DAFCS

Question 1

DAFCS

Answer 1

Digital Advanced Flight Control System

Question 2

DAFCS Description

Answer 2

(1) With DAFCS the aircraft is both stable and agile, reducing pilot workload and fatigue which increases pilot situational awareness.

(2) The result is improved capability, mission effectiveness, operational readiness, operational tempo, and reduced maintenance costs.

(3) The Digital Advanced Flight Control System augments the mechanical Flight Control System and add features that tremendously increase capabilities.

Without the DAFCS the CH-47F is not stable and a challenge to fly.

Question 3

Dual Channel, Limited Authority System Provides

Answer 3

basic aircraft stability functions, and desirable handling characteristics.

(1) The pilot selectable higher augmentation modes add additional advanced features.
(2) The limited authority of the system ensures that the pilot can always over-ride the system if necessary.

Despite the complete loss of one channel, if the other channel is healthy, DAFCS functionality is largely retained.

(1) The pilot can select either channel or both channels of the DAFCS (1, 2, or both).

(2) The AFCS panel enables coupling of the Flight Director and either manual or automatic control of the Longitudinal Cyclic Trim (LCT) actuators.

Question 4

The DAFCS provides these features when on.

Answer 4

(1) Damping of angular rates of motion in the pitch, roll, and yaw axes.

(2) Control response augmentation in the pitch, roll, and yaw axes.

(3) Longitudinal static stability and airspeed stability above 40 knots CAS.

(4) Pitch attitude stabilization.

(5) Bank angle and heading hold.

(6) Directional static stability and automatic turn coordination above 40 KCAS and limited automatic turn coordination below 40 knots.

(7) Roll axis Attitude Command/Attitude Hold (ACAH) response type below 40 knots CAS.

(8) Selectable Velocity mode (VEL) below 40 knots groundspeed (with accompanying Forward Flight Velocity (aka Roll-to-Wings-Level) mode (Level) above 40 knots groundspeed).

(9) Selectable Position Hold (PSN) mode below 65 knots groundspeed (through accompanying DECEL mode).

(10)Selectable Altitude Hold using inertial (ALT-INRT) or radar (ALT-RAD) altitude reference. Selectable Decent mode (DESCENT) below 65 knots groundspeed (used in conjunction with DECEL mode).

(11)Selectable automatic longitudinal cyclic trim scheduling.

(12)Coupling with Avionics Management System (AMS) Flight Director.

Question 5

Rate Command (RC)

Answer 5

1) Most used control mode in a basic helicopter is rate-command/response type in all axes.

2) In other words, control inputs produce corresponding angular or vertical rates.

3) The stick/pedal deflection commands an equal roll/pitch/yaw response.

4) This is the control method used most often when the pilot has good visibility and can react immediately to the numerous visual cues in a Good Visual Environment (GVE).

5) This mode is needed because it gives the pilot the quickest response and most maneuverability.

Question 6

Attitude Command (AC)

Answer 6

1) With (AC), the DAFCS assist pilot by stabilizing the attitude of the helicopter in one or more axes, allowing the pilot to focus on control of the aircraft’s position.

2) This assistance is necessary due to the loss of the visual cues in a Degraded Visual Environment (DVE).

3) In an Attitude Command control mode, the pilot provides attitude commands to (DAFCS) though control movement.

4) The DAFCS system then attempts to achieve the commanded attitude while maintaining the stability in the axis it’s controlling.

5) This reduces the pilot workload since DAFCS takes control of certain axes relieving the pilot of the extra attention to aircraft control that resulted with the loss of visual cues.

6) This Attitude Command feature is needed and highly effective in a degraded visual environment (DVE).

Question 7

LINEAR ACCELERATION COMMAND (LAC)

Answer 7

1) With DAFCS 3.3 (LAC) replaces (TRC).

2) Consider (LAC) as an advanced version of (TRC) that is activated by selecting Velocity (VEL) on the Thrust.

3) In this mode, direction and groundspeed is proportional to cyclic stick displacement (like TRC) but, when controls are relaxed, the aircraft holds a constant groundspeed while locking the aircraft onto a ground track.

4) Both groundspeed and direction are adjustable by pilot stick or AFCS Trim Switch deflection.

