{"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":"2025-06-10T12:49:59","modified_gmt":"2025-06-10T07:19:59","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":"\n<h2>Ground Proximity Warning System<\/h2>\n\n\n\n<h3>Introduction to GPWS<\/h3>\n\n\n\n<ul><li>Ground proximity warning system prevents controlled flight into terrain<\/li><li>Warns of proximity to the terrain which are potential threats to safety<\/li><li>Operates in height band 50 to 2450 feet, which is same as radio altimeter<\/li><li>Automatic selection of operation mode based on flight profile<\/li><li>Radio altimeter, Mach meter, ADC and Glidepath provide inputs<\/li><li>Undercarriage, Flaps and Navigation systems also provide inputs<\/li><\/ul>\n\n\n\n<h3>Stages of GPWS Warnings<\/h3>\n\n\n\n<ul><li>GPWS warnings fall under two categories<ul><li>Alert is a caution which means advisory instructions.<\/li><li>Warnings are commands which means obey the instructions.<\/li><\/ul><\/li><\/ul>\n\n\n\n<h3>Mode 1 &#8211; Excessive Barometric Descent Rate<\/h3>\n\n\n\n<ul><li>Mode 1 has two boundaries and is independent of aircraft configuration<\/li><li>This mode activates below 2500 feet on radio altimeter.<\/li><li>Penetration of the first boundary generates an voice alert of \u00e2\u20ac\u0153SINK RATE\u00e2\u20ac\u009d<\/li><li>Audio warning repeats every 1.5 seconds.<\/li><li>Penetrating the second boundary causes the repeated warnings<\/li><li>Audio of \u00e2\u20ac\u0153WHOOP, WHOOP PULL UP\u00e2\u20ac\u009d<\/li><li>Visual light indication of \u00e2\u20ac\u02dcPULL UP\u00e2\u20ac\u2122<\/li><\/ul>\n\n\n\n<h3>Mode 2 &#8211; Excessive Terrain Closure Rate<\/h3>\n\n\n\n<ul><li>Mode 2 monitors five parameters to set its boundaries<\/li><li>Mach, radio altitude, rate of change, barometric altitude and configuration<\/li><li>Mode 2 operates below 1500 feet at 0.35 mach<\/li><li>Increase in mach number to 0.45 with gear up increases height to 2450 feet<\/li><li>Flap override switch overrides the higher portion of envelope<\/li><li>First boundary triggers an audio alert of \u00e2\u20ac\u0153Terrain, Terrain\u00e2\u20ac\u009d every 1.5 seconds.<\/li><li>Second boundary generates audio warning of \u00e2\u20ac\u0153WHOOP, WHOOP PULL UP\u00e2\u20ac\u009d<\/li><li>In landing configuration, only the repeating TERRAIN voice alert is heard.<\/li><\/ul>\n\n\n\n<h3>Mode 3 &#8211; Descent after Take-off or Go-around<\/h3>\n\n\n\n<ul><li>Mode 3 alerts for descent is made during initial climb or go-around<\/li><li>The audio alert of \u00e2\u20ac\u0153DON\u00e2\u20ac\u2122T SINK\u00e2\u20ac\u009d is repeated each 1.5 seconds<\/li><li>Operating height is between 50 and 700 feet of radio altitude.<\/li><li>Alerts when aircraft descends more than 10 percent of barometric altitude.<\/li><li>Mode 3 does trigger below 200 feet of radio altitude.<\/li><\/ul>\n\n\n\n<h3>Mode 4A &#8211; Unsafe Terrain Clearance &#8211; Landing Gear Not down<\/h3>\n\n\n\n<ul><li>Mode 4A operates if aircraft descends below set height without landing gear.<\/li><li>This mode operates below 500 feet of radio altitude<\/li><li>Landing gear mode armed after aircraft climbs above 700 feet radio altitude.<\/li><li>Upper limit increases from 500 feet to 1000 feet radio altitude.<\/li><li>Below Mach 0.35, the aural alert \u00e2\u20ac\u0153TOO LOW GEAR\u00e2\u20ac\u009d is heard every 1.5 seconds<\/li><li>Above Mach 0.35, voice alert \u00e2\u20ac\u0153TOO LOW TERRAIN\u00e2\u20ac\u009d is heard every 1.5 seconds<\/li><\/ul>\n\n\n\n<h3>Mode 4B &#8211; Unsafe Terrain Clearance &#8211; Flaps Not in Landing Configuration<\/h3>\n\n\n\n<ul><li>Mode 4B alerts if landing gear is down without flaps below 300 feet.<\/li><li>Below Mach 0.28, voice alert of \u00e2\u20ac\u0153TOO LOW FLAPS\u00e2\u20ac\u009d is heard every 1.5 seconds<\/li><li>Above Mach 0.28, audio of \u00e2\u20ac\u0153TOO LOW TERRAIN\u00e2\u20ac\u009d is heard every 1.5 seconds<\/li><li>Upper boundary increases to 1000 feet radio altitude.<\/li><li>\u00e2\u20ac\u0153TOO LOW GEAR\u00e2\u20ac\u009d alert takes priority over the \u00e2\u20ac\u0153TOO LOW FLAPS\u00e2\u20ac\u009d.<\/li><li>Mode 4B is inhibited by \u00e2\u20ac\u02dcFLAP OVRD\u00e2\u20ac\u2122 switch<\/li><\/ul>\n\n\n\n<h3>Mode 5 &#8211; Below Glide Slope Deviation Alert<\/h3>\n\n\n\n<ul><li>Mode 5 alerts descent of 1.3 dots below glide slope, below 1000 feet on ILS<\/li><li>Operates when glide slope receiver is active and landing gear is down<\/li><li>Hard alert sounds at full volume whereas Soft alert is at reduced volume<\/li><li>Repetition rate increases with glide slope deviation and reducing in altitude<\/li><li>Mode 5 is cancelled by pressing \u00e2\u20ac\u02dcBELOW G\/S\u00e2\u20ac\u2122 light<\/li><li>Above 1000 feet radio altitude mode 5 will get re armed.