Can a SDR crash a plane ? - Page 1
Forum section: electronics / rf-microwave

author: Georgi
author_rank: Contributor
timestamp: August 18, 2018, 09:57:17 am
content: Here is something that has been on my mind for a while:Is it possible to mess an airplane communication system with a SDR dongle (Lets take the USRP b210 as an example), to such an extend that it crashes. If not,what are the potential problems (if any) that can be cause by such a device on board (transmit power usually 100mW). I am asking this, because I have met with some colleagues during conferences who traveled with these devices on a plane and never had any problem boarding with them, because they told the that this is a research equipment (Which is the truth). So if someone would provide some clarification on the matter, I would be very thankful.RegardsGeorgi

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 10:04:55 am
content: QuoteWhy would this cause any issues with boarding? It is allowed to carry transmitters as long as they are switched off.

author: Georgi
author_rank: Contributor
timestamp: August 18, 2018, 10:07:45 am
content: Because you can switch them on very easily once you are on the plain (assuming you want to cause some trouble)?

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 10:10:42 am
content: You can switch on whatever, including mobile phone. And there is no quick way to determine at which frequencies device can operate. You are basically inventing non existing rules prohibiting transmitters.

author: sokoloff
author_rank: Super Contributor
timestamp: August 18, 2018, 12:10:33 pm
content: Transmitters in passenger's possession are barred from transmitting by most airline OpSpecs. (Some allow wifi/BT. It will be made clear in the pax announcement.) The operator (the airline in this case) is allowed to permit certain devices under14 CFR 91.21.b.5(for US law).In terms of what you could do intentionally, it's fairly easy to disrupt GPS reception (which would be detectable by the flight crew and at worst would be likely to result in a diversion to an airport served by a ground-based precision approach if in poor weather or a visual approach to the intended airport in good weather). It's harder to disrupt the ground-based approach navaids (typically a localizer and glideslope) because of the much higher power levels of the proper aids and the location of the pax cabin in relation to the receiving antennae. You could try spoofing ADS-B or voice transmissions, again likely with limited effect.I would imagine that if you managed to cause actual disruption or diversion to an alternate airport, it wouldn't be hard to taxi the airplane to the gate and have it met by police who could investigate everyone on board and their carryon articles. If found to be intentional, you'd be looking at a terrorism charge, just like the shoe and underwear bombers...As other posters have said, there's no prohibition on carrying transmitters in the off state.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 01:44:43 pm
content: I wonder if planes will eventually be equipped with SDR/SA/Recivers connected to intelligent programs to detect belligerent transmitters so the air marshal can deal with the situation without crazy shit like the movie 'executive decision', or at least be able to find malfunctioning consumer electronics that end up jamming due to some weird failure mode, crime and stupidity aside.I would imagine that 100mW of transmit power would probably not effect avionics equipment unless there is a unshielded location you put the antenna into and it happens to disrupt a MCU, or you manage to overwhelm a input amplifier to a communications receive system. If the system is severely degraded due to lack of maintenance/damage from surges/etc maybe you can get more effects.I would personally say its a bad idea in general to do any kind of testing no matter how small on a flight with a bunch of people that paid for a service however, IMO it should be done on a empty plane with a willing pilot. It has a serious 'mad scientist' vibe. I am anxious enough about complicated travel methods like that, that I would ask you to turn it off if I saw it. I just wanna get to where I am going, if I will be a guinea pig in a experiment of any sort I would like to be compensated for it and be able to make the decision to participate.Empty plane, willing pilot, etc.. at least you can get some parachutes maybe, and alert rescue operations to be on higher alert to your fight so you don't disappear into the ocean. Not to mention you can properly setup your RF system by running coaxial lines and setting up antennas all over the plane, using quality test eqipment... the experiment would be better then some kind of half assed james bond scientist shit hiding a 5$ SDR under your trench coat so the old ladies don't freak out.It feels kind of like participating in someones science experiment that has no appreciation for the danger/precision required for flight. I would want people to stick to the specifications.Also if you have a transmit capability thats broadband connected to a laptop made by some people for a hobby setting you don't really have a good idea if the software is working properly, you might be inadvertently transmitting because of a software bug, this kind of thing should have isolated receive equipment so the technician may detect bad operating modes, like there should be a commercial SA setup next to you to monitor the transmitter, harmonics, stuff like that.There can be hundreds of people on board, this decision should not be left up to a damn internet hobby forum.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 18, 2018, 03:02:23 pm
content: Quote from: Georgi on August 18, 2018, 09:57:17 amPlanes are not flown by communication systems, but by pilots.The best chance to crash a plane by an rogue transmitter is if some other equipment is not immune to some frequency, causing noise in a system.But equipment on planes is thoroughly tested...What you can do is mess up the navigationsandcommunications, but to "crash" the plane you'll have to hold this out until you're out of fuel.If all navigations (radio and gps) stop working, the pilots will notice and fly by hand to a near airport for technical difficulties.If all communications fail, the pilots will be greeted by nearby F16's if they enter an controlled airspace.If both fail,andthe pilots you're on a ocean flight... it will depend on the pilots skill to navigate by compass.So, it can be a factor in a crash. Since there never is one cause.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 03:09:53 pm
content: Quote from: Jeroen3 on August 18, 2018, 03:02:23 pmyes but if something goes to a higher impedance due to whatever reason, a filter gets shorted, shield panel falls off, etc, you can have a problem.. is it really necessary to run experiments on planes filled with travelers? I see it as a MKULTRA type mindset. I am usually happy enough the damn thing did not get hit by a flock of birds or get otherwise assaulted... let alone that someones rogue experiment worked as anticipated. Of all the things you can fuck up with RF, a planes seems really up there as to consequences.What is so fascinating about the electromagnetic environment inside of a boeing that people wanna risk any kind of complication to run some RF experiment??? It seems like something you would do just because it sounds cool rather then for any real benefit.You can probobly get alot more interesting data from a small Cesna then trying to misuse airlines for amature radio research???

