{"id":14466,"date":"2025-06-07T16:15:37","date_gmt":"2025-06-07T10:45:37","guid":{"rendered":"https:\/\/ibexaviation.com\/pilot-training\/?p=14466"},"modified":"2026-07-26T10:26:20","modified_gmt":"2026-07-26T04:56:20","slug":"errors-in-altimeter","status":"publish","type":"post","link":"https:\/\/ibexaviation.com\/pilot-training\/errors-in-altimeter\/","title":{"rendered":"Errors in Altimeter"},"content":{"rendered":"<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-1.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<h2>Errors and Remedial Actions for Pressure Altimeter<\/h2>\n<p>The main altimeter errors are instrument error, position error, and pressure\/temperature error, which can cause incorrect altitude readings. These errors occur due to instrument imperfections, airflow effects, and changes in atmospheric conditions.<\/p>\n<h3>Position and Instrument Errors in Altimeter<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-2.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Position or Pressure error is caused due to location of pitot head.<\/li>\n<li>Instrument error is caused due to mechanical imperfections.<\/li>\n<li>Position and instrument errors are corrected on the ground.<\/li>\n<li>Residual errors are listed on a correction card.<\/li>\n<\/ul>\n<h3>Manoeuvre and Time Lag Errors in Altimeter<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-3.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Manoeuvre-induced error causes temporary fluctuations in attitude indications.<\/li>\n<li>Time lag error is caused due to the sluggish response of the capsule to pressure changes.<\/li>\n<li>Servo-assisted altimeter avoids time lag error.<\/li>\n<\/ul>\n<h3>Barometric Error<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-4.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Barometric error is caused due to changes in Mean Sea Level (MSL) pressure.<\/li>\n<\/ul>\n<h2>Effect of Variation of Pressure and Temperature on Altimeter<\/h2>\n<h3>Effect of Incorrect QNH Setting<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-5.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>If an incorrect QNH is set in the sub-scale, the indicated altitude will differ from the actual altitude.<\/li>\n<li>If the sea level pressure decreases, the set datum becomes lower than MSL.<\/li>\n<li>The altimeter will <strong>over-read<\/strong>.<\/li>\n<li>If the sea level pressure increases, the set datum becomes higher than MSL.<\/li>\n<li>The altimeter will <strong>under-read<\/strong>.<\/li>\n<\/ul>\n<h3>Flight from High to Low Pressure Area<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-6.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>During a flight from a high-pressure area to a low-pressure area, the indicated altitude will be higher than the true altitude.<\/li>\n<li>True altitude is lower than that indicated by the altimeter.<\/li>\n<li>The altimeter over-reads, reducing terrain clearance, which is potentially dangerous.<\/li>\n<\/ul>\n<h3>Flight from Low to High Pressure Area<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-7.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>During a flight from a low-pressure area to a high-pressure area, the indicated altitude will be lower than the true altitude.<\/li>\n<li>True altitude is higher than that indicated by the altimeter.<\/li>\n<li>The altimeter under-reads, increasing terrain clearance.<\/li>\n<li>This is generally less dangerous from a terrain clearance point of view.<\/li>\n<\/ul>\n<h3>Temperature Error \u2013 Cold Air<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-8.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Consider a flight between two places with the same Mean Sea Level pressure.<\/li>\n<li>Colder air has a higher lapse rate.<\/li>\n<li>At a particular altitude, the observed pressure is lower.<\/li>\n<li>The indicated altitude will be higher than the true altitude.<\/li>\n<li>The altimeter over-reads during a flight from a warmer region to a colder region.<\/li>\n<\/ul>\n<h3>Temperature Error \u2013 Warm Air<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-9.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Consider a flight between two places with the same Mean Sea Level pressure.<\/li>\n<li>Warmer air has a lower lapse rate.<\/li>\n<li>At a particular altitude, the observed pressure is higher.<\/li>\n<li>The indicated altitude will be lower than the true altitude.<\/li>\n<li>The altimeter under-reads during a flight from a colder region to a warmer region.