Shall We Drop Calls Or Airplanes? – Airlines And Wireless Companies Fight Over 5G Activation

Over the weekend several thousand flights in the U.S. were canceled:

The holiday travel nightmare worsened on New Year’s Day with more than 1,700 flights already cancelled for Sunday after more than 2,700 flights were cancelled Saturday due to poor weather conditions and the impacts of the Omicron variant of COVID-19.

The total number of cancelled flights since Christmas Eve now totals more than 14,000 – leaving thousands of Americans stranded over the holiday season.

Sunday’s travel chaos stems from key airline hubs including Chicago and Denver, as well as certain airlines which have been left with staff shortages due to COVID.

In an effort to combat the travel disruptions, airlines say they are taking steps to reduce cancellations.

United has offered to pay pilots three times or more of their usual wages for picking up open flights through mid-January. Southwest and others have also raised premium pay for some workers.

Many more flights may get canceled after January 5. It will have nothing to do with Covid though, or with bad weather. It will rather be because of a fight between two U.S. government agencies and the client industries they serve.

Two years agon the Federal Communications Commission (FCC) auctioned off radio frequencies between 3.7 to 3.98 gigahertz for the use in 5G networks. Major telecoms paid a total of $78 billion to get access to these. They will start using them on January 5.

This is of serious concern for the Federal Aviation Administration (FAA). Radar or radio altimeters in airplanes use frequencies between 4.2 and 4.4 gigahertz to determine the level of a plane above the ground. While they try to filter out neighboring frequencies to some degree they can be overwhelmed with false signals if these come at high power or were scatter around their frequencies through reflections.

Source: RTCA – bigger
The data from the altimeters is used in many automated alarms and systems especially in those that allow an airplane to operate in limited visual conditions during start and landing.

Source: FAA – bigger
The Aerospace Vehicle Systems Institute (AVSI) and the Radio Technical Commission for Aeronautics (RTCA) did independent evaluations and found that 5G base stations on the ground as well as 5G phones on a plane operating in the new frequencies may well overwhelm the radio altimeter filters and may lead to their misreporting of the distance to the ground.

When that happens the results can be deadly:

Turkish Airlines Flight 1951 was a passenger flight that crashed during landing at Amsterdam Schiphol Airport, the Netherlands, on 25 February 2009, resulting in the deaths of nine passengers and crew, including all three pilots.

The crash was caused primarily by the aircraft’s automated reaction, which was triggered by a faulty radio altimeter. This caused the autothrottle to decrease the engine power to idle during approach. The crew noticed this too late to take appropriate action to increase the thrust and recover the aircraft before it stalled and crashed.

Aircraft builders like Airbus and Boeing and altimeter producers like Garmin have asked the FCC to limit the use on the 5G frequencies near to the altimeter frequency ranges.

The FCC said no:

Aviation industry concerns were detailed by AVSI in an October 2019 study. Garmin cited AVSI’s research in an FCC filing this week, saying it showed altimeters “subjected to simulated 5G interference sources” output misleading data on a plane’s height above the ground, and this incorrect data “would not be able to be detected by downstream safety-critical systems that enable safe operation of aircraft in all weather conditions.”

The FCC found that AVSI’s report “does not demonstrate that harmful interference would likely result under reasonable scenarios (or even reasonably ‘foreseeable’ scenarios to use the parlance of AVSI).”

For the FCC to do something one must prove that something harmful is likely to happen under reasonable scenarios.

That is a good approach when the potential harm is a dropped phone call.

But it is a bad approach when a potential harm is a dropped passenger airplane.

Dropped airplanes are what the FAA is concerned about.

To get something FAA certified ones must prove that any malfunction and the related harm is extremely unlikely to appear.

Or as the FAA writes in a recent Airworthiness Directive:

The FAA determined that, at this time, no information has been presented that shows radio altimeters are not susceptible to interference caused by C-Band emissions permitted in the United States.

The FCC and FAA approaches to potential harm are extremely different. The FCC says “show me that it happens” while the FAA says “show me that it can not happen.”

Telecommunication lobbyists are engaged on the FCC side. The do not see the risk to the aviation industry. I find them to be quite dishonest:

Based on the modeling assumptions RTCA and AVSI are using, other systems, even in the absence of 5G, would be interfering with altimeters today. For example, Navy radar, such as the AN/SPN-43 radar, operates in mid-band frequencies at extremely high power with ground transmitters pointing at aircraft in geographical areas where U.S. planes operate. Such potential interference, however, has not been a problem in the real world.

