No we are well past that point. Engineering judgement is supposed to balance the conflicts. Your example is what happens when the uninformed make important decisions without asking the correct questions.

Bit of rumour and history.

Any telecoms types feel free to correct me.

In the 90's when GSM was kicking off there was a battle between the aviation regulators the radio freq authorities and the phone OEMs.

The aviation regulators wanted the phone OEMs to certify the phones for aviation use and pay for it. At the time it was Nokia and Ericsson. They said no we are not certify every handset, just to get one done would be a fortune and take months and we fully expect to have new models every 6 months.

The aviation regulators the went to the radio feds and they said nothing to do with us.

So they banned them on aircraft.

But in the mean while they changed the certification standards so aircraft are more radio hardened.

This C band Freq is actually used in 3-4 systems.

The rad alt data is used for low Viz approaches Cat 2 and cat 3. But it's also linked into terrain avoidance and traffic.

Now the problem the FAA has is that the USA uses alot of old aircraft that predate the certification change or they have grandfathered from older models. So John it is sort of related to MAX issues.

It's not going to effect a 787 or 777 but nobody has a clue about the MAX or NG.

The radio feds want the cash from the frequency sale. And have absolutely zero interest again with aviation issues. Which they see as the aviation regulators fault for not dealing with years ago. The 5G frequency was in white papers before 2000.

Airbus, Bombardier, embraer etc have all had the issue sorted years ago. Boeing I believe haven't due grandfathered certification rules.

Please don't take any of the above as fact, but it's what believe is what the issue is.

They basically have a choice of down grade the aircraft effected so they can't operate in less than 200ft cloud base or 550meters Viz. Or find some way of turning 5G off when the airport's go low Viz approaches. Or have 5G black areas around airport approaches.

It's a political hot potato. Because its billions of dollars industry that are clashing against each other.

If the FAA does nothing and a fatal accident occurs then all hell will let loose again.

To note the 5G band in Europe is 3.4-3.8 GHz

USA it's 3.7 to 4.2

The rad ALTs work at 4.2 to 4.4.

I don't have a clue who decided that 4.2-4.4 was for rad alt.

I think it was a UK invention which is why it fits in with the European frequency allocation.

Spend some time on short wave radio and you will be amazed at how many different applications use various bandwidths.
A lot of these are 'short range' applications that aren't supposed to interfere. But over time many of these have seen increases in efficiency and power and now they interfere a lot.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

The modern rad ALTs fire coded pulses and ignore everything else. Code changes every pulse and it's octo or hex.

And modern aircraft have 3 rad alts and then compare them and then throw up a flag that one has been pulled from the mix and as long as the last two agree you can continue. Once they disagree then you have to bin it unless you can see the runway. You can go with just one but then you can't do any approaches that require radalt.

But it may screw with other systems.

The Turkish crash in skipol is a prime example.

The 737 only has suprise suprise 2 rad ALTs. One went tits up and the autothrottle went into retard landing mode thinking it was at -8 ft and pulled the power to flight idle the pilot didn't spot it. And they stalled and crashed every one dead.

The old systems just use a straight squirt without any code so are much more vulnerable to getting confused.


The frequency clash though is the old GSM bun fight over 850 and 900 MHz.

I think the US didn't want rad alt to use that band. But by the time they jumped on the band wagon the rest of the world were using it. But it fitted nicely with European frequency allocation, it was in an awkward hole in the US taking up two blocks instead of 1. And they seem to be trying to use one of those blocks for 5G.

The bulk of the USA domestic fleet though is legacy aircraft types. 2 rad ALTs no coding.

It must effect Canada as well and south America. I think they are 850 GSM as well.

Sorry just looked at the books

It's a frequency modulated continuous wave radar not a pulse.

There is a code in there somewhere though I believe.

I don't need to know how it works to be honest. Just what to do if one or more fails.

A good presentation on the issue

Quote (blancolirio)

5G C-Band Interference with Radar Altimeters in Aviation

Really good presentation.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

FM CW is what we used to call a Radio altimeter, as opposed to Radar Altimeters which are pulsed devices. I think I saw my first random-pulsed Radalt in the late 1980s (that one frequency-hopped as well, just for fun).