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 03:20:56 pm
content: Quote from: coppercone2 on August 18, 2018, 03:09:53 pmExample you wrote is simply ridiculous. Filter gets shorted and the thing continue to work normally until someone switches on transmitter?You'd need the stars align on the sky for something like this to happen. When you waste time and money fighting imaginary problems, you will have no resources left to address real ones.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 03:22:47 pm
content: Why would you even risk a airliner that is filled with people to run a amature experiment with no tangible value? I am not bored/crazy enough to do that. People will just think you are insane.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 03:25:28 pm
content: Quote from: coppercone2 on August 18, 2018, 03:22:47 pmI did not notice any intention to run experiment.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 03:27:29 pm
content: Quote from: wraper on August 18, 2018, 03:25:28 pmhe said his friends bring SDR on board and its allowed, Read first post please.' I have met with some colleagues during conferences who traveled with these devices on a plane and never had any problem boarding with them, because they told the that this is a research equipment (Which is the truth).So if someone would provide some clarification on the matter, I would be very thankful.'I think they are very bored and careless researchers. I don't see why the question would be even asked if it was just brought on board as inert cargo. I don't think the designers of these planes in the 1970's though that there would be personal broadband digital transmitters in the cabin.And I have personally inspected equipment that for reasons still unknown to me had MOLTEN shorted input inductors on the ADC signal path (meant as a HF compliance filter) that lead into a ADC that still kinda worked. You can only tell with close inspection that the package was bulging and had a point discoloration and then if you measure it you got a dead short at DC. Connected to a isolated floating sensor. Damage was consistent with thermal/overcurrent. And this was small time stuff. If you were old you needed to use a optical magnifier to notice the damage. If I was not a diligent engineer I would not have noticed it, I had to observe it close up carefully under bright light to see it.. if I did not notice the fault it would just get a replaced ADC or whatever the first signal chain semiconductor was and get shipped back to customer (where they would by default probobly blame their handling and chalk it up to ESD, but ESD does not freakinmeltinductors!) If this happened it would work great, so long you don't mind there not being any functioning inductors in the signal chain! Other professionals who say this were basically dumbfounded by the damage, it was completely bizarre... everything looked tip top.Like the package started to mushroom and discolor on the top over the bobbin. SMD parts 0805 I think, rated for 50 or 100mA I think. 2 EE's, 1 general manager engineer and 2 experienced (15+ year) technicians (one of which was practically a multidisciplinary engineer) could not figure out why (customer used system as sub assembly). Turned into some kind of bureaucratic blame game and I did not see the final result due to departure. The inclination was to give the customer replacements and hope it does not happen again.The damage occurred to several units that tested fine and sold in a large batch, and the units used the same inductors all over the place, they were only damaged in that one signal chain input. The purchaser could not isolate the fault to any particular system, the claim was that the failure was random, and our basic questions about their wiring scheme in their product did not result in any obvious red flags (i.e. are you running it parallel to heavy conductors in a cable assembly, is there any signs of fraying/insulation damage, high voltages, field collapses, RF signals, etc). Communications about this problem were spread out over like 1 year with no obvious solution due to distance and priority.

