hivue wrote:

There is a relatively minimal downside and potentially a fantastic upside.

Not everyone would agree with this characterization...

wireamerica.org

ADent wrote:

Derico wrote:

Sorry if this has been asked, but how come in countries where 5G is already rolled out one hasn't heard of any issues? In fact I was in Korea last year for half the year and I don't remember hearing of such a storm around 5G and aviation.

If you go to the FAA site linked above they give several reasons as compared to France.
- France has bigger buffer zones, the US allows higher power, France requires antennas to be tilted downward.




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

The head of the FCC was on CNBC this morning ripping the airlines for not being more like France, where aviation and this frequency band have coexisted just fine for some time. So here's an obvious solution: How about the FCC telling Verizon and AT&T to re-deploy their C-band the same way France has? Can't be that hard to do, right? No harder than the airlines refitting their fleets with new equipment and procedures. Come to think of it, why wasn't the FCC on to this years ago rather than waiting till now to compare French operators to US airline/FAA slackers?

kalvado wrote:

RJs either wait their turn for review or are all problematic.

Many RJs aren't equipped for low-visibility (ILS CAT II / III), or their pilots aren't certified / trained to use it. It's a relatively small issue, operationally, to cancel or delay short haul flights for weather, while maintaining the equipment and the training requirements is costly. So they're pretty low on the airlines' and FAA's priority regarding this issue.

kalvado wrote:

Aaron747 wrote:

kalvado wrote:

What timeframe are you talking about? Looks like 2 years - abeit 2 covid years - were there for sure, probably more than that.

Perhaps you missed GalaxyFlyer’s earlier post that certifying new equipment was a minimum 4-6 year affair.

May I disbelieve that?
787 - a totally new plane - was supposed to go from start to finish in 5 years. it took 8 or so.
737MAX full computer system was fully redesigned in somewhat over a year.
So 4-6 years for a single filter? No.
Still 4 years? Fire everyone on property and hire some professionals.

Have you been involved in a certification program? It takes the FAA a year to approve an OpsSpec sometimes. It took the FAA a year to accept an already approved type certificate from another NAA, that by treaty they were supposed to take “on faith”. It took them a year to decide Martha Lunken’s emergency revocation. I’ve seen software uploads take over a year for release.

The MAX was one system, well understood, not remotely similar to changing an installed fleet of, perhaps 20,000 frames. Every type built in the last 25 years is affected. The 787 was well into design when the formal announcement was made and Boeing has years of carbon fiber experience in the B-2 program.

Every type with a RADALT will have to have all the interfaces checked, new code written, flight checked, a SB written, kits built and sent out. Service facilities trained and approved. It’s not going to be a simple filter, field installed. Collins, one supplier, won’t even answer the request for information.

Both Verizon’s and AT&T’s corporate jets are affected.

mxaxai wrote:

kalvado wrote:

RJs either wait their turn for review or are all problematic.

Many RJs aren't equipped for low-visibility (ILS CAT II / III), or their pilots aren't certified / trained to use it. It's a relatively small issue, operationally, to cancel or delay short haul flights for weather, while maintaining the equipment and the training requirements is costly. So they're pretty low on the airlines' and FAA's priority regarding this issue.

At least E145 and E175 are equipped with radar altimeters, though. I suspect every commercially flying plane is. They may have smaller role in operations compared to widebodies as a saving grace - subject to FAA approval.
Example: for 145 gear voice prompt depends on radalt - e.g. button Cancels LANDING GEAR voice msg. in case of Radio Altimeter loss only when flaps < 22º
As far as i understand, altitude callouts on landing are radalt as well. May be important for decision height. So it may be less critical, but there is an impact from faulty radalt.

GalaxyFlyer wrote:

kalvado wrote:

Aaron747 wrote:

Perhaps you missed GalaxyFlyer’s earlier post that certifying new equipment was a minimum 4-6 year affair.

May I disbelieve that?
787 - a totally new plane - was supposed to go from start to finish in 5 years. it took 8 or so.
737MAX full computer system was fully redesigned in somewhat over a year.
So 4-6 years for a single filter? No.
Still 4 years? Fire everyone on property and hire some professionals.

Have you been involved in a certification program? It takes the FAA a year to approve an OpsSpec sometimes. It took the FAA a year to accept an already approved type certificate from another NAA, that by treaty they were supposed to take “on faith”. It took them a year to decide Martha Lunken’s emergency revocation. I’ve seen software uploads take over a year for release.

The MAX was one system, well understood, not remotely similar to changing an installed fleet of, perhaps 20,000 frames. Every type built in the last 25 years is affected. The 787 was well into design when the formal announcement was made and Boeing has years of carbon fiber experience in the B-2 program.

Every type with a RADALT will have to have all the interfaces checked, new code written, flight checked, a SB written, kits built and sent out. Service facilities trained and approved. It’s not going to be a simple filter, field installed. Collins, one supplier, won’t even answer the request for information.

