Flight Controls

Question 1

(88, 90) Purpose of STABILIZER TRIM brake switch:

Answer 1

• Red guarded switch on aft pedestal used to stop a runaway stabilizer caused by the primary trim motor.
• Moving switch⇒ STOP removes pwr from stab trim brake.
• Springs then force brake to clamp on primary trim motor.

Question 2

(88, 90) Function of STICK PUSHER PUSH TO INHIBIT Switchlight (white):

• How can pusher be overridden?
• When is pusher been inhibited?

Answer 2

• Illuminates whenever post stall recovery system (stick pusher) is activated, and during stall warning test.
• When pressed - Disengages post stall recovery system (stick pusher) and extinguishes switchlights.
• Pusher may be manually overridden by pulling aft on control column. However, if stall persists and aft pressure is released, stick pusher will again force the column forward.

NOTE: Post stall recovery system is inhibited anytime red windshear warning light is illuminated.

Question 3

(88, 90) Positions and purpose of rudder control lever

(RUD HYD CONT):

Answer 3

PWR / MAN
• PWR – Allows hyd pressure to power rudder and lock rudder control tab in a faired position.
• MAN – Shuts off hydraulics to rudder, unlocking rudder control tab to respond to rudder pedal movement.

Question 4

(88, 90) SLATS advisory lights:

Answer 4

• T/O – FLAP/SLAT handle, flaps and slats are in takeoff range (for flaps, 0-24°)
• DISAG – Left and right wing slat positions do not agree with handle position and/or with each other.
• AUTO- Slats have automatically extended from mid to extend position in response to stall warning system (autoslat).
• LAND – FLAP/SLAT handle, flaps and slats are in the landing range.

Question 5

(88, 90) Differences in trim rates for primary and alternate pitch trim systems:

Answer 5

• Primary trim ctrl moves stab 1/3° per sec

MD-88
• Alternate trim control moves the stabilizer 1/10° / sec. Alternate trim motor is also used by the autopilot.

MD-90
• Operation of alternate trim switches moves stabilizer 1/5° /sec. Alternate trim motor is also used by autopilot for longitudinal trim and Mach Trim compensation.

Question 6

(88) How are primary lateral flight controls are POSITIONED and POWERED?

Answer 6

• Lateral Control (ailerons) – Control wheels are cable connected to respective aileron control tabs, and are linked together by a torque tube arrangement that causes both control wheels to move together.

Question 7

How are primary directional flight controls are POSITIONED and POWERED?

Answer 7

• Directional Control (Rudder) - Rudder is powered by the right hydraulic system, but may be operated aerodynamically without hydraulic power

Question 8

(88) How are primary pitch flight controls are POSITIONED and POWERED on the MD-88?

Answer 8

MD-88
• Pitch control (elevators) - 2 elevators attached to rear of the horizontal stab, are displaced by aerodynamic control tabs (one on each elevator). Each control tab is driven by an independent two way cable system from corresponding control column in the cockpit.
• Hydraulic power augmenter system provides elevator control for additional nose down capability in extreme, high AOA flight conditions. (This power augmenter system hydraulically displaces the elevators full down.)
• Blue ELEVATOR POWER ON light on OAP illuminates when hyd. pressure is being applied to the elevator.

Question 9

(90) How are primary pitch flight controls are POSITIONED and POWERED on the MD-90?

