Recently the FAA contacted Doobert to bring up an issue with pilots using the call sign ARF as a flight designator. The issue is a problem with matching actual aircraft using the designator in flight on an IFR flight plan. Using designators for flights is an approved process. Animal rescue pilots can file using an alternate call sign. For example, if your aircraft is N52431 you can file using ARF431. When using the ARF designator in flight over the radio, you should identify yourself as ANIMAL FLIGHT FOUR THREE ONE. The ARF callsign is registered with the FAA to be used by saying “animal flight,” not ARF on the radio. If you want to spend hours looking through the list of call signs and telephony designators, click here. The reason this is becoming a bigger issue with the FAA is because of the implementation of ADS-B and the unique identifiers that are assigned to aircraft using a compatible transponder. The transponder identifier, which is set in the software, is a unique code linked to a specific aircraft. Let’s say for example our aircraft N52431 has an ADS-B transponder and it is programmed with the unique code of A69AA6. (You can lookup your unique assigned code if you click here.) If you just file an IFR flight plan without using the ICAO format or you don’t provide the appropriate Mode S Hex Code with your flight plan, the FAA will be unable to match your ARF call sign to your aircraft, automatically. As an IFR pilot I’m a big fan of FLTPLAN.COM and I file all of my flights using the site. This site makes using a call sign, like ARF, a no brainer if you have setup your aircraft defaults with the ICAO data for your aircraft. This would include the Mode S Hex Code for your ADS-B transponder. Here is a screenshot on how I would fill out the FltPlan.com form if I was filing and IFR flight plan through them. Since the ICAO identification is already set by default, the call sign is automatically linked to your aircraft and there is no issue for the FAA to deal with. The FAA says, “Pilots must be aware that when an aircraft is equipped with ADS-B, the ADS-B call sign must exactly match the flight plan call sign.” But in the FltPlan.com screenshot above you can see my flight plan is associated with my aircraft but I have listed an optional call sign for that specific flight. The optional call sign gets passed to controllers and I’ve never had an issue as a result. I’m sure there are a bunch of workarounds for making this work, like trying to insert something in the “remarks” box, but I’ve found that is not as reliable. Controllers have told me that sometimes the remarks section gets truncated and they don’t get all the information. So I never use the remarks box. If you’d love to read the official FAA presentation on ADS-B Call Sign MisMatch issues, click here.