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Feb
23
2024

Radar Altimeters and 5G Exemptions…For Safety or Convenience?

Posted 52 days ago ago by Admin

Author: Randy Rowles

The introduction of radar (also known as radio) altimeters to the helicopter industry began as a highly accurate tool to validate actual height above ground during Instrument Flight Rules (IFR) flight operations. Like the fixed wing world, a helicopter being flown on an IFR approach needs accurate information on height above ground to continue to a safe landing. 

As the helicopter industry introduced additional technologies, the requirement for a radar altimeter in a helicopter expanded. It was determined that a radar altimeter would be required equipment for NVG modified cockpits and stated accordingly in 14 CFR 91.205(h)(7). After April 24th, 2017, the FAA expanded the requirement for radar altimeter installation and use in Part 135 operations with the introduction of 14 CFR Part 135.160(a): Radio Altimeters for Rotorcraft Operations.

The clear intent of the regulation was to improve aviation safety. Providing the pilot with a highly accurate tool to know their actual height above ground would reduce controlled flight into terrain (CFIT) accidents. 

In 2015, the Federal Aviation Administration (FAA) and the world aviation industry jointly raised concerns regarding allocation and permitted use by telecom companies of frequencies in the 3.4 to 3.7 GHz spectrum (i.e., 5G) — but not the 3.7 to 3.98 GHz spectrum that is the issue for radio altimeters. 

From 2018 to 2020, ahead of the auction for 5G C-Band, the FAA again raised concerns drafting a letter asking for a postponement to collaborate on a solution because in their opinion, 5G C-Band was a major issue for radar altimeter usage in aircraft. Nearing the end of the period where any potential solutions prior to the 5G C-Band auction could be addressed, the NTIA, the federal government's coordinator on spectrum disputes, failed to put the 2020 FAA letter of concern requesting postponement of 5G sale into the FCC's docket. 

In the United States, 5G C-Band services launched in 46 markets on January 19, 2022, all but ignoring the FAA’s concerns on 5G implementation. In response, the FAA established 5G airworthiness directives addressing modifications to the regulatory utilization of radar altimeter equipment in helicopters.  

The FAA states that safety is their mission, and it guides all their decisions. I believe this to be true, however, it seems that common sense is not always included, at least initially.

The FAA requirement for a radar altimeter during NVG and Part 135 operations was a safety-based mandate. During FAA evaluation of early NVG cockpit modifications, FAA test pilots said no NVG flights should occur without a radar altimeter. Additionally, the FAA’s decision for all Part 135 helicopter operators to install a radar altimeter for continued operations was again a critical safety decision. On both points, I will agree the intent of the FAA’s decision was their belief a safety issue exists. 

Once the 5G rollout began, the FAA issued Airworthiness Directives addressing radar altimeter usage in 5G affected areas. Since that time, the FAA has expanded their definition of 5G affected areas to say that the entire lower 48 states are now 5G critical. 

The solution for the FAA to allow flight operations to continue when radar altimeter equipment is required was using regulatory exemptions. The Helicopter Association International (HAI) was an early entrant of a 5G exemption request which was intended to benefit most of HAI’s helicopter operator members. Although the HAI 5G radar altimeter exemption request was crafted to benefit all operators, the FAA only approved Helicopter Air Ambulance (HAA) operators to be exempt. Additional exemption requests were submitted and approved for the purpose of NVG pilot training to include FAA inspectors and HAA operators to name a few.

It was the limited FAA 5G exemption language, although with the best of intent, that seemed to lack common sense.

For instance, the FAA stated that the approval of the HAA 5G exemption was in the best interest of public safety. If true, why wasn’t Law Enforcement, Firefighting, and other public safety operations included? Within the initial HAI 5G exemption, most law enforcement agencies that fly with NVGs were forced to do so contrary to regulations unless they chose to operate in the capacity of a Public Aircraft Operation due to non-compliant radar altimeters.

Within the FAA’s exemption documents, the FAA outlines their belief that a radar altimeter is expected to be inaccurate and thus exempt from the regulatory requirements of 14 CFR Part 135.160(a). As a Part 135 operator, our company spent thousands of dollars equipping our helicopters with radar altimeter equipment. Why was this investment so critical to safety if only to be expected to have inaccurate readings. We can continue Part 135 flight operations since the FAA stated within 5G exemption language that a radar altimeter may be inaccurate, however, this perspective from the FAA on what was such a critical piece of safety equipment makes no sense. 

Since we also operate with NVGs under Part 135 in most of our aircraft, a radar altimeter solution is required for those operations as well. In this situation, NVGs changed everything. Under the original HAI exemption, we remained compliant for Part 135 operations without NVGs in the dark with an inaccurate radar altimeter, but not with NVGs which would allow the pilot to see the ground which enhances safety of flight avoiding terrain and potential low clouds, etc. 

Here is an example in the form of a question where common sense was lacking on the 5G exemption issue: If an HAA operator is exempt from 5G limitations and allowed to fly NVGs for the safety of a single passenger and crew, why would a Part 135 helicopter with 9-passengers or less have a lesser requirement for safety and be unable to fly NVGs to aid in terrain and weather avoidance?

The FAA states that until 5G radar altimeter solutions are more available, the exemption process is valid. The radar altimeter industry is ready now with 5G solutions. Companies like FreeFlight Systems, a radar altimeter manufacturer, now offer 5G compliant, software based radar altimeter solutions for helicopters today. They are available and FreeFlight Systems and others have them on the shelf. 

On June 23rd, 2023, the FAA reissued Exemption Number 18973B to the Helicopter Association International on behalf of industry. Updates to this exemption took an unexpected turn in the form of a commonsense approach to the 5G challenges the helicopter industry has been facing on the issue. Within the exemption, the FAA expanded stating,” This exemption applies only to Part 91 operators and Part 119 certificate holders authorized to conduct Part 135 operations”. 

What does this mean for you? If you’re operating Part 91 or 135, this exemption applies to you. Within the exemption, you can continue to fly Part 135 operations. For the NVG operators, this exemption expands NVG operational approval from just HAA operations to anyone operating under Part 91 as well. Not perfect, but an improvement!

Wow…a commonsense solution that is both convenient in process and improves operational safety.   

Hey FAA, thank you!  ​

About the Author: Randy Rowles has been a FAA pilot examiner for 20 years for all helicopter certificates and ratings. He holds a FAA Gold Seal Flight Instructor Certificate, NAFI Master Flight Instructor designation, and was the 2013 recipient of the HAI Flight Instructor of the Year Award. Rowles is the owner/president of Helicopter Institute.

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