An Embraer E190 passenger aircraft entered a low-speed state shortly after take-off from Honiara, in the Solomon Islands, after its flight crew inadvertently selected the incorrect speed mode before take-off.
On 23 February 2024 an Alliance Airlines E190 was being prepared for a scheduled passenger flight from Honiara to Brisbane, operated on behalf of Solomon Islands Air. On board were two flight crew, two cabin crew and 66 passengers.
During the Before start procedure, an ATSB final report notes, the captain unintentionally left the speed selector knob in manual mode, instead of the recommended flight management system mode.
As the aircraft climbed through 1,200 ft at an airspeed of 144 kt, the flight management system mode transitioned from take-off to vertical flight level change, and thus the flight director began to target the selected manual airspeed which, at that time, was 125 kt.
"While the captain was monitoring traffic and weather, and making a radio broadcast, the first officer was not effectively monitoring the airspeed and, as a result, did not initially detect the aircraft was slowing down," ATSB Director Transport Safety Stuart Macleod said.
After a short time, the captain detected the aircraft was not accelerating.
However, thinking it was due to excessive drag, the captain retracted one stage of flap while below the minimum flap target speed.
"This meant the aircraft entered a low-speed state, and the crew received corresponding cockpit low airspeed visual alerts," Mr Macleod said.
As the aircraft continued to slow, the first officer detected the speed mode was incorrectly set, and changed it to flight management system mode, at which time the aircraft began to accelerate to the correct airspeed.
The ATSB's investigation into the incident found that Alliance's pre-flight procedure required the flight crew to initially set the speed knob to 'manual', despite that mode rarely being used for take-off, thus increasing the risk of the aircraft departing with the incorrect mode selected.
"Additionally, Embraer's airplane operations manual was inconsistent with its standard operating procedures manual in regard to setting the speed knob to manual in the Before start procedures," Mr Macleod noted.
In response to the investigation, Alliance Airlines has amended its pre-flight procedures, and Embraer has committed to resolve the discrepancy between its airplane operations and standard operating procedures manuals.
In addition, the ATSB found Alliance Airlines flight crews' conduct of the Before start procedures and Pre-take-off brief review were not being performed effectively to ensure the speed selector knob was correctly set and checked, likely due to a training deficiency.
Alliance Airlines has reinforced training and procedural guidance in response to this finding.
"This incident shows how important continuous attention to the modes displayed on the primary flight display is to situation awareness," Mr Macleod summarised.
Loss of mode awareness, or mode confusion, has been identified as a factor in several major accidents around the world.
"Loss of mode awareness can result in flight crews mismanaging an aircraft's energy state, such as the low-speed state that eventuated in this case."
You can find here the final report: Incorrect configuration involving Embraer E190, VH-UYI, near Honiara International Airport, Solomon Islands on 23 February 2024
