Nearly 14 percent, or 6,255, of the 45,257 U.S.-based aircraft currently equipped with ADS-B Out avionics are not properly transmitting a signal, according to data from Duncan Aviation. While in some cases this is the result of improper hardware installations, in many cases it is caused by incorrect configuration by avionics technicians.

In an ADS-B installation technical paper released by the FAA last week, the agency noted numerous installations of ADS-B Out equipment that broadcast incorrect ICAO codes. “Extra care should be taken to ensure that newly installed systems are configured correctly and verified with appropriate ground-test equipment,” the FAA notes in the paper. In addition, the agency also says in the document that a “high number” of ADS-B Out installations have been completed with an improper emitter category code, which is based on an aircraft’s mtow. Missing or incorrect flight IDs is also a problem, the FAA said in an ADS-B performance report user’s guide issued last year.

Duncan president Aaron Hilkeman pointed out that his company’s data includes aircraft reported as Source Integrity Level zero (SIL=0). This means that the ADS-B Out avionics has been interfaced with an uncertified GPS or portable transmitter that does not meet the requirements to become a TIS-B service client.