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Worried about 5G?

Thermal said:
This was kind of my impression, although it must be a significant improvement to warrant all those snazzy new towers, and being a rival for conventional ISPs.
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Fixed 5G cellular datalinks (we have one) can hit >1Gb/s.

Also 5G uses different (higher) frequencies to previous systems, >30GHz rather than <6GHz, which allows more efficient spectrum usage.
Better bandwidth and (potentially) lower energy levels and improved battery life for portables.

Finally 5G base stations are different. As an effect of the higher frequencies, allowing them to provide far greater bandwidth, they also allow for greater directionality in signals, and that antennae can be much smaller than for previous generations of cellular base stations. With more, more directional, antennae per base station car more client devices can be supported.
There are also two other less noticeable changes; smarter bandwidth utilisation and software defined base units. The former means 5G nets are better able to make use of the available RF and prioritise traffic for efficiency. The later means fewer hardware deployments and changes in the future, useful given the number of units.
However high frequencies means shorter range, hence more base stations, but also more redundancy in the mesh. Some of the frequencies used are susceptible to water scattering and absorption.
 
FAA Statement on 5G

Tuesday, December 7, 2021

The FAA believes the expansion of 5G and aviation will safely co-exist. Today, we took an important step toward that goal by issuing two airworthiness directives to provide a framework and to gather more information to avoid potential effects on aviation safety equipment. The FAA is working closely with the Federal Communications Commission and wireless companies, and has made progress toward safely implementing the 5G expansion. We are confident with ongoing collaboration we will reach this shared goal.


https://www.faa.gov/newsroom/faa-statement-5g


No worries
 
LongFuzzy said:
Radio altimeter/radar altimeter — Airborne electronic devices capable of measuring the height of the aircraft above the terrain immediately below the aircraft. They operate in the 4.2–4.4 GHz band. Use of the radio altimeter is integral to terrain awareness and warning systems and to the landing of aircraft during CAT 2/CAT 3 approaches, for example.

A move by the U.S. Federal Communications Commission (FCC) to allow 5G telecommunications systems to use the 3.7–3.98 GHz frequency spectrum presents a “major risk … of harmful interference” with radar altimeters on civil aircraft, according to new research by RTCA.

https://skybrary.aero/articles/radio-altimeter-interference

The concern is that there could be interference between the 3.7-3.98GHz band and 4.2-4.4GHz band. I think the FCC position is that there is enough 'space' between these bands. The airlines and manufacturers position is that there is not.

If I understand how the systems work, the aircraft could stop receiving altimeter information. (I don't think they would get incorrect info, like showing the plane at 100' while it is actually at 50' or something like that. But I am not an expert in this, and I don't know exactly what would happen. In normal landings it shouldn't be much of an issue, but in foggy (low visibility) landings, it could be an issue.)

Any of you that are more knowledgeable please correct any info I may have incorrect.
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Essentially correct.

A non-functioning radar altimeter is the most likely problem, but the possibility of incorrect information cannot be ruled out depending on the type of radar altimeter. (I have put a description of the two types in the spoiler.

The second type (FMCW) is used for low altitude measurement, and of the two types, it is the one that is most susceptible to interference causing false altitude readings. When you are watching one of those Air Crash Investigation documentaries, and the recreation has one of those audible warnings...."Terrain, Terrain, Pull Up!" it is the data from an FMCW radar altimeter that is being used by the flight computer to generate these warnings.

Now the likelihood of this happening is small, but anyone who follows flight safety (and I do, very closely) will know the "Swiss Cheese theory" - that each hole in a slice of Swiss Cheese is a potential failure point and if you keep lining up different slices they will eventually line up in such a way that there is a straight path right through all of the slices, and you have got yourself an accident.

If we have learned anything about air safety from Boeing's MCAS debacle, its that it is sheer stupidity to make unnecessary extra holes in your Swiss Cheese.



Essentially there are two types of radar altimeters, Pulse Modulated and Frequency Modulated Continuous Wave (FMCW)

Pulse Modulated
This is the simplest type. The basic theory is that a very short pulse is transmitted at the ground, and the time taken for the leading edge of the pulse to return and be detected is calculated to give the distance from the ground to the aircraft. In reality it is somewhat more complicated than this, but that is the basic idea. The drawback with this type is that there is a lower height limit below which the altimeter will no longer function. If a radar altimeter is using, for example, 1 µS (one microsecond) pulses, the pulse length is about 300 metres, or 1000 feet, so at anything below 500 feet, and the altimeter will stop working because the the leading edge of the pulse arrives back at the receiver before the pulse finishes being transmitted, so the receiver cannot detect it. This limitation led to the development of the second type.

