In conclusion
It appears that air may interfere with Boeing 737s
FAA now says 5G airports may interfere with Boeing 737s
The US Federal Aviation Administration warned on Wednesday that 5G C-band transmissions may interfere with landing operations at a limited set of airports for most Boeing 737 aircraft. It issued an advisory calling for affected planes to observe modified operating procedures where 5G interference might occur. The FAA in …
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Thursday 24th February 2022 05:49 GMT pavel.petrman
Re: In conclusion
Last few years have indeed shown us that to ensure the award winning* safety and reliability of 737s, they should not be put in contact with air in any manner.
* "Award winning" appears to be a compulsory grammatical particle in any sentence related to the award winning United States of Erica.
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Thursday 24th February 2022 12:43 GMT vtcodger
Re: In conclusion
* "Award winning" appears to be a compulsory grammatical particle in any sentence related to the award winning United States of Erica.
Indeed. "Award Winning" is an example of the a ninth grammatical category on top of the traditional eight -- noun, pronoun, verb, adjective, adverb, preposition, conjunction, and interjection. The ninth category is called the hype and apparently entered the language in North America in the mid Twentieth Century. It is used in place of, or along with, adjectives or pronouns and has no known utility other than being occasionally useful to pad the length of a line of poetry or song.
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Thursday 24th February 2022 08:51 GMT Chris G
Re: In conclusion
"It appears that air may interfere with Boeing 737s"
And while tin foil may limit 5G signals from penetrating your brain, they may be less effective protecting you from a 737 attempting a landing.
It seems there is not much communication between federal agencies when it comes to managing mutual resources.
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Thursday 24th February 2022 17:48 GMT jtaylor
Re: Boing it on the cheap.
"a decades old platform, the technical debt keeps on accumulating, and at some point it bites you"
What do you propose in place of radar altimeters? Airlines do have GPS (newer tech) and barometers (older tech) but those provide only the location of the aircraft, not of obstacles beneath.
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Friday 25th February 2022 09:21 GMT Martin an gof
Re: Boing it on the cheap.
A similar question came to my mind.
These kinds of aircraft systems are not unique to one specific model of aircraft as far as I am aware. Since every single commercial 'plane carries a radio altimeter these days and most of those will use its data as input for auto pilot systems, why is the 737 being singled out? Surely similar problems will hit other Boeing aircraft and, indeed, Airbus etc. too?
Oh, and if it's particulalry a problem at airports, surely the use of that band can be restricted near airports? 5G operates on many different bands and a bit of careful frequency planning could go a long way to solving this problem.
Oh, I forgot. Corporations know best and can't be regulated too heavily.
M.
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Friday 25th February 2022 21:13 GMT MachDiamond
Re: Boing it on the cheap.
"What do you propose in place of radar altimeters?"
Another radar altimeter.
The issue with aircraft electronics is they take forever to be certified and the cost is very high. A company can spend tens of thousands to get a certification on something that costs £50 to make. This means that the part has to sell for thousands each to make back the initial investment. The same applies to upgrades of existing devices. The airlines are not going to be happy to need to replace all of their radar altimeters in every 737 they own. The cost could be £100k or more each since it takes union mechanic that holds an Airframe and Powerplant (A&P) license to perform the work. Provided, of course, that it doesn't take any modifications to the aircraft to fit the new kit.
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Thursday 24th February 2022 17:58 GMT jtaylor
Re: So now you do the testing?
The FAA warned about this 6 months ago. https://www.reuters.com/business/aerospace-defense/faa-has-deep-concern-about-5g-network-plan-aviation-safety-letter-2021-10-29/
They didn't sell the spectrum, the FCC did. Please keep in mind that not every country has privatized its airwaves.
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Friday 25th February 2022 21:19 GMT MachDiamond
Re: So now you do the testing?
"But the FCC could have put a proviso on that particular block of frequencies that they are restricted near airports."
