Using TCAS surveillance to enable legacy ADS-B transponder use for in-trail procedures

TCAS crosscheck is an effective mitigation technique for mitigation for horizontal position uncertainty for legacy Version 0 and Version 1 ADS-B transponders. A geometric analysis shows that TCAS crosscheck is a sufficient mitigation for scenarios when the ITP aircraft and reference aircraft are on an identical track. Analysis holds for any ADS-B application where the required position accuracies are significantly larger than the TCAS range error. A position source error analysis and modified fault tree from the operational safety assessment shows that TCAS crosscheck meets the ITP safety objectives even if the specific reference aircraft horizontal position integrity requirement is not met when the ITP aircraft and reference aircraft are not on an identical track. The methodology presented is applied specifically to ITP, but it is extensible to other applications of ADS-B . Additional analyses were used to show that ITP is safe for aircraft that are outside the range where TCAS crosscheck is possible.