Incident Overview
On 10 November 2015, a Boeing 737-400 aircraft experienced a takeoff configuration warning after the thrust levers were moved to the T/OFF position during takeoff from Istanbul (IST). The incident involved 98 occupants, none of whom sustained injuries.
Sequence of Events
During the takeoff roll, after advancing the thrust levers to the T/OFF setting, the TAKEOFF CONFIGURATION warning illuminated. The monitoring pilot recognized the anomaly and informed the flying pilot, who was the captain. Per the operator's standard operating procedures, the captain holds final authority to continue or abort the takeoff. The captain ordered the flaps to be set to the takeoff position and continued the takeoff. According to flight data recorder (FDR) data, the flaps extended to the takeoff position of 5 degrees at approximately 143 knots. Rotation began at 154 knots, and liftoff occurred at 165 knots. After the flight, no ASR (Aviation Safety Report) was filed. The monitoring pilot reported the event by telephone and later discussed it in person with the Flight Safety Committee (KBZL). The event was entered into the Q-pulse database based on the first officer's description; however, a missing entry was noted on 14 December 2015, and the entry procedure was repeated.
Cause
The investigation stated the cause as crew error due to excessive hurry and a determination to operate on schedule at all costs. This led to the omission of the essential BEFORE TAKEOFF checklist, which contains only three items: Flight Control, Flaps, and Transponder. A contributing factor was the absence of a Takeoff Configuration Test system on the Boeing 737, which could have detected the irregularity before taxiing onto the runway.
Preventive Measures
In response, the Safety Pilot of the Short Haul fleet was informed, and the incident was discussed during the November Instructors' College meeting. The Flight Safety Committee recommended that the Safety Pilot include a description of the event in the Safety Bulletin, which was published in Bulletin No. 10/2015. Additionally, the committee reviewed the QRH and OM B Volume 1 for the Boeing 737 and found that the Before Taxi Procedure in OM B included a "FLAPS" item, but the QRH BEFORE TAXI checklist did not. The committee requested consideration of adding a FLAPS item to the QRH, but the B-737 Fleet Management decided not to modify the checklists. No safety recommendations were issued.