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View Full Version : Fort Wayne incident


Excargodog
06-28-2018, 06:29 AM
Anyone know what REALLY happened?

https://www.usatoday.com/story/travel/nation-now/2018/06/28/delta-attendant-kicks-passengers-off-plane-over-airplane-mode-dispute/741161002/

This story seems to lack detail.


jtsastre
06-28-2018, 10:12 AM
I feel bad for FAís that have to enforce this regulation, because everyone knows no one turns their phone to airplane mode.

Iíve seen passengers talking on their phone as we were lining up on the runway and it just so happened the FAís didnít notice.

It wouldnít make operational sense to go 1 by 1 to ensure everyone oneís phone is in the appropriate mode.

GearUpHeadDown
06-28-2018, 10:48 AM
That and the fact having your phone on does absolutely nothing to affect the safety of flight.


Excargodog
06-28-2018, 10:53 AM
That and the fact having your phone on does absolutely nothing to affect the safety of flight.

So why IS the FAA pushing this? Don't they have to have some degree of evidence to promulgate these rules?

zondaracer
06-28-2018, 11:19 AM
It is an FCC thing.

minimwage4
06-28-2018, 11:58 AM
That and the fact having your phone on does absolutely nothing to affect the safety of flight.


It absolutely can if you're using an ILS in low visibility. It can throw the signal off. But really that's the only time it can affect the plane so not that often.

WesternSkies
06-28-2018, 12:00 PM
Ready for that fast upgrade?

amcnd
06-28-2018, 12:04 PM
Isnít there a Myth Busters episode on this..??..

TJBrass
06-28-2018, 12:12 PM
Probably, more a case of having 20 passengers, all trying to talk over each other, disturbing the other passengers and leaving the FAs to act like chaperones on a seventh grade field trip.

Excargodog
06-28-2018, 12:20 PM
It absolutely can if you're using an ILS in low visibility. It can throw the signal off. But really that's the only time it can affect the plane so not that often.

It only affects the ILS in low visibility? Why would an electronic device affect an ILS any more in low visibility than when it is CAVU?

Got an URL for that?

TheAshtar
06-28-2018, 12:33 PM
FAís are informers not inforcers.

I should know. Iím married to one

zondaracer
06-28-2018, 12:36 PM
The FAA allows use of devices if it doesnít affect or interfere with the aircraft equipment.

The FCC requires airplane mode because they donít want an Airbus with 230 cellphones and other devices trying to connect to a dozen towers simultaneously, especially at lower altitudes like climbout and approach.

OOfff
06-28-2018, 12:46 PM
Isnít there a Myth Busters episode on this..??..

There is, but their methodology falls a bit short of five 9 safety.

rickair7777
06-28-2018, 02:29 PM
That and the fact having your phone on does absolutely nothing to affect the safety of flight.

It absolutely can if you're using an ILS in low visibility. It can throw the signal off. But really that's the only time it can affect the plane so not that often.

They most certainly CAN affect flight safety, just because YOU haven't personally experienced a serious accident doesn't mean it couldn't happen. But it depends on the type of phone, where the pax is seated, what aircraft type, and what sort of operation is being conducted. Also the signal output strength of the phone varies with range from the tower (close to tower, lower output to save battery, further away, signal jacked up for QoS).

I flew one type where an old analog phone (rare these days) used in the back rows would set off the cargo smoke detector... SOP was blow the bottles and land immediately.... $$$.

The FAA simply cannot test and certify every possible permutation of phone, plane, and location.

Eventually service will be available over a common onboard connection point (such as wifi) which can be practically certified due to short range and low power output requirements. Probably best to keep voice disabled, just to avoid air rage.

rickair7777
06-28-2018, 02:33 PM
The FAA allows use of devices if it doesn’t affect or interfere with the aircraft equipment.

Under part 91.

121 is more restrictive, the PIC does not have the authority to make that call (pun intended).



The FCC requires airplane mode because they don’t want an Airbus with 230 cellphones and other devices trying to connect to a dozen towers simultaneously, especially at lower altitudes like climbout and approach.

This is also true. The problem is that the cell system can deconflict a phone which has line-of-sight to a few towers, maybe 3-4, but it's not designed to handle it if the phone has LOS on 20+ towers, which is entirely possible in a big metro area at 5K-10K.

blindfayth
06-28-2018, 04:12 PM
This is also true. The problem is that the cell system can deconflict a phone which has line-of-sight to a few towers, maybe 3-4, but it's not designed to handle it if the phone has LOS on 20+ towers, which is entirely possible in a big metro area at 5K-10K.


