The crew of the Boeing 737, VH-TJC, were operating a scheduled sector from Coolangatta to Melbourne, with the co-pilot acting as handling pilot. Air traffic control cleared TJC to depart from runway 14, with a requirement to maintain a heading of 150 degrees after becoming airborne. The departure clearance included an instruction that TJC was initially limited to climb to an altitude of 6,000 ft. As the crew lined up on runway 14, they observed rain showers to the south of the airfield. The crew selected the wing flap setting of FLAP 5 for the take-off.
After TJC became airborne the co-pilot, observing indications of a positive rate of climb, called for "gear up". The pilot in command reported that on hearing the "gear up" call, he observed his airspeed indicator to be at the speed when flaps would normally be retracted from the FLAPS 5 position to the FLAPS 1 position. Noting this airspeed, he positioned the flap lever to the FLAPS 1 position instead of positioning the landing gear lever to the UP position. However, he did not call "flaps 1 set" when the flaps reached the FLAPS 1 position, which should have been done in accordance with the operator's standard operating procedures. At about the same time, TJC encountered mild windshear from the rain showers in the area as it was approaching the departure end of runway 14. The co-pilot was concentrating on maintaining the aircraft's flightpath and did not notice that the pilot in command had retracted the flaps instead of the landing gear. As the aircraft continued to accelerate, both crewmembers became aware of an unexpected increase in ambient noise and immediately realised that the landing gear was still in the DOWN AND LOCKED position. The landing gear was selected up and then flaps fully retracted to establish the aircraft in the climb configuration.
The co-pilot did not engage the autopilot/flight director system but continued to hand-fly the aircraft. As the aircraft approached 6,000 ft, the crew received clearance to climb to flight level (FL) 200. The pilot in command entered 20,000 ft in the altitude display of the autopilot mode control panel. The co-pilot continued to hand-fly the aircraft, and as the climb progressed, the airspeed decreased to the minimum flaps-up manoeuvre speed. On observing the reduction in speed, the co-pilot recognised that the autopilot/flight director system was incorrectly configured. He immediately applied increased engine thrust to increase speed above the flaps-up manoeuvre speed, and at the same time engaged the vertical navigation mode on the autopilot/flight director system mode control panel. With the correct climb reference speed now available from the flight management computer system, the climb continued normally, and the aircraft proceeded to its destination without further incident.
Subsequent analysis of information from TJC's flight data recorder (FDR) revealed that flap retraction from the FLAPS 5 position commenced 5 seconds after TJC became airborne, when it was approximately 130 ft above ground level (AGL). The flaps had retracted to the FLAPS 1 position 20 seconds after lift-off and at approximately 960 ft AGL. The landing gear was retracted 27 seconds after lift-off and at approximately 1,250 ft AGL. Flap retraction from the FLAPS 1 position commenced 51 seconds after lift-off and at approximately 2,550 ft AGL, and the final climb configuration was achieved 55 seconds after lift-off and at approximately 2,630 ft AGL. A positive rate of climb was maintained throughout this sequence of events, and no degradation of the aircraft flight path was evident.
At the time of the occurrence, the crew were on the first day of a 4-day tour of duty, during which the pilot in command and co-pilot were rostered to fly together. They had commenced their tour of duty earlier that day in Melbourne, and the occurrence sector was their second flight sector for the day. The pilot in command had commenced the tour of duty after having the previous 3 days off duty, and the co-pilot had done a tour of duty in a flight simulator the previous day. During the course of the investigation, the pilot in command reported that for a period prior to the occurrence, personal stressors had caused him to experience limited and interrupted sleep patterns.