27 Flight Controls

 

TTP	B1-L3	ATA 27
Beech 90 Series	B2-L2	Flight Controls

INTRODUCTION

 

The aircraft uses conventional three-axis flight controls; ailerons, elevators, and a rudder. Two electrically driven flaps are on each wing. Ground steering is accomplished by the rudder pedals through a mechanical steering rod attached to the nose landing gear.

GENERAL

 

LJ-1 AND AFTER; LW-1 AND AFTER

 

Flight-control  movement  is  accomplished through single non-redundant cables, push rods, and bell cranks, and are non-powered (with the exception of the rudder boost). The ailerons and elevators are controlled by conventional control columns  interconnected  to  a T-column  behind the  instrument  panel.  The  rudder  is  operated with conventional rudder pedals (a set for both the pilot and copilot). Both are equipped with toe brakes. Each wing has dual flap segments. To prevent damage to the control surfaces, hinges, or control system, the control locks and rudder pin should be installed. Elevator, aileron, and rudder trim are adjustable with manual controls mounted on the center pedestal.  On SNs LJ-1 through LJ-317 there are aileron trim tabs on both the left and right aileron. The elevator and aileron tab incorporate anti-servo mechanisms. Electric elevator trim is provided through switches on the outboard grip of each control wheel. A rudder boost system, to aid the pilot during an engine-out condition, is designed to function automatically as engine bleed-air pressure drops during an engine failure.

AILERON SYSTEM

 

The aileron control system has three subsets of cables.

 

•  One set connects the two control wheels together.

 

•  On the second set, the fuselage cables connect the T-column to the quadrant located forward of the rear spar in the wing center section.

 

•  The third set, consisting of the wing cables, connects the quadrant to the aileron bell- cranks in the outer wing.

Aileron travel is symmetrical with up travel equaling down travel and is limited and adjusted by stop bolts at the outer wing bellcranks. A rig pin hole is provided in the quadrant; no rigging holes are provided on the bellcranks.

Aileron Quadrant Regulator

 

Starting with LJ-1320 (see the Maintenance Manual for specific aircraft), a regulated quadrant was installed that compensates for temperature rates of expansion and changes the rigging procedures for these later aircraft. Wiring cable tensions are determined by reference to the Aileron Quadrant Adjustment Graph in the AMM.

Checking Aileron Tab Free Play

 

Visually inspect the aileron tab for any damage, security of hinge attach point, and for tightness of the actuating system. Inconsistencies should be remedied prior to checking the free play of the tab. This check should be performed at the intervals specified in Chapter 5 of the AMM to make sure that the trim tab free play falls within the prescribed limits.

RUDDER SYSTEM

 

The pilot and copilot rudder pedals are connected to their respective bellcranks with pushrods. The copilot bellcrank is attached to the pilot bellcrank through an interconnecting pushrod. A set of cables from the pilot bellcrank then run aft through the length of the fuselage and fasten to the rudder bellcrank on the bottom of the rudder torque tube. Adjustable rudder centering springs are attached between the aft bulkhead and the rudder bellcrank. With the rudder pedals pinned to the center, the rudder is adjusted 1° to the left and rudder travel is asymmetrical with travel to the left greater than travel to the right. Travel is measured from the vertical stabilizer centerline and can be adjusted with the rudder  bellcrank  stop  bolts.  Secondary  rudder stop bolts limit the travel of the pilot bellcrank. When the rudder reaches the limit of its travel set by the rudder bellcrank stop bolts, a measured clearance must exist between the pilot bellcrank and its stop bolts.

ELEVATOR SYSTEM

 

The elevators are controlled by the pilot control columns which are attached to the T-column. A pushrod is connected to the forward  elevator  bellcrank  at  the  base  of  the T-column. From the forward elevator bellcrank, a set of cables run aft through the length of the fuselage and fasten to the aft elevator bellcrank assembly. Individual left and right pushrods are then connected to the left and right elevator control horns to control elevator movement. Both the forward and the aft bellcranks have rig pin holes. To enhance aircraft handling, two elevator down springs are in the aft fuselage, and an elevator bob weight is attached to the T-column. Bias from the units must be considered during rigging.