^ Correct. Also, since you're at a higher elevation and your phone has a LOS on every tower, it's going to try and maintain a connection to each and every tower it sees, draining the heck out of your battery. It's in your own best interest to disable cell mode for that reason alone.

Also, how exactly does a cell phone using a cellular signal which uses *micro*wave bands (800 MHZ and 1900 MHZ) in any way shape or form have the capability to interfere with an ILS signal which uses RADIO wave bands.

Those are two completely different parts of the electromagnetic spectrum. That's like saying I shouldn't listen to NPR on my FM radio near my lamp because the radio might affect how much light the light bulbs will emit.

Also, keep in mind, turning on airplane mode does *not* disable your gps receiver/location services. So your phone will still be communicating with GPS satellites even in airplane mode. What if the plane is doing an RNAV GPS approach? Is it going to crash? No, of course not. Separate signals to separate receivers for separate reasons. Does the FAA/FCC say anything about disabling one's GPS receiver in their phone?

Also, let's be real here. What if someone leaves their cell phone in their carry-on and forgot to put it in airplane mode? Or their pocket of their jacket? How would the FA's know? How many aircraft have been taken down by a rogue cell (read: Microwave) signal? None. How would FA's enforce that? Everyone take out their cell phones for visual inspection? Confiscation until the end of the flight?

I'm not faulting the FA for enforcing policy, but it *is* a pretty stupid policy.

PerfInit
06-28-2018, 04:33 PM
Also ADS-B in/out is on 1090 or 978 Mhz. Could a cell signal interfere
with that by chance?

Excargodog
06-28-2018, 04:39 PM
Isnít there a Myth Busters episode on this..??..

Actually, there is:

Cell Phones Interfere with Plane Instruments | MythBusters | Discovery (http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/cell-phones-interfere-plane-instruments/)

They considered it a myth, that the real reason was that the FCC (not FAA) didn't want high flying phones overloading multiple cell towers over a wide area.

RandomName
06-28-2018, 05:16 PM
*snip*
Also, keep in mind, turning on airplane mode does *not* disable your gps receiver/location services. So your phone will still be communicating with GPS satellites even in airplane mode. What if the plane is doing an RNAV GPS approach? Is it going to crash? No, of course not. Separate signals to separate receivers for separate reasons. Does the FAA/FCC say anything about disabling one's GPS receiver in their phone? *snip*


A GPS receiver in a phone does not communicate back to the satellites. GPS receivers are just that, receivers ONLY. Since there is no signal being broadcast "out" by the device there can be no interference that it causes (disregarding the likely negligible electromagnetic field the device generates during it's operation)



If you don't believe me, you are free to look up how exactly GPS works. In a nutshell, the GPS receiver uses it's own internal clock and compares this timestamp with the timestamp of the signal received.



If you know how long the signal took to reach you, you know how far away the transmitter is. By using at least 3 independent satellite signals you can triangulate your position, with more signals improving the accuracy.

BeechPilot33
06-28-2018, 06:30 PM
The reason Is not because it will interfere with the ILS. Itís because if you have a fire or emergency on the ground you want pax to be alert and paying attention not texting away on their phone while an Aircraft is moving.

DarkSideMoon
06-28-2018, 06:47 PM
They most certainly CAN affect flight safety, just because YOU haven't personally experienced a serious accident doesn't mean it couldn't happen. But it depends on the type of phone, where the pax is seated, what aircraft type, and what sort of operation is being conducted. Also the signal output strength of the phone varies with range from the tower (close to tower, lower output to save battery, further away, signal jacked up for QoS).

I flew one type where an old analog phone (rare these days) used in the back rows would set off the cargo smoke detector... SOP was blow the bottles and land immediately.... $$$.

The FAA simply cannot test and certify every possible permutation of phone, plane, and location.

Eventually service will be available over a common onboard connection point (such as wifi) which can be practically certified due to short range and low power output requirements. Probably best to keep voice disabled, just to avoid air rage. sitting in the back a lot, I'm convinced if cell phones actually put out a harmful amount of interference someone would've crashed by now. Large numbers of passengers are already on their phone under 5,000ft.

JamesNoBrakes
06-28-2018, 07:37 PM
ß121.306 Portable electronic devices.
(a) Except as provided in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any U.S.-registered civil aircraft operating under this part.

