I find the following confusing:

Separately, the FAA on Tuesday published an airworthiness directive on the Boeing 777 and 747-8 airplanes that interference may affect multiple airplane systems using radio altimeter data. The directive does not prevent any operations at nearly all large U.S. airports. The FAA has approved alternative means of compliance for the airplanes.

Ref: https://www.reuters.com/business/aerosp ... 022-01-25/

Ok, we have a concern that is specific to 777 and 787, but it doesn't prevent operations at "nearly all" large US airports?

Edit: Thread attached to https://twitter.com/ByERussell/status/1 ... 4411471873 suggests that the result might be to not allow 787/777 to be dispatched to certain airports with 5G towers nearby, and to figure out which ones those are you need to dig through the forest of ADs that speak to limitations of individual airplane/altimeter combinations.

Here is the AD for the 747 and 777:

https://public-inspection.federalregist ... iling+list

Approaches and Landings in the Presence of Radio Altimeter 5G C-Band
Interference:

Dispatching or releasing to airports, and approaches or landings on runways, in U.S.
airspace in the presence of 5G C-Band wireless broadband interference as identified by
NOTAM is prohibited (NOTAMs will be issued to state the specific airports or
approaches where the radio altimeter is unreliable due to the presence of 5G C-Band
wireless broadband interference).

adipasqu wrote:

Here is the AD for the 747 and 777:

https://public-inspection.federalregist ... iling+list

Approaches and Landings in the Presence of Radio Altimeter 5G C-Band
Interference:

Dispatching or releasing to airports, and approaches or landings on runways, in U.S.
airspace in the presence of 5G C-Band wireless broadband interference as identified by
NOTAM is prohibited (NOTAMs will be issued to state the specific airports or
approaches where the radio altimeter is unreliable due to the presence of 5G C-Band
wireless broadband interference).

Rather misleading if that is all you are going to share. Boeing and Aircus received AMOC approval last week for multiple RA models including those utilized on the B777 family, B748 family



(3) AMOCs approved for AD 2021-23-12, Amendment 39-21810 (86 FR 69984, December 9, 2021) providing relief for specific radio altimeter installations are approved as AMOCs for the provisions of this AD.

Qantas744er wrote:

adipasqu wrote:

Here is the AD for the 747 and 777:

https://public-inspection.federalregist ... iling+list

Approaches and Landings in the Presence of Radio Altimeter 5G C-Band
Interference:

Dispatching or releasing to airports, and approaches or landings on runways, in U.S.
airspace in the presence of 5G C-Band wireless broadband interference as identified by
NOTAM is prohibited (NOTAMs will be issued to state the specific airports or
approaches where the radio altimeter is unreliable due to the presence of 5G C-Band
wireless broadband interference).

Rather misleading if that is all you are going to share. Boeing and Aircus received AMOC approval last week for multiple RA models including those utilized on the B777 family, B748 family



(3) AMOCs approved for AD 2021-23-12, Amendment 39-21810 (86 FR 69984, December 9, 2021) providing relief for specific radio altimeter installations are approved as AMOCs for the provisions of this AD.

Since this is a later document - effective 1/27 - you may either say that FAA is misleading, or AMOC is not a blanket one.

Qantas744er wrote:

Rather misleading if that is all you are going to share. Boeing and Aircus received AMOC approval last week for multiple RA models including those utilized on the B777 family, B748 family



(3) AMOCs approved for AD 2021-23-12, Amendment 39-21810 (86 FR 69984, December 9, 2021) providing relief for specific radio altimeter installations are approved as AMOCs for the provisions of this AD.

I wasn't trying to be misleading, but since the AMOC's are only approved for a limited amount of time for now and we really don't know what they contain since the public can't access them, there wasn't any more context to quote directly pertaining to the AD that I linked to. The AMOC's have been discussed higher up in the thread.

DC 10s and 727s!! ;-)

M564038 wrote:

DC 10s and 727s!!

The MD-10 is on the list, so that seems to leave the 727 and the ERJ-135/140/145, I'm guessing?

adipasqu wrote:

Here is the AD for the 747 and 777:

https://public-inspection.federalregist ... iling+list

Not an AD but a request for comments on the proposed AD, right?

