Andrasz

1G analogue mobile phones were a major problem. At that time I was involved in flight inspection (testing Navaids, including the ILS). I calibrated our kit every month, on the test bench. Looking at the Glideslope indicator I could get it to go full scale up or down as I walked up and down the workshop, about maximum distance of 20m, with my mobile in my pocket Our kit was installed and earthed to at least the same standards found in aircraft, and arguably to a far higher earthing standard. The cellphone was not making a call, it was communicating with the base station on an “overhead” channel or 2. I have no experience with 2, 3, 4 or 5g.

What we're being told

5G NETWORK – AVIONICS INTERFERENCE ISSUES
What:

5G high-speed telecommunication networks are being slowly rolled out across the world. It’s a fast, high-density information streaming medium that operates in the 3.4-4.0 MHz frequency range. It is short range and is susceptible to attenuation by buildings and trees, which necessitates a vast network of antennae. The associated infrastructure is both resource intensive and very expensive, so 5G implementation is going to be slow.

So What:

Most Radio Altimeters (RADALT) work in the 4.2-4.4 MHz band. The Radio Technical Committee for Aeronautics has conducted an assessment of 5G in the frequency band 3.7-3.98 MHz (Oct 2020) and found the potential for harmful interference to aviation RADALT systems. The RADALT is a mandated critical aircraft safety system used to determine an aircraft’s height above terrain or water (e.g. maritime environments). RADALT equipment can be directly integrated into several aircraft systems and functions for various flight profiles. These can include: Terrain awareness, aircraft collision avoidance, wind shear detection, flight controls, auto-land, auto-hover and transition up/down systems in rotary aircraft. Interference could lead to malfunctions in aircraft systems and a potential loss of situational awareness during critical phases of flight. Both 5G enabled portable electronic devices and ground-based antennae have the ability to compromise RADALT equipment.

Mitigations:

Worldwide testing and evaluation has been limited thus far; various nations are looking into potential 5G flight safety issues; Canada, Japan, and the USA are introducing guard bands of between 0.2 and 0.7 MHz either side of the 4.2-4.4 MHz RADALT frequency band. Canada is introducing both exclusion and protected zones around major airports and heliports that have auto-land systems (CAT I, II and III). Ground-based antennae will be tilted downwards and transmission power levels reduced. Uncrewed airborne operations (e.g. drones/RPAS) will not be permitted in the 3.45-3.65 MHz band. Individual aircraft types will require testing and certification with regard to exposure to 5G signals; this will be a time consuming and expensive process. Transport Canada will be producing maps showing 5G zones, allowing crews to plan to avoid them in the low level environment. ICAO is liaising with aircraft manufacturers to decide the best way ahead to mitigate this issue. In the interim, operators are reminded to remain vigilant regarding their aircraft behavioral characteristics and report any undesirable or objectionable aircraft behaviors observed during manual or automated RADALT systems operations.

Useful websites:

Map of Exclusion Zones and Protection Zones (SRSP-520) - Spectrum management and telecommunications
Blanclirio Yoo Toob channel put out an interesting video yesterday. Basically the FAA rescinded the 5G NOTAM as the rollout of the system has been delayed by two weeks. It would have severely restricted operations at 80 or so airports in CONUS by not allowing the use of CAT I/II/III and RNP approaches in poor weather.

In layman's terms - I read the problem with 5g (specifically in the United States) is the power they use, somewhere typically in the region of 2.5 times that of other countries 5g networks. They also point the antennas up whereas other countries point them down and that means powerful signals going right into the rad alt of aircraft. This might be why USA has seemingly bigger issues with interference than other countries. Not sure why its affecting Boeing more than Airbus but at least it doesn't give you covid. I think....

Why has EK cancelled 777s but are still flying 380s to the US?

Also, the interference potential from 5G in C band is greater in the US because the 5G allocated band goes up to 3.98 GHz, whereas in other places including Europe it stops at 3.8 GHz or even 3.7GHz

Good article thank you

Not a 777 pilot, but why would the engines and flight controls be affected? Aren't those usually governed by air/ground logic? With the exception of tailstrike prevention, the rest seem like pretty minor things. Certainly no reason to cancel a flight.

Flight Controls and EGPWS are minor things???!!!???. I beg to differ.

first the 380 and 350 are using 3 Rad Alt instead of 2 and therefore is less volatile to miss readings.

A380 is by design newer technology and there the Filter design will allow frequencies which are closer to ops frequencies of the rad alt.
there is also a design difference in the installation since at time of development of the B777 frequency of 1GHZ or more where not considered for mobile telecom and therefore electronic equipment has not been designed and tested to withstand such frequency ranges and output power level.
at design time of the A380 there had been definitiv more considerations towards these potential sources of errors.