 

The elevator control system has three stops:

 

•  Primary stops are contacted by the elevator control horn to limit elevator movement

 

•  Secondary stops are on the forward bell- crank and establish  the limits of control column travel

•  Final stop in the elevator control system is the stop assembly for the bob-weight

FLAP SYSTEM

 

The flaps, two on each wing, are driven by an integral electric motor/gearbox assembly mounted on the forward side of the rear spar on the centerline of the fuselage. A dynamic braking system, operating through the up and down windings of the flap motor and controlled by an assembly containing two dynamic brake relays and contacts, helps prevent over travel of the flaps. The gearbox drives four flexible drive shafts that are connected to individual jackscrew actuators at each flap. There is no split flap protection provided if a flex shaft or jackscrew failure occurs.

The flaps are operated by a three-position lever on the cockpit center pedestal just below the condition levers. Up and approach detents  are built into the flap lever to prevent inadvertent flap extension. The flap lever must be moved to the right to extend the flaps to approach or down. A flap indicator, on the center instrument panel subpanel, shows the flap position in percentage of extension. The indicator is driven by a transmitter connected to the right inboard flap. Flap positioning is controlled with the cockpit flap switch and regulated  by  four  cam-actuated  microswitches that are also connected to the right inboard flap.

 

On C90B/GT/GTi aircraft, the flaps drive to the position selected on the flap lever.

 On C90A/SE aircraft, the flaps can be positioned to any angle between the approach and down setting. If the flaps are set at approach and the lever is moved to the down setting, the flaps start driving toward down. Returning the lever to the approach setting (which is now the off setting) stops the flaps at the selected intermediate position. If the flaps are down, the flap lever must be moved to the up setting to start the flaps retracting. While the flaps are driving up, and are at any position below approach, returning the flap switch to the approach setting (which is still the off setting) stops the flaps at the selected intermediate position. Flap positioning between up and approach for the C90A/SE is the same as it is on the C90B/ GT/GTi. Selecting the up setting drives the flaps up, and selecting the approach setting drives the flaps to approach.

Flaps Full Up

Flap  control  power  is  provided  through  the 20-amp motor circuit breaker on the right CB panel. Power passes through the circuit breaker but stops at the flap dynamic break relay contacts (caused by movement of the cams inside the flap limit switch assembly).

 

Flap indicator and control power is provided through a 5-amp circuit breaker on the right CB panel. Opening of the flap up limit switch deen- ergizes the up dynamic brake relay solenoid, removing power from the up side of the flap motor. Deenergizing the up side of the dynamic brake relay solenoid also provides a ground path for residual energy to pass through the down windings of the flap motor to prevent coasting.

Approach Selected/Selectable Flaps

NOTE: This information applies to LJ-1063 through   LJ-1287,   LJ-1289   through LJ-1294,     and     LJ-1296     through LJ-1299.

 Flap motor power passes through the down contacts of the dynamic brake relay, through the down windings of the flap motor, and then to ground. The flap motor continues to operate until the approach limit switch opens by movement of the cam in the switch assembly.

 When the approach limit  switch  opens, power is removed from the down relay solenoid in the dynamic brake relay. This causes the down relay contacts in the dynamic brake relay to open, providing a ground path for residual energy to pass through the up windings of the flap motor to prevent coasting.

 Aircraft LJ-1063 through LJ-1287, LJ-1289 through LJ-1294, and LJ-1296 through LJ-1299 have selectable flaps. This means that the flaps can be positioned to any angle between approach and down (35% and 100%). In the downward flap direction, this can be accomplished by placing the flap handle in the full-down position, allowing the flaps to pass beyond the approach position (35% to 100%), and then placing the flap handle to the desired angle. In the upward flap direction, this can be accomplished by placing the flap handle in the up position and then placing the flap han- dle in the approach position when the flaps are at the desired angle. When selecting flaps between 35% and 100%, power is provided through either the down flap or up flap control switches in the center console. In both cases, dynamic braking occurs  through  the  respective  dynamic  brake relay contacts.

 Down Selected

 

Flap motor power passes through the down contacts of the dynamic brake relay, through the down windings of the flap motor, and then to ground. The flap motor continues to operate until the down limit switch opens by movement of the cam in the switch assembly.

 When the down limit switch opens, power is removed from the down relay solenoid in the dynamic brake relay. This causes the down relay contacts in the dynamic brake relay to open, providing a ground path for residual energy to pass through the up windings of the flap motor to prevent coasting.

