If you ever have had a window seat when flying on a large passenger jet, it is very likely that you have noticed some large panels on the wing, right above the flaps. If you have paid proper attention, you might also have noticed that they open slightly upon final approach, and then open up fully once the airplane is down on the ground.
These devices are called “spoilers”, and in this article, we’ll explore how they work, and why pilots use them.
So, how do spoilers work?
Spoilers work by deflecting the flow over the wings upwards, to slow the aircraft down upon approach and during landing. Most of the time they are opened partially during landing, and then extended fully upon touchdown. However, spoilers are also used when rolling the aircraft in mid-flight, as a substitute for ailerons.
In essence, the main objective when using spoilers is to decrease lift and speed. This is done by effectively stalling a small part of the wing, which means that some of the wing’s lift is lost. In that regard, spoilers are quite different from slats or flaps, that serve to increase lift at the cost of speed.
This means that spoilers become the perfect tool to increase the rate of descent without increasing the speed of the aircraft.
As a comparison, using flaps would also serve to slow the aircraft down, but it would generate extra lift, and keep the aircraft from losing altitude.
What Are Spoilers: A Closer Look
Spoilers are devices on the wing that when raised reduce lift and speed by stalling a portion of the wing. They are used both during landing and when banking the aircraft in-flight. However, they are only raised to their fullest during landing.
Distinguishing the various parts of the wing from each other can be quite hard if you haven’t received a proper introduction to how a wing is constructed.
So, where on the wings are the spoilers are located?
The spoilers are typically located right above the flaps, in the middle section of the wing.
They are raised upwards when activated, and when not used, they integrate nicely with the wing.
How Spoilers Are used During Flight: From Take-off to Landing
Spoilers generate downforce on the wings and can be used in cases where the pilot wants to descend rapidly without using speed brakes such as flaps, or changing the thrust settings.
Let’s look a little closer at the various uses of spoilers during take-off, flight, and landing!
Since spoilers are used to slow an aircraft down, you might think that it would we unwise to activate them during take-off. After all, you want to gain as much speed as possible to get off the runway and then quickly ascend to the skies.
Well, spoilers can be used very discreetly during takeoff as well. Their main function at this stage is to counteract roll. This is especially utilized during strong crosswinds, where the spoiler facing upwind will be raised somewhat to reduce the lift on that wing, effectively keeping the airplane from rolling.
In modern aircraft, spoilers are often raised automatically with the ailerons, if the conditions are right. This is to counteract adverse yaw as the ailerons are used.
As mentioned, spoilers can be used together with the ailerons to prevent the plane from rolling, and counter adverse yaw at high speeds.
They can also be used to bank the aircraft. The pilot simply deploys the spoiler on one wing which causes it to drop. This makes the plane bank in the direction of the dropped wing.
When used to bank the aircraft, spoilers are often referred to as “spoilerons”.
In addition to the above situations, spoilers can also be used to quickly bring an aircraft down from high altitudes. This could be done in cases when, for instance, air traffic control demands a quick change of altitude, or if the airplane loses cabin pressure.
Why Do Pilots Use Spoilerons Instead of Ailerons?
But why doesn’t the pilot just use the ailerons to bank the aircraft?
Well, one of the reasons is that, at high speeds, the ailerons will put significant stress on the wings when used, as they essentially are twisting the whole plane structure. This is further exacerbated by the fact that they are placed so far out on the wing.
To decrease stress on the airplane, spoilers can be used instead. As they are mounted closer to the fuselage, the airplane will twist less and they will make the airplane roll with much less stress on the wings and fuselage.
Upon approaching the runway, spoilers play mainly three roles, namely:
1. Making the airplane slow down
2. Making the airplane descend at a quicker pace
3. Both the above
Many airports around the world have a tight schedule with airplanes taking off and landing every minute. In such cases, ATCs naturally want the traffic to flow as effectively as possible, and will ask airplanes to come in at relatively high speeds. This means that the airplanes must be able to slow down quickly before and after hitting the runway.
Another aspect is that many airports are located close to densely populated areas that must be respected. Therefore the ATC is likely to require a quite quick and steep rate of decline, to lower noise levels.
Spoilers help in both regards, as they will facilitate a fast deceleration and quick altitude drop at the same time.
Upon touchdown, the spoilers will be deployed to their max. This serves two functions:
- It slows down the aircraft by created drag on the wing.
- it remove the remaining lifting forces on the wing by stalling it. This causes the airplane to have its weight fully resting on the landing gear, ensuring that the brake system can be used to its fullest to slow down the aircraft.
In case the spoilers aren’t deployed during landing, the wings will carry more of the plane’s weight as it rolls down the aircraft. This means that the pilot would have to wait longer to use full brake force, effectively increasing the time it would take for the airplane to grind to a halt.
Ground Spoilers VS Flight Spoilers: Are They Different?
As we have mentioned, spoilers can be used both in-flight and during take-off and landing.
What we haven’t looked into is that there are two types of spoilers, namely:
- Ground spoilers: These are only deployed when the aircraft’s weight rests fully on the landing gear, such as during aborted takeoffs and landing. The ground spoilers are the ones closest to the fuselage.
- Flight spoilers: These are used during flight AND after touchdown, and are located farther away from the fuselage.
Even though there are two types of spoilers, they are typically mounted in a line on the wing. Typically, the pilot doesn’t have to select which ones to use, as it’s taken care of by the airplane itself.
Speed Brakes VS Spoilers: What’s the Difference?
Many people confuse speed brakes with spoilers, but the truth is that they are quite different from another.
The main difference between spoilers and speed brakes is that spoilers are designed to decrease lift and speed by stalling a small part of the wing, while speed brakes only decrease speed.
In addition, speed brakes are smaller than spoilers and are mostly fitted on smaller high-performance airplanes. Mounted on the top of the wing, these serve to reduce speed but leave lift mostly untouched.
On quite spectacular speed brake design is that found on airplanes like BAE 146. Here the tail section unfolds into two protruding brakes that create drag and slow down the aircraft.
Other Brake Systems Found on Aircraft
Spoilers aren’t enough to stop a plane on the runway. In order to get an airplane to grind to a halt, several braking systems are involved.
Let’s take a quick look at two common braking systems!
Reverse thrust is when the direction of the air that comes out of the engine is reversed, to slow down the aircraft right after touchdown.
If you ever have seen a jet engine open when landing, it’s the reverse thrust mechanism that kicks in.
Flaps are found on the trailing edge of the wing and extend downwards when activated. Their main purpose is to generate more lift at lower airspeed (thus lowering the stall speed).
However, when used more aggressively, they will start to generate a lot of drag, which will prepare the aircraft for landing and takeoff by slowing it down.
If you are interested to know more about how airplanes slow down, you find more information in our article about how airplanes slow down in mid-air and on ground.
- Spoilers are control surfaces that are mounted on the wings. Their main role is to decrease the lift and speed of the aircraft.
- Spoilers are used both in-flight and during takeoff and landing. However, they are used somewhat differently in all three cases. One major difference is that they are only unfolded completely during landing, when they are used to remove the lift from the wings and ensure that the wheel brakes can be activated to their fullest.
- When spoilers are used to bank an airplane, they are called “spoilerons”
- Spoilers can be divided into ground spoilers and flight spoilers, where the latter is used in-flight and during landing, while the former is used only in-flight.
- Spoilers and speed brakes are distinctly different from another in that the former removes lift and reduces speed, while the latter only is designed to reduce speed.