|
|
Disclaimer: This article is for informational and educational purposes only. Aircraft avionics installation requires appropriate licensing (such as an A&P certificate with an Instrument Rating or a Repairman Certificate). Always refer to the official Narco Avionics Escort II Installation Manual (P/N 057-001-0025) for specific data. Narco Avionics is no longer in business; therefore, no manufacturer technical support is available. Introduction: The Forgotten Workhorse The Narco Escort II (often designated as AT-150) is a legacy Air Traffic Control Transponder (Mode A and Mode C) that was ubiquitous in General Aviation (GA) cockpits throughout the 1980s and 1990s. While largely replaced by Mode S and ADSB-Out systems today, thousands of these units remain installed in vintage Pipers, Cessnas, and homebuilts as secondary transponders or in non-rule airspace.
| Pin | Function | Wire Color (Typical) | Notes | | :--- | :--- | :--- | :--- | | 1 | Chassis Ground (P1) | Bare | Bond to airframe | | 2 | +14/28V Input | Red/Orange | Requires 5A circuit breaker | | 3 | Power Ground (Return) | Black | Size 16 AWG | | 4 | Encoder Data A1 (Gray) | White/Gray | Gillham code | | 5 | Encoder Data A2 (Blue) | White/Blue | Gillham code | | 6 | Encoder Data A4 (Green) | White/Green | Gillham code | | 7 | Encoder Data B1 (Yellow) | White/Yellow | Gillham code | | 8 | Encoder Data B2 (Brown) | White/Brown | Gillham code | | 9 | Encoder Data B4 (White) | White/Red | Gillham code | | 10 | Encoder Data C1 (Red) | White/Black | Gillham code | | 11 | Encoder Data C2 (Orange) | Orange | Gillham code | | 12 | Encoder Data C4 (Slate) | Slate | Encoding altimeter sync | | 13 | Panel Dimming Bus | Blue | 0 to 5V DC dimming | | 14 | Ident Switch (Remote) | Green | Momentary to ground | | 15 | Transponder Antenna | Center Conductor | RG-400 coaxial | | 16 | Antenna Shield | Braid | 360-degree bond | | 17 | Encoder Common (Return) | Black/White | Encoder ground | | 18 | Spare | N/A | No connection | | 19 | Spare | N/A | No connection | narco escort ii installation manual full
If your aircraft has a modern encoder (e.g., ACK A-30), you must wire pins 4 through 12 directly. The manual includes a truth table for altitudes from -1000 to +35,000 feet. A mis-wired encoder is the #1 cause of "Mode C" failures on ramp checks. The official manual contains Section 5: Test and Calibration . Without this, your shop cannot sign off a 337 form. Narco Avionics is no longer in business; therefore,
| Â |