In other words, you're saying FAA doesn't do their job as they should. Avionics manufacturers are fat cats, not willing to move their ass. Who is surprised? Not me. Who is at fault? Of course someone else - those who work hard!
Think about it in such a way - wheels started to spin (and with enormous efficiency! On a government scale, of course) only once a gun of fleet groundings are pointed at heads.
Add some fines for unlicensed frequency usage, and things may start moving so fast, that FAA may overtake a sick snail!

GalaxyFlyer wrote:

The MAX was one system, well understood, not remotely similar to changing an installed fleet of, perhaps 20,000 frames. Every type built in the last 25 years is affected. The 787 was well into design when the formal announcement was made and Boeing has years of carbon fiber experience in the B-2 program.

Every type with a RADALT will have to have all the interfaces checked, new code written, flight checked, a SB written, kits built and sent out. Service facilities trained and approved. It’s not going to be a simple filter, field installed. Collins, one supplier, won’t even answer the request for information.

Both Verizon’s and AT&T’s corporate jets are affected.

On a more serious none. Looks like FAA cleared 2 radalt models. So this is not "every type". Someone actually cared to do things properly.
Why wasn't that analysis performed in 2021, or 2020? That may be the key question to the situation.

Yes, there is some work to be done. But - how long did it take to develop a fix for a pickle fork in NG? Months, if not weeks. Radalt is probably an easier fix, after all. And starting things moving a month earlier would mean completing the job a month earlier...

kalvado wrote:

mxaxai wrote:

kalvado wrote:

RJs either wait their turn for review or are all problematic.

Many RJs aren't equipped for low-visibility (ILS CAT II / III), or their pilots aren't certified / trained to use it. It's a relatively small issue, operationally, to cancel or delay short haul flights for weather, while maintaining the equipment and the training requirements is costly. So they're pretty low on the airlines' and FAA's priority regarding this issue.

At least E145 and E175 are equipped with radar altimeters, though. I suspect every commercially flying plane is. They may have smaller role in operations compared to widebodies as a saving grace - subject to FAA approval.
Example: for 145 gear voice prompt depends on radalt - e.g. button Cancels LANDING GEAR voice msg. in case of Radio Altimeter loss only when flaps < 22º
As far as i understand, altitude callouts on landing are radalt as well. May be important for decision height. So it may be less critical, but there is an impact from faulty radalt.

The Citation had Radar altimeters in 1980, every jet you see overhead now has, at least one, likely two. And modern avionics make the RADALT integral to every function—EGPWS, GPWS, TCAS, warning systems, auto flight and thrust, ground and flight spoilers, flight control laws for FBW, tail strike protection.

Vicenza wrote:

par13del wrote:

Since the flights canceled so far are by foreign airlines whose pilots are trained to let the computers do the bulk of the work for safety reasons, not sure where the skygods fit in.

Are you saying pilots on US airlines do the bulk of the work flying manually?

No, I was throwing shade back at the poster who said that the skygods in the USA should have no issue with the 5G implementation, the reality right now is that the foreign airlines who embrace automation more than the US pilots are the one's cancelling flights, most likely due to company policy. At present the situation is not yet in a position to bring up the issue about USA versus third world pilots, pot stirring may eventually come up but not yet.
https://edition.cnn.com/2022/01/18/busi ... index.html

BA has joined others in changing aircraft it sends to the USA it said today.

GalaxyFlyer wrote:

The Citation had Radar altimeters in 1980, every jet you see overhead now has, at least one, likely two. And modern avionics make the RADALT integral to every function—EGPWS, GPWS, TCAS, warning systems, auto flight and thrust, ground and flight spoilers, flight control laws for FBW, tail strike protection.

This integration of functions dependent on the radio altimeter as main sensor makes it all the more astonishing that such interference-prone sensors have been approved and installed. Have airplanes become too complex with various smart systems, so that such loopholes (and here I mean the failure to analyze the consequences of poor receiver selectivity) remain in the fault tolerance of these systems?

GalaxyFlyer wrote:

kalvado wrote:

787 - a totally new plane - was supposed to go from start to finish in 5 years. it took 8 or so.
737MAX full computer system was fully redesigned in somewhat over a year.
So 4-6 years for a single filter? No.
Still 4 years? Fire everyone on property and hire some professionals.

Have you been involved in a certification program? It takes the FAA a year to approve an OpsSpec sometimes. It took the FAA a year to accept an already approved type certificate from another NAA, that by treaty they were supposed to take “on faith”. It took them a year to decide Martha Lunken’s emergency revocation. I’ve seen software uploads take over a year for release.

The MAX was one system, well understood, not remotely similar to changing an installed fleet of, perhaps 20,000 frames. Every type built in the last 25 years is affected. The 787 was well into design when the formal announcement was made and Boeing has years of carbon fiber experience in the B-2 program.

Every type with a RADALT will have to have all the interfaces checked, new code written, flight checked, a SB written, kits built and sent out. Service facilities trained and approved. It’s not going to be a simple filter, field installed. Collins, one supplier, won’t even answer the request for information.

