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

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

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

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)

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

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.

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%

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

#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

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

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

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

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

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

Airspeed transducer #1 collective position sensors

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

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

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

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

MALFUNCTION ANALYSIS

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

 SAS 1 and FPS switchs - Off. 9.29.1 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.

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

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

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

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

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

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

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.

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.

LAND AS SOON AS PRACTICABLE. 9.29.6 Trim Actuator Jammed. LAND AS SOON AS PRACTICABLE.

QUESTIONS ?