You are here:

Aerospace/Aviation/Altimeter Flight instrument.


Dear Laura

Do the altimeter Flight instrument indicates with accuracy the plane Altitude from the ground level to the pilot?.

How does the Altimeter Flight instrument measure the Altitude?.


The altimeter is typically used to indicate the airplane's altitude above sea level, not necessarily above ground level, for aircraft flying below 18,000' in the USA. Above 18,000' in the USA, airplanes all use the altimeter to set one standard barometric pressure, and then that is what the altimeter indicates the height by reference to.
A good article explaining how the altimeter actually works is found here:
Here is an excerpt from the article:
"In aircraft, an aneroid barometer measures the atmospheric pressure from a static port outside the aircraft. Air pressure decreases with an increase of altitude—approximately 100 hectopascals per 800 meters or one inch of mercury per 1000 feet near sea level.

The aneroid altimeter is calibrated to show the pressure directly as an altitude above mean sea level, in accordance with a mathematical model defined by the International Standard Atmosphere (ISA). Older aircraft used a simple aneroid barometer where the needle made less than one revolution around the face from zero to full scale. This design evolved to altimeters with a primary needle and one or more secondary needles that show the number of revolutions, similar to a clock face. In other words, each needle points to a different digit of the current altitude measurement.

Modern aircraft use a "sensitive altimeter,". On a sensitive altimeter, the sea-level reference pressure can be adjusted with a setting knob. The reference pressure, in inches of mercury in Canada and the US, and hectopascals (previously millibars) elsewhere, is displayed in the small Kollsman window,[5] on the face of the aircraft altimeter. This is necessary, since sea level reference atmospheric pressure at a given location varies over time with temperature and the movement of pressure systems in the atmosphere."


All Answers

Answers by Expert:

Ask Experts


Laura Laster


I can help with questions about aviation disasters, aircraft operations especially general aviation and King Air information, aviation safety, and education questions on how to get into an aviation career. I can also answer general aviation questions as I am a commercial multi-engine pilot. I cannot answer questions about flight training or MBA schools in countries other than the USA or provide advice for non-US citizens interested in flight training. I cannot answer questions advising you what school to choose. I have no experience with aeronautical engineering so I cannot answer questions relating to engineering or schooling for aeronautical engineers. PLEASE don't ask me questions about any kind of engineering because it is outside my area of expertise, and I will NOT answer your question. I also cannot help you to choose a master's program for study as I do not have a master's degree in aviation. I cannot help with MBA advice.


I have been studying aviation disasters through doing my own research and a lot of reading since I was 13 or 14 years old. I am very interested in aviation safety and also am a commercial, multi-engine pilot. I am Director of Flight Operations at a private university working in the flight training department. I also have worked as an operations manager at a small charter airline and was involved in getting the airline certificated under Part 121 rules. I was formerly a flight operations division manager for a company operating a large fleet of King Air aircraft (60) and so I have some business aviation experience as well as having flight instructed for one year after college. My operations manager job frequently involved coordinating international projects for aerial survey clients and hiring qualified pilots to fly aerial survey missions.

Bachelor of Science, Aeronautical Science with Flight Management Concentration: LeTourneau University (2004) :: Dispatch Certificate: Sheffield School of Aeronautics (2010) :: Commercial Pilot: Single and Multi Engine Land, Instrument Rating :: Flight Instructor: Single, Multi and Instrument :: Ground Instructor: Basic and Advanced

©2016 All rights reserved.