P i t o t   R a m   A i r   P r e s s u r e   T o
A i r   S p e e d   C a l c u l a t o r    1 . 5
(for use in calibrating a pitot air speed indicator using a water column manometer)

I n p u t s 
       R e s u l t s
Elevation, feet above sea level
height of manometer water column, inches
Barometric Pressure, inches Hg
Indicated Air Speed, mph
Air Temperature, degrees F
Indicated Air Speed, knots
Dew Point, degrees F
Indicated Air Speed, ft/sec
Enter either Manometer Scale reading, inches
Density Altitude, feet above sea level
and click to compute
True Air Speed (density altitude corrected), mph
OR  Enter Indicated Air Speed, mph
pressure at pitot opening, lbs/sq ft
and click to compute
pressure at pitot opening, lbs/sq in

The Equations:

P = 1.938 sg/ft2 * 32.2 ft/sec2 * (H / 12)

Pressure in pounds per sq ft = (density H2O in slugs per cubic ft * acceleration of gravity in ft per sec per sec) *
(water column height in inches / 12)

V = sqrt((1 / ( 0.0023769 slugs/ft3 * 2116.22 lbs/ft2) * 7 * 2116.22 lbs/ft2 * ((P / 2116.22 lbs/ft3) + 1)0.2857 - 1)

Velocity = sqrt(((1 / sea level air density in slugs per cubic ft) * 7 * sea level air pressure in pounds per sq ft) * ((Pressure / sea level air pressure) + 1) ^ (2/7) -1)

mph = Velocity in feet per sec * 0.68181       kph = Velocity in feet per sec * 0.59249


All ASI gauges are calibrated a standard atmosphere (59 degrees F and 29.92" Hg barometric pressure). Density Altitude compensation to obtain True Air Speed is approximate and nearly insignificant at speeds under 70 mph.

copyright 2005, Dean A. Scott, all rights reserved.
Density Altitude copyright 1998-2004, Richard Shelquist
http://wahiduddin.net/calc/calc_da.htm.

 

Water Column Manometer Setup

Download a 0 - 80 mph Calibrated Manometer Reading Scale to use with the setup below (PDF document)