AFCS (OFT 8)

Question 1

What is the AFCS?

Answer 1

• automatic flight control system
• electrohydromechanical system
• 3 subsystems: SAS, Stab System, AFCC

Question 2

What is the AFCC?

Answer 2

• commands SAS and trim actuators in C/P/R/Y channels
• located in nose bay
• 2 types of control: inner-loop and outer-loop

Question 3

What is inner-loop control?

Answer 3

• SAS actuators
• fast control response
• limited to 10% authority
• does not move cockpit controls

Question 4

What is outer-loop control?

Answer 4

• trim actuators (or autopilot)
• limited to 10% per second of rate response
• has full authority (100%)
• moves cockpit controls

Question 5

What does the SAS do?

Answer 5

• Senses rate acceleration in P/R/Y

- inputs rate dampening for improved stability

Question 6

What is SAS 1?

Answer 6

• analog

- P/R/Y only

Question 7

What is SAS 2?

Answer 7

-digital

Same as SAS 1 but also has:

• hover augmentarion
• gust alleviation
• altitude hold
• coupler features
• turn coordination
• roll attitude hold

Question 8

What kind of pressure and from what does SAS get px?

Answer 8

• SAS actuators get hyd px from PAS module via SAS shutoff valve
• controlled by SAS/BOOST pushbutton

Question 9

When and why does the SAS caution illuminated?

Answer 9

• during loss of px OR when actuators lose electrical power (manual disengagement or power server)
• sensed by SAS px switch

Question 10

With both SAS actualtors what is control authority?

Answer 10

-P/R/Y have +/- 10% authority

———–thats’s +/- 5% authority from each channel

Question 11

What happens to control authority if either SAS fails?

What happens if SAS 1 fails?

What happens if SAS 2 fails?

Answer 11

• AFCS DEGRADED caution and SAS on fail cube
• remaining SAS works at +/- 5% control authority but at 2x the gain to compensate
• if SAS 1 fails: AFCC automatically disengaged affected axis
• if SAS 2 fails: pilot must manually disengage via AFCS panel

Question 12

5 “Holds”

19 functions

Answer 12

1. Attitude hold
2. Airspeed hold
3. Heading hold
4. BARALT hold
5. RADALT hold

Question 13

5 “Hovers”

19 functions

Answer 13

1. Auto approach
2. Coupled hover
3. Cable angle
4. Crew
5. Auto depart

Question 14

3 “ations”

19 functions

Answer 14

1. Turn coordination
2. Hover augmentation and gust alleviation
3. Stability augmentation (system)

Question 15

Last 6

19 functions

Answer 15

MT DABS

1. M = maneuvering stability
2. T = trims
3. D = diagnostic cubes
4. A = auto pre-flight check
5. B = blade fold assist
6. S = stabiliator

Question 16

Trim (19 functions)

Answer 16

-cyclic, collective, pedal

• pitch and roll have hydraulic trim servos (1000psi)
• collective and yaw have electric servos

-actuators command 100% control authority BUT are rate-limited to 10%/sec (outer-loop)

Question 17

How do you disengage yaw trim?

Answer 17

A/S < 50 KIAS = pedal microswitch

A/S > 50 KIAS = pedal microswitch AND cyclic trim release

Question 17

How do you disengage yaw trim?

Answer 17

A/S < 50 KIAS = pedal microswitch

A/S > 50 KIAS = pedal microswitch AND cyclic trim release

Question 18

Maneuvering stability

Answer 18

-engages by pushing AUTO PLT pushbutton on

-in AOB > 30°……..
longitudinal trim actuator pushes cyclic forward in a turn to “increase pilot effort” (i.e. false g-loading)

• 1% of fwd cyclic per 1.5°AOB (between 30-70° AOB)
• @ 70° AOB = 30% fwd cyclic

Question 19

Heading hold

Requirements, airspeed, re-engage

Answer 19

• to turn on: weight OFF wheels and AUTO PLT on
• disengaged with: WOW/on deck
• A/S < 50 KIAS: 3°/second
• A/S > 50 KIAS: 1°/click (less than a sec) OR 1°/sec
• to re-engage HH after turn, 2 things must be maintained for 2 seconds:
  1. 2° of wings level
  2. Yaw rate < 2°/sec

Question 20

RADALT Hold

Answer 20

• any airspeed and 0-5000’ AGL
• RADALT, SAS 2, TRIM, AUTO PLT must be on
• to change altitude, collective trim must be held until at new alt.
• in hover coupler mode: altitude controlled with HVR ALT knob will be limited to 1000 fpm climb and 200 for descent (starts automatically within 2ft of selected altitude on HVR ALT)

Question 21

BARALT hold

Answer 21

-turned on when BAR ALT, SAS 2, TRIM, AUTO PLT are on

• AFCC monitors engine Q and will stop collective increase if Q is pulled to:
• —‐—-106% (> 80 KIAS)
• ——–112% (< 80 KIAS)

-change altitude with collective trim release button (when depressed)

Question 22

Attitude hold

Answer 22

• A/S < 50 KIAS and AUTO PLT engaged

- 4 way trim switch changes 5°/second

Question 23

Airspeed Hold

Answer 23

Engaged with:

• AUTO PLT
• A/S > 50 KIAS
• AOB < 30°

-4 way teim switch controls at 6 KIAS/sec

Question 24

Pitch/roll hover augmentation and gust alleviation

Answer 24

- controlled by SAS 2 | - improved stability by maintaining attitude, lat/long acceleration to stop drift

Question 25

Turn coordination

Answer 25

- allows pilot to fly coordinated turns with directional control from AFCS at > 50 KIAS - udes lateral acceleration and roll rate to determine if in balanced flight - done by yaw SAS and yaw TRIM - engaged when heading hold off, and roll attitude is > 1° AND any of the following: - -----------lateral cyclic > 3% - -----------cyclic trim release pressed - -----------roll attitude > 2.5° (using 4-way trim switch)

Question 26

Hover coupler

Answer 26

- engaged after end of auto approach within 1kt of set airspeed OR manually within 5 kts - with SAS 2, TRIM, AUTO PLT, APPR/HVR - provides LAT/LONG groundswell control via LAT/LONG velocity potentiometers - AFCC monitors dual-engine Q to prevent collective increase if Q reaches 116% - warning, pay attention to airspeed, if you go above 50 KIAS you'll be put on air speed hold - limitednto 50kts fwd, 20 kts aft, 20 kts sideways - cannot exceed 1000 fpm clim or 200 fpm descent

Question 27

Crew hover

Answer 27

- allows aircrewman to contro/position hover when coupled - aircrww cyclic authority rated at +/- 5 KIAS - activatrd by CREW HVR pushbutton, but must be in coupled hover