History of Aircraft Control
So, other than computers and software engineering I have this fascination with airplanes. I mean, I think everyone could agree that airplanes are cool and are one of the marvels of modern engineering. As one of modes of transportation, airplanes are the safest with only 20 fatal accidents out of estimated 39.000.000 flights in 2019. That is around one every two million flights. With that kind of track record, despite being weighing around 40 tons with dozens of critical subsystems working together in harmony everytime, most of the modern airplanes are just controlled by two people, how do they manage it?
For that, let’s take a look at how the earlier planes are controlled. The first airplane, built by The Wright Brothers just has 2 kinds of control, a stick which controls your pitch (for going up and down), an unique control for controlling roll-yaw (for turning) which is controlled using the pilot’s hips, and a throttle control on the engine. On the third model of The Wright airplane, the control for the pitch and roll is combined into one stick and another stick for yaw, but still it’s only small amounts of input compared to modern aircraft. Almost all of the early airplanes only have those controls and no instruments for control. By the 1909 on the Bleriot XI, the first airplane to cross The English Channel, the control scheme is already starting to look like the modern airplane with one yoke and rudder pedals, and it has 2 instruments which are oil pressure gauge and a tachometer.
Then The World War I started, in this era we saw rapid improvements in airplane technology that now it is something that is crucial in war and not just a leisure device. The airplanes are now started being built with metal rather than linens and the engine is getting more sophisticated. SPAD S.XIII, one of the most well known airplane at this era, the amounts of controls and instruments have increased which consists of usual yoke rudder and throttle, altimeter, fuel gauge, compass, air pump selector, fuel selector, air speed, and tachometer. But is still pale in comparison to the modern aircraft, and is the start of what to come as the airplane keeps getting complex.
After the war ended, by no means that the development of aircraft is slowing down, instead it keeps getting faster with many of crossings records being broken. In 1919, Alcock and Brown were the first men to cross The Atlantic in a modified Vickers Vimy. This modified aircraft is the first aircraft to have an artificial horizon as a use of navigation. This artificial horizon is the precursor for the modern attitude indicator fitted in all modern aircraft. In 1929, Jimmy Doolittle became the first man to fly an aircraft just using the instruments available onboard without outside view, an outstanding achievement at the time and all modern airplane is required to be able to flown just using the instruments in case of bad weather and low visibility. In 1937, the British Royal Air Force (RAF) choose six of essential flight instruments which are altimeter, airspeed indicator, turn and bank indicator, vertical speed indicator, artificial horizon, and heading indicator. These six instruments are then fitted into all of RAF aircrafts and many other aircraft manufacturers follow in their steps.
The needs for more complex and powerful aircraft leads to the development of large scale aircraft. In 1929, the Dornier Do X was introduced. This aircraft is the largest at its time and has 6 propeller engines. There engines means that there’s more things to monitor and control and the job of 2 pilots aren’t enough for that, by this time we start seeing third person, the Flight Engineer (FE), whose job is to monitor all of the instruments because by this time we starts to see panels full of light indicators and gauges. And for smaller aircraft for this time, we saw that the cockpit is starting to look like a modern Cessna. Also by this time we saw the development of them jet engine with it being more common by the end of WW2. The state of an aircraft control and instrument this time stays relatively the same with some more control for weapons deployment in military aircraft.
By the end of the war, we saw the development of the De Havilland Comet, the first passenger jet aircraft. This aircraft has the similar cockpit layout to the modern passenger aircraft, with a lot of panels and switches, and a flight engineer panel. The aircraft of this time while being more complex but the controls are still hydro-mechanically linked and the instruments are still being mainly mechanical and not electrically controlled.
In 1965, Boeing released the first model of 737, the family of aircraft which then later became the most selling aircraft family of all time. In the first model, 737–100, we start seeing the appearances of Flight Management System (FMS) which is used by the pilot to calculate take off weight, keep track of coordinates and many more things. By the third generation, 737–300 or 737 Classic, we saw the FMC already adapted to the more modern form supporting a full keyboard, and in the cockpit getting more digitized with many of the then mechanical gauges changed to digital display panel, but some of the mechanical gauges instrument are still being kept for redundancy. Redundancy is one of the important principle in modern aircraft design.
In 1987, Airbus released the A320, the first aircraft to fully use fly-by-wire system. The fly-by-wire system means that the input from the pilot is then read by a computer which then moves the control surfaces of the aircraft. This is a revolutionary development because at this time, most of the aircraft is hydro-mechanically controlled, using hydraulic, cables, and pulley. In this series we saw the first usage of side stick on the side of the pilot, replacing the bulky yoke in the front of the pilot and freeing the front space for the pilot which makes the cockpit feels more spacious, a design which Airbus is still using for now. In this series we saw that the cockpit is mainly digital displays with some essential mechanical instruments. Also around this time we saw the job of Flight Engineer get replaced with computers and electronics as the technology kept developing. Because of the advancement of electronic technology, the cockpit became less cluttered as the many controls and instrument displays could be changed in the push of a button.
So back to our original question, how do these steel birds could be controlled with only 2 people and still have minimal accidents? In my opinion it is because the design of a modern aircraft cockpit is really considered thoroughly with every thing has the correct reason to be there, the important information is easily accessible and there are many redundancies built into the design of the system. Pilots of the old day have many things to track and calculate like the takeoff weight, fuel consumption, takeoff speed and many others. The development of FMC now does the calculation job for the pilot leaving their mental capacities to take care of the important things. It’s not uncommon now to see an iPad loaded with aviation apps and maps to be able to do calculations and replace old paper maps, but modern pilots are still being taught how to calculate this things and use paper maps, which are still stored in a compartment in the cockpit for redundancy reasons. The development of autopilot allows the aircraft to be controlled automatically in cruise with the pilot only needing to change the altitude and heading of the aircraft. The autopilots even allow for automatic landing in a well equipped airport but is rarely used. Beside the aircraft itself, there are many protocols and rules that pilots must follow. Every time an aircraft crash happens in any part of the world and the cause is identified, these protocols and pilots are then adapted accordingly to make air travel safer. There are many defined paths in the sky, like roads in the sky, which pilots must follow and air traffic control will always keep track of them to make sure it is safe. Air traffic controllers are a fascinating topic in itself, keeping the modern air travel safe.
As a software engineer, looking at the modern aircraft systems design, I could learn a lot of things like redundancies, make important things easier to keep track of, automate a lot of things but still give the user the abilities to manually do things, and keep iterating until you get satisfactory results.
