Flight Control System Flashcards
What are the three sections of the flight control system?
[H] “MAF”
- Mechanical control system
- Flight control servo system
- Automatic flight control system
.
Where are the cyclic, collective, and tail rotor pedal flight controls routed?
Aft and outboard of each pilot seat, vertically up each side of the aircraft
What does the tail rotor control system provide?
Directional control by varying the pitch of the tail rotor blades
What (2) sources power the tail rotor servo?
- No. 1 hydraulic system
- Backup hydraulic system
The use of dual systems ensures reliability in directional control.
What happens when either tail rotor cable becomes severed?
(Think Caution)
Microswitches activate the TAIL ROTOR QUADRANT caution
How many primary servos are located in the hydraulics bay? Check me
Three primary servos
Each primary servo has redundant features for safety.
What occurs if one primary servo stage becomes inoperative?
[Think Caution]
A bypass valve opens, and the #1/#2 PRI SERVO PRESS caution appears
This mechanism ensures continued control despite a failure.
What does the pilot-assist servo assembly contain?
Three part anwser// [H]: 2 ANSWER share a button
- Boost servos
- SAS actuators
- Hydraulic (pitch and roll) trim actuators
These components help reduce pilot workload and enhance control.
What is the function of boost servos?
Reduce cockpit control forces and SAS system feedback
Boost servos are critical for making control inputs easier.
Fill in the blank: The cyclic, collective, and pedal controls are mechanically combined in the _______.
[mixing unit]
This combination allows for effective airframe response characteristics.
Delete
What type of mixing is present when trim is engaged? Revise question
Electrical (collective/airspeed-to-yaw) mixing
This mixing enhances the responsiveness of the helicopter to pilot inputs.
What does AFCS stand for?
Automatic Flight Control System
What type of system is the AFCS?
It combines the elements of mutiple systems / three parts make it work
Electro+hydro+mechanical system
What are the three major subsystems of the AFCS?
- Stability Augmentation System (SAS)
- Stabilator system
- Advanced Flight Control Computer (AFCC)
True or False: Each subsystem of the AFCS operates independently.
True
What feature of the AFCS provides pitch, roll, and yaw stability augmentation?
Stability Augmentation System (SAS)
List three features provided by the AFCS.
- Pitch and roll attitude hold
- Airspeed hold
- Automatic approach to hover
List two types of altitude hold provided by the AFCS.
- Barometric altitude hold
- Radar altitude hold
What is the function of the automatic depart feature in the AFCS?
Facilitates automatic departure
What does the term ‘turn coordination’ refer to in the context of the AFCS?
Coordinating turns for stability
What feature of the AFCS aids in maneuvering stability?
Maneuvering stability
True or False: The AFCS includes an automatic preflight check.
True
What does the pitch and roll hover augmentation feature do?
Augments hovering capabilities and alleviates gusts
What happens when there is an AFCS mode failure?
DEL
AFCS DEGRADED caution appears and the appropriate mode failure capsule is activated
Except for stabilator failures.
What is the central component of the AFCS?
Digital advanced flight control computer (AFCC)
Commands SAS actuators and trim actuators.
What are the two types of control employed by the AFCC? Refer to Loops
- Inner-loop (SAS)
- Outer-loop (autopilot)
What is the primary purpose of the stabilator system?
To provide angle of attack stability
Helps stabilize the aircraft in both angle of attack and maneuvering stability.
What are the four inputs required to position the stabilator?
C.L.A.P
- Collective position
- Lateral acceleration
- Airspeed
- Pitch rate
What is the function of the SAS?
Increases stability by sensing acceleration rate and applying control inputs
Works in pitch, roll, and yaw axes.
True or False: SAS 1 is a digital system.
False
SAS 1 is an analog system.
What happens if either SAS channel malfunctions?
AFCS DEGRADED caution appears and the appropriate SAS fail advisory light illuminates.
What are the two types of altitude hold available in the autopilot system?
- Barometric altitude hold (BAR ALT)
- Radar altitude hold (RAD ALT)
Fill in the blank: The stabilator travels from _____ for hover and low-speed flight to _____ for cruise and maneuvering flight.
42° trailing-edge down, 10° trailing-edge up
What is the maximum rate of change for the autopilot’s airspeed hold feature?