Why would they do that? Most government agents are pandering to industry so they will have a cushy job waiting for them when they stop feeding at the public trough. If you analyze decisions made with this in mind, you start to see the rationale behind the policies.
I would also think that 5G in and around airports is going to be very important to customers.
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Friday 25th February 2022 01:49 GMT Yes Me
Re: So now you do the testing?
Please point to a reference for that "practical experience".
I am still in disbelief that the people who designed radio altimeters in the 1960s would have made them susceptible to sidebands from a 3.98 GHz channel but not from a 3.80 GHz channel, which appears to be the FAA assertion. So where is the evidence?
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Thursday 24th February 2022 09:05 GMT tip pc
Just when they are trying to convince us it’s safe
Yet another bad optics story for the 737.
I really don’t want to fly on a 737 again and actively choose airlines that don’t fly that aircraft. Sadly that puts sleazy jet on that list, but they are still on my no fly list.
We flew TUI to Menorca in 2018, they subbed the flight out to Norwegian and it was a 737, not sure if it was a new NG or Max. If was well appointed with large screens, free WiFi, it was a comfy cabin and comfy flight. Good enough it was memorable for being good. I hope it was an NG, I won’t now knowingly get in a Max though.
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Thursday 24th February 2022 15:13 GMT First Light
Re: Just when they are trying to convince us it’s safe
I always check when booking, but to be sure also check the safety card when on board. I flew with Norwegian and the safety card said 737 Max/NG meaning the card could be used for both types. I was assured by the attendant that we were flying on an NG.
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Thursday 24th February 2022 16:51 GMT jdiebdhidbsusbvwbsidnsoskebid
Re: Just when they are trying to convince us it’s safe
"Just about every modern airliner, from any manufacturer, relies on the same technology"
Not exactly the same technology. They might transmit in the same band but that's because they have to use the band licensed for radar altimeters. Not all radalts are the same. Different devices use different waveforms, processing, power levels etc. And the plane manufacturers don't necessarily design the radalts themselves. They might specify them in terms of form,fit and function, but they'll come from a supplier, and not all aircraft manufactures will use the same supplier. Different radalts will have different levels of susceptibility to interference, whether by accident or by design.
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Friday 25th February 2022 05:25 GMT rnturn
Re: Just when they are trying to convince us it’s safe
"Not all radalts are the same."
Indeed. I was involved in some work back in the '80s that discovered that FM radio station transmitters -- and the stew of intermodulation frequencies that resulted from multiple FM transmitters in a locale -- could interfere with ILS receiver front ends. Not all receivers were susceptible to the same degree but some of the more commonly used (especially in general aviation) were affected the most. I recall wanting to be a fly on the wall at the meeting where the report was to be presented to the FCC (who would represent radio station operators who could be denied either an antenna location or proposed transmitter power if either interfered with the landing system) and the FAA (whose interested was in maintaining the protected airspace around an airport)---the fireworks would have been fun to watch.
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Thursday 24th February 2022 12:03 GMT Anonymous Coward
Re: The Downfall: Boeing doc on Netflix.
I didn't think much of the new Netflix Documentary, as someone that has been following this from the beginning since the first crash (and following Boeing long before that), there wasn't anything new. The hidden footage of workers, was all previous footage.
All it seemed to show was the complete lack of ethics/morals at the top of the company, again that was known, from previous investigations. Just seemed to be a rehash, I've seen better YouTube content.
The documentary also missed a very important point: One thing that wasn't clear, was that if the pilot (as they did in flight ET302) turned off the MCAS system, what were the effects of not trimming to neutral before hitting Cut-Off.
Describing MCAS as achieved by adding a few lines of code, seemed a pretty dumbed down, crude description for the programmers that had worked on it.
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Thursday 24th February 2022 17:27 GMT tip pc
Re: The Downfall: Boeing doc on Netflix.