(b) Paragraph (a) of this section does not apply toó

(6) Any other portable electronic device that the part 119 certificate holder has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used.

The FAA doesn't require them to put it on airplane mode, they require the airline to test and verify that the interference doesn't cause any issues. If they are unwilling or don't have the resources to do the testing, they can simply have everyone turn it to airplane mode. So if they wanted to run tests, collect data, and present it to the FAA, I'm sure it would be approved.

bradthepilot
06-28-2018, 07:50 PM
Also, how exactly does a cell phone using a cellular signal which uses *micro*wave bands (800 MHZ and 1900 MHZ) in any way shape or form have the capability to interfere with an ILS signal which uses RADIO wave bands.

Those are two completely different parts of the electromagnetic spectrum. That's like saying I shouldn't listen to NPR on my FM radio near my lamp because the radio might affect how much light the light bulbs will emit.

It's absolutely possible to have interference across different parts of the spectrum, and the phenomena is well documented for all kinds of different things. One well known example in aviation is 12th and 13th order harmonics of VHF communications interferring with GPS L1 , especially frequencies of 121.150, 121.175, 121.2, 131.2, 131.25, and 131.3 MHz. More info on this specific example at link (http://www.navnin.nl/new/wp-content/uploads/2018/02/WSIA-1-NLR-Introduction-to-GNSS-Interference-and-Jamming-20180130.pdf) .

Not saying that cell phones will or will not cause issues, just pointing out that RF is not as cut and dried as it might first appear to be.

tomgoodman
06-28-2018, 07:57 PM
The real safety hazard in this case was annoying a Flight Attendant. :eek:

EMAW
06-28-2018, 08:02 PM
The reason Is not because it will interfere with the ILS. It’s because if you have a fire or emergency on the ground you want pax to be alert and paying attention not texting away on their phone while an Aircraft is moving.

Exactly. I don't want to have to knock you down and step on/over you in an evacuation, but I will.
In other news, certain phone models WILL and have caused interference in the communications radios. It's mostly just an annoyance but it could cause an accident.

hawk21
06-29-2018, 08:15 AM
I always thought it had to do with the potential for remotely detonated explosives in the cargo :confused:

ajaf1656
06-29-2018, 11:02 AM
There are a lot of rules that exist for reasons other than safety. You aren't supposed to use smokeless tobacco on a flight, so can I just chew some Redman if I feel like it? Granted I'm not a "black flier" or a "Latina" so I don't think my story will be as exciting when I get kicked off for demonstrating that I will refuse to comply with instructions from a crew member. You can't have passengers pick and choose which rules and instructions they will follow or not.

OOfff
06-29-2018, 12:57 PM
Granted I'm not a "black flier" or a "Latina" so I don't think my story will be as exciting when I get kicked off

https://media0.giphy.com/media/7WyERzq2P0jnO/giphy.gif

UAL T38 Phlyer
06-29-2018, 01:15 PM
It's absolutely possible to have interference across different parts of the spectrum, and the phenomena is well documented for all kinds of different things. One well known example in aviation is 12th and 13th order harmonics of VHF communications interferring with GPS L1 , especially frequencies of 121.150, 121.175, 121.2, 131.2, 131.25, and 131.3 MHz. More info on this specific example at link (http://www.navnin.nl/new/wp-content/uploads/2018/02/WSIA-1-NLR-Introduction-to-GNSS-Interference-and-Jamming-20180130.pdf) .

Not saying that cell phones will or will not cause issues, just pointing out that RF is not as cut and dried as it might first appear to be.

^^This. I’m guessing you are an EE. Nice explanation.

Radio tuning is not just “letting in one frequency.” It’s about making it easier for that one frequency (plus or minus a little), and difficult (but not impossible) for other frequencies.

As a kid, had an old record player that picked up the neighbor’s ham radio. Picked up a cell conversation on the interphone on the 727 once, and I saw where a cell phone would cause momentary pulses on the ILS in a Lear. In all cases, proximity was a key factor.

So yeah, it is unlikely, and even less likely to cause an incident...but it can happen.

501D22G
06-29-2018, 02:22 PM
A GPS receiver in a phone does not communicate back to the satellites. GPS receivers are just that, receivers ONLY. Since there is no signal being broadcast "out" by the device there can be no interference that it causes (disregarding the likely negligible electromagnetic field the device generates during it's operation)



If you don't believe me, you are free to look up how exactly GPS works. In a nutshell, the GPS receiver uses it's own internal clock and compares this timestamp with the timestamp of the signal received.



