When landing a plane, do pilots immediately pull on the brakes once they touch down, or do they coast a little bit first?

Sort of… depends on what you mean by ‘brakes’.

There’s 3 (and a half) types of brakes we have on most aircraft, and we use them at different times.

Airbrakes

Airbrakes are those square things you can see on top of the wings, and they fold up like that when you land (they’re usually sealed away). They work by pushing against the air (like how a parachute works by catching all that air, except we don’t need the full force of a parachute behind most planes).

Now you might say, “What about those rectangles on the bottom of the wing? Don’t they slow the plane down too?” Well those are called ‘flaps’ and although they might look like they slow the plane down, they actually push the air down instead of trying to catch and slow it. They do sort of slow the plane down too, but they are not a braking system (same thing with the wheels – they slow the plane down but obviously we don’t put the wheels down whenever we want to slow down).

If you look at the Boeing 777 above, you can see two thick airbrakes near the body of the plane and then three more further out on the other side of the engine. Although they all act as ‘airbrakes’, only the two thick ones are called air brakes. The others are called ‘spoilers’ and they are usually only half opened to slow the plane down a little bit (next time the pilot says “we’ll be starting our descent soon”, have a look and you might see them). This is done in the air, and when the plane touches the ground they open up fully.

This video is from a 777 and shows the airbrakes on landing. If you watch the whole video, you can see that crazy square next to the flaps moving up and down. It’s called a flaperon (or an inboard aileron) and you can see every time it moves up, the airbrakes kinda open but then they don’t. That’s called a spoiler roll (which is performed by – wait for it – roll spoilers) and I talked about it in Lachie Smith’s answer to How can the B2 bomber be flown without a vertical stabiliser (rudder)? if you’re interested.

Another thing about air brakes (I specifically chose the 777 for this reason because that aircraft highlights it) is that you’ll notice the airbrakes open at different times. This is to slow the plane gently instead of just fully throwing them all up. This lets the pilots have more time to softly put the nose down, and also means the main touch is softer (and makes people less scared, but that’s a story for another day).

Anyway, we’re onto a second braking system.

Reverse thrust

Reverse thrust is – wait for it – when the direction the thrust is going gets – ready – reversed. They don’t tend to get too creative with naming in aviation.

This is done by having little panels slide in behind the engines, which forces the air to turn around. This, again, makes the plane slow down.

If you’re interested, I highly recommend you read Lachie Smith’s answer to Why don’t airplanes go backward? to learn more about rev thrust.

Here’s rev thrust in action.^

Reverse thrust is good, but you can see in the video that the airbrakes are deployed a lot earlier than it. Both are still after the gear touches the ground, but the reverse thrust is usually after the front wheel touches.

Next, we have a braking system that isn’t actually used.

Ground (tyre) brakes

Ground brakes (formally called gear or tyre brakes) are probably the easiest to wrap your head around.

Essentially, they’re the same as the brakes in your car; they make it harder for the wheels to turn.

Gear brakes are usually not used in landing, as they can actually be damaged at high speeds (please watch this video):

This is a video of an A380 brake test at landing speed. “What’s burning?” you might ask. It’s metal. That is literally metal that is so hot that is burning. Do you know how hot metal has to get before it burns? Crazy stuff.

Gear brakes are instead used to slow the plane when it is taxiing, parking, or stopping at low speeds. Not only does this prevent the brakes from breaking (get it?), but airbrakes only work at high speeds and reverse thrust can actually destroy things like glass panels and airport workers (as well as using a lot of fuel and reducing the lifetime of the engine).

So here’s how things play out:

1. The main wheels touch down
2. Air brakes come up
3. Reverse thrust comes on
4. Front wheel touches (can be before reverse thrust)
5. Plane slows to 80 knots
6. Reverse thrust is stopped (not needed anymore)
7. Plane slows to about 30–40 knots
8. Air brakes retracted (not needed anymore)
9. Plane either coasts down to 20 knots or light gear brakes are applied
10. Plane taxies to gate
11. Plane uses gear brakes to stop at the gate

And that’s how you land a plane!

I’ll attach a video of a cockpit landing, usually you can hear the ‘copilot’ say when to do stuff like “speed brakes up”, “80 knots” etc.

Daniel Bednar raised an interesting point about autobrakes, which I forgot to mention. Autobrakes are when the gear brakes are lightly applied (or severely applied depending on the setting) and also help to slow the plane down. Sorry for the confusion.

Thanks to, among other people, Sebastian Lender for correcting me about the gear brakes. You can read more in the comments if you are interested.

Source: Quora