author: Jr460
author_rank: Regular Contributor
timestamp: August 18, 2018, 03:42:55 pm
content: Let's look at a small plane first.VFR flying the plane needs zero electrical system for it to fly. Other than an electric turn and bank indicator everything else is mechanical or air driven. The engine uses magnetos rather than an automotive type system. (BTW, I've had a completely electrical system failure happen at night. Shock for few seconds, and then you do it just like in training and fly the plane).So yea, come on my plane with some sort of RF source to try and screw with things. If I find out, I'm PIC, my word is final like the captain of ship, you will be getting off the plane.Now IFR flying. GPS, yea easy to jam, but you are not going to provide false readings, I'll get a RAIM alert. VHF nav aids, yea, maybe you can cause an issue, or block comms, but that is why we have more than one and cross check all the time. But the rule in an plane is to Aviate, Navigate, and then Communicate in that order. So I'll have instruments that keep the plane flying just fine. I should know the minimum safe altitude in the area, and if I know the base of the clouds, just go down until I break out and then fly VFR.Big planes. The unknown to me is how well the fly-by-wire systems are the shielded. However most the same things apply.Please do not go into the movie Die Hard II, you are not going to crash a plane into the ground. So many things wrong with that plot.

author: Rerouter
author_rank: Super Contributor
timestamp: August 18, 2018, 03:50:30 pm
content: The A380 autopilot responds to the unencrypted and well documented position / heading messages of other nearby planes aswell as a Ping-pong system with a ~250ms lag time,there are black hat talks about this, Pretty much while the plane is in autopilot mode, you have enough margin to suddenly tell the plane there is another 100m off from one of its wings, And it would react accordingly to try and avoid an intercept. To my knowledge no one followed up with a qualification of exactly how significant that reaction would be, but It would show up on the data logs, and the plane would likely be fully debriefed, however the pilots are always able to turn off the autopilot and disable the response from these systems, so a crash I would say no. temporary steering, yes.Again planes use an automated landing system at certain runways, now that is the most horrifying thing I can think of. as I believe another blackhat found it was spoof-able and the number of active radars was being reduced. Asking the question of what happens if you offset the ground by 100m, or the position so the plane comes up short, These ones would be hard for a pilot to correct for. and would come down to how paranoid they where of the automated systems.

