The aircraft descended below a cleared altitude and then descended below the ILS glideslope because the ALTITUDE SELECT mode of the flight director was not armed. The incorrect flight path was first noticed by a ground controller, who had no formal responsibility for this phase of flight, when the aircraft had descended to within 800 ft of local terrain approximately 5 nm from the runway threshold. The aerodrome controller advised the pilots of the aircraft’s position and although they modified its rate of descent it did not regain the correct vertical flight path. The aircraft landed without further incident. The investigation also considered a similar event involving G-JECK (EW/G2009/05/39).
DHC-8-402 Dash 8, G-JECI 03-10.pdf (754.18 kb)