Both Verizon’s and AT&T’s corporate jets are affected.

My opinion is somewhere between these two. To be clear, this is just my opinion, but it is shaped by being somewhat knowledgeable in engineering, radio science and aviation.

I feel this crisis probably isn't going to be solved by the installation of an external filter. I feel it probably does involve upgrading the RADALTs themselves, but only their RF circuits, just so you do not end up needing to totally requalify all the downstream stuff. However to do this will be at least a 1-2 year job and even doing this will need an expedited path to delivery. I think in the end some set of restrictions will be put on 5G near airports for the 1-2 year period it'll take to get this work done.

I feel it's likely there is a lack of expertise in this area. No one has really needed to design this kind of equipment for a while. I attend conferences on wireless stuff and a lot of the young talent is working on radar applications for self driving cars, and a lot of the greybeards have retired. I suppose there is still expertise in the military space, but I'm not sure how transferable that is to the civilian space.

Revelation,

Probably closest to the fact on the future.

Snowfalcon wrote:

GalaxyFlyer wrote:

The Citation had Radar altimeters in 1980, every jet you see overhead now has, at least one, likely two. And modern avionics make the RADALT integral to every function—EGPWS, GPWS, TCAS, warning systems, auto flight and thrust, ground and flight spoilers, flight control laws for FBW, tail strike protection.

This integration of functions dependent on the radio altimeter as main sensor makes it all the more astonishing that such interference-prone sensors have been approved and installed. Have airplanes become too complex with various smart systems, so that such loopholes (and here I mean the failure to analyze the consequences of poor receiver selectivity) remain in the fault tolerance of these systems?

The type I fly, you can’t test the spoiler system if the tail of the plane is over a downslope. Why, will it requires a RADALT of less than 16’ to activate the spoilers, so if the tail-mounted antennas measure 20’, ground spoilers won’t arm for the test. These interfaces are what is driving the 777 and 787 problems. FBW control laws are dependent on height readings. Obviously, Airbus made a better vendor selection.

kalvado wrote:

On a more serious none. Looks like FAA cleared 2 radalt models.

What I found on FAA's site is:

FAA 5G Statement issued on January 16, 2022

Today, the FAA cleared an estimated 45 percent of the U.S. commercial fleet to perform low-visibility landings at many of the airports where 5G C-band will be deployed on Jan. 19.

The agency approved two radio altimeter models that are installed in a wide variety of Boeing and Airbus planes. This combination of aircraft and altimeter approval opens up runways at as many as 48 of the 88 airports most directly affected by 5G C-band interference.

As of Jan. 5, none of the 88 airports would have been available for landing during low-visibility conditions. The wireless companies agreed to create buffer zones for six months around airports where transmitters are in close proximity. They also agreed to delay deployment until Jan. 19 while the FAA reviewed new data detailing the location and power of wireless transmitters in all 46 U.S. markets where this service will be deployed.

Even with these new approvals, flights at some airports may still be affected. The FAA also continues to work with manufacturers to understand how radar altimeter data is used in other flight control systems. Passengers should check with their airlines if weather is forecast at a destination where 5G interference is possible.

The airplane models approved include some Boeing 737, 747, 757, 767, MD-10/-11 and Airbus A310, A319, A320, A321, A330 and A350 models. FAA expects to issue more approvals in the coming days.

So, they don't name the two RADALT models they approved or what process they used to approve them.

They also only address Boeing and Airbus models, no regional or business airplanes.

kalvado wrote:

mxaxai wrote:

kalvado wrote:

RJs either wait their turn for review or are all problematic.

Many RJs aren't equipped for low-visibility (ILS CAT II / III), or their pilots aren't certified / trained to use it. It's a relatively small issue, operationally, to cancel or delay short haul flights for weather, while maintaining the equipment and the training requirements is costly. So they're pretty low on the airlines' and FAA's priority regarding this issue.

At least E145 and E175 are equipped with radar altimeters, though. I suspect every commercially flying plane is. They may have smaller role in operations compared to widebodies as a saving grace - subject to FAA approval.
Example: for 145 gear voice prompt depends on radalt - e.g. button Cancels LANDING GEAR voice msg. in case of Radio Altimeter loss only when flaps < 22º
As far as i understand, altitude callouts on landing are radalt as well. May be important for decision height. So it may be less critical, but there is an impact from faulty radalt.

Correct, they are less critical, especially when they're just advisory (e. g. altitude callouts or warnings) and aren't directly coupled to the flight controls, which would be the case for autoland operations and many FBW systems. The radar altimeter is critical for the final approach and flare for autoland systems; worst case scenario is a late flare and a resulting hard touchdown with catastrophic damage.

In good visibility, there is enough reaction time (and available external references) to detect and mitigate a faulty altimeter. You'd be flying manually anyways. So you move from a 'catastrophic' rating to perhaps 'minor' or 'major'. There's still some safety effect, but loss of life is not expected. The probability of a 5G-related altimeter failure is low enough to satisfy these relaxed requirements.

