Flight Controls Flashcards
Components
- 3 computers: 2 Flight Control Computers (FCCs) and Backup Flight Control Unit (BFCU) - - 16 actuators: 9 Hydraulic Actuators (HAs) and 7 Electric Backup Hydraulic Actuators (EBHAs) - 16 Remote Electronics Units (REUs)
- Horizontal Stab Control Unit (HSCU)
- Horizontal Stab Trim Actuator (HSTA)
- 2 Flight Control System (FCS) batteries: Electric Backup Hydraulic Actuator (EBHA) battery and Uninterruptable Power Supply (UPS) battery
- Flap Electronic Control Unit (FECU)
- GVIII uses fly-by-wire technology. How does this work?
Pilot inputs are read by a computer that in turn decides how to move control surfaces to best achieve what the pilot wants.
- How is trim accomplished?
Pitch and roll trim is accomplished by actuating switch mounted on sidestick; pedestal mounted PITCH TRIM switch is also used to control pitch.
- What’s the purpose of A/P DISC switch?
It disengages autopilot and stops runaway trim in all three axes.
- What’s the function of FLT CTRL RESET switch?
Used to reset flight control computers, sidesticks, and control surface actuators when directed by checklist.
- What effect does loss of one hydraulic system have on flight controls?
Loss of one spoiler pair.
- What are control laws?
Software in FCCs that translate electrical commands from cockpit control sensors and aircraft motion sensors (inertial/air data) into flight control surface commands.
- How many computers control the fly-by-wire flight control system?
Three (3) computers: two (2) flight control computers for normal operation and Backup Flight Control Unit in case both flight control computers fail.
- What’s the minimum number of FCC channels that can command all flight control surfaces on the aircraft.
One
- What’s the purpose of Backup Flight Control Unit (BFCU)?
It’s designed to provide what Gulfstream calls “get home capability” if both primary FCCs fail.
- What happens once the BFCU becomes active?
It communicates directly with EBHA remote electronics units (REUs) on separate backup data buses, and is active for duration of flight.
- Describe Electric Backup Hydraulic Actuator (EBHA).
It’s a special actuator with self-contained electric motor/pump and hydraulic reservoir.
- What type of sensor input is provided to FCCs?
Input from IRSs, AHRS, ADSs and radio altimeters.
- Describe AOA limiting feature.
In this mode, full stick input commands maximum nose angle-of-attack of 0.95.
- Which mode protects from surface flutter and separation that would occur greater than Vdive speed?
High speed protection
- What’s the auto-retract feature?
It retracts speed brakes at high power settings.
- What enhanced rudder feature occurs automatically following engine failure?
Application of rudder counters uncommanded thrust asymmetry.
- Name the four (4) flight control modes.
Normal, alternate, direct, and backup.
- When would flight control mode change from normal to alternate?
Loss of multiple air data or inertial sensors; may also revert to alternate mode if FCCs lose communication with HSCU.
- What happens if all four (4) FCC channels are invalid?
Flight control system reverts to direct mode.
- What happens if all four (4) FCC channels are unable to compute the control law?
Backup Flight Control Unit (BFCU) activates to provide “get home” capability.
- What term is used to describe the amplification, attenuation, boosting, or magnification that’s applied to forward signal to achieve desired aircraft response?
Gain
- Normal mode has four (4) primary operating sub modes. What are they?
On ground / takeoff stall protection, In flight, AOA limiting, and High speed protection.
- Describe how the flight control system operates in alternate mode.
Pitch, roll, and rudder pedal inputs are multiplied by set of fixed gains to command elevator, ailerons, roll spoilers, and rudder.
- How many sets of gains are associated with degraded flight control modes?
Two: one set of generally smaller numbers used when flap handle and gear handle are up (and aircraft is presumed to be traveling at higher speed – 340 kts), and a set of generally larger numbers that are used if flap handle or gear handle is down (and aircraft is presumed to be traveling slower – 250 kts).
- What functions with ailerons to improve roll response?
Mid and outboard spoiler panels extend to a maximum of 55°.