I'm getting the feeling that the FAA is going through painful contortions to try to keep everybody happy.

hivue wrote:

I'm getting the feeling that the FAA is going through painful contortions to try to keep everybody happy.

Is that a part of their job description?

Revelation wrote:

hivue wrote:

I'm getting the feeling that the FAA is going through painful contortions to try to keep everybody happy.

Is that a part of their job description?

I thought their job description is to keep everyone somewhat unhappy. That's when things are in balance.

Keep everyone happy, keep everybody unhappy. One of those odd constructions, opposites which mean about the same thing.

frmrCapCadet wrote:

Keep everyone happy, keep everybody unhappy. One of those odd constructions, opposites which mean about the same thing.

No, it's a long since lost art of compromise. Keep everyone somewhat unhappy, but make sure nobody is totally pissed off.

This will not end well...signed, Ayatollah So

When 5G rolled in out February, there was all this drama about airplanes crashing due to interference with radar altimeters. Haven’t heard or read anything since then. Even crazier is that the best 5G speeds that I have encountered has been at my home airport, SAT!

Some aircraft encountered problems but mysteriously none of them reported to the tower on arrival so...

Fred

Same thing that happened with Y2K doomsday predictions?

There are still issues. There are AMOCs out there for many runways for most aircraft types. There are fewer AMOCs for other aircraft types. For example, at one carrier the 223/320 has more AMOCs available than the E190, and the E190s can’t do RNP/cat2/3 approaches. There have been some anomalous issues associated with RA interference, such as spurious landing gear warnings when the aircraft is at say 4,000 feet with the gear up and the RA thinks it’s close to the ground due to the 5G interference.

EWRandMDW wrote:

Same thing that happened with Y2K doomsday predictions?

Somehow, I feel there's a large section of the a.net populous who may not get this reference.

EWRandMDW wrote:

Same thing that happened with Y2K doomsday predictions?

Y2K was mitigated through long and widespread awareness and efforts put into place to fix relevant programing codes in the few years in advance.
This.. is now being deal with with band aid fixes rolled out in two weeks when the news come that the 5G will actually be coming.

It's still out there but with mitigation in place. At my airline (757/767 operator) we have AMOCs for many of the airports we fly to, so normal operations continue. We do have a small subset of 767s that didn't receive FAA approval to use the AMOC airports. For those aircraft and at airports with AMOC, no CAT II/III, RNAV (RNP) or autoland.

flipdewaf wrote:

Some aircraft encountered problems but mysteriously none of them reported to the tower on arrival so...

Fred

The cell phone companies reported more precise location data for the towers to the FAA which allowed the FAA to reduce / remove a significant number of the restrictions. There are still a lot of issues out there, but most of them are performance limitations rather than prohibitions on operating. So a flight might be required to have some number of held seats based on the equipment type / airport combination.

Many aerospace companies are also developing / selling 5G filters that will protect the avionics that should "solve" the issue.

Here's a Phoenix NOTAM:

!PHX 01/073 PHX AD AP RDO ALTIMETER UNREL. AUTOLAND, HUD TO TOUCHDOWN, ENHANCED FLT VISION SYSTEMS TO TOUCHDOWN, HEL OPS REQUIRING RDO ALTIMETER DATA TO INCLUDE HOVER AUTOPILOT MODES AND CAT A/B/PERFORMANCE CLASS TKOF AND LDG NOT AUTHORIZED EXC FOR ACFT USING APPROVED ALTERNATIVE METHODS OF COMPLIANCE DUE TO 5G C-BAND INTERFERENCE PLUS SEE AIRWORTHINESS DIRECTIVES 2021-23-12, 2021-23-13 2201190501-2401190501

A lot of abbreviations, but the bottom line is procedures relying on radio altimeter are not authorized without alternate means of compliance.

The FAA requested better data from the providers to establish which airports had potential issues and which didn't. Then created mitigation plans for those that did.

It was basically a standoff between FCC and FAA. FCC insisted there was no issue and referred to FAA as "ankle-biters". But FAA holds the authority and also held firm on no compromise for safety. So providers had to demonstrate impact with data.

It's still a big thing, but for a lot of the planes it is affecting, it's only for CAT II/III operations since CAT I can rely on the baro altimeter.

