What happened
On 18 January 2006, a Dorn/er 328-110, registration D-CPRW, was performing a passenger flight from the Isle of Man to Manchester Airport. While approaching Runway 24R in instrument meteorological conditions, the aircraft was being radar vectored by Air Traffic Control (ATC).
During the descent, the crew received instructions to descend from 3,000 ft to 2,000 ft. While the co-pilot acknowledged the clearance, the altitude pre-selector was not updated. As the aircraft descended using vertical speed mode, the descent rate increased to approximately 1,500 fpm. The crew became preoccupied with configuring the aircraft for landing and reducing airspeed, leading them to lose situational awareness regarding their vertical profile.
The aircraft's descent continued dangerously low, reaching approximately 450 ft above the ground. The situation was only identified when the Enhanced Ground Proximity Warning System (EGPWS) triggered a "GLIDESLOPE" alert. The commander immediately disconnected the autopilot and initiated a go-around. The aircraft subsequently completed a second approach and landed safely.
The investigation
An AAIB field investigation examined the aircraft's systems and the crew's actions. Maintenance tests performed on D-CPRW by the operator's provider found no technical faults in the autopilot, navigation, or ILS systems. Tests confirmed that the glideslope could be captured and that the autopilot functioned correctly in vertical speed mode.
The investigation also reviewed the company's Standard Operating Procedures (SOPs). It was noted that the co-pilot used varying checklists depending on the captain on duty, which led to a lack of standardized communication and 'call' procedures between flight crews. Additionally, EGPWS data from previous flights indicated several transient glideslope warnings had occurred on the same aircraft in recent weeks.
Findings
- The primary cause of the incident was the flight crew's failure to adequately monitor the aircraft's flight path and vertical profile.
- The crew was distracted by the tasks of configuring the aircraft for landing and managing airspeed.
- A lack of standardization in cockpit procedures and checklists contributed to inconsistent crew coordination.
- The aircraft's altitude pre-selector was not updated to the newly cleared altitude of 2,000 ft, contributing to the excessive descent rate.