What are Aircraft Altimeters?

An aircraft altimeter is a common instrument used in aviation operations, playing an important role in ensuring safety and efficiency during flight. This instrument is specifically designed to measure an aircraft’s altitude, which is the distance between the vessel and sea level. By providing accurate altitude readings, altimeters enable pilots to optimally navigate the skies by adhering to altitude restrictions, maintaining proper separation from other aircraft, and ample clearance from ground obstructions and landforms. In this blog, we will provide a brief overview of altimeters, covering the basics of common types to help you familiarize yourself with these important flight instruments.

There are several types of altimeters used in aviation, each with its unique operating principles and applications. The most common type is the barometric altimeter, which functions based on the principles of atmospheric pressure. Put simply, atmospheric pressure decreases the higher an aircraft ascends, and a barometric altimeter serves to measure this change in pressure to calculate altitude. The instrument generally features a type of barometer that is calibrated to convert pressure readings into altitude values, such as using mercury within a tube that rises alongside increases of atmospheric pressure to obtain measurements. In order to facilitate proper readings across different regions, pilots must adjust their barometric altimeter settings to account for local atmospheric pressures, which is also referred to as the QNH. This adjustment is crucial, because variations in atmospheric pressure as a result of weather conditions can significantly affect instrument readings.

In addition to standard barometric altimeters, modern aircraft are often equipped with encoding altimeters. These devices combine the traditional barometric altimeter design with an encoding system that transmits altitude information to air traffic control (ATC) via an aircraft’s transponder. The encoded altitude data is extremely beneficial for controllers in their duties of maintaining situational awareness in controlled airspace, as it allows them to track an aircraft’s altitude electronically while providing any necessary instructions to ensure safe separation from other aircraft and proper heading. With this feature, encoding altimeters become especially valuable in busy airspace where accurate altitude information and ATC data access is critical for upholding safety.

Another popular type used in aviation operations is the radio altimeter, also known as a radar altimeter. Unlike barometric altimeters, these instruments measure altitude values above the ground rather than above sea level. To obtain measurements, radio waves are sent from the aircraft to the ground below, the instrument calculating distance by measuring the amount of time it takes for signals to bounce back to a receiver. Radar altimeters are particularly useful during low-altitude flight operations where having accurate measurements is crucial, such as during landing approaches. While radio altimeters may be found in various fixed-wing aircraft, they are also common in helicopters, which often operate at low altitudes where barometric altimeters may not provide the most accurate readings.

The radio altimeter antenna is a crucial component of a radar altimeter system, being the element that is responsible for transmitting and receiving the signals used to calculate altitude. In terms of placement, the antenna is typically mounted on the underside of an aircraft’s fuselage for unobstructed signal transmission to the ground. As the antenna will regularly face wear and tear over time, it is important that proper maintenance and calibration is carried out to uphold accuracy and reliability of readings.

Understanding the differences between each type of altimeter is important for pilots and aviation professionals, as all provide unique advantages depending on the type of aircraft and the flight operations it carries out. For instance, while barometric altimeters are ideal for high-altitude, en-route navigation, radar altimeters prove indispensable during landing approaches and low-altitude maneuvers. Additionally, the integration of encoding altimeters with transponders enhances flight safety by ensuring that altitude information is accurately communicated to air traffic control, which can be paramount for commercial operations.

In summary, aircraft altimeters are essential instruments that provide pilots with the critical altitude information that is necessary for carrying out safe and efficient flight operations. For those seeking high-quality aircraft altimeters and other aviation parts, ASAP Airplanes offers a comprehensive selection of products to meet the needs of aviation professionals across the industry. We currently feature popular part numbers like 519-28702-552 from Kollsman IDC and others, everything being offered with competitive pricing and timely fulfillment. If you take interest in any listings, fill out and submit a Request for Quote (RFQ) form through our website with as much information as you can regarding your needs. Within 15 minutes of us receiving and reviewing your submission, a member of our staff will be in touch to provide customized purchasing options for your consideration. See why so many steadily depend on ASAP Airplanes for aircraft instrumentation and more when you get in touch.