Boeing Co 737-376, VH-TJC

Although the crew were only operating on the second flight sector for the day, at the time of the occurrence the pilot in command was experiencing fatigue. This was as a result of limited and interrupted sleep patterns. Fatigue increases the likelihood of skill-based errors and has been demonstrated to be a factor or condition that can promote active failures (or unsafe acts). The pilot in command's fatigue reduced his attention to the task. As a result, on hearing the call for "gear up", and on noting that the airspeed was in excess of the initial flap retraction speed, he inadvertently substituted flap for gear and consequently retracted flap instead of the landing gear.

Had the pilot in command called "flaps 1 set" when the flaps had reached the FLAPS 1 position, the co-pilot may have recognised that the flaps had been retracted instead of the landing gear and then been able to alert the pilot in command to the error. However, at the time, he was concentrating on maintaining the aircraft flight path and did not recognise that the aircraft was in the incorrect configuration until the increase in ambient noise alerted both crewmembers that the landing gear was still extended.

Both crewmembers then became preoccupied with the error to the extent that the airspeed was allowed to reduce to minimum flaps-up manoeuvre speed before either pilot noticed that the autopilot/flight director system was incorrectly configured.

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
rainshowers to the south of the airfield. The crew selected the
wingflap setting of FLAP 5 for the takeoff.

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
rainshowers 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.