Garmin GPS-155 Installation Manual

The Garmin GPS-155 is a panel-mounted TSO-C129a1 Class A1 GPS sensor and navigation system designed for certified aircraft. It provides en route, terminal, and non-precision approach (LNAV) capability. This manual covers essential information for the safe and proper installation, configuration, operation, and maintenance of the unit. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

Features at a Glance

Key components: Panel-mounted display/control unit, Remote GPS Sensor/Receiver (Antenna), Interface/Data Cable Harness.

Installation Overview

Installation must be performed by qualified personnel in accordance with FAA AC 43.13-1B, approved data, and this manual.

1. Mounting: Cut a standard 3.125-inch (79 mm) diameter hole in the instrument panel. Secure the unit using the provided mounting clamp.
2. Antenna Installation: Mount the remote antenna on the aircraft exterior (typically on top of fuselage or cabin) with a clear view of the sky. Ensure proper bonding to the aircraft skin.
3. Wiring: Connect the provided cable harness to the aircraft's power bus (via a dedicated circuit breaker), ground, and any desired interface equipment (HSI, CDI, audio panel, etc.).
4. Secure Cabling: Route and secure all wiring away from sharp edges, high-temperature areas, and sources of interference.

WARNING! Ensure aircraft power is OFF during installation. Confirm weight and balance calculations after installation. Verify no interference with other navigation or communication equipment.

First-Time Configuration

After installation and power-on, perform initial configuration.

1. Power On: Apply aircraft power. The unit will perform a Power-On Self-Test (POST).
2. Set System Mode: Navigate to the SETUP page. Confirm or set the system mode to "GPS" (not "VLOC").
3. Configure Interfaces: On the SETUP > INTERFACE page, set the ARINC 429 and serial output formats to match your installed avionics (e.g., HSI type, autopilot model).
4. Initialize Position: On the satellite status page, allow the unit to acquire satellites. You may need to enter an approximate initial position (airport identifier) to speed up acquisition.
5. Load Database: Insert a current Jeppesen NavData card. The unit will automatically recognize and load the data.
6. CDI/Scale Selection: Set the CDI sensitivity (e.g., Enroute ±5.0 nm, Terminal ±1.0 nm, Approach ±0.3 nm).

CAUTION! Do not attempt flight using GPS for navigation until a successful satellite acquisition, RAIM check, and database validity confirmation are complete.

Specifications

• Physical (Display Unit): 3.125" dia. panel cutout, depth behind panel: 6.5 inches.
• Power Requirements: 10.5-32 VDC, 1.5A max at 14V.
• GPS Receiver: 12 parallel channel, all-in-view tracking.
• Accuracy: <15 meters RMS, 95% typical.
• Velocity Accuracy: 0.1 knot RMS.
• Update Rate: 1 second.
• Database Capacity: Jeppesen NavData Card (Type II PCMCIA).
• Environmental: TSO-C129a1 for temperature, altitude, vibration.
• Output Protocols: ARINC 429 (High/Low Speed), NMEA 0183, RS-232.
• Operating Temperature: -15°C to +55°C.

Controls and Interface

Primary control via front panel keypad and concentric knob.

Front Panel: POWER Knob (Volume/Push), Direct-to (D) Key, CLR Key, ENT Key, MENU Key, concentric outer knob (cursor/page) and inner knob (data entry).

Pages: Cycle through using the outer knob: SAT (Satellite Status), NRST (Nearest Airports), WPT (Waypoint Info), AUX (Setup, Utilities).

Setup Menu (AUX Page): System Mode (GPS/VLOC), Interface (ARINC, Serial), CDI/Scaling, Alarms, Units (nm/km), Datum, System Tests.

Annunciator LEDs: MSG (Message/Alert pending), ALERT (Integrity/RAIM alert), and status lights for power and data.

Connecting to Aircraft Systems

Typical connections for integrated avionics.

