Since the world of aviation has so many acronyms, it can be confusing to distinguish important terms from one another, and V speeds are no exception. With “V” meaning “velocity,” V speeds are defined as the standard airspeeds that each aircraft can operate at while achieving the highest possible performance level within safety standards. That being said, V speeds are determined by manufacturers once they have performed test flights and have identified an aircraft’s limitations. The main focus of these test flights is to provide pilots with insight as to the best practices for the operation of the aircraft they are flying.
As previously mentioned, V speeds are standard speeds, meaning that you could find them on the airspeed indicator. With this in mind, pilots are required to be able to identify and read the V speeds that are displayed by the airspeed indicator. While different aircraft have different airspeed indicator designs, one thing remains the same: the information they all display is standard. For instance, the airspeed indicator utilizes a standardized code of colors to illustrate the V speeds that are most relevant for safety and performance. Meanwhile, numbered lines are used to represent the values of those speeds.
In dial indicators, there will be colored arcs. In aircraft models we see today, glass cockpits may be used where the code is represented by a colored bar. Nonetheless, the basic principle remains the same. Four main colors are used to represent varying speeds, those of which are white, green, yellow, and red. To better understand what each color means, we will outline the four categories below.
The main V speeds that are in the white range are VSO, VS1, and VFE. The white arcs or bars in any airspeed indicator represent the speed range for using flaps. VSO is defined as the stall speed in landing configuration, or with the landing gear and flaps fully deployed which is technically the same. The VSO can be identified at the lower end of the wire arc and is also known as the minimum steady flight speed. It is worth noting that this is the minimum speed at which an aircraft is controllable in landing configuration. VS1, on the other hand, is defined as the stall speed with the landing gear and flaps fully retracted, and it also defined as the minimum steady flight speed in a given configuration. It is often called the “clean” stall speed because it does not create any additional drag or turbulent airflow. In contrast, the maximum speed with flaps extended is called the VFE. Generally, it is defined as the Maximum Flap Extended Speed, which represents the limit for extending the flaps. Serious structural damage could happen if the flaps are extended beyond the limits of a given VFE and can be found at the top end of the white arc.
The green range on the airspeed indicator represents the speeds of normal operation and are denoted by VNO (Velocity of Normal Operation). However, the VNO does not encompass the entire green range and only refers to the top of the green scale. The top speed of the green range represents the maximum speed an aircraft can reach without compromising its integrity during cruise. The VNO also represents the flying limit within the FAA-certified range of wind gusts. Keep in mind that the yellow color after the green range represents a warning signal.
Yellow and Red
Yellow and red are going to be covered alongside one another since yellow is already a warning and red represents a final alert. The speeds in the yellow range are excessive for the aircraft, meaning that it has surpassed the maximum operating limit speed set by the VNO. The red range is called the VNE which is the “Velocity that you Never Exceed.”
Other V Speeds
Other than the V speeds defined above, there are a few others worth mentioning. For example, maneuvering speed or Velocity of Acceleration (VA) is the maximum speed an aircraft can go through when sudden or brusque movements take place without causing structural damage. It is worth noting that no aircraft should operate above the VA under turbulence or high wind gust conditions. Next, the maximum landing gear operating speed or Maximum Velocity for Landing Gear Operation (VLO) is used exclusively for retractable gear aircraft only. Other common V speed terms include the maximum landing gear extended speed or VLE, best rate of climb (VY), and best angle of climb (VX).
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