What are the concerns with 5G and airplanes?

[russ_watters]

TL;DR Summary

What's the deal with 5G and airplanes?

The basics of this issue is that AT&T and Verizon were set to turn on C-Band 5G service tomorrow, but the roll-out has been halted by the Biden admin because it could interfere with radar altimeters on airplanes.
https://www.reuters.com/technology/...tion-avoid-catastrophic-5g-flight-2022-01-17/

But I have some questions:

• What about T-Mobile? My GF has T-Mobile and it says she has 5G. What's up with that?
• I have a verizon phone. It says it's on 5G now. What's up with that?
• Other countries already have this too and it's all fine. What's up with that?
• The FAA, airlines and manufacturers evidently saw this coming. What's up with that?
• The FAA has cleared 45% of the airplane fleet at certain airplanes. Airplanes or airports? And/or?

 

[Baluncore]

Some radio altimeters can be jammed when flying near or over a 5G towers.
The altimeters are only essential when instrument landing in bad wx.
Certifying and replacing the altimeters is a slow process.
5G towers need to be kept away from landing flight approach path until the conversion is complete.

 

[anorlunda]

Summary:: What's the deal with 5G and airplanes?

Other countries already have this too and it's all fine. What's up with that?

On the news tonight they said

1. USA 5G signal strength is twice as strong as European 5G.
2. In Europe, they ban 5G for a radius around the airports three times bigger than the radius in the USA.

Summary:: What's the deal with 5G and airplanes?

I have a verizon phone. It says it's on 5G now. What's up with that?

The 5G spectrum band is not contiguous. The rollout this week was for a frequency segment not previously used by 5G. That is the segment close to the band used for radio altimeters.

 

[berkeman]

Related thread from last December:

https://www.physicsforums.com/threa...-delay-in-u-s-5g-wireless-deployment.1010462/

The main issue seems to be the TX signal strength that the US phone carriers are trying to use (way stronger than is currently used in Europe). The nightly news program that I watched tonight erroneously said "twice as strong", but they obviously don't understand how dB levels work...

 

[phinds]

The nightly news program that I watched tonight erroneously said "twice as strong", but they obviously don't understand how dB levels work...

That's 'cause they're in the business of presenting "news", not actual information.

 

[Astronuc]

Summary:: What's the deal with 5G and airplanes?

AT&T and Verizon were set to turn on C-Band 5G service tomorrow

What I heard this evening is that the roll-out will happen tomorrow with the exception of certain airports.

The questions I had last night were, "Why is this happening now? Why wasn't this identified issue early on and solution implemented?"

If certain aircraft need the radio altimeter in poor visibility conditions, then what about good visibility? If not needed, then pick an airport or airports with good visibility with 5G towers in sensitive locations and fly susceptible aircraft over them to see if they are actually affected.

 

[berkeman]

If certain aircraft need the radio altimeter in poor visibility conditions, then what about good visibility? If not needed, then pick an airport or airports with good visibility with 5G towers in sensitive locations and fly susceptible aircraft over them to see if they are actually affected.

On the nightly news tonight they mentioned that since SFO (San Francisco) often has limited visibility, SJO (nearby San Jose) which rarely has limited visibility is getting ready for increased diversion traffic.

 

[Baluncore]

The questions I had last night were, "Why is this happening now? Why wasn't this identified issue early on and solution implemented?"

The airlines are Covid broke, while the cell phone companies are rolling in it. If the cell phone companies had to pay to replace the altimeters, it would have been finished last year and all would be well.

If not needed, then pick an airport or airports with good visibility with 5G towers in sensitive locations and fly susceptible aircraft over them to see if they are actually affected.

Digital systems are difficult to test by monte carlo techniques.
How many more samples would be needed to verify that sometimes it fails?

 

[berkeman]

Digital systems are difficult to test by monte carlo techniques.
How many more samples would be needed to verify that sometimes it fails?

I have hung out of Subway trains on the manufacturer's test track in the snow in upper New York trying to debug communication issues with our twisted pair control networks on their trains. Luckily these airline engineers don't need to hang out of the plane to monitor the signal-to-noise of the radar altimeter equipment...

 

[Astronuc]

The airlines are Covid broke, while the cell phone companies are rolling in it. If the cell phone companies had to pay to replace the altimeters, it would have been finished last year and all would be well.Digital systems are difficult to test by monte carlo techniques.
How many more samples would be needed to verify that sometimes it fails?

Fair points, which brings me back to, "Why now!?"

By the early 2000s, developers knew that 3G and even 4G networks wouldn’t be able to support such a network. As 4G’s latency of between 40ms and 60ms is too slow for real-time responses, a number of researchers started developing the next generation of mobile networks.

In 2008, NASA helped launch the Machine-to-Machine Intelligence (M2Mi) Corp to develop IoT and M2M technology, as well as the 5G technology needed to support it. In the same year, South Korea developed a 5G R&D program, while New York University founded the 5G-focused NYU WIRELESS in 2012.

https://www.brainbridge.be/en/blog/1g-5g-brief-history-evolution-mobile-standards

And this problem couldn't have been addressed by 2018, 2019, 2020?

Do Airbus aircraft have a problem, or is this domestic US? Seems Airbus has been thinking about this issue.

https://securecommunications.airbus.com/en/meet-the-experts/the-history-of-the-5g-technology

 

[tech99]

This seems a useful summary. (Don't confuse 5G meaning fifth generation mobile and 5 GHz) :-
Radio altimeters operate in the 4.2 gigahertz to 4.4 gigahertz band, and the US has set aside a portion of the spectrum right up to the lower band of that for 5G. In the UK, the comparable band ends at 4 gigahertz and in the EU, it ends at 3.8 gigahertz.