If you know how long the signal took to reach you, you know how far away the transmitter is. By using at least 3 independent satellite signals you can triangulate your position, with more signals improving the accuracy.

Sorry to nitpick, but if you are correcting him, it's trilateration, not triangulation.

rickair7777
06-29-2018, 04:34 PM
Also, how exactly does a cell phone using a cellular signal which uses *micro*wave bands (800 MHZ and 1900 MHZ) in any way shape or form have the capability to interfere with an ILS signal which uses RADIO wave bands.

Those are two completely different parts of the electromagnetic spectrum. That's like saying I shouldn't listen to NPR on my FM radio near my lamp because the radio might affect how much light the light bulbs will emit.

If you had an electrical engineering degree, you would not have asked this question. An antenna is optimized for the wavelength in question, and uses tuned resonance to capture the signal. But any component of any electronic or electrical system (or any conductor for that matter, including medical devices installed in the human body) can capture any EM signal if there's an impedance match. Basically everything is a potential radio, including sub-components of avionics, wires, power supplies, chassis, etc. All you need is EM energy, a conductor, and a coincidental impedance match and you can get the trons sloshing about in unpredictable ways... people with orthodontic braces have been known to hear radio stations via their jaw.

Military hardware is typically hardened against outside EM interference, because jamming will likely occur, and would be deliberately optimized for frequency, waveform, and high power level.

Civilian hardware is not typically hardened to that level (presumably FBW systems are reasonably well protected... I hope). They would be hardened to deal with EM interference in the expected operating environment, ie from emitters at some distance from the aircraft.

Cell phones have relatively weak power output... but recall that the power at the receiver is proportional to distance squared. A cell phone which was inches away from an antenna, wire, or electronic module would deliver a much higher signal strength than most remote transmitters, even though they may be far more powerful at the source.



Also, keep in mind, turning on airplane mode does *not* disable your gps receiver/location services. So your phone will still be communicating with GPS satellites even in airplane mode.

No. Your phone or other portable GPS does not in any way "communicate" with any satellite (unless you have an iridium satphone). Assuming that "communicate" implies two-way transfer of info. GPS is one-way in this context, your device only receives the signal from the satellite (and it's very weak, because satellites don't have large nuclear reactors to power their transmitters, and the distance from the source is many thousands of miles).


Also, let's be real here. What if someone leaves their cell phone in their carry-on and forgot to put it in airplane mode? Or their pocket of their jacket? How would the FA's know? How many aircraft have been taken down by a rogue cell (read: Microwave) signal? None. How would FA's enforce that? Everyone take out their cell phones for visual inspection? Confiscation until the end of the flight?


Whether or how FA's know or enforce the policy is a good question. It would be nice if that were clearly specified because it is hard for them to know for certain if someone is in violation. Even someone making a voice call could be using VOIP via wifi.

rickair7777
06-29-2018, 04:38 PM
sitting in the back a lot, I'm convinced if cell phones actually put out a harmful amount of interference someone would've crashed by now. Large numbers of passengers are already on their phone under 5,000ft.

I don't think a cell could likely directly cause a crash, although it would be hypothetically possibly in the case of interference with a fly-by-wire control system which was not shielded and caused a control deflection in close proximity to the ground (rotation/flare).

It is much more likely to cause an anomaly which could be a distraction at exactly the wrong moment, one link in the chain. I've experienced the anomalies in RJ's. Fortunately never in fly-by-wire mainline aircraft, that would actually cause me some concern.

RemoveB4Flight
06-29-2018, 09:28 PM
The reason Is not because it will interfere with the ILS. Itís because if you have a fire or emergency on the ground you want pax to be alert and paying attention not texting away on their phone while an Aircraft is moving.

This is incorrect. If this were the reason, why is cell phone usage allowed immediately upon landing while taxiing to the gate? Fires and emergencies are just as likely at that time as well.
Also, just because they arenít in airplane mode doesnít mean they are paying attention. Watching a movie offline, listening to music, etc. are just as distracting and perfectly legal for taxi and all phases of flight.

ajaf1656
06-30-2018, 01:58 AM
https://media0.giphy.com/media/7WyERzq2P0jnO/giphy.gif

Britney, you realize that is quoted from the article don't you?

OOfff
06-30-2018, 04:34 AM
Britney, you realize that is quoted from the article don't you?
No, your comment was not

NormalAbnormal
06-30-2018, 06:19 AM
^^This. Iím guessing you are an EE. Nice explanation.