author: janoc
author_rank: Super Contributor
timestamp: August 18, 2018, 03:54:27 pm
content: Quote from: Georgi on August 18, 2018, 09:57:17 amYou can board with almost whatever you want - the exceptions are listed every time when you buy a plane ticket or typically next to every check-in counter (explosives, guns, compressed gases, flammable liquids - that sort of stuff. See e.g. here:http://www.airsafe.com/danger.htm). Radios of any kind are not banned, neither in the cabin nor in the hold.Operating the equipment containing oscillators/transmitterswhile in flightis another matter and typically is prohibited for safety reasons as a matter of precaution. However, that doesn't mean if someone does this it will crash a plane! It is extremely unlikely a 100mW SDR device will cause any serious issues - at best it will knock out some navigation signals which will likely cause the autopilot to disconnect automatically. That's very much a non-event that happens regularly on almost every flight for all sorts of reasons.The chances of and SDR causing significant interference with the controls (e.g. on FBW planes like Airbuses or the new Dreamliner) to the point of losing control (and crashing) are slim to none - remember that many planes have wifi on board, there are several radios in the cockpit with the wiring and antennas all over the plane, there are most likely at least several passengers on board that forgot to turn off their cell phones on every flight, etc. And all of these things have much larger power output than your puny 100mW into a crappy short antenna. Not to mention that you are sitting inside a huge Faraday cage while the wiring is effectively outside of it (in the fuselage walls).Either way, if you somehow manage to cause sufficient interference this is bound to be noticed quickly because such failures trigger alarms in the cockpit and the crew will take over. So the chances of "driving a plane into the ground" by a gadget like this are slim to none, IMO.OTOH, if the source of interference is identified as a passenger device and you don't turn it off when asked to by the crew, then you are pretty much guaranteed a large fine as a minimum and a possible prosecution with a very severe prison sentence in the worst case. Endangering an aircraft/interfering with the flight crew are serious offenses, so this is really a very idiotic place where to be messing around.

author: sokoloff
author_rank: Super Contributor
timestamp: August 18, 2018, 04:00:31 pm
content: If anyone wants to conduct legitimate research on this, the answer is to charter an aircraft, go fly and experiment away (with the consent and awareness of the pilot or flight crew).Some part 135 (on-demand/charter) OpSpecs will also prohibit transmitters by pax, but I suspect most will leave it to PIC discretion. You could experiment on any size aircraft that you wallet supports.

author: janoc
author_rank: Super Contributor
timestamp: August 18, 2018, 04:19:26 pm
content: Quote from: Rerouter on August 18, 2018, 03:50:30 pmThat is most likely the TCAS collision avoidance system. See here:https://en.wikipedia.org/wiki/Traffic_collision_avoidance_systemand:https://www.airbus.com/newsroom/press-releases/en/2009/08/easa-certifies-new-autopilot-flight-director-tcas-mode-for-a380.htmlQuoteIt would be likely a non-event. Spurious TCAS warnings are common, especially in a busy airspace (e.g. around airports). The A380 case is a bit special because the autopilot can actually perform an avoidance maneuver automatically (most other planes will only warn the crew and the pilot has to actually turn the plane).So a plane "suddenly appearing 100m off from one of its wings" is nonsense that pretty much is a guaranteed false alarm. Both because there is no way for a plane with a working transponder (no transponder = no TCAS warning neither) to get there in a controlled airspace (separation minima - 15NM lateral separation and 300/600m vertical one, see:https://www.skybrary.aero/index.php/Separation_Standards) and because in such case the ATC would have been screaming at the crew for a long time already (separation losses trigger alarms on their consoles).Also the TCAS doesn't work with only position, it calculates an actual closing rate and only if the conflicting traffic is on a trajectory that could cause a collision, a warning (either a traffic advisory or the more severe resolution advisory that has to be followed) is triggered. A spurious "plane" that has popped out of nowhere with "no history" would pretty much get ignored as false. The crew has situational awareness from the radio traffic and if they never heard the ATC to talk to a plane they suddenly see on their screen near them it would definitely trigger questions.If the signal has been there for a while, simulating a non-communicating plane on a conflicting trajectory, then the crew would have time to talk to the ATC about it (you are supposed to tell the ATC you are getting TCAS warning in order to not cause a collision by avoiding another one). The offending false transponder signal would also likely show up on the ATC screens too, prompting someone to look into it.And even in the worst case, if the attacker somehow managed to convince the A380 autopilot/flight director to change course (likely to climb/descend, TCAS never orders turns because they are slower than diving/ascending and you are more likely to turn into traffic), the crew would again see it right away and react. (no, you can't drive a A380 into ground with a TCAS warning neither - TCAS is inhibited below 1000ft/~300m by design).

