Flight Controls Flashcards
Flight Controls Description and Operation
The CH-47F Flight Control system uses two Flight Control Hydraulic Systems, two digital automatic flight control systems (DAFCS), first and second stage mixing units secondary controls that add features, and the linkage and connecting rods that connect and transmits control movements from the cockpit controls to the rotor heads
The Flight Control System is divided into seven main sections
(1) Cockpit Controls
(2) Closet Controls
(3) First and Second-Stage Mixing Controls
(4) Forward Upper Controls
(5) Tunnel Controls
(6) Aft Fuselage Controls
(7) Aft Upper Controls
The purpose of the flight control system is to
transmit control movements from the cockpit to the swashplates.
Control inputs from the cockpit are transmitted through ________ _________ to the rotary wing assemblies.
Control inputs from the cockpit are transmitted through mechanical linkage to the rotary wing assemblies.
_______ _______ assist in the mechanical linkage movements, and without ______ ________ the flight controls can not be moved.
Hydraulic actuators assist in the mechanical linkage movements, and without hydraulic pressure the flight controls can not be moved.
The forward tilt of the forward transmission is __ degrees while the aft transmission is __ degrees.
The forward tilt of the forward transmission is 9 degrees while the aft transmission is 4 degrees.
The preset forward tilt of these two transmissions provides a forward propulsive force to aid in _______ ________.
The preset forward tilt of these two transmissions provides a forward propulsive force to aid in ground taxiing.
Programmed cyclic tilt of the rotor discs (forward and aft) is provided by the _________ _________ ________ (___J system which are electrical actuators attached to the swashplates.
Programmed cyclic tilt of the rotor discs (forward and aft) is provided by the Longitudinal Cyclic Trim (LCT) system which are electrical actuators attached to the swashplates.
As airspeed increases ________ ________ increases to minimize fuselage pitch and attitude changes.
This directs the propulsive force more forward at higher airspeeds; reduces _______ _______, stress on the _______ _______ ______, fuselage ______ __ ______, allowing for a higher velocity, not to exceed airspeed limits.
As airspeed increases forward tilt increases to minimize fuselage pitch and attitude changes.
This directs the propulsive force more forward at higher airspeeds; reduces blade flapping, stress on the aft vertical shaft, fuselage angle of attack, allowing for a higher velocity, not to exceed airspeed limits.
Four control axis are identified by the helicopter response to the control input:
(1) Thrust
(2) Pitch
(3) Roll
(4) Yaw
When the thrust control is raised, the ______ ______ _______ of all six rotor blades increases, causing the aircraft to ascend.
When the thrust control is raised, the collective pitch angle of all six rotor blades increases, causing the aircraft to ascend.
Longitudinal control of tandem helicopters is accomplished through _______ _______ ______ (___).
Longitudinal control of tandem helicopters is accomplished through differential collective pitch (DCP).
____ varies the amount of thrust produced by the forward and aft rotors systems, creating pitch attitude changes of the fuselage in the pitch axis.
DCP varies the amount of thrust produced by the forward and aft rotors systems, creating pitch attitude changes of the fuselage in the pitch axis.
Forward cyclic input _______ ______ (collective pitch) in the forward rotor system and _______ ______ in the aft rotor system an equal amount, causing the aircraft to pitch nose down and increase airspeed.
Forward cyclic input decreases thrust (collective pitch) in the forward rotor system and increases thrust in the aft rotor system an equal amount, causing the aircraft to pitch nose down and increase airspeed.
Aft cyclic input ______ the thrust in the forward rotor system and ______ thrust in the aft rotor system causing the aircraft to pitch nose up, decrease airspeed and move aft.
Aft cyclic input increases the thrust in the forward rotor system and decreases thrust in the aft rotor system causing the aircraft to pitch nose up, decrease airspeed and move aft.
What is the Digital Advanced Flight Control System (DAFCS)?
A limited authority system that provides basic aircraft stability/hold features and desirable handling characteristics when the AFCS System SEL switch is placed to 1, 2, or BOTH.
