Why do you need to press so many buttons to start a plane? Can’t there be just one button to start everything in sequence automatically?
In: Technology
There could be, but it would probably make the aircraft much less safe. It would be pretty easy to program a computer to go through the normal cold start procedure, even accounting for conditions that would require a the procedure to be modified, perform pretty much every diagnostic check that a human pilot would. It would be 100% reliable, under 2 conditions: every sensor is giving the computer accurate data, and the thing was set up correctly (both by the programmers that made it, and the pilots that pressed the button).
However, in the real world, you can never rely on both of those things being true. Having actual humans go through the means that even if technically all the numbers are right, they can investigate if something doesn’t “feel right”. This means they can catch edge cases that the programmers of an automated system might have missed, and also might notice if a sensor is giving bad data. Also, in the case of an emergency, it’s vital that the pilots are aware of how every system on the plane works and interacts with every other system. By manually switching power from the battery, to the APU, to the engine generators, they’re essentially reviewing how the plane’s electrical system works, which could be the difference between a safe landing and a crash if there is an electrical fault in flight.
[Newer high-end airplanes](https://www.youtube.com/watch?v=qlR0mszVIng) do have automated start sequences. Technically it isn’t too difficult, it’s just that it requires a computerized sequencer to operate all the switches and valves based on inputs from other instruments. When you have critical equipment run by a computer you have to go through a painful, long, expensive process to qualify the software and hardware.
I work in nuclear. Software QA is similar — usually easier to deal with ancient instrumentation than find something with acceptable software QA.
Tldr: It’s more or less a checklist to make sure all systems are working properly.
Some of it may include adjusting the instruments on the dash so the readings are correct based on weather conditions and compass readings from the ground. Radio check on all the radios. Listening to the weather forecast and writing it down. Depending on the aircraft, you may need to prime the engine, start it up, check and make sure it acts as expected when you adjust things. Make sure back up systems are working well. Make sure all the control surfaces, flaps, evelons, rudder is working. Check the exterior lights work. Check to make sure all the sensors, radars, and other equipment is working. Hydraulics and back up hydraulics. Cabbin compression, emergency equipment. Navigation equipment.
That’s about all I can think of, but it’s quite a lot.
Almost every thing on a commercial plane is going to have main systems and back up systems. You want to check it all out before flying.
Even after the plane starts moving you have to check a few other things, like the brakes and throttle.
In a car you’re responsible for 8~ lives and there are not as many systems in play as a B737-800 for say (a car engine dies, you slow and stop; a plane engine dies, you now have uneven thrust on a vessel with hundreds on board and “stopping” means hitting the ground, however well you’re able to do it), which can carry hundreds of souls. if you look through youtube for preflight checklists youll see how necessary each step is. one big thing is safety, make sure all your warning lights work (there’s a test switch for all warning lights). the other is airline cost, you dont want to start your engines until you need them (fuel cost AKA cost index), and before that you need to make sure everything is safe to function in the event of a failure. some planes like the 747 can’t even move until al 4 engines are running because if only 2 are running they would produce an unsafe amount of thrust to move around the airport to the workers on the ramp. so mostly it comes down to safety.
and then there’s redundancy. You can start or restart an engine with the APU, or with the bleed from an already functioning engine, or from electricity from either the apu, a generator, the battery, or ground power. with so many variables you have to check to make sure each is available to you in the event one somehow isn’t.
sticking with the theme of safety, you have to make sure your instrument readings are correct, setting the QNH (make sure your altimeter knows where the ground is), check that your settings are ready for takeoff (go full throttle for a second and make sure the warning sound beeps when you know you aren’t set for takeoff) etc.
a lot of this is programmed into the Flight management system (FMS/FMC) and in fact pretty much all of the flying is done by the computer once you reach the “transition altitude”. but the onus is on you to make sure the computer is doing everything right, and you need to know how to solve a problem if one arises.
When you start a car, the twist of a key actually automatically activates many separate systems. First it powers the electrical system to many critical components. Fuel pump. Engine control unit. Ignition system. Then if you continue twisting the key it engages the starter motor, and starts the engine. You release the key and all of the systems keep the engine running.
In an aircraft all of these critical flight systems are isolated on different switches, and often have multiple backups (fuel pumps, ignition systems, hydraulics, air pressure, different sources of power for the electrical system, totally separate electrical systems). There is a redundancy and level of safety here that lets a pilot troubleshoot and select or de-power systems individually in the event of a failure while in flight or on the ground. Hence the complexity of starting. It requires a certain order of operation to bring everything online to start a plane.
