GNC 255A/255B Pilot’s Guide
© 2012 Garmin Ltd. or its subsidiaries. All rights reserved. This manual reflects the operation of System Software version 2.00, or later. Some differences in operation may be observed when comparing the information in this manual to later software versions. Garmin International, Inc., 1200 East 151st Street, Olathe, KS 66062, U.S.A. Tel: 913/397.8200 Fax: 913/397.8282 Garmin AT, Inc., 2345 Turner Road SE, Salem, OR 97302, U.S.A. Tel: 503/391.3411 Fax 503/364.2138 Garmin (Europe) Ltd.
LIMITED WARRANTY All Garmin avionics products are warranted to be free from defects in materials or workmanship for: two years from the date of purchase for new Remote-Mount and Panel-Mount products; one year from the date of purchase for new portable products and any purchased newly-overhauled products; six months for newly-overhauled products exchanged through a Garmin Authorized Service Center; and 90 days for factory repaired or newly-overhauled products exchanged at Garmin in lieu of repair.
WARNING: For safety reasons, GNC 255 operational procedures must be learned on the ground. CAUTION: The Garmin GNC 255 does not contain any user-serviceable parts. Repairs should only be made by an authorized Garmin service center. Unauthorized repairs or modifications could void both the warranty and the pilot’s authority to operate this device under FAA/FCC regulations.
NOTE: Canadian installations: In accordance with Canadian Radio Specifications Standard 102 (RSS 102), RF field strength exposure to persons from an antenna connected to this device should be limited to 60 V/m for controlled environment and 28 V/m for uncontrolled environment. 190-01182-01 Rev.
NOTE: This device complies with Part 15 of the FCC limits for Class B digital devices. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. Furthermore, there is no guarantee that interference will not occur in a particular installation.
Product Registration and Support Help us better support you by completing your online registration today! Have the serial number of your product handy and connect to the Garmin web site (www.garmin.com or https://fly.garmin.com/fly-garmin). Look for the Product Registration link on the Home page. Also, be sure to record your serial number in the space provided. If you have any questions, the Garmin Product Support department may be reached Monday through Friday, 7:00 AM to 7:00 PM Central Time.
Record of Revisions Part Number Revision Date Description 190-01182-01 A 11/19/12 Initial release vi Garmin GNC 255A/255B Pilot’s Guide 190-01182-01 Rev.
Contents Product Registration and Support.......................................................................v 1 Getting Started.....................................................................................1-1 1.1 Product Description............................................................................... 1-1 1.2 Pilot Controls........................................................................................ 1-2 1.2.1 Power/Com Volume/Squelch Knob................................
3 Functions...............................................................................................3-1 3.1 Functions Description............................................................................ 3-1 3.2 Com Frequencies.................................................................................. 3-2 3.2.1 Recent Com Frequencies......................................................... 3-2 3.2.2 Com User Frequencies............................................................ 3-3 3.2.
3.6.3 Viewing Timers in the Com Display........................................ 3-24 4 Appendix...............................................................................................4-1 4.1 Troubleshooting.................................................................................... 4-1 4.2 Updating the Frequency Database......................................................... 4-3 4.2.1 Downloading the Frequency Database.................................... 4-3 4.2.
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1 GETTING STARTED 1.1 Product Description Combining a powerful VHF communications transceiver with 200 channel VOR, Localizer and Glideslope receivers, the GNC 255 provides a full-functioned navigation and communications solution in a small footprint at a very affordable price.
1.2 Pilot Controls The GNC 255 controls have been designed to simplify operation of the system and minimize workload and the time required to access sophisticated functionality. Controls are comprised of dual concentric knobs for frequency tuning, Com volume/squelch knob, Nav volume/ID knob, and bezel keys. 1.2.1 Power/Com Volume/Squelch Knob The Power/Com Volume/Squelch knob located in the top left corner of the bezel controls audio volume for the Com radio.
1.2.3 Tuning LARGE/SMALL Concentric (Cursor) Knobs The LARGE right and SMALL right knobs are used for tuning frequencies and data entry. LARGE, Outer Knob SMALL, Inner Knob 1.2.4 FLIP/FLOP Key 1.2.5 Press and release the FLIP/FLOP key to switch between the active (left-most) and standby (right-most) frequency. Switching between Com frequencies is disabled while you are transmitting. C/N (Com/Nav) Key Press the C/N key to select the Com or Nav (VLOC) radio mode. 1.2.6 OBS Key 1.2.
1.2.10 FUNC (Function) Key The FUNC (Function) key accesses function categories for the following: the Com Radio, Nav Radio, ICS Configuration, System Configuration, and Timer. Pressing the FUNC key once displays the Function mode. Pressing the FUNC key a second time exits the Function mode. 1.2.11 MON (Monitor) Key The MON (Monitor) key will engage the monitor function where the Standby frequency may be monitored while still listening to the Active frequency. 1.
2 BASIC OPERATION 2.1 Power On Turn the GNC 255 on by either turning the Power/Com Volume/ Squelch knob clockwise to turn the power on or, if installed, turning on the master switch that powers the radios. 2.2 Com Radio 2.2.1 Selecting a Com Frequency New frequencies are first selected as a Standby frequency and then toggled to the Active side with the FLIP/FLOP key.
2.2.2 Monitoring the Standby Com Channel The Frequency Monitoring function allows you to monitor the Standby frequency for activity, while listening to the Active frequency. Press the MON key in the Com function to listen to the standby frequency. A small “MN” will replace the “STB” to the left of the Standby frequency.