The Radio Alts used a linear sweep on the transmit frequency, then mixed that with the return to provide a beat whose frequency depended linearly on the difference between the two frequencies, hence on the delay between transmit and receive and hence on altitude. Feeding that into a Frequency to Voltage converter allowed you to drive a meter. I always thought that was a really ingenious low-tech solution.

A.

I think they also have a Doppler function as well these days that feeds into the egpws for windshear.

But it's one of these systems that has been linked into multiple other things apart from it's primary job. But it's not really been touched.

The A3xx family apart from the A380 apparently is effected as well. They also only have 2 so no error Cheching or voting.

Among all of the technical issues that are raised, the most interesting to me right now are actually philosophical.

To the FCC, consequences of failure that drive reliability analysis are driven economically.
To the FAA, consequences of failure that drive reliability analysis are driven by fatalities.

The FCC's testimony to Congress has taken the stance that "there's never been a problem" which is probably true. So from their perspective the precautions they have already taken are adequate and justified.

The FAA disagrees, but not by disregarding the facts put forward by the FCC, but because the FAA isn't permitted to rely on "never been a problem". The aviation safety mentality does not allow for designers, engineers or pilots to ignore known risks. For example, the whole underlying failure in the 737 MCAS saga was "never been a problem" until is suddenly was. The FAA has a much higher standard of proof than the FCC, viewed in this perspective. The FAA has spent decades developing policy and analytical methods to find, quantify, and manage risks to a level unseen in most other industrial sectors.

The FAA doesn't have the deep pockets to pay for the in-flight testing needed to prove interference or non-interference, to their standard of evidence. The test program would be very costly, take a long time, and require specially-equipped aircraft to collect the data.

Complicating matters, unfortunately, is the economics between the two governmental agencies are drastically different. The FCC spectrum auctions are worth billions of dollars of revenue to the FCC. The FAA bears most of the cost of all major certification programs, to the tune of millions of dollars. Maybe the FAA can do some cost recovery on big programs, but that's it.

It's not a level playing field.

different red lines FAA is 1 in 1 million flights fatality rate which means one crash per year with 1 death in the USA airspace and the FCC can make it up as they go along and claim no data.

FCC gets shit loads of billions into the bank due license sales. And realistically its not their problem the rest of the world as said screw you to the radio alt frequency. And the FAA has had over 20 years warning in the matter.

BTW the rad alt freq will not change. End of and don't even thick it will happen. The rest of teh world which does have sep on the freqs everything works great and nobody cares that the local domestic is screwed for low viz.

I might add I have done 8 low vis approaches out of 18 in the last 7 days which required the rad alt to be operational and legal and we would not have landed without it. And if I didn't have that tick in the box it would have meant at least another 20 tons of fuel loaded. And thats only in the last 7 days.

FMCW should be tolerant of random noise (to it), since the frequency chirp is fairly unique

TTFN (ta ta for now)
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Its the old no triple data source and no error voting tolerance aka 73& max.

On board they all run at different frequency's so if two disagree the system dies, three and they can pull the one that disagrees out the mix and we can continue downgraded to 2. We can actually currently (well we could on the Q400) do them with only one working and one tech with I think a 10 day limit to get it fixed. 10 MEL items are not mission critical.

Its more a fault tolerance issue than anything else. But you definitely don't want things to throw a wobbly at 50ft. They have various failure modes Fail passive, fail operational, failed. But these rely on a complete failure of one unit to down grade to a single data source. To my knowledge the problem is a data quality issue and no way of determining which one is correct.

The FCC has only authorized the C-band use for 5G up to 3.95GHz. The radars start at 4.2GHz. It's quite astonishing that they're so terrible they apparently can't work right with a 200MHz guard band. That's utterly atrocious filter performance, I'm surprised the FAA authorized such dodgy systems in the first place.

:D you have to remember that some of the rad alts are 1960's. And certified to 1960's standards.