Answer 9

• Longitudinal control provided by 2 elevators attached to horizontal stab. Elevator control, for all normal flying, is hydraulically powered by both hydraulic systems, w/ manual operation (non-powered) capability. Elevator hydraulic control is accomplished through the ACU. The ACU monitors hydraulic pressure to the actuators, controls 2 motor-operated shutoff valves, and generates ELEV CONTROLS MANUAL message on OAP during manual elevator operation.
• HYD CONT ELEV switch on overhead panel, deactivates powered elevator control and establishes manual elevator control. ELEV CONTROLS MANUAL is displayed on OAP to confirm reversion to manual control.
• In the event of a total loss of hydraulic pressure or malfunction of powered elevator system, elevator control automatically reverts to manual operation. During manual operation of elevators, manual reversion mechanism operates single control tab (faired for powered operation, but unlocked for manual control) on each elevator
• The left and right control columns are connected by a split torque tube. Should any part of the system become jammed between the control columns and control tabs, a pre-locked detent-type mechanism will allow pilots to override jam by using approx 150# of force.
• Blue ELEVATOR AT LIMIT light on OAP indicates pylon flaps and elevators have reached full down position; also indicates full up position of the elevator.

Question 10

(88, 90) How do spoilers assist ailerons in roll control?

Answer 10

• Inboard and outboard spoiler on each wing supplement the ailerons for lateral control.
• When control wheel is rotated (ailerons deflected) past an approx 5˚ wheel angle, flight spoilers start to extend on downward moving wing.
• Further control wheel movement extends flight spoilers in proportion to lateral control demands.

Question 11

(88, 90) Conditions for automatic ground spoiler deployment on landing:

Answer 11

When system is armed and throttles are moved to idle: Spoilers automatically extend
• After main wheel spin-up -or-
• After nose gear actuates groundshift.

After landing, all spoilers (flight and ground) extend to a max of 60° to serve as ground spoilers.

Question 12

(88, 90) Conditions for automatic ground spoiler deployment during a rejected takeoff:

Answer 12

• Spoilers armed prior to takeoff
• Rejected takeoff is initiated
- Nosewheel on ground and throttles at idle
• When reverse thrust selected
- Flight and ground spoilers will extend to 60°

Question 13

(88, 90) Seven takeoff warnings:

Answer 13

With airplane on the ground and throttles advanced toward T/O any of following conditions will cause aural and vocal system to activate:
• “FLAP” - FLAP/SLAT handle not in agreement with value set in FLAP window of the TAKEOFF CONDTN computer.
• “SLAT” - Slats are not extended.
• “STABILIZER” - Horizontal stabilizer not set within green band area of the LONG TRIM indicator.
• “BRAKES” - Parking Brake set.
• “AUTOBRAKE” - Spoiler/speed brake lever armed when autobrakes are not selected for takeoff.
• “SPOILERS”- Spoiler/speedbrake lever not in retract detent
• “AUTO SPOILER” - Autobrakes selected for takeoff and spoiler/speed brake lever not armed.

Question 14

(88, 90) When will auto spoilers retract after deployment on landing (rejected landing?)

Answer 14

If throttles are advanced for a go-around,

• Spoilers retract and SPD BRK lever will be disarmed

Question 15

(88, 90) Progression of the stall protection system:

Answer 15

Approach to stall is detected by either of 2 independent stall warnings systems.
• AUTO SLATS – If Flap/Slat handle is set in 0-13° flap range, airspeed ≤ 240KIAS, and either of the 2 stall warning computers detects a stall, slats extend automatically from mid to extended position.
• STICK SHAKER – As aircraft continues into a deeper pre-stall with increasing AOA, stick shakers are activated.
• STALL WARNING LIGHTS AND AUDIO - As aircraft continues into stall, either stall warning computer will activate stall warning horn, vocal “STALL”, and illuminate red glareshield STALL lights.
• STICK PUSHER SYSTEM – Whenever a stall condition is detected by both stall warning systems and slats are not retracted, control columns are abruptly moved forward, STICK PUSHER PUSH TO INHIBIT glareshield lights illuminate, and auto pilot, if engaged, will disconnect.

Question 16

(88, 90) Where are the four sets of longitudinal trim switches located, and which trim motor they operate?