Where I work we have a pretty long list of pireps about 5G interference. There are AMOCs for our aircraft that lets us fly CAT II ops into certain airport where towers are far enough away.

Long story short, I think you won't hear much about it until you get an airport with close towers and a heavy fog bank. That's where things get screwy.

What problem?

FreeFlight is offering new direct-replacement radar altimeters that use custom DSP (Digital Signal Processing) to filter out potential interference with 5G tower signals. As of late-March of this year they were in the final stages of receiving FAA approvals, which is expected to be granted soon.

https://www.ainonline.com/aviation-news ... altimeters

LDRA wrote:

What problem?

See all above…

Also, the FCC has decided that they're going to crack down on receivers that have insufficient resiliency to interference.

From: https://arstechnica.com/tech-policy/202 ... equencies/

In her statement before the vote, FCC Chairwoman Jessica Rosenworcel said, "Receivers that are not sufficiently resilient [to interference] can make it more difficult to introduce additional services in the same or adjacent airwaves [and thus] diminish the spectral environment and shut out new uses before they even begin."

While the FCC isn't clear if it has the ability to regulate reception (much of their legal basis focuses around regulating transmission), they're going to study what their options are. However, whatever steps they take toward making things clearer around reception are an improvement, that is the crux of what got us into this pickle. Also both the FAA and the FCC should've been clearer about this to begin with.

This does bring up a related question, I wonder if the FAA ever will clean up the interference that comes from radio altimeters still functioning when they're on the ground. It'd seem trivial to start to require new equipment to stop transmitting when there is weight on the wheels.

WASHINGTON, May 24 (Reuters) - The Federal Aviation Administration (FAA) wants airlines to complete retrofits of some airplane radio altimeters that could face interference from C-Band 5G wireless service by the end of 2022, according to a memo seen by Reuters.

The FAA memo said following a May 19 meeting of airlines, manufacturers and wireless carriers that "a collective goal was set to complete" retrofits on some Embraer and Airbus planes by the end of the year. Another meeting is set for June 3.

The memo sets out a series of dates for actions by the aviation industry, including by June 1 asking airlines to "commit to purchase filters and installation kits." The FAA plans to develop a "tool to track and report progress in real time" by May 31, the memo says.

The FAA and altimeter manufacturers divided the U.S. commercial passenger airline fleet into four groups based on their tolerance to interference. Group 1 has the poorest performing altimeters and primarily consists of Embraer regional jets, while Group 2 is largely Airbus A320s, officials said.

The FAA wants 1,760 planes in Groups "1 and 2" to be retrofitted this year. None have been completed yet.

The memo also says retrofits should be completed for 4,800 Group 3 planes in 2023.

https://finance.yahoo.com/news/1-u-faa- ... 34609.html

BEG2IAH wrote:

WASHINGTON, May 24 (Reuters) - The Federal Aviation Administration (FAA) wants airlines to complete retrofits of some airplane radio altimeters that could face interference from C-Band 5G wireless service by the end of 2022, according to a memo seen by Reuters.

The FAA memo said following a May 19 meeting of airlines, manufacturers and wireless carriers that "a collective goal was set to complete" retrofits on some Embraer and Airbus planes by the end of the year. Another meeting is set for June 3.

The memo sets out a series of dates for actions by the aviation industry, including by June 1 asking airlines to "commit to purchase filters and installation kits." The FAA plans to develop a "tool to track and report progress in real time" by May 31, the memo says.

The FAA and altimeter manufacturers divided the U.S. commercial passenger airline fleet into four groups based on their tolerance to interference. Group 1 has the poorest performing altimeters and primarily consists of Embraer regional jets, while Group 2 is largely Airbus A320s, officials said.

The FAA wants 1,760 planes in Groups "1 and 2" to be retrofitted this year. None have been completed yet.

The memo also says retrofits should be completed for 4,800 Group 3 planes in 2023.

https://finance.yahoo.com/news/1-u-faa- ... 34609.html

Its good to see the FAA taking assertive steps that should've been taken a few years ago.

I'm curious if the memo in question. I found an AD in the federal register for 707, 717, MD10, MD11, and MD80 airplanes, but nothing covering the Embrarers.

Which Embrarers are in Group 1? E140/145 or does it include E170/175/190s?

It looks like only Reuters had access to the memo. I searched for it but found nothing.