Approach

NOTE: This information applies to LJ-1288, LJ-1295, LJ-1300, and subsequent.

 Flap motor power passes through the down contacts of the dynamic brake relay, through the down windings of the flap motor, and then to ground. The flap motor continues to operate  until the down limit switch opens by movement  of the cam in the switch assembly.

 When the down limit switch opens, power is removed from the up or down relay solenoid in the dynamic brake relay. This causes the down relay contacts in the dynamic brake relay to open, providing a ground path for residual energy to pass through the up windings of the flap motor to prevent coasting.

 

Full Down

NOTE:This information applies to LJ-1288, LJ-1295, LJ-1300, and subsequent.

 Flap motor power passes through the down contacts of the dynamic brake relay, through the down windings of the flap motor, and then to ground. The flap motor continues to operate  until the down limit switch opens by movement  of the cam in the switch assembly.

 When the down limit switch opens, power is removed from the down relay solenoid in the dynamic brake relay. This causes the down relay contacts in the dynamic brake relay to open, providing a ground path for residual energy to pass through the up windings of the flap motor to prevent coasting.

Full Up

            NOTE: This information applies to LJ-1288, LJ-1295, LJ-1300, and subsequent.

Flap motor power passes through the up contacts of the dynamic brake relay, through the up windings of the flap motor, and then to ground. The flap motor continues to operate until the up limit switch opens by movement of the cam in the switch assembly.

 When the up limit switch opens, power is removed from the up relay solenoid in the dynamic brake relay. This causes the up relay contacts  in the dynamic brake relay to open, providing a ground path for residual energy to pass through the up windings of the flap motor to prevent coasting.

CONTROLS AND INDICATIONS

 

 LANDING GEAR WARNING SYSTEM

 

The landing gear warning system is effected by the position of the flaps through one of the right inboard  flap  microswitches.  With  the  landing gear not extended and the flaps set in the up or approach position, retarding one or both of the power levers activates an intermittent warning horn and illuminates the red lights in the landing gear handle. Momentarily depressing the horn silence  button  silences  the  warning  horn. The landing gear handle lights  remain  illuminated. Advancing both power levers deactivates the system. If the flaps are extended below approach and the landing gear is not extended, the warning horn sounds and the gear handle lights illuminate regardless of power lever positions and the horn silence button becomes nonfunctional.

PTP  Beech 90 Series	B1	LOC	FOT	SGH	R/I	MEL	TS
	B2	LOC	FOT

271001 Aileron Controls - Check freedom of movement and proper operation through full                   travel.
271002 Ailerons and Cables - Check operation and security of stops. Check cables for                      tension, routing, fraying, corrosion, and turnbuckle safety. Check travel if cable                     tension requires adjustment or if stops are damaged. Check fairleads and rub strips               for condition

271004 Ailerons and Hinges - Check condition, security, and operation. B 05-12-01 520 620
271005 Control Wheel Lock - Check general condition and operation. C 05-12-01 222
271007 Inspect aileron hinges, hinge bolts, hinge bearings and hinge and pushrod attach                   fittings.
272001 Rudder - Check internal surfaces for corrosion, condition of fasteners, and balance
             weight attachment. C 05-12-03 340
272002 Rudder - Inspect the rudder skins for cracks and loose rivets, rudder hinges for                     condition, cracks and security; hinge bolts, nuts, hinge bearings, hinge attach                         fittings, and bonding jumper for evidence of damage and wear, failed fasteners, and               security. Inspect balance weight for looseness and the supporting structure for                       damage.
272006 Inspect rudder pedal torque tube and cable attachment arms. 
273001 Elevator Control - Check freedom of movement and proper operation through full                   travel. B 05-12-01 222, 223
273002 Elevator Control System - Inspect pulleys, cables, sprockets, bearings, chains, and
             turnbuckles for condition, security, and operation. Check cables for tension, routing,
             fraying, corrosion, and turnbuckle safety. B 05-12-01 222, 
273102 Elevator Trim Control and Indicator - Check freedom of movement and proper                       operation through full travel.
273103 Elevator Trim Tab and Hinges - Check condition, security, and operation.
273106 Elevator Trim Tab Stop Blocks - Inspect for damage and security