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5G could interfere with radio altimeters on most Boeing 737s, FAA says

FAA is warning that 5G emissions could interfere with radio altimeters in most Boeing 737 jets and impact airplane landings.The Federal Aviation Administration's directive affects all Boeing 737 family jets except its 200 and 200-c series, a Federal Register notice posted online on Wednesday said. ( More...

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John Coode 11
It’s the specific frequency band not the 5G technology that is the problem. Important distinction.
Tim Smith 3
Completely agree, John. Whoever supplies the radio altimeters' for the 737 should be responsible for the repair of the radios. There is no excuse for the radio altimeter not being able to isolate itself from nearby frequencies. i.e., Motorola has accomplished this for years with commercial radios.

There is an excellent article that addresses the issue here.
Ken Lane 4
You cannot just suddenly change out the transmitter of several thousand units.

Besides, this was brought on by the FCC and cellular carriers. It's not the fault of aircraft operators.
Douglas Perrenoud 5
I agree that changing all of these altimeters now is a huge challenge. But the FAA has known about the proposed 5G spectrum for over 7 years, and it has had over 2.5 years since the frequency bands were auctioned in order to facilitate the necessary upgrades. The FAA (and the airlines) completely dropped the ball on this.
Ken Lane 5
It has nothing to do with actual 5G technology. It's about FREQUENCY BANDS.

Secondly, the RF altimeters have been in use in their current band for decades. The FCC knew this. They still sold the adjacent band for $80 Billion knowing the likelihood of interference.

It's not on the FAA nor aircraft operators. It's on those who came LAST.
clarify 0
Douglas refers to 5G spectrum, not 5G technology. The band is entirely separate from that designated for radar altimeters.

Furthermore, you say "cannot just suddenly change out". But Douglas rightly points out that the only reason it's "suddenly" is because the FAA and the equipment manufacturers have ignored the issue for 7 years. Where would we be if they'd gotten their act together back then?
Ken Lane 2
There is more than one band being used for 5G. The band in question is directly below that used for RF altimeters.

Who was there FIRST?
godutch 2
Just a quick pass-thru of the document. Can you point out where actual flight tests were conducted and type aircraft/altimeter combination were flown...vs simulations? Thanks.
Tim Dyck 1
Why should owners and users of 737s have to switch out equipment? Seems to me that they were here first and the telecoms should be the ones ensuring their equipment doesn’t put someone else’s previously built equipment in jeopardy.
ADXbear 10
Well there it is.. Alot of alternate airport landings if the intended weather is below Cat 1 approaches.. on the bright side, those passengers will be able to Quickly call someone about there location! 😆
Larry Doench 3
That's really good!
bentwing60 1
ADX, a + 1000!
Brian Freeman 5
Radio altimeters have been around long before cellular technology. Sophomoric perhaps, but cellular should be made to adapt to aviation not the other way around. Reminds me of the whiners who buy a house adjacent to an existing airport then complain about the noise and expect the airport to adapt to them.
William Ableman 3
Well, they're just going to have to land the old-fashioned way, by knowing what 50, 40, 30, 20, 10 feet looks like just by looking.
godutch 6
Could, could, could!!! Where are the tests proving that it DOES??? The aviation world is waiting...
Roy Hunte 4
They have no facts just theory...
Victor Engel 1
Jon Barrett 1
You want to fly the plane they use for testing?
godutch 2
We fly every day in the 5g environment. Actually, I didn't see where actual aircraft were used to test it. And I'm sure any testing will be done in a VFR environment. So...yeah, I would.
Jon Barrett 3
Bench tests are fine; but get into the real world where equipment has to deal with weather (temperature, humidity, wind) effects, and not everything is closely tested to be within tolerances 24/7. The FCC blew it when they didn't listen more carefully to the adjoining band users before they decided to sell the "extra" spectrum to the phone companies.
stuart landau 2
The Federal Communications Commission has become a profit center for the Federal Treasury and the sale of a block of frequencies in C band for 5G is an example. They had been advised that there could be a problem with aviation operations but seemed to have ignored that advice. Talks between the telecommunications and aircraft industries broke off last fall regarding this problem, so now there is a really big issue of flying safety.
The radar altimeters were properly certified when there was not an issue with high-powered radio transmitters located near airports, on an adjacent frequency band. These radar altimeters have operated for decades without these problems. Both sides should have looked at this several years ago to resolve the issue before it came to this.
Malcolm Chouinard 2
Am I missing something? Weren't the airlines using this frequency band long before 5G was every thought of. Why blame the airlines? Shouldn't the electrical engineers at the telecommunications companies done a better job of developing new technology?
Anthony Fiti 4
To quote a famous commercial “that’s now how this works, that’s not how any of this works!”

There is nothing wrong with 5G. The issue is that prior to this particular chuck of radio spectrum being auctioned in 2020, the FCC and FAA did not coordinate sufficiently to ensure there would be no interference.

In fact Boeing submitted paperwork to the FCC to say that they thought that they would only need a 20 MHz guard band, which the FCC implemented (it’s why this particular chunk of cell phone spectrum stops at 3.98 GHz instead of going all the way to 4 GHz). You can search google for “Boeing C-Band NPRM reply comments” to read their statement from 2018.

