly in a zone with wake vortices galore, anyway? That makes a successful attempt at a large airport less likely, but smaller airports with less frequent arrivals or departures would be easier. But nowhere near as much a harassment impact.

    Largish unguided solid-fuel rockets would be even more effective at shutting down an airport as everyone's first thought would be a MANPAD, a far more dangerous proposition, though the chances of even one of those actually bringing down a modern airliner isn't that good.

    Yes, they're a threat, but so are high-powered rifles.

  7. Yeah, yeah, yeah. And we are all supposed to clutch at our pearls and wail in fright about the free and easy availability of assault rifles with 'that black shoulder thing that flips up" and Glocks are invisible to airport x-ray machines…

    Let's game it out, Pete. I've built these things, configured and programmed them and flown them both in line of sight and FPV modes. Let's blow up an airliner!

    Anything we get from a hobby shop or build is probably going to be run on lipo batteries. Best case scenario is a 15 minute flight time. Cut 5 minutes off that if we have to maneuver in turbulence or fly at full throttle. We will not be blowing aircraft out of the sky from miles away. Fact is we will have to be sitting pretty damn close to the target. It is very likely that if we make any attempt we will probably be seen. The major airports I've seen are heavily patrolled and getting within range is going to be a major obstacle. Getting away afterward is going to be even tougher, assuming we are successful.

    Our payload is measured in ounces, best case scenario. If we have a camera on board, it is better measured in grams. Can you conjure up an jet killer with a couple grams of explosives? (I'm asking because I don't know).

    Our FPV camera is most likely powered by a 500~600 mW transmitter. Because airports are a veritable chit storm of EM noise what with radio, radar and all that other good stuff – we are going to have a rat of a time piloting our drone. Expect your FPV cams to operate on the south side of 'dismal'. All your channels will be spotty and I dunno about you, but I don't want to be around an armed bomb triggered on a radio that can barely function in a mess like that. There is a very real risk of inadvertent detonation.

    For us to menace a passenger jet we are going to need to spend huge $$$$ on heavy lift motors, special batteries to run them – and still have problems flying it and arming it. Last I heard you could buy shoulder fired missiles for around $85k US – and the Chinese clones are even less.

    It just doesn't make sense.

    In fact, given all the fake news lately, I strongly doubt ISIS was blowing up their enemies with commonly available drones. The boys in the other thread were right: the best thing they could do would be fly one into the intake of a jet engine. If they do something like that in today's political climate – it's game over for the multi-culti crowd as Americans will have to start thinking of their personal safety – and if that means deporting moslem mudflaps…?

    I say there's better things to worry about!

  8. people with ill intent could always have done it with variety of vehicles. Radio control vehicles have been around for long time, but only recently has automation technology have allowed such vehicle to be usable by anyone and with autonomous and with fpv capability. like it or not though, the cat is out of the bag, and the ubiquitous nature makes them tougher to keep them out of hand of people that have ill intent. The madness is in allowing risky population into the country uncontrolled. it is not if, but when we will have terrorist event involving such vehicle.

  9. David Lang writes:

    Even if multi-rotor copters are a real threat to airlines, regulation/registration of them is not the answer. They are just too easy to build from parts. As others have noted, any serial numbers can easily be removed, but with all the parts being things that are incredibly useful for many tasks, there workload to try and track the manufacture and sale of the parts would be incredible.

    So trying to regulate them is just not the answer.

  10. Looking through today and yesterday's post and comments I'm not convinced that it would be impossible or even very difficult to get a UAV to impact a plane in flight. How much damage that would do to the plane is also debatable and the terrorists really would like to cause a crash.

    As was mentioned takeoff and landing are the easy places to target but the takeoff is much more productive for a terrorist for several reasons. At takeoff there is more fuel on-board in most cases, the impact spot will likely be in the community, not on the airfield and the plane is likely to be an easier target when ascending.

    If it is actually very difficult to hit a plane as it takes off there is a second point where an attack could still be very effective while minimizing the difficulty.

    Hit the plane on the taxiway between the terminal and runway. Maybe hit the first in line when things are busy and then since the other planes in the queue are trapped, hit them too. It can't be too difficult to get a 2 ounce thermite charge to a spot on the wing over a fuel tank. Maybe the first pilot could taxi the damaged plane out of the burning fuel spill if they are quick and lucky, not so sure about the folks behind them though.

