1. AUTOMATIC FLIGHT CONTROL SYSTEM (AFCS)
Presented by
CW3 Martin Dadswell

2. PURPOSE: To develop the Student
Instructor Pilot’s understanding of the
Automatic Flight Control System
NEED: You will be instructing this
subject in the near future

3. TOPICS OF DISCUSSION Auto Flight Control System What is Stability?
Stability Augmentation System
TRIM
Flight Path Stabilization
Malfunction Analysis

4. WHAT IS AFCS?
AFCS enhances the stability and handling qualities of the UH60 helicopter. It is comprised of four subsystems:
Stability Augmentation System (SAS)
Trim Systems
Flight Path Stabilization (FPS)
Stabilator (previously discussed)

5. WHAT IS STABILITY? Create a cool drawing on the dry erase
board at this time.

6. Stability, in physics and engineering, the property of a body that causes it to return to its original position or motion as a result of the action of the so- called restoring forces, or torques, once the body has been disturbed from a condition of equilibrium or steady motion.

7. STABILITY AUGMENTATION SYSTEM (SAS)
Purpose: Provide dynamic stability through short term rate dampening in the pitch, roll, and yaw axis.
SAS systems: SAS 1 & SAS 2
Control Authority: Each SAS has 5% control authority, for a total of 10%

8. SAS 1 Components: Input Signals:
SAS1 amplifier (analog) is located in the avionics compartment
Three SAS actuators
Input Signals:
Pitch - rate gyro in the #1 stabilator amplifier
Roll - pilot’s (number 2) vertical gyro
Yaw - yaw rate gyro in the SAS1 amplifier
additional signals - #1 filtered lateral accelerometer, airspeed transducer

9. #1 pitch rate gyro #2 vertical gyro #1 lateral accl a/s transducer
Yaw gyro
#1 pitch rate gyro
#2 vertical gyro
#1 lateral accl
a/s transducer

10. SAS 2 Components: Input Signals:
SAS2 is the SAS/FPS computer (digital)
Three SAS actuators
Input Signals:
Pitch - rate gyro in the #2 stabilator amplifier
Roll - roll rate gyro in the avionics compartment
Yaw - yaw rate gyro in the avionics compartment

11. SAS 2 Additional Signals #1 & #2 filtered lateral accelerometer
rate gyro in the #1 Stabilator amplifier
air data transducer

12. Yaw rate gyro
#1 & #2 lateral accl
Air data transducer
Roll rate gyro
#2 pitch rate gyro

13. TRIM SYSTEM
Purpose: Provide a gradient force, maintains position of the cyclic and tail rotor controls
Components:
two electromechanical actuators, and one electrohydromechanical actuator
TRIM REL switch on the cyclic, and pedal micro switches on the directional control pedals
monitored by the SAS/FPS computer

14. TRIM SYSTEM Slip Clutches
both the roll and yaw trim actuators incorporate slip clutches to allow the pilots to make control inputs should either actuator jam
13 pounds maximum in the roll
80 pounds maximum in the yaw

15. Airspeed transducer
#1 collective position sensors

16. FLIGHT PATH STABILIZATION
Purpose: Enhances static stability through long term rate dampening in the pitch, roll, and yaw axis.
Components: SAS/FPS computer, and three trim actuators
Control Authority: When coupled with trim, 100% control authority

17. FLIGHT PATH STABILIZATION
The following systems must be on and operational for FPS to function 100%
SAS 1 and/or SAS 2
Boost
Trim
Stabilator in AUTO mode enhances FPS operation, but is not required

18. FLIGHT PATH STABILIZATION
FPS provides the following functions:
BELOW
60 KIAS
ABOVE
Attitude Hold/
Airspeed Hold
Attitude Hold
Pitch Axis
Attitude Hold
Roll Axis
Attitude Hold
Heading Hold or
Turn Coordination
Heading Hold
Yaw Axis

19. Airspeed transducer
#1 collective position sensor
#1 pitch rate gyro
#1 vertical gyro
#1 vertical gyro
ASN 43
#1 lateral accl
Airspeed transducer
#1 collective position sensor

20. MALFUNCTION ANALYSIS

21. ON ON ON ON ON ON AUTO FLIGHT CONTROL SAS 1 SAS 2 TRIM FPS BOOST
FAILURE
ADVISORY
RESET
RESET ON ON
POWER ON RESET

22.  SAS 1 and FPS switchs - Off.
SAS Failure With No Failure/Advisory Indication.
 SAS 1 switch - Off.
If condition persists:
 SAS 1 switch - On.
 SAS 2 switch - Off.
If malfunction still persists:
 SAS 1 and FPS switchs - Off.

23. ON ON ON ON ON ON AUTO FLIGHT CONTROL SAS 1 SAS 2 TRIM FPS BOOST
FAILURE
ADVISORY
RESET
RESET
SAS2 ON ON
POWER ON RESET

24. 9.29.2 SAS2 Failure Advisory Light On.
Power On Reset switches - Simultaneously press and then release.

25. ON ON ON ON ON ON AUTO FLIGHT CONTROL SAS OFF SAS 1 SAS 2 TRIM FPS
BOOST
FAILURE
ADVISORY
RESET
RESET ON ON
POWER ON RESET

26. 9.29.3 SAS OFF Caution Light On.
FPS switch - Off.

27. ON ON ON ON ON ON AUTO FLIGHT CONTROL SAS OFF SAS 1 SAS 2 TRIM FPS
BOOST
FAILURE
ADVISORY
RESET
RESET ON ON
POWER ON RESET

28. ON ON ON ON ON ON AUTO FLIGHT CONTROL FLT PATH STAB SAS 1 SAS 2 TRIM
FPS ON ON ON ON
BOOST
FAILURE
ADVISORY
RESET
RESET ON ON
A /S
POWER ON RESET

29. 9.29.4 FLT PATH STAB Caution Light On.
 POWER ON RESET switches - Simultaneously press and then release.
WARNING
If the airspeed fault advisory light is illuminated, continued flight above 70 KIAS with the stabilator in the AUTO MODE is unsafe since a loss of the airspeed signal from the remaining airspeed sensor would result in the stabilator slewing full down.

30. 9.29.5 Pitch, Roll or Yaw/Trim Hardover.
POWER ON RESET switches - Simultaneously press and then release.
If failure returns, control affected axis manually.

31. LAND AS SOON AS PRACTICABLE.
Trim Actuator Jammed.
LAND AS SOON AS PRACTICABLE.

32. QUESTIONS ?