An Australian Transport Safety Bureau (ATSB) visibilty study has revealed that ADS-B In would have alerted the pilots of two aircraft involved in a mid-air collision south of Mangalore much earlier.
The accident in February 2020 was the first fatal collision of two civil aircraft operating under IFR in Australia.
In March this year, the ATSB released its final investigation report, which concluded that the pilots did not manoeuvre to avoid the collision or communicate with each other probably because the risk of collision was not recognised,
“To support the investigation, the ATSB initiated an aircraft performance and cockpit visibility study to determine when each aircraft may have been visible to the pilots of the other aircraft,” said ATSB Chief Commissioner Angus Mitchell.
“In addition, the study was undertaken to determine what effect an ADS-B In system would have had on the pilots’ ability to detect traffic as they converged.”
The investigation found that the pilots had insufficient time to see the other aircraft as cloud likely obscured the aircraft up until the collision, The study found that even in better visibility the pilots were unlikely to have had sufficient time to see another in time to avoid a collision.
“Analysis indicated that even in clearer conditions than experienced on the day of the accident, closing speeds and shielding by the aircraft structures would have limited the pilots’ opportunities to acquire the other aircraft, with two of the four pilots involved likely having the opposing aircraft shielded from their view at key moments prior to the collision,” Mitchell said.
As part of the study, the ATSB developed scale 3D models of the internal and external structures of the aircraft using laser scanning technology, and determined the pilots’ approximate eye position within each model.
Animations using ADS-B position and aircraft performance data showing the cockpit view for both pilots in each aircraft overlaid with simulated cockpit traffic displays and alerts were created, supplemented by recorded air traffic control data.
These animations revealed the limitations of see-and-avoid and demonstrated the significant additional alerting time that would be provided by an ADS-B In display with an aural alert.
“The study has clearly shown that had the aircraft been equipped with ADS-B In, the pilots would have been assisted in locating the other aircraft and alerted to its position much earlier than by visual acquisition,” Mitchell said.
“The ATSB continues to strongly encourage the fitment and use of ADS-B transmitting, receiving and display devices in all general and recreational aviation aircraft, as these devices can significantly assist pilots with the identification and avoidance of conflicting traffic, and are available at relatively low-cost.”
The ATSB has produced a video simulating the flight paths of the two aircraft and how the limitations of the see-and-avoid principle reduced the opportunity for either pilot to have avoided the conditions, compared to what they would have seen if ADS-B In was fitted.
The full visibility study is available on the ATSB website.