6 KIAS per second
Above 50 KIAS.
What is the maximum control authority for SAS channels when both are engaged?
±10 percent control authority
Each channel provides ±5 percent.
When is heading hold disengaged?
(On the ground vs in flight)
With weight on wheels or below 50 KIAS by depressing tail rotor pedal microswitches.
True or False: The trim system uses only electric servos.
False
It uses both electric and hydraulic servos.
What occurs during a total AC power failure regarding the AFCC?
AFCC computer power is interrupted and must be cycled after power restoration.
What is the role of the collective inner-loop actuator (CILA)?
Required for hover augmentation, gust alleviation, turn coordination, roll attitude hold, altitude hold, and coupler functions.
What happens if the stabilator system malfunctions? 3 Things
Automatic power shutdown to both actuators, warning tone, and STABILATOR caution appears.
What should the PNAC do in the event of a runaway down stabilator?
Disengage the automatic mode by activating manual mode slewing.
Fill in the blank: The stabilator may fail without illumination of the associated caution and aural warning tone, with the initial indication being an uncommanded _____ change during flight.
pitch
What is the purpose of the stabilator position indicator? DEL
Assists the pilot in manually slewing the stabilator to a desired position.
What is the altitude range for engaging RAD ALT hold?
0 to 5,000 feet Above Ground Level (AGL)
In hover coupler mode, how is altitude the aircraft is sitting at determined
HVR ALT knob
What are the maximum climb and descent rates when transitioning to another altitude in hover coupler mode?
- Climb: 1,000 feet per minute
- Descent: 200 feet per minute
What happens if RAD ALT hold mode fails?
BAR ALT hold is automatically engaged
What can cause altitude hold to disengage?
Malfunction in the engine torque indication system
What is a potential consequence of using the four-way cyclic TRIM switch continuously?
The aircraft may enter a descent with altitude hold engaged
True or False: RAD ALT hold may decouple when flying over the deck of a ship.
True
What indications will illuminate if RAD ALT hold decouples? DEL
- AFCS DEGRADED caution
- MASTER CAUTION
What environmental condition may make BAR ALT hold difficult to engage?
Electromagnetic environment
What is the purpose of maneuvering stability?
To increase pilot effort required to maintain a given pitch rate at bank angles > 30°
This feature alerts the pilot to g-loading during maneuvering flight.
At what altitude and airspeed can I engage automatic approach
Activate the automatic approach pushbutton (APPR/HVR) at any airspeed and altitude < 5,000 feet AGL
What happens if torque reaches or exceeds limitations during an automatic approach?
The AFCC stops increasing collective
This ensures the aircraft does not exceed torque limitations.
What does the hover coupler engage based on?
Longitudinal groundspeed within 1 KGS of selected LONG VEL after automatic approach or within 5 KGS if engaged manually
Radar altitude hold engages when altitude is within 2 feet of selected altitude.
What occurs when the automatic depart mode is engaged?
The aircraft accelerates to 120 KIAS and climbs to 150 feet AGL
The AFCC monitors dual-engine torque and adjusts collective accordingly.
What happens if the stored roll attitude is < 5° angle of bank during automatic departure?
The AFCS levels the wings and maintains heading as the aircraft accelerates through 50 KIAS
If > 5° angle, it maintains coordinated turn for established bank angle.
What does the crew hover feature allow, AWs to do?
Allows the aircrewman to position the helicopter while in a coupled hover
Controlled using the HOVER TRIM CONTROL panel.
What initiates the automatic preflight check of SAS components?
Pressing the SAS 1 pushbutton with conditions met:
* Weight on wheels
* Rotor brake on
* Engine torques < 10%
* Both EGI attitudes valid
* SAS 1 pushbutton engaged after AFCC on for at least 20 seconds
If conditions change, the AFCC CMPTR PWR/RESET button must be cycled.
How long does the automatic preflight check take to complete?
Approximately 10 seconds
It checks the response of rate gyros against a digital model.
Fill in the blank: The AFCS positions the cyclic, collective, and tail rotor pedals prior to the _______ sequence
[blade-fold sequence]
What inputs are transferred to the swashplate assembly?
