Flight Control Systems Quiz

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Questions and Answers

Which hydraulic systems provide primary power to the flight controls under normal operating conditions?

  • Hydraulic System A only
  • Hydraulic Systems A and B (correct)
  • Hydraulic System B only
  • Standby Hydraulic System

In the event of a complete loss of both Hydraulic Systems A and B, how are the ailerons and elevator controlled?

  • Mechanically through cables, all surfaces
  • Mechanically through cables for ailerons and elevator, standby hydraulic for rudder (correct)
  • Electrically
  • Hydraulically via the standby system

Following a failure of Hydraulic System B, how are the leading edge flaps/slats and trailing edge flaps actuated?

  • LE Flaps/Slats: Electrically; TE Flaps: Hydraulically from System A
  • LE Flaps/Slats: Hydraulically from System A, TE Flaps: Electrically
  • LE Flaps/Slats: Electrically, TE Flaps: Standby Hydraulic System
  • LE Flaps/Slats: Standby Hydraulic System, TE Flaps: Electrically (correct)

If the aileron control system is jammed or restricted, how is roll control maintained?

<p>Force applied to the First Officer's control wheel operates the flight spoilers for roll control (A)</p> Signup and view all the answers

If the Spoiler System is jammed or restricted, how is roll control maintained?

<p>Roll control is maintained through the operation of the ailerons by the Captain's control wheel (B)</p> Signup and view all the answers

Why is aileron trim prohibited when the autopilot is engaged?

<p>Aileron trim when the autopilot is engaged can cause an out of trim condition and abrupt roll when disengaged (C)</p> Signup and view all the answers

Approximately how many degrees of control wheel displacement is needed to initiate flight spoiler deflection?

<p>10 degrees (D)</p> Signup and view all the answers

What does illumination of the FEEL DIFF PRESS light indicate?

<p>Excessive differential pressure in the elevator feel computer (A)</p> Signup and view all the answers

If either the Captain’s or the First Officer’s control column is jammed, how can elevator control be regained?

<p>By applying force against the jam to breakout the column, and use the freed column for control (D)</p> Signup and view all the answers

When is the Elevator Jam Landing Assist system designed to be used?

<p>When there is a jam in the aft elevator control mechanism (B)</p> Signup and view all the answers

What is the primary function of the Elevator Jam Landing Assist system during approach and landing?

<p>To provide small flight path adjustments using flight spoilers. (B)</p> Signup and view all the answers

Under which condition would the autopilot NOT provide stabilizer trim?

<p>When a STAB TRIM Cutout switch is set to CUTOUT (C)</p> Signup and view all the answers

If both STAB TRIM Cutout switches are set to 'CUTOUT', how would a pilot adjust the stabilizer trim?

<p>By manually rotating the stabilizer trim wheels. (C)</p> Signup and view all the answers

What is the function of the Control Column Actuated Stabilizer Trim Cutout switches?

<p>To prevent trim inputs if the pilot moves the column opposite of the trim command. (B)</p> Signup and view all the answers

What is the primary purpose of the STAB TRIM switch on the aft electronics panel when set to 'OVRD'?

<p>To allow operation of the Main Electric Stabilizer Trim regardless of control column position. (D)</p> Signup and view all the answers

What indicates that the stabilizer trim is out of the acceptable range during takeoff?

<p>An intermittent horn and the illumination of the TAKEOFF CONFIG light. (D)</p> Signup and view all the answers

Which statement accurately describes the Speed Trim System's (STS) functionality?

<p>It improves flight characteristics during low weight, aft center of gravity, and high thrust when the autopilot is not engaged. (D)</p> Signup and view all the answers

What is a primary difference in operation between the Speed Trim function and the MCAS function?

<p>MCAS is designed to command the stabilizer nose down at elevated AOAs, while the Speed Trim function maintains a trimmed speed in other conditions. (C)</p> Signup and view all the answers

If the Main Electric Stabilizer Trim is used to inhibit Speed Trim or MCAS, how long will these systems be inhibited?

<p>The system will be inhibited for 5 seconds. (D)</p> Signup and view all the answers

Why does the MCAS function contain logic that limits its nose down stabilizer trim command?

<p>To ensure there is enough elevator authority available for pitch control. (A)</p> Signup and view all the answers

What is the immediate consequence when the Maneuvering Characteristics Augmentation System (MCAS) reaches its command limit for nose-down stabilizer trim?

<p>The SPEED TRIM FAIL light illuminates, and the Speed Trim System is inhibited for the remainder of the flight. (B)</p> Signup and view all the answers

Under what condition will the SPEED TRIM FAIL light remain illuminated after a Flight Control Master Caution is reset?

<p>A failure in either the Speed Trim function or the MCAS function within the Speed Trim System. (D)</p> Signup and view all the answers

If a FLT CONTROL Master Caution illuminates on RECALL, accompanied by the SPEED TRIM FAIL light, which then extinguishes after the Master Caution system is reset, should the crew perform the QRH Non-Normal Checklist?