Revelation wrote:

GalaxyFlyer wrote:

kalvado wrote:

787 - a totally new plane - was supposed to go from start to finish in 5 years. it took 8 or so.
737MAX full computer system was fully redesigned in somewhat over a year.
So 4-6 years for a single filter? No.
Still 4 years? Fire everyone on property and hire some professionals.

Have you been involved in a certification program? It takes the FAA a year to approve an OpsSpec sometimes. It took the FAA a year to accept an already approved type certificate from another NAA, that by treaty they were supposed to take “on faith”. It took them a year to decide Martha Lunken’s emergency revocation. I’ve seen software uploads take over a year for release.

The MAX was one system, well understood, not remotely similar to changing an installed fleet of, perhaps 20,000 frames. Every type built in the last 25 years is affected. The 787 was well into design when the formal announcement was made and Boeing has years of carbon fiber experience in the B-2 program.

Every type with a RADALT will have to have all the interfaces checked, new code written, flight checked, a SB written, kits built and sent out. Service facilities trained and approved. It’s not going to be a simple filter, field installed. Collins, one supplier, won’t even answer the request for information.

Both Verizon’s and AT&T’s corporate jets are affected.

My opinion is somewhere between these two. To be clear, this is just my opinion, but it is shaped by being somewhat knowledgeable in engineering, radio science and aviation.

I feel this crisis probably isn't going to be solved by the installation of an external filter. I feel it probably does involve upgrading the RADALTs themselves, but only their RF circuits, just so you do not end up needing to totally requalify all the downstream stuff. However to do this will be at least a 1-2 year job and even doing this will need an expedited path to delivery. I think in the end some set of restrictions will be put on 5G near airports for the 1-2 year period it'll take to get this work done.

I feel it's likely there is a lack of expertise in this area. No one has really needed to design this kind of equipment for a while. I attend conferences on wireless stuff and a lot of the young talent is working on radar applications for self driving cars, and a lot of the greybeards have retired. I suppose there is still expertise in the military space, but I'm not sure how transferable that is to the civilian space.

just in case - let me show you the scope of work from my semi-educated RF understanding.
This is a commercially available filter for similar frequency range. Not exactly what altimeters need, but a good idea of how things look:
https://www.pasternack.com/8-section-ba ... 742-p.aspx
Price is $500 or so. Add another zero or two for certification costs.
Yes, this is not a drop-in part; there will be redesign and tests. Yet, we're talking about adding a finger-sized component with 2 connectors. Sounds like an overnight maintenance job...

Revelation wrote:

So, they don't name the two RADALT models they approved or what process they used to approve them.

They also only address Boeing and Airbus models, no regional or business airplanes.

One of the models is most likely the Rockwell-Collins LRA-2100, which is the default on the A350 but has been fitted to other models (A320, A330) as well.

Revelation wrote:

I feel it's likely there is a lack of expertise in this area.

All due respect for your longtime contribution to this board, but this is what was called in Jerry's day a "copeout"

There is no lack of expertise in either Telecom or Aviation in this area. There is a lack of backbone to say enough is enough, we're prioritizing the safety of our civil aviation industry over your profits!

kalvado wrote:

just in case - let me show you the scope of work from my semi-educated RF understanding.
This is a commercially available filter for similar frequency range. Not exactly what altimeters need, but a good idea of how things look:
https://www.pasternack.com/8-section-ba ... 742-p.aspx
Price is $500 or so. Add another zero or two for certification costs.
Yes, this is not a drop-in part; there will be redesign and tests. Yet, we're talking about adding a finger-sized component with 2 connectors. Sounds like an overnight maintenance job...

The concept seems right yet I think the filter would need to be included inside the RADALT enclosure to ensure proper RF shielding and mechanical stability. There may or may not be room for that. Aircraft electronics bays are crowded places and there are lots of other devices that radiate nearby so shielding is a big concern. Also, adding a filter creates an insertion loss which will cause some performance degradation, so amplification may be needed to compensate for the filter. Designing anything to work at 4GHz comes with its challenges. Insertion losses and parasitic oscillations are real challenges. Radar works by measuring time differences so any delay the new elements create needs to be factored into the altitude determination.

Overall, It could become an overnight job, but I think it'd be more of swapping out the old radalt for an upgraded unit, once the suitable upgrades are designed, manufactured and tested. Getting to the point of such upgrades being available could be an uncomfortably long time.

mxaxai wrote:

Revelation wrote:

So, they don't name the two RADALT models they approved or what process they used to approve them.

They also only address Boeing and Airbus models, no regional or business airplanes.

One of the models is most likely the Rockwell-Collins LRA-2100, which is the default on the A350 but has been fitted to other models (A320, A330) as well.

Interesting, also https://www.collinsaerospace.com/-/medi ... 0e0dbf3540 is the link for the data sheet.

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

FAA clears 777 now.

Revelation wrote:

kalvado wrote:

just in case - let me show you the scope of work from my semi-educated RF understanding.
This is a commercially available filter for similar frequency range. Not exactly what altimeters need, but a good idea of how things look:
https://www.pasternack.com/8-section-ba ... 742-p.aspx
Price is $500 or so. Add another zero or two for certification costs.
Yes, this is not a drop-in part; there will be redesign and tests. Yet, we're talking about adding a finger-sized component with 2 connectors. Sounds like an overnight maintenance job...

The concept seems right yet I think the filter would need to be included inside the RADALT enclosure to ensure proper RF shielding and mechanical stability. There may or may not be room for that. Aircraft electronics bays are crowded places and there are lots of other devices that radiate nearby so shielding is a big concern. Also, adding a filter creates an insertion loss which will cause some performance degradation, so amplification may be needed to compensate for the filter. Designing anything to work at 4GHz comes with its challenges. Insertion losses and parasitic oscillations are real challenges. Radar works by measuring time differences so any delay the new elements create needs to be factored into the altitude determination.

Overall, It could become an overnight job, but I think it'd be more of swapping out the old radalt for an upgraded unit, once the suitable upgrades are designed, manufactured and tested. Getting to the point of such upgrades being available could be an uncomfortably long time.

I specifically added a link to an actual filter. Less than 2 dB insertion loss for 8 sections. Probably a bit lower altitude to start measuring, but not by much.
And this thing is well shielded - if anything, connector (which already exist) may be the biggest leaky spot.
So, while I hear what you say, I don't quite believe in such approach being beyond the reach

ILikeTrains wrote:

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

FAA clears 777 now.

I think https://www.faa.gov/newsroom/faa-statements-5g spells it out better:

The FAA issued new approvals Wednesday that allow an estimated 62 percent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band.

The new safety buffer announced Tuesday around airports in the 5G deployment further expanded the number of airports available to planes with previously cleared altimeters to perform low-visibility landings. The FAA early Wednesday cleared another three altimeters.

Even with these approvals, flights at some airports may still be affected. The FAA also continues to work with manufacturers to understand how radar altimeter data is used in other flight control systems. Passengers should check with their airlines for latest flight schedules.

Airplane models with one of the five cleared altimeters include some Boeing 717, 737, 747, 757, 767, 777, MD-10/-11 and Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models.

Still no 787, and still no word on what process is being used to "clear" a RADALT.

US aviation industry must be happy, 62% of their aircraft just got cleared without them "getting off their asses". Think of how many $millions they saved by not rushing out and "fixing it". 62% of the problem just went away with them spending $0.

N212R wrote:

danman132x wrote:

What baffles me is this is an airline enthusiast website, but so many people are defending the telecoms.

As in many on-line forums, a good percentage of the posters are not independent but institutional mouthpieces. The disinformation and misdirection comes fast and furious in these heady days.

Big Telecom, like Big Pharma,cares not a whit for public health or safety. What's a few broken eggs in a hen house of profits?

Oh please. If you understand the engineering aspects of the situation at all, it's obvious that the radar altimeters in question were designed in an unsafe way (assuming frequencies not assigned to the service would forever be clear) that happened to be lucky up until now.

Safety is task #1, but in our society that turns everything into property, the only way to keep these bands clear would be for the airlines to buy the spectrum, and we all know they don't have the money for that.

Revelation wrote:

ILikeTrains wrote:

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

FAA clears 777 now.

I think https://www.faa.gov/newsroom/faa-statements-5g spells it out better:

The FAA issued new approvals Wednesday that allow an estimated 62 percent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band.

The new safety buffer announced Tuesday around airports in the 5G deployment further expanded the number of airports available to planes with previously cleared altimeters to perform low-visibility landings. The FAA early Wednesday cleared another three altimeters.

Even with these approvals, flights at some airports may still be affected. The FAA also continues to work with manufacturers to understand how radar altimeter data is used in other flight control systems. Passengers should check with their airlines for latest flight schedules.

Airplane models with one of the five cleared altimeters include some Boeing 717, 737, 747, 757, 767, 777, MD-10/-11 and Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models.

Still no 787, and still no word on what process is being used to "clear" a RADALT.

US aviation industry must be happy, 62% of their aircraft just got cleared without them "getting off their asses". Think of how many $millions they saved by not rushing out and "fixing it". 62% of the problem just went away with them spending $0.

So basically the FAA is making the RADALT manufacturers answer the questions raised about interference and take ownership of the handling of spurious and erroneous data.

For reference of the Aircraft and model R Altimeter and Airports / Runways approved, look into the following AMOC's.

720-22-1105A (Boeing)
720-22-1372 (Boeing)
720-22-1377A (Boeing)
720-22-1407A (Airbus)
720-22-1391 (Airbus)

slowrambler wrote:

it's obvious that the radar altimeters in question were designed in an unsafe way (assuming frequencies not assigned to the service would forever be clear) that happened to be lucky up until now.

The original designs (or rather, the certification requirements) were safe for the environment at the time. The services that had permission to use the adjacent frequency bands in the past had to adhere to certain upper limits in power output (and, if they needed high power transmitters like for satellite ground stations, would not get permission to do so in the vicinity of airports). It's a waste of money to design equipment for implausible scenarios.

The entire situation changed of course when 5G received spectrum that had previously been assigned to other uses. But it's not as if the spectrum had been sitting completely unused.

kalvado wrote:

So far, 777 and 787 seem to be confirmed as affected.
So much for modern.

Airplane models with one of the five cleared altimeters include some Boeing 717, 737, 747, 757, 767, 777, MD-10/-11 and Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models.

So half of your fanboy estimate just flew through the window...

mxaxai wrote:

Revelation wrote:

So, they don't name the two RADALT models they approved or what process they used to approve them.

They also only address Boeing and Airbus models, no regional or business airplanes.

One of the models is most likely the Rockwell-Collins LRA-2100, which is the default on the A350 but has been fitted to other models (A320, A330) as well.

A second approved model should be the Thales ERT 550 https://www.thalesgroup.com/en/communic ... l-aircraft , which is used on A380s. (I am not sure whether there was a different model to choose from on the A380).

mxaxai wrote:

slowrambler wrote:

it's obvious that the radar altimeters in question were designed in an unsafe way (assuming frequencies not assigned to the service would forever be clear) that happened to be lucky up until now.

The original designs (or rather, the certification requirements) were safe for the environment at the time. The services that had permission to use the adjacent frequency bands in the past had to adhere to certain upper limits in power output (and, if they needed high power transmitters like for satellite ground stations, would not get permission to do so in the vicinity of airports). It's a waste of money to design equipment for implausible scenarios.

The entire situation changed of course when 5G received spectrum that had previously been assigned to other uses. But it's not as if the spectrum had been sitting completely unused.

That is how problems happen, failing to account for implausible scenarios that could have been handled with a simple filter. There are other means of RF interference that can occur naturally. Occurrence rates would be certainly lower, but it can happen. How much effort you spend in accounting for those sorts of implausible situations is directly tied to how critical the equipment is.

Boeing12345 wrote:

For reference of the Aircraft and model R Altimeter and Airports / Runways approved, look into the following AMOC's.

720-22-1105A (Boeing)
720-22-1372 (Boeing)
720-22-1377A (Boeing)
720-22-1407A (Airbus)
720-22-1391 (Airbus)

Are these AMOCs public? If so, where can we find them?

a2b7 wrote:

mxaxai wrote:

Revelation wrote:

So, they don't name the two RADALT models they approved or what process they used to approve them.

They also only address Boeing and Airbus models, no regional or business airplanes.

One of the models is most likely the Rockwell-Collins LRA-2100, which is the default on the A350 but has been fitted to other models (A320, A330) as well.

A second approved model should be the Thales ERT 550 https://www.thalesgroup.com/en/communic ... l-aircraft , which is used on A380s. (I am not sure whether there was a different model to choose from on the A380).

On the Airbus Fleet only the Colin's LRA-2100 and Honeywell ALA-52B are approved. Still pending FAA approval for Airbus is Thales ERT-530/ -540, -550 and Collins LRA-700, - 900 and the ALT-4000.

BEG2IAH wrote:

kalvado wrote:

So far, 777 and 787 seem to be confirmed as affected.
So much for modern.

Airplane models with one of the five cleared altimeters include some Boeing 717, 737, 747, 757, 767, 777, MD-10/-11 and Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models.

So half of your fanboy estimate just flew through the window...

After a couple of canceled flights, its more like my belief in FAA professionalism flew out of the window. Good for telecom that they know how to apply some pressure!

Boeing12345 wrote:

a2b7 wrote:

mxaxai wrote:

One of the models is most likely the Rockwell-Collins LRA-2100, which is the default on the A350 but has been fitted to other models (A320, A330) as well.

A second approved model should be the Thales ERT 550 https://www.thalesgroup.com/en/communic ... l-aircraft , which is used on A380s. (I am not sure whether there was a different model to choose from on the A380).

On the Airbus Fleet only the Colin's LRA-2100 and Honeywell ALA-52B are approved. Still pending FAA approval for Airbus is Thales ERT-530/ -540, -550 and Collins LRA-700, - 900 and the ALT-4000.

Are there any specifically rejected models?

kalvado wrote:

Boeing12345 wrote:

a2b7 wrote:

A second approved model should be the Thales ERT 550 https://www.thalesgroup.com/en/communic ... l-aircraft , which is used on A380s. (I am not sure whether there was a different model to choose from on the A380).

On the Airbus Fleet only the Colin's LRA-2100 and Honeywell ALA-52B are approved. Still pending FAA approval for Airbus is Thales ERT-530/ -540, -550 and Collins LRA-700, - 900 and the ALT-4000.

Are there any specifically rejected models?

Not that I have seen, just that these are still pending approval by the FAA via AMOC's.