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 04:28:18 pm
content: Quote from: coppercone2 on August 18, 2018, 03:27:29 pmThey brought it on board, so what? It is not prohibited. It's fine as long as you don't turn on. Or would you fantasize further that it will turn itself on, and on particular settings to crash the plane?

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 04:37:46 pm
content: Quote from: wraper on August 18, 2018, 04:28:18 pmhe asked if it could damage the plane, you would need to jam it into the pilot to do so without turning it out. what is your point?Obviously anything is fine if you dont turn it on, you can bring a container of nerve gas, a box of plutonium or a rabid bear inside of a cage so long you don't turn any of them on? Do you want the discussion to be limited to strict interpretation of airport law? I don't think the HAM radio forum on a technical engineering forum is a good place for interpretation of laws setup by the transportation agencies and airports.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 04:42:12 pm
content: Quote from: coppercone2 on August 18, 2018, 04:37:46 pmDo you understand the difference between asking if it may potentially cause any damage and actually intending to turning it on inside the plane? Also comparing SDR with container of nerve gas is forcing me doubt your sanity.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 04:43:23 pm
content: Quote from: wraper on August 18, 2018, 04:42:12 pmHow could a PCB cause any damage being on a plane dormant?Thats absurd and does not merit a thread. I am done with this aspect of the discussion thanks.

author: wraper
author_rank: Unknown
timestamp: August 18, 2018, 04:45:11 pm
content: Quote from: coppercone2 on August 18, 2018, 04:43:23 pmIf I ask if suspected poison is actually poisonous, does it mean I intend to poison someone?

author: Howardlong
author_rank: Super Contributor
timestamp: August 18, 2018, 04:48:54 pm
content: It’s incredibly easy to disrupt avionics without even touching an SDR. Should you choose one could cause serious disruption with just one $200 handheld airband transceiver, but you won’t make any friends, and you’ll be found very quickly. (I can tell you that from personal experience as a perp of inadvertent transmissions as a pilot myself when doing the odd radio check to debug a problem - they’ll usually be able to DF you and correct you before you’ve worked it out yourself).The only facet of SDR that lends itself to being supposedly easier is that things like modulation and coding are software configurable, but you have to write that pesky software first. Frequency agility, for example, is not at all unique to SDR. Jamming, for example, including spread spectrum techniques, has been around long before SDR.Avionics frequencies, together with their modulation and coding techniques, are well known and well defined. They are based on many decades of technology and standardisation and have stood the test of time, but they are incredibly open to disruption. There are also many backup systems.Frankly I don’t see SDR as being a particular enabler, at the end of the day if you know enough and are of a particular bent, with or without an SDR you can cause plenty of damage, and if you do, you’ll have the book thrown at you.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 18, 2018, 04:54:03 pm
content: [I have been a pilot for 15 years]The ILS system is the most vulnerable because it is used to land the plane in very low visibility. In general, however, you would need a lot of power to have any impact on the system. The worst you could do is cause the system to go haywire which is easy to see visually and the pilot would see the identifier cannot be decoded and hear the static on the audio monitor for the ILS. At that point, they would just choose another approach.Overall - I doubt a passenger could do much to crash a plane. They could, at most, create erroneous behaviors of VOR's, GPS, ILS, etc. even that seems unlikely.

