The topic related to the adaptation of TCAS II v. 7.0 anti- collision avoidance systems to version 7.1 was discussed in one of our articles last year. We have moved from theory to practice. So far, we have been able to modify 5 such flying systems on various platforms (including Learjet and An-26) – four processors of Honeywell TPU 67A type and one Rockwell Collins TTR 921.
Each upgrade is carried out at the headquarters of the device manufacturer, but in close cooperation with our company (as a dealer) and that is why we are the first point of contact for any modification. After upgrading the software to version 7.1, devices receive a new Part Number, but no modifications are required to the system components that work with the processor. The device returns after the change and can be installed on a „plug & play” basis.
There are cases and such possibility is given by Rockwell Collins– where devices in version 7.0 can be exchanged for more modern systems, already containing version 7.1. Then the new system comes with a new mounting rail (due to the different dimensions of the devices), which should be replaced on the plane. In rare cases, such process requires a slight modification of the electrical installa- tion, but then all necessary instructions on how to perform it are included in a package with the new device.
We should remind here that EASA has already obliged (on 16 December 2011) aircraft owners to modify the TCAS II system to version 7.1 by 1 December, 2015 (EU Regulation No 1332/2011)
Our company offers such service for the following processors:
– TPA100, TPA81, TPU67A firmy Honeywell,
– TT 920/921/4000 firmy Rockwell Collins.
The basic change in the software concerns commands of vertical speed adjustments RA (Resolution Advisory) and the new RA Reversals logic
Adjust Vertical Speed, Adjust” (AVSA)
The AVSA command has been identified as misleading and there are documen- ted cases where pilots mistakenly responded to this command. Version 7.1 replaces four „Adjust Vertical Speed, Adjust” commands with one command, which is „Level Off, Level off”.
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TCAS Reversals
TCAS Reversals were introduced in amendment 7.0 in order to adjust to the changing situation, where the original design became the wrong advisor in making decisions. This is particularly the case when one of the pilots decides not to follow the TCAS II instructions or is instructed by ATC to perform certain maneuvers. Version 7.1 introduces improvements to the current Reversals logic, taking into account the described factor.
