FLIGHT LEVEL Meaning and
Definition
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Flight level is a term used in aviation to denote a specific altitude or vertical position of an aircraft in the atmosphere. It is a universally recognized standard that allows for consistent communication and identification of aircraft at different altitudes. Flight levels are typically measured in hundreds of feet above a reference level known as the standard pressure level.
The concept of flight levels is based on the fact that atmospheric pressure decreases with increasing altitude. To account for this variation, a standard reference pressure of 1013.25 hectopascals (hPa) or 29.92 inches of mercury (inHg) is established. Each flight level represents an altitude where the atmospheric pressure is equal to this standard reference pressure.
Flight levels are often represented by three digits, with the last two digits rounded to the nearest 100 feet. For example, flight level 350 represents an altitude of 35,000 feet. To ensure accurate and efficient altitude reporting, pilots set their altimeters to the standard reference pressure when climbing or descending through a transition altitude, which is the altitude where the local pressure falls below the standard reference pressure.
Flight levels are commonly used for aircraft operating in controlled airspace, such as during instrument flight rules (IFR) operations. By assigning specific flight levels to different aircraft, air traffic control can maintain safe vertical separation and facilitate efficient traffic flow. Flight levels ensure consistent and precise altitude reference, enhancing flight safety and minimizing the risk of mid-air collisions.
Etymology of FLIGHT LEVEL
The term "flight level" originated in the field of aviation to refer to specific altitudes above the standard datum plane (usually measured in feet or meters). The etymology of the term is based on the standard practice of assigning aircraft altitudes according to a standardized system known as "pressure altitude".
Pressure altitude is determined by measuring the atmospheric pressure at a specific location and then converting it into an equivalent altitude. This allows aircraft to operate at designated altitude levels despite variations in atmospheric pressure at different locations and times.
In the past, altimeters were mainly calibrated to display altitude in terms of atmospheric pressure. However, to ensure accurate and consistent altitude reading for aircraft operating beyond a certain altitude, it was necessary to establish a reference plane where atmospheric pressure would always be constant. This gave rise to the concept of the "standard datum plane".