author: ignator
author_rank: Regular Contributor
timestamp: August 18, 2018, 05:36:51 pm
content: I spent my career testing avionics for shake/bake/EMC.These are the RTCA DO-160 (Radio Technical Commission for Aeronautics, DO is a series of documents for minimum performance requirements, in this case 160 is a set of environmental tests) test requirements for radiated susceptibility tests. My product (autopilot, flight management, and ARINC429 data switch) was tested to category Y. Some products were allowed to be upset, some must operate through the test. We called this HIRF testing (High Intensity Radiated Frequency). Some systems were allowed upset as long as they did not produce misleading data, or in the case of the autopilot, produce a hard over, or slow over. Our displays (Collins Radio) would operate through these tests with no upset (our competitor "brand H" would put a big red X on their screens, allowed by regulations, as there was no misleading data).So to answer the OP, most likely the black box, and system level test done by the avionic vendor would exceed any RF field strength that a SDR local oscillator would radiate. However you don't know what coupling method could amplify this, or from a cell phone. And the airframe manufacture never would do any RF testing on their aircraft with the real wiring.I know of one RF upset event on a biz jet. A Gulfstream (I think G1) with a Honeywell system, where it had CRT display system, with remote graphics computers. These were 3 boxes all in the nose along with the AHRS (Attitude Heading Reference System), qty 2, and many other boxes. The DME box had a coaxial cable to it's antenna with a soldered connector at the mount. The ground shield came loose, which enabled the wire to spray RF through the whole system interconnect. This shut down all the avionics in the nose.The pilots used the required standby instruments which were all still mechanical.On the Folker100 airtransport airframe, our autopilot had a Cuk power supply where a large electrolytic capacitor failed open. This allowed EMI to be conducted out of the 115VAC 400Hz power wires.This noise was picked up by the wheel tachometer system, as a valid signal. Now the aircraft was on approach, coupled to the autopilot, and this system when it sensed the wheels spinning, automatically deployed the lift spoilers. Problem was the aircraft was on final approach, and suddenly lost altitude. LUCKLY the pilots recovered, but just barely.You never know what sort of EMC issues happen until they do, and the investigation sorts it out.A crash from a customer that kills all would never have a root cause understanding. A SDR represents a worst case system, especially if it is sweeping the LO.

author: james_s
author_rank: Super Contributor
timestamp: August 18, 2018, 06:04:16 pm
content: Realistically there is absolutely zero chance of a consumer SDR causing any issues whatsoever. Even if you hauled a 10kW transmitter onto the aircraft and found a way to power it up you wouldn't crash the plane. The worst you could reasonably accomplish that would be a real safety risk is to stomp on the frequencies used for radio communications with ATC. The regulations were written with an abundance of caution, not because there is any real risk of something happening.

