Ki 256 Installation Manual -

| Pin | Signal | Wire Color (King harness) | Notes | |------|-----------------------------|----------------------------|---------------------------------------------------| | 1 | +28V DC Erection | Red/White | Powers the vertical erection circuits. | | 2 | Gyro Spin Motor (115V AC) | Brown/Black | 400Hz from inverter or alternator. | | 3 | Gyro Neutral (AC return) | Black | Must be isolated from DC ground. | | 4 | Roll Syncro Stator S1 | Blue | To KI 525A or autopilot computer. | | 5 | Roll Syncro Stator S2 | Yellow | | | 6 | Roll Syncro Stator S3 | Green | | | 7 | Pitch Syncro Stator S1 | Orange | | | 8 | Pitch Syncro Stator S2 | White/Orange | | | 9 | Pitch Syncro Stator S3 | White/Green | | | 10 | DC Ground | White/Black | Also connects to gyro case ground. | | 11 | Flag Output (Normally Open) | Gray | Opens on gyro fail, triggers warning flag. | | 12 | Flag Common | Black/White | | | 13 | +28V DC (Aux) | Red | For lighting (if dimmer not used). | | 14 | Lighting Dimmer Bus | Violet | 0-5V DC typical. |

Critical Warning from the Manual: Do not combine AC ground and DC ground. The KI 256 uses separate returns. Combining them creates ground loops that induce 400Hz noise into the syncro outputs, causing HSI oscillations.

Before touching a screwdriver, know what the KI 256 is and isn't. It is an electrically driven, remote-magnetometer attitude indicator that receives pitch, roll, and slip/skid data from an external attitude gyro (such as the KG 258 or KG 102). It is not a standalone artificial horizon.

Unlike modern AHRS units, the KI 256 requires mechanical and electrical rigging. Section 5 of the ki 256 installation manual details the following procedure: ki 256 installation manual

In the world of glass cockpit retrofits and digital attitude indicators, the Honeywell (formerly King) KI 256 remains a workhorse. As the primary Flight Director (FD) attitude indicator paired with the KFC 150, KAP 150, and KFC 200 autopilot systems, the KI 256 provides critical pitch and roll commands. However, finding a clear, actionable KI 256 installation manual is a common pain point for maintenance shops and owner-assist mechanics.

This article consolidates the essential installation steps, wiring diagrams, post-installation testing, and common pitfalls—based on official OEM documentation and field service experience.

Disclaimer: This guide is for informational purposes only. Always refer to the official Honeywell (Bendix/King) manual, document number 006-10593-0000 (Rev 8 or later), before beginning any installation. Installation must be performed by a certified avionics technician in accordance with 14 CFR Part 43. | Pin | Signal | Wire Color (King