On an airplane, what are spoilers for, what do they look, and what is the point of it?

Question

On an airplane, what are spoilers for, what do they look, and what is the point of it?

Answer 1

Spoilers are hinged panels in the upper surface of the wings on airliners that are so equipped.  Below a certain speed, the spoilers can be "deployed," or hinged upward, to disrupt ("spoil") the smooth flow of the boundary layer of air over the upper surface of the wing.

Spoilers dramatically reduce the lift of the wings, allowing the crew to decide on a flight profile that is more to the liking of Air Traffic Control, because they can remain at a higher altitude for a longer time and descend more steeply when near the destination airport.

Gliders also use spoilers to allow them to descend sharply to get into the intended landing field, as they do not have the ability to "go around" and try again if they overshoot.

Also, some advanced airplanes use differential spoilers (operate oppositely on opposite wings) instead of ailerons for roll control.

Answer 2

Better aerodynamics

Answer 3

Spoilers are mechanical (usually hydraulically actuated, electrically or mechanically activated) secondary control surfaces on the tops of wings.

What are spoilers for?

They "spoil" the lift and provide drag by directing airflow up... using Newton's First Law (for every action there's an equal and opposite reaction), the airflow directed up and the air hitting the spoiler head-on will push the plane down and backwards. It also breaks up the flow of air over the wing.  

You want this for several reasons:

1. Decrease altitude without increasing airspeed

2. Decrease lift (helps stick to the ground the second you touch down)... you'll see them deploy.

3. Slow down (once on the ground) to minimize ground roll

Here is a picture of some spoilers (the things deployed up) on a 737 that just landed.  

http://upload.wikimedia.org/wikipedia/co...

Here's a quick analogy to the spoilers on a car... when a car moves at high speeds, the faster moving airflow over the car (put a piece of string next to some running tap water to see this effect) pulls the car up.  This creates unwanted lift on a car that decreases traction on the road and detereorates handling.  On rear-wheel-drive cars, spoilers are installed to "spoil" the lift, just like on an airplane.  They provide downward force to improve traction of the REAR wheels.  Here's a picture.

http://damox.com/cars/thumbs/Honda/Honda...

Come on you guys give this kid some better answers here...

Oh and one more thing... spoilers can be combined with ailerons to form SPOILERONS... if the one on the right wing goes up, the airplane turns to the right, and vice versa... multipurpose control surfaces.

Answer 4

While touched upon, the most important use for spoilers is the ability to go down and slow down at the same time. Most non-jet pilots as well as non pilots period do not recognize the difficulty in slowing down a jet. The engineers make extreme efforts to design a clean airplane with as little drag as possible... and they are quite good at it.

You may climb out with 90% -100% power... but once you reach your cruising altitude, you only need about 20% thrust to keep going. You have so much available, that you must constantly keep pulling back the throttles during the trip because the airplane keeps speeding up as you burn off fuel which makes you lighter. Boston to Paris in an L-1011 can burn 100,000 lbs of fuel... yes.. that is 50,000 TONS of fuel...

You are already at max speed when you need to start down to a lower altitude, and going down hill can cause you to pick up some speed.. so even with the throttles closed to idle... you may be bumping up against your max speed restriction. What a waste! you burned all that fuel getting up there.. and now you have to put on the brakes to come down... so you deploy the spoilers (commonly called "boards") which effectively defeat lift and allow the airplane to come down with a higher vertical rate, without increasing speed.

The L-1011 was the first airplane to use a concept called DLC or Direct Lift Control... and when you were in the DLC speed range, the spoilers would reset to a null postition of 7 degrees up.... NOW.. you could use the YOKE to lower the aircraft with OUT pitching the nose up and down.. something the passengers and f/a's REALLY appreciated. It worked this way...  with the spoilers set to a new "neutral" postition of actually deployed 7 degrees, when the pilot pushed forward on the yoke to increase the descent rate...  instead of pitching the nose over, the spoilers *increased* their angle causing the airplane to sink faster, without increasing speed...  the reverse was true... if it appeared that you were coming down too quickly... and the pilot pulled back on the yoke, the spoilers would retract towards a normal "clean" position, resulting in a slower descent rate. It was brilliant and worked fantastically. The pilots were able to "sink" the airplane without changing the pitch of the airplane, and for the attendants pushing those carts back to the tail... it was so much easier than having to push them "uphill". It was not uncommon to have them tell you when they were ready for the "stampede" and you could pitch the airplane up slightly and allow them to roll the carts back to the galley elevators downhill...  they loved that... but it had to be done before you started the descent.

Answer 5

Spoilers aka "Lift Dumper" CAN be used to slow a airplane down, but isn't what it is designed for. Spoilers are make to decrease lift, which is why they are used when the airplane touches down. Spoilers can also be used for a quicker faster descent.

http://homepage.mac.com/lesposen/iblog/B...

Answer 6

They redirect air flow for flight control.  Flaps.

Answer 7

In aeronautics a spoiler (sometimes called a lift dumper) is a device intended to reduce lift in an aircraft. Spoilers are plates on the top surface of a wing which can be extended upward into the airflow and spoil it. By doing so, the spoiler creates a carefully controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. Spoilers differ from airbrakes in that airbrakes are designed to increase drag while making little change to lift, while spoilers greatly reduce lift while making only a moderate increase in drag.