FAA Wants US Airlines To Retrofit, Replace Radio Altimeters

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Bill-Higdon

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IMHO the cell companies & their equipment providers should pay for this
 

Vigilant1

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IMHO the cell companies & their equipment providers should pay for this
Agree, it seems that somebody else should be paying. Also, I'm pretty sure "US airlines" aren't the only planes affected. Other planes registered in the US have radio altimeters that could be affected, and foreign airlines operating in the US.
Obviously, this is something the FAA and FCC should have worked out before the frequencies were sold.
 

proppastie

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they did have it worked out......they just made a mistake (or lied)...... in the end all of us will pay for this mistake and the government regulators, engineers, management, and politicians will not be penalized in any way.......
 

Vigilant1

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they did have it worked out......they just made a mistake (or lied)...... in the end all of us will pay for this mistake and the government regulators, engineers, management, and politicians will not be penalized in any way.......
IMO, "Worked out" = Figure out if there is a problem, find the best solution, implement the solution (including paying for it). So, IMO, it wasn't "worked out." It was kicked down the road.
 

TFF

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5G is good. We can prosper. It made a monkey of the requirement that all PT 135 helicopters had to be equipped in 2019. Safety says Congress, because someone whispered that in their ear. Safety is good. Oh, we required something that we have to legally ignore. Doesn’t look good. But someone is making money on it and that’s all that really matters.
 

Vigilant1

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SpruceForest

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Again, way more complex than who should pay whom. Who is it we're going to tax to have the government cut a check, as we already know that the telecomm can throw far more legal shade than can aviation? And the answer is that - much like other mandates we may see as unjust or misguided - we have to suck it up and move on.

Radalt drives a fair number of safety-related systems aboard modern air transport aircraft, as well as Class A TAWS systems (air transport/mid and large corp jet) and is an option in Class B TAWS (corp/business/GA aircraft), so making sure the RADALT had adequate filtering exclude any interference that would degrade/disrupt/deny services is important.

Channel allocation for radar altimeters was done way before digital broadcast was a thing, and as any RF engineer knows, the guard bands - the unused bandwidth between adjacent channels to avoid interference - is necessarily wider for adjacent digital and analog waveforms than for digital to digital or analog to analog at comms and radalt frequencies. Tens of (perhaps hundreds with inflation o_O) billions of dollars of revenue space for telecomm services exists adjacent to (in the US, 3.70-3.98 GHz) the 4.3 GHz +/- 0.1 GHz center channel RADALT frequency (total allocated bandwidth from 4.2-4.4 GHz).

While I suspect the filtering on 5G transmitters on the upper side of the 3.70-3.98 GHz band will likely obviate any potential for interference with recent TSO-compliant digital FM-CW RADALTs, older analog systems may see both co-channel and out-of-band interference. That is the basis for the push to address the potential safety problem with additional filtering or unit replacement.

Further tech notes:

- The interference which might be generated by 5G emissions looks like noise to a RADALT which sees a portion of the 5G signal

- RADALT sees what looks like time-gated Gaussian noise, which - like any noise in the received signal - reduces the potential accuracy of measurement of radar derived altitude.

Anyway, it's a done deal and those aircraft requiring RADALT or TAWS A, plus any other RADALT users that will keep a RADALT installed and operational will have to either prove immunity to interference or address the problem with mods or swap.

Yes...it sucks.

Truth in advertising: I am NOT an RF engineer (aero with extensive avionics background)... if there are any here with 5G expertise as well as FM-CW and pulse RADALT design experience, I'd love to read your take on the matter.
 
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Bill-Higdon

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SpruceForest

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Thinking that - while you might have had your heart set on Cat 2/3 and RNP-AR approvals for the Piet, you may have to settle for VFR if that's your radar altimeter. ;)
 

Ava

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Thinking that - while you might have had your heart set on Cat 2/3 and RNP-AR approvals for the Piet, you may have to settle for VFR if that's your radar altimeter. ;)
Sport Pilots are limited to daylight VFR only.

Ole Piet, being NX registered, requires NO instrumentation at all... and unless equipped to standards laid out in § 91.205(b), it is likewise restricted to daylight VFR.

But, you know, that e-bay altimeter is completely unaffected by 5G, or 6G, or 7G...
radio.jpeg
:) And they have radios for sale too! :)
 

SpruceForest

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Sport Pilots are limited to daylight VFR only.