Radio tuning is not just ďletting in one frequency.Ē Itís about making it easier for that one frequency (plus or minus a little), and difficult (but not impossible) for other frequencies.

As a kid, had an old record player that picked up the neighborís ham radio. Picked up a cell conversation on the interphone on the 727 once, and I saw where a cell phone would cause momentary pulses on the ILS in a Lear. In all cases, proximity was a key factor.

So yeah, it is unlikely, and even less likely to cause an incident...but it can happen.

^^^^^^^^^^^^^
This as well.

Just like how carrying Dangerous Goods probably won't cause a problem at any given time, the risk of the holes in the swiss cheese lining up is too great to allow.

I'm pretty sure the FCC license for cellular is a ground based license ONLY. It is not licensed for airborne use. In addition to the cell tower confusion, and the power variability (a cell phone only uses as much power as is needed to talk to a cell tower), you have the problem of edge and corner cases. If all components everywhere are perfectly within spec., the risk is probably low. However, if components start to drift toward the boundaries of the spec., the holes in the swiss cheese may start to line up. Real life devices are NEVER perfectly in spec.

I haven't personally seen the effects of cell phones on flight instruments. But, I have heard the interference on radios and intercoms; which can be just as distracting and risky.

This is a case where Mythbusters did a great disservice.

Wang Wei
06-30-2018, 06:27 AM
^ Correct. Also, since you're at a higher elevation and your phone has a LOS on every tower, it's going to try and maintain a connection to each and every tower it sees, draining the heck out of your battery. It's in your own best interest to disable cell mode for that reason alone.

Also, how exactly does a cell phone using a cellular signal which uses *micro*wave bands (800 MHZ and 1900 MHZ) in any way shape or form have the capability to interfere with an ILS signal which uses RADIO wave bands.

Those are two completely different parts of the electromagnetic spectrum. That's like saying I shouldn't listen to NPR on my FM radio near my lamp because the radio might affect how much light the light bulbs will emit.



I'm not faulting the FA for enforcing policy, but it *is* a pretty stupid policy.

Radiofrequency interference is infinitely more complex then what you describe. For example, while the carrier frequency of GSM800/900 is in the range of 800-960 MHz, the signal is fundamentally modulated at 18Hz. Moreover, the mode of entry in of the interfering signal is not necessarily through the receive path. Conceptually, your cell phone's carrier frequency could be induced though some path into the guts of the aircraft's ILS receiver. Within the electronics, there are typically devices that have a tendency to behave like AM detectors (demodulation). Thus, an 18 Hz noise signal is induced, which, by the way, will also have harmonic content at 96 Hz (18 Hz x 3).

It so happens that the 2 ILS modulation frequencies, 90 and 150 Hz, are close to the harmonics of a pulsing 18 Hz signal (90 vs 96). THIS is how a cell phone could jack up an ILS..........

NormalAbnormal
06-30-2018, 06:29 AM
I don't think a cell could likely directly cause a crash, although it would be hypothetically possibly in the case of interference with a fly-by-wire control system which was not shielded and caused a control deflection in close proximity to the ground (rotation/flare).

It is much more likely to cause an anomaly which could be a distraction at exactly the wrong moment, one link in the chain. I've experienced the anomalies in RJ's. Fortunately never in fly-by-wire mainline aircraft, that would actually cause me some concern.

Don't think a non-FBW is immune to something like this. I was on a plane in IMC that started diving (ILS coupled approach) at less than 1000' feet to stay on the glideslope because a heavy aircraft taxied in front of the glideslope antenna. Luckily we recognized what was happening and disconnected the autopilot. I let ATC know and they weren't sympathetic because protecting the critical area wasn't required.

NormalAbnormal
06-30-2018, 06:41 AM
A GPS receiver in a phone does not communicate back to the satellites. GPS receivers are just that, receivers ONLY. Since there is no signal being broadcast "out" by the device there can be no interference that it causes (disregarding the likely negligible electromagnetic field the device generates during it's operation)



If you don't believe me, you are free to look up how exactly GPS works. In a nutshell, the GPS receiver uses it's own internal clock and compares this timestamp with the timestamp of the signal received.



If you know how long the signal took to reach you, you know how far away the transmitter is. By using at least 3 independent satellite signals you can triangulate your position, with more signals improving the accuracy.

