A recent ATSB investigation shows how unexpected developments or confusion about procedures can contribute to decisions and actions that increase the safety risk to the aircraft.
In the incident, the crew of a Cobham Airline Services Boeing 717 aircraft, was conducting an instrument approach to land on runway 03 at Perth Airport.
The aircraft was conducting an approach in instrument meteorological conditions after a flight from Paraburdoo, Western Australia. When they reached the decision altitude, the crew initiated a missed approach procedure as they had not obtained visual reference with the runway.
Almost immediately, however, they obtained visual reference with the runway, discontinued the missed approach procedure and landed, despite the aircraft being in an unstable condition.
The ATSB found that the onset of fog at Perth Airport at the estimated time of arrival was not forecast until after the aircraft had passed the point in the flight when it had insufficient fuel remaining to divert to a suitable alternate aerodrome. Before that point, there had been no requirement for the aircraft to carry fuel to continue to a suitable alternate.
Under the circumstances, the flight crew considered that the better option was to discontinue the missed approach procedure and land, in spite of the aircraft being in an unstable condition due to the initiation of the missed approach.
This incident highlights the risk of an unstable approach from not following a missed approach through to its conclusion.
Unstable approaches are a frequent factor in approach and landing accidents, including controlled flight into terrain. The Flight Safety Foundation has developed an Approach and Landing Accident Reduction Tool Kit to reduce the risk of approach and landing accidents.
‘Handling approach to land’ is also a top safety concern in the ATSB’s SafetyWatch initiative. The ATSB has identified an increasing trend where pilots mishandle or mismanage their aircraft and flight profile when unexpected events arise during the approach to land.
The occurrence also highlights that during a flight, the forecast weather at the destination may change and it is advisable to obtain the most up-to-date weather forecasts. However, pilots should be alert to the fact that the actual weather can differ significantly from forecasts.
Read the report: Weather-related operational event involving Boeing 717, VH NXO, Perth Airport, Western Australia, on 1 June 2012