User manual

Page 38

Aircraft Operation Manual

Piper Cheyenne I, IA, II, IIXL

For ight simulation use only

SAS - Stability Augmentation System

(Cheyenne II only)

1: Stall Margin Indicator

A stability augmentation system (SAS) is incorporated in the ele-

vator control system to improve the static longitudinal stability

of the airplane. Major components of the SAS include an angle-

of-attack sensor vane, a computer, servo actuator, and an eleva-

tor down spring and cable assembly. The angle-of-attack sensor

vane, located on the right side of the nose section, transmits the

airplane´s angle-of-attack to the SAS computer.

Based on the input from the angle-of-attack sensor vane, the

computer sends a signal to the servo actuator, located in the aft

fuselage of the airplane, which is connected to the elevator con-

trol horn through the elevator down spring and cable assembly.

The servo actuator provides variable elevator down spring ten-

sion improving the logitudinal stability to allow more versatile

Also incorporated in the SAS is a stall margin indicator (1), which

receives its signal from the SAS computer. The indicator provi-

des visual input to the pilot of the ratio of present speed to stall

speed for any airplane conguration. The indicator dial is marked

with ve color-coded zones: red (stall), red and black barber pole

(stall warning), yellow (slow), white (30% above stall) and green

(speed greater than 30% above stall).

An additional function of the SAS computer is to provide aural

warning to the pilot, through a stall warning horn, of an impen-

ding stall condition.