Uplifting Effects

High-lift devices are enhancements or additions to an aircraft’s wing which serve to increase lift. They may be a fixed component, or they may be a moveable mechanism. That’s the technical description, but let’s look at what that practically means. And we will find that as is the case with many aspects of aviation, there are some blurry lines, as some components may not strictly fit the text book definition.

Flaps

Flaps are probably the most obvious addition to a wing to increase lift. Basic Aeronautical Knowledge teaches us about the basic theory of flaps, but digging deeper, there are many different types of flaps. Some are not common in GA or recreational aircraft, but they are nonetheless, very interesting. The blown flap is one such example; it’s a flap which has air blown across the top of it through nozzles (internal) or jet blast (external) to shape the airflow over the rear of the wing. The Lockheed F-104 Starfighter has internal blown flaps, but because of the maintenance effort required for the pipework and nozzles, it remains uncommon.

The RAAF’s Lockheed C-17 Globemaster III has lower surface externally blown flaps, where the exhaust efflux from the four engines slung beneath the high wing is blown through the trailing edge flaps. This arrangement is one of the features which gives the C-17 good short field performance.

The types of flaps most likely to be seen at a