Question 8

Disturbance Responses Description

Answer 8

(a) Disturbance Responses are the control modes DAFCS switches to when the pilot is not moving the controls.

(b) Disturbance Responses can occur in a single or multiple axes.

1) Example: You will see Longitudinal Attitude Stability, Lateral Attitude Stability and Roll Attitude Stability described in the operator’s manual.

(c) A HOLD is different from stability.

1) Example: Directional Stability will resist the disturbance that caused the aircraft to (yaw in this example) but will not return the aircraft to the previous state (heading).

2) Directional Hold, however, stored the previous state (heading in this example) and will return the aircraft to the stored heading that was present prior to the disturbance.

Question 9

ARMED State:

Answer 9

Means a feature is turned on and ready to operate when the parameters required by the feature to operate are met (usually airspeed or groundspeed or distance).

This state is displayed in white on the Vertical Situation Display (VSD) if displayed

Question 10

CAPTURED (Active) State

Answer 10

Means the feature is ARMED and is now within the parameters required for the feature to operate and the feature is now engaged or is activated.

This state is displayed in green on the VSD if displayed.

Question 11

CYCLIC DETENT

Answer 11

Means the cyclic is not in motion (in a steady state), with no pressure applied to control centering springs (remove spring pressure by bumping the CD-REL switch) and the centering device release switch (CD REL) is not being depressed.

1) At this time DAFCS establishes an electronically/pseudo centered position. This electronically centered position is the cyclic detent.

2) It is not necessarily for the cyclic to be in the mechanical centered position.
3) The cyclic detent is used by Position Hold (PH) Velocity (VEL) and other DAFCS features.

4) You will notice that DAFCS features usually have two airspeeds/groundspeeds associated with them.
a) Example: The Low speed Regime uses 45 knots accelerating and 35 knots decelerating.
b) If one speed was used, the feature would toggle on and off at that speed. Using the two different speeds prevents this toggling.

Question 12

Core Features Description

Answer 12

Core features are features that are operating as soon as the DAFCS selector switch is placed in the 1, 2 or both positions.

(a) These features activate automatically when within the parameters programed for them to operate.

(b) The core DAFCS is always active unless failures are present, or the system is selected off.

(c) Core Feature Explanation: DAFCS is ON with no pilot-selectable features engaged.

Question 13

Core Features

Answer 13

Rate Damping

Control Rate Augmentation

Longitudinal Static Stability and Airspeed Stability

Pitch Attitude Stabilization

Roll and Yaw Hold

Automatic Turn Coordination and Lateral-Directional Trim

Roll axis Attitude Command/Attitude Hold (ACAH)

Question 14

Damping of angular rates of motion in pitch roll, and yaw axes (also called rate damping).

Answer 14

(a) Damping is a method of decreasing oscillations by resisting rates of motion.

(b) DAFCS resists all aircraft rates of motion not caused by pilot input in the pitch roll, and yaw axes.

(c) DAFCS uses EGI angular rate feedback to move the ILCA Extensible Link Actuator (ELA) in the pitch, roll, and yaw axes for this feature.

(d) When airborne, this feature is always active.

Question 15

Control response augmentation in the pitch, roll and yaw axes (also called Control Response Quickening).

Answer 15

(a) (Inertia) More effort is required to start a movement than is required to continue a movement, so DAFCS augments pilot input to start the motion then ‘washes out’ the extra input once the motion has started.

(b) This feature also counters sluggishness that is sometimes caused by rate damping.

Question 16

Longitudinal static stability and airspeed stability above 40 KCAS.

Answer 16

(a) Below 40 KCAS, rotor-wash prevents accurate KCAS from the Air Data Computers (ADCs), so the DAFCS uses the DASH Actuator to hold the pitch attitude equal to the cyclic position.

(b) DAFCS always dampens pitch rates using the pitch extensible link but works with the DASH actuator below 40 KCAS to maintain pitch attitude hold below 40 knots.

(c) Above 40 knots, the ADCs now provide accurate KCAS and DAFCS now sees cyclic position as a defined KCAS.

(d) This is airspeed hold above 40 KCAS (like cruise control).

