Radar Altimeters Interference mitigation?

Anyone at the FCC get fired?
 
Velocity173 said:
We (Part 135 rotor) just got an exemption last week.
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Will be interesting to see what happens in the GOM as all the IFR approaches require RA which in some aircraft is coupled to the approach. Hard to get the exemption when the 5G antenna is mounted on the same platform/rig you're shooting an approach to.
 
BladeSlap said:
Anyone at the FCC get fired?
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More like, Did anyone at the FCC do their job not to repurpose and auction adjacent spectrum for new services that by design were immediately understood to create obvious interference with established bands?
 
What happens if someone in the back fires up their 5G capable phone during the a CatIII approach? Is the signal from the phone enough to cause any issues?
 
Lots of opinions on this, but here's mine: This isn't on the FCC at all, it's on the FAA and RTCA. They're the ones that didn't do their jobs.

Here's the background:

Back in the 60's, the FAA and RTCA issued the TSO and supporting DOs for Radar Altimeters. The FCC had allocated a frequency band for the radar altimeters to operate in. The TSO restricted radar altimeter transmissions to the allocated band, but assumed that there would be no strong interfering signals withn 10% of the transmitting band - that's +/- 400MHz - which is huge. The FCC did NOT allocate that 800MHz wide swath of spectrum to radar altimeters, it's just the guys in the 60's that wrote the relevant TSOs and DOs assumed it would stay empty. There were two updates to those TSOs and DOs, the last being in the 80s - but with no significant change to the "don't worry about interference from this 800MHz swath, even though it's completely outside our control" idea. So the FAA and RTCA generated a crappy spec - one that worked when no-one was using adjacent bands, but would be vulnerable to interference if those adjacent bands (again, NOT allocated to radar altimeters) ever started being used.

In the meanwhile, avionics companies went off and built radar altimeters and certified them against the TSO, the FAA built some approaches around them, and radar altimeters started getting integrated into big jets' avionics - so a good deal of operations now depend on a functioning radar altimeter.

Then the FCC auctions off some of those bands that are OUTSIDE the frequency allocation for radar altimeters, but inside the imaginary 10% "you don't have to worry about interference from these frequencies" range, that the FAA and the RTCA just MADE UP 50-60 years ago. So now, a mess. There may be some radar altimeters that outperform the TSO and will work fine with 5G in its band. A filter in the radar altimeter can solve the problem too. But the system will move at glacial speeds to address those (new TSO? recertification? Bring money. And time.) That said, this glacial system has produced the world's safest commercial air transportation system.

Hence my view: This is completely on the FAA and RTCA. They wrote a crappy spec in the 60's, had more than 5 DECADES to fix it, and didn't, so they tripped over their own shoelaces. The FAA was NOT allocated this "super guard band", they just assumed it. It's not the FCC's job to work around crappy specs of other agencies.

YMMV,

--Tony
 
TxJim said:
More like, Did anyone at the FCC do their job not to repurpose and auction adjacent spectrum for new services that by design were immediately understood to create obvious interference with established bands?
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In the private sector that type of screw up costs you your job, and probably would make you radioactive in your industry.
 
TonyG said:
Lots of opinions on this, but here's mine: This isn't on the FCC at all, it's on the FAA and RTCA. They're the ones that didn't do their jobs.

Here's the background:

Back in the 60's, the FAA and RTCA issued the TSO and supporting DOs for Radar Altimeters. The FCC had allocated a frequency band for the radar altimeters to operate in. The TSO restricted radar altimeter transmissions to the allocated band, but assumed that there would be no strong interfering signals withn 10% of the transmitting band - that's +/- 400MHz - which is huge. The FCC did NOT allocate that 800MHz wide swath of spectrum to radar altimeters, it's just the guys in the 60's that wrote the relevant TSOs and DOs assumed it would stay empty. There were two updates to those TSOs and DOs, the last being in the 80s - but with no significant change to the "don't worry about interference from this 800MHz swath, even though it's completely outside our control" idea. So the FAA and RTCA generated a crappy spec - one that worked when no-one was using adjacent bands, but would be vulnerable to interference if those adjacent bands (again, NOT allocated to radar altimeters) ever started being used.

In the meanwhile, avionics companies went off and built radar altimeters and certified them against the TSO, the FAA built some approaches around them, and radar altimeters started getting integrated into big jets' avionics - so a good deal of operations now depend on a functioning radar altimeter.

Then the FCC auctions off some of those bands that are OUTSIDE the frequency allocation for radar altimeters, but inside the imaginary 10% "you don't have to worry about interference from these frequencies" range, that the FAA and the RTCA just MADE UP 50-60 years ago. So now, a mess. There may be some radar altimeters that outperform the TSO and will work fine with 5G in its band. A filter in the radar altimeter can solve the problem too. But the system will move at glacial speeds to address those (new TSO? recertification? Bring money. And time.) That said, this glacial system has produced the world's safest commercial air transportation system.

Hence my view: This is completely on the FAA and RTCA. They wrote a crappy spec in the 60's, had more than 5 DECADES to fix it, and didn't, so they tripped over their own shoelaces. The FAA was NOT allocated this "super guard band", they just assumed it. It's not the FCC's job to work around crappy specs of other agencies.

YMMV,

--Tony
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That filter should be paid for out of the pension funds of the FAA and FCC
 
donjohnston said:
What happens if someone in the back fires up their 5G capable phone during the a CatIII approach? Is the signal from the phone enough to cause any issues?
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I don't think so, but I doubt it's been tested sufficiently to know to an acceptable level of certainty. That's why all phones are supposed to be in Airplane Mode from block-out to landing.

The 5G phone won't transmit on the 5G channels until it has established a connection, on the data channel, with a cell site that has assigned it a 5G channel.
 
TonyG said:
Hence my view: This is completely on the FAA and RTCA. They wrote a crappy spec in the 60's, had more than 5 DECADES to fix it, and didn't, so they tripped over their own shoelaces.
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The solution is to increase the budget for the FAA, they will argue, I’m sure. Hire some shoe-lace watchers, maybe.
 
NoHeat said:
The solution is to increase the budget for the FAA, they will argue, I’m sure. Hire some shoe-lace watchers, maybe.
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The solution is to fire every person who didn’t act and make examples out of them, make them unemployable and make them spend every dime they have to defend themselves in a court that already made its mind up, that’s what the FAA would do if it was a airmen or operator who messed up.

You don’t reward idiots, so get rid of them and hire good talent.
 
TonyG said:
Lots of opinions on this, but here's mine: This isn't on the FCC at all, it's on the FAA and RTCA. They're the ones that didn't do their jobs.
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I had read that the FCC was also partially to blame, by allowing 2x the transmitter power and allowing the antennas to be oriented vertically, unlike the EU which required they be angled down. And the NSTC for not getting the Executive branch to mediate the dispute before the implementation date.. Still, any way you slice it, it was a 31-flavors-of-f*ckup situation.
 
In one of the aircraft I fly the RA is tied to autothrottle behavior, particularly the trigger to go to flight idle at 100 ft. AGL on approach. It's a big problem. Very curious to see how it will be ultimately solved or at least mitigated to acceptable risk levels.
 
Large organizations run by people that don't listen to the smart people that work for them. Job promotion skills should not be confused with trade skills.
 
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