1. Power & Ground: Connect Red wire to a 5A circuit breaker on the aircraft bus. Connect Black wire to a clean aircraft ground point.
2. HSI/CDI (ARINC 429): Connect the designated High (HI) and Low (LO) ARINC output wires to the corresponding inputs on your HSI or CDI.
3. Autopilot: Connect the appropriate ARINC or NMEA output wires to the flight director/autopilot coupler interface.
4. Audio Panel (Muting): Connect the provided audio inhibit wire to the audio panel to mute non-essential audio during GPS annunciations.
5. Moving Map/External Display (RS-232): Connect the serial output TX/RX/GND wires to a compatible display unit.

Tip: Refer to the aircraft-specific wiring diagram and the Garmin GPS-155 Interface Guide for detailed pinouts and signal specifications. Ensure all connections are secure and insulated.

Operational Procedures

Basic steps for IFR or VFR navigation.

1. Preflight: Power on. Check satellite acquisition (SAT page). Verify RAIM prediction for intended flight time/route (AUX > RAIM PREDICT). Confirm database is current and valid.
2. Direct-To Navigation: Press the D key. Enter the destination airport or waypoint identifier using the knob. Press ENT to activate navigation. Observe CDI/HSI movement.
3. Flight Plan Creation: From the AUX page, select FLIGHT PLAN. Use the knob to add waypoints from the database or user list. Activate the flight plan.
4. Approach Activation: While in terminal airspace, select the desired approach from the database (AUX > APPR). Load and activate the approach. CDI scale will automatically change to approach sensitivity (±0.3 nm).
5. Suspend/Resume: Use the SUSPEND function to hold current guidance (e.g., during vectors). Press D or reactivate flight plan to resume.
6. Nearest Airports: In an emergency, use the NRST page to quickly locate the closest suitable airports with bearing and distance.

WARNING! Pilot is responsible for verifying all procedures, waypoints, and clearances. GPS is a supplemental navigation aid; always have a backup means of navigation. Do not use GPS for primary guidance if integrity (RAIM) is unavailable or lost.

Database Management

The unit requires current Jeppesen NavData for IFR operations.

Updating: Purchase updated Jeppesen data cards on a 28-day cycle. Power off the unit. Insert the new card into the slot on the front panel. Power on. The unit will automatically load the new database. Verify the effective date range on the AUX > DATABASE status page.

Validity: The database is required to be current for IFR operations. An expired database may be used for VFR navigation, but all data must be verified by the pilot.

Maintenance & Inspection

Regular inspection per aircraft maintenance schedule.

Daily/Preflight: Visual inspection of unit, antenna, and connectors for security and damage. Verify normal power-up and self-test.

Periodic (Annual/100hr): Check antenna bonding resistance (should be < 2.5 milliohms). Inspect cable integrity and security. Perform a full operational check using the built-in test functions (AUX > SYSTEM TEST). Verify interface outputs with appropriate test equipment if available.

Cleaning: Use a soft, dry cloth to clean the display and bezel. Do not use liquid cleaners or aerosols.

CAUTION! Maintenance must be performed by appropriately rated personnel. Disconnect aircraft power before performing any internal inspections or tests not described in this manual.

Regulatory & Compliance

This unit is approved under TSO-C129a1, Class A1. Installation must be documented in the aircraft maintenance records and may require an FAA Form 337. Compliance with Advisory Circular AC 20-138(), AC 20-130A, and AC 23.1311-1C is required for airworthiness. The use of GPS for IFR en route, terminal, and approach operations is subject to the limitations and procedures outlined in the FAA's Aeronautical Information Manual (AIM) and applicable pilot operating handbooks. Garmin is a registered trademark of Garmin Ltd. Jeppesen is a registered trademark of Jeppesen Sanderson, Inc.

Troubleshooting

Reset: A full system reset can be performed via AUX > SYSTEM > MASTER RESET (caution: erases all user waypoints and settings).

Technical Support: Contact Garmin Aviation Product Support or refer to the Garmin GPS-155 Maintenance Manual for advanced troubleshooting. For warranty service, contact an authorized Garmin dealer.