TCAS II Version 7.1 mainly incorporates two important changes in relation to resolution advisory thresholds and pilot commands.
The first important change involves the monitoring of Resolution Advisory (RA) compliance. That is, when a TCAS II detects after a certain period of time that an aircraft is not responding correctly to the RA, a reversal RA will be triggered to immediately adjust to the other aircraft not complying with the RA.
The second change relates to the "Adjust Vertical Speed" RA issued by the TCAS that requires the decrease in VS to 2000, 1000, 500, or 9 feet per minute. In some cases, pilots were increasing their vertical speed instead of decreasing it. Some aviation representatives concluded that the "Adjust Vertical Speed" aural alert was not direct enough even though the visual RA was present as well. As a result, instead of retraining crews on TCAS procedures, the "Adjust Vertical Speed" RA is replaced with a simple "Level Off" RA. The RA display visually depicts the same "Level Off" command.