author: Jr460
author_rank: Regular Contributor
timestamp: August 18, 2018, 06:51:18 pm
content: Quote from: Rerouter on August 18, 2018, 03:50:30 pmCAT III ILS is what you are talking about. If not needed the pilots are going to fly the CAT I or CAT II where with CAT I you break out of the clouds 200 feet above the ground.I said, don't go all Die Hard II, but you did.......ILS approaches have nothing to do with radar. They use a localizer in the VHF range and a glide slope in UHF, and many times also DME.You can't change the position of the ground. The field is at an elevation above sea level, MSL. Approach gives you the local altimeter setting. So your ALT is reading the plane's MSL and doesn't depend on anything on the ground. Even if ATC mess up and gives you something wrong, you are going to intercept the glide slope beam at the wrong spot, and know you have screwed the approach somehow and go around. But the biggest thing, is once you break out of the clouds it becomes a visual approach. So if somehow you were too low, you are going to hit DH, that is 200' for a CAT I before you break out, so you go missed. Now the big guys have ground radar with also gives them the distance to the ground so when that doesn't match, with other things, you go missed.I will not even get into required ground approach lighting and cues it gives as to the end of the runway, the VASI glide slope lights and runway lights and markings that all add to a correct and stable landing.Now to move the position of something, end of the runway for example, you would've to go out on the field and take down the glide slope antenna and physical move it. If the approach also has DME, then unless you move that antenna also, were you meet the glide slope will be wrong, go missed. Maybe you can go out and screw with the GS elements on the pole so the slope is higher or lower, but then again, you will intercept it in the wrong place, go missed again.The procedure is you ID the signals, and then while using it if the red flag drops in the instrument window, you go missed. Also some distance from the airport is an ILS monitor on the ground, if it the signal goes away, or is wrong, it causes the ISL transmitter to go down, you get a red flag, you go missed.You need to look at an approach plate. You fly the initial at a set MSL, you will intercept the glide slope signal from below at fixed point. You can tell this point from markers, DME or radial off of some other nav aid. If you get the slope early or late you may be following a false lobe, you go missed. It is not a matter of your trust of the ISL signals, it is a matter if you as the pilot messed up somehow. Go missed and sort it out.All of the above works without Radar or taking to ATC. But if those other two things are in the mix, then you would have to spoof the radar data, which would mess up all the radar tracks in the area, and ATC would know something is wrong.The final nail in the Die Hard coffin. ATC talks on the 2.5 meter VHF band, with AM modulation. You don't need any fancy to listen to or talk to planes from the ground. Up in the tower cab, (this is not the place approach controllers sit, as shown in movies, they are in a dark room at the base of the tower), they have a battery powered radio they can pull out and dial up the right frequency and listen and and talk to any plane.

author: Georgi
author_rank: Contributor
timestamp: August 18, 2018, 08:29:06 pm
content: I did not expect the discussion to go that far, but I am very grateful it did. I asked this question, because I was genuinely interested in the technical side of it. And I think you guys provided very detail information. Thank you to all who replied!RegardsGeorgi

author: bson
author_rank: Unknown
timestamp: August 25, 2018, 11:37:18 pm
content: Any RF emission will cause a magnetic compass to deviate. This in turn will produce an error in any auto pilot that relies on a magnetic compass to maintain heading. And given the lag in using GPS data to calculate heading I would assume all auto pilots use a magnetic compass, perhaps with a declination correction from the navigation plotter/planner (to permit fallback on magnetic heading in case of system failure).

author: james_s
author_rank: Super Contributor
timestamp: August 26, 2018, 12:04:46 am
content: You'd need a hell of an RF emission to cause significant deviation of a magnetic compass. Compasses are used in all sorts of vehicles, including boats that have onboard VHF radios, radar, etc. Sure if you transmit right next to the compass it might do something but I've never seen any meaningful deviation in normal use.

author: ignator
author_rank: Regular Contributor
timestamp: August 26, 2018, 12:09:10 am
content: For RF to do this, it would most likely be a HIRF event that upsets the analog electronics that is part of a AHRS/AHS system.Magnetic fields from intense magnets can be a problem.I have heard of problems where the steel rebar in the runway was handled with a magnetic crane, and causes a deviation picked up by the flux detectors in the heading circuitry.

author: bson
author_rank: Unknown
timestamp: August 26, 2018, 01:53:19 am
content: A quick test using a completely unshielded, but also relatively insensitive, consumer grade electronic compass, on a Suunto Vector, shows ANY RFI makes it deflect. Merely turning on a cheap handset (Baofeng UV-5R) in the same room makes it deflect five degrees. No keying necessary. Putting it next to an ethernet switch makes it never settle and effectively makes it output random numbers.So, no, there is no inherent immunity or lack of sensitivity - in fact, the opposite applies and it's 100% about shielding and designing for immunity. And the easiest way to improve the effectiveness of the shielding is to eliminate emissions in the first place.