Question 17

Pitch attitude stabilization

Answer 17

(a) Pitch attitude stabilization is accomplished by the pitch ILCA ELA and DASH actuator using a combination of EGI pitch rate and pitch attitude.

(b) Pitch attitude stabilization is active when airborne regardless of airspeed, or whether the CD REL button is pressed.

(c) This feature simply holds the pitch attitude stable. It is not attempting to acquire or hold an airspeed as above.

Question 18

Roll and yaw axes holds

Answer 18

(a) Roll and Yaw axes are using attitude holds.

(b) Roll attitude hold is accomplished by the roll ILCA ELA using a combination of EGI roll rate and roll attitude.

(c) Yaw (Heading hold) is accomplished by the yaw ILCA ELA using EGI true heading. It is accurate to ± 3°.

(d) Holds are different from stabilization.

Question 19

Automatic Turn Coordination and Lateral-Directional Trim

Answer 19

(a) The automatic turn coordination and automatic trimming of the roll and yaw axes.

(b) If the CD REL button is released while the trim ball is floating within the inner goalposts, DAFCS will automatically center, the trim ball

(c) If the CD REL button is released while the ball is displaced far enough to just to touch the inner goalpost or more, then DAFCS will hold that position.
1) Example: Holding the aircraft out of trim for smoke and fume elimination.
2) It is not possible to trim the pedals for small sideslip angles producing less than 3/16 ball displacement.

(d) The DAFCS automatic turn coordination feature is active when accelerating above 40 kts airspeed.
1) If already in a turn when decelerating below 40 knots, then DAFCS provides low speed limited turn coordination down to 15 knots forward groundspeed.
2) The low-speed limited turn coordination will hold a maximum bank angle of 15 deg.
3) Once the aircraft has rolled out of the turn while below 40 knots, it will not go back into turn coordination until the airspeed is above 40 knots.

Question 20

Roll axis Attitude Command/Attitude Hold (ACAH) response type below 40 knots CAS.

Answer 20

(a) Within five seconds after decelerating below 35 knots airspeed, the DAFCS provides attitude-command attitude-hold (ACAH) in the roll axis using the roll ILCA and rate-command with heading-hold in the yaw axis using the yaw ILCA.

Question 21

Pilot-Selectable features (description)

Answer 21

(a) These features must be selected by the pilot when desired.

(b) The features activate when within the parameters programed for their operation.

(c) The pilot selectable modes add functionality to the core DAFCS but never remove it.

Question 22

Pilot-Selectable features

Answer 22

Forward Flight Velocity Mode (RWL)

Selectable Position Hold (PSN) and DECEL to Hover Modes

Selectable Altitude Hold

Descent Mode in conjunction with the DECEL mode

Selectable automatic longitudinal cyclic trim (LCT) scheduling

DAFCS Coupling to FD

Question 23

Velocity (VEL) mode

Answer 23

Velocity (VEL) mode and Position Hold (PSN) mode are disarmed at power-up and cannot be used at the same time.

One of the uses for Velocity mode is for pacing moving vehicles and matching their speed. This is a low-speed sub mode that activates below 35 KGS). The other mode is Forward Flight Velocity mode.

Question 24

Forward Flight Velocity Mode (RWL) )(also called roll-wings-level mode)

Answer 24

a) Forward Flight Velocity Mode is also called Roll Wings Level Mode (RWL) and activates above 45 KGS.

b) In the forward flight velocity mode, the helicopter will automatically roll itself to near wings level for zero turn rate with a limited ACAH roll axis response type.

c) Lateral stick in detent commands zero turn rate, which corresponds with wings-level only when the pedals are trimmed for ball-centered flight.

Right on TCL 4 way selector switch

Question 25

Selectable Position Hold (PSN) and DECEL to Hover Modes

Answer 25

1) The DAFCS position mode is another pilot-selectable horizontal mode that reconfigures the stick response and hold modes.

2) The deceleration to a hover is an integral part of position mode, so selecting PSN will capture your current radar altitude, decelerate the aircraft to a hover, (showing DECEL on the MFD) then, transfer to position hold mode at 1 KGS to hold your position (showing PSN on the MFD).

3) Position mode can be armed at any speed but will not activate if forward groundspeed is above 70 kts, if ground contact is detected, or if the CD REL button is pressed.

a) Automatic hover capture activates below 65 kts forward groundspeed if both ground contact switches indicate airborne.

Question 26

Selectable Altitude Hold

Answer 26

1) Selecting ALT label selects the DAFCS altitude hold modes.

2) Inertial altitude hold (using the EGIs as the MSL altitude source) is selected first to avoid following the terrain profile when moving.

3) The second click selects radar altitude hold (using the radar altimeter as the AGL altitude source) and the third click selects Descent Mode.

4) Additional clicks of the ALT button round robins though the modes.

5) Holding the 4-way selector forward for one second or more deselects altitude hold.

Question 27

Descent Mode in conjunction with the DECEL mode,

Answer 27

allows for pilot selection of a descending, decelerating flight profile that terminates in DAFCS PSN and ALT-RAD modes.

1) Descent can be armed at any speed using the ALT switch on the TCL.
2) When armed, the mode behaves identically to ALT-RAD.

3) DESCENT will become active upon activation of DAFCS DECEL mode and will descent the aircraft at a steady glideslope no steeper than 9 degrees and a rate of descent not more than 600 fpm, until terminating at a hover flight condition at a minimum height 20 feet AGL.

Question 28

Selectable automatic longitudinal cyclic trim (LCT) scheduling

Answer 28

1) When the Cyclic Trim Switch on the AFCS Control Panel is placed in the AUTO position, the longitudinal cyclic trim actuators are controlled automatically by the Flight Control Computers (FCCs).

2) The FCC1 controls the forward LCT actuator, and the FCC2 controls the aft LCT actuator.

3) When the Cyclic Trim Switch is placed in the manual position the pilots can independently control the actuators manually.

Question 29

DAFCS Coupling to FD

Answer 29

(a) The Flight Director is a cueing system that provides visual steering cues to the pilot to maintain the pilot selected airspeed, groundspeed, heading, and MSL/AGL altitudes etc.

(b) DAFCS provides a coupling feature which allow the Flight Director partition configured in MFDs 1 and 4 to take control of the DAFCS and fly the cues for the pilot, (Autopilot).

(c) Each Multi-Function Display (MFD) contains two computers.

Question 30

Sub-system description.

Must have the following to operate

Answer 30

Question 31

Flight Control Computers (FCCs)

Answer 31

The Flight Control Computers (FCCs) are located on the third shelf in the avionics compartment.

Each FCCsoperates as one of two independent DAFCS channels.

Question 32

CONTROL LAWS / REGIMES

Answer 32

There are three control laws/regimes programed into the DAFCS computers.

Ground Regime
Low Speed Regime
Flight Regime

Question 33

Sensors that supply information to the Flight Control Computer (FCCs):

Answer 33

Embedded Global Positioning / Inertial Navigation System (EGIs)

The Pitot Static system and Air Data Computers (ADCs)

The Radar Altimeter

The weight on Wheels Switches and the Power Steering Control Box.

The Control Position Transducers (CPTs)

Question 34

The Embedded Global Positioning / Inertial Navigation System (EGIs) supply the following information to the FCCs

Answer 34

The EGIs supply pitch, roll and yaw information.
Pitch, roll and yaw rate (speed) information.

Groundspeed

Lateral Acceleration Data for maintaining aircraft trim.

Altitude information for Inertial Altitude hold (MSL altitude).

Question 35

PITOT STATIC SYSTEM AND AIR DATA COMPUTERS

Answer 35

The Pitot Static system and Air Data Computers (ADCs) send calibrated Airspeed (CAS) and static pressure information to the FCCs.

There are two ADCs. The one in the left chin bubble sends data to the FCC1 and the ADC in the right chin bubble sends data to the FCC.2

Question 36

Radar Altimeter

Answer 36

The Radar Altimeter sends Above Ground level (AGL) altitude information to the FCCs for the radar altitude hold feature.

Question 37

PROXIMITY / WEIGHT-ON-WHEELS (WOW) SWITCHESPOWER STEERING CONTROL BOX

Answer 37

When both L and R GND CONT lights are active, the LCTs are commanded to the GND position.

