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1.  General
A.  A windshield wiper is provided to maintain a clear area on the pilots' No. 1 windows during takeoff, approach and landing, in rain or snow. Each wiper is operated by a separate system to ensure that clear vision through one of the windows will be maintained in the event of a system failure. The wiper blades clear a path approximately 13-1/2 inches wide through an arc of 84 +4 degrees.
B.  Both wiper systems are electrically operated and controlled by a common gang switch located on the overhead panel. The switch provides a selection of two wiper action speeds ranging from a minimum of 250 strokes per minute with the windshield wiper switch in HIGH position to a minimum attainable speed commensurate with stable motor operation with switch in LOW position and controls the stowing of the wiper blades in a PARK position when the system is not in use.
C.  Each windshield wiper system consists of a drive motor and torque converter assembly, a control switch, a resistor box, and a windshield wiper assembly (Fig. 1).
D.  Speed control is accomplished by changing the voltage applied to the windshield wiper motor by means of resistances arranged in the resistor box. The required resistance is connected into the motor circuit by turning the windshield wiper switch to a selected speed (Fig. 2). The rotary motion of the drive motor is transmitted to the converter, which reduces the shaft speed and changes rotary motion to an oscillating motion of the windshield wiper arm.
CAUTION: DO NOT OPERATE WINDSHIELD WIPERS ON DRY WINDSHIELDS.
E.  A second method for maintaining clear windows in heavy rain is by the use of rain repellant (Ref 30-43-0, Rain Repellant System).
526 
Jun 20/86  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  30-42-0 Page 1 

2.  Motor-Converter Assembly
A.  The wiper assembly for each system is driven by a motor-converter assembly. The motor-converter assembly consists of a 28 volt dc variable speed electric motor and torque converter coupled together by a connector sleeve and assembled on a support fitting. Each assembly is mounted on a bracket on its respective windowsill close to the inner surface of the skin.
B.  Each motor is equipped with two radio noise filters, an automatically resetting thermal overload switch, and a cam actuated switch. The thermal switch temporarily opens the motor field circuit when the motor temperature exceeds 300°F, or when the field current exceeds 8 to 10 amps. The cam-actuated switch is a two pole two position microswitch. The operating cam is driven by reduction gearing in the motor to coincide with the wiper cycle. One pole of the switch is closed when the motor is in any part of the wiper cycle other than PARK. The other pole of the switch is closed only when the motor is in the PARK position of the cycle. The switch is used in conjunction with the system control switch to stop the motor with the wipers in the PARK position when the system is not in use.
C.  The converter has a serrated drive shaft, which protrudes through the skin just forward of the windshield for attachment of the wiper assembly. The converters change the high-speed low torque rotary motion of the motor to a low speed high torque circular oscillating motion for the wiper arm, by the use of a worm gear and eccentric drive mechanism. The motor and converter are synchronized with respect to the wiper cycle before the units are coupled together.
3.  Control Switch
A.  The windshield wiper control switch is a four position-double wafer-rotary gang switch. The switch is located on the overhead panel and is used to control the action of both windshield wiper motors by changing the motor circuitry. The switch has a momentary PARK position and three detent positions, OFF-LOW- and HIGH.
526 
30-42-0 Page 2  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/69 

F88306
526  Windshield Wiper System Component Location 
Aug 15/69  Figure 1  30-42-0 
Page 3 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

4.  Resistor Box
A.  Each windshield wiper system has a resistor box for its motor (Fig. 1). The box contains three resistors, which may be selected by the control switch to be added in series with the motor circuit to control the motor speed.
5.  Wiper Assembly
A.  The windshield wiper assembly consists of a wiper blade and wiper arm. The wiper arm has a serrated sleeve at its hub to provide angular adjustment between the arm and the converter drive shaft, and is attached to the shaft by a bolt through the hub. The wiper tension of the arm can be adjusted by a tension-adjusting nut near the hub of the arm. The wiper blade is bolted to the end of the wiper arm and the angle between the blade and the arm can be adjusted by means of a serrated disc attached to each part.
　
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