They are certified and if they haven't changed them since they won't be recertified to modern standards.

The FAA though is throwing the teddy out the pram though and are banning even CAT 1 and RNP approaches which you can't autoland off and rad alt previously could be completely offline and you could still do them.

right a bit of googling

Apparently the collins ALT-50 rad alt is the main stay of rad-alts more than 15 years old. Which is a colossal fleet bracket in the USA.

After that date then they use the collins ALT 1000-4000 series mostly. The biz jets tend to use Honeywell but as the bulk of the domestic fleet is the issue I stopped there. 737 Ng uses Collins alt 50.

All the manuals are pay to view but there is coming up a few things dating about 1975. They won't have had any certification work done on them since because there is no update to the installation paperwork and approval from the FAA in the doc logs.

They can change them but that requires a TSO and will be over 150k per aircraft for a single and don't have a clue how much it would be for a dual installation plus TSO for Boeing. Wouldn't surprise me though if its over half a million per airframe.

I don't think Airbus use Collins. But the FAA won't want to say its only a collins issue which mainly effects Boeing so they are banning the approaches not the hardware.

I have a suspicion there is a FCC V FAA empire war going on and FAA banning approaches is hoping that the politicians over ride the FCC.

BBB

A lot on that list.

BBB?

There is not a lot of info on this crap to pilots. We are deemed safe in euro land but my mates are getting utterly nonsense from authorities

Not so much direct interference, but a high vulnurability must exist between various low orbit technologies, GPS, Earth imaging, remote monitoring, space comms applications, space tourism and other developing low orbit technologies. The space junk from all of them is getting dangerous. It's only a matter of time before junk from one impacts another.
https://www.aljazeera.com/economy/2021/12/29/bbspa...

Link
White paper on 5G interference with radio altimeter,

Is it a problem with the base stations or with the rad alts?

To my uneducated eye it doesn't look as if they can co exist.

It's the radio altimeters by my reading, it appears under some scenarios the 5G emissions can exceed the IOAC mandatory 6db interference safety margins.

It seems to follow my perception of the history and I really can't see them doing anything about changing the Rad Alts medium term ie next 10 years never mind by the time 5G goes live.

That IACO band has been defined and protected since I was in nappies.

WiFi 6 GzHz
https://www.theverge.com/2021/12/28/22857852/6ghz-...

Well it appears that the FAA is going to ban all ILS approaches and RNP approaches at 46 city's next week.

Which will mean basically anything less than 400ft cloud base and nothing is going to land. Most of the VOR were taken out of action years ago along with NDB's

And ambulance flight as well are going to be grounded.

Quote (faa)

Example IAP NOTAM against impacted approaches (SA CAT I / II, CAT II, III, or RNP AR):BDL IAP BRADLEY INTL, WINDSOR LOCKS, CT. ILS RWY 06 (SA CAT I AND SA CAT II), AMDT 13A… ILS RWY 06 (CAT II AND CAT III), AMDT 38A… RNAV (RNP) Z RWY 06, AMDT 1… RNAV (RNP) Z RWY 24, AMDT 1… PROCEDURE NOT AUTHORIZED EXC FOR ACFT USING APPROVED ALTERNATIVE METHODS OF COMPLIANCE DUE TO 5G C- BAND INTERFERENCE PLUS SEE AIRWORTHINESS DIRECTIVE 2021-23-12

METAR KIAD 310852Z 00000KT 7SM OVC007 11/10 A2992 RMK AO2 SLP133 T01060100 50000

Here is a site which will decode the above. And you can have a look at your local airport. Purple seems to mean under the ban aircraft couldn't land.

https://metar-taf.com/KIAD

If you click on the notams tab it will tell you the current "rules" at the airport and if the FAA bans the approaches.

if your interested here is Dulles approach plates. Have a look at the cat C minimas

http://www.airnav.com/airport/KIAD

Just had a bit of a google and it appears that they are going to turn off the glide slopes and SBAS. So they can't just ignore it. The airports will be turning the hardware off.

Which means they should be able to get down to 300 ft on a LOC approach and 250 off a LNAV/VNAV.

