B737 Ng Flight Control System Engineering Essay

In this chapter the differences of the Airbus A320 and Boeing 737 NG will be discussed. There will be looked at the flight control system of the Boeing 737 NG and the flight control system of the Airbus A320 ( 2.2 ) after that a comparing between the conventional system and fly-by-wire system ( 2.3 ) .

2.1 B737 NG flight control system

This subdivision will discourse the flight controls of the Boeing 737 NG. At first the primary flight controls particularly the ailerons ( 2.1.1 ) and besides the secondary flight controls of the Boeing 737 NG draging border devices ( 2.1.2 ) will be discussed.

2.1.1 Primary flight controls

In this subdivision, the primary flight controls of the Boeing 737NG will be discussed. The ailerons will be investigated as primary flight control in this chapter. The composing of the system ( 2.1.2a ) , the input of the system ( 2.1.2b ) , the transit of signals ( 2.1.2c ) , the end product signals ( 2.1.2d ) and the hydraulic system of the Boeing 737NG will be discussed ( 2.1.2e )

2.1.1a Composition

The aileron system exist of two ailerons. The Boeing 737 has an aileron on each wing. They are placed on the outer side of the wing to make a greater minute over the aeroplanes longitudinal axis. Over this axis the aeroplane will be able to turn over. Because the ailerons are mounted on the outer side of the flying the needful forces can be lower than when they are placed on the interior side of the wing. The minute of the aileron is the force multiplied by the arm length.

2.1.1b Input signal

The ailerons are positioned by the control wheels of the pilots. When the pilot controls his maneuvering wheel a mechanical cardanic motion will do the input signal transferred to the transportation mechanism.The transferm mechanism maintain the control wheel motion to a bound

of 107.5 grades left and right. This mechanism is mounted under the maneuvering column of the pilot. The axial rotation axis force transducer is mounted between the control shaft and aileron membranophone below the captain ‘s control column. The force transducer provides double electrically stray Ac end product signals that are relative to the force applied to the control wheel or column. The signals are used by the automatic pilot computing machines when the system is engaged in CWS ( manual ) manner or in CMD manner with no flight manner selected. Both control wheels are overseas telegram mounted connected to each other, when the captain maneuver his control wheel the left aileron control coach membranophone will revolve and operated the control overseas telegram to revolve the right aileron control coach membranophone. This membranophone is connected precisely as the captains control wheel and the first officers control wheel will travel.

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2.1.1c Conveyance

By revolving the control coach membranophone, the control membranophone besides will revolve. The control overseas telegram will be operated and will run through the aeroplane and routed by overseas telegram ushers and maintain on tenseness with overseas telegram tensioners. In the chief wheel good the overseas telegram will be attached to the aileron organic structure quadrant. On the quarter-circle the new surpassing overseas telegram is mounted. The quarter-circle is mounted on two aileron power control units ( PCU ) . This PCU ‘s are mounted at the aileron control quarter-circle. On this quarter-circle the aileron input shaft is mounted. On this shaft the automatic pilot control rod, the PCU ‘s four pogo input grouchs, the feel and focus oning unit and the aileron actuator are mounted.

For backup two PCU ‘s are mounted to assist the pilot to make a higher force to the ailerons so the pilot do n’t necessitate all his strength to command the ailerons. Besides there are four pogo inputs installed between the organic structure quadrant and the input shaft. These are to command the motion of the overseas telegrams so that they are on tenseness at all times and non travel when the do n’t necessitate to. The feel and focus oning unit is used to place the ailerons to his impersonal place. This can be done by motion of both aileron trim switches on the aft electronic panel. The aileron spare actuator can place the aileron input shaft to pare the system. The entire spare the pilot have made can be read on the aileron spare index on the control wheel. The automatic pilot aileron actuator is duplicated for safety grounds. The automatic pilot actuator is with the automatic pilot input rod mounted to the aileron input shaft. This actuator will be electronic controlled by the flight control computing machines. All the actuators are hydraulic controlled by system A and B.

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2.1.1d End product

The control overseas telegrams will led through the wings until they reach the aileron wing quarter-circle. This quarter-circle is kept on tenseness by the aileron overseas telegram tenseness spring. This for that the trenched out overseas telegrams are kept on tenseness. The quarter-circle is connected with and pushrod connexion to the aileron. On the aileron an aileron balance check is mounted and connected with control rods. The aileron is armed with four balance panels to maintain the balance in the ailerons. And this panels are equipped with fixed balance weights. The end product signal of this system is that the aileron will travel up or down after motion that the pilot will do by traveling the control wheel.

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2.1.1e Hydraulic system

The ailerons are powered by system A and B. When both of this systems fails, the aileron can still be operated manually by commanding the overseas telegrams. The left aileron is powerd by system a and the right aileron is powered by system B.

During normal operation of the ailerons, an aileron input goes through the input pogos of each PCU to its input grouch. The upper and lower input grouchs move, slides in the control valve, and provide hydraulic force per unit area to the actuator. The lower input grouch is connected to the primary slide and the upper input grouch is connected to the secondary slide. A tortuosity spring inside the PCU connects the two input grouchs. Motion of the primary slide supplies one-half the entire flow rate, and motion of the secondary slide supplies the other half. The primary slide moves to its full effectual shot before the secondary grouch starts to travel the secondary slide. When the primary and secondary slides move, hydraulic force per unit area goes through the control valve to one side of the actuator. This moves the actuator lodging and the several aileron organic structure quadrant to the commanded place. The other side of the actuator is connected to the return.

If one PCU ca n’t provide a hydraulic force per unit area, its beltway valve will be activated and moves to the beltway place. This connects the two sides of the actuator, and prevents a hydraulic lock status. When the pilot moves the control wheel, the ON side PCU still moves to his commanded place usually. As the ON side PCU moves, it besides moves his several aileron organic structure quarter-circle and back drives the OFF side PCU actuator lodging. When the OFF side lodging moves, hydraulic fluid is pushed through the beltway valve. If one PCU input pogo ca n’t travel freely, the pilot must provide about 20 lbs of extra force to compact or widen the spring inside the pogo. The other PCU input pogo still moves its ain input grouch and slide to the commanded place. This equalizes force per unit area on both sides of the actuator and prevents a hydraulic lock status. Now the other PCU can travel the aileron organic structure quadrant assembly usually. As the ON side PCU moves its several aileron organic structure quarter-circle it besides back drives the OFF side PCU actuator lodging. When the OFF side lodging moves, hydraulic fluid is pushed through the beltway valve.

During a manual reversion, the beltway valve receives no hydraulic force per unit area and moves to the beltway place. This connects the two sides of the actuator and prevents a hydraulic lock status. When the pilot moves the control wheel more than three grades, the primary and secondary input grouchs hit the mechanical Michigans on the exterior of the actuator lodging. As the lodging moves, hydraulic fluid in the actuator is through the beltway valve. Motion of the lodging besides moves the aileron organic structure quadrant assembly to the commanded place.