The AN/SPN-43 is an S-band radar that operates between 3.5 and 3.7 gigahertz. That is much further away from the altimeter frequencies than the new 5G frequencies. There are also only few big ships with AN/SPN-43 radars around while there will be hundreds of powerful 5G base stations together with ten thousands of phones around airports and other densely populated areas. Will they and their beam steering antennas all work properly and keep to the right frequencies?

The FAA and the airline industry are unwilling to find out the hard way:

On December 23, 2021, the Federal Aviation Administration (FAA) issued Special Airworthiness Information Bulletin (SAIB) AIR-21-18, alerting operators to the potential for severe restrictions in flight operations to ensure safety.

On December 7, 2021, the FAA issued a statement on 5G that includes an Airworthiness Directive (AD) intended to cover all transport category aircraft. The AD requires the following Airplane Flight Manual (AFM) revision that prohibits the following operations in the presence of possible 5G interference:

Figure 1 to paragraph (g)—AFM Revision     (Required by AD 2021-23-12)

Radio Altimeter Flight Restrictions 

When operating in U.S. airspace, the following operations requiring radio altimeter are prohibited in the presence of 5G C-Band wireless broadband interference as identified by NOTAM (NOTAMs will be issued to state the specific airports where the radio altimeter is unreliable due to the presence of 5G C-Band wireless broadband interference): 

  • Instrument Landing System (ILS) Instrument Approach Procedures (IAP) SA CAT I, SA CAT II, CAT II, and CAT III 
  • Required Navigation Performance (RNP) Procedures with Authorization Required (AR), RNP AR IAP 
  • Automatic Landing operations 
  • Manual Flight Control Guidance System operations to landing/head-up display (HUD) to touchdown operation 
  • Use of Enhanced Flight Vision System (EFVS) to touchdown under 14 CFR 91.176(a)

It is further anticipated that, depending on the aircraft, the FAA may restrict the use of other aircraft systems as well with additional ADs. The limitations imposed by the ADs protect operations by preventing the most critical hazards from occurring in the case of radar altimeter interference.

Since radar altimeter interference is location-specific, the AD restrictions will be “activated” by NOTAMs issued for specific geographic locations and times.

The FAA issued Safety Alert for Operators 21007 on 12/23/2021, which describes some of the other aircraft systems which may be affected by C-Band 5G interference on radar altimeters, and also contains examples of 5G interference NOTAMs.

Starting January 5 2022 the telecommunication providers will activate the new frequencies on their 5G base stations in 45 major cities. If there is even the slightest hint that these may interfere, as is expected, with any radio altimeter the FAA will block any night or restricted visibility traffic to and from the related airport.

Aviation lobbyists point to the potential harm:

For instance, if you are traveling I-495 across the American Legion Bridge between Virginia and Maryland, a large cellular tower can be seen within a few hundred yards of the river.

When the river is visible, it is the preferred flight path to Reagan National Airport, and is also favored by rotorcraft including the president’s helicopter.

When the river is not visible, like at night or in a rainstorm, pilots still use the same path to the airport but must rely on their radio altimeters to maintain proper altitude.

Hundreds of commercial flights fly over that cellular tower during a typical week, but if it starts generating the power output planned for 5G signals, the airworthiness directive would kick in, severely restricting pilot options.

Planes might need to divert to other airports, however all of the nearby options have their own potential 5G problems, so there could be some lengthy detours for passengers.

If any major hub is affected the chaos will be gigantic with thousands of flights getting canceled each day. The airlines would lose billions.

But the concern is valid not only around airports. Emergency helicopters land about everywhere and also use radio altimeters.

Over the last weekend U.S. Transportation Secretary Pete Buttigieg and Federal Aviation Administration chief Steve Dickson had asked the telecommunication providers  to delay all 5G activations on the new frequencies. They were rebuffed:

U.S. Transportation Secretary Pete Buttigieg and Federal Aviation Administration chief Steve Dickson had asked AT&T CEO John Stankey and Verizon CEO Hans Vestberg late Friday for a commercial deployment delay of no more than two weeks.

The wireless companies in a joint letter on Sunday said they would not deploy 5G around airports for six months but rejected any broader limitation on using C-Band spectrum. They said the Transportation Department proposal would be “an irresponsible abdication of the operating control required to deploy world-class and globally competitive communications networks.”

The telcos point to France where 5G is restricted only around airports but not anywhere else. But 5G in France uses different frequencies and less powerful transmitters. Canada, which uses the same frequencies as the U.S., has restricted their use around airports.

When two big industries and their supporting government agencies collide with the potential of billions of losses on either side the fighting will get bitter.

The airlines now threaten to go to the courts to get an injunction against the use of the new frequencies.

I for one wish them good luck.