You’ve Got the Wrong Number, Please Dial Again
In the previous CSMM article, we discussed how most GA pilots are not typically affected by this issue since the N-number they use as their call sign is almost always the same number entered into their ADS-B system. Recent data confirms this is still the case. As long as your ADS-B Out system is properly installed and configured to match your registration or N-number, you’re good to go. However, sometimes GA operators are simply unaware they have a mismatch, which is often the result of the installer “fat-fingering” the registration number into the ADS-B unit. But don’t worry, there’s an easy way to check that.
The FAA’s Public ADS-B Performance Report (PAPR) tool can verify that your system is configured properly. Simply fly in an area of ADS-B coverage and then submit a request. PAPR reports are typically delivered within 30 minutes and can verify if your system’s call sign is matched properly with your aircraft as well as detect any other operational deficiencies with your ADS-B transmitter. If you suspect a typo is the cause of a CSMM, your repair shop should be able to help correct it. If the aircraft identification input on your unit can be manually configured, you should be able to update it yourself.
Beyond the “Call” of Duty
The more pervasive problem with CSMM lies with operators who use specialized call signs that differ from the aircraft’s registration number, like an Air Ambulance flight. By using a pilot-programmable ADS-B unit, an operator can easily sync the ADS-B call sign with the flight plan call sign to avoid a CSMM. However, some ADS-B transmitters do not have a pilot changeable call sign feature, and many air ambulance operators change their call sign depending on the need for priority handling. This sticking point has required some creative thinking to resolve.
FAA System Operations Security handles call sign policy and is the nexus between call signs and ADS-B equipment. Working with members of the air ambulance community, the FAA drafted new language in Advisory Circular (AC) 120-26M, Assignment of Aircraft Call Signs and Associated Telephonies, to resolve this issue. There were differing understandings in the community regarding the use of N-numbers, local call signs, and priority handling. Section 2.4 from the AC addresses priority handling for civilian air ambulance flights, clarifying that when the pilot states “MEDEVAC” before its FAA-authorized call sign or N-number, ATC will provide priority handling in accordance with FAA Order JO 7110.65, no exceptions. For any MEDEVAC flight, there is no additional flight plan filing requirement, such as entering “MEDEVAC” in the remarks section.
Here’s an example of how MEDEVAC is now used during a flight using a local call sign:
NO PRIORITY: For radio transmissions, use “MID-ATLANTIC Three;” when filing a flight plan, file as MA3.
PRIORITY HANDLING REQUESTED: For radio transmissions, use “MEDEVAC MID-ATLANTIC Three;” when filing a flight plan, file as MA3.
While this policy change allows air ambulance operators without programmable ADS-B units to still receive priority handling, using a radio transmission to make this request does not automatically communicate this special status to controllers downstream from where the flight is operating. The National Air Traffic Controllers Association (NATCA) and the FAA are currently looking at possible solutions to this problem, which include exploiting data from the remarks section (Field 18) from the ICAO Flight Plan to convey a MEDEVAC status to other controllers. We’ll follow up on their progress in a future issue.
AC 120-26M also provides additional clarity on programmable ADS-B equipment and strongly recommends it for anyone using new or existing FAA-authorized call signs (ICAO Three-letter Identifier, U.S. special, or local) in the NAS. However, if an aircraft operator does not have a pilot programmable ADS-B transponder, the FAA-authorized call sign may be used by having a mechanic or other qualified person preset the call sign in the ADS-B equipment before flight. Otherwise, the pilot must use the aircraft registration number as the aircraft identification when filing a flight plan and for use during radio communications.
To sum up, if the pilot is able to ensure that the local or other FAA-authorized call sign is programmed into the ADS-B equipment before flight, the pilot can continue to use that FAA-authorized call sign. If the pilot is unable to do so, use of the N-number is required.