When either the L or R GND CONT light transitions to active, the DECEL/PSN and VEL modes will disengage.

When either the L or R GND CONT light is
active, the DAFCS selectable modes can be armed by the pilot, but they cannot activate.

When either the L or R GND CONT light transitions to active, ALT-INRT and ALT-RAD modes will revert to the armed state.

While the ALT-INRT or ALT-RAD mode is armed on the ground, the thrust control lever may be beeped up or down to aid in takeoff and landing.

Question 38

POWER STEERING CONTROL BOX

Answer 38

Power Steering Control Box swivel switch sends a signal to the FCCs when placed in unlock or steer position.

The FCCs are programed to disengage the DAFCS Heading Hold feature at this time.

This prevents landing gear damage that would occur if DAFCS countered power steering input.

Question 39

Control Position Transducers (CPTs)

Answer 39

The Control Position Transducers (CPTs) in the pitch, roll and yaw axes send signals to the FCCs when the cyclic or pedals are moved.

The FCCs can determine the direction and rate of motion from the CPT signal.

The FCCs know that the pilot moved the controls and will not to counter the pilot’s input.

If the aircraft moves without CPT movement the FCCs know the movement was caused by an outside force (like wind, turbulence etc.), and immediately counters this type of motion.

Question 40

DAFCS controls the following components to make inputs into the pitch, roll, yaw, and thrust axes:

Answer 40

Extensible Link portion of the Integrated Lower Control Actuator

Differential Airspeed Hold Actuator (DASH)

Thrust Cockpit Control Driver Actuator

Pitch Cockpit Control Driver Actuator (CCDA)

Longitudinal Cyclic Trim Actuators (LCTs)

Question 41

Integrated Lower Control Actuators (ILCAs)

Answer 41

Flight Control Computers (FCCs) drive redundant electrohydraulic Extensible Link Assemblies mounted on Integrated Lower Control Actuators (ILCAs) in the pitch, roll, and yaw axes.

Question 42

Authority Cover

Answer 42

The thickness of the Authority Cover configures the ELAs on each ILCA for the axis in which it is installed (pitch, roll, and yaw).

Question 43

Spring Loaded Locking Cam

Answer 43

The Locking Cam houses a spring that locks the extensible link to the centered position when hydraulic pressure is removed.

Question 44

Extensible Link

Answer 44

Each Extensible link is connected to the summing link.

Question 45

Locking Cam

Answer 45

When hydraulic pressure is applied to the extensible link section of the ILCA, the locking cam is retracted from the extensible link

Question 46

Servo Valve Assembly

Answer 46

The Servo Valve Assembly responds to FCC commands and directs hydraulic pressure to extend or retract the extensible link.

Question 47

DIFFERENTIAL AIRSPEED HOLD (DASH) ACTUATOR

Answer 47

Provides pitch attitude Stability (below 40 knots), airspeed Stability (above 40 knots), and longitudinal static Stability.

The DASH actuator is a connecting rod with an actuator on each end which allows it to increase and decrease in length.

The two actuators extend or retract as commanded by the FCCs to maintain airspeed or pitch attitude for a given stick position (pitch).

The top actuator (1) is controlled by FCC1 and the bottom actuator (2) is controlled by FCC2.

Question 48

THRUST COCKPIT CONTROL DRIVER ACTUATOR (CCDA)

Answer 48

Thrust or Collective Cockpit Control Driver Actuator (CCDA) has a magnet brake to hold thrust Control Lever in place and an actuator inside. The actuator/motor is part of the DAFCS.

Only the FCC1 controls the Thrust CCDA to provide the various types of Altitude Hold features available in the CH-47F.

The Thrust CCDA is an electrically operated actuator/motor chosen to provide the full range of motion needed in the thrust axis.

When altitude hold is active the Thrust lever will move so the area beneath the thrust should always be clear.

The existing operator’s manuals use the terms thrust and collective interchangeably.

Question 49

LONGITUDINAL (PITCH) COCKPIT CONTROL DRIVER ACTUATOR (CCDA)

Answer 49

Only the FCC2 controls the longitudinal CCDA.

Inside the longitudinal CCDA, there are two motors.

The trim motor is controlled by the pilot using the pitch beep trim switch (also called the AFCS Trim Switch) to increase/decrease airspeed/groundspeed.