3rd output power of Telecom Equipment:
the higher the carrier frequency the more output power you need for the same coverage area (alternatively more transmitters with less power - here does $$$ set the tone)
for higher data speeds you need higher carrier frequencies (that’s why everything up to 6ghz is of such a big intresst for telecom, as it allows to massively increase data throuput, by compared minimal increasing Transmitter density

as 5G is strongly depending on the distance between Transmitter and receiver (mobile phone) and the fact that the receiver won’t be able to significantly increase its output power, doubling the transmitter power is a cheap trick to pretend being full 5G, therefore the assumption is for $$$ driving another Industrie into trouble with no proper assest

as a further point should be mentioned: the modulation technology behind 5G
it is phase shift based and so is a radar distance measuring too, in the Same frequency Spektrum these 2 things can interfere

See discussion of Rad Alt interaction with the air/ground logic in the main 5G thread in R&N.

on an airbus in general RA are always a point to observe even on CAT I
without RA the airplane goes to direct law at gear down and their is a checklist for double RA u/s
but that’s on system fail - resulting if both RA running falls measurement constantly a lot of systems will do the right thing at the wrong time

Partial quote from Hueymeister -:
Both 5G enabled portable electronic devices and ground-based antennae have the ability to compromise RADALT equipment.“
So enhanced vigilance and enforcement from cabin crew will also be required ?

The issues with 5G in the US are related to both frequency and signal strenght. Airbus aircraft are protected against RA interference, so not affected by the 5G roll out in the US.
In Euroland this is not a problem. The rest of the world? Not sure.

well only the 380 and the 350 enjoy a better protection as these variant use 3 RA - 320/330/340 (only 2 RA) not so and are volitile to issue as well

Interesting, in the mid-nineties we did quite extensive testing for a period of about 3 months under CAA supervision with three pilots up front, making monitored Cat III approaches in VFR with 1G phones in various use configurations in the cockpit, no ILS issues were noted on any of the approaches. On the F70 we did have a couple of FMC resets which we suspected but could not conclusively link to phone interference, but that was all.

That is sure not true on the A330’s flown by my company. Lots of 5G issues including putting the aircraft into the wrong flight law and loss of trim to the stabilizer among other issues.

How do 3 RAs provided better protection than 2 RAs? I'm assuming all 3 RAs have the same receiver selectivity meaning any out-of-band interference would affect all RAs equally.

first this is a information from airbus safety bulletin where the protection against falls read outs is described.
on the other hand close frequency interference has a lot to do with how the signal arrives at the receiver.
A electromagnetic wave has high and lows. So while the aircraft is traveling along and so does the el mag wave it’s not for granted that all 3 RA receiver get the same disturbance.
as an excample: have you ever experienced that the radio in your car starts cracking while stoping at a red light? So you move your car just a few inches forward and the signal get suddenly better. With a second and third antenna at Slight shifted distance would solve the issue without moving. Same effect takes place here.
While with two RA only one needs to be wrong to tell the system something is wrong, it has possibly 2 correct read outs on a 380
in this case you have to consider that the system is fully functioning and therefore it compares the read outs, and fail over switching logic does not take place. At 2 RA the system cannot say which one is correct, with 3 it can.
it is not 100% protection, still 2 of the 3 can be in the same wrong but it is less likely that all 3 will receive the same disturbance at the same time as the distance is measured 100 times a second
there is also a difference of a disturbance in the same frequency band or from one which is close by. A close by band radiates side frequencies which cannot be eliminated a 100% but to a fair lower level.
they properly not effecting anything if a weaker transmitter output (like in Europe) is applied, but ramping up that output power to 2,5 of its original value does make the side radiation stronger too, which suddenly starts making problems. There are a lot of other factors as what are the signal by products of the modulation and filter characteristic and etc.

antennas and high frequency transmitters are a highly complex technology, it’s very very difficult to predict what will happen once you change one parameter, without testing and measuring.

andrasz
Even more interesting, this was in the mid 1990’s but before Dec 1999. As part of the monthly calibration check of our navigation kit (typical aircraft commercial kit, albeit one receiver was modified for flight inspection use by the manufacturer) after calibration and everything back together with all covers on, I could reliably get my cellphone (cant remember brand/model) to move the glideslope full scale in both directions by walking up and down the workshop. The Nav kit was all on the bench, driven by appropriate sig generators (no aerials in circuit), all very well earthed. Never tried it airborne. If I remember correctly, there was an area of little or no interference within about 1-2m of the kit. However, as soon as I moved further away down the workshop the glideslope (and only the glideslops) would give false readings. The phone was not making/receiving a call, but was communication on data channels with the cellphone base station. I remember I switched my phone off, problem disappeared, hence the source was my phone, and not the cell base station. Glideslope is 330-335MHz and G1 cellphones 890-960MHz, hence 3rd harmonic interference was a likely source. Aircraft kit is built to a spec, but cellphone was built to a price, maybe the transmitter was out of spec? BTW, the workshop was at Biggin Hill, UK.