<\/li>\n<\/ul>\n<h3>Regional QNH<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-10.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Regional QNH is the lowest forecast QNH within an Altimeter Setting Region.<\/li>\n<li>Issued every hour for use while flying close to the ground.<\/li>\n<li>Ensures minimum terrain clearance.<\/li>\n<\/ul>\n<h3>Temperature Variation from ISA Temperature<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-11.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Effect of temperature variation from ISA:<\/li>\n<li>For every <strong>1\u00b0C colder<\/strong> than ISA, the altimeter over-reads by <strong>4 ft per 1,000 ft<\/strong>.<\/li>\n<li>For every <strong>1\u00b0C warmer<\/strong> than ISA, the altimeter under-reads by <strong>4 ft per 1,000 ft<\/strong>.<\/li>\n<\/ul>\n<h3>Effect of Pressure and Temperature<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-12.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>For both pressure and temperature:<\/li>\n<li><strong>High to Low \u2192 Altimeter Over-reads<\/strong><\/li>\n<li><strong>Low to High \u2192 Altimeter Under-reads<\/strong><\/li>\n<\/ul>\n<h3>Alticor<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-13.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Alticor = Indicated Altitude \u2212 True Altitude.<\/li>\n<li>Add <strong>30 ft<\/strong> for every <strong>1 hPa<\/strong> higher than Mean Sea Level pressure.<\/li>\n<li>Add <strong>1%<\/strong> of the indicated altitude for <strong>ISA +3\u00b0C<\/strong> conditions.<\/li>\n<li>D-value = True Altitude \u2212 Indicated Altitude.<\/li>\n<\/ul>\n<h2>Effect of Blockage and Leaks on Altimeters<\/h2>\n<h3>Blockage of Static Vent<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-14.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>A blocked static vent causes the altimeter to indicate the altitude at which the blockage occurred.<\/li>\n<li>It will <strong>under-read during climb<\/strong>.<\/li>\n<li>It will <strong>over-read during descent<\/strong>.<\/li>\n<\/ul>\n<h3>Leak in Static Vent<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-15.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Leakage in the static line outside the pressurised compartment causes no significant problem; the altimeter indicates correctly.<\/li>\n<li>A leak in the static line inside the pressurised compartment causes the altimeter to indicate cabin altitude instead of actual altitude.<\/li>\n<\/ul>\n<h3>Error Summary<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i7-altimeter-errors-16.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<p><strong>Remember:<\/strong><\/p>\n<ul>\n<li><strong>High to Low Pressure \u2192 Altimeter Over-reads<\/strong><\/li>\n<li><strong>Low to High Pressure \u2192 Altimeter Under-reads<\/strong><\/li>\n<li><strong>Warm to Cold \u2192 Altimeter Over-reads<\/strong><\/li>\n<li><strong>Cold to Warm \u2192 Altimeter Under-reads<\/strong><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Errors and Remedial Actions for Pressure Altimeter The main altimeter errors are instrument error, position error, and pressure\/temperature error, which can cause incorrect altitude readings. These errors occur due to instrument imperfections, airflow effects, and changes in atmospheric conditions. Position and Instrument Errors in Altimeter Position or Pressure error is caused due to location of pitot head. Instrument error is caused due to mechanical imperfections. Position and instrument errors are corrected on the ground. Residual errors are listed on a correction card. Manoeuvre and Time Lag Errors in Altimeter Manoeuvre-induced&hellip;<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"disable_featured_image":false,"footnotes":""},"categories":[345],"tags":[],"class_list":["post-14466","post","type-post","status-publish","format-standard","hentry","category-cpl-atpl-flight-instruments"],"_links":{"self":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/comments?post=14466"}],"version-history":[{"count":1,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14466\/revisions"}],"predecessor-version":[{"id":16652,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14466\/revisions\/16652"}],"wp:attachment":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/media?parent=14466"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/categories?post=14466"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/tags?post=14466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}