Figure 1-4. AH-1S Low Airspeed Profile.

TM 9-1270-219-13&P

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

and

angle

airflow

signals representing

Electronic

and

techniques.

temperature are also fed to the EPU. The pneumatic

pressure outputs are converted into analog electronic

Because

downwash

inconsistent

when

the

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

EPU.

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

1-11.

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.

1-5