Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
CE-19-19
December 5, 2019
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin informs owners and
operators 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.
At this time, the airworthiness concern is not an unsafe condition that
would warrant airworthiness directive (AD) action under Title 14 of the
Code of Federal Regulations (14 CFR) part 39.
Background
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).
Recommendations
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.
For Further Information Contact
Christopher Withers, Aerospace Engineer, 1801 Airport Road, Suite 100,
Wichita KS 67209; phone: (316) 946-4190; fax: (316) 946-4107; e-mail:
christopher.d.withers@faa.gov
For Related Service Information Contact
Rockwell Collins, 400 Collins Road NE, Cedar Rapids, IA 52498; phone: (319) 295-5000.