Configuration 1; Honeywell TPU-67A (TCAS II v 7.0) updated to Honeywell TPU-67B (TCAS II v 7.1)
Configuration 2; Honeywell TPA-81A (TCAS II v 7.0) updated to Honeywell TPA-100B (TCAS II v 7.1)


TCAS 7.1 is being offered as an upgrade by all of the major TCAS manufacturers and makes two important safety enhancements.

  1. Aural Warning Change- The current TCAS II aural warning will be changed from “Adjust Vertical Speed, Adjust” to “Level Off, Level Off”.
  2. TCAS Reversals- TCAS 7.1 corrects missed and late TCAS reversals. TCAS reversals were introduced in TCAS 7.0 to adapt to changing situations where the original sense had clearly become the wrong thing to do, in particular when a pilot decides not to follow the Resolution Advisory (RA), or is instructed by Air Traffic Control (ATC) to perform a particular maneuver. The solution in Change 7.1 introduces improvements to the current reversal logic that addresses the late issuance of reversal RAs and potential failures to initiate reversal RAs.


The upgrade also makes the following changes:

  1. Corrects issue when descending through 1000 foot Above Ground Level (AGL).
  2. Modifies the “Datalink Capability Report” (The status report sent by the TCAS processor to the Mode S transponder) to tell the systems that the TCAS processor is hybrid-surveillance-capable.
  3. Allows for the transmission of the TCAS processor part number and software level.
  4. Corrects TCAS multi-aircraft logic issues, which reduces the risk of “close encounters” of multiple aircraft in RVSM airspace.


These enhancements are significant enough to warrant mandates by both the International civil Aviation Organization (ICAO) and the European Aviation Safety Agency (EASA). ICAO has mandated TCAS 7.1 by January 1, 2014, for forward-fit aircraft and January 1, 2017, for retrofit aircraft. By comparison, EASA required all forward-fit aircraft to be updated by March 1, 2012, with retrofit aircraft to follow by December 1, 2015. The certification path for TCAS 7.1-modified units will be accomplished through a Supplemental Type Certificate (STC), Type Certificate (TC) or in some cases a Major Repair Alteration (MRA) project with a re-write of the Airplane Flight Manual Supplement (AFMS). To determine the certification path for your aircraft, please call APG Avionics at: 941-637-8585.