P-180 PTG - Section 8 - Flight Controls by Donald Sims

Flight Controls

Piaggio Avanti

SimsAir

The conventional primary flight controls are operated by dual control wheels and pedals. The control wheels operate the ailerons and the elevators. The adjustable pedals operate the rudder and the nose steering. The toe brakes, which are an integral part of the pedals, operate the wheel brakes. The pilot and copilot's rudder pedals are individually adjustable through the RUDDER PEDAL ADJ control handles on both lower sides of the instrument panel close to the cockpit walls. Pulling out and holding the handle the spring-loaded pedals adjusting mechanism unlocks allowing to readjust the pedals only by pushing the pedals to the desired position. At this point, pushing in the handle, the rudder pedal adjusting mechanism locks again. Rudder Pedal Adjust Knob

Elevator Control

The control surfaces are mechanically connected to the pilot controls through systems of cables, pulleys, push-pull rods and bell cranks. An up-down spring mechanism, linked to the stabilizer, is

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Flight Controls

installed in the longitudinal control system to provide a suitable pilot stick force through the complete center of gravity range. Aileron Control

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Piaggio Avanti

SimsAir

Rudder Control

Secondary control is provided by the aileron and rudder trim tabs for roll and yaw, and by the allmovable horizontal stabilizer for pitch attitude. All trimming surfaces are electrically operated and controlled. The roll trim is accomplished by positioning the aileron trim tab on the inboard trailing edge of the right aileron through actuation of the roll trim actuator. The roll trim system operates on the left single feed bus through the 3-amp ROLL TRIM circuit breaker on the pilot's circuit breaker panel. The aileron trim is controlled through the pilot and copilot's control wheel trim switches (CWTS).

Each control wheel trim switch is a dual-function (trim and trim arming) switch, which controls roll trim and primary pitch trim. One switch is located on the outboard horn of each control wheel. Rev 1

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Piaggio Avanti

Flight Controls

Each switch has four positions: LWD, RWD, NOSE UP and NOSE DN, The arming button on top of each switch must be depressed for trim motion to occur. Actuation of either control wheel trim switch to LWD or RWD will signal the aileron trim tab actuator to move the tab as required to lower the appropriate wing. Actuation of the pilot's switch will override actuation of the copilot's switch. Aileron trim tab position indication is provided by the ROLL indicator located in the TRIM indicator panel in the center pedestal. Two semi-circular scales and a pointer present the trim tab position in terms of LWD (left wing down) and RWD (right wing down). The scales markings represent increments of trim tab travel. The indicator operates on the right single feed bus through the 3-amp TRIM POSN circuit breaker on the copilot's circuit breaker panel. The yaw trim is accomplished by positioning the rudder trim, tab on the lower trailing edge of the rudder through actuation of the yaw trim actuator. The yaw trim system operates on the 28 VDC left single feed bus through the 3-amp YAW TRIM circuit breaker on the pilot's circuit breaker panel.

The yaw trim is pilot-controlled through the RUDDER TRIM switch located on the pedestal trim control panel. The switch has three positions: NOSE LEFT, OFF and NOSE RIGHT. The switch knob is split and both halves must be rotated simultaneously to initiate yaw trim motion. When the switch is released both halves return to the center OFF position.

Actuation of the rudder trim switch to NOSE LEFT or NOSE RIGHT will signal the yaw trim actuator to move the rudder trim tab in the appropriate direction. Rudder trim tab position 8-4

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Piaggio Avanti

SimsAir

indication is provided by the YAW indicator located in the TRIM indicator panel in the center pedestal, a semi-circular scale and pointer indicates the direction (L or R) of yaw trim. The scale markings represent increments of rudder trim tab travel. The indicator operates on the right single feed bus through the 3-amp TRIM POSTN circuit breaker on the copilot's circuit breaker panel. Pitch trim is accomplished by repositioning the horizontal stabilizer to the desired trim setting through actuation of the horizontal stabilizer pitch trim actuator. The three-motor, screw-jack type actuator has a primary and a secondary mode of operation.

Primary trim control circuits operate on the left dual feed bus through the 3-amp PRI PITCH TRIM circuit breaker on the pilot's circuit breaker panel. Secondary pitch trim control circuits operate on the essential bus through the 5-amp SEC PI'T'CH TRIM circuit breaker on the pilot's circuit breaker panel. When in primary mode: • • •

One motor drives the lower rate pitch trim changes in the range from 2° ND to 2° degrees NU. Second motor drives the high rate pitch trim changes in the range from 2° NU to 8° degrees NU. Third motor is operated by the autopilot at the low rate speed.

