Some Ground Stations Having Issues Tracking Aircraft Equipped With The Devices

The FAA has released a Special Airworthiness Information Bulletin (SAIB) following reports of an issue with certain ground stations properly detecting and tracking aircraft equipped with Rockwell Collins TDR-94 and TDR-94D ATC/Mode S Transponders.

According to the SAIB, Certain ground stations outside of the United States have issues tracking aircraft equipped with TDR-94() ATC/Mode S Transponders modified by Rockwell Collins Service Bulletin TDR-94()-34- 30; this is marked on the unit as MOD "30". Issues include instances where aircraft were not detected by a Multilateration (MLAT) ground system, where an aircraft was not tracked when close to the airport, or where a duplicate return was sensed by an Air Traffic Control Radar Beacon System (ATCRBS) ground station.

The loss of detection / duplicate reports usually occur when TDR-94() MOD 30 equipped aircraft are close to the ground station. For MLAT stations, this is usually within 1 nautical mile of the ground station; other ground systems have had issues at a greater distance. This issue is only evident near ground stations that have not implemented Dynamic Minimum Trigger Level (MTL).

There is an update available to the TDR-94() that will allow all ground stations outside of the United States to properly detect and track the aircraft. The FAA recommends that owners and operators, who have a TDR-94() marked with MOD "30", refer to Rockwell Collins Service Bulletin TDR-94()-34- 33 Revision No. 1 or later for further information.

(Image from file)

FMI: SAIB