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Wing Spoilers: How Destroying Lift Helps You Fly

Olivier CABARET

Spoiler alert: while most control surfaces increase lift, not all of them do. And we'll prove it today with wing spoilers. Wing spoilers are actually pretty impressive, because they can do more than one job. In fact, they can do three, and here they are:

1) Spoilers Help You Slow Down And Lose Altitude

Spoilers destroy lift, but why exactly would you want them to do that? Just ask a glider pilot or airline pilot. Gliders and airliners are built to produce very little drag, which is great in most cases, except when you're trying to descend and slow down.

Gliders use spoilers during approach and landing. By extending spoilers, glider pilots can increase drag, lower the nose, and descend faster without significantly increasing airspeed. Check out the spoilers extending out of the wing in the animation below:

droneviking

Airliners use spoilers to their advantage as well. If you need to descend quickly, spoilers are often the answer to controlling your airspeed while you lose altitude. And if you're flying through icing conditions, you often times can't reduce your engines to flight idle, because you need to keep your anti-icing surfaces, which are heated with engine bleed air, hot. Again, spoilers increase drag enough for you to keep your engines producing sufficient bleed air, making life a little bit easier.

Wikipedia

2) Spoilers Help You Bank

Spoilers can also help your ailerons, or in some cases, completely replace them. These are sometimes called "spoilerons", and the animation below is a great example of them at work:

Jeffh737

There are a couple advantages to using spoilerons. First, when you have high speed airflow over your wings, using ailerons can actually generate so much force that your wings twist, causing your aircraft to bank in the opposite direction. And that's definitely not good.

But there's another benefit to spoilerons: they reduce adverse yaw in a bank. In normal aircraft, when you bank, the outboard aileron moves down, creating more lift, and more drag. But, when you use spoilers to roll, they generate form drag on the inboard wing. This helps keep your nose in line with the turn, which means you don't need to use as much rudder to stay coordinated.

3) Spoilers Help You Stop Faster On The Ground

The last benefit, and one that you see nearly every time you land in an airliner, is stopping quicker on the ground. When you land, your wings are still generating lift, which means there isn't much weight on your landing gear, and your braking effectiveness is reduced.

Jeffh737

When airliners touch down, they detect when the wheels hit the pavement, and they deploy ground spoilers. The ground spoilers do two things: put the full aircraft's weight on the wheels, and create form drag. And when they pop up, the airliner can stop in a much shorter distance.

Two Main Spoiler Designs

There are two main types of spoilers: vertical, and hinged. So what's the difference, and when are they used?

Vertical spoilers are typically used on smaller aircraft, like gliders. When vertical spoilers are raised, they disrupt airflow over the aft part of the wing. But when they first start to raise, they aren't very effective. The further they extend, the more effective they are, which means they're good for dumping altitude and airspeed, but not so great for controlling roll. They also have another limit: the thickness of the wing. Simply put, you can't fit a tall vertical spoiler into a thin wing.

Hinged spoilers are much more common, and they're typically what you see on airliners. They're more effective in small deflections, which makes control inputs more responsive. And, you can hinge a big spoiler onto the wing of an airliner.

One Design, Three Benefits

Spoilers may be simple, but they can do a lot: descend, roll, and stop your aircraft. Who knew that one flight control surface could be so useful?

Colin Cutler

Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.

Images Courtesy:

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