It's been a while since I saw a technical presentation on GPS; but I think a synchronized atomic clock is required in the receiver in order to use only 3 satellites (absolute time measurement as you describe above). However, atomic clocks don't lend themselves to portability. If you use a good relative clock, to do differential time measurements, then you need 4 satellites (4 degrees of freedom) and you don't need to know how long the signal took to reach you. You can infer it by looking at the relative delays between the 4 satellite signals. This is how the vast majority of GPS receivers work. I'm pretty sure the ground based calibration sites do have their own synchronized atomic clock.

rickair7777
06-30-2018, 07:06 AM
Don't think a non-FBW is immune to something like this. I was on a plane in IMC that started diving (ILS coupled approach) at less than 1000' feet to stay on the glideslope because a heavy aircraft taxied in front of the glideslope antenna. Luckily we recognized what was happening and disconnected the autopilot. I let ATC know and they weren't sympathetic because protecting the critical area wasn't required.

Non FBW is not immune to interference, just that the interference would affect other systems such as what you described. But at least you can grab the controls and right the ship. A hypothetical EM interference which caused a FBW aircraft control to go hard-over might not be recoverable.

RandomName
06-30-2018, 08:06 AM
Sorry to nitpick, but if you are correcting him, it's trilateration, not triangulation.


I had no idea that was even a word before your post. I appreciate the nitpick as I've now learned something new.

Excargodog
06-30-2018, 08:17 AM
Non FBW is not immune to interference, just that the interference would affect other systems such as what you described. But at least you can grab the controls and right the ship. A hypothetical EM interference which caused a FBW aircraft control to go hard-over might not be recoverable.

I suppose anything is possible, but I have a rather vivid memory of flying in the back seat of a FBW fighter and watching ball lightning dance along the canopy. OK, perhaps mil-spec stuff is better EMP protected than civilian aircraft, but after watching that it sort of begged credibility that a cellphone signal could cause problems. Someone hacking the onboard computer in an Airbus on the other hand....

N1234
06-30-2018, 08:21 AM
It's been a while since I saw a technical presentation on GPS; but I think a synchronized atomic clock is required in the receiver in order to use only 3 satellites (absolute time measurement as you describe above). However, atomic clocks don't lend themselves to portability. If you use a good relative clock, to do differential time measurements, then you need 4 satellites (4 degrees of freedom) and you don't need to know how long the signal took to reach you. You can infer it by looking at the relative delays between the 4 satellite signals. This is how the vast majority of GPS receivers work. I'm pretty sure the ground based calibration sites do have their own synchronized atomic clock.

This is correct. Most aviation receivers require line of sight to 5 satellites. 3 for position incl alt. 1 for time reference and 1 for RAIM.

NeverHome
06-30-2018, 09:22 AM
To everyone who mentioned harmonics and all the fun little R.F. facts: you warmed my heart! I love that stuff.

Also when I flew the dash, we had a problem with false smoke warnings. Turns out it was cell phones. So ya, interference. By cellular devices.

Did we crash, no. Did we divert and cancel flights, yup. All because some prick couldnít follow the rules. But hey, pax know better than any of us

rickair7777
06-30-2018, 02:23 PM
I suppose anything is possible, but I have a rather vivid memory of flying in the back seat of a FBW fighter and watching ball lightning dance along the canopy. OK, perhaps mil-spec stuff is better EMP protected than civilian aircraft, but after watching that it sort of begged credibility that a cellphone signal could cause problems. Someone hacking the onboard computer in an Airbus on the other hand....

All aircraft are protected against lightning, but that's mainly surge protection.

EM interference from man-made sources is going to be about frequency and waveform, and potentially digital packet interference. Near infinite potential variations, like the old analogy about a 10,000 monkeys with typewriters.

JamesNoBrakes
06-30-2018, 08:49 PM
This is correct. Most aviation receivers require line of sight to 5 satellites. 3 for position incl alt. 1 for time reference and 1 for RAIM.

Not my understanding. My understanding is that it's a differential math equation with 4 equations and 4 unknowns, solving for 1 time that satisfies all equations. Sats traveling thousands of miles/hr are essentially "dumb", sending out their atomic time. Receiver gets atomic time from 4 different sats, but all the times are different due to the difference in distance. Receiver must solve for distances and time in those 4 equations, pseudo-ranging. This is 3d position. Receiver knows what time it is where it is located with no delay/distance error because it's constantly solving this equation.