When in secondary mode the autopilot is disengaged and the manual control only is allowed through the low rate motor in the range from 2° ND to 8° degrees NU. The primary and secondary pitch trim systems are electrically independent and mode selection is made through PITCH TRIM selector switch located on the pedestal trim control panel. The switch has three positions: PRI, OFF and SEC. When the switch is set to PRI trim changes are accomplished through the control wheel trim switches (CWTS). When the switch is set to SEC trim changes are accomplished through the pedestal NOSE DN-OFF-NOSE UP split switch. Rev 1

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Piaggio Avanti

Flight Controls

When the switch is set to the OFF position, both pitch trim electrical control circuits are isolated from the airplane electrical system. The autopilot is inoperative with the PITCH TRIM selector switch in the OFF position. Each control wheel trim switch (CWTS), located on the outboard horn of each control wheel, is a dual function (trim and trim arming) switch which controls primary pitch trim and roll trim. Each switch has four positions: LWD, RWD, NOSE UP and NOSE DN. The arming button on top of each switch must be depressed for trim motion to occur. Actuation of either control wheel trim switch to NOSE UP or NOSE DN will signal the primary mode motors in the pitch trim actuator to move the stabilizer in the appropriate direction. Actuation of the pilot's switch will override actuation of the copilot's switch. Actuation of either switch to any of the four positions when the autopilot is engaged (without pushing the arming button) allows to insert autopilot pitch and roll attitude changes. The NOSE DN-OFF-NOSE UP switch, on the pedestal trim control panel, controls secondary pitch trim. The switch is spring-loaded to the center (OFF) position and is split in two parts: only moving both halves together the appropriate movement of the horizontal stabilizer is obtained. With the PITCH TRIM selector in the SEC position, actuation of the switch will drive the third motor of the horizontal stabilizer pitch trim actuator to move the stabilizer in the appropriate direction only at the low rate speed. When the SEC trim has been selected the autopilot cannot be engaged. With the PITCH TRIM selector in the PRI position, this switch has no effect. A control wheel Master Switch (MSW) is located beneath the control wheel trim switch on the outboard horn of each control wheel.

Each momentary type control wheel Master Switch, when depressed, will inhibit either primary or secondary pitch trim or rudder trim in the event of an actuator runaway. In addition the control wheel Master Switch provides the autopilot disconnection as well as the nose steering release. A trim-in-motion audio signal system is installed on the primary pitch trim actuator to alert the crew of horizontal stabilizer movement. Horizontal stabilizer trim position indication is provided by the PITCH indicator located in the trim indicator panel on the pedestal. ND and NU markings indicate the direction of trim travel for airplane nose down and airplane nose up respectively. The indicator operates on the right single feed bus through the 3-amp TRIM POSTN circuit breaker on the copilot's circuit breaker panel. The scale markings represent increments of two degrees of the longitudinal trim travel.

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Piaggio Avanti

SimsAir

FLAP SYSTEM Forward Wing Flap

Main Outboard Wing Flap

Main Inboard Wing Flap

The electrically controlled flap system provides setting of the forward and the main wing flap surfaces. The flap control system consists of four mechanically independent subsystems: • The Main Wing Outboard Flaps (MWOF) • The Main Wing Inboard Flaps (MWIF) • The Forward Wing Left Flap (FWLF) • The Forward Wing Right Flap (FWRF) The operation of the four subsystems is coordinated by an Electronic Control Unit, which controls the power supply to the D.C. motors of each subsystem actuator.

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Flight Controls

A Drive Unit, located in the center of the fuselage, embodies the two independent motors and gear trains which actuate the main wing outboard flaps (MWOF) and inboard flaps (MWIF) subsystems. Each Fowler-type outboard flap runs on two tracks and is actuated by two screw jacks. The screw jacks of the left and right surfaces are mechanically interconnected through rotating shafts linkages engaged on the drive unit.

Each single-slotted inboard flap is actuated by a single screw jack connected to the drive unit through a rotating shaft. 8-8

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The mechanically independent left flap (FWLF) and right flap (FWRF) of the forward wing are single-slotted type. Each surface is driven by an electromechanical dual linear actuator. A gated FLAP control lever, located on the control pedestal right side of the condition levers, allows setting the flaps through a flap selector switch. The control lever has three positions: UP (clean setting), MID (takeoff setting) and DN (landing setting). Each setting can be selected moving the control lever to the desired position: from UP to MID, from MID to DN and vice versa (single step command), or directly from UP to DN and vice versa (direct command).

NOTE The use of single step control is recommended as normal operating procedure. Stop micro switches control the surfaces stopping in the selected position. In addition mechanical stops are provided in the UP and DN configurations.

