Dynamic Pressure

Short Name or Variable Name
QCF, QCR (also QCFR on the C-130)

The dynamic pressure is the excess pressure above ambient that develops when air is compressed and adiabatically brought to rest relative to the moving aircraft. The total pressure, the sum of ambient and dynamic pressure, is normally sensed using a pitot tube, a tube pointed in the direction of the relative airflow and specially designed to be relatively insensitive to small-angle changes in the direction of the relative airflow. The difference between this measurement and the static pressure measurement is the measured dynamic pressure. The dynamic pressure is equal to 0.5 times the air density times the airspeed squared, so dynamic pressure can be used to determine the airspeed of the aircraft. On RAF aircraft, the measurement of dynamic pressure is made by Honeywell digital differential transducers. Because any errors affecting the measurement of static pressure also affect the difference between total and static pressure, the same corrections that are applied to static pressure (for errors in the pressure delivered by the static ports) are also applied to the dynamic pressure, with reversed sign. See the discussion of processing algorithms in the Documentation section.

Model: Honeywell PPT0005GXX2VB-S021

Measurements Provided: Dynamic Pressure

Measurement Characteristics: 

  • GV: Range: 0-5 PSI, Accuracy: 0.001 PSI Typical, ResponseTime: 0.05 s
  • C-130: Range: 0-125 mb; Accuracy: 0.7 mb; Time Response: 0.02 s
  • Overall estimate of uncertainty: 0.001 PSI
  • Response time: 50 ms / 20 ms
Calibration Methods

RAF Calibration Cart / Traceable Pressure Standard - GV is digital so not susceptible to DSM A2D temperature variations.

Lead Contact
Adriana Bailey