<p>No, this indicates a single FCC channel failure which does not require a checklist. (D)</p> Signup and view all the answers

How can a pilot counteract the nose-up or nose-down stabilizer trim commands from the Speed Trim System (STS) or MCAS?

<p>By using the Main Electric Stabilizer Trim to oppose STS/MCAS commands, except nose-down stabilizer trim from MCAS. (A)</p> Signup and view all the answers

What is the primary function of the Elevator Feel Shift (EFS) module during a stall?

<p>To increase pressure to the elevator's hydraulic actuator, which doubles control column forces. (C)</p> Signup and view all the answers

What specific protection do the Flight Control Computers (FCCs) provide regarding erroneous stabilizer trim commands?

<p>They compare each other's commands and stop all trim for the remainder of flight for that FCC if they detect an error. (C)</p> Signup and view all the answers

What function does the Autopilot Elevator Monitor primarily serve?

<p>To protect against erroneous elevator commands that could lead to incorrect autopilot stabilizer trim commands. (D)</p> Signup and view all the answers

If one function of the Speed Trim System fails, what happens to the other function?

<p>It is inhibited for the remainder of the flight. (B)</p> Signup and view all the answers

What does the illumination of the SPEED TRIM FAIL light specifically indicate, with regard to the flight control system?

<p>That there has been a failure in either the Speed Trim or MCAS functionality. (B)</p> Signup and view all the answers

When are the control column cutout switches effective at inhibiting stabilizer trim commands?

<p>They inhibit electric trim commands but do not interrupt MCAS nose down commands. (B)</p> Signup and view all the answers

Flashcards

Primary Flight Control Power

Hydraulic System A and B power the primary flight controls.

Manual Reversion for Ailerons

Ailerons are controlled mechanically through cables when both hydraulic systems fail.

LE Flaps and Slats Operation

If Hydraulic System B fails, LE Flaps and Slats are operated by the Standby Hydraulic System.

Roll Control with Aileron Jam

Roll is controlled by spoilers when the aileron system is jammed.

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Roll Control with Spoiler Jam

When the spoiler system is jammed, the ailerons provide roll control.

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Aileron Trim with Autopilot

Aileron trim is prohibited with autopilot engaged to prevent abrupt roll when disengaging.

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Flight Spoiler Deflection

More than 10° of control wheel displacement initiates flight spoiler deflection.

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FEEL DIFF PRESS Light

Illuminated light indicates excessive differential pressure in the Elevator Feel Computer.

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Elevator Control Jam Recovery

Force against a jammed control column can break it free, allowing elevator control.

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Elevator Jam Landing Assist

Used when there is a jam in the aft elevator control mechanism to assist landing.

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MCAS Command Limit

When MCAS reaches its command limit, the SPEED TRIM FAIL light illuminates and Speed Trim System is inhibited.

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SPEED TRIM FAIL Light

Illuminates due to failure in the Speed Trim System. Remains on until reset.

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FLT CONT Master Caution Reset

Resetting the caution does not clear the SPEED TRIM FAIL light if there's a failure.

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Single FCC Channel Failure

Only the FLT CONTROL Master Caution is on RECALL for a single FCC channel failure.

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Override Speed Trim System

Pilot can override the Speed Trim commands using the Main Electric Stabilizer Trim.

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Elevator Feel Shift (EFS)

Increases hydraulic pressure to elevator feel during stall, doubling control column forces.

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FCC Stall Protection

FCCs monitor and inhibit stabilizer trim commands to prevent runaway stabilizers.

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Autopilot Elevator Monitor

Protects against erroneous elevator commands that could lead to improper autopilot stabilizer trim.

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Inhibit Commands

When a function fails (like MCAS), the other function is inhibited prevents further commands.

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Control Column Cutout Switches

Used to inhibit electric trim commands, except for MCAS nose down commands.

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Elevator Jam Landing Assist Activation

Activated by turning the Elevator Jam Landing Assist switch ON, flap position 1+, and disengaging autopilot.

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Stabilizer Trim with Autopilot

When autopilot engaged, trim is achieved through the autopilot stabilizer trim circuit.

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Manual Stabilizer Trim

Accomplished through cables; the pilot uses trim wheels to manually position the stabilizer.

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STAB TRIM Cutout Switches

Disconnects autopilot trim, main electric trim, and speed trim when set to CUTOUT.

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Speed Trim System (STS)

Provides speed and pitch stability augmentation while autopilot is not engaged.

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Maneuvering Characteristics Augmentation System (MCAS)

Pitch stability function that activates at high angles of attack, commanding the stabilizer nose down.

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MCAS Activation Conditions

Activates with AOA above threshold, autopilot off, flaps up, up to Mach 0.84, and 10 seconds after takeoff.

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Speed Trim Function Operation

Improves flight characteristics with low weight and high thrust when autopilot is not engaged.

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Inhibiting MCAS

MCAS stabilizer operation can be inhibited by using pilot Main Electric Stabilizer Trim switches.

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Takeoff Warning Horn

Sounds if stabilizer trim is out of the green band during takeoff.

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Study Notes

Flight Control Systems

  • Primary Flight Controls: Powered by Hydraulic Systems A and B.
  • Manual Reversion: With both hydraulic systems lost, ailerons and elevators revert to mechanical control via cables. The rudder uses a standby hydraulic system.
  • Flaps and Slats: With Hydraulic System B lost, Leading Edge (LE) flaps and slats operate via the standby hydraulic system. Trailing Edge (TE) flaps are electrically operated.

Aileron and Spoiler System Failures

  • Jammed Ailerons: Roll control is provided by applying force to the First Officer's control wheel, activating the spoilers.
  • Jammed Spoilers: Roll control is provided by applying force to the Captain's control wheel, activating the ailerons.

Aileron Trim with Autopilot

  • Autopilot Engagement: Aileron trim is prohibited when the autopilot is engaged.
  • Autopilot Override: Autopilot overpowers trim adjustments, maintaining the control wheel position needed for heading/track control. Disengaging autopilot can result in abrupt rolling.

Spoiler Deflection

  • Control Wheel Displacement: More than 10° control wheel displacement triggers flight spoiler deflection.

Elevator Feel Pressure

  • FEEL DIFF PRESS light: Indicates excessive differential pressure in the Elevator Feel Computer due to hydraulic system loss (A or B) or Elevator Feel Pitot System failure.

Control Column Jam

  • Column Jamming: Force against a jammed control column will often break it free. The free column is used for elevator control.
  • Elevator Jam Landing Assist: Used when the elevator mechanism is jammed, using flight spoilers to adjust the flight path during the approach and landing phases.
  • Activation: Elevator Jam Landing Assist switch ON, flaps at 1 or greater, and autopilot disengaged.

Stabilizer Trim

  • Autopilot Trim: Stabilizer trim is managed by the autopilot when engaged.
  • Manual Trim: Manual trim uses cables, moving the stabilizer through stabilizer trim wheels. Electric motors are used when flying manually.
  • High/Low Speed Modes: Autopilot or electronic trim is active when flaps are extended (high speed) or retracted (low speed).

Trim Cutout Switches

  • STAB TRIM Cutout Switches (PRI and B/U): Disconnecting Autopilot Trim, Main Electric Stabilizer Trim, and Speed Trim System (STS/MCAS) if set to CUTOUT.
  • Manual Trim with Cutout: Stabilizer trim is performed manually by using the stabilizer trim wheel..
  • Control Column Actuated Stabilizer Trim Cutout Switches: Interrupting Main Electric Stabilizer Trim, Autopilot Trim, and Speed Trim commands when control column opposes trim direction. MCAS (nose down) is unaffected by aft column movement.
  • FCC Software Column Cutout Function (Redundancy): Adds a redundant layer to protect against latent failures in the Control Column Actuated Stabilizer Trim Cutout switches.
  • Aft Electronics Panel STAB TRIM Switch (Override): Allows for Main Electric Stabilizer Trim operation independent of control column position.

Stabilizer Trim Warnings

  • Takeoff Warning: Horn sounds, and TAKEOFF CONFIG light illuminates if stabilizer trim is out of the green band during takeoff.

Speed Trim System (STS)

  • Purpose: Speed and pitch stability augmentation. The Speed Trim function assists speed stability, while the MCAS function assists pitch stability.
  • Autopilot Compatibility: STS does not operate when the autopilot is engaged.
  • Operation Conditions: Up to Mach 0.68, 10 seconds after takeoff, 5 seconds after releasing trim switches, and sensor-detected trim needs.
  • Trim Rate: High rate with flaps extended, low rate with flaps retracted.

Maneuvering Characteristics Augmentation System (MCAS)

  • Purpose: Pitch stability augmentation at elevated angles of attack (AOAs). Increases control column forces by commanding stabilizer nose-down at high AOAs.
  • Operation Conditions: AOA above threshold, autopilot disengaged, flaps up, up to Mach 0.84, and 10 seconds after takeoff.
  • **Autopilot Compatibility:**MCAS does not operate when the autopilot is engaged.
  • Trim Rate: High rate.
  • Data Source: Flight Control Computer (FCC) receives data from both AOA vanes.
  • Override: MCAS can be inhibited/reversed by using the pilot's Main Electric Stabilizer Trim switches.
  • Inhibit Delay: 5 seconds after inhibiting with main electric trim.

Speed Trim Failure

  • SPEED TRIM FAIL Light: Lights up and remains illuminated after a FLT CONT Master Caution reset due to Speed Trim System (Speed Trim function or MCAS function) failure. A single failure will inhibit the other function.

Elevator Feel Shift (EFS)

  • Purpose: Increases hydraulic system A pressure to the Elevator Feel and Centering Unit in a stall; this approximately doubles control column forces.
  • Stall Protection: Flight Control Computers(FCCs) protect against possible runaway stabilizer trim.

Autopilot Elevator Monitor

  • Role: Protects against erroneous elevator commands that may result in erroneous autopilot stabilizer trim commands.

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