VC speed

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The correct title of this article is V_C speed. It features superscript or subscript characters that are substituted or omitted because of technical limitations.

This article is about an aircraft velocity. For other uses of VC, see VC.

The V_C of an aircraft is the V speed which refers to the velocity of cruising. V_C is within the green arc on many airspeed indicators. This speed varies is different for each aircraft model.

V_C is also called the design cruising speed or the optimum cruise speed – the latter being the speed giving the most velocity (i.e greatest distance/time) from a litre of fuel, usually utilising 75% power at Maximum Take-Off Weight (MTOW) and about 1.3 times the maximum lift-to-drag ratio (L/D) speed – V_br above. The speed and power required decrease as the aircraft weight decreases from MTOW.

For normal category aircraft FAR Part 23 specifies a minimum design cruising speed (in knots) based on the wing loading of <math>33\sqrt{\tfrac{W}{A}}</math> (weight in pounds divided by wing area in square feet). For the utility category, the minimum design cruising speed is <math>36\sqrt{\tfrac{W}{A}}</math>. Many ultralight aeroplanes are unable to comply with the FAR part 23 requirement for a minimum design cruising speed.