Ki 256 Installation Manual Review

| Symptom | Likely Cause | Solution | |---------|--------------|----------| | OFF flag visible | No vacuum or gyro not spun up | Check vacuum line and electrical power | | Roll flag only | Missing roll command return (pin H) | Verify wiring continuity | | Bars stuck full scale | Command signal shield grounded at KI 256 | Remove ground loop — shield only at source | | Erratic attitude | Vacuum too high or low | Adjust regulator to 5.0 inHg | | No backlight | Voltage mismatch (28V to 5V lamp) | Install dropping resistor per manual Fig 6-3 |

From the field: A common mistake is skipping the 3-minute warm-up. Doing so leads to false nulls and autopilot “porpoising.”

Apply 28V DC and 115V AC. Allow 3 minutes for spin-up. Depress the “CAGE” button on the KCS 55 controller for 10 seconds.

The KI 256 installation manual dedicates five pages to wiring. Below is the essential pinout for a standard KFC 150 autopilot integration. Always verify against your specific serial number.

| Pin | Function | Signal Type | Wire Gauge | |-----|----------------------|----------------------|------------| | 1 | Power Input (14V or 28V) | DC Power | 22 AWG | | 2 | Power Ground | Ground | 22 AWG | | 3 | Pitch Gyro Signal (3.8V RMS) | 400Hz AC | 24 AWG shielded | | 4 | Pitch Gyro Reference | 400Hz AC Return | 24 AWG | | 5 | Roll Gyro Signal | 400Hz AC | 24 AWG shielded | | 6 | Roll Gyro Reference | 400Hz AC Return | 24 AWG | | 7 | Slip/Skid Sensor (+/- 150mV) | DC Analog | 22 AWG twisted | | 8 | Slip/Skid Return | DC Ground | 22 AWG | | 9 | No Connection | N/A | N/A | | 10 | Flight Director Pitch (Command) | 0-5V DC | 22 AWG shielded | | 11 | Flight Director Roll (Command) | 0-5V DC | 22 AWG shielded | | 12 | Synchro Stator C (Roll) | 26V 400Hz | 24 AWG | | 13 | Synchro Stator B (Roll) | 26V 400Hz | 24 AWG | | 14 | Synchro Stator A (Roll) | 26V 400Hz | 24 AWG | | 15 | Lighting Power | 5V or 14V AC/DC | 22 AWG |

Document P/N: 006-10565-00
Rev: C
Applicability: KI 256 Electric Attitude Indicator (14V & 28V systems)

The most critical mechanical step often overlooked in the ki 256 installation manual is the mounting orientation.

If you want, I can expand this into a full formatted manual with wiring diagrams, exact electrical ratings, firmware update steps, or a printable PDF.

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The BendixKing KI 256 is a critical vacuum-driven Flight Command Indicator used extensively in legacy flight control systems like the KFC 150, KFC 200, and KFC 225. It serves a dual role: providing a visual attitude display for the pilot and supplying pitch and roll attitude data to the autopilot computer. ki 256 installation manual

Proper installation is vital, as any misalignment or contamination during the process can lead to autopilot "hunting" or complete system failure. Technical Specifications

Understanding the physical and electrical requirements is the first step in a successful installation:

Power Input: Supports +14VDC or +28VDC (0.7AMP max) and 10VAC at 430Hz (0.2AMP max). Weight: Approximately 3.3 lbs.

Tilt Options: Available in 0-degree or 8-degree panel tilt configurations to match the specific aircraft's instrument panel angle.

Air Source: Internally air-driven, requiring a regulated vacuum source of 4.5 in. Hg. Mechanical Installation

The KI 256 is designed for standard instrument panel mounting.

Panel Cutout: It fits into a standard 3-inch instrument hole.

Clearance: Ensure adequate depth behind the panel for the unit and its electrical and vacuum connectors.

Cleanliness: Work must be performed in a clean environment to prevent contaminants from entering the vacuum ports, which can cause gyro precession. Electrical & Vacuum Connections | Symptom | Likely Cause | Solution |

A secure and correctly wired interface is essential for the flight director and autopilot functions. Vacuum System

Regulation: Connect to a filtered and regulated 4.5 in. Hg vacuum source.

Failure Warning: Check that the "gyro" or "vacuum" warning flag on the unit face is operative. Wiring and Pinouts

The electrical connector interfaces the unit with the autopilot (e.g., KC 295 computer).

Attitude Outputs: Pins provide buffered pitch and roll attitude signals to the flight computer.

Command Bars: Receives steering commands from the computer to drive the single-cue command bars.

Static Protection: Always handle the unit at a static-safe workstation, as the internal circuit boards are highly sensitive to ESD. Alignment and Testing

Once installed, the system requires precise calibration to ensure the autopilot and manual flight director cues are synchronized.

Leveling: Mount the aircraft (or use a gyro tilt stand) to a level flight attitude. From the field: A common mistake is skipping

Zeroing: Use a specialized test set like the KTS 150 or KTS 151 to zero the command bars.

Functional Test: Verify that the unit erects quickly and remains stable. If the unit precesses or is slow to erect, the internal bearings may be contaminated, necessitating an overhaul.

💡 Maintenance Note: The KI 256 is an overhaul-intensive unit. Modern upgrades like the KI 300 electronic indicator or Garmin GI 275 are often used to replace the KI 256 to eliminate vacuum reliability issues.

If you'd like to move forward with the installation, could you tell me:

Which autopilot system (e.g., KFC 200, KFC 150) are you pairing it with?

Do you have the specific aircraft tail number or model to find the exact STC-approved wiring diagram?

Are you performing a new install or a replacement of an existing unit?

I can provide the specific pinout charts or troubleshooting steps based on those details. BendixKing KI-256 | SEAEROSPACE.COM

If "ki 256" could refer to a specific product, software, or hardware from a certain manufacturer or a generic term used in a particular field (like electronics, software, etc.), here are a few general steps and considerations that might help in creating or understanding an installation manual: