{"id":14458,"date":"2025-06-07T16:13:43","date_gmt":"2025-06-07T10:43:43","guid":{"rendered":"https:\/\/ibexaviation.com\/pilot-training\/?p=14458"},"modified":"2025-06-09T19:32:21","modified_gmt":"2025-06-09T14:02:21","slug":"pressure-measurement","status":"publish","type":"post","link":"https:\/\/ibexaviation.com\/pilot-training\/pressure-measurement\/","title":{"rendered":"Pressure Measurement"},"content":{"rendered":"\n<h2>Pressure Measurement<\/h2>\n\n\n\n<h3>Static Pressure<\/h3>\n\n\n\n<ul><li>Static pressure is the Atmospheric pressure or Ambient air pressure<\/li><li>Due to the weight of air column above the aircraft<\/li><li>Reduces with increase in altitude as air column above the aircraft reduce<\/li><\/ul>\n\n\n\n<h3>Dynamic Pressure<\/h3>\n\n\n\n<ul><li>Dynamic pressure is the force exerted when air is brought to rest<\/li><li>By a moving body like aircraft<\/li><\/ul>\n\n\n\n<h3>Pitot Pressure<\/h3>\n\n\n\n<ul><li>An aircraft in flight is affected by both static as well as dynamic pressures<\/li><li>Combined pressure is called Pitot pressure<\/li><li>Pitot pressure is a combination of static and dynamic pressures<\/li><li>Sensed by the pitot tube<\/li><\/ul>\n\n\n\n<h3>Principle of Pitot Static Tube<\/h3>\n\n\n\n<ul><li>Pitot Static tube consists of Pitot and Static heads<\/li><li>Pitot head senses total pressure called pitot pressure<\/li><li>Pitot pressure = Dynamic pressure + Static pressure<\/li><\/ul>\n\n\n\n<h3>Position of Pitot Static Tube<\/h3>\n\n\n\n<ul><li>Pitot Static tube consists of Pitot and Static heads<\/li><li>Located outside boundary layer of the aircraft<\/li><li>Avoids the effect of aircraft on the airflow<\/li><li>On the nose or wing tip or on the side of fuselage<\/li><li>Parallel to Longitudinal axis of the aircraft<\/li><li>Keeps the pitot tube parallel to the airflow in normal flight attitude<\/li><\/ul>\n\n\n\n<h3>Construction of Pitot Static Tube<\/h3>\n\n\n\n<ul><li>Pitot head is the open-ended tube which senses the pitot pressure<\/li><li>It brings moving air to rest in the stagnation wall of pitot tube<\/li><li>Pitot pressure sensed is a combination of Static and Dynamic pressures<\/li><li>Static head are perforations or holes with forward end sealed<\/li><li>Sealing of forward end avoids dynamic pressure<\/li><\/ul>\n\n\n\n<h3>Features of Pitot Static Head<\/h3>\n\n\n\n<ul><li>Heating elements are provided to prevent ice accretion<\/li><li>Drain holes in the pitot static tube removes moisture<\/li><li>Removal of moisture also causes an error due to loss in pressure<\/li><li>Both features cause error in measurement due to change the density<\/li><li>This error is corrected during calibration of pressure instruments<\/li><\/ul>\n\n\n\n<h3>Position or Pressure or Static Error<\/h3>\n\n\n\n<ul><li>Position error is also called Pressure error or Static error<\/li><li>Static tube is designed to sense the correct atmospheric pressure<\/li><li>Position error is caused due to the turbulent airflow near the static holes<\/li><li>Turbulence creates suction effect resulting in detection of lower static<\/li><li>Pressure instruments are provided with lesser than correct static pressure<\/li><\/ul>\n\n\n\n<h3>Variation of Position, Pressure or Static Error<\/h3>\n\n\n\n<ul><li>Turbulent air in the location of Pitot static tube increases static error<\/li><li>Higher speeds increase position error<\/li><li>Increase in speeds increase turbulent air flow<\/li><li>Position error also increases at high angle of attack even at lower speeds<\/li><li>Use of flaps increases angle of attack increasing position error<\/li><\/ul>\n\n\n\n<h3>Static Vents for Position Error Correction<\/h3>\n\n\n\n<ul><li>Position error is corrected by use of independent static vents<\/li><li>Static vents are located in area of least turbulence like sides of fuselage<\/li><li>Designed to drain water without heating unlike that of pitot tube<\/li><li>Two inter-connected static vents located on either side of fuselage<\/li><li>Inter connection removes error due side-slipping or yawing movement<\/li><li>Static vents are unsuitable in high speed aircraft due to shock waves<\/li><li>Fighter aircrafts use high speed pitot-static probe probes<\/li><\/ul>\n\n\n\n<h3>Manoeuvre Induced or Time Lag Error<\/h3>\n\n\n\n<ul><li>Manoeuvre induced errors cause short term fluctuations during manoeuvres<\/li><li>Manoeuvre induces temporary fluctuation of pressure in the static vents<\/li><li>This creates a time lag in readings of pressure instruments<\/li><li>The error is significant during change in configuration of flaps or slats<\/li><li>Noticeable error is also seen during change in angle of attack<\/li><\/ul>\n\n\n\n<h3>Minimum and Maximun Time Lag Error<\/h3>\n\n\n\n<ul><li>Manoeuvre errors are obvious during change in pitch angle<\/li><li>For example, during overshooting, take off, landing or during level out<\/li><li>Time lag error increases with increase in altitude<\/li><li>This error is seen even in Servo assisted altimeters or Air data computers<\/li><li>Time lag could vary from 3 sec at low altitudes to 10 sec at 30,000 ft<\/li><\/ul>\n\n\n\n<h3>Complete Pitot Static System<\/h3>\n\n\n\n<ul><li>Modern aircrafts have independent pitot &amp; static for instruments on left &amp; right<\/li><li>The instruments can be cross connected in case of emergency<\/li><li>Heaters with heating alert warning is provided to avoid ice accretion<\/li><\/ul>\n\n\n\n<h3>Alternate Static Source<\/h3>\n\n\n\n<ul><li>Alternate static source is provided for blockage of main static source<\/li><li>Alternate static may be placed inside the cabin for unpressurised aircrafts<\/li><li>It is at a non optimum location resulting in under reading of static<\/li><li>Alternate static causes over reading of Altimeter and Air speed indicator<\/li><li>Errors due to alternate static usage are tabulated in the flight manual<\/li><\/ul>\n\n\n\n<h2>Share this Page<\/h2>\n","protected":false},"excerpt":{"rendered":"<p>Pressure Measurement Static Pressure Static pressure is the Atmospheric pressure or Ambient air pressure Due to the weight of air column above the aircraft Reduces with increase in altitude as air column above the aircraft reduce Dynamic Pressure Dynamic pressure is the force exerted when air is brought to rest By a moving body like aircraft Pitot Pressure An aircraft in flight is affected by both static as well as dynamic pressures Combined pressure is called Pitot pressure Pitot pressure is a combination of static and dynamic pressures Sensed by&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\/14458"}],"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=14458"}],"version-history":[{"count":0,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14458\/revisions"}],"wp:attachment":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/media?parent=14458"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/categories?post=14458"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/tags?post=14458"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}