The documentary also missed a very important point: One thing that wasn't clear, was that if the pilot (as they did in flight ET302) turned off the MCAS system, what were the effects of not trimming to neutral before hitting Cut-Off.
They couldn’t trim to neutral because MCAS would keep cutting in. My understanding is that MCAS stopped the trim action when it was activated. So you keep pressing trim and it dies what you want until MCAS cuts in and does the opposite for 10s before stopping for 5 & repeating.
Do your stabbing trim, see the wheel move the right way, keep stabbing trim and then the wheel moves the wrong way for 10s. Dealing with an unknown crisis just after you’ve put the flaps away something like that would be super confusing especially when you either don’t know about MCAS of have just heard about it and this is the first time experiencing what it does.
As the documentary explained, turning off the electric trim after MCAS has activated, just like the Ethiopian pilots did, is not good enough as if it’s deployed too far and speed high the aero forces are too much to manually adjust the trim.
These are things older 737 pilots knew because I’d an issue wihh to older jets that was rightfully designed out but new pilots had no idea as even Boeing didn’t know it was a thing at that point.
Don’t try and blame the pilots for Boeings deliberate attempts to hide MCAS and not take responsibility for its actions.
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Thursday 24th February 2022 14:55 GMT Alan Brown
Re: The Downfall: Boeing doc on Netflix.
It's not just the Max
The NG had major issues too:
https://www.huffpost.com/entry/boeing-whistleblowers-unc_n_797515
The fact that the FAA was utterly owned by Boeing by 2005 is underscored by the fact the whistleblowers were shopped back to the company by FCC officials (a federal crime in itself) within days and no punishment or investigation ever ensued
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Thursday 24th February 2022 10:21 GMT steamnut
Why the 737?
Doesn't is strike you as odd that Airbus planes are seemingly ok? They too use radio altimeters. Surely the FCC and others who dish out band allocations thought about the possibilities of interference or are Boeing a bit marginal on the EMC specs? Is this something else that Boeing slipped under the radar with the FCC?
Going to watch the Netflix program tonight. I'm sure it will not be very complementary.
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Thursday 24th February 2022 17:17 GMT jdiebdhidbsusbvwbsidnsoskebid
Re: Why the 737?
"Doesn't is strike you as odd that Airbus planes are seemingly ok? They too use radio altimeters."
Don't know about Boeing, but I do know that airbus tend to use a particular design of radar altimeter, that might be standard across the whole fleet. I also know that that particular design is more robust against interference than other designs. Other design considerations could trade off that robustness for other things, so I'm speculating as to why airbus is not affected - yet.
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Thursday 24th February 2022 11:19 GMT TeeCee
There may be more.
I have seen it reported elsewhere that this is not a 5G problem or a 737 problem, but a US of A one. Hence the lack of panic elsewhere, despite other places having airports and having 737s land at them.
In a nutshell, the USA has a 5G band bang against the aviation one and some bleed over is inevitable. Funny that when a small company tried to do this (Lightsquared) they got shut down, but when the big telcos wanted to do the same it went through. I wonder how much that cost in
bribeslobbying and feasibility studies?While they have a similar allocation issue in Japan, there they have mandated beamforming antennae on cell towers close to airports which aim the signal along and down rather than up. For some reason (cost to the telcos bringing out the
bribelobby cash must be favourite), the US hasn't done this. -
Thursday 24th February 2022 12:10 GMT Electronics'R'Us
Out of band power
5G uses QAM as the modulation method (16, 64 and 256 equating to 4, 6 and 8 bits per symbol).
The power spectral density (PSD) mathematically extends to infinity.
The key question is just how much power extends beyond the allocated band and in what direction.
Radar and radio altimeters have very sensitive receivers [1] so if there is sufficient out of band power from a 5G transmitter it can interfere with the receiver most likely both directly and by intermodulation products.