Were as before they were 50ft for a CAT 3A and 0 for a CAT3B.

From the white paper, 5G user equipment on the ground not a problem, 5g user equipment onboard cat 2 and cat 3 aircraft pose a significant risk of harmful interference to the radar altimeters used on these aircraft, 5G base stations present a risk of harmful interference to radar altimeters across all aircraft types, with far-reaching consequences and impacts to aviation operations.

Seems the FAA has asked for a 2 week extension and is trying to sort out a compromise for 27 airports.

The telecoms providers are saying its not our problem you allow aircraft to fly with old antiquated hardware we shouldn't have to change things for that.

FCC is just saying we can't see a problem and we want the cash for the blocks.

There is also miss direction with "47 countries are using it no problems already" but they are all 3.4 to 3.8 block. Round me its being run at 3.5 and we had zero issues last night with doing CAT II and autoland approaches.

Quote (BBC)

The letter cited research by trade group Airlines for America which found that if the Federal Aviation Administration's (FAA) 5G rules had been in effect in 2019, about 345,000 passenger flights and 5,400 cargo flights would have faced delays, diversions or cancellations

AT&T, Verizon Refuse FAA Request to Delay 5G Launch
Link

Wonder what the French restrictions are.

https://www.4gltemall.com/blog/tag/5g-frequency-ba...

It only seems that USA and Japan have this issue. Everyone else has stuck with the ICAO protected zone even Russia.

It will cost more than they got for the 5G licenses to upgrade the USA aircraft domestic fleet of commercial carriers never mind the rest.

The restrictions on the medical and police heli ops will create a storm to boot.

And then there will be national security issues around military airfields not being able to operate. I am pretty sure the military gear will have the same Rad alts although they won't be linked into the other systems in the same way.

Found some details and response to the FAA and DOT

https://www.politico.com/f/?id=0000017e-1c36-dee4-...

They have is way wrong about helicopters though, they definitely do need an approach and departure sector just a different shape to aircraft.


Although there doesn't seem to be anything over 3.8 to date or even about to be turned on. And as they say the rest of us are operating fine with a 400 block split.

Has there actually been reported incidences of interference? Or is it all supposition, based on supposed noise margins?

TTFN (ta ta for now)
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I haven't seen anything with onboard 5G handsets or anything else.

And there must be a load traveling around Europe switched on. And a fair few of them controlled by crew.

I am 99% sure that the 4G LTE network in most of Europe has 3.8 Ghz as its top limit currently, and has done since it came out. Not a clue what the difference in risk is between 4G and 5G.

We used to have issues years ago when they used radio isotopes in the hold fire and smoke detectors with GSM phones. If they were left on in baggage they sometimes used to trigger them. But I haven't flown anything in decades which had one of them fitted.

Could it be a cat fight between two federal agency's for supremacy over that 3.8 to 4.8 range?

I was looking more for instances of interference with the radar altimeters. My recollection is that the 1980s' timeframe altimeters were a bit dodgy w.r.t. penetration of moderate foliage, because NASA once funded us to provide a laser altimeter to supplement their radar altimeter

TTFN (ta ta for now)
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I think that's when they went away from pulse .
They have pretty strict approach zones out to 6 miles I think. Which are surveyed to death and also controlled what goes in them. There are quite a few airports that only one end of a runway is able to take a low minima approach because of tertian issues.

They tend not to have crops in them just grass cut to special length to discourage birds.

There are plenty of accidents of radar alts failure which has resulted in fatal crashes.

The Turkish in Amsterdam had the active one started reading minus numbers at 1000ft and the plane went into retard mode and took the power back to idle. Pilots didn't spot it and a heap of alarms were in landing mode so they stalled and crashed.

https://catsr.vse.gmu.edu/SYST460/TA1951_AccidentR...

Here is the accident report on it.

I am posting from my phone but seem to remember the Dutch were quite though with it and there is quite a bit of back ground on how the rad alt links in with the 737-800 Ng systems.

Which I suspect is one of the reasons why the FAA are so twitchy about this. They have over 10 000 737's operating domestically in the USA and know full well what happens when the systems get false triggers.

