this post was submitted on 01 Oct 2023
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submitted 1 year ago by [email protected] to c/dankmemes
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[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

My edit was mainly based on a 2006 study, quote:

Yet our research has found that these items can interrupt the normal operation of key cockpit instruments, especially Global Positioning System (GPS) receivers, which are increasingly vital to safe landings. Two different studies by NASA further support the idea that passengers’ electronic devices dangerously produce interference in a way that reduces the safety margins for critical avionics systems.

The most common are the VHF omnidirectional range system and the instrument landing system, both of which operate near 100 MHz, and GPS, which operates between 1200 and 1600 MHz. PEDs have the potential to interfere with each of them, but the most serious concern has to be for GPS receivers, which are becoming key navigational aids these days—particularly when clouds or other weather problems make it impossible for pilots to see runways.

If I understand this correctly, there can be some interference, but it is likely not very significant. I assume that if enough devices are left with their GPS systems active, the pilots and auto pilot system could be fed data at a slower rate which is possibly less accurate. I don't interpret this as a direct cause for a aircraft to crash.

Also, again if I understand correctly, the FAA can do shit to allow people to have airplane mode disabled, due to the Prohibiting In-Flight Voice Communications on Mobile Wireless Devices Act or PIFVCoMWD Act for short. The act put responsibility to enforce this on the FCC, not FAA. It seems the FAA itself is pretty hands off, allowing the operator of the aircraft to allow any devices they deem to be safe.

Also also, the EU lifted its ban of PEDs not in airplane mode in 2014 (coincidentally the same year in which the act I mentioned above was passed and introduced), but in my experience airplane mode is still required on European airlines. Note that the EASA does require aircraft operators to "ensuring aircraft are not affected in any way by the transmission of signals from the PEDs" if they want to stop requiring airplane mode.

in other words ¯\(ツ)/¯

[–] Dettweiler42 2 points 1 year ago* (last edited 1 year ago) (1 children)

Regarding GPS interference, a GPS antenna is a receiver, not a transmitter. More GPS enabled devices around it will not affect performance, as they're all listening to the same frequencies. WAAS is also broadcast and received in a similar fashion and frequency, which is where you get down to Cat III levels of accuracy for Autoland.

As for bands, cell phones are sectioned to ~700-900 MHz and some small ranges above ~1700 MHz for VHF. VOR navigation operates between 108-118 MHz while GPS sits specifically at 1575.42 MHz (L1), 1227.6 MHz (L2) and 1176.45 MHz (L5) with WAAS and SBAS sticking close to those. From a VHF standpoint, a cell phone will not cause interference. I can also confirm this by goofing off with my phone while using an IFR4000 test set and watching the nav display indications in the flight deck.

Now, SHF is where things change a little bit. SHF is very directional and fairly short range. It will not make it inside or outside the metal tube of an aircraft very easily. Although the 5G cellular band is separated from the radio altimeter band, the Rockwell-Collins systems were receiving occasional interference from ground antennas during landing. Since the initial issue was discovered, they've patched the transceivers with better filtering (supposedly from just adding a LPF filter, which wasn't necessary before); and issued a service bulletin requiring the use of a newer model of antenna (which used to be optional. The 5 fleets I work on have all been updated or verified at this point.

[–] [email protected] 1 points 1 year ago (1 children)

Interesting!

The study I quoted stated that GPS is vulnerable to interference from PEDs as a fact, but it seems they only measured cell service frequencies. Since it seemed to be made by legitimate authors, I took its words.

From what I understand, neither the FAA (US) nor EASA (EU) require aircraft to be in no way affected by PEDs, though they do require a aircraft to be assessed as not affected to allow onboard WiFi or to allow devices with airplane mode turned off.

Thanks for your insight!

Also: out of curiosity: have any aircraft you've worked on been equipped with picocells?

[–] Dettweiler42 2 points 1 year ago* (last edited 1 year ago)

I have not encountered any picocells on aircraft yet. Plenty of airborne wifi service equipment and some wireless mQAR's for uploading aircraft monitoring data once the aircraft parks at the gate, though.

I do specialize in avionics, though. Hence, the more in-depth experience with navigation systems and radios.