Fore, aft, and lateral inputs
These inputs are essential for adjusting the helicopter’s pitch and roll.
What mechanism is used to transfer yaw inputs to the tail rotor servo?
Tail rotor cables
This mechanism is vital for controlling the helicopter’s yaw.
How is the tail rotor servo actuated/ what moves the pitch change shaft?
Mechanically actuated but requires hydraulic pressure to operate the pitch change shaft
What is the function of the tail rotor quadrant?
Transmits tail rotor cable movement to the tail rotor servo
What do the spring cylinders connected to the quadrant do?
Maintain cable tension if either tail rotor cable becomes severed
What activates the TAIL ROTOR QUADRANT caution? Z
Microswitches when either cable is broken
How is directional control of the tail rotor maintained if one cable is severed?
By the remaining spring
What happens if both tail rotor cables are severed?
Two separate centering springs counter the tail rotor servo pilot valve positioning the tail rotor to a neutral setting
What capability does a neutral setting of the tail rotor provide?
Fly-home capability
What does the flight control servo system consist of? (3)
Primary servos, tail rotor servos, and pilot-assist servos
What happens if the first stage of the tail servo loses hydraulic pressure?
The backup pump powers the second stage
What cautions and advisories illuminate when the backup pump powers the second stage?
- # 1 TAIL RTR SERVO caution
- # 2 TAIL RTR SERVO ON advisory
- BACKUP PUMP ON advisory
Can flight controls operate without hydraulic pressure to the pilot-assist servos?
Yes
What is required to move the primary servos?
Hydraulic power
How are pilot-assist servos turned on and off?
By pressing the SAS/BOOST pushbutton
If SAS/ boost controls pressure to the servos then what controls hyd px to pitch and roll trim actuators?
TRIM pushbutton
How many boost servos are there, now list them. [H: Which control movements are boosted]
- Collective
- Yaw
- Pitch
What is the function of the SAS actuator? DELETE
Provides rate damping
What controls are mechanically combined in the mixing unit? Like the things that I touch
- Cyclic
- Collective
- Pedal
Fill in the blank: The pilot-assist servos, except _______ and roll trim, are turned on and off by pressing the SAS/BOOST pushbutton.
Pitch
What does AFCS stand for?
Automatic Flight Control System
AFCS is an electrohydromechanical system for helicopter flight control.
What is the function of the inner-loop (SAS) in the AFCC?
Employs rate damping to improve dynamic helicopter stability
It operates without movement of the flight controls.
What does the outer-loop (autopilot) do?
Provides long-term inputs by trimming the flight controls
It can drive the flight controls through their full range of travel.
How fast can the outer-loop drive the flight controls?
At a limited rate of 10 percent per second
Can the pilot override the inner-loop and outer-loop functions?
Yes, the pilot can make normal flight control inputs to override both functions.
While hovering or in low speed flight, why is the stab programming down?
Eliminates undesirable nose-up attitudes caused by rotor downwash
The stabilator aligns with rotor downwash in low-speed flight.
What is the travel range of the stabilator?
From 42° trailing-edge down to 10° trailing-edge up
What does the collective position input do?
Decouples aircraft pitch response when collective position is changed
What restrictions apply to stabilator travel in case of actuator failure?
Restricted to 35° if an actuator fails down, 30° if it fails up
True or False: The stabilator system is completely dependent on the AFCS.
False
The stabilator is independent except for common sensors.
What may be the initial indication of stabilator failure?
An uncommanded pitch change during accelerated or decelerated flight
This indicates that the stabilator may fail without illumination of the associated caution and aural warning tone.
What happens if accelerated flight is continued with the stabilator in the full down position?
Longitudinal control will be lost
At slow speeds, what may occur with the stabilator fixed at or near 0°?
Nose-high attitudes may occur
How many channels does the SAS have?
Two separate and independent channels
What are the types of SAS channels?
- SAS 1 (analog system)
- SAS 2 (digital system that is part of the AFCC)
What occurs if SAS 2 fails?
The AFCC will automatically disengage the affected axis
If SAS one fails will it automatically disengage by it`s self?
No the pilot needs to Manually disengage SAS 1 using the AFCS CONTROL panel
What is the control authority of the remaining operable SAS channel after a failure?