But there are other factors.
In addition to insertion loss, make up gain, and oscillation,potential RF issues within the unit, there are phase-shift, not everything is linear so you are talking testing and recertification. A steeper filter could be made by a high-schooler, but steeper filters means more noise and signal distortion. There might be software with very strict treshold values needing adjustments. I have no problem seeing how this could be far from clean cut, even though just making a steeper filter could be easy as pie.

kalvado wrote:

Revelation wrote:

kalvado wrote:

just in case - let me show you the scope of work from my semi-educated RF understanding.
This is a commercially available filter for similar frequency range. Not exactly what altimeters need, but a good idea of how things look:
https://www.pasternack.com/8-section-ba ... 742-p.aspx
Price is $500 or so. Add another zero or two for certification costs.
Yes, this is not a drop-in part; there will be redesign and tests. Yet, we're talking about adding a finger-sized component with 2 connectors. Sounds like an overnight maintenance job...

The concept seems right yet I think the filter would need to be included inside the RADALT enclosure to ensure proper RF shielding and mechanical stability. There may or may not be room for that. Aircraft electronics bays are crowded places and there are lots of other devices that radiate nearby so shielding is a big concern. Also, adding a filter creates an insertion loss which will cause some performance degradation, so amplification may be needed to compensate for the filter. Designing anything to work at 4GHz comes with its challenges. Insertion losses and parasitic oscillations are real challenges. Radar works by measuring time differences so any delay the new elements create needs to be factored into the altitude determination.

Overall, It could become an overnight job, but I think it'd be more of swapping out the old radalt for an upgraded unit, once the suitable upgrades are designed, manufactured and tested. Getting to the point of such upgrades being available could be an uncomfortably long time.

I specifically added a link to an actual filter. Less than 2 dB insertion loss for 8 sections. Probably a bit lower altitude to start measuring, but not by much.
And this thing is well shielded - if anything, connector (which already exist) may be the biggest leaky spot.
So, while I hear what you say, I don't quite believe in such approach being beyond the reach

M564038 wrote:

But there are other factors.
In addition to insertion loss, make up gain, and oscillation,potential RF issues within the unit, there are phase-shift, not everything is linear so you are talking testing and recertification. A steeper filter could be made by a high-schooler, but steeper filters means more noise and signal distortion. There might be software with very strict treshold values needing adjustments. I have no problem seeing how this could be far from clean cut, even though just making a steeper filter could be easy as pie.

kalvado wrote:

Revelation wrote:

The concept seems right yet I think the filter would need to be included inside the RADALT enclosure to ensure proper RF shielding and mechanical stability. There may or may not be room for that. Aircraft electronics bays are crowded places and there are lots of other devices that radiate nearby so shielding is a big concern. Also, adding a filter creates an insertion loss which will cause some performance degradation, so amplification may be needed to compensate for the filter. Designing anything to work at 4GHz comes with its challenges. Insertion losses and parasitic oscillations are real challenges. Radar works by measuring time differences so any delay the new elements create needs to be factored into the altitude determination.

Overall, It could become an overnight job, but I think it'd be more of swapping out the old radalt for an upgraded unit, once the suitable upgrades are designed, manufactured and tested. Getting to the point of such upgrades being available could be an uncomfortably long time.

I specifically added a link to an actual filter. Less than 2 dB insertion loss for 8 sections. Probably a bit lower altitude to start measuring, but not by much.
And this thing is well shielded - if anything, connector (which already exist) may be the biggest leaky spot.
So, while I hear what you say, I don't quite believe in such approach being beyond the reach

As far as I understand, this is about frequency sweep and measuring beat frequency, so there is a lot of tolerance on everything.

Well, EK's CEO Sir Tim Clark has some " hot sports opinions" about this mess

https://www.dailymail.co.uk/news/articl ... llout.html

Snowfalcon wrote:

GalaxyFlyer wrote:

The Citation had Radar altimeters in 1980, every jet you see overhead now has, at least one, likely two. And modern avionics make the RADALT integral to every function—EGPWS, GPWS, TCAS, warning systems, auto flight and thrust, ground and flight spoilers, flight control laws for FBW, tail strike protection.

This integration of functions dependent on the radio altimeter as main sensor makes it all the more astonishing that such interference-prone sensors have been approved and installed. Have airplanes become too complex with various smart systems, so that such loopholes (and here I mean the failure to analyze the consequences of poor receiver selectivity) remain in the fault tolerance of these systems?

This is what I was going to say. Clearly there is plenty of blame to pass around, but we've been building radios for nearly a century. We know how to tune specific frequencies. The fact that sloppy hardware was designed is just shoddy work. The fact that officially certified (you know, the thorough and laborious and paper-intensive work required to certify aircraft hardware) radio altimeters with shoddy hardware design got certified anyway by either FCC and/or FAA is also shoddy. And if it was known a few years ago that this would be a problem, then a bunch of organizations dropped the ball.

Airbus has applied for five AMOC with the FAA to cover those Radar Altimeters utilized on Airbus family aircraft.

