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.
| 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 you have a clean PDF of the Narco Escort II Installation Manual (Full, not just the pilot guide), consider uploading it to the AOPA Forums or Vintage Avionics Library. Preserve this knowledge for the next restorer. Researched from Narco technical documents, FAA STC SA2076SO, and avionics trade archives. Verified pinouts against the Escort II Maintenance Manual Rev C. If your aircraft has a modern encoder (e
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. The official manual contains Section 5: Test and Calibration