Originally Posted by MPGiles
Two questions How is speed calculted on the stealth aircraft which I presume don't have poles sticking into the breeze
Michigan Aerospace:
"Pitot Probe/Static Ports/Alpha Sensors are used on the F-16, F-18, and the F-117. Flush Port Sensors are used on the X-15, Space Shuttle (SEADS Experiment), B-2, and the A-12. A hybrid system (Pitot Probe/Alpha Sensor/Flush Port) is used on the F-22. The B-2 has quad flush port sensors for the quad flight control systems. Flush Port Pressure Sensors are symmetrically placed on the airframe. The pressure measured at each port varies as the airframe maneuvers. Pressure differences between symmetrical ports correspond to changes in angle of attack and sideslip. Pressure data is derived from wind tunnel and flight tests. The B-2 air data system is made up of two gust load alleviation static ports, differential beta static ports, and left and right alpha/static ports. Each port contains its own 1553 terminal, which is tied to the Flight Control Computer (FCC) along with the total temperature (probe measured at engine inlet) and nose gear position. The air data computation routines in the FCC then determine angle of attack, angle of sideslip, static pressure, pressure altitude, mach number, dynamic pressure, and true air speed."
One of the advantages of laser based/optical air data systems, as well as the so called 'smart probes' is that they are very accurate (even down to very low speeds) and don't suffer from the pneumatic lag inherent in contemporary systems. This enables the FCS to have access to the most accurate current data, and aids flight stability.
Because OADS are capable of detecting air molecules in advance of the airframe, this gives the FCS the ability to act partially as a predictor 'crystal ball' system and issue corrective control surface commands before the airframe has encountered a particular body of air. I think this can be viewed as a flight safety as well as a flight comfort benefit.
Turbulence detection and wind profiling
Obi