What are the three different DAFCS control regimes?
- Ground Regime
- Low Speed Regime
- Forward Flight Regime
What does ‘Stability’ indicate in the context of DAFCS?
A lack of integral feedback, meaning the aircraft may not hold the desired heading, altitude, bank angle, or velocity in response to an aircraft trim change.
What does ‘Hold’ indicate in the context of DAFCS?
Integral feedback is present, and after an aircraft trim change, the new heading, altitude, bank angle, or velocity will remain secure.
What are the core features of DAFCS?
- Pitch Attitude Stability
- Longitudinal Static Stability
- Airspeed Stability
- Rate Dampening
- Control Response Quickening
What are the pilot-selectable native features in DAFCS?
- Deceleration (DECEL) (<65 knots to 1 knot)
- Position Hold (PSN) (<1 knot)
- Inertial Altitude Hold (ALT-INRT) (All Speeds)
- Radar Altitude Hold (ALT-RAD) (All Speeds)
- Descent (<65 knots must be used with DECEL)
- Roll Wings Level Mode (LEVEL or RWL) (>45 knots)
- Linear Acceleration Command/Velocity Hold (VEL) (Up to 45 knots)
True or False: The DAFCS can operate with the complete loss of one system.
True
Fill in the blank: The DAFCS provides basic aircraft stability and hold features when the _______ is placed to 1, 2, or BOTH.
AFCS System SEL switch
What is the role of the Flight Control Computers (FCCs) in DAFCS?
They perform redundant signal interface, real-time processing, control, and monitoring of cockpit controls, actuators, hydraulic valves, and sensors.
What happens in the Low Speed Regime of DAFCS?
It is active when weight is off wheels, and the aircraft has not accelerated past 45 KCAS.
What is the assessment method for students in this training program?
A criterion type examination requiring a GO on each scoreable unit, with 90 minutes to complete.
What are the safety requirements for the DAFCS training?
- No special safety considerations
- Emergency procedures for fire and severe weather
- Accountability formation by class leader
What does the term ‘Rate Dampening’ refer to in DAFCS?
Resistance to a rate motion not caused by the pilot.
What is the purpose of the risk assessment in DAFCS training?
To include environmental considerations and ensure students are briefed on hazards and control measures.
What are the environmental considerations mentioned in the DAFCS training?
- Comply with all environmental laws and regulations
- Prevent pollution at the source
- Conserve and preserve natural and cultural resources
What is the significance of the Weight on Wheels Switch in DAFCS?
It is also known as the Proximity Switch and is used to determine the aircraft’s status on the ground.
Fill in the blank: The DAFCS operates in three different control regimes that use _______ to separate the different regimes.
airspeeds
What is the definition of ‘Control Response Quickening’ in DAFCS?
It amplifies the pitch, roll, and yaw control inputs from the pilot to improve the aircraft response.
What is the function of the ‘Heading Hold’ feature in DAFCS?
It maintains the aircraft’s current heading, disabled when the power steering swivel switch is set to UNLOCK or STEER.
What is the maximum speed for Deceleration (DECEL) mode?
<65 knots to 1 knot
What speed does Position Hold (PSN) operate at?
<1 knot
What are the operational speeds for Inertial Altitude Hold (ALT-INRT)?
All Speeds
What speeds does Radar Altitude Hold (ALT-RAD) operate at?
All Speeds
What is the speed requirement for Descent mode?
<65 knots must be used with DECEL
What is the speed requirement for Roll Wings Level Mode?
> 45 knots
What is the maximum speed for Linear Acceleration Command/Velocity Hold (VEL)?
Up to 45 knots
List the main sections of the DAFCS pilot selectable modes.
- FLT DIR (Flight Director) section
- CYCLIC TRIM section
- SYSTEM SEL (Select) section
What components does DAFCS use to make inputs into the pitch, roll, yaw, and thrust axes?