author: sokoloff
author_rank: Super Contributor
timestamp: August 26, 2018, 01:54:57 am
content: Primary autopilot stabilizing signal (wing roll level and rate of turn) is (almost?) invariably provided by a gyroscopic instrument (older APs) or a modern AHRS.Magnetic anomalies or compass deviations will not upset autopilots.You're more able to cause a magnetic deviation with a nail, a coil of wire, and a battery than an SDR.By the time I'm falling back on the whiskey compass a primary means of navigation, several other things on the airplane have broken...

author: bson
author_rank: Unknown
timestamp: August 26, 2018, 02:43:37 am
content: Even a gyro needs to be disciplined to a magnetic reference or it will drift. There will always be a magnetic reference (seems to be called a slaving transmitter in aircraft terminology) and apparently it's common practice to mount these in a wingtip to minimize interference.

author: sokoloff
author_rank: Super Contributor
timestamp: August 26, 2018, 03:07:14 am
content: Quote from: bson on August 26, 2018, 02:43:37 amI've owned three aircraft. Two had no magnetic inputs to stabilize or reference the autopilot control gyro.First one had a turn coordinator based autopilot (Stec-50) that used no magnetic input in the autopilot whatsoever. Pure electrically-driven gyro that sensed rate of turn only (and had a separate channel for altitude hold). Any heading control that would be affected by a magnet had me in the loop (using various a ground-based navaid system , Loran, GPS, ATC vector, or the whiskey compass).Second airplane used a similar setup, but was attitude-based and air-driven gyro (Century IV). Any heading control still had me in the loop, or was driven off a generated deviation signal from the WAAS GPS (GPS Steering). Still no magnets.Third airplane does use a wing-mounted AHRS unit that uses a magnetometer for mid-term trimming/correction. Not nearly all APs can be upset (into a loss of control) by a magnetic anomaly.

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 26, 2018, 11:33:36 pm
content: Quoteyou know there are some lna who can power by 5V from usb? I gues the can use for transmitting to.I dont know if the are legimidated but what happen when the creq is hearing that Warning Sound over there Headset:When the ask over the Radio if someone else hear it the would say now becouse its that low power that just the creq heard it.How about an Microwave Ofen Ray Gun?Sure with an bad ass Powerbank behind.Is the Cockpit Door RF Proof?

author: janoc
author_rank: Super Contributor
timestamp: August 26, 2018, 11:47:30 pm
content: Quote from: Lord of nothing on August 26, 2018, 11:33:36 pmLNA is a low noise amplifier such as for a receiver, youcan'ttransmit through that. Or, well, you can - once.A power amplifier that would produce sufficient output power + antenna + power supply is going to be totally inconspicuous. Riiight ...And that is only if you wanted to simply blanket the signals with interference - that would be a nuisance at best. If you wanted to produce a valid TCAS signal, you would also need a GPS and a way to produce a valid transponder signal - and be able to negotiate with the onboard TCAS in order to be able to generate any advisories (it is a two way system - the planes coordinate with each other so that they don't end up turning in the same direction and crashing into each other at a different altitude - one gets the order to descend and the other to climb).Certainly possible technically but about as realistic threat as getting hit by a meteorite ...Quote from: Lord of nothing on August 26, 2018, 11:33:36 pmThose messages are genuine. But they are a mix of various unrelated systems - GPWS, TCAS, etc. Those are cockpit warnings, nothing to do with radio. So no, nobody else but the crew in the cockpit can hear these so they are certainly not going to ask whether anyone else heard them.And if you want to know what the crew procedures are when e.g. "TERRAIN TERRAIN" or "TRAFFIC TRAFFIC" sounds, all is well documented and available online.Quote from: Lord of nothing on August 26, 2018, 11:33:36 pmHere is a good explanation by an actual pilot about how TCAS works and what you would actually see and hear in the cockpit in case the system activates:I suggest everyone to watch it first before fantasizing about planes.