Automatic Flight Control System CW2 Ray Freeman

OBJECTIVE Develop the student instructor pilots understanding of the Automatic Flight Control System

Reasons for AFCS???? Enhances the handling qualities of the aircraft through varying flight regimes.

ELEMENTS AFCS components and location Functions of SAS, Trim, & FPS Operations Emergency Procedures/Limitations

REFERENCES TM 1-1520-237-10 TM 11-1520-237-1 Flight Line Supplement AFCS Student Handout

SUBSYSTEMS SAS TRIM FPS STABILATOR

SAS Enhances dynamic stability through short term rate dampening in the pitch, roll, and yaw axis.

COMPONENTS/LOCATION SAS 1 Amplifier- Avionics compartment SAS 2 Amplifier- SAS 2/FPS computer

SAS Cont. Each SAS has 5% control authority up to a total of 10%. If one SAS is turned off or inop, the other SAS doubles its gain but still only has 5% control authority. SAS 1 has no diagnostic capability Malfunction of SAS 2 will be indicated by a SAS 2 failure advisory light

TRIM Provides a gradient force, maintains position of the cyclic and tail rotor controls, and provides the “muscles” for FPS.

Yaw Trim Proper operation requires that the Boost be on and pressurized. Electromechanical actuator that incorporates a slip clutch in the event the actuator jams. (80 lbs) Trim/FPS hardover will result in 1/4 inch pedal movement Reference is changed by pressing micro switches on the pedals and release.

Roll Trim Electromechanical actuator with slip clutch. Force required to override the clutch is 13 lbs. Located on the cabin top under the control access. Roll Trim/FPS hardover will result in 1/2 inch cyclic displacement. Reference is reset using the trim release switch or stick trim switch.

Pitch Trim Hydroelectromechanical actuator that operates in conjunction with the SAS/FPS computer. Located on the cabin top above the pitch boost servo. Hydraulic pressure is 1000 lbs. Pitch Trim/FPS hardover results in about 1/2 inch cyclic displacement.

Flight Path Stabilization Basic autopilot that enhances static stability through long term rate dampening in the pitch, roll, and yaw axis. Must be coupled with Trim to operate. With Trim, FPS has 100% control authority. Since the Trim actuators are the muscle, the controls in the cockpit will move.

Trim Boost Mixing Unit Control Inputs

SAS Trim Boost Mixing Unit Control Inputs

FPS Cont. Requires Boost,SAS 1 or 2, Trim to operate. Although not required for proper operation, the FPS performance will be improved by the proper operation of the stabilator in the auto mode.

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

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

Functions < 60 kts > 60 kts ATT HOLD ATT HOLD Pitch A/S HOLD* Roll ATT HOLD ATT HOLD HDG HOLD HDG HOLD Yaw or Turn Coord.

Malfunctions & Emergency Procedures

If condition persists:  SAS 1 switch - On.  SAS 2 switch - 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 switches - Off.

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

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

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

POWER ON RESET switches - Simultaneously press and then release. 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.

Review and Questions