Drag – Is There Anything In The Air That Resists The Travel Of Aircraft?

Drag - Aviatorsbuzz

Is there anything in the air that resists the travel of aircraft? Invisible Resistance?

In aerodynamics, drag refers to forces that oppose the relative motion of an object through the air. Drag always opposes the motion of the object and in an aircraft, is overcome by thrust.

Types of Drag

There are many different types of drag. The most commonly encountered are:

  • Parasitic Drag, composed of :
    • Form Drag, which is the result of the aerodynamic resistance to motion due to the shape of the aircraft
    • Skin Friction Drag, which is due to the smoothness or roughness of the surfaces of the aircraft
    • Interference Drag, which may occur where surfaces with different characteristics meet (e.g. wing and fuselage)
  • Induced Drag, which is a secondary effect of the production of lift
  • Wave Drag, which comes into play when shock waves develop close to the surface of the aircraft in transonic and supersonic flight.

Drag and Airspeed

Parasitic drag increases with the square of the airspeed, while induced drag, being a function of lift, is greatest when maximum lift is being developed, usually at low speeds. The diagram below shows the relationship of parasitic drag and induced drag to each other and to total drag.

Relationship of Drag with Airspeed - Aviatorsbuzz
Relationship of Drag with Airspeed

There is an airspeed at which total drag is minimum, and in theory, this is the maximum range speed; however, flight at this speed is unstable because a small decrease in speed results in an increase in drag, and a further fall in speed. The further decrease in speed causes yet more drag and without the addition of thrust or initiation of a descent, could result in a stall or Loss of Control. In practice, for stable flight, maximum range is achieved at a speed a little above the minimum drag speed where a small speed decrease results in a reduction in drag.

DRAG - Aviatorsbuzz

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Ria & Kartik
Follow our TechTalks with Ria Maini and Kartik Bhatnagar, both commercial pilots, rated and endorsed on the A320. Although they recently stepped into their aviation career, nothing has stopped them from taking their knowledge to the next level, with successful experience in coaching on the subject of A320’s for aspiring pilots and a memory refresh for the experienced ones. Curiosity, passion for flying and avionics led them to start "A320 Trivia", and their endeavour has been to share their knowledge to benefit all aviation enthusiasts and pilots, and to highlight key dynamics of the versatile aircraft. You are welcome to share your valuable inputs and further enable this page, to be an expert guide/reference, polestar for all to follow. If you are interested in discovering new and mind boggling facts on the aircraft & technical general, catch up on our weekly blog!