- Name the two types of flight control actuators.
Hydraulic Actuator (HA) and Electric Backup Hydraulic Actuator (EBHA).
- Describe HA operation.
It’s controlled electrically by its Remote Electronics Unit (REU) and uses hydraulic power to move control surface.
- What’s the function of REU?
It’s averages FCC1 and FCC2 commands and electrically controls a valve in hydraulic manifold to control actuator position to match FCC commands.
- What additional features do EBHAs have?
Able to operate in electric backup mode if normal source of hydraulic pressure is lost or operate in MCE direct control mode for REU failure.
- Describe EB operation.
Within EB hydraulic manifold, an electric motor turns a hydraulic pump that draws fluid from self-contained reservoir: it acts like third hydraulic system.
- What does the color of HA or EBHA status border indicate on flight control synoptic page?
Green for active/healthy, gray for inactive, and amber for failed.
- What pilot action is required for an aileron, spoiler, or elevator surface jam?
Both pilot and copilot side sticks remain available to control the unrestricted surfaces: fly normally and trim, and refer to AFM.
- Under what condition would pedestal mounted PITCH TRIM switch have to be used?
Backup mode: If this were to occur, pedestal mounted PITCH TRIM switch bypasses FCCs and controls horizontal stabilizer directly at a constant, minimum rate.
- What’s the difference between active, degraded active, and passive sidestick modes?
Active mode features electronic linking and electronic feel. In degraded active, sidesticks remain linked but lose active feel. In passive mode, there’s a loss of both electronic linking and feel.
- What pilot action is required in the unlikely event that rudder pedals become mechanically jammed?
Pilots would have to use other flight controls or differential power to control the aircraft.
- What component is responsible for moving the stabilizer surface?
Horizontal Stab Trim Actuator (HSTA), which is a dual electric motor.
- What kind of things can go wrong with the horizontal stabilizer?
FCC loss of communication with HSCU, failure of dual electric motor, mechanical jam of jack screw, or failure of both channels of Horizontal Stab Control Unit (HSCU).
- What is elevator off-load feature?
Once elevator deflection exceeds preset value for predetermined amount of time, horizontal stabilizer and elevators move simultaneously: horizontal stab moves to new trim position as elevators move to “faired” position (0 degrees relative to horizontal stab surface). It’s controlled or commanded from FCCs to reduce elevator deflection.
- Describe return-to-zero function.
FCC commands stabilizer, roll trim and yaw trim to return-to-zero after landing.
- Describe how the flaps operate.
Manually operated, electrically controlled, hydraulically powered, and mechanically actuated.
- What happens if there’s any sort of malfunction (e.g., flap jam, asymmetry, runaway, etc.) during flap operation?
Flap motion is interrupted.
- What happens if you attempt to extend the flaps at high rate of speed?
A load limiter device prevents the flaps from extending.
- When do the spoilers function?
Six spoiler panels (three on each wing) operate as speed brakes/air brakes and ground spoilers; four operate as flight spoilers (i.e., two outboard).
- What is maximum spoiler deflection?
55°
- What’s the maximum deflection with full speed brake extension?
30° in-flight or 55° on ground with flap handle not up.
- What indications would you get during speed brake extension?
When moved left and aft out of forward detent, a white Speed Brakes Extended message displays.
- How would the indications change during level off?
As power is increased during level off, white Speed Brakes Extended message changes to amber and you get the associated two bong caution chime.
- What happens if speed brakes are extended and pilot advances the throttles to high power setting?
Speed brakes automatically retract although speed brake handle remains in extended position, and amber Speed Brakes Auto Retract message displays.
- What function do ground spoilers perform on touchdown or during rejected takeoff?
All spoiler panels deploy to 55° and ailerons deploy trailing edge upwards to spoil lift and increase braking effectiveness.
- What are the requirements for ground spoiler deployment?
Throttles at idle and one of the following: both main gear WOW, left WOW and right wheel spin, right WOW and left wheel spin, both main gear wheel spin and radar altitude < 10 ft.
