{"id":14504,"date":"2025-06-07T16:24:43","date_gmt":"2025-06-07T10:54:43","guid":{"rendered":"https:\/\/ibexaviation.com\/pilot-training\/?p=14504"},"modified":"2026-07-26T10:36:53","modified_gmt":"2026-07-26T05:06:53","slug":"ground-proximity-warning-system","status":"publish","type":"post","link":"https:\/\/ibexaviation.com\/pilot-training\/ground-proximity-warning-system\/","title":{"rendered":"Ground Proximity Warning System (GPWS)"},"content":{"rendered":"<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-1.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<h2>Warning of Controlled Flight into Terrain by Ground Proximity Warning System (GPWS)<\/h2>\n<h3>Introduction to GPWS<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-2.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>The Ground Proximity Warning System (GPWS) helps prevent Controlled Flight Into Terrain (CFIT).<\/li>\n<li>It warns the flight crew when the aircraft is in unsafe proximity to terrain.<\/li>\n<li>The system typically operates between <strong>50 ft and 2450 ft<\/strong> radio altitude, similar to the radio altimeter range.<\/li>\n<li>GPWS automatically selects operating modes based on flight conditions.<\/li>\n<li>It uses inputs from the radio altimeter, Mach meter, Air Data Computer (ADC), and glide slope receiver.<\/li>\n<li>Additional inputs include landing gear, flap position, and navigation systems.<\/li>\n<\/ul>\n<h3>Stages of GPWS Warnings<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-3.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>GPWS warnings are categorised into two levels:<\/li>\n<ul>\n<li><strong>Alerts<\/strong> \u2013 Cautionary warnings requiring pilot awareness and preparation.<\/li>\n<li><strong>Warnings<\/strong> \u2013 Mandatory commands requiring immediate pilot action.<\/li>\n<\/ul>\n<\/ul>\n<h2>Operating Modes of GPWS<\/h2>\n<h3>Mode 1 \u2013 Excessive Descent Rate (Sink Rate)<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-4.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Mode 1 operates independently of aircraft configuration.<\/li>\n<li>Active below approximately <strong>2500 ft radio altitude<\/strong>.<\/li>\n<li>First threshold triggers the alert: <strong>&#8220;SINK RATE&#8221;<\/strong> (repeated every 1.5 seconds).<\/li>\n<li>Second threshold triggers urgent warning: <strong>&#8220;WHOOP WHOOP PULL UP&#8221;<\/strong>.<\/li>\n<li>A red <strong>PULL UP<\/strong> visual warning is also displayed.<\/li>\n<\/ul>\n<h3>Mode 2 \u2013 Excessive Terrain Closure Rate<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-5.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Mode 2 monitors aircraft closure rate to terrain using multiple parameters:<\/li>\n<ul>\n<li>Mach number<\/li>\n<li>Radio altitude<\/li>\n<li>Rate of descent<\/li>\n<li>Barometric altitude<\/li>\n<li>Aircraft configuration<\/li>\n<\/ul>\n<li>Typically active below <strong>1500 ft<\/strong> at Mach 0.35.<\/li>\n<li>At higher speeds or gear-up configuration, activation height increases up to 2450 ft.<\/li>\n<li>First alert: <strong>&#8220;TERRAIN, TERRAIN&#8221;<\/strong> (repeated every 1.5 seconds).<\/li>\n<li>Second warning: <strong>&#8220;WHOOP WHOOP PULL UP&#8221;<\/strong>.<\/li>\n<li>In landing configuration, only the &#8220;TERRAIN&#8221; alert may sound.<\/li>\n<\/ul>\n<h3>Mode 3 \u2013 Descent After Take-off or Go-Around<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-6.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Active during initial climb or go-around phases.<\/li>\n<li>Triggers when the aircraft loses more than ~10% of barometric altitude gain.<\/li>\n<li>Operates between <strong>50 ft and 700 ft radio altitude<\/strong>.<\/li>\n<li>Audio alert: <strong>&#8220;DON&#8217;T SINK&#8221;<\/strong> repeated every 1.5 seconds.<\/li>\n<\/ul>\n<h3>Mode 4A \u2013 Unsafe Terrain Clearance (Gear Not Down)<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-7.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Active below approximately <strong>500 ft radio altitude<\/strong>.<\/li>\n<li>Warns when landing gear is not extended during descent.<\/li>\n<li>Upper limit increases up to 1000 ft under certain conditions.<\/li>\n<li>Below Mach 0.35: <strong>&#8220;TOO LOW GEAR&#8221;<\/strong>.<\/li>\n<li>Above Mach 0.35: <strong>&#8220;TOO LOW TERRAIN&#8221;<\/strong>.<\/li>\n<\/ul>\n<h3>Mode 4B \u2013 Unsafe Terrain Clearance (Flaps Not in Landing Configuration)<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-8.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Active when gear is down but flaps are not properly configured below ~300 ft.<\/li>\n<li>Below Mach 0.28: <strong>&#8220;TOO LOW FLAPS&#8221;<\/strong>.<\/li>\n<li>Above Mach 0.28: <strong>&#8220;TOO LOW TERRAIN&#8221;<\/strong>.<\/li>\n<li>Gear warning has higher priority than flap warning.<\/li>\n<li>This mode can be inhibited using the flap override switch.<\/li>\n<\/ul>\n<h3>Mode 5 \u2013 Glide slope Deviation Alert<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-9.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Activates when aircraft deviates significantly below Glide slope (about 1.3 dots).