HSC-3 FRS > AFCS > Flashcards

AFCS Flashcards

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1
Q

What is the purpose of the AFCS?

A

It is an electrohydromechanical system that provides inputs to the flight control system to assist the pilot in maneuvering and handling the helicopter

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2
Q

What are the three major subsystems of the AFCS?

A
  1. SAS (Stability Augmentation System)
  2. Stabilator
  3. AFCC (Advanced Flight Control Computer)
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3
Q

What are the 18 functions of the AFCS?

5-Holds, 4-Hovers, 3-ations, and MTDABS

A
  1. Attitude Hold (Pitch/Roll)
  2. Airspeed Hold
  3. Heading Hold
  4. RAD ALT Hold
  5. BAR ALT Hold
    —
  6. Automatic approach to a hover
  7. Hover coupler
  8. Crew hover
  9. Automatic departure
    —
  10. Pitch, roll, and yaw stability augmentation
  11. Pitch/roll hover augementation/gust alleviation
  12. Turn coordination
    —
  13. Maneuvering stability
  14. Trim (collective, cyclic, and pedal)
  15. Diagnostics
  16. Automatic preflight check
  17. Blade fold
  18. Stabilator control
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4
Q

What is the central control of the AFCS?

A

The AFCC

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5
Q

What does the AFCC do?

A

It commands the SAS actuators and trim actuators in all four control channels

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6
Q

What are the two types of control that the AFCC employs? What is an example of each?

A
  • Inner loop (SAS)
  • Outer loop (Autopilot)
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7
Q

What does inner-loop control do?

A

It employs rate damping to improve dynamic helicopter stability

Characteristics:
* Fast in response
* Limited in authority
* Operates without movement of flight controls

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8
Q

What does outer-loop control do?

A

Provides long-term inputs by trimming the flight controls to the positions required to maintain the selected flight regime

Characteristics:
* Has 100% authority (meaning it can drive flight controls through their full range)
* Limited to a rate of 10% per second

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9
Q

What is the primary purpose of the stabilator?

A

To provide angle of attack stability

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10
Q

How does the the stabilator system work?

A

Two electric jackscrew actuators position the stabilator and is controlled by a separate stabilator amplifier

Each actuator provides 1/2 of the input

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11
Q

What four inputs does the stabilator amplifier require to position the stabilator?

CLAP

A
  1. Collective position
  2. Lateral acceleration
  3. Airspeed
  4. Pitch rate
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12
Q

If a stab actuactor fails in the full-down position, what is the travel restriction?

A

Travel is restricted to 35°

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13
Q

If a stab actuactor fails in the full-up position, what is the travel restriction?

A

Travel is restricted to 30°

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14
Q

What is the airspeed limit when the stabilator is fixed in the 0° position?

A

150 KIAS

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15
Q

What is the airspeed limit when the stabilator is fixed in the 10° position?

A

100 KIAS

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16
Q

What is the airspeed limit when the stabilator is fixed in the 20° position?

A

80 KIAS

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17
Q

What is the airspeed limit when the stabilator is fixed in the 30° position?

A

60 KIAS

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18
Q

What is the airspeed limit when the stabilator is fixed in the 40° position?

A

45 KIAS

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19
Q

What is the purpose of SAS?

A

Provides increased stability by sensing acceleration rate in the pitch, roll, and yaw axes and applying proportionate control inputs to dampen out the sensed rate

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20
Q

What kind of system is SAS 1?

A

An analog system

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21
Q

What kind of system is SAS 2?

A

A digital system that is a part of the AFCC

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22
Q

What authority does the SAS actuators have when both channels are engaged?

A

The actuators have ±10% control authority with each channel providing ±5%

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23
Q

What happens if SAS 1 fails?

A

It must manually be disengaged

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24
Q

What happens if SAS 2 fails?

