8/13/2019 AFCS1

1/32

AUTOMATIC FLIGHTCONTROL SYSTEM

(AFCS)

Presented by

CW3 Martin Dadswell

8/13/2019 AFCS1

2/32

PURPOSE: To develop the StudentInstructor Pilots understanding of the

Automatic Flight Control System

NEED: You will be instructing this

subject in the near future

8/13/2019 AFCS1

3/32

TOPICS OF DISCUSSION

Auto Flight Control System

What is Stability?

Stability Augmentation System

TRIM

Flight Path Stabilization Malfunction Analysis

8/13/2019 AFCS1

4/32

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)

8/13/2019 AFCS1

5/32

WHAT IS STABILITY?

Create a cool drawing on the dry erase

board at this time.

8/13/2019 AFCS1

6/32

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 steadymotion.

8/13/2019 AFCS1

7/32

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%

8/13/2019 AFCS1

8/32

SAS 1

Components: SAS1 amplifier (analog) is located in the

avionics compartment

Three SAS actuators Input Signals:

Pitch - rate gyro in the #1 stabilator amplifier

Roll - pilots (number 2) vertical gyro Yaw - yaw rate gyro in the SAS1 amplifier

additional signals - #1 filtered lateral

accelerometer, airspeed transducer

8/13/2019 AFCS1

9/32

#1 pitch rate gyro

#2 vertical gyro

#1 lateral accla/s transducer

Yaw

gyro

8/13/2019 AFCS1

10/32

SAS 2

Components:

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

8/13/2019 AFCS1

11/32

SAS 2

Additional Signals

#1 & #2 filtered lateral accelerometer

rate gyro in the #1 Stabilator amplifier

air data transducer

8/13/2019 AFCS1

12/32

Roll rate gyro

#2 pitch rate gyro

Yaw rate gyro#1 & #2 lateral accl

Air data transducer

8/13/2019 AFCS1

13/32

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 microswitches on the directional control pedals

monitored by the SAS/FPS computer

8/13/2019 AFCS1

14/32

TRIM SYSTEM

Slip Clutches

both the roll and yaw trim actuators

incorporate slip clutches to allow the pilotsto make control inputs should either

actuator jam

13 pounds maximum in the roll

80 pounds maximum in the yaw

8/13/2019 AFCS1

15/32

Airspeed transducer#1 collective position sensors

8/13/2019 AFCS1

16/32

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 withtrim, 100% control authority

8/13/2019 AFCS1

17/32

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 FPSoperation, but is not required

8/13/2019 AFCS1

18/32

FLIGHT PATH STABILIZATION

FPS provides the following functions:

60 KIASBELOW ABOVE

Attitude Hold

Attitude Hold

Attitude Hold/

Airspeed Hold

Attitude Hold

Heading Hold

Pitch Axis

Roll Axis

Yaw AxisHeading Hold or

Turn Coordination

8/13/2019 AFCS1

19/32

Airspeed transducer

#1 collective position sensor

#1 pitch rate gyro

#1 vertical gyro#1 vertical gyro

ASN 43#1 lateral acclAirspeed transducer#1 collective position sensor

8/13/2019 AFCS1

20/32

MALFUNCTION ANALYSIS

8/13/2019 AFCS1

21/32

AUTO FLIGHT CONTROL

SAS 1 SAS 2 TRIM FPS

ON

BOOST FAILURE ADVISORY

ON

R

E

S

ET

POWER ON RESET

R

E

S

ET

ON ON ON ON

8/13/2019 AFCS1

22/32

9.29.1 SAS Failure With No

Failure/Advisory Indication.SAS 1switch - Off.

If condition persists:

SAS 1switch - On.

SAS 2switch - Off.

If malfunction still persists:

SAS 1 andFPSswitchs - Off.

8/13/2019 AFCS1

23/32

AUTO FLIGHT CONTROL

SAS 1 SAS 2 TRIM FPS

ON

BOOST FAILURE ADVISORY

ON

R

E

S

ET

POWER ON RESET

R

E

S

ET

ON ON ON ON

SAS2

8/13/2019 AFCS1

24/32

Power On Resetswitches - Simultaneously press and then release.

9.29.2 SAS2 Failure Advisory Light On.

8/13/2019 AFCS1

25/32

AUTO FLIGHT CONTROL

SAS 1 SAS 2 TRIM FPS

ON

BOOST FAILURE ADVISORY

ON

R

E

S

ET

POWER ON RESET

R

E

S

ET

ON ON ON ON

SAS OFF

8/13/2019 AFCS1

26/32

9.29.3 SAS OFF Caution Light On.

FPSswitch - Off.

8/13/2019 AFCS1

27/32

AUTO FLIGHT CONTROL

SAS 1 SAS 2 TRIM FPS

ON

BOOST FAILURE ADVISORY

ON

R

E

S

ET

POWER ON RESET

R

E

S

ET

ON ON ON ON

SAS OFF

8/13/2019 AFCS1

28/32

AUTO FLIGHT CONTROL

SAS 1 SAS 2 TRIM FPS

ON

BOOST FAILURE ADVISORY

ON

R

E

S

ET

POWER ON RESET

R

E

S

ET

ON ON ON ON

A /S

FLT PATH STAB

8/13/2019 AFCS1

29/32

9.29.4 FLT PATH STAB Caution Light On.

POWER ON RESETswitches - 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.

8/13/2019 AFCS1

30/32

9.29.5 Pitch, Roll or Yaw/Trim Hardover.

POWER ON RESETswitches - Simultaneously press and then release.

If failure returns, control affected axis manually.

8/13/2019 AFCS1

31/32

9.29.6 Trim Actuator Jammed.

LAND AS SOON AS PRACTICABLE.

8/13/2019 AFCS1

32/32

QUESTIONS

?