Autonomous Driving — Airplane vs. Automobile

Anyone in the autonomous vehicle industry might wonder what pilots do in the cockpit at the current level of machine automation. In this article, I describe how a commercial airplane is operated as opposed to an AV in a few scenarios using AV terminology.

Scenario 1: Route Planning

From airport A to B, there is really only one designated route that all commercial airplanes must adopt and it is defined by multiple points of specified longitude and latitude. Although there are rarely two flights on the same route at the same time, in case there are or the timing is very close, altitude is the way to avoid conflict. In fact, ATC (Air Traffic Control) or the commonly named ATS (Air Traffic Service) in the West manages all flights regardless of airline operator.

The pilots would pre-set the route in the system before takeoff. Takeoff is a manual operation but once it reaches a certain altitude as agreed with ATC, the pilots would connect to autopilot so the aircraft follows designated directions and speed without pilot intervention. During the flight, there are cases when the route needs to be adjusted temporarily and they are summarized in the next scenario as collision avoidance.

Scenario 2: Collision Avoidance

The chances of hitting an obstacle up in the air seem very small because the route has been planned based on all the static and dynamic factors. However, there are situations requiring action.

A thunderstorm, cumulonimbus in aviation terminology, is one of the common hazards. An aircraft is fitted with weather radar to detect cumulonimbus (Cb) within an effective range. The pilots would be able to read from the display unit if a Cb is for example 100 nautical miles ahead of the planned route. Then the pilots would propose a detour trajectory to the ATC in charge based on the Cb size and position. Upon ATC approval, the pilots could go ahead with the detour manually or through adjusting the system.

In case of a temporary air traffic control, ATC would notify pilots with detailed avoidance instruction.

An aircraft is fitted with a Traffic Collision Avoidance System (TCAS) that monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder. TCAS can warn the pilots of impending collisions and advise maneuvers based on the location information received from nearby aircraft. In an emergency like this the pilots have to operate manually. Usually ATC makes sure it doesn’t happen while TCAS is independent from ATC to provide the extra sensing and safety warning.

An aircraft is also fitted with the Ground Proximity Warning System (GPWS) that monitors an aircraft’s height above ground or an obstacle below the aircraft. It keeps tracks of height through altimeter radar and under certain dangerous modes it would warn the pilots with visual and audio messages like “TERRAIN” “PULL UP”. Together with GPS on the aircraft, by comparing current location with a database of the Earth’s terrain, GPWS also predicts future terrain features leaving sufficient time for avoidance action.

Although the airplane can’t automatically avoid an obstacle, it can warn the pilots and even guide them to bypass obstacles in most cases.

Scenario 3: Parking (Airplane Landing)

There are analogies between airplane landing and vehicle parking. Landing can be automatic or manual.

In the automatic case (enabling “instrument landing system”/”ILS”), once the aircraft reaches a certain distance to the touchdown point, it would follow a programmed trajectory to descend. This is commonly used when the landing area has minimum visibility.

In most cases pilots manually land the aircraft to practice skills or demonstrate to fellow pilots. Moreover not all airports support ILS.

During the landing roll, in case of an unexpected obstacle on the taxiway, the tower and the pilots are responsible for identifying it and avoid it. The aircraft is not able to sense it.

When there is traffic at the landing airport, the tower would tell the pilots to hold within a designated airspace. The pilots can maneuver the aircraft in circles or set up the autopilot system to do so.

Conclusion

The modern flight control system assists humans by aggregating sensor information, sending hazardous alerts/warnings and even controlling the aircraft. To a large degree, it relieves pilots from mundane tasks. Meanwhile, pilots can always override the system by disconnecting it. In conclusion, automation in commercial aircraft parallels automation within level 2 or 3 autonomous vehicles.

However, if we benchmark airplane and automobile by the 3 components of an autonomous driving system (perception, planning and control), aircraft manufacturers would tend to focus on planning and control in order to achieve higher level of automation. Meantime, automobiles are still seeking a major breakthrough with vehicle perception.

(Initially published on LinkedIn on October 21, 2019.)