An aircraft is one of the most advanced inventions. Today, aircraft manufacturers are more capable than ever of producing a safer and more reliable aircraft. However, there is one part of flying, which is often said to be the toughest; the landing. Although modern-day aircraft are capable of handling landings very well, there is almost some kind of uncertainty to it.
From the time the aircraft turns around and taxis to the active runway, everything seems normal. The consequent power-up of strong modern engines makes the aircraft capable of taking off, nowadays rather easily. The remaining part of the flight is comparatively challenging.
The possibility of experiencing bad weather, an engine failure, or strong winds is unpredictable. However, every aircraft has to somehow and somewhere touch-down safely. The main question remains: How does an aircraft stop after landing?
A modern-aircraft braking system
On any given modern aircraft, there are mainly three types of braking sources; ground spoilers, disc brakes, and thrust reversers. The three combined can provide the most potent braking effect post-landing. Although spoilers and wheel brakes are an integral part of any aircraft, thrust reversers are usually more common in airliners.
One of the most effective and logical ways of bringing an aircraft to rest is by first cutting off its supply of lift—spoilers on the top of a wing act as a hindrance to the streamlined flow of air. However, spoilers can have varied applications. They can be used to some extent to lower aircraft speeds at the time of descent and approach. This stage is called ‘partial deployment’ of spoilers.
After touching down, the spoilers take a fully vertical shape by standing straight and out of the wings. In many cases, an additional ground spoiler, which is closer to the fuselage, is used as well. However, there is only a bit that the spoilers can do. The main application of an aircraft spoiler is to cut the lift and provide some sort of a drag. The rest is done by disc brakes and reverse thrusters.
The wheel braking system is the most common form of braking on any given vehicle in the world. Unsurprisingly an aircraft has it too. Nevertheless, the braking system on any given aircraft is highly-engineered and sophisticated. The complexity of a disc-braking system is such that it is hard to explain it in few words.
Simply put, the disc braking system of a wheel is a part that is fixed and doesn’t rotate with the other part of the wheel. Just like a pad on any modern-vehicle, these stationary discs act as friction to the rotating part and cause it to either gradually stop or reduce its rotation speed.
Most-modern aircraft are nowadays equipped with autobraking systems controlled by the autopilot. Depending on the various aspects of landing, the level of the auto brake can be changed to get the desired effect. A lot depends on the length and the state of the runway. For example, it will take some tough braking to stop a B747 touching down on a wet runway at the speed of 290 km/hr.
Runway length is an essential factor too. Airports like Kai Tak, which had a really tough approach and a high possibility of crosswinds, required an aircraft to apply strong brakes to stop on its short runway. For this reason, most pilots nowadays have to prepare the autobraking system before landing. After the aircraft has slowed down to an extent, the pilots switch to manual braking.
Thrust reversers are a very common part of modern aircraft engines. The application of thrust reversers is more important in heavier aircraft. Some smaller aircraft like the BAE 146 still don’t find any use of thrust reversers. This might have to do with a combination of a strong braking system and effective spoilers. However, on a heavy passenger aircraft like an A330, thrust reversers are very crucial.
The working of a thrust reverser is easy to understand and very practical. It is the process of amending an already working engine. In modern high-bypass turbofan engines, more than 90% of air is sucked in and thrown out of the engines. After touch-down, all thrust reversers have to do is just change the direction of the air.
Instead of being pushed towards the back, the reversers pave a sideward opening to allow for the air to push forward. This creates an ‘opposite thrust’, and this helps the aircraft in stopping. Unlike the process of wheel braking, thrust reversers are mostly manual and applied after the aircraft has safely touched down.
There is more to a safe landing
A safe landing of an aircraft depends heavily on the braking system, however, not entirely. For a pilot to safely stop a plane, prior calculations and preparation need to be done. If an aircraft touches down at a very high speed, there is only a little the braking systems can do.
There are some aspects which have to be kept in mind:
- Aircraft weight: Even before an aircraft takes off, pilots are aware of the predicted landing weight. If the aircraft is too heavy, it might not be able to stop on a wet/short runway.
- Runway length: As discussed before, pilots have to keep in mind the available landing distance and threshold length to perform a safe landing. Flaps are often used to make an aircraft land easily on shorter runways.
- The approach: Approach is an equally important aspect. If the aircraft is not correctly aligned to the runway or is facing heavy winds, it might not stop after touching down.
- Runway type: Wet runways require special consideration as the aircraft can skid off.
All the above factors and the power of modern-day braking systems, have made aircraft landing safer than ever.
Which part of a flight do you prefer, landing, or take off? Let us know in the comments.