N1234
06-30-2018, 09:16 PM
Not my understanding. My understanding is that it's a differential math equation with 4 equations and 4 unknowns, solving for 1 time that satisfies all equations. Sats traveling thousands of miles/hr are essentially "dumb", sending out their atomic time. Receiver gets atomic time from 4 different sats, but all the times are different due to the difference in distance. Receiver must solve for distances and time in those 4 equations, pseudo-ranging. This is 3d position. Receiver knows what time it is where it is located with no delay/distance error because it's constantly solving this equation.

The result is the same. You are solving a 3D problem using a 4th data point to compensate for time uncertainty at the receiver end.

The satellite transmits its own position and accurate time (atomic clock).

The receiver itself compares the signal delay from the satellites and interprets it as distance from the reported satellite position.

But it essentially compensates for time inaccuracy.

In the old days submarines could get away with just two satellites by (1) having an atomic clock onboard and (2) making the simplifying assumption to be on the surface.

JamesNoBrakes
06-30-2018, 09:23 PM
The satellite transmits its own position and accurate time (atomic clock).


That's where I think the issue is, they are traveling somewhere like 10k mph, right? They are not transmitting their "GPS" position, they are transmitting time, it's all about the time. The receiver doesn't know the satellite position. If it did, it could easily calculate it's own position without time.

jtsastre
06-30-2018, 11:32 PM
That's where I think the issue is, they are traveling somewhere like 10k mph, right? They are not transmitting their "GPS" position, they are transmitting time, it's all about the time. The receiver doesn't know the satellite position. If it did, it could easily calculate it's own position without time.

Youíre on the right track. But the receiver still needs distance to calculate the sphere itís located in from the satellite. Once it receives the distance from three of the satellites and therefore their spheres and times, it can calculate position.

https://lh3.googleusercontent.com/uTTLT4Is7VRwP-PO7N94XwND_gfq8y4PBbojZd7JLMZl0DBWciC2yM8_Y0RHNh3e gyA9aDao40RBmpPWD4JmmpFlXD2ircLjaCt4rfaiIigzo3HSSi mvkHH5Z7D6wV6C055vZNlxNUs=w2400

jtsastre
06-30-2018, 11:32 PM
That's where I think the issue is, they are traveling somewhere like 10k mph, right? They are not transmitting their "GPS" position, they are transmitting time, it's all about the time. The receiver doesn't know the satellite position. If it did, it could easily calculate it's own position without time.

Whatís crazy is this ďcesium/caesiumĒ element used in atomic clocks. Itís so reactive that its accuracy is within 1 part in 10^15, about 1 second in 20 million years.

N1234
07-01-2018, 05:01 AM
That's where I think the issue is, they are traveling somewhere like 10k mph, right? They are not transmitting their "GPS" position, they are transmitting time, it's all about the time. The receiver doesn't know the satellite position. If it did, it could easily calculate it's own position without time.

You need both.

Time (or time difference) gives you the distance. But you still need to know a distance from a fixed spot in space. So you need a starting location.

Satellites are on a predefined orbit and they send their orbital (location data). Ground stations monitor the data sends by satellites and correct the satellites for errors (this is not WAAS). This is just to maintain saaellite orbital data accuracy.

You can also check it out here.

https://timeandnavigation.si.edu/multimedia-asset/how-does-gps-work

rickair7777
07-01-2018, 07:54 AM
In the old days submarines could get away with just two satellites by (1) having an atomic clock onboard and (2) making the simplifying assumption to be on the surface.

Yes. Accurate time and one plane was known by the receiver. Even then, they didn't need quite the same accuracy that an RNP approach would require. Open ocean navigation tolerance was relatively loose. The most accuracy would be required for missile boats... the missiles had to know their starting point at launch, but even then you know what they say about horseshoes and hydrogen bombs...

rickair7777
07-01-2018, 08:13 AM
Not my understanding. My understanding is that it's a differential math equation with 4 equations and 4 unknowns, solving for 1 time that satisfies all equations. Sats traveling thousands of miles/hr are essentially "dumb", sending out their atomic time. Receiver gets atomic time from 4 different sats, but all the times are different due to the difference in distance. Receiver must solve for distances and time in those 4 equations, pseudo-ranging. This is 3d position. Receiver knows what time it is where it is located with no delay/distance error because it's constantly solving this equation.

Yes. Solving for actual time based on the time signals from multiple satellites allows the receiver to get away with NOT having a large expensive atomic clock installed (an atomic clock could be practical on airliners, but not cessnas or cell phones, or the infantry guy that GPS was also designed to accommodate).

