Stock Photo - This close_up view shows the AFTI F_16 air probe early in the research program. It consists of a nose boom resembling a long pipe, and four indicators that look and act like weather vanes. The indicators on the left and right measure pitch, or the movement of the airplane´s nose up or down. Those on the top and bottom of the boom measure yaw, or movement of the nose to the left or right. Similar probes are standard on most research and prototype aircraft. The data from the indicators is recorded aboard the aircraft and/or radioed to the ground. This data includes both the amount of yaw and pitch at any given time, and the rate at which both motions changed in flight. This information, subsequently processed and compared to wind tunnel results, may reveal stability and aerodynamic abnormalities.The two metal half_circles and their attachment fixtures are not part of the air probe. Rather, they are used to calibrate the indicators on the ground, enabling the data to be corrected for instrument errors. The figure in the photograph is shown holding a red Remove Before Flight ribbon, a reminder to the ground crew that it must be taken off prior to a research mission.