Honeywell King Bendix Maintenance Manual KC 140 FLIGHT CONTR

Honeywell King Bendix FULL MAINTENANCE MANUAL KC 140

This comprehensive maintenance guide is designed for DIY repair enthusiasts, providing detailed insights into the flight control system of the KC 140. With a searchable, bookmarked index spanning 341 pages, this manual delivers the technical information needed for troubleshooting and repairs.

• Manual Number: 006-15573-0000
• Revision: 0, May 2003

4.1 GENERAL

This section covers the block diagram and underlying theory for the KC 140 flight computer. It explains the roles of the four boards within the flight computer:

• Power Supply Board
• Main Board
• Accelerometer Board (Only in two-axis flight computers)
• Display Board

The Main Board integrates most of the system circuitry, while the Power Supply Board provides essential power management. The Accelerometer Board manages signal gains and the Display Board hosts the display and mode switches.

4.2 BLOCK DIAGRAM CIRCUIT THEORY

This section outlines a high-level description of the circuit operation of the KC 140 flight computer.

4.2.1 POWER SUPPLY BOARD

The Power Supply Board is equipped with multiple power circuits, including:

• 5V logic for control circuitry
• 5V audio for alert systems
• 15V circuits for both internal analog and external digital guidance systems
• -185V for display power

Additional outputs include filtered aircraft voltage, 5V analog supply with minimal ripple, and a 4V reference supply for pressure sensor calibration.

• 4.2.1.1 Input Surge Protection

  Both aircraft and audio voltages are surge-protected and filtered separately, ensuring voltage levels do not exceed 34 volts. This protection guarantees reliable operation across different sections of the unit.

• 4.2.1.2 5V Logic Power Supply

  A switching regulator converts the filtered aircraft power (11-34 VDC) to 5 VDC for the logic circuitry. An additional filtering process creates an analog 5V output with reduced noise, followed by further refinement for a stable 4V reference supply used by sensors and controls.

• 4.2.1.3 5V Audio Power Supply

  This regulated and filtered audio voltage supports the audio alert circuitry, ensuring clear and consistent performance.

• 4.2.1.4 15V Power Supplies

  Two identical 15 VDC modules serve different parts of the system: one for internal analog circuitry and another for external digital guidance. The use of separate supplies maintains functionality even with limited current capabilities.

• 4.2.1.5 -185V Display Power Supply

  A flyback regulator delivers -185 VDC for the display, with integrated low-voltage shutdown and overcurrent limiting. Additionally, a buffered resistive divider and zener diode produce -75 VDC and -175 VDC required for the display driver circuitry.