Study These Flashcards
A

It will automatically be disengaged by the AFCC

25
What conditions are required for the AFCC preflight check? | **CREEW**
1. Computer power on for 20 secs **AND** SAS 1 is engaged 2. Rotor Brake — ON 3. Engine TRQs less than 10% 4. EGI attitudes valid (both) 5. Weight on wheels
26
What flight control authority does TRIM have?
It has 100% authority in all channels
27
What is the normal automatic approach profile?
When above 40 KGS: * 2.5 kts per sec deceleration * 215 fpm descent rate When below 40 KGS: * 1.5 kts per sec deceleration * 130 fpm descent rate
28
What does the auto-pilot do if you are **above** the approach profile on an automatic approach?
* Airspeed hold * 360 fpm descent rate
29
What does the auto-pilot do if you are **below** the approach profile on an automatic approach?
* 2.5 kts per sec deceration * RAD ALT hold
30
What profile does the automatic departure take you to?
* 150’ AGL * 120 KIAS ## Footnote **Climb @ 240fpm When less than 85 KIAS, you'll accelerate at 3kts/sec When above 100 KIAS, you'll accelerate at 1kts/sec**
31
What happens when you press the DEPART HOV button a second time while on the automatic departure profile?
It terminates both climb and acceleration **and** engages RAD ALT hold If above 50 KIAS: * Airpseed hold is engaged If below 50 KIAS: * Attitude hold is engaged
32
What are the AFCS requirements for an automatic approach?
* SAS 2 * Trim * Autopilot * RAD ALT * Both EGIs **with the #2 EGI giving heading and velocity**
33
Why does the AFCS recieve a torque signal from the EDECU?
So the AFCS knows not to exceed the set engine torque limits to attempt to hold its trim parameters
34
What does the AFCS DEGRADED caution mean?
* Failure of one or more AFCC modes
35
What does the AFCC I/O FAIL caution mean?
The AFCC has lost power ## Footnote Accompained with an AFCS DEGRADED caution
36
What does the SAS caution mean?
* The loss of hyd pressure to the pilot-assist servos assembly **or** * Loss of electric power to both SAS 1 and SAS 2 ## Footnote A SAS 1 or SAS 2 fail are usually but not necessarily followed by this caution
37
What does the RAD ALT caution mean?
Failure of all of the following: * Pilot FD RAD ALT data * Co-pilot FD RAD ALT data * MD digital interface
38
What functions does the CILA (Collective Inter-Loop Actuator) give us?
1. Hover augmentation/gust alleviation 2. Turn coordination 3. Attitude Hold (Roll) 4. Altitude Hold 5. Coupled Hover functions
39
Why do we check "stabililator programming" on the first T/O of the day?
To verify that the stabilator will program up. During the stabilator ground checks, we only test that the stab programs down.
40
What are the control mixing compensations (mechanical and electrical)?
Mechanical Compensation: * Collective to yaw * Collective to lateral * Collecitve to longitudinal * Yaw to longitudinal Electronic Compensation: * Collective/airspeed to yaw
41
Collective to Yaw | Mechanical Compensation
* **Action:** Nose yaws right when collective is increased * **Compensation:** T/R thrust is increased
42
Collective to Lateral | Mechanical Compensation
* **Action:** Helicopter drifts right when collective is increased * **Compensation:** Rotor disc is tilted left
43
Collective to Longitudinal | Mechanical Compensation
* **Action:** When collective is increased, the nose pitches up and helicopter drifts aft * **Compensation:** Rotor disc is tilted forward
44
Yaw to Longitudinal | Mechanical Compensation
* **Action:** When left pedal is applied, the nose pitches down and the helicopter drifts forward * **Compensation:** Rotor disc is tilted aft
45
Collective/airspeed to Yaw | Electronic Compensation
* **Action:** Nose yaws left as airspeed increases * **Compensation:** A portion of the M/R torque compensation is provided by a trim input
46
When does **attitude hold** take effect?
At airspeeds less than 50 KIAS ## Footnote **Using the trim switch, attitude will change at a rate of 5° per second.**
47
When does **airspeed hold** take effect?
At airspeeds greater than 50 KIAS and bank angles less than 30° ## Footnote **Using the trim switch, airspeed will change at a rate of 6 KIAS per second**
48
How is **heading hold** engaged? How is it disengaged?
It is engaged via the AUTO PLT pushbutton. It is disengaged with the weight on wheels switch.
49
How do you disengage heading hold in flight **below 50 KIAS**?
By depressing either tail rotor pedal microswitch
50
How do you disengage heading hold in flight **above 50 KIAS**?
By depressing both tail rotor pedal microswitches **and** the cyclic trim release button
51
At airspeeds **below 50 KIAS**, how does the collective HDG TRIM switch change heading hold?
It slews the aircraft at a rate of 3° per second
52
At airspeeds **above 50 KIAS**, how does the collective HDG TRIM switch change heading hold?
If the switch is actuated for **less than one second:** * Provides a 1° heading change If the switch is actuated for **more than one second:** * Provides a 1° per second coordinated turn
53
When does the hover coupler engage on an automatic approach?
When the longitudinal groundspeed is: * Within 1 KGS of the selected LONG VEL (longintudinal velocity) **OR** * Within 5 KGS if engaged manually
54
When does RAD ALT hold engage automatically on an automatic approach?
When the aircraft altitude is within 2' of the selected altitude on the HVR ALT potentiometer
55
How much can the coupled hover longitudinal and lateral groundspeed be varied with the four-way trim switch **on the pilot's cyclic**?
±10 KGS
56
How much can the coupled hover longitudinal and lateral groundspeed be varied in crew hover mode with the **crew hover trim grip**?
±5 KGS ## Footnote **This is in addition to the speed selected on the pilot's cyclic four-way trim switch.**
57
When is automatic turn coordination engaged?
When roll attitude is greater than 1° **AND** any of the following conditions are met: * Lateral cyclic displacement is greater than 3% * Cyclic trim button is pressed * Roll attitude exceeds a 2.5° AOB using the 4-way trim switch * HDG trim switch is toggled for more than 1 second
58
How does manuvering stability work?
It commands 1% forward cyclic for every 1.5° AOB between 30-75° ## Footnote Only starts at AOBs greater than 30°
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