FAA Proposes Canadian-Airspace Limits for Helicopters With Radio Altimeters, Extending the 5G Rules Already Placed on Airplanes

The proposed AD applies to all helicopters, certificated in any category, that are equipped with a radio altimeter, also called a radar altimeter. It does not name a list of models. Instead it states that radio altimeters are installed on various helicopter models, "including, but not limited to," those of 20 listed design approval holders. The list includes Airbus Helicopters, Airbus Helicopters Deutschland, Bell Textron Inc. and Bell Textron Canada Limited, Leonardo, MD Helicopters, Robinson Helicopter Company, Sikorsky Aircraft, Columbia Helicopters, Erickson Air-Crane, Kaman Aerospace and Helicopteres Guimbal, among others.

The subject is classified under ATA code 3444, Ground Proximity System. The unsafe condition, as the FAA describes it, is that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7 to 3.98 GHz band, known as 5G Lower C-Band, while operating in Canadian airspace. The agency says radio altimeter anomalies that go undetected by the automation or the pilot, particularly close to the ground, could lead to loss of continued safe flight and landing.

The geographic scope is narrow. Because operators would have to comply before a rotorcraft's first flight in Canadian airspace, the FAA notes that helicopters that do not operate in Canada would not have to comply and would therefore have no costs under the proposed AD.

What would be prohibited

For helicopters classed as "non-radio altimeter tolerant," the proposal would require a revision to the Limitations section of the rotorcraft flight manual (RFM) before further flight in Canadian airspace. The wording the FAA supplies would bar four things when operating in Canada:

• Approaches that require radio altimeter minimums for offshore operations. Barometric minimums would have to be used instead.
• Engaging hover autopilot modes that require radio altimeter data.
• Engaging search and rescue (SAR) autopilot modes that require radio altimeter data.
• Takeoffs and landings under any procedure, whether Category A, Category B or by Performance Class in the flight manual or operations specification, that requires radio altimeter data.

The proposal says the flight-manual revision may be made by the owner or operator, provided that person holds at least a private pilot certificate, and that it must be entered in the aircraft records in line with the relevant sections of 14 CFR Parts 43, 91 and 135.

How a helicopter avoids the limits

A "radio altimeter tolerant rotorcraft" is defined in the draft as one whose altimeter, as installed, demonstrates specified tolerances using a method approved by the FAA. Two tolerances are set: one for interference from fundamental emissions in the 3.7 to 3.98 GHz band, measured against a power spectral density curve that varies with height above ground, and one for spurious emissions in the 4.2 to 4.4 GHz band, the range the FAA says radio altimeters use. No action is required for tolerant helicopters.

Modifying a non-tolerant helicopter so that it becomes tolerant ends the flight-manual limits for that aircraft, and the limits can then be removed from the manual. The FAA adds that a helicopter already accepted as tolerant under an earlier AD, 2023-11-07, also counts as tolerant here.

Why Canada, and why now

The proposal traces a path through three earlier steps. The FAA first issued AD 2021-23-13 in December 2021 for all helicopters with a radio altimeter, limiting certain operations where interference was identified by notices to air missions. It superseded that in June 2023 with AD 2023-11-07, which extended the limits to the entire contiguous United States for non-tolerant rotorcraft, because 5G base stations were expected to cover most of the contiguous US.

The new trigger is in Canada. According to the FAA, Transport Canada issued its own AD, CF-2024-15, on 15 May 2024. Then, in late March 2026, Transport Canada told the FAA that from 1 July 2026 changes to the 5G Lower C-band protections would create a more severe interference environment in Canadian airspace.

The FAA's account of those protections is specific. In July 2023, Innovation, Science and Economic Development Canada (ISED), the country's spectrum regulator, put in place measures to limit interference with radio altimeters: exclusion and protection zones, an airport effective isotropic radiated power (EIRP) elevation mask at certain runways covering the majority of air traffic in Canada, and nationwide limits tied to antenna uptilt. The FAA says that from 1 July 2026 the exclusion and protection zones at airports will no longer exist, and updates to the elevation mask, the tilt restriction, an emitter height limit and reduced spurious emissions will protect only radio-altimeter-tolerant rotorcraft.

