What happened
During pre-flight preparations, the captain failed to switch the speed selector knob from manual to the flight management system (FMS) mode. This error went unnoticed by both crew members during their pre-start scans and the take-off briefing.
Following take-off, the aircraft initially maintained a stable climb. However, once the aircraft passed 1,200 feet and transitioned into vertical flight level change (VFLCH) mode, the flight director began targeting a speed of 125 kt, which was the value displayed on the primary flight display. As the aircraft entered a 25-degree banked turn, the airspeed began to decrease.
While the captain was occupied with radio communications and monitoring traffic and weather, the first officer failed to detect the decaying airspeed. Believing that the deceleration was caused by excessive drag, the captain decided to retract one stage of flap. This action, performed while the aircraft was already below the minimum flap target speed, resulted in the aircraft entering a low-speed state. The crew eventually identified and corrected the speed mode selection.
The investigation
The investigation examined the crew's monitoring of flight modes, the automation settings, and the discrepancies between various operational manuals. Investigators found that the speed selector knob had been left in manual mode due to a combination of the captain's oversight and the operator's specific pre-flight procedures.
Findings
- The captain unintentionally left the speed selector knob in manual mode without a target speed set.
- The first officer did not effectively monitor the airspeed while the captain was performing departure duties.
- The captain's decision to retract a flap stage while below the minimum target speed contributed to the low-speed state.
- There were significant inconsistencies between the Embraer airplane operations manual (AOM) and its standard operating procedures manual (SOPM) regarding the speed selector knob.
- Alliance Airlines' pre-flight procedures required the speed knob to be set to 'manual' during certain phases, which increased the risk of an incorrect setting being left in place for departure.
- Training deficiencies were noted regarding the effectiveness of the pre-take-off brief and the conduct of before-start procedures.
- The operator's shutdown flow for the right-seat pilot was undocumented and deviated from manufacturer guidance.