Incident Overview
On 16 October 2006, a Boeing 737-800, registration TC-JGR, was operating a commercial passenger flight from London Stansted Airport to Istanbul Ataturk Airport. The crew consisted of six and there were 93 passengers on board. No injuries or damage were reported.
Sequence of Events
The aircraft was cleared to depart from Runway 05 on a 'Dover Five Sierra' Standard Instrument Departure (SID). The co-pilot was the pilot flying and briefed the commander on the departure. After an uneventful pushback and taxi, the aircraft was cleared for takeoff. Soon after takeoff, the aircraft was observed in a steep nose-down attitude. It then flew level at 500 ft aal (900 ft amsl) for approximately 6 nm. The crew initiated a climb only after being instructed to climb immediately to 5,000 ft amsl. Further clearances allowed the aircraft to reach its cruising level, and it landed at Istanbul without further incident.
Eyewitness Observations
The crew of an Airbus A319 that had landed just before TC-JGR took off witnessed the incident. As they taxied onto Taxiway H, they saw the Boeing 737 flying almost level at approximately 500 ft half a mile beyond the threshold of Runway 23. The aircraft then pitched down markedly before levelling again. The A319 crew initially suspected an engine failure due to the lack of climb performance. They observed the 737 turn right with a shallow bank angle, still level, and noted a TCAS indication of +500 ft above them. The TCAS target later showed a descent rate and then disappeared from the navigation display. The A319 crew informed the Ground Controller, who alerted the Tower Controller.
Crew Statements
The commander stated that after takeoff, the autopilot failed to capture the preselected altitude of 900 ft. He took manual control, flew above 900 ft, and then descended back to 900 ft. Once level, he realised something was wrong and noted the aircraft was below the Minimum Safe Altitude of 1,800 ft amsl, but was not overly concerned as they were in visual meteorological conditions. He reported high workload and did not remember setting FL80 instead of FL70 in the altitude pre-selector. The crew believed the initial level-off at 900 ft was correct per the SID note, but later realised they had not fully understood the 'Initial climb' note on the plate.
Air Traffic Control Comments
Ground Controller: Soon after the landing A319 was transferred, its crew alerted him to the low altitude of the departing 737. He observed the aircraft unusually low and levelling off about one mile from the end of Runway 05, and he drew it to the attention of the Tower Controller and Duty Watch Manager.
Tower Controller: After giving takeoff clearance, he observed a normal takeoff and confirmed a squawk and altitude of 900 ft on the Aerodrome Traffic Monitor before transferring the aircraft to London Air Traffic Control Centre (LATCC). Later informed of the incident, he saw the aircraft still at 900 ft on the monitor.
LATCC Controller: After an initial call from the crew, the controller asked for altitude confirmation. The crew reported 900 ft. He instructed an immediate climb to 5,000 ft. Later, the Mode S readout showed FL80 selected despite clearance to FL70; the crew then corrected it to FL70. The controller asked why they levelled off; the crew cited inability to contact ATC and the FMS.