An ATSB transport safety investigation into an airspeed management event involving a Fokker 100 passenger aircraft has found the operator’s training did not prepare pilots for the activation of an automatic flight envelope protection mode – alpha mode – during critical phases of flight.
The investigation report details how the Alliance Airlines-operated aircraft’s airspeed reduced below the minimum allowable approach speed during final approach into Rockhampton Airport, Queensland, on 10 November 2019.
The aircraft, registered VH-UQN, was being operated on a regular public transport flight from Brisbane to Rockhampton, with 97 passengers and 4 crew on board.
“Aware of some bushfire activity to the north-east of the airport, the flight crew conducted a standard briefing prior to descent which included the speeds required for the approach, and identifying the threat of reduced visibility due to smoke,” ATSB Director Transport Safety Dr Michael Walker said.
The aircraft was slightly high on approach, and at 400 ft above ground level the flight crew encountered reduced visibility and moderate turbulence due to the nearby bushfire.
This added uncertainty, and delayed the flight crew’s identification of the high approach profile, the report notes.
“In the later stages, crew identified the high approach, and began an attempt to regain the correct profile, the aircraft’s airspeed reduced below the minimum allowable speed at about 300 ft,” Dr Walker said.
This automatically activated the aircraft’s alpha mode automatic flight envelope protection, overriding the thrust levers and accelerating the aircraft.
“The flight crew were unaware of the alpha mode activation, and the pilot flying encountered increased resistance in the thrust levers while trying to manually recover airspeed,” Dr Walker said.
After a short period, the pilot forced the thrust levers to the desired setting. The aircraft’s engines responded, airspeed increased accordingly, and the aircraft landed safely.
“The ATSB’s investigation found the operator’s initial type qualification for the F100 aircraft and cyclic training did not adequately prepare pilots to identify and respond to alpha mode activations during critical phases of flight,” Dr Walker said.
“The ATSB further identified that the aircraft’s rate of descent exceeded the operator’s stabilised approach criteria for a short period during the approach; however, it was also identified that there was no permissible exceedance criteria in the stabilised approach criteria for transient exceedances.”
Following the incident, Alliance issued an operations notice to pilots including guidance on the dangers of low thrust and low airspeed situations during performance decreasing conditions.
The notice also provided greater guidance about the activation of alpha mode within its fleet, and the operator updated its cyclic simulator training to include alpha mode activation scenarios.
“Flight crew awareness of automatic flight protections and their subsequent effect is paramount to the safe operation of passenger transport flights,” Dr Walker said.
“Effective initial and cyclic training, and assessments in these systems, is important to ensure that pilots respond appropriately to these situations during critical phases of flight.”
The ATSB investigation also identified Alliance’s acting safety systems manager at the time of the incident was unable to effectively conduct the role, due to limited experience in the role, increased workload, and remote working conditions during this time.
“This, along with other key changes, limited the operator’s capacity to provide effective safety assurance,” Dr Walker said.
Alliance has, since the incident, finalised its internal safety manual and standard operating procedures, developed a position handover checklist, and reviewed its company policy manual to detail the formal delegation of duties relating to key safety post holder positions.
“This incident highlights that effective change management is an essential part of any safety management system,” Dr Walker said.
“Changes to key safety management systems, key post holder positions, and the procedures and processes that support systems and personnel, need to be carefully managed in order to operate a robust and effective safety management system.”
Read the report: AO-2019-063 Airspeed management event involving a Fokker F28-0100, VH-UQN Rockhampton Airport, Queensland, on 10 November 2019