Radio Altimeter Aircraft - A more immediate solution would be to make permanent the temporary limits that AT&T and Verizon have placed on their 5G networks near airports. Or the companies could reduce the strength of the 5G signals near airports, or redirect antennas in ways that limit or eliminate their impact on planes.
These options would probably make 5G networks less useful in those areas, and potentially not available for those who live within the buffer zones of certain airports. What about helicopters? The FAA allows air ambulance operators to continue using safety-enhancing night vision goggles in areas where the aircraft's radio altimeter could be unreliable due to 5G C-band interference as identified by NOTAMs.
Radio Altimeter Aircraft
Operators must comply with specific conditions and limitations. Similar to commercial aircraft, helicopters can perform day and night operations that do not require the use of a radio altimeter. What are radio altimeters? Radio altimeters provide highly accurate information about an aircraft's height above the ground.
The Safety Issue
Data from these radio altimeters informs other safety equipment on the plane, including navigation instruments, terrain awareness, and collision-avoidance systems. The FAA issued new approvals Thursday that allow an estimated 78 percent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band.
This now includes some regional jets. Airplane models with one of the 13 cleared altimeters include all Boeing 717, 737, 747, 757, 767, 777, 787, MD-10/-11; all Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models;
and some Embraer 170 and 190 regional jets. The FAA is working diligently to determine which altimeters are reliable and accurate where 5G is deployed in the United States. We anticipate some altimeters will be too susceptible to 5G interference.
To preserve safety, aircraft with those altimeters will be prohibited from performing low-visibility landings where 5G is deployed because the altimeter could provide inaccurate information. Passengers should check with their airlines for the latest flight schedules.
Why Weren’t These Concerns Addressed Earlier?
Safety is the core of our mission and this guides all of our decisions. The FAA thanks AT&T and Verizon for agreeing to a voluntary delay and for their proposed mitigations. We look forward to using the additional time and space to reduce flight disruptions associated with this 5G deployment.
In his Brookings Institution piece, Mr. Wheeler, the former F.C.C. chair, outlined three sources of potential funding: The government could spend some of the $82 billion it received from selling 5G frequencies to the wireless companies;
the wireless industry could be forced to pay additional fees for use of those frequencies; or the aviation industry could be forced to pay for the upgrades because it has long known that 5G was coming.
The FAA says 5G “may” cause interference. So how do you know there's a safety risk? Aviation in the U.S. is the safest in the world. That's because we rely on data to mitigate risk, and never assume that a piece of equipment or a given flight scenario is safe until this can be demonstrated.
What Are Aviation Safety Experts Worried About?
If there's the possibility of a risk to the flying public, we are obliged to restrict the relevant flight activity until we can prove it is safe. Any solution will have to be negotiated between the airlines and the F.A.A.
on one side and wireless companies and the F.C.C. on the other. But the two camps view the problem so differently that reaching agreement could be difficult, said Harold Feld, a senior vice president at Public Knowledge, a research and advocacy group that has received funding from AT&T and Verizon.
If an altimeter's waves don't bounce back because of 5G interference, or can't be distinguished from other nearby waves, the altimeter could give the wrong reading or not function at all, said Peter Lemme, a former Boeing engineer who spent 16 years
at the company designing safety systems that rely on altimeters. Key stakeholders in the aviation and wireless industries have identified a series of steps that will continue to protect commercial air travel from disruption by 5G C-band interference while also enabling Verizon and AT&T to enhance service around certain airports.
Questions And Answers
The main components of a radio altimeter system are the transmitter, the receiver and the display unit. The display is incorporated in the ADI displays of EFIS or flight director equipped aircraft, the instrument includes a decision height feature that allows the pilot to set the decision height indel bug on the face of the instrument.
When the pointer reaches the set height during a descent a visual and/or aural warning is activated. Safety is our mission, and it guides all of our decisions. In the United States, 5G services launched in 46 markets on January 19, using frequencies in a radio spectrum called the C-band.
These frequencies can be close to those used by radio altimeters, an important piece of safety equipment in aircraft. To make sure that this does not lead to hazardous interference, the FAA requires that radio altimeters are accurate and reliable.
The airline industry has been working on new standards for radio altimeters that would address the 5G interference and other issues. But those standards are not scheduled to be released until October and would apply only to new altimeters.
Disruption Risk To Aviation From G
The F.A.A. has approved five models of altimeters as 5G compliant in the past week, but the approvals are based on the combination of altimeter and plane model, and no altimeters have been approved for use in 787s.
Many airports are not currently affected by the new 5G deployment, even though they are not on this list. These include airports not in the 46 markets where the new service will be deployed and airports that do not currently have the ability to allow low-visibility landings.
The Federal Aviation Administration (FAA) issued an Airworthiness Directive (AD) revising the landing requirements for Boeing 737 MAX airplanes at airports where 5G interference could occur. Continued collaboration between the FAA and wireless companies has enabled the agency to clear an estimated 90 percent of the U.S.
commercial aircraft fleet, including the Boeing 737 MAX, for most low-visibility approaches in 5G deployment. This AD will not apply to landings at airports where the FAA determined the aircraft radio altimeters are safe and reliable in the 5G C-band environment.
Collaborative Work Underway To Reduce Delay Cancellation Risk
It also does not apply to airports where 5G is not deployed. The FAA issued the AD because many systems on the 737 MAX rely on the radio altimeter, including autothrottle, ground proximity warning, thrust reversers and Traffic Collision Avoidance System.