Answer 16

• Control Wheel Trim Switches (2) – activate primary trim.
• One set of LONG TRIM Handles on the Pedestal – activate primary trim. Trim handles override electric control wheel switches as well as the ALT LONG TRIM levers.
• One set of ALT LONG TRIM Levers on pedestal - activate alternate trim motor

Question 17

(88, 90) Describe the operation of the spoilers/speed brakes on the ground and in flight:

Answer 17

• During flight, manually moving the pedestal-mounted spoiler/speed brake lever aft extends the four flight spoilers to serve as speed brakes.
• These spoilers may be symmetrically extended to 35° max
• Use of aileron control during speed brake operation results in asymmetrical extension of spoilers to aid in lateral control.
• In flt, speed brakes may be extended w/ slats extended.
• On the ground, all spoilers (flight and ground) are extended to a max of 60° to serve as ground spoilers during landing or RTO (either automatically or manually).

Question 18

(88, 90) Function of MD-88 Rudder Throw Limiter

Answer 18

• Rudder throw limiter is installed to protect empennage from overload in case of inadvertent application of excessive rudder control.
• During acceleration, throw limiter is scheduled to vary between the max. throw of 22° (unrestricted) up to 2½° (fully restricted) at ~300 kts.
• Blue RUDDER TRAVEL UNRESTRICTED light must be extinguished above 200 knots.
• On deceleration, throw increases until reaching 22° at a min. speed of 165 KIAS.
• Rudder throw limiter is monitored by blue RUDDER TRAVEL UNRESTRICTED light on OAP.

Question 19

(88, 90) Function of MD-90 Rudder Throw Limiter

Answer 19

• Primary & backup rudder throw limiter systems protect empennage from inadvertent overload. Failures in either primary or backup limiting systems generate msgs on OAP.
• Rudder hook monitor (RHM) verifies that primary limiter is in proper position. No blue RUDDER TRAVEL UNRESTRICTED LIGHT is installed.
• Backup rudder throw limiter is hydraulically powered, and protects empennage from overload if excessive rudder control is attained due to a failure in primary system.
• ACU monitors rudder stop limiter and commands hyd. actuators based on airspeed. Hyd power is supplied to each actuator by its associated hyd system. Backup limiter continues to operate with single system hyd failure.
• Springs retract backup limiter if both hyd systems fail.

Question 20

(88, 90) Switch positions and operation of Yaw Damper :

Answer 20

OFF / ON / OVRD

• OFF - Yaw damper operation disabled if autopilot is disengaged. With autopilot engaged, yaw damper operation is automatically provided.
• ON - Yaw damper operation is provided with autopilot engaged or disengaged.
• OVRD - Inhibits yaw damper operation with autopilot engaged or disengaged.

Question 21

(90) Purpose and function of MD-90 Pylon Flap System:

Answer 21

• Pylon flap system, installed on trailing edge of each pylon, provides increased aircraft nose-down pitching moment if deep stall is encountered.
• Moving either control column to the forward stop activates system. Pylon flap surfaces move from neutral position to fully deployed. Moving control column off forward stop causes pylon flap surfaces to return to neutral position.
• Blue ELEVATOR AT LIMIT light on OAP indicates pylon flaps and elevators have reached full down position. Also illuminates to indicate full up position of the elevator.

Question 22

(88) Purpose and operation of MD-88 Mach trim compensator:

Answer 22

MD-88
• Operating on a Mach speed schedule, Mach trim compensator pulls FO’s control column aft as Mach number increases to compensate for normal pitch down (tuck) encountered at high Mach operation.
• With switch in NORM, mach trim compensator positions FO’s control column aft at speeds > .80M.
• Function is controlled by MACH TRIM COMP switch located on overhead panel.
• Switch ⇒ OVRD deactivates system

Question 23

(88, 90) Purpose and operation of the MD-90 Mach trim compensator:

Answer 23

MD-90
• Mach trim compensation is accomplished w/ horizontal stab trim.
• Function is controlled by the MACH TRIM COMP switch located on the overhead panel.
• Switch ⇒ OFF deactivates system