The Importance of Autopilot in Commercial Flights

by Leo Cheung

One of the questions pilots get asked the most is “Do pilots just turn on the autopilot and go to rest?” followed by a skeptical thought on whether they are getting overpaid for pressing some buttons. To answer this question, we first need to know what exactly is an autopilot and the application of automation in everyday commercial aviation.

The first recorded autopilot was invented more than 100 years ago to reduce the workload of pilots as the duration of flights started to increase with the advancement of technologies. It was composed of a revolutionary decision to include a gyroscope linked to control surfaces of the aircraft to adjust deviations on the three axes of the aircraft (pitch, roll and yaw). Over the years, with the development of computerised navigational systems, the autopilot became an integral part of the flight management system that interacts with the geographic database to control an aircraft to fly a particular trajectory following the pilots’ input. In short, autopilot is a system that allows the trajectory of an aircraft to be controlled autonomously. 

Australia's Most Obscure And Remote Commercial Airports Boolgeeda airport

Automated landing receives guidance from the Instrument Landing System on ground © JumpOn

How Does a Modern Autopilot Work?

Today, an autopilot is mandatory for commercial operations with more than 20 seats as required by ICAO. In an Airbus 320, there are two systems of autopilot available for redundancy and both systems are required for the aircraft to conduct an auto-land. Air data (speed, height and angle of attack, etc.) are collected from sensors on the airframe surface and are calibrated before being used by the flight computers that calculate how and how much the aircraft should move. These numbers are then sent to hydraulic actuators that control the flight controls (ailerons, elevators and rudders) to execute the required movement. This process is continuous and is commanded by the pilots’ input.

When is the Autopilot Used?

On a typical commercial flight, autopilot is used for almost 90% of the flight. To simplify, we can consider the flight to be divided into 4 phases of flight: takeoff, cruising, approach and landing. Currently, autopilots are not used for takeoff as it requires split-second decisions from the flight crew to abort the take-off in case of emergencies or obstructions on the runway. The autopilot can be engaged as early as 5 seconds after lift-off or when the aircraft has reached 100 feet above ground level. As part of the ICAO requirements, the autopilot must be used when flying above 29,000 feet above mean sea level for more precise air traffic controls and the typical cruising level of an airliner is above 30,000 feet. Some aircraft can conduct auto-land onto runways that are certified for the operation. In this case, both autopilots will remain engaged until the aircraft is on the ground. The auto-land capability allows the aircraft to land in airports where the weather is not ideal, especially with low clouds and low visibility. In other cases, the autopilot will be turned off at around 1500 feet above the ground when the aircraft has established its final flight path. As for now, the capability to taxi and take-off with autopilot is still in development.

Shows A350 being tested for the internal link above

Airbus evaluates the possibilities of automated take-off and taxi in commercial operations.

Why Use Autopilot? Are the Pilots Just Lazy?

The invention of autopilot was introduced in 1912, less than 10 years after the first powered flight as aircraft started to gain longer flight time and a form of relief was needed for the pilots. Today, the main purpose of using an autopilot system remains the same but it is justified even further. The Airbus philosophy suggests that autopilot should be used appropriately at all times and is presented as one of the 4 golden rules of flying an Airbus aircraft. According to the Airbus training manual, the use of autopilot will alleviate workload and enhance situational awareness of the surroundings. This ensures the flight crew can focus more on decision-making in high workload situations during critical phases of flights. For long-haul flights, the aircraft spends most of its time flying straight and level in RVSM* airspace and the autopilot system is a mandatory requirement as it can maintain a more accurate height when compared to the aircraft being hand-flown. The use of the system in low visibility conditions like a foggy morning is also imperative as the pilots will not be able to see the runway and initiate the final flare with visual reference to the ground.

It would be unfair to say the use of autopilot allows the flight crew to slack off as it has been proven to provide comfort and safety in commercial aviation. However, the autopilot is only a system on the aircraft and is prone to errors and malfunctions so the flight crew will have to monitor it actively throughout the flight for any unexpected deviation.

Got any questions about flight automation in airlines? Ask us in the comment section below.

  • RVSM: Reduced Vertical Separation Minima-Air traffic procedures to reduce the height between an aircraft in the airspace to allow more aircraft to travel between 29,000 feet to 41,000 feet above mean sea level.
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