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Piaggio Avanti

Flight Controls

Moving the FLAP lever from UP to MID the flap surfaces deployment will be completed in 16 seconds (nominal) as per the following schedule: • • • •

The main wing outboard flaps will start traveling while the inboard flaps and the forward wing flaps will rest in the clean setting. After 9 seconds (nominal) of delay the forward wing flaps also will start then stop after 1 second of travel; the inboard flaps remain in clean setting; the main wing outboard flaps motion continues. After further S seconds (nominal) of delay the inboard flaps also will start; the forward wing flaps will restart; the main wing outboard flaps motion continues. After further 2 seconds all the flaps sections will reach the takeoff setting.

When the flap control lever is moved from MID to DN all the flap surfaces simultaneously will start motion and will reach the full extension in 5 seconds (nominal) travel. The flap retraction requires 5 seconds (nominal) from the landing to the takeoff setting (FLAP lever from DN to MID) and 16 seconds (nominal) from the takeoff to the clean setting (FLAP lever from MID to UP). All flap subsystems start retracting simultaneously. Flap Setting UP MID DN

Flap Setting Table Fwd Wing Flaps Main Wing O.B. Flaps 0˚ 0˚ 13˚ 10˚ 30˚ 30˚

Main Wing I.B. Flaps 0˚ 20˚ 45˚

The FLAPS position indicator, mounted in the center of the lower section of the instrument panel, provides the crew with visual indication of flaps surfaces position. The indicator face consists of two arc scales and pointers in the upper section and two vertical scales and pointers in the lower section. All the scales have markings for UP, MID and DN positions. The arc scales show the position of left and right forward wing flaps. The OUTB vertical scale on the left side shows the position of the main wing outboard flaps. The INB vertical scale on the right side shows the position of the main wing inboard flaps. Each flap subsystem actuating motor drives a potentiometer, which provides the position, signal to the corresponding indicator scale through the electronic control unit.

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Piaggio Avanti

SimsAir

A FLAP SYNC caution light on the annunciator display will come on in the event of either a system failure is detected or an asymmetric/incorrect flaps deployment occurs. Airplanes without S.L. 80-0020. An acoustic warning will be generated whenever the flaps are lowered to the DN position and the landing gear is not locked down. In addition the acoustic warning will be generated whenever the flaps are in the MID position, the landing gear is not locked mown and the left power lever is retarded approximately below- the half travel position. Airplanes incorporating S.L. 80-0020. An acoustic warning will be generated whenever the flaps are lowered to the MID OR DN position and the landing gear is not locked down. In addition, at the takeoff, the acoustic warning will be generated if the flaps are not retracted to the clean (UP) setting within approximately 25 seconds after the landing gear has been retracted. The 326 Hz warning tone cannot be silenced by the mute switch and will continue until either the landing gear is extended or the flaps are retracted to the clean (UP) setting. The SYS TEST selector switch allows testing the system after being rotated to the FLAPS position. A MID Interlock Control (MIC) in the electronic control unit checks the main wing outboard flaps and both forward wing flaps subsystems for the transit through the MID setting when the FLAP control lever is moved directly from either UP to DN or DN to UP (direct command). There is no check on the main wing inboard flaps subsystem. The MID Interlock Control inhibits further travel beyond the MID position until all the checked subsystems have reached this configuration. If an asymmetric flap condition occurs after such direct command, in order to reduce the asymmetry (if necessary) the FLAP control lever can only be moved to the previous (UP or DN) position. If an asymmetric flap condition occurs after a single step command, the FLAP lever can only be moved to the previous position for recovering the original flaps configuration. The flap system operates on 28 VDC supplied from the left generator bus through a 35-ampere remote control circuit breaker located in the baggage compartment: this breaker can be reset: through the 0.5-ampere FLAPS PWR circuit breaker on the copilot circuit breaker panel. As further protection three circuit breakers are provided, all located on the copilot circuit breaker panel: the 3-ampere L FWD WING FLAP and R FWD WING FLAP circuit breakers that protect respectively the left and the right forward wing flap actuators, and the 10-ampere OUTB WING FLAP circuit breaker that protects the main wing outboard flaps actuator.

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Piaggio Avanti

Flight Controls

CONTROL LOCKS The control lock consists of a clamp, a pin and a connecting rod joined together with a chain. The pin and the connecting rod lock the primary flight controls while the clamp fits around the engine control levers in order to avoid starting the engines with the flight control locks installed. It is important that the locks be installed and removed together to preclude the possibility of an attempt to taxi or fly the airplane with the engine control released and the flight controls locked.' Install the control locks in the following sequence: 1. Connect the pilot control column and the pilot rudder pedals by means of the connecting rod with the pedals aligned at neutral insert the long pin of the rod through the pedals locking holes then insert the short pin of the rod through the control column locking plate. 2. Insert the pin through the hole provided in the rear side of the pilot control wheel when centered. 3. Position the clamp around the engine control levers. Remove the locks in the following order: first the connecting rod from the control column and the rudder pedals, then the pin from the control wheel and, as last step, the clamp from the engine control levers.

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