The fact that Japan (which uses the same bands) has mandated beamforming [2] and requiring the signal to point downwards mitigates the problem significantly.
There are 2 fundamental types of radio altimeter; pulsed (which is more properly referred to as a radar altimeter) and frequency modulated continuous wave (FMCW). The first uses time of flight to calculate the altitude and the second compares the received frequency to the currently transmitted frequency. (That's the simple description - entire books have been written on the subject).
Both types can be susceptible but FMCW (very common for approach and landing radio altimeters) is particularly susceptible to intermodulation issues which is highly likely to be the problem here.
1. Below -100dBm (that's 0.1 picowatt or 100 femtowatt)
2. This has its own issues but outside of the main lobe the signal can be suppressed significantly.
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Thursday 24th February 2022 17:13 GMT DaemonProcess
Re: Out of band power
Thanks for that info, I'm generally ignorant of this tech - it is a bit like doppler but with EMR instead of sound?
Another ignorant teenager's question along the lines of tin foil hats, couldn't they just fit upside-down metal umbrellas on top of the 5G transmitter towers near to airports..
The Japanese method seems more power efficient to me anyway.
Verizon / Comcast / whoever's board is penny pinching a couple of million in spend when their accounts report in billions.
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Thursday 24th February 2022 17:32 GMT jdiebdhidbsusbvwbsidnsoskebid
Re: Out of band power
"Thanks for that info, I'm generally ignorant of this tech - it is a bit like doppler but with EMR instead of sound?"
Kind of like Doppler, in the sense that the FMCW radalt measures a frequency shift, and translates that into a time.
The FMCW radalt transmits a chirp waveform (the frequency increases linearly over the duration of the pulse). While that is propagating to the ground and back, there is the same replica waveform running inside the device. Because of the time taken for the transmitted waveform to return back from the ground, it arrives with a frequency shift compared to the replica waveform which has been increasing in frequency during the transmission. The replica and received waveforms are mixed together to produce a signal with a frequency equal to the difference in frequencies of the replica and transmitted waveforms. Because you know the chirp rate, you can easily convert that frequency difference to a time, and thence a distance.
By using a chirp waveform, you can have a longer pulse, which means more energy (not power) in the pulse, which makes it more robust against interference (or, you can trade off transmitted power instead). A fixed frequency pulse has to be a lot shorter to avoid interfering with itself when the ground return comes back (you must stop transmitting before the ground return comes back). The chirp waveform can still be transmitting while the ground return comes back, the changing frequency giving you the discrimination to still see the return signal.
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Thursday 24th February 2022 16:45 GMT Marty McFly
The blame
Everyone likes to jump all over Boeing at the slightest excuse. It seems to me the FCC & FAA are not doing their jobs. These frequencies should not have been allocated to 5G if they cause interference with aircraft, regardless of the manufacturer & model.
Oh, and let's not forget... This is the same industry that has told us to shut off all electronic devices to keep them from interfering with aircraft systems. I have yet to hear about a plane crashing because someone in seat 23C forgot to switch off their cell phone.
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Friday 25th February 2022 02:16 GMT sanmigueelbeer
In other Boeing-related news: Each Boeing 787 Dreamliner Produced Will Have to Be Individually Certified By FAA
Not really a Boeing-related fault but still looks bad for the company.
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Friday 25th February 2022 14:17 GMT W4YBO
"Concerns about the effect 5G signals may have on aviation systems have been discussed for years..."
FAA and FCC have both been aware of the problem since the late 1990s. If you listen to top-of-the-hour radio newscasts and have noticed occasional gaps in the audio, sometimes accompanied by a squeak, then you have too. It's often caused by a C band radar altimeter flying directly over the C band satellite antenna. Operating a licensed (supposedly interference protected) ground station digital audio receiver, the broadcaster I worked for filed several interference complaints. I'm retired now, but I still notice the holes and squeaks in the news audio. It'll probably take great loss of life before they actually do something about it.