Frequency Modulated Continuous Wave
In this type, the radar altimeter continuously transmits a signal toward the ground at transmitted frequency that is repeatedly "ramped" from one output frequency to a another output frequency at known rate (in a sawtooth pattern, low to high, low to high, low to high) and it is the difference between the transmitted frequency the the return frequency that is used to calculate the height, e.g. lets say the output frequency is ramped from 4250 MHz to 4290Mhz at a rate of 1 MHz per µS. If the frequency of the return signal is 4275 Mhz at the moment the transmitter is sending the signal at signal at 4260 MHz, the difference between the signals is 15 Mhz which corresponds to 15 µS, and since the ramp rate is known, this directly corresponds to the height. Of course, this has the opposite problem to the pulse modulated type - there is a maximum height where the return signal "slips over" into the next ramp and gives a false readings. This is why most commercial and military aircraft are equipped with both types; Pulse modulated to give accurate higher altitude readings to assist TCAS (Traffic Collision Avoidance System), and FMCW for low altitude such as terrain avoidance.
 
zorro99 said:
The FAA says there is absolutely nothing to worry about.
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Are you sure about that?
https://www.flyingmag.com/aviation-wireless-5g/
Reuters on Friday quoted FAA Deputy Administrator Bradley Mims from a letter dated Oct. 6, saying the agency shares his “deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band.”
 
LongFuzzy said:
Are you sure about that?
https://www.flyingmag.com/aviation-wireless-5g/
Reuters on Friday quoted FAA Deputy Administrator Bradley Mims from a letter dated Oct. 6, saying the agency shares his “deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band.”
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Indeed!!

Safety concerns about potential interference from the FCC’s proposed C-band change have been an issue in the aviation community for more than a year. Last August, these concerns were raised again during a meeting between aviation industry leaders and the FCC.

Representatives of 19 aviation and aerospace companies and associations at the meeting, including Airbus, Boeing, Lockheed Martin, the Air Line Pilots Association and others, released a joint letter afterward that offered details about their concerns.​

The source of these concerns will be Avionics Engineers, the absolute experts in Aviation electronics.... these people know what they are talking about. Ignore them at your peril!

If we fail to take any notice, then all the lessons we have learned from the 737 Max debacle, and the Challenger and Columbia disasters (where the engineers were warning of the dangers, and were overruled by bean-couners and managers) will have been wasted.
 
Mojo said:
If it’s light enough to read a book, you’re probably getting quite a lot of radiation from the window, or the light bulb.
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All EHS nonsense basically comes down to a fundamental misunderstanding of the electromagnetic spectrum.

I talked to someone who were deadly afraid of 5G but was an avid sun bather... :boggled: I tried to tell them about ionizing vs non-ionizing but the understanding just wasn't there.
 
Airbus and Boeing team up to call for delay of 5G roll-out in US

Well, the airlines themselves are taking this seriously.

https://www.stuff.co.nz/travel/news...team-up-to-call-for-delay-of-5g-rollout-in-us

"The world’s biggest aircraft manufacturers have written to the US government over their concerns a planned roll-out of the 5G wireless network next month could lead to safety issues.

Boeing and Airbus have written to US Transportation Secretary Pete Buttigieg to ask for a delay of communication giants AT&T and Verizon’s planned 5G release in the US on January 5.

Reuters reported that Boeing Chief Executive Dave Calhoun and Airbus Americas CEO Jeffrey Knittel agreed the roll-out "could adversely affect the ability of aircraft to safely operate" and could have "an enormous negative impact on the aviation industry".​

Its understandable why they are doing this. After the furore over MCAS and the Max 8 crashes, the airlines might be a bit nervous and risk-averse. By taking these steps, they are effectively covering their arses... if there is no 5G contributed crash, no harm no foul, but if there is one, they can say "told ya!!" and shift all of the blame onto a couple of Federal agencies.
 
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LongFuzzy said:
Are you sure about that?
https://www.flyingmag.com/aviation-wireless-5g/
Reuters on Friday quoted FAA Deputy Administrator Bradley Mims from a letter dated Oct. 6, saying the agency shares his “deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band.”
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Perhaps they could give all the aircraft radioactive pendants to ward off the interference.
 
Dr.Sid said:
Any technical info about what actually is the issue ?
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You can find the original (in Dutch) here https://www.rivm.nl/bibliotheek/rapporten/2021-0239.pdf

One manufacturer produced products with elevated actinium/radium levels, and the rest have elevated thorium/uranium levels.

The radiation levels reported are typically in the vicinity of .01 to .02 uS/hr.

The Dutch really do have stringent standards.
 
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