Giveaway: May 2018

The winners for the April giveaway are in. Congratulations Howard and Amanda!

For May I want to get more planes out there in your hands so I am giving away 2 Cessna 172 Reality Expansion Packs from SimCoders. As usual, I will randomly draw someone from my mailing list to win the first 172, and then I will run it again to find our 2nd winner. Continue reading “Giveaway: May 2018”

How low can you fly?

How low can you legally go?

In very sparse areas, you can fly as low as you want but you must be high enough to make a safe emergency landing. 91.119(a)

If there is any kind of human presence, including people or property, then you must be at least 500 feet away from them or 500 feet above. This is pretty low. Use the ground elevation and your altimeter to determine your height above the ground. 91.119(c)

In most places there are people and structures spread out, so 500 feet above should be considered the limit. The 500 feet away rule really only applies over open water and truly empty areas of land. Continue reading “How low can you fly?”

6 Types of Flaps

Flaps are very useful for giving an airplane good handling characteristics at low speed. They are vitally important for giving fast planes the ability to go slow for takeoff and landing.

There are 6 types of flaps

  1. Plain Flaps
  2. Split Flaps
  3. Slotted Flaps
  4. Fowler Flaps
  5. Slots
  6. Slats

Plain Flaps

A simple hinge at the rear of the wing is used to make plain flaps. They are easy to design but they can’t provide much lift before the drag increases very significantly.

Since increasing drag is one of the purposes of a flap the performance is not too bad for landing. When taking off though, drag is not desired.

The reason this flap has so much drag is because the air from above the wing tends to separate and become turbulent when it has to flow downwards at such a steep angle. Think of it like a car on the highway having to make a sharp turn to stay on the road. This airflow separation is like that car spinning out because it can’t make the turn.

Turbulent airflow separation above the wing reduces lift.

Split Flaps

The split flap surface is actually below the wing and pushes down out of the bottom. It does provide some lift but it creates a lot of drag and is almost like a speed brake under the wing.

Slotted Flaps

This is the most common type of flap because it is relatively simple to design and build but provides a huge benefit over the plain flap. The slot created when the flap extends allows air to flow from under the wing.

This airflow provides a cushion for the air from on top of the wing to keep it from separating. It also flows along the top of the flap surface. These two benefits combine to create a lot of extra lift.

Fowler Flaps

Fowler flaps are complex but provide a lot of benefit. They act like slotted flaps opening up a channel for air, but they also slide outwards as depicted below. By sliding out from the wing they greatly increase wing area.

Put simply, they make the wing bigger. A bigger wing means lots of lift!

Most modern airliners use double or triple slotted fowler flaps. These have several flap surfaces that extend out from each other as the flaps are lowered creating a much larger wing with several slots for air to pass through.


This modification to the leading edge of the wing provides a channel of air that is pushed up over the wing and channeled towards the upper surface. At low speeds, this simple fixed device can increase the critical angle of attack (the angle at which the wing stalls). This means that the plane can fly much slower without stalling.


Slats are another type of leading edge flap. They slide down at low speeds and provide a large increase in lift like the fixed slot. The benefit of the slat is that it is retractable and won’t create extra drag at high speeds because it slides up into the wing surface.