• The paths of YXH and HMQ over Mangalore. (Google Earth annotated by the ATSB)
    The paths of YXH and HMQ over Mangalore. (Google Earth annotated by the ATSB)

A missed approach executed by a Piper Seminole at Mangalore last year resulted in the TCAS in a HEMS helicopter to issue an advisory to the crew, an ATSB report has found.

Babcock AW139 VH-XYH was on a retrieval mission from Yielima to the Royal Melbourne Hospital when it came into conflict with Seminole VH-HMQ after the aeroplane executed a missed approach to the RNAV on runway 36 at Mangalore. The TCAS on the helicopter issued an advisory then a resolution.

The two aircraft passed each other in cloud with only 543 feet of vertical and 333 m of horizontal separation, with the pilot of the AW139 commencing a right turn rather than descend below the LSALT.

Both aircraft continued to their destinations without further incident.

"The ATSB’s investigation into this occurrence found that while the helicopter pilot was aware of the Seminole, they did not consider the possibility of the Seminole conducting a missed approach, which might conflict with the helicopter’s flight path,” said ATSB Director Transport Safety Stuart Macleod.

“The Seminole’s pilot, meanwhile, reported not hearing broadcasts from the helicopter and misinterpreted traffic advice from air traffic control, and consequently was not aware of the helicopter nearby and that an incident had occurred.”

The ATSB also found that the helicopter operator's TCAS knowledge was lacking with respect to resolution advisory alert terrain considerations, and the required intensity of response manoeuvring.

“As such, this incident highlights the importance of effective flight crew TCAS training,” Macleod said.

“TCAS is a complex system which serves as a ‘last line of defence’ in airborne collision avoidance. Thorough knowledge of the system is critical in ensuring that crews respond appropriately to TCAS resolution advisories.”

The Seminole was not equipped with with TCAS or ADS-B In and was not required to be.

Macleod went on to stress that in non-controlled airspace radio remains the primary defence in avoiding mid‑air collisions by aircraft crews maintaining effective listening and pro-active broadcasts, and encouraged aircraft owners to fit both ADS-B Out and In to help with situational awareness.

The full report is on the ATSB website.

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