The FAA explains the elevation mask as a restriction requiring nearby cell tower signals to be angled downward so that they do not interfere with aircraft altimeters.

The airplane rules that came first

The helicopter proposal follows rules that took effect on the day the Canadian changes did. On 30 June 2026 the FAA issued airworthiness directives for airplanes, effective 1 July. Airways Magazine reported that they set operating restrictions for transport and commuter-category aircraft without radio altimeters proven tolerant of Canada's revised 5G Lower C-band environment, covering aircraft from manufacturers including Airbus, Boeing, Embraer, Bombardier, ATR, De Havilland Canada and Gulfstream.

According to that report, the FAA estimated about 1,000 US-registered aircraft could be affected, while noting it lacks definitive data on how many already have compliant upgrades. The prohibited operations it listed for non-tolerant airplanes were certain special-authorization ILS approaches, Category II and III approaches, automatic landings, head-up-display landings to touchdown and enhanced flight-vision-system operations to touchdown. Part 121 airlines with non-compliant aircraft would have to modify them before operating in Canadian airspace, it said.

The cost estimate

The FAA's figures are for US-registered helicopters. It estimates about 5,500 have a radio altimeter installed and that 1,128 of them are equipped to perform the operations the proposed AD would prohibit for non-tolerant rotorcraft.

It says it does not have definitive data on how many helicopters have become tolerant since July 2023, so it keeps the estimates from the 2023 AD and expects that some of the affected aircraft have already been modified, either by replacing the altimeter or by adding filters.

• Flight-manual revision: one work-hour at $85 an hour, so $85 per helicopter and $467,500 across US operators, with no parts cost.
• Optional modification by replacing the altimeter: up to $60,000 per helicopter, including labor and parts.
• Optional modification by adding a filter: up to 24 work-hours at $85 an hour, or $2,040, plus up to $12,000 for parts, for up to $14,040 per filter.

The $467,500 total is the figure the FAA gives; the modification costs are presented per aircraft, with no fleet-wide total.

An interim measure

The FAA calls the proposed AD an interim action. It says it may consider further rulemaking if the Canadian 5G C-band interference environment changes or if Canada issues an operational rule to address interference with radio altimeters.

It also notes two differences from the Transport Canada AD. The Canadian directive describes the fundamental emissions band as 3.45 to 3.98 GHz, whereas the FAA proposal specifies 3.7 to 3.98 GHz, consistent with its 2023 finding. The agency reasons that frequencies below 3.7 GHz are further from the 4.2 to 4.4 GHz band used by radio altimeters, so rotorcraft shown to be tolerant across 3.7 to 3.98 GHz would also be tolerant of emissions below 3.7 GHz.

The FAA certifies that the proposal is not a "significant regulatory action" under Executive Order 12866, would not affect intrastate aviation in Alaska and would not have a significant economic impact on a substantial number of small entities.

What happens next

Comments can be sent through the Federal eRulemaking Portal at regulations.gov under Docket No. FAA-2026-11799, by fax, mail or hand delivery. The agency says it will post comments publicly, and information designated as confidential business information will be handled separately.

For operators the practical questions are straightforward but fleet-specific: whether a helicopter's altimeter, as installed, has already been shown tolerant by an FAA-approved method, whether it flies into Canada, and whether it is used there for offshore approaches, hover or SAR autopilot modes or radio-altimeter-dependent takeoff and landing procedures. If it does, the proposal would mean a manual change at minimum, and altimeter modification as the route to lifting it.

Sources

• Federal Aviation Administration, "Airworthiness Directives; Various Helicopters," notice of proposed rulemaking, Docket No. FAA-2026-11799, Federal Register public-inspection document 2026-20677 (publication date 8 October 2026)
• Airways Magazine, "FAA Issues New 5G Operating Limits for Aircraft Flying to Canada" (30 June 2026)