EDIT: Some seriously good discussion here about aircraft. A couple of points to make. Are we talking about starting the engines only, or taking an aircraft from cold and dark to ready to taxi? I agree that FADEC systems allow an automated start. But even then you still have to at least turn on the battery master. And even if the aircraft could be fully automated, that wouldn’t preclude the need to check and verify that everything is working and set appropriately. Also, automated systems are their own system that needs to be monitored with the possibility of failure (MCAS). I’m not making an argument one way or another, thanks for the discussion.
EDIT 2- One final comment guys. Many people have said this, and I will agree. A fully automated, one touch button start aircraft, complete with systems integrity monitoring is technically possible. And in small drones you can actually find this technology today. The question is, is this acceptable, is this safe, and how can we determine the risk going forward. Commercial air travel is by far the safest method of travel in the world today. It’s a really really high bar to even meet. Getting technology to match that level could be coming in the future, but it’s going to be a long and slow implementation.
You want as much control over such complicated systems as possible, if only to be able to work through any in-flight emergencies if need arises.
And, modern aircraft are quite automated anyway, just compare modern computerized cockpit to one from 1960s. Some aircraft had a separate crew member to just control/oversee the engines and other systems due to super high workload.
It is still hard to fly a passenger liner compared to driving a car, bexause you have so many systems there (and often, most important ones are doubled, or quadrupled for safety, too)
Think of it like a Velcro shoe and a laced shoe.
The Velcro shoe just takes 2 steps: pull out taut and bring in the other direction.
A laced shoe requires adjusting the strings and pulling taut, crossing and looping under, creating a loop. Then it’s winding one strong around the other, creating a gap, pulling through, and tightening while making sure it doesn’t come undone at the end.
Both do the same thing, keep the shoes on your feet, but one is more complicated, gives more control to you, and is much more stable and reliable!
If your car malfunctions/breaks down while driving, you can take it to a mechanic, or get a tow. If it’s a plane that’s flying, you have to fix it before you die.
When flipping all those switches to start the plane, you’re not just turning things on; you’re making sure they work. If you find a problem, you can isolate its location; then either attempt to fix it, or abort the flight: thus preventing said problem from crashing your plane.
Pilot here. In a sense, a lot of the larger planes *are* “one button starts”, in that when everything is configured correctly, you simply turn a knob or push a button and the start sequence happens automatically.
The major difference between larger planes and cars is that, while cars can be started simply by the power from the battery alone turning over the engine, supplying fuel from the fuel pumps, and powering the spark plugs all at the same time, jet engines take a lot more “oomph” to turn over. They are far too heavy and need to turn at thousands of revolutions per minute before they gain enough speed to compress the air and begin the combustion process. Hence they are started with pressurized air rather than an electrically driven starter.
This air is typically supplied by a smaller jet engine in the back of the plane called an Auxiliary Power Unit which is small enough that it *can* be started with an electric motor. This smaller jet engine outputs enough pneumatic pressure to drive the larger jet engine and begin the combustion process. However, when it is broken or disabled, they can be started on the ground with a huge cart that is basically a giant fan that blows air into the engine and can get it going fast enough to begin the combustion process. If you have one engine running, it can also supply the air to the other engine. And in the *extremely* unlikely event that you lose *both* engines *and* the APU in mid-flight, the airplane can pitch down and glide fast enough to use the air blowing through the engines to start the combustion process. Pretty cool, right?
So in a way, when everything is working correctly, most larger airplanes are started with a two-button process- start the APU, then start the engines. The reason the airplane is so “configurable” and has so many buttons is primarily for troubleshooting and manually tweaking the systems in the event of a mid-air emergency. Unlike a car, when your engine quits or starts to overheat or something else, you can’t simply pull over and coast to a stop. You need to be able to isolate the affected systems and toggle them on or off as necessary. Also, if a giant computer controls all the systems and the computer itself has a problem (*cough* 737 MAX *cough*) you want to make sure you can manually and directly control the individual systems. Boeing takes the majority of the blame for the MAX design, as well they should, but there was a lot that went wrong on the pilots’ end of those crashes, too.
Airbus pilot here. We have 2 switches to start the airplane, the first is to tell the computer we want to start the engine and the second initiates the start sequence. I flew Boeing before and they have a more complicated sequence, but without going into too much detail the Airbus way is just better.
Feel free to AMA I’m off today!
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