- Extensible Link Actuator
- Differential Airspeed Hold Actuator (DASH)
- Thrust Cockpit Control Driver Actuator (CCDA)
- Pitch Cockpit Control Driver Actuator (CCDA)
- Longitudinal Cyclic Trim Actuators (LCTs)
- Control Position Transducers (CPTs)
- Air Data Computers (ADCs)
How many Air Data Computers (ADCs) does DAFCS utilize?
Two
What information do the Embedded GPS Initial Navigation Units (EGIs) supply?
- Pitch
- Roll
- Yaw
- Yaw rate
- Groundspeed
- Lateral Acceleration Data
What is Rate Damping in DAFCS?
Resistance to a rate motion not caused by the pilot in pitch, roll, and yaw axes
What does Control Response Quickening do in DAFCS?
Amplifies pitch, roll, and yaw control inputs from the pilot
How do the Flight Control Computers (FCCs) know if the pilot has made an input to the flight controls?
Through Control Position Transducers (CPTs)
What happens when the aircraft moves without CPT movement?
FCCs counter the motion caused by an outside force
What does the DAFCS provide in terms of altitude hold?
Altitude hold function available at all airspeeds
How does the Flight Director (FD) system operate?
As a cueing system with altitude hold options selected from the FD control layer
What are the operational modes for Longitudinal Cyclic Trim (LCT)?
- AUTO
- MANUAL
When is the Ground Regime active?
When the L and R GND CONT light are active
What happens to DECEL/PSN and VEL modes when either GND CONT light is active?
They will disengage
What is the maximum bank angle for low-speed turn coordination?
45°
What is the activation condition for Linear Acceleration Command/Velocity Hold (VEL)?
Can be armed at any speed but activates only below 35 knots forward groundspeed
What is the purpose of the Thrust Cockpit Control Driver Actuator (CCDA)?
Controls the longitudinal CCDA
What is the function of the DASH actuator?
Maintains airspeed or pitch attitude for a given stick position
What does the heading hold function do?
Rejects changes from an explicitly stored reference heading
What happens to heading hold when the power steering swivel switch is set to UNLOCK or STEER?
It is automatically disabled
What is limited-ACAH in the roll axis of low-speed flight?
A response-type that allows proportional change in bank angle until authority is exceeded
What does the CD REL switch do?
Adjusts the reference bank angle
What is the condition for the Low Speed Regime to become active?
When weight is off wheels and the aircraft has not accelerated past 45 KCAS
What is the primary purpose of the Extensible Link Assemblies (ELAs)?
Rate Damping and Stability control or Attitude Hold
What is the maximum speed for Deceleration/Position Hold (DECEL/PSN)?
Can be armed at any speed but activates only below 65 knots forward groundspeed
What happens to the longitudinal trim motor when the trim switch is pressed?
Increases/decreases airspeed/groundspeed
What is the function of the AFCS Trim Switch?
It allows the pilot to increase/decrease airspeed/groundspeed
Also known as the pitch beep trim switch.
Does the AFCS Trim switch work when the AFCS selector switch is OFF?
Yes, it will function even when the AFCS selector switch is in the OFF position.
What does the servo motor controlled by the AFCS provide?
PSN / DECEL / VEL features.
What holds the longitudinal detent when the trim motor is not driving?
A magnetic brake.
What should be done if erratic behavior of DECEL/PSN or VEL modes is observed?
Momentarily press the CD REL button.
What happens if GPS aiding is not available?
PSN will arm, DECEL will become active, driving the aircraft to a zero-velocity hover, but PSN will not engage.
When is the forward flight regime active?
When neither low speed nor ground regimes are active.
What does longitudinal static stability imply?
The cyclic is in the proper position for all airspeeds.
What does the DASH actuator do?
Rejects changes in airspeed and keeps the aircraft stable about an equilibrium airspeed.
What is the roll axis response type in the forward flight regime?
Rate command / attitude hold (RCAH).
What disengages bank angle hold?
Pressing the CD REL switch, displacing the AFCS TRIM switch, or laterally displacing the cyclic stick.
