[Scan-DC] Windshear Systems

[bobjeter1]

Most airports, including DCA, have a windshear system installed but  
they only function in limited weather events i.e. fast moving (usually  
cold) fronts or a thunderstorm near one of the sensors. One, of  
several, is in Alexandria, another is on the airport itself. If the  
winds at the sensors and airport are approximately the same, the  
system does not sound an alert.

Pilots are on the alert for a sudden change in airspeed during descent  
or climb out which is caused by a rapid change in wind velocity and/or  
direction in a short altitude span. The area of shear usually moves  
around geographically and may be short lived at any altitude and/or  
location. Weather characteristics causing shear is widely known by  
aircrews and ATC folks. Some airlines prohibit an approach at all if  
windshear alerts are generated by the tower for a particular runway.

Some airplanes have onboard equipment to detect shear and alert the  
pilots, other wise the pilot not flying constantly monitors airspeed.  
The  escape manuever is routinely practiced in the simulator.

AT DCA a sudden pull up/go around could make you a candidate for a  
military intercept/adverse action due to proximity of White House and  
a pre-determined threat profile by TSA.

73, Bob K#RSJ (retired pilot)