Pressure: Effects on Aircraft Altimeter Performance

    The environmental hazard that I have chosen for this blog entry is the pressure changes and its effects on altitude readings. We measure this through the use of an altimeter, according to J.C Bellamy. If the factors influencing pressure remained constant, then pilots would be able to maintain a constant height with ease. However; this is rarely the case. These variables need to be accounted for on the altimeter so that it displays the true altitude. An example: if an aircraft is flown from a high pressure area to a low pressure area the constant altitude would be displayed, but the actual height of the aircraft above the ground would be lower than the indicated altitude. The other major factor that influences this is temperature. For example, when the pilot flies into a colder air mass while keeping a constant altitude, the true altitude would be lower due to the molecules moving more slowly, crowding together, and causing the air to increase in density (Ahrens, pg. 198). This would cause the reading to remain the indicated altitude, but in reality it would be lower than indicated. This would pose a significant hazard to a plane flying in an mountainous area with low visibility for example.

Photo Credit: Flightline Weekly


    As illustrated above, it's safe to say that pressure is a an environmental factor that requires careful consideration when planning flights. The changes in temperature or pressure that produce false readings on the aircraft altimeter  can be compensated for by the pilots flying the aircraft using calculated altitude adjustments. According to the FAA, this is done using formulas derived from ICAO or the International Civil Aviation Organization as portrayed in Mitrowsky's tutorial video (Mitrowsky, 2013). As with most hazards out there, mitigation measures have been established to combat them. An experienced, driven pilot would try and set the reading of their altimeter to the current one for the airfield as communicated by air traffic control. The aircraft instrument systems should be and are inspected and tested for accurate readings based on manufacturer specifications. (Airport Programs & Guidance, 2021). All of these steps are taken into account by the pilots in the interest of avoiding potential mishaps, or in the worst cases, even a crash.



References:


Ahrens, C. D., & Henson, R. (2019). Meteorology today: an introduction to weather, climate and the environment (12th ed.). Cengage.


Bellamy, J. C. (1945). THE USE OF PRESSURE ALTITUDE AND ALTIMETER CORRECTIONS IN METEOROLOGY, Journal of Atmospheric Sciences, 2(1), 1-79. Retrieved Jul 17, 2021, from https://journals.ametsoc.org/view/journals/atsc/2/1/1520-0469_1945_002_0001_tuopaa_2_0_co_2.xml


Calitz, G. (2020, November 10). Density Altitude -The Silent Killer. flightlineweekly. https://www.flightlineweekly.com/post/density-altitude-the-silent-killer.


Mitrowsky. (2013, February 27). Altimetry basic principles. YouTube. https://www.youtube.com/watch?v=-Dvsh-udkJQ.

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