- Impact pressure
Impact pressure is the difference between pitot pressure (also known as
stagnation pressure ) andstatic pressure . [ [http://www.answers.com/topic/impact-pressure DoD and NATO definition of impact pressure] Retrieved on 2008-10-01] [ [http://www.thefreedictionary.com/impact+pressure The Free Dictionary] Retrieved on 2008-10-01] Inaerodynamics notation, this quantity is denoted as q_c or Q_c.Significance
Impact pressure measurements are used to measure
airspeed onaircraft . The resulting quantity,indicated airspeed , can be found as the positive square root of the following application ofBernoulli's equation for compressible fluids::IAS = sqrt{frac{2q_c}{ ho
where (using SI units):
:IAS = indicated airspeed in m/s:q_c = impact pressure in pascals :ho = standard air density in kg/m3
More information
Measurements of impact pressure are typically imperfect due to the variation of static pressure readings in different locations of the aircraft. This is why aircraft-specific correction tables are used to eliminate this error, producing
calibrated airspeed .Note that for an incompressible fluid, impact pressure is equal to
dynamic pressure . For compressible fluids (such asair ), the resultant airspeed can be further corrected for compressibility effects and variation of air density with altitude. These corrections yieldequivalent airspeed andtrue airspeed , respectively.References
See also
*
Airspeed
*Dynamic pressure
*Pitot-static system
*Pressure
*Static pressure
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