From that response: Radio altimeters are already “properly engineered” to resist spurious emissions from external sources. The band pass filters that are incorporated into radio altimeters, however, have limited ability to reject transmissions close to the edges of the 4.2-4.4 GHz band.

Boeing goes on to say that they shouldn’t allow mobile communitarians in the 4.1-4.2GHz band. Which came to pass.
In this case it is a wider bandwidth causing the problem. Cheap equipment. Bad quality. Greedy guys. Why not affecting Airbus or Embraer?
“Impact landing” gets my attention.
William Cavico 3
I worked as a communication technician from 1983 through 2002 in data communications from before 800 numbers to after the impementation of what became the internet.

All I want from a telephone is to be able punch in some numbers and speak with someone and maybe leave a voice mail message. When I was in high school there was no such thing as cell phones.

There actually was a time when there wasn't anything called a telephone.

In my 75th year I have live to see tech junkies with hundreds of phone applications they didnt now they needed before they got a phone.

Most shocking is these people are weighing the ease of use of cell phones and all its needed(haaha !) aps in their right hand and weighting it against the lives of hundreds of people in airplanes in their left hand!!!!!


Bill C.
avionik99 3
Not one single shred of evidence has ever been reported to show 5G is of any hazard whatsoever. Just mights, coulds, possibles, ifs etc. We have the technology to easily prove 5G is dangerous but yet Nothing!! And in this day and age of falsely manufactured evidence even that has not been used! So there is something fishy going on at the FAA that has them running scared.
MAX, maybe?
Ken Lane 1
The Max crashes had to do with a system with bugs that was installed on the aircraft Boeing never disclosed to either the buyers nor the FAA. That has absolutely nothing to do with 5G or RF bands.
godutch 1
Max crashes were at affect.
You asked about the FAA. I think they are on the ground.
The point being that their prior certification of a faulty product made the FAA more cautious.
Michael Wise 1
Crashes at altitude?
Victor Engel 5
Error condition happened at altitude (actually, in the two crashes it was shortly after takeoff I believe) causing the plane to pitch downward. Watch Downfall: the Case Against Boeing on Netflix.
Jim Ward 1
Great documentary. Just watched. Thanks for sharing.
godutch 2
He asked if this issue related to the 737 Max crashes. I said they were issues/caused at altitude. THIS (5G) is a lower altitude issue.
w2bsa 1
That doesn’t mean that Boeing didn’t get cheap on other equipment.
Jeff Hill 2
It doesn't mean they did get cheap on their equipment either. The instrument manufacturers are responsible for making sure that their equipment doesn't interfere or accept interference from nearby frequencies, and apparently didn't do their job. We'd have to see the specs that they sold to Boeing to really know who cheaped out on this.
As any equipment you can have one of better quality than another. This will reflect on the cost. I am sure that this one is cheaper than the ones used by EMbraer and Airbus. Cheaper circuitry, with no problems BEFORE 5G. Like an old radio with bad quality Intermediate Frequency filter.
Max, probably. Doesn't have with the two crashes, but show how cheap equipment they are installing on their planes. Greedy guys.
w2bsa 1
Could be. If they had flaws in one piece of equipment, it’s very possible that there are flaws in other pieces of equipment. As I have said earlier I have to wonder if Boeing was cutting corners just to sell airplanes. Also, it should be a simple fix to install the electronic filters needed to filter the 5G frequencies. It should only transmitting and receiving in the specific frequency band the equipment is assigned. Frankly, that’s what make this whole issue strange to me. What did Boeing do get cheap on the radio altitude equipment??
Ken Lane 3
You would be wrong. Studies started two years ago regarding the interference after the FCC chose to collect $80 Billion in fees instead of insuring there would be no interference.
Tim Dyck 1
So should we just wait for a loaded passenger jet to crash befor we decide it’s a bad idea? Or could we err on the side of caution and just not use that band with the 5G? Why is it so important to the cell carriers to have this band width that they are willing to risk people’s lives?
Ken Lane 2
It wasn't. And, the FCC didn't care about potential interference as they collected $80 Billion in fees for giving away the band to cellular carriers.
William Cavico 1
People please keep in mind that mmicrowave power satellites are back on the drawing board being backed by the military for military uses. How this 5G issue is resolved will be a learning example for similiar problems to come.

Bill C.
w2bsa -2
This says to me that it not the 5G technology it’s the specific equipment used in those airplanes. I also have to wonder if Boeing cut some corners on those specific pieces of equipment. Proper electronic filters need to be installed in those pieces of equipment to prevent that kind of interference.
Craig Good -1
So the 737 needs an upgrade to one that does a better job of rejecting off-frequency input.
Michael Penney 2
No one builds a radio receiver (1/2 of an altimeter) with perfect total out of band frequency rejection. Physics does not work that way. Frequency may be modulated digitally but it is in fact not digital. You build good enough. Now thanks to FCC good enough is no longer good enough.

Proving safe requires testing all versions of antennas, altimeters, Cell equipment in real world environments to show mutual compatibility. Just pray that there will not be two or three crashes before the world figures out there is a problem.


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