Reacting to a just-issued Eurocontrol Safety Warning Message (SWM) about the loss of traffic collision avoidance system (TCAS) functionality, a Germany-based airline captain says many airline checklists are now eliminating a final check on whether TCAS is switched on when lining up for take-off.
The reason, he says, is that such a check, which “creates a head-down moment” at a high-workload, high-risk moment, is missed or ignored for runway safety reasons.
The captain notes that TCAS drills before take-off have been modified because of the increasing use of Mode S ground surveillance by air traffic control, which means that TCAS is now left at standby during taxiing instead of being turned on with the transponder after engine start as it used to be.
Eurocontrol safety management tools expert Tzvetomir Blajev, examining the lessons emerging from the Gol Boeing 737-800 collision with an Embraer Legacy business jet over Brazil last September used the emailed SWM to remind pilots that the TCAS and the transponder must both be switched on, otherwise there will be no airborne collision avoidance system (ACAS) alerts to the pilots in conflicting aeroplanes.
The US NTSB says evidence suggests the Legacy’s TCAS was serviceable but not switched on, and neither aircraft received any ACAS warning as a result.