    UAV Swarm and Thermite

    Here is the Phoenix airport, there are plenty of good spots to launch a drone attack within a couple thousand feet of the runway ends.


  11. Actually, the technology for this (in much simpler and cruder form) has existed for over 50 years (as Larry pointed out above): RC model aircraft. The biggest differences are the modern stuff is VTOL and battery powered, and, as such, has more precise motion control than the antique equipment many of us played with as kids. Still, something with wings, which would allow a much higher forward velocity, that has tungsten rods in the wingspan and the length of the fuselage, might pose a threat to engines, but it would still require mastery of the spacial mechanics of a rather tight 4D problem: time and the X,Y and Z axes.

    If the goal is to weaponize the energy of the moving mass of an airliner, the two critical points are after V1 but before V2 on takeoff, and the last 30 seconds before touchdown on landing.

    The 3D location of aircraft during those two periods is highly predictable, to within a couple meters.

    More fuel=more fire=greater destruction? Sure, concentrating on takeoff is better, but…airlines routinely over-fuel aircraft going from airport X to airport Y to airport Z, despite the additional cost of hauling extra fuel around, because fuel is cheaper at X and turnaround times don't allow for fueling at Y and Z, so if one knows flight schedules and the operational doctrine of particular airlines, it's not hard to find a plane with a 70% fuel load landing. 70% isn't 95%, but given that 70% will still be thousands of gallons, the difference is largely academic.

    Still, despite flight path predictability there's the problem of hitting a moving target in a particular area with enough precision to accomplish the terrorist's job; a couple feet one way or another bounces the drone off the wing's leading edge instead of into the engine, despite the large low pressure area at the turbine intake. And, don't forget the amount of turbulence present, especially during landing. Flying, landing and taking off airliners are deliberately separated horizontally for a reason; the air disturbance caused by one, especially a large aircraft, remains present for a few minutes after the airplane passes through that glide path "box," and the effect is quite noticeable even when the following airliner weighs 100 tons. To a 5-7 pound drone, well, good luck with achieving an extremely precise 3D point near the center of the glide path. Not impossible, but highly difficult.

    Could a VTOL drone with a 2 lb explosive payload be used in a "pop-up" capability near the end of a runway? Probably, but the critical zone for success is pretty small, and, first, most airports have long enough runways for most airliners to achieve V2 over the concrete, some – like Reagan National – may have susceptability because of short runways that end just before water, allowing some sort of floating device to carry a drone close enough, but that's a physical problem solved by fencing.

    If – and it's a big if – they could get close enough, a swarm of VTOL drones with small shaped charges could pose a threat to the "conga line," that herd of airliners queued up nose-to-tail at places like LAX, LGA, ATL, MCO, et al on Friday or Sunday evenings.

    The threat, while not zero, is fairly small and sufficiently limited in scope that cogent and technically competent personnel should be able to defeat it. That, however, is the real weak point: "cogent", "competent" and "government" very rarely co-exist.

  12. Explosives? Why not a chunk of re-bar. Think about what that would do to a turbine.

    And RC aircraft aren't the only threat. Kites, balloons, shotguns, there have to be any number of ways to do damage to an aircraft low and slow.

    Focusing on the weapons does no real good. It makes it look like the Powers That Be are Doing Something, but, like the TSA, doesn't really make it any safer.

  13. I find it funny how much the "don't ban guns, they're just a tool" and the "ban drones, they're dangerous" crowds overlap. Somehow they don't seem to notice the cognitive dissonance.

  14. Our payload is measured in ounces, best case scenario. If we have a camera on board, it is better measured in grams. Can you conjure up an jet killer with a couple grams of explosives? (I'm asking because I don't know).

    Explosives? Why not a chunk of re-bar. Think about what that would do to a turbine.

    Actually, not even rebar. If the drone goes through the engine, the engine will have to be inspected; on plane, 2-4 hours at least. That plane is out of commission, and all the economic considerations Peter mentioned come into play. If I recall correctly, terrorists shut down an airport by lobbing an occasional mortar shell onto a runway or hanger. The insurance companies declared losses there would not be covered due to the Act of War clause, and no one wanted to risk $30 – 100 MM aircraft. (Tamil Tigers in Sri Lanka?) Another Sri Lanka terror group launched an assault on the airport in 2001, destroying 26 military aircraft and 3 civilian Airbus airliners (1/3 of SriLankan Airlines fleet).

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