Ole Piet, being NX registered, requires NO instrumentation at all... and unless equipped to standards laid out in § 91.205(b), it is likewise restricted to daylight VFR.

But, you know, that e-bay altimeter is completely unaffected by 5G, or 6G, or 7G...
View attachment 127025
:) And they have radios for sale too! :)
Familiar with the Piet... I doubt anyone is doing RNP-AR with one, but you never know...
A shame what 6G - not to mention 7G - will do to the rest of the aircraft, though. I concur...stay away from those excessive g's :cool:
 
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N804RV

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...

IMHO the cell companies & their equipment providers should pay for this

Nope! This is a pure pissing contest between two government regulatory agencies. IMHO, the US Government is responsible.

And, if 10s of thousands of private aircraft owners had to pony up to meet the ADS-B "mandate" then, its not fair to bail out the commercial operators over this C-band circus.

 

Vigilant1

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The US government received $81 billion in license fees for this part of the spectrum. If owners of existing, perfectly compliant and legal, radar altimeters were forced to modify their equipment because the FCC and FAA didn't coordinate properly, it seems clear to me that the fix to truly make all that (already sold) frequency useable (filters, new RA equip, etc) should be paid for from that $81 billion.
 

Pops

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Sport Pilots are limited to daylight VFR only.

Ole Piet, being NX registered, requires NO instrumentation at all... and unless equipped to standards laid out in § 91.205(b), it is likewise restricted to daylight VFR.

But, you know, that e-bay altimeter is completely unaffected by 5G, or 6G, or 7G...
View attachment 127025
:) And they have radios for sale too! :)
Looks like the radio I built at 8 years old, except I used a toilet paper tube in making the coil.
 

trimtab

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This was already hashed out previously. Popular radar altimeters are trash...completely vulnerable. It takes minimal effort to make them digital and pretty much immune to the sorts of noise problems that are at issue, and a clever person can make a purely analog system to do the same thing.

But they didn't.

And the FAA and FCC both failed the American people ....again.

Bad engineering, bad standards setting, bad regulatory oversight. Predictable results.

If you want good results, you have to start with good people at the top.
 

N804RV

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The US government received $81 billion in license fees for this part of the spectrum. If owners of existing, perfectly compliant and legal, radar altimeters were forced to modify their equipment because the FCC and FAA didn't coordinate properly, it seems clear to me that the fix to truly make all that (already sold) frequency useable (filters, new RA equip, etc) should be paid for from that $81 billion.

It wouldn't work out that way though. It'd just be another bailout for the airlines on the "tax-payer's dime". That $81B is already spent.

With ADS-B, we were told that was the price of progress, ...well, there ya go!
 

SpruceForest

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Again, the analog FM-CW (civ) and pulse (mil) analog systems were designed and built decades before digital broadcast became a thing... it's like saying my Technics PPL turntable which I bought in 1977 for about $60 (and runs over $1K now on eBay) is trash because it does not have a remote, cannot make me a sandwich, will not respond to "Alexa... play Blue Nile's 'Hats'" or rub my sore feet after a day spent on the shop's concrete floor. None of those designers envisioned that there would be digital waveforms slamming adjacent channels at 4.3 GHz or indeed anyone interested in the bands either side of the allocated RADALT band.

As far as the FCC is concerned, they appear to have assumed pre-sale that certified systems would stay within the protected spectrum allocated by the ITU/FCC and that the 5G licensees would prevent at least the OOB stuff from occurring on the high end. The former may or may not be a good assumption, and the later likely is reasonable based on the testing results I've seen.

In a nutshell, the FCC's focus is not safety - it's regulating useable spectrum and feeding the organized appetite of government with the grist of power... which is to say converting resources held in trust into money to do 'good things' for 'stakeholders' and ensure 'equity' prevails. That later part of that last sentence should smell of three-day-old fish to any thinking person.

The FAA? Complain all you want, but they are solidly operating in their lane and have been doing what they can to mitigate the problem. Until the test results come in, expect them to err on the side of caution because that is what they are chartered to do.

As also mentioned previously, all of this sucks, but short of magicking a few trillion out of thin air - which we should all hope does NOT happen given the inevitable result of that action - don't expect any relief.
 
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