A109 All Series
Maintenance Inspection Authority
Maintenance Inspector 30
Deviation / Discrepancy - Procedural Published Material / Policy
ATC Equipment / Nav Facility / Buildings; Chart Or Publication; Manuals; Procedure
A rotorcraft was in a all metal hanger with all doors closed except one with a 5 ft. walk through space. The aircraft was undergoing a FAR part 91. 411 413 static & transponder 24 month test. The aircraft is also ADS-B (aircraft dependent surveillance broadcast) equipped with a Lynx NGT9000 plus transponder (ads-b in and out). We had performed this test on numerous aircraft in the past in the same location within the building to contain the transponder altitude signal as the test aircraft altimeter system was raised to perform the required testing. No problems with outside aircraft either in the pattern for the airport or overflying the area were ever noted or reported. In the time period between the last aircraft test and this one; the airport had installed an additional ADS-B surveillance radar site. No notification was sent to any operators and we were not informed by the administrator. During the 91.411 / 413 testing; the new radar equipment received the ADS-B data and it was routed into the national airspace system automaticaly. The next day; we received a call from our FSDO (Flight Standards District Office) concerning a possible deviation by a commercial air carrier to a traffic conflict alert generated by the ADS-B system. The conditions were VFR but ATC advised the carrier of the presence of the test aircraft even though it was on the ground in a metal hanger.There should be a provision ; either through a phone contact with ATC to provide a ' test ' window for performing this type of aircraft maintenance with the registration number being posted on the ads-b data as an aircraft under test or other nomenclature. Possibly a software change to allow a maintenance function to be displayed through the ADS-B broadcast that would alert other aircraft that this particular ADS-B report is in fact not an airborne aircraft. Due to the sensitivity of these airport surveilance radars; it was found by phone calls to other operators; that this is a problem that is recurring around the country. The ramp test equipment has provisions to contain the transponder signal; but the effect of RF (Radio Frequency) leakage is not guaranteed.
Maintenance Inspector reported that a Radio Frequency leakage occurred during maintenance ADS-B ground test.