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I’ve been researching this: original idea is that the 5G signals are “de-sensing” the Instrument Landing Systems (ILS) on airplanes that receive the radar signa

by enkrs 5y ago

I’ve been researching this: original idea is that the 5G signals are “de-sensing” the Instrument Landing Systems (ILS) on airplanes that receive the radar signals from the airport. The 5G C-band is 3.7-3.98GHz; The global aeronautical band is 4.2-4.4GHz where supposedly the modern ILS reside.. Of course the planes could be fitted with better instruments with filtering that do not desense from a signal 200MHz(!) away. I did not find much info on 4GHz ILS so I’m not sure how widespread it is used in airports. Seems that the 110MHz/330MHz system is prelevant. (Which I don’t belive could be affected) What I’m more interested is the quote from the article: “… compromise not only the radio altimeter systems but the flight control systems on the fly by wire aircraft.” Does anyone have a guess what fly by wire systems could be affected by those 5G band signals?

_djo_ 5y ago
This isn’t the ILS signal, it’s the radar altimeter. Equally crucial.
37ef_ced3 5y ago
These same C-band 5G frequencies are used in France (and 39 other countries). There are no known interference issues. Everything works fine, every day, for thousands of flights.
- stevenhubertron 5y ago
  Except at half power directed away from the air. Quoteddirectly from the article: "We were not aware that the power of the antennas in the United States have been doubled compared to what's going on elsewhere. We were not aware that the antenna themselves have been put into a vertical position rather than a slight slanting position, which then taken together compromise not only the radio altimeter systems but the flight control systems on the fly by wire aircraft."
_moof 5y ago
There are three categories of ILS. The most basic one can get you down to 200' AGL and can be flown using only the signals from the localizer and glideslope antennas. These are the 110 and 330 MHz systems, respectively. They are transmitters sited at the airport, and there is receiving equipment in the aircraft. The aircraft uses a standard barometric altimeter. (Technically a "sensitive" altimeter but this distinction is pretty much irrelevant if you're flying anything made after 1930.) No radar altimetry or other special equipment is required; small single-engine planes flown by appropriately rated private pilots fly these all the time. These systems aren't affected by 5G. The other two categories get you down to 100' AGL and 0' AGL, and these are the ones at issue. These require additional equipment, training, operations manuals, and certification of air crew. They also use the localizer and glideslope, but they require a radar altimeter as well (plus a bunch of other additional equipment in the aircraft, mostly for redundancy, that isn't relevant to this discussion). The radar altimeter is C Band and has no ground components. The 0' AGL category is full autoland, with the autopilots controlling the aircraft not just all the way down to the ground, but throughout the landing rollout too. I suspect these are the "fly by wire" systems people are referring to, which is a bit of a misnomer if that's the case. "Fly by wire" is when the stick/yoke has no mechanical-hydraulic connection to the flight control surfaces; instead it provides signals to a set of flight computers, which mix those inputs with signals from the aircraft's sensors to produce an output for the actuators. It's possible that the radar altimeters are included in the inputs to the flight computers but I don't know. (I'd be surprised.) Autopilots, on the other hand, are more properly referred to as "automation." These would definitely be affected by problems with the radar altimeters during Cat II & III ILS approaches. Edit: Some Cat I (basic) ILS approaches are marked "SA" meaning "Special Authorization." These approaches do require radar altimetry, but they're the exception when it comes to Cat I.
Diesel555 5y ago
This is why I included my initial post on this topic. The 5G band affects the Radar Altimeter. The flight control systems rely on many inputs. If one of those inputs is the Radar Altimeter than the issue with RA could translate to an effect on the flight control system. This is well recognized and hence why the approaches (the way airplanes get close to runways in bad weather) that use this system are unavailable via NOTAMs.

by enkrs 5y ago

_djo_ 5y ago

This isn’t the ILS signal, it’s the radar altimeter. Equally crucial.

37ef_ced3 5y ago

These same C-band 5G frequencies are used in France (and 39 other countries). There are no known interference issues. Everything works fine, every day, for thousands of flights.

stevenhubertron 5y ago
Except at half power directed away from the air. Quoteddirectly from the article: "We were not aware that the power of the antennas in the United States have been doubled compared to what's going on elsewhere. We were not aware that the antenna themselves have been put into a vertical position rather than a slight slanting position, which then taken together compromise not only the radio altimeter systems but the flight control systems on the fly by wire aircraft."

_moof 5y ago

There are three categories of ILS. The most basic one can get you down to 200' AGL and can be flown using only the signals from the localizer and glideslope antennas. These are the 110 and 330 MHz systems, respectively. They are transmitters sited at the airport, and there is receiving equipment in the aircraft. The aircraft uses a standard barometric altimeter. (Technically a "sensitive" altimeter but this distinction is pretty much irrelevant if you're flying anything made after 1930.) No radar altimetry or other special equipment is required; small single-engine planes flown by appropriately rated private pilots fly these all the time. These systems aren't affected by 5G. The other two categories get you down to 100' AGL and 0' AGL, and these are the ones at issue. These require additional equipment, training, operations manuals, and certification of air crew. They also use the localizer and glideslope, but they require a radar altimeter as well (plus a bunch of other additional equipment in the aircraft, mostly for redundancy, that isn't relevant to this discussion). The radar altimeter is C Band and has no ground components. The 0' AGL category is full autoland, with the autopilots controlling the aircraft not just all the way down to the ground, but throughout the landing rollout too. I suspect these are the "fly by wire" systems people are referring to, which is a bit of a misnomer if that's the case. "Fly by wire" is when the stick/yoke has no mechanical-hydraulic connection to the flight control surfaces; instead it provides signals to a set of flight computers, which mix those inputs with signals from the aircraft's sensors to produce an output for the actuators. It's possible that the radar altimeters are included in the inputs to the flight computers but I don't know. (I'd be surprised.) Autopilots, on the other hand, are more properly referred to as "automation." These would definitely be affected by problems with the radar altimeters during Cat II & III ILS approaches. Edit: Some Cat I (basic) ILS approaches are marked "SA" meaning "Special Authorization." These approaches do require radar altimetry, but they're the exception when it comes to Cat I.

Diesel555 5y ago

This is why I included my initial post on this topic. The 5G band affects the Radar Altimeter. The flight control systems rely on many inputs. If one of those inputs is the Radar Altimeter than the issue with RA could translate to an effect on the flight control system. This is well recognized and hence why the approaches (the way airplanes get close to runways in bad weather) that use this system are unavailable via NOTAMs.