I know Allister has posted the letter from Verizon, but here's the news item that reports on their and AT&T's responses:

AT&T, Verizon reject U.S. request to delay 5G wireless plans

Verizon and AT&T have rejected a request by the U.S. government to delay the rollout of next-generation wireless technology

https://abcnews.go.com/Technology/wireStory/att-ve...

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

I believe today they have agreed to a two week delay.

I suspect though that's linked to the current airline situation in the US. It's apparently utter chaos with crewing and weather.

Alistair... I found this comment a little disturbing:

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

OK, but the accident report seemingly indicates that the altimeter(s) in question were problematic, both on that specific aircraft as well as within that airline, with the intimation that this was a long-standing problem of the equipment provided by Boeing for nearly 20 years.

It also appears that like many other issues, redundant sensors don't appear to be properly integrated, and the report alludes to the fact that the left and right altimeters are completely separated systems and there's no oversight function that says, "Hey, my two sensors disagree; you need to do something, given that information." This was likewise the scenario in the MAX accidents, although this type of issue is likely not unique to Boeing.

Altimeters have been problematic for decades; my first introduction to that was a supposed problem with the F111's nap of the earth flight system that relied on the unreliable barometric altimeter that supposedly caused several incidents during the Vietnam War.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

Quote (IRstuff)

It also appears that like many other issues, redundant sensors don't appear to be properly integrated, and the report alludes to the fact that the left and right altimeters are completely separated systems and there's no oversight function

That's the balls of it all...

Its 1960 certificated in the case of the 737 and 1980's certificated in the case of the airbus grandfathered and stretched to death aircraft.

Which is a global issue in aviation unless they have to they won't and will use every trick in the book to only reuse old hardware.

There is historical issues which I mentioned above with the USA not wanting or refusing on principle to fit in with the rest of the international world. I also thing there is some metric imperial allocation bias in the mix as well with blocks.

The block works with metric, it doesn't work with imperial.

But the sort of hard place is they won't or can't change the hardware in the USA to modern in the next 5 years or for the cost of the new avionics V price paid for the block. But the airlines and aviation won't pay for the block to keep the current hardware. They are more than happy to blackmail to politicians into giving it to them for free.

dik this is all linked to the max threads and the way things operate.

I have just done 4 days of 10 hours studying and 2 days ground school as part of my yearly tech refresher. Next week I have 2 days of 4 hours doing low viz and 1/3 tech emergency faults on the aircraft systems. I will get 2 take-offs on both engines 1 might be normal the other will be rejected the variable bit will be if the other is if the other pilot is still alive by the time we get off the ground. Its not a problem you want the pay you do the shit...

After the sim i have a 6 month break to drink coke zero in the cruise... but I am sure your didn't have any sympathy feelings anyway

Faa has released a counter argument against the telecoms letter

https://www.faa.gov/5g

...sounds like a vacation to me?

Just jokin'... you sound pretty busy at times.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

After the sim it will be easy enough until start of April then hopefully all hell will let loose with a good summer season.

And a good summer season means I can build my barn and put my new solar plant in October.

I actually feel quiet sorry for USA pilots, they normally get paid by the hour in the air. And they are going to get hammered by this political bun fight.

There is something funny going on which hasn't surfaced yet in the public domain.

Well FAA has issued 1400+ NOTAM's with restrictions.

https://aopa.org/news-and-media/all-news/2022/janu...

If you can and don't have to travel by air in the USA I would get home by the 18th or give it a couple of weeks after the 19th.

I and I really hope nothing crashes before this can be sorted out. Telecoms and FCC seem hell bent on forcing upgrading of all rad alts to fit with their plans.

I suspect that this is only a temporary solution:

Verizon, AT&T Delay 5G Rollout Near Airports After Warning Of ‘Catastrophic Disruption’

Major airlines had urged that “the vast majority of the traveling and shipping public will essentially be grounded" if 5G was rolled out as planned.

https://www.huffpost.com/entry/verizon-att-5g-dela...

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without