Limited to ±5 percent authority, but operates at twice its normal gain
When does the SAS caution appear?
Whenever SAS 1 and SAS 2 lose electrical power or when hydraulic pressure is lost to the actuators
What is required for yaw trim disengagement above 50 KIAS?
Pedal microswitches and cyclic TRIM REL button must be pressed simultaneously
Delete
What does the autopilot maintain during cruise flight?
Helicopter pitch and roll attitude, airspeed, heading
The autopilot also provides a coordinated turn feature at airspeeds above 50 KIAS.
What does the AFCC do in relation to the autopilot?
Sends command signals to the trim actuators to reposition the flight controls
At what airspeed is the airspeed hold engaged / with angles of banks at what?
Above 50 KIAS with angles of bank less than 30°
Engaging the four-way TRIM switch changes the airspeed reference at a rate of 6 KIAS per second.
What happens when the four-way TRIM switch is actuated laterally?
The helicopter roll attitude changes at a rate of 6° per second
This is part of the roll attitude maintenance function.
Delete
What does the collective/airspeed-to-yaw electrical mixing control?
It reduces left yaw as airspeed increases
This is controlled through the collective position sensor and an airspeed signal.
True or False: Uninterrupted use of the four-way cyclic TRIM switch can cause a descent with altitude hold engaged.
True
How does maneuvering stability increase pilot effort?
By displacing the cyclic forward at bank angles greater than 30°
What is the maximum deceleration rate change during an automatic approach?
±1 knot per second
What happens when the cyclic TRIM REL button is pressed in a coupled hover?
Removes cyclic four-way TRIM switch inputs, returning to LONG VEL and LAT VEL settings
How is the crew hover trim grip controlled?
It has a control authority of ±5 KGS laterally and longitudinally.Using the HOVER TRIM CONTROL panel and cyclic four-way TRIM switch
It has a control authority of ±5 KGS laterally and longitudinally.
What is the purpose of the automatic preflight check provided by the AFCC?
To check SAS components prior to flight
It is initiated using the SAS 1 pushbutton under specific conditions.
What must be done if any of the preflight conditions change?
Flight Control System
Cycle the AFCC CMPTR PWR/RESET button and wait 20 seconds
This is needed before the test will initiate again.
What does RADALT stand for?
Radar Altimeter
What happens to the radar altimeter dial during a RADALT failure?
Declutters and displays red Xs in digital readout
What must be done to deselect HVR after a failure?
HVR must be manually deselected on AFCS control panel
What is the aircraft response when RADALT disengages?
BAR ALT hold engages at failure altitude; >50 KIAS - airspeed hold; <50 KIAS - attitude hold
What remains engaged after APPR/HVR/DEPART disengages?
RAD ALT hold remains engaged, but is degraded
What autopilot functions are lost after a RADALT failure?
All other autopilot functions lost
Fill in the blank: The DEPART function is _______ after a RADALT failure.
not available
True or False: The HVR function remains engaged after a RADALT failure.
True
SAS provides stability by sensing acceleration & dampening what 3 channels?
Pith
Roll
Yaw
What are the 4 sections of the flight controls?
Mechanical
Servos
AFCS
Tail Rotor
How many degrees are the blade tips swept by and for what reason?
20 degrees, for sound attenuation & efficiency
How many degrees is the tail rotor tilted & how much
lift in a hover does it provide?
20 degree tilt, 2.5 % lift
In a tail rotor failure, what two speed provide balanced flight?
25 & 145 KIAS
What do the elastomeric bearings do?
Allow for lead, lag, droop & flap
Name the 18 functions of the AFCSName the 18 functions of the AFCS
(1)Pitch, roll, & yaw stability augmentation
(2)Stabilator control
(3)Cyclic collective & pedal trim
(4)Pitch & roll attitude hold
(5)Airspeed hold
(6)Heading hold
(7)Barometric altitude hold
(8)Radar altitude hold
(9)Pitch/Roll hover augmentation/gust alleviation
(10)Turn coordination
(11)Maneuvering stability
(12)Automatic approach to a hover
(13)Hover coupler
(14)Auto depart
(15)Crew hover
(16) Blade fold assist
(17) Automatic preflight check
(18)Diagnostics (failure advisory)