<\/li><li>Mode 1 to 4 audio alerts have priority over mode 5<\/li><li>PULL UP and BELOW G\/S lights could light up simultaneously<\/li><\/ul>\n\n\n\n<h3>Mode 6A \u00e2\u20ac\u201c Descent Below Selected Minimum Radio Altitude<\/h3>\n\n\n\n<ul><li>Mode 6A alerts on descent below the minimum decision altitude<\/li><li>MDA is set using a cursor on captain\u00e2\u20ac\u2122s radio altimeter.<\/li><li>Mode 6A is active between 50 and 1000 feet of radio altitude.<\/li><li>Audio alert consists of \u00e2\u20ac\u0153MINIMUMS, MINIMUMS\u00e2\u20ac\u009d sounded only once.<\/li><li>The mode is re-armed when the radio altitude increases above the MDA.<\/li><\/ul>\n\n\n\n<h3>Mode 6B &#8211; Altitude Call-outs and Bank Angle Alert<\/h3>\n\n\n\n<ul><li>Mode 6B calls out at altitudes at pre selected intervals and at minimums<\/li><li>Normally, calls out at 200 ft and 100 ft to decision height<\/li><li>Alternately absolute height call-outs from the radio altimeter.<\/li><li>Mode 6B also calls out \u00e2\u20ac\u0153BANK ANGLE\u00e2\u20ac\u009d to alert for excessive roll angles.<\/li><li>Bank angle limits reduce with proximity to the ground<\/li><\/ul>\n\n\n\n<h3>Mode 7 &#8211; Wind Shear Alert<\/h3>\n\n\n\n<ul><li>Mode 7 provides visual and audio wind shear warnings based on calculations<\/li><li>Pilot can initiate quicker wind shear go-around actions.<\/li><li>Mode 7 warnings take priority over all other modes.<\/li><li>GPWS calculates the initial conditions for entering an area of wind shear.<\/li><\/ul>\n\n\n\n<h3>Mode 7 &#8211; Wind Shear Alert Calculation<\/h3>\n\n\n\n<ul><li>The calculations are based on five inputs<ul><li>Ground speed<\/li><li>Air speed<\/li><li>Barometric height<\/li><li>Rate of descent<\/li><li>Radio altitude<\/li><\/ul><\/li><\/ul>\n\n\n\n<h3>Enhanced Ground Proximity Warning System<\/h3>\n\n\n\n<ul><li>EGPWS provides warnings from rising terrain ahead using TAWS<\/li><li>Terrain Awareness and Warning System is a world-wide terrain data base<\/li><li>Terrain ahead is shown in shades of green, yellow and red on a display<\/li><li>Display could be independent or of weather radar or navigation screen<\/li><li>Audio warning may be of Caution Terrain Ahead or Whoop Whoop Pull Up<\/li><li>Voice message in this mode depends on the type of danger<\/li><\/ul>\n\n\n\n<h3>Action on GPWS Warning<\/h3>\n\n\n\n<ul><li>Pilots must take positive and immediate response to GPWS warnings<\/li><li>Wings level and initiate a maximum gradient climb until minimum safe altitude<\/li><li>Find the cause of the warning and verify the aircraft\u00e2\u20ac\u2122s position.<\/li><\/ul>\n\n\n\n<h3>Pilot Override on GPWS Warning<\/h3>\n\n\n\n<ul><li>Action can be deferred only under the following circumstances<ul><li>Positively identification of cause<\/li><li>Warning has ceased<\/li><li>During day<\/li><li>Clear visual conditions<\/li><\/ul><\/li><li>Obviously not in any dangerous situation with regard to three factors<\/li><li>Terrain clearance, Aircraft configuration or the Manoeuvre<\/li><\/ul>\n\n\n\n<h3>Runway Awareness and Advisory System<\/h3>\n\n\n\n<ul><li>Runway Awareness and Advisory System increases situational awareness<\/li><li>Reduce the likely-hood of runway incursions.<\/li><li>Provides advisory during taxi, take off approach and landing<\/li><li>RAAS uses Terrain Clearance Floor for its operation<\/li><li>Terrain clearance floor is a height map in the vicinity of airfields<\/li><li>Avoids premature descent on non-precision approaches<\/li><\/ul>\n\n\n\n<h2>Share this Page<\/h2>\n","protected":false},"excerpt":{"rendered":"<p>Ground Proximity Warning System Introduction to GPWS Ground proximity warning system prevents controlled flight into terrain Warns of proximity to the terrain which are potential threats to safety Operates in height band 50 to 2450 feet, which is same as radio altimeter Automatic selection of operation mode based on flight profile Radio altimeter, Mach meter, ADC and Glidepath provide inputs Undercarriage, Flaps and Navigation systems also provide inputs Stages of GPWS Warnings GPWS warnings fall under two categories Alert is a caution which means advisory instructions. Warnings are commands which&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},"categories":[345],"tags":[],"_links":{"self":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14504"}],"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":0,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14504\/revisions"}],"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}]}}