What is IAS on Boeing 737? (Indicated Airspeed)

The Indicated Airspeed (IAS) on the Boeing 737 is a critical measurement parameter that pilots use to maintain safe and efficient flight operations. It is the airspeed value displayed on the aircraft’s airspeed indicator, which is an instrument that provides real-time information about the aircraft’s velocity.

IAS is an important parameter as it indicates the speed of the aircraft through the air. It differs from groundspeed, which is the speed of the aircraft relative to the ground. The IAS is affected by various factors such as altitude, temperature, and air density, and it is crucial for pilots to monitor and adjust their speed accordingly to ensure a smooth and controlled flight.

How is Indicated Airspeed Measured?

The Indicated Airspeed is measured using pitot-static systems, which are an integral part of the aircraft’s instrumentation. These systems consist of two main components: the pitot tube and the static port.

The pitot tube is a small probe located on the exterior of the aircraft. It is designed to measure the dynamic pressure of the air flowing around the aircraft. As the aircraft moves through the air, the pitot tube captures the force exerted by the air and converts it into a pressure value.

The static port, on the other hand, is a small opening located on the side of the aircraft. It is designed to measure the static pressure of the air. This static pressure is unaffected by the aircraft’s motion and provides a reference value for calculating the airspeed.

The difference between the dynamic pressure captured by the pitot tube and the static pressure measured by the static port is used to calculate the Indicated Airspeed. This calculation takes into account factors such as altitude, temperature, and air density to provide an accurate representation of the aircraft’s speed through the air.

The Importance of Indicated Airspeed

Indicated Airspeed is crucial for several reasons:

1. **Flight Safety**: Pilots rely on the Indicated Airspeed to maintain safe flight operations. It helps them ensure that the aircraft is flying within its safe speed limits and prevent potential hazards such as stall or overspeed conditions.

2. **Engine Performance**: Indicated Airspeed is used in computing engine performance parameters. It assists pilots and engineers in optimizing the aircraft’s fuel efficiency by monitoring the engine performance at different airspeeds.

3. **Aircraft Systems**: Various aircraft systems and avionics rely on Indicated Airspeed for their operation. This includes systems such as autopilot, flight management computers, and flight control systems. These systems use the Indicated Airspeed as an input parameter to ensure smooth and precise control of the aircraft.

Overall, Indicated Airspeed plays a vital role in maintaining the safety and efficiency of Boeing 737 operations. It provides pilots with real-time information about the aircraft’s velocity through the air, enabling them to make informed decisions and adjustments during flight.

The Limitations of Indicated Airspeed

Although Indicated Airspeed is a valuable measurement parameter, it is important to note its limitations:

1. **Instrument Errors**: The Indicated Airspeed displayed on the airspeed indicator may not always be completely accurate due to instrument errors. These errors can result from factors such as instrument calibration, sensor malfunctions, or blockages in the pitot-static system.

2. **Wind Conditions**: The Indicated Airspeed does not account for wind conditions. It only provides the aircraft’s speed through the air, which means that the actual groundspeed can be higher or lower depending on the wind direction and speed.

3. **Altitude and Temperature Effects**: Indicated Airspeed is affected by changes in altitude and temperature. As the aircraft climbs to higher altitudes, the air density decreases, resulting in a decrease in Indicated Airspeed for the same true airspeed. Similarly, changes in temperature can impact the air density and, consequently, the Indicated Airspeed.

Despite these limitations, pilots are trained to understand and account for these factors when using Indicated Airspeed as a reference for their flight operations.


Indicated Airspeed is a crucial parameter on the Boeing 737, providing pilots with real-time information about the aircraft’s speed through the air. It is measured using pitot-static systems and is influenced by factors such as altitude, temperature, and air density. Pilots rely on Indicated Airspeed for safe and efficient flight operations, while also considering its limitations and potential inaccuracies caused by instrument errors and environmental conditions. Understanding and utilizing Indicated Airspeed correctly is essential for a successful and controlled flight experience on the Boeing 737.

For More: What is CWS on Boeing 737? (Control Wheel Steering)