5 Most Common Aircraft Flap Types (Explained by a CFI)

5 Most Common Aircraft Flap Types (Explained by a CFI)

By Jillian C. Novak, CFI

As a student pilot, you've probably already heard your instructor talk about using flaps during takeoff, landing, and sometimes even during slow flight practice. But have you ever wondered how different flap types actually work, and why aircraft manufacturers choose one design over another?

In this post, I’ll walk you through the five most common types of aircraft flaps, how they function, what kinds of aircraft you’ll find them on, and the pros and cons of each—just like I would if we were sitting in a ground school session together.

Let’s get into it by first talking about what flaps are.

What Are Flaps?
Flaps are movable surfaces on the trailing edge of an airplane’s wings that can be extended downward to change the shape of the wing during flight. When deployed, they increase the wing’s lift and drag, allowing the airplane to fly safely at slower speeds. This also allows the plane to make a steeper descent without pointing the nose down and speeding up to unsafe airspeeds.

How Do Flaps Work?
When flaps extend, they increase the camber (curvature) of the wing, which boosts the amount of lift the wing generates. Some flap types also increase the surface area of the wing. At the same time, flaps create extra drag, which helps slow the airplane down.

Why Do Aircraft Need Flaps?
Flaps are used mainly during takeoff and landing—the phases of flight where slower speeds are necessary.

  • On takeoff, flaps help the airplane become airborne sooner by increasing lift.
  • On landing, flaps allow the airplane to descend more steeply and at a slower speed, making landings safer and shorter.

Now, let's get into the 5 most common types of flaps:

 

1. Plain Flaps

How They Work:
The plain flap is the simplest design. It’s a section of the wing’s trailing edge that pivots downward on a hinge. By increasing the camber (curvature) of the wing, it produces more lift—at the cost of additional drag.

Common Aircraft:
You’ll find plain flaps on many older or basic training aircraft. The early Cessna 150s and Piper Cubs are good examples.

Pros:

  • Simple design and easy to maintain
  • Lightweight
  • Good for basic flight training

Cons:

  • Not very efficient at increasing lift compared to modern designs
  • Generates a lot of drag relative to the amount of lift gained

2. Split Flaps

How They Work:
Split flaps are located on the lower surface of the wing. When deployed, only the bottom portion of the wing’s trailing edge drops down, creating significant drag while adding moderate lift.

Common Aircraft:
These were used in many WWII-era aircraft like the Douglas DC-3 and early warbirds, and you might see them on some experimental or vintage aircraft today.

Pros:

  • Creates substantial drag—great for steep approaches
  • Adds lift while keeping upper wing surface mostly undisturbed

Cons:

  • High drag penalty
  • Limited lift improvement compared to more advanced designs

3. Slotted Flaps

How They Work:
Slotted flaps are like plain flaps, but they include a slot or gap between the flap and the wing. When extended, air flows through the slot and re-energizes the boundary layer over the flap, delaying airflow separation and allowing greater lift with less drag increase.

Common Aircraft:
Extremely common in general aviation—many Cessna 172s, 182s, and even larger commercial aircraft use slotted flaps.

Pros:

  • Excellent lift-to-drag balance
  • Great for short-field performance
  • More effective than plain or split flaps

Cons:

  • Slightly more complex than plain flaps
  • Can be heavier and require more maintenance

4. Fowler Flaps

How They Work:
Fowler flaps not only pivot downward but also slide rearward on tracks, increasing wing area and camber at the same time. This dramatically improves lift while keeping drag relatively moderate until full extension.

Common Aircraft:
You’ll find Fowler flaps on higher-performance general aviation aircraft and light twins. 

Pros:

  • Greatly increases lift and wing area
  • Very effective for takeoffs and landings on short runways

Cons:

  • Mechanically complex
  • Heavier and more costly to maintain

5. Double or Triple-Slotted Flaps

How They Work:
These flaps use multiple panels that deploy in stages with slotted gaps between them. As each segment extends, it further increases wing area and camber, and airflow through the slots keeps the boundary layer attached.

Common Aircraft:
Primarily used in large transport and airliner aircraft such as the Boeing 737, Airbus A320, and larger jets that require high lift at low speeds.

Pros:

  • Maximizes lift generation
  • Critical for large aircraft operating at high weights and low approach speeds

Cons:

  • Extremely complex
  • Heavy and maintenance-intensive
  • Not used in general aviation due to complexity and weight

So, Why Do Flaps Matter to You?

As a student pilot, understanding flaps isn't just about checking a box on the knowledge test. It’s about controlling your aircraft more precisely, especially during takeoff and landing phases. Knowing how different flap types behave can help you understand why your aircraft performs the way it does—and what to expect when you fly other airplanes in the future.

While most training aircraft use either plain or slotted flaps, you’ll eventually encounter more advanced designs as you move into high-performance aircraft. By learning the fundamentals now, you’ll be better prepared for every stage of your flying journey.

By Jillian C. Novak, CFI

Northstar Aviation References brings you the Pre-Tabbed ASA FAR/AIM, DIY tabs for your FAR/AIM and other pilot resources so that you can more easily study the regulations that form the foundation of your flying career or hobby. Have any questions? Check out our FAQs page or contact us. Check out other blog posts here.

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