VNE
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- The correct title of this article is VNE. It features superscript or subscript characters that are substituted or omitted because of technical limitations.
The VNE of an aircraft is the V speed which refers to the velocity that should never be exceeded. VNE is specified as a red line on many airspeed indicators. This speed specific to the aircraft model, and represents the edge of its performance envelope.
Exceeding VNE risks structural failure, because the aircraft is being with a less than acceptable structural safety factor for one or more components. The most common limitations are the risk of wing or tail deformation or failure, or for higher-speed aircraft, the onset of aeroelastic flutter. For these reasons, it is not safe to fly at or near VNE in turbulence or when abrupt control inputs are expected. In some aircraft, control input may be reversed at speeds above VNE (such as pulling the nose up actually causing the nose to go down). This is typically due to structural deformation of control surfaces and their attaching structures at such high speeds and is one factor in establishing VNE. No control reversals should occur under normal flight circumstances if the plane is operated under VNE.
In order to set VNE during the certification process, an aircraft manufacturer performs calculations and flight testing to determine the speed at which the first obstacle to safe flight occurs, even if the aircraft is unaccelerated and no abrupt control inputs are applied. This speed is then reduced to provide a safety margin.
A higher speed, Vd, or the designed diving speed of the airplane, is used only by experienced test pilots under testing conditions when the airplane is being certified. For obvious reasons, this speed is not typically advertised by the manufacters of aircraft, and should never be relied upon by pilots.