Five have been approved, still pending FAA approval are

Collins LRA-700/LRA-900
A300-600/A310/A320Family/A330/A340 (all of which can also be fitted with the Thales ERT-530/ERT-540 for which a AMOC is already approved by the FAA)

Collins ALT-4000
A220 is also still awaiting AMOC approval.

No, I actually disagree. Using shallow filters when allowed is good design. We want shallow filters. Shallow filters are easy, safe, sturdy and distortion free.
However, there is some arrogance and assumption in making things so shallow that you de-facto are taking up more of the spectrum than you are supposed to. Someone must have made a deal at some point that didn’t quite translate through the decades.

Chemist wrote:

Snowfalcon wrote:

GalaxyFlyer wrote:

The Citation had Radar altimeters in 1980, every jet you see overhead now has, at least one, likely two. And modern avionics make the RADALT integral to every function—EGPWS, GPWS, TCAS, warning systems, auto flight and thrust, ground and flight spoilers, flight control laws for FBW, tail strike protection.

This integration of functions dependent on the radio altimeter as main sensor makes it all the more astonishing that such interference-prone sensors have been approved and installed. Have airplanes become too complex with various smart systems, so that such loopholes (and here I mean the failure to analyze the consequences of poor receiver selectivity) remain in the fault tolerance of these systems?

This is what I was going to say. Clearly there is plenty of blame to pass around, but we've been building radios for nearly a century. We know how to tune specific frequencies. The fact that sloppy hardware was designed is just shoddy work. The fact that officially certified (you know, the thorough and laborious and paper-intensive work required to certify aircraft hardware) radio altimeters with shoddy hardware design got certified anyway by either FCC and/or FAA is also shoddy. And if it was known a few years ago that this would be a problem, then a bunch of organizations dropped the ball.

Thales ERT-530 and -540 is now AMOC approved as well.

Chemist wrote:

This is what I was going to say. Clearly there is plenty of blame to pass around, but we've been building radios for nearly a century. We know how to tune specific frequencies. The fact that sloppy hardware was designed is just shoddy work. The fact that officially certified (you know, the thorough and laborious and paper-intensive work required to certify aircraft hardware) radio altimeters with shoddy hardware design got certified anyway by either FCC and/or FAA is also shoddy. And if it was known a few years ago that this would be a problem, then a bunch of organizations dropped the ball.

All that shoddiness and sloppiness that has allowed civilian airliners to safely navigate the world's skies for just as long, he sarcastically replied to an obvious attempt at scape-goating.

N212R wrote:

Chemist wrote:

This is what I was going to say. Clearly there is plenty of blame to pass around, but we've been building radios for nearly a century. We know how to tune specific frequencies. The fact that sloppy hardware was designed is just shoddy work. The fact that officially certified (you know, the thorough and laborious and paper-intensive work required to certify aircraft hardware) radio altimeters with shoddy hardware design got certified anyway by either FCC and/or FAA is also shoddy. And if it was known a few years ago that this would be a problem, then a bunch of organizations dropped the ball.

All that shoddiness and sloppiness that has allowed civilian airliners to safely navigate the world's skies for just as long, he sarcastically replied to an obvious attempt at scape-goating.

This allowed civilian airliners to safely navigate due to lack of occupants nearby
That's like driving on a great plain randomly disregarding traffic lane and land ownership, then complaining someone who buy a land and building a house out there for blocking your way, despite their house are build along the road supposed to be followed.

I see the fear mongering is in full swing by the airlines today. Even read Emirates CEO claiming they had no idea until this morning, sure, ok.

Long about the year 2000, similar thing happened in the AF, in fact most state aircraft. The ILS band is just below the FM Broadcast band and early ILS receivers could be interfered with by FM stations. The civilian world dealt with, governments monitored for interference, finally all ILS receivers were “FM Immune”; they could reject broadcast radio. All except the old stuff installed in many military aircraft where budget priorities meant updating the ILS receivers never got funded. Oops, the governments in Europe stopped the monitoring, the USAF planes suddenly had no way down in winter except finding PARs. Funded and fixed by spring.

c933103 wrote:

N212R wrote:

Chemist wrote:

This is what I was going to say. Clearly there is plenty of blame to pass around, but we've been building radios for nearly a century. We know how to tune specific frequencies. The fact that sloppy hardware was designed is just shoddy work. The fact that officially certified (you know, the thorough and laborious and paper-intensive work required to certify aircraft hardware) radio altimeters with shoddy hardware design got certified anyway by either FCC and/or FAA is also shoddy. And if it was known a few years ago that this would be a problem, then a bunch of organizations dropped the ball.

All that shoddiness and sloppiness that has allowed civilian airliners to safely navigate the world's skies for just as long, he sarcastically replied to an obvious attempt at scape-goating.

This allowed civilian airliners to safely navigate due to lack of occupants nearby
That's like driving on a great plain randomly disregarding traffic lane and land ownership, then complaining someone who buy a land and building a house out there for blocking your way, despite their house are build along the road supposed to be followed.

Yet somehow a bunch of other units don't seem to have this problem and still work fine.