An incident in which a freight aircraft flew below the minimum permitted altitude has highlighted the value of having a clear and, where appropriate, shared contingency plan.
The incident occurred on 17 June 2016, as the Boeing 737-376 was arriving on a freight service to Launceston, Tasmania from Melbourne. Air traffic control (ATC) advised the crew that, based on the latest automated weather observations, rain showers and overcast cloud were impacting visibility.
After arriving overhead Launceston, the flight crew proceeded to conduct an instrument approach to the runway but, owing to the weather conditions, they could not see the runway, and elected to conduct a missed approach and go around for a second approach.
After they had climbed away from the runway, the captain initiated a left turn to reposition the aircraft for a second approach. While responding to a call from the airport groundsman, the captain handed control of the aircraft to the first officer (FO). The captain instructed the FO to maintain the turn, but did not advise where they were turning to or onto what heading. There had been no discussion about how the aircraft would be manoeuvred on completion of the missed approach.
The resulting flight path resulted in the aircraft entering an area with a minimum permitted altitude of 5,800 ft., but it had only climbed to about 4,400 ft. In response, air traffic control issued a safety alert for terrain and instructed the crew to climb the aircraft above the minimum safe altitude.
The aircraft was never in immediate danger of colliding with terrain, but its operation over an area and at an altitude less that that prescribed for safe flight was cause for concern.
Stuart Macleod, Director Transport Safety at the ATSB says this is not the first time they have seen this sort of problem. “The approach and landing phase of a flight brings a substantially increased workload,” said Macleod. “In fact, that is the phase of flight traditionally associated with the highest accident rate.”
A similar incident occurred in 2011, when an Airbus A320 descended below the minimum permitted altitude after conducting a go-around at Avalon Airport in Victoria. The ATSB investigation found that flight crew, despite recognising the potential need for a go-around, did not plan for a return to the runway. Indeed, the workload associated with the execution of the go-around prevented them from planning the return to land until they’d levelled at 3,000 ft.
“Both incidents showed the safety benefit of intervention by air traffic controllers,” said Macleod. “But it’s far better to have things right without being corrected. The importance of good planning and good communication around the approach and landing phases of a flight is one of the key messages in our SafetyWatch list of concerns.”
The ATSB is encouraging operators and flight crew to consider including appropriate missed approach considerations, such as intended flight path, crew actions, terrain clearances and ATC requirements into their approach briefings.
For more information on managing flightpath during the approach to land, visit the ATSB’s SafetyWatch page.