Each satellite transmits a virtual sphere, your location could be anywhere on that sphere (based on time/distance, essentially like DME). The intersection of three spheres is your location. The intersection on or near earth of course, not the other one halfway to the moon, the receivers disregard any solutions in deep space.

The fourth satellite actually allows for time to be solved. The fifth is required for RAIM, so if one satellite is out of whack the system will detect that by constantly comparing the solutions of various combinations of four of the five birds (all solutions should be the same within certain tolerances).

Baro-aiding can reduce the required satellites to four. Knowing your altitude above the earth creates another virtual sphere, which can be combined with two satellites for position, a third for time solution, and a fourth for RAIM.

rickair7777
07-01-2018, 08:28 AM
You need both.

Time (or time difference) gives you the distance. But you still need to know a distance from a fixed spot in space. So you need a starting location.

Satellites are on a predefined orbit and they send their orbital (location data). Ground stations monitor the data sends by satellites and correct the satellites for errors (this is not WAAS). This is just to maintain saaellite orbital data accuracy.

You can also check it out here.

https://timeandnavigation.si.edu/multimedia-asset/how-does-gps-work

Garden-variety GPS receivers don't get any info from the satellite as to the satellites' own location. The orbits are known, and don't change much.

The receiver would need only very rough knowledge of the satellite's location so as to avoid wasting processing power calculating the OTHER possible solution... in deep space.

The rough locations are stored in databases, and don't change much or often. In fact, the DoD will generally try to return a wayward satellite to it's published orbit rather than just update the database (which would take time to propagate to all users).

Ground control stations continually monitor and satellite positions and function obviously.

NeverHome
07-01-2018, 08:46 AM
Fun thoughts,

Some of you say time, some say distance. Then there is the old algebra of distance=rate*time (d=rt).

Leading to the fun fact that those satalights up there are moving very fast to stay in orbit. Much faster than we are used to dealing with (even in our airplanes). So realativity must be accounted for. The frequency of the signal is slightly (very slight) shifted.

domino
07-01-2018, 11:02 AM
Funny reading this thread. Human race is truly screwed.

todd1200
07-01-2018, 11:32 AM
In terms of enforcing compliance, what about WiFi calling? My phone rings all the time in airplane mode when Iím in the cabin and connected to onboard WiFi. I donít answer and talk in flight, I just silence the ringer, but couldnít people follow the rules and still have phones ringing, etc.? Is there a reg about talking on the phone through WiFi?

Slaphappy
07-01-2018, 12:04 PM
Anyone know what REALLY happened?

https://www.usatoday.com/story/travel/nation-now/2018/06/28/delta-attendant-kicks-passengers-off-plane-over-airplane-mode-dispute/741161002/

This story seems to lack detail.

Sounds like another entitled person who thinks the rules don't apply to her.

SpeedyVagabond
07-01-2018, 12:33 PM
How did a thread that could have been a lot of fun turn into a porchlight for nerds?

DarkSideMoon
07-01-2018, 01:52 PM
How did a thread that could have been a lot of fun turn into a porchlight for nerds?

Have you ever talked to 80% of pilots?

rickair7777
07-01-2018, 07:18 PM
Fun thoughts,

Some of you say time, some say distance. Then there is the old algebra of distance=rate*time (d=rt).

Leading to the fun fact that those satalights up there are moving very fast to stay in orbit. Much faster than we are used to dealing with (even in our airplanes). So realativity must be accounted for. The frequency of the signal is slightly (very slight) shifted.

Also... the satellites experience relativistic shift due to being further up the gravity well than those of us on the surface. The sum of those effects produces a net increase in the clock speed on the satellites (compared to surface receivers). If it was not accounted for (it's predictable) it would introduce large errors into the system rather quickly.

n9810f
07-02-2018, 06:26 PM
OO crews have well earned to corner on airplane mode enforcement. No other airline I sit on as a passenger labors over airplane mode than OO. It goes without saying the headline immediately was a dead give away. That said, I find OO to be far above any other regional. It must be their training department.

ajaf1656
07-02-2018, 07:08 PM
No, your comment was not

I was referring to the part I put in QUOTATION MARKS. ...Smarty McSmarty over here.

Fr8Thrust
07-05-2018, 03:05 PM
OO crews have well earned to corner on airplane mode enforcement. No other airline I sit on as a passenger labors over airplane mode than OO. It goes without saying the headline immediately was a dead give away. That said, I find OO to be far above any other regional. It must be their training department.

That and leaving the cabin lights ON during the whole flight. 😣