The Australian Transport Safety Bureau (ATSB) is investigating an incident in which a Boeing 737-800 aircraft operated by Virgin Australia came too close to the minimum manoeuvre speed.
On 4 January, the aircraft, with registration VH-VUZ, was operating on the Launceston Tasmania-Melbourne route, says the ATSB.
After take-off, the crew put the auto-pilot into level change mode, causing the aircraft to climb at a constant airspeed to 26,000ft (7,920m). The crew neglected to switch out of this mode and into another vertical mode during the climb, however, owing to a heavy workload associated with the short route.
Changing the vertical mode would have allowed the aircraft to accelerate.
"As the aircraft continued to climb at a constant Mach number, the airspeed slowly reduced," says the ATSB. "The crew did not detect the reducing airspeed until the aircraft was approaching the minimum manoeuvre speed at about [35,000 feet]."
The crew reduced the aircraft's pitch and entered a shallow descent to regain airspeed, which allowed an accelerated climb to the intended cruising level.
The ATSB expects to issue a report on this incident in November 2013.
Flightglobal Pro data shows that the build date of the VH-VUZ is 1 January 2011 and the aircraft is leased from SMBC Aviation Capital.