AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

What Airspeed Is Best?

Although it might be intuitive to think that aircraft aim to fly at the highest speeds possible throughout flight, this is not the case in practice. In fact, pilots constantly monitor and adjust airspeed to optimize for maximum efficiency and safety. Determining proper airspeed is equally complex as it is important, which is why it is necessary to review some key concepts first, including how airspeed and efficiency are measured. In this blog, we will discuss everything you need to know about airspeed optimization, highlighting its importance, measurement, and determination criteria.

When pilots read an airspeed off of the dial, they receive information about the indicated airspeed (IAS). If measured at sea level with standard pressure, the IAS would resemble the true airspeed (IAS). However, as density decreases with altitude, so does the IAS in relation to the TAS. As a result, a value named "calibrated airspeed" (CAS) is used to lessen the gap between IAS and TAS, also serving as a reference point for various pedestral aircraft controls. Airspeed is most commonly measured in knots, although various professional societies, including the ICAO, recommend using kilometers per hour (km/h).

One of the most critical topics for pilots to commit to memory is the V speeds, which is a list of standardized and regulated speeds for different performance requirements. Although the complete list encompasses over 30 designations, we will only cover some of the most common.


V1 is an aircraft-specific value that determines the maximum speed at which a takeoff may be aborted. Speeds faster than this may compromise the plane's ability to come to a safe and complete stop.


Most of the V speeds are tabulated to provide the pilot with relevant information in the case of an emergency. V2 represents the speed at which the plane can still climb if one engine were to fail upon takeoff.


For aircraft operating with flaps, V4 indicates the speed at which the flaps should be retracted.


Also known as maneuvering speed, VA is the airspeed at which the aircraft will stall without causing structural damage should its angle of attack suddenly increase.


Although aircraft might be faster or slower depending on its weight and atmospheric conditions, VC is the speed that the manufacturer recommends for cruising. This value is generally optimized for fuel efficiency and protection against sudden gusts of wind.


Often called the stall speed, VS is the minimum speed at which the pilot can still control the aircraft without stalling.


Although the landing gear are designed to withstand immense forces during extension, their operating threshold speed as determined through testing is listed as the VLE.


Clearly, there are numerous factors that come into play when determining optimal airspeed. These values have been rigorously tested by manufacturers to achieve best practices in a wide range of scenarios, making their implementation highly recommended. However, in order to establish a reference airspeed, it is necessary to ensure that all measuring devices are high-quality and in working order.

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