During initial negotiations in January, the wireless companies offered to keep mitigations in place until July 5, 2022, while they worked with the FAA to better understand the effects of 5G C-band signals on sensitive aviation instruments.
The transmitted signal is modulated to sweep over a frequency range of, typically, 100 MHz around 500 times per second. This is a deliberately low sweep rate, designed to avoid height ambiguity which might occur at a
With safety as its core mission, the FAA will continue to ensure that the traveling public is safe as wireless companies deploy 5G. The FAA continues to work with the aviation industry and wireless companies to try to limit 5G-related flight delays and cancellations.
What Happens Now?
Throughout this process, the FAA will work with both industries to track the pace of the radio altimeter retrofits while also working with the wireless companies to relax mitigations around key airports in carefully considered phases.
The FAA is working with the aviation and wireless industries to find a solution that allows 5G C-band and aviation to safely coexist. While that work is underway, the FAA alerted operators that Notices to Air Missions (NOTAMs) may be issued to restrict operations in areas where 5G interference is possible.
It also provides additional information about aircraft systems that could be affected. But telecommunications experts say that there is little or no risk to altimeters from 5G and that the aviation business has had years to prepare for what little risk there is.
"The science is pretty clear — it is hard to repeal the laws of physics," Tom Wheeler, a former chairman of the Federal Communications Commission, wrote in a piece for the Brookings Institution in November, in which he noted that F.C.C.
engineers had found no real cause for concern. 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 the 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. The Helicopter Association International held a webinar last week for its members on 5G interference.
One of the panelists was Seth Frick, a radar system engineer at Honeywell Aerospace, which makes altimeters for many aircraft, including its own military helicopters. Mr. Frick said Honeywell had found a range of errors, from altimeters "getting noisy" to providing no reading, in the company's testing of 5G interference.
Are the AMOCs you've issued going to remain in effect indefinitely? No. The AMOCs that we issued in advance of the rollout of 5G C-band will expire at the end of each month. That's because the wireless carriers have towers that will go live at the beginning of each month as they build out their service.
The clash has been years in the making and came to a head in the last few weeks. AT&T and Verizon agreed on Tuesday to restrict 5G near airports after airlines warned that potential interference from it could cause a crucial device on planes to malfunction, and force them to cancel flights.
Even with the airport restriction, a number of international airlines on Tuesday canceled flights to the United States, although some of those flights were restored. During the two-week delay in deploying new 5G service, safety experts determined that 5G interference with the aircraft's radio altimeter could prevent engine and braking systems from transitioning to landing mode, which could prevent an aircraft from stopping on the runway.
The accuracy of the radio altimeter is given as ±1 ft or ±3% of the indicated height, whichever is the greater. It can be subject to errors due to reflections from parts of the aircraft structure, such as the landing gear, or to leakage of signals between the transmitting and receiving aerials.
The positioning of the aerials is therefore very important and every effort is made by the manufacturer to avoid these errors. The visual warning is usually in the form of a light and the aural warning may be a chime alert or a recorded voice message.
In the event of failure of the system due to loss of power, a system or reception fault, a prominent warning flag appears on the face of the instrument. Additionally, the pointer will be obscured on these occasions or when flying above 2500 ft.
The pointer will take up a known position when the press-to-test button is depressed. In some displays the instrument scale is logarithmic for heights above 500 ft. The difference between the received and transmitted frequencies will vary as the aircraft height varies, and the time taken for the signal to travel to the ground and back varies.
It is the frequency difference that is used to determine the aircraft height above the ground at any instant, using the speed of propagation of the radio beam and the rate of change of transmitted frequency, which are both known.
The FAA is working to determine which radar altimeters will be reliable and accurate with 5G C-Band deployed in the United States. Since the agreement with the wireless companies was reached, the agency has made progress to safely reduce the risk of delays and cancellations as wireless companies share more data and manufacturer altimeter testing results arrive.
The FAA expects to provide updates soon about the estimated percentage of commercial aircraft equipped with altimeters that can operate reliably and accurately in the 5G C-Band environment. Aircraft with untested altimeters or that need retrofitting or replacement will be unable to perform low-visibility landings where 5G is deployed, as outlined in Notices to Air Missions (NOTAMs) published at 0000 EST Thursday, January 13, 2022.
The radio-altimeter manufacturers have worked at an unprecedented pace with Embraer, Boeing, Airbus and Mitsubishi Heavy Industries to develop and test filters and installation kits for these aircraft. Customers are receiving the first kits now. In most cases, the kits can be installed in a few hours at airline maintenance facilities.
AT&T and Verizon's decision to temporarily limit their new 5G network within two miles of airports should address many of these safety concerns — at least for now. But the start of 5G has been years in the making, raising questions about why airlines, the F.A.A., the wireless companies and the F.C.C.
did not resolve them earlier. AMOC stands for Alternative Method of Compliance. The AMOC process allows operators or manufacturers to demonstrate alternative ways to mitigate an unsafe situation. This process is used to clear altimeters that have been proven to be reliable and accurate in certain high-powered 5G environments.
The altimeter was patented by Lloyd Espenschied, a prolific inventor who spent more than 40 years working for Bell Labs, the celebrated research arm of AT&T. The device functions by sending out radio waves to determine a plane's location relative to the ground and other objects.
I've heard about 5G already being deployed in other countries, such as France and Japan, with no issues. Why would the U.S. be different? The U.S. airspace is the most complex in the world, and the FAA holds ourselves and our aviation sector to the highest safety standards.
Deployments of 5G technology in other countries often involve different conditions than those proposed for the U.S., including:
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