<\/li>\n<li>Operates below 1000 ft during ILS approach.<\/li>\n<li>Requires active Glide slope receiver and landing configuration.<\/li>\n<li>Audio warning: <strong>&#8220;GLIDESLOPE&#8221;<\/strong> (hard or soft depending on deviation).<\/li>\n<li>Can be cancelled using the BELOW G\/S switch.<\/li>\n<\/ul>\n<h3>Mode 6A \u2013 Minimums Alert<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-10.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Warns when aircraft descends below selected minimum decision altitude.<\/li>\n<li>Active between 50 ft and 1000 ft radio altitude.<\/li>\n<li>Audio call-out: <strong>&#8220;MINIMUMS, MINIMUMS&#8221;<\/strong> (single alert).<\/li>\n<li>Re-armed when aircraft climbs above selected minimum altitude.<\/li>\n<\/ul>\n<h3>Mode 6B \u2013 Altitude Callouts and Bank Angle Alert<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-11.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Provides automatic altitude callouts at predefined heights (e.g., 200 ft, 100 ft).<\/li>\n<li>Also provides <strong>\u201cBANK ANGLE\u201d<\/strong> warnings during excessive roll.<\/li>\n<li>Bank angle limits reduce as aircraft gets closer to the ground.<\/li>\n<\/ul>\n<h3>Mode 7 \u2013 Wind Shear Alert<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-12.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Provides visual and aural warnings for wind shear conditions.<\/li>\n<li>Has highest priority over all other GPWS modes.<\/li>\n<li>Enables immediate go-around decision by pilot.<\/li>\n<li>Uses multiple inputs:<\/li>\n<ul>\n<li>Ground speed<\/li>\n<li>Airspeed<\/li>\n<li>Barometric altitude<\/li>\n<li>Rate of descent<\/li>\n<li>Radio altitude<\/li>\n<\/ul>\n<\/ul>\n<h2>Advancements in GPWS like EGPWS and RAWS<\/h2>\n<h3>Enhanced Ground Proximity Warning System (EGPWS)<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-14.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>EGPWS incorporates a terrain awareness database (TAWS).<\/li>\n<li>Provides predictive terrain warnings ahead of the aircraft.<\/li>\n<li>Displays terrain in colour-coded format:<\/li>\n<ul>\n<li>Green \u2013 safe terrain<\/li>\n<li>Yellow \u2013 caution<\/li>\n<li>Red \u2013 immediate danger<\/li>\n<\/ul>\n<li>Can be integrated with weather radar or navigation displays.<\/li>\n<li>Typical alerts include &#8220;TERRAIN AHEAD&#8221; and &#8220;PULL UP&#8221;.<\/li>\n<\/ul>\n<h3>Action on GPWS Warning<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-15.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>Pilots must respond immediately and positively to GPWS warnings.<\/li>\n<li>Standard response: wings level and maximum climb rate.<\/li>\n<li>Climb to a safe altitude as quickly as possible.<\/li>\n<li>Verify aircraft position and identify cause of warning.<\/li>\n<\/ul>\n<h3>Pilot Override Conditions<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-16.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>GPWS warnings should only be disregarded if:<\/li>\n<ul>\n<li>Cause of warning is positively identified.<\/li>\n<li>Warning has ceased.<\/li>\n<li>Daytime conditions with clear visibility exist.<\/li>\n<li>No immediate terrain, configuration, or manoeuvrer hazard is present.<\/li>\n<\/ul>\n<\/ul>\n<h3>Runway Awareness and Advisory System (RAAS)<\/h3>\n<p> <img decoding=\"async\" src=\"https:\/\/ibexaviation.com\/page-show\/flight-instruments\/i26-ground-proximity-warning-system-17.jpg\" alt=\"\" loading=\"lazy\"\/><\/p>\n<ul>\n<li>RAAS improves situational awareness during taxi, take-off, approach, and landing.<\/li>\n<li>Reduces risk of runway incursions.<\/li>\n<li>Uses a Terrain Clearance Floor database around airports.<\/li>\n<li>Helps prevent premature descent during non-precision approaches.<\/li>\n<\/ul>\n<h2>Pilot Actions on GPWS Warning<\/h2>\n","protected":false},"excerpt":{"rendered":"<p>Warning of Controlled Flight into Terrain by Ground Proximity Warning System (GPWS) Introduction to GPWS The Ground Proximity Warning System (GPWS) helps prevent Controlled Flight Into Terrain (CFIT). It warns the flight crew when the aircraft is in unsafe proximity to terrain. The system typically operates between 50 ft and 2450 ft radio altitude, similar to the radio altimeter range. GPWS automatically selects operating modes based on flight conditions. It uses inputs from the radio altimeter, Mach meter, Air Data Computer (ADC), and glide slope receiver. Additional inputs include landing&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-14504","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\/14504","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=14504"}],"version-history":[{"count":1,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14504\/revisions"}],"predecessor-version":[{"id":16671,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14504\/revisions\/16671"}],"wp:attachment":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/media?parent=14504"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/categories?post=14504"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/tags?post=14504"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}