Read more: https://www.newscientist.com/articl...really-interfere-with-aircraft/#ixzz7ISPWqU9o

 

[anorlunda]

Is there any information in today's world that isn't misinformation? I don't know what to believe any more.

https://arstechnica.com/tech-policy...now-say-5g-isnt-a-big-problem-for-altimeters/

Airline CEOs make U-turn, now say 5G isn’t a big problem for altimeters​

 

[phinds]

Is there any information in today's world that isn't misinformation?

Well, there's a science forum called "The Physics Forums" which just about always has solid information. I can't say the same for much of anyplace else.

 

[anorlunda]

Well, there's a science forum called "The Physics Forums" which just about always has solid information. I can't say the same for much of anyplace else.

Correct. I should have said "news" rather than information.

 

[russ_watters]

Is there any information in today's world that isn't misinformation? I don't know what to believe any more.

From the link, this is not shocking:

The FAA didn't start its process of evaluating the actual altimeters used by airplanes after February 2020, when the Federal Communications Commission approved the use of C-Band spectrum for 5G. The FAA also didn't start this evaluation process after the FCC auctioned off the spectrum to wireless carriers in February 2021. Instead, the FAA continued arguing that 5G deployment should be blocked long after carriers started preparing their equipment and towers to use the C-band.

Sounds normal to me!

 

[anorlunda]

Sounds normal to me!

I was thinking more of the press and the airlines than the government.

From January 17:

US airline officials warn of ‘catastrophic’ crisis in aviation with new 5G service​

From January 21:

Airline CEOs make U-turn, now say 5G isn’t a big problem for altimeters​

Somebody made an enormous flip in just four days. It's unclear if it was the media or the airlines, but in this case it does not seem to be the government.

 

[russ_watters]

Somebody made an enormous flip in just four days. It's unclear if it was the media or the airlines, but in this case it does not seem to be the government.

Isn't the flip that the government finally stopped arguing against itself and finally started actually checking to see if there was an actual problem? Click-through from that article to an FAA press release Thursday:

The FAA issued new approvals Thursday that allow an estimated 78 percent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band. This now includes some regional jets.

Airplane models with one of the 13 cleared altimeters include all Boeing 717, 737, 747, 757, 767, 777, 787, MD-10/-11; all Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models; and some Embraer 170 and 190 regional jets.

The FAA is working diligently to determine which altimeters are reliable and accurate where 5G is deployed in the United States. We anticipate some altimeters will be too susceptible to 5G interference. To preserve safety, aircraft with those altimeters will be prohibited from performing low-visibility landings where 5G is deployed because the altimeter could provide inaccurate information.

Why couldn't they have done the checks/issued the approval some other time in the past to years?

 

[Dullard]

They just remembered that they have barometric altimeters?

 

[anorlunda]

They just remembered that they have barometric altimeters?

Not good enough for low visibility landings.

Not good for any landing. Barometric pressure does not tell you height above the ground.

 

[Baluncore]

Barometric pressure does not tell you height above the ground.

With the latest QNH it gives an outdated approximation of altitude, but not a sufficiently accurate ground clearance.

 

[Dullard]

I don't think (maybe I'm wrong) that they land commercial aircraft completely 'blind.' Some visibility is required at some minimum altitude. I get your point though - I'm thinking like the Florida flat-lander that I am.

 

[anorlunda]

I don't think (maybe I'm wrong) that they land commercial aircraft completely 'blind.' Some visibility is required at some minimum altitude.

Many modern airliners are equipped for fully automated hands-off autoland, although it may be seldome used.

Here is some relevant info about radio altimeters in airliners.

https://skybrary.aero/articles/radio-altimeter
Early radio altimeters determined altitude by measuring the time between transmission of a radio signal from the aircraft and reception of the reflected signal. Modern systems use other means, for example, measurement of the change of phase between the transmitted and reflected signal.

In almost all cases, the display of radio height ceases when an aircraft climbs through 2500' above ground level (agl) and recommences when it descends through 2500' agl. This is confirmed visually by the appearance/disappearance of an 'OFF' flag and emergence of a pointer from behind a mask or activation of a digital display.

Radio altimeter calls may be either:

• Announced by one of the pilots, usually the Pilot Flying (PF) and Pilot Monitoring (PM), either in accordance with an SOPs or on an ad hoc basis, or
• Generated automatically by a synthetic voice. (For example: "Thirty feet")

Many operators have an SOPs which requires a pilot call of "Rad Alt Live" to be made during descent as soon as practicable after height indications reappear at 2500 feet agl in order to enhance crew awareness of proximity to terrain.

Use of the radio altimeter is integral to both the function of ground proximity warning systems and to the operation of aircraft during Cat 2/3 approaches where it is used to determine the position of the aircraft in relation to the applicable decision height.

There might be alternative procedures that don't use the radio altimeter, however the minimums would be different for those procedures and the airline SOPs may restrict their use.

 

[tech99]

On a point of accuracy, I believe radio altimeters have always used FM radar, never a pulse system, originally at 420 MHz using acorn tubes.

 

[Tom.G]

I seem to recall once having an old piece of equipment using either the 955 or 957 acorn tube, don't recall what it was in though.

The overall physical size was somewhat smaller than the end phalanx of your thumb.

See also:
https://en.wikipedia.org/wiki/Acorn_tube

Cheers,
Tom