Figure 1-4. AH-1S Low Airspeed Profile.
a . The AADS is a swiveling pitot-static probe which
error against lateral airspeed for discrete forward speeds,
samples local airflow pitot and static pressures, the angles
a complete picture of Iateral errors is obtained.
of that airflow relative to the helicopter and the free
j. Vertical airspeed errors are corrected in a similar
stream air temperature. Pneumatic pressure outputs are
fed via the helicopter plumbing to transducers in the EPU
way to the horizontal airspeed errors, using error curves
temperature are also fed to the EPU. The pneumatic
pressure outputs are converted into analog electronic
signals by the electrical force balance transducers in the
h e l i c o p t e r is in ground effect, the ADS utilizes the Radar
A l t i t u d e signal to obtain the corrected airspeed at heights
of less than 30 feet.
b. Computation to convert the AADS outputs into
airspeed components and temperature and pressure output
System Description of the Air Data Subsystem
is accomplished by a microprocessor based computing unit
( A D S ) . A system block diagram is shown in figure 1-5 and
i n the EPU. The computing unit also controls input and
modular breakdown of the ADS is shown in figure 1-6.