What happened
On 10 December 2015, a SAAB 2000, registration HB-IZW, operated by Etihad Regional/Darwin Airline, was conducting a scheduled flight from Berlin Tegel Airport to Billund Airport. During the initial approach to Billund, the flight crew encountered difficulties with the glideslope indication. At an altitude of 800 feet above ground level, which was 250 feet below the required minimum altitude for that position, the pilot flying initiated a go-around.
For the second approach attempt, the crew opted for a non-precision approach using the localizer. During this descent, the aircraft's vertical flight path became unstable, descending too steeply and dropping below the established minimum altitudes. This excessive descent triggered the Enhanced Ground Proximity Warning System (EGPWS) with a "terrain ahead, pull up" alert. The crew responded with a second go-around, after which they decided to abort the flight and return to Berlin.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) conducted the investigation, with the Danish AIB acting as an accredited representative. Investigators analyzed radio communications, radar data, and Quick Access Recorder (QAR) data, alongside crew statements. The inquiry focused on the aircraft's descent profile, the crew's monitoring of the vertical path, and the effectiveness of the approach charts used during the incident.
Findings
- The primary cause of the serious incident was the crew's poor monitoring of the vertical flight path, which resulted in the aircraft descending below the stipulated minimum altitude for a non-precision approach.
- The flight crew's approach planning regarding the vertical flight path was deficient.
- The pilot flying's performance was likely reduced due to fatigue, following a modified roster that changed his scheduled day off.
- The approach chart lacked a distance/altitude table, which hindered the crew's ability to effectively monitor the descent.
- The crew did not consistently apply the standard procedure required following an EGPWS warning.
Safety action
Following the incident, the operator, Etihad Regional, implemented several changes to its standard operating procedures (SOPs). These include the addition of specific "on profile" and "stable" call-outs at 1000 feet and 500 feet AAL to ensure approach stability. The airline also updated its minimum equipment list (MEL) regarding flights without EGPWS or GPS and integrated the incident into simulator training. Additionally, Jeppesen updated its approach charts to include recommended altitude descent tables to assist with vertical path monitoring.