Beyond the Runway: Airspeed Indicator

 Beyond the Runway is a new series which aims to induce more information and knowledge about the industry as a whole, exploring a plethora of topics that go beyond the headlines. Today's topic- the Airspeed Indicator.

The Airspeed Indicator (ASI) is a flight instrument which measures the aircraft’s speed relative to the surrounding air. Its main function is to provide the pilots an accurate and real-time airspeed reading. This helps in avoiding unsafe predicaments such as a stall or overspeed. It also assists in navigation and calculations, as it enables the pilots to calculate fuel consumption and climb rate.

The types of airspeed measured by the ASI include Indicated Airspeed, which is a direct reading, Calibrated Airspeed, which is correct for instrument errors, and True Airspeed, which is correct for altitude and air density. Groundspeed is the speed over the ground, as the name suggests, but is not calculated by the ASI.

Moving on to how ASIs work, the pitot tube measures the ram pressure while the static port measures the ambient pressure. The difference between these 2 readings moves a needle on the ASI dial, hence displaying airspeed.

In 2009, Air France flight AF447 suffered a failure of the ASI, due to the pitot tube icing at a high altitude. This gave inconsistent readings and eventually lead to confusion in the cockpit and the aircraft stalling. It was an Airbus A330 registered F-GZCP. After this, de-icing technology for ASIs improved and pilot training for unreliable airspeed readings was also enhanced.

By the DGCA’s regulations, all aircraft must have operational airspeed indicators.

Although simple in design and fundamentals, the Airspeed indicator is an imperative instrument for a safe and comfortable flight, preventing stalls and overspeed.