The servo motor is controlled by the AFCS to provide the Position Hold / DECEL / VEL features.

A magnetic brake holds the longitudinal detent when the trim motor is not driving, and the CD REL button is not pressed.

Question 50

LONGITUDINAL CYCLIC TRIM SYSTEM (LCT)

Question 51

DAFCS CONTROL PANEL

Answer 51

FLT DIR (Flight Director) section
The FLT DIR switch, when pressed,illuminates a green CPLR annunciatoron the MFD,
and the CAAS FDcouples to the DAFCS for automatic flight control operation.

When the Flight Director switch is pressed again or the FD couple release on the
cyclic is pressed, the FD will uncoupled.

The Voice Warning System (VWS) provides the pilot and copilot with computer-synthesized
voice messages of “Flight Director Uncoupled” when DAFCS and flight Director are uncoupled.

CYCLIC TRIM section
The AUTO/MANUAL cyclic trim switch is a two-position switch normally placed in AUTO.

(a) In AUTO, FCC1 controls the forward Longitudinal Cyclic Trim (LCT) actuator and FCC2 controls the aft LCT actuator automatically based on the airspeed and the position of the Weight-On-Wheels Switches.

(b) In MANUAL, the actuators are controlled by the pilot through with the CYCLIC TRIM FWD and AFT switches.

(c) The FWD and AFT EXT and RET switches are three-position switches that are spring-loaded to the center position.

(d) Used to extend (EXT) or retract (RET) the FWD and AFT LCT actuators.

(e) These switches are inoperable when the cyclic trim switch is in AUTO.

SYSTEM SEL (Select) section

The SYSTEM SEL switch is a five-position rotary switch labeled OFF, 1, BOTH, 2, OFF.

At OFF, both systems are inoperative except for the Longitudinal Cyclic Trim System (LCTs).

The switch allows a single system to be isolatedin the event of a failure.

With both systems on, each system operates at half-gain.

If one system off, the remaining system operates at three-quarter-gain to compensate.

The gain change between dual DAFCS and single DAFCS switch-over produces no significant change in control feel or response.

Thetwo OFF positions are to prevent transitioning through a known bad system to reachanOFF position.

The switch also turns off the associated Differential Airspeed Hold (DASH) actuator.

Question 52

CYCLIC CONTROL AND THRUST CONTROL LEVER SWITCHES

Answer 52

CYCLIC SWITCHES: There are three switches on the cyclic that have a DAFCS function.

(a)Advanced Flight Control System (AFCS) TRIM. Switch

(b)Centering Device Switch (CD REL)

(c)Flight Director Coupler Release (FD CPLR REL)

(d) The AFCS Trim Switch (a four-way rocker switch) is used to make changes in airspeed/groundspeed and roll attitude.

1) In Core DAFCS Mode, moving the switch forward or aft from the center off position commands an increase (forward) or decrease (aft) inAirspeed/Groundspeedby driving a trim motor inside the Pitch Cockpit Control Driver Actuator (CCDA).

a) Thecyclic will movein the direction of AFCS Trim switch movementandshouldbe allowed to move.

2) Moving the switch left or right tells the FCCs the command the roll extensible linksto bank the aircraft in the direction ofAFCS Trim switch movement.

a) The cyclic will notmove.

3) With Pilot-selectable features active, the DAFCS TRIM switch will have other functions described later in the lesson.

(e) The Centering Device Release Switch (CDR) is used to simultaneously release themagnetic brakes in the pitch, roll, and yaw axes.

1) In addition, when depressed, it momentarily disengages Bank Angle Hold, Heading Hold, and the flight director coupling while depressed.

2) When the CD REL switch is released, the flight director will return to the last selected heading or course if the flight director was engaged.

(f) The Flight Director Coupler Switch (FD CPLR REL) is a two-position pushbutton which allows the pilot on the flight controls to disengage the coupled mode of the Flight Director (FD).

Question 53

AFCS Mode Select Switch

Answer 53

The AFCS Mode Select Switch labels and function are: OFF / PSN / ALT / VEL for the DAFCS Thrust Grip.

a) Momentarily moving the 4-way selector switch to a desired mode will select that mode for operation.