What happens when heading hold is disengaged?
It disengages if the swivel switch is set to STEER or UNLOCK, the CD REL switch is pressed, or the directional pedals are displaced.
What is directional static stability?
The tendency to point the nose of the aircraft into the relative wind.
What does the yaw ILCA do in terms of turn coordination?
Rejects changes in lateral acceleration and keeps the inclinometer ball centered.
What does the DAFCS Mode Select Switch do?
Selects operational modes for DAFCS: OFF / PSN / ALT / VEL.
What is the function of the Roll Wings Level Mode (LEVEL)?
It allows the pilot to activate a limited ACAH response type to roll the helicopter to near wings level.
What happens when the aircraft is in LEVEL mode and zero lateral stick force is applied?
It results in zero turn rate.
What is the primary function of DAFCS altitude hold?
To maintain altitude at all airspeeds.
What does the Thrust CCDA actuator do?
It holds the thrust control lever in place and is part of DAFCS.
What is the default function of altitude hold?
ALT-INRT, which nulls the vertical velocity signal from the EGI.
What does ALT-RAD mode utilize for altitude maintenance?
It uses inertial data and radar altimeter data.
What does the radar altimeter gauge indicate?
Radar altitude information valid to 8000 ft AGL.
What happens when both engine failure warnings are annunciated?
DAFCS stops controlling the collective.
What is the function of DAFCS Descent Mode?
It allows pilot selection of a descending, decelerating flight profile.
What is the maximum descent rate in DAFCS Descent Mode?
Approximately 600 fpm.
What does RATE COMMAND (RC) refer to in helicopter control?
Control inputs produce corresponding angular or vertical rates.
What is Attitude Command (AC) in DAFCS?
It stabilizes the helicopter’s attitude while allowing the pilot to control its position.
What is Linear Acceleration Command (LAC)?
An advanced version of TRC activated by selecting Velocity (VEL).
What feature does DAFCS provide to reduce pilot workload in degraded visual environments?
Attitude Command feature
This feature takes control of certain axes, relieving the pilot from extra attention to aircraft control.
What does LAC stand for in DAFCS 3.3?
Linear Acceleration Command
LAC is an advanced version of TRC activated by selecting Velocity (VEL) on the Thrust.
What is the purpose of Disturbance Responses in DAFCS?
Control modes DAFCS switches to when the pilot is not moving the controls
Disturbance Responses can occur in a single or multiple axes.
Define the ARMED state in DAFCS.
A feature is turned on and ready to operate when parameters are met
Displayed in white on the Vertical Situation Display (VSD) if shown.
What does the CAPTURED (Active) state indicate in DAFCS?
The feature is ARMED and within operational parameters
Displayed in green on the VSD if shown.
What does CYCLIC DETENT mean in the context of DAFCS?
Cyclic is not in motion with no pressure applied to control centering springs
Establishes an electronically centered position, used by Position Hold (PH) and other DAFCS features.
What are the two independent DAFCS systems in the CH-47F?
DAFCS #1 and DAFCS #2
Each requires AC and DC electrical power, flight hydraulic pressure, and two EGIs.
What does the FLT DIR switch do in DAFCS?
Couples the CAAS FD to DAFCS for automatic flight control operation
Illuminates a green CPLR annunciator on the MFD when pressed.
What is the function of the AUTO/MANUAL cyclic trim switch?
Controls the forward Longitudinal Cyclic Trim (LCT) actuator automatically in AUTO mode
In MANUAL mode, the pilot controls the actuators through the CYCLIC TRIM FWD and AFT switches.
What does the SYSTEM SEL switch do?
Selects operational DAFCS systems and prevents transitioning through a known bad system
Has two OFF positions and allows a single system to be isolated in case of failure.
What happens when both DAFCS systems are selected ON?
Each system operates at half-gain
Remaining system operates at three-quarter-gain if one system is off.
What is the purpose of the AFCS Trim Switch?
Makes changes in airspeed/groundspeed and roll attitude
In Core DAFCS Mode, it commands an increase or decrease in Airspeed/Groundspeed.
What does the Thrust Control Lever Hover Altitude Beep Switch do?
Allows the pilot to adjust altitude when Altitude Hold features are engaged
Each discrete beep changes hover altitude by one foot.
What is the DECEL mode in DAFCS?
Allows pilot selection of a descending, decelerating flight profile
It terminates in DAFCS PSN and ALT-RAD modes.
What altitude modes are available in the Thrust Control Lever?
- ALT-INRT
- ALT-RAD
- DESCENT
These modes are designed for precise hover altitude tasks.
What is the maximum glide path angle during DESCENT mode?
9 degrees
Becomes effective at 200 AGL and below from 65 KGS.
True or False: The DAFCS allows for the pilot to command a standard-rate turn.
True
The aircraft will continue the turn if the trim switch is held.
What does the DESCENT mode do when active?
Commands a descent terminating at 20 feet radar altitude simultaneously with PSN engagement
Adjusts glideslope based on height AGL and horizontal distance.
Fill in the blank: The DAFCS provides an acceleration command/ground speed hold mode for _______.
[pacing objects/vehicles or for formation flight in the low-speed flight regime]
What happens when the Beep UP is activated during descent?
The aircraft will continue the DESCENT with the new G/S and rate of descent.
What is the minimum G/S when beeping down on the Thrust UP/DN switch?
3 degrees
What is the purpose of DESCENT MODE?
To provide agility to take-off and land on a rolling, pitching and/or yawing ship deck without needing to turn off the AFCS.
What does the DAFCS SHIP mode disable?
- Heading Hold
- Roll Attitude Hold
- Altitude corrections when ground contact is detected.
How is SHIP mode activated?
Controlled by R1 on the VSDH or R6 on the HSDH.
What does it indicate when SHIP mode is displayed in white text?
SHIP mode is off.
What does it indicate when the SHIP label is highlighted with a green box?
SHIP mode is active.
What should be done before responding to any LCT failure emergency procedure?
Cycle the cyclic trim AUTO/MANUAL switch one time.
What is indicated if both ADCs fail?
The CHECK LCTS advisory will be inoperative.
What should be monitored if the system fails during cruise?
The LCT’s indications on the POWER TRAIN page.
What is the airspeed limit if one or both cyclic actuators fail in a fully retracted position?
Limit airspeed according to Vne for retracted longitudinal cyclic trim.
What should be done when both LCTs are partially or fully retracted?
Maintain below Vne and if failure occurs extended, maintain airspeed at or above 60 KCAS.
What should be done if one or both actuators fail in an extended position during landing?
Set the brakes and execute a shallow approach to a hover or to the ground.
What happens if both Flight Control Computers (FCC) lose power?
The LCT position indications will not be displayed on CAAS.
What does the AFCS1 OFF or AFCS2 OFF caution indicate?
The associated DAFCS has been turned OFF at the AFCS control panel.
What does the CHECK LCTS advisory indicate?
The actuator(s) position does not agree with the airspeed and altitude scheduling.
What is the RETRIM REQUEST advisory?
Active when either the roll and yaw ILCA is using more than 40% or 50% of its available authority for trim.
What should be accomplished before entering moderate or stronger turbulence?
- De-select FLT DIR Altitude Modes
- Alert crew
- Adjust airspeed
- Select MAN for LCTs
- Secure loose equipment
- Tighten safety belts and shoulder harnesses.
What is the recommended airspeed adjustment in severe turbulence?
Decrease airspeed to Vne minus 15 KCAS or to maximum range, whichever is slower.
What is the recommended airspeed adjustment in moderate turbulence?
Decrease airspeed to Vne minus 10 KCAS or to maximum range, whichever is slower.
What should be maintained during turbulence to keep airspeed relatively constant?
Constant THRUST CONT lever position and level flight attitude on the VSD.
What is the potential airspeed variation in turbulence?
Airspeed may vary as much as 40 KCAS.