2) Holding the 4-way selector switch on a desired mode for one second will deselect only that mode.

a) Momentarily selecting OFF will deselect (turn off) all native modes.

Question 54

THRUST CONTROL LEVER SWITCHES ALT

Answer 54

3) Native DAFCS – INRT/RAD

a) Toggling the AFCS Mode Select switch to ALT selects one of the altitude modes that are designed for tasks involving precise hover altitude particularly at low altitude near the ground or over water.

b) The first selection of the AFCS Mode Select switch to ALT selects the inertial source which displays as ALT-INRT.

1 Inertial altitude hold mode (using EGIs) may contain small bias errors which may cause slow drift rates of the inertial altitude hold.

2 This mode can be armed or active at any speed.

4) The second selection of ALT toggles the Altitude Hold mode to Radar Altitude Hold mode (ALT-RAD), where the actual altitude is measured by the radar altimeter.

a) If either Altitude Hold mode is active and 30 degrees pitch or 45 degrees roll are exceeded, the DAFCS Altitude Hold mode will change to armed.

b) The Altitude Hold mode will return to active when aircraft attitude is returned to within 25 degreed pitch and 40 degrees roll.

5) The Hover Altitude UP/DN switch is used to adjust hover altitude when radar or inertial altitude hold is selected.

a) Each discrete beep changes the hover altitude by one foot. If the switch is held for a sustained period of time, it commands a 200 ft/min rate of climb or descent.

b) While on the ground, beeping the switch up commands a 0.25 in/sec upward rate.

c) On the ground, the lower torque limit is set at 20% to approximately correspond to the thrust lever ground detent and zero thrust at 100% NR.

Question 55

THRUST CONTROL LEVER SWITCHES LEVEL

Answer 55

Native DAFCS – VEL/LEVEL

a) Momentarily toggling the AFCS Mode Select switch to VEL arms two of the Native DAFCCS modes.

b) Above 45 KGS, ROLL WINGS LEVEL or LEVEL mode is activated.

c) The LEVEL mode provides a selectable wing-leveler function during the turn coordination regime, in which the aircraft returns to wings-level at a rate of 5 deg/sec when lateral cyclic stick forces are relaxed.

d) LEVEL mode is active when it is armed, airspeed is above 45 KGS, roll attitude hold is active (core DAFCS mode that will disable if 90-degree roll is exceeded), no conflicting Flight Director coupled mode is engaged, and turn coordination is active during real-time operation.

e) The DAFCS allows the pilot to command a standard-rate turn by holding the cyclic trim switch in the roll direction when LEVEL mis active.

1 The aircraft will continue the turn if the trim switch is held. Once released, the aircraft will roll wings level.

Question 56

THRUST CONTROL LEVER SWITCHES VEL

Answer 56

f) Velocity Hold or VEL mode replaces TRC mode.

1 DAFCS provides an acceleration command/ground speed hold mode for pacing objects/vehicles or for formation flight in the low-speed flight regime.

2 In VEL mode, aircraft lateral and longitudinal KGS is proportional to cyclic stick displacement from detent.

3 VEL mode is active when it is armed, the aircraft is airborne, operating below 35 KGS, the CD REL button is not pressed, and the DASH is in normal rate mode.

Question 57

THRUST CONTROL LEVER SWITCHES DESCENT

Answer 57

Native DAFCS – DESCENT

a) DAFCS provides a selectable Descent Mode for performing degraded visual approaches over flat terrain in conjunction with DECEL.

b) Selecting ALT a third time toggles Altitude Hold mode to Radar Altitude Hold Descent mode (ALT+R DM).

Question 58

Flying in Moderate or Above Turbulence

Answer 58

In moderate to heavy turbulence, coupling barometric altitude will result in some fluctuating of airspeed hold. This occurs because short period altitude hold compensation is provided through the DASH actuator.

To prevent engine overtorque, do not enter forecast moderate or stronger turbulence with an inoperative Cockpit Control Drive Actuator or coupled to a vertical axis of the Flight Director.

LCTs — Select MAN, then adjust both actuators for the airspeed to be flown. This is accomplished to prevent the cyclic trim actuators from cycling.