5. Turn the LARGE knob to select the waypoint Type. 6. Turn the SMALL knob to select the Type from the list.
2.2.4 Com Database Look-Up 1. Press the CURSOR knob from the Com display to activate the database look-up function. Identifier Field Active for Selection Turn SMALL Knob To Select Character Turn LARGE Knob To Move Cursor Figure 2-5 Database Identifier Active for Selection 2. Turn the SMALL knob to select characters and turn the LARGE knob to move the cursor. Selected Identifier Figure 2-6 Database Identifier Selection 3. After selecting the desired characters, press ENT.
2.2.6 Emergency Channel 1. Press and hold the FLIP/FLOP key or the Com Remote Transfer (COM RMT XFR) key for approximately two seconds. Figure 2-9 Emergency Channel 2. The Emergency Channel will be inserted into the Active Frequency position and the previous Active Frequency will become the Standby Frequency.
2.3 Nav Radio 2.3.1 Selecting a Nav Frequency The selection of Nav frequencies is the same as for the Com frequencies. 1. Press the C/N key to reach the Nav radio function. The NAV annunciator on the top line of the display will show. 2. Turn the LARGE knob to change the values in one MHz increments. The MHz selection range is between 108 and 117 MHz in one MHz steps. 3. Turn the SMALL knob to change the values in 50 kHz increments.
5. Turn the LARGE knob to select the waypoint Type. 6. Turn the SMALL knob to select characters. 7. Turn the LARGE knob to move the cursor. Figure 2-12 Nav User Frequency Type Selection 8. After selecting the desired characters, press ENT. Frequency Type Symbol VOR DME LOC ILS 01-36 Blank Description Very High Frequency Omni-Directional Range Distance Measuring Equipment Localizer Instrument Landing System Runway Heading None Table 2-2 - Nav Frequency Type List 2.3.
2.4 OBS Mode If your system is configured with an external CDI/HSI, the OBS radial of your remote display will be decoded and displayed on the screen of the GNC 255. NOTE: The Identifier is the decoded Nav Identifier from the Morse code broadcast by the station. 1. Press the OBS key to see the current OBS setting and graphic CDI. 2. Use the LARGE and SMALL knobs to change the displayed OBS values. The GNC 255 graphic CDI is shown as a graph of five dots right or left of the triangle icon.
2.5 Distance/Speed/Time (DST) Display When the GNC 255 has received data from an external device, such as a GPS receiver or DME sensor through the serial port, DST data will be available. If you are not connected to an external sensor, you will not see this display. If DST data is not shown, pressing the T/F key will show DST data in the lower part of the display.
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3 FUNCTIONS The Functions section allows provides information about Com Frequencies, Nav Frequencies, Internal Communications System (ICS) Configuration, System Configuration (SYS), and Timers (TMR). 3.
1. Press the FUNC key to access the Functions. 2. Turn the LARGE knob to select the COM, NAV, ICS, or SYS functions. 3. Turn the SMALL knob to view the choices in each function. 4. Press the ENT key to access the function. 5. Press the FUNC key again to exit Functions. 3.
3.2.2 Com User Frequencies Fifteen Com User Frequencies can be saved with an assigned waypoint (WPT) identifier and Type. NOTE: When switching from 8.33 kHz to 25 kHz mode, any 8.33 kHzspecific user frequencies will be deleted from the user frequency list. This only affects the user frequencies within the 8.33 kHz spectrum. 3.2.2.1 Viewing the Com User Frequency 1. Press FUNC to access the Functions. Turn the LARGE knob to select the Com Frequency Function.
2. Press the ENT key to confirm deletion of the displayed frequency. 3.2.2.3 Editing a Com User Frequency 1. Press FUNC. Turn the LARGE knob to reach the Com functions and then turn the SMALL knob to select the Com User Frequencies. Press ENT. Select User Freqs Figure 3-5 Com User Frequency Function 2. Press the CRSR (SMALL knob) to start editing the Com User frequency.
3.2.3 Com Database Frequencies The GNC 255 contains a large database of Com frequencies that may be recalled by identifier. Turn SMALL Knob To Select Character Turn LARGE Knob To Move Cursor Figure 3-9 Com Database Frequencies 1. Press FUNC to access the Functions. With the Com Frequency Function highlighted, turn the SMALL knob to view the Com Database function. Then, press ENT. 2. Turn the SMALL knob to select the desired character. 3.
3.2.4 Com Nearest Airports (APT) The GNC 255 will report the 25 nearest Airports (APT), when interfaced with an appropriate GPS receiver. Turn SMALL Knob To Scroll Through Available Airports Figure 3-11 Com Nearest APT Frequencies 3-6 1. Press FUNC to access the Functions. With the Com Frequency Function highlighted, turn the SMALL knob to view the Com Nearest APT function. Then, press ENT. 2. Turn the SMALL knob to display the available airports.
3.2.5 Com Nearest Area Control Center (ACC) Frequencies The GNC 255, when interfaced with an appropriate GPS receiver, will report the 25 nearest Area Control Center (ACC) frequencies. ACCs are also known as Air Route Traffic Control Centers (ARTCC). Turn SMALL Knob To Scroll Through Available Frequencies Figure 3-12 Com Nearest ACC Frequencies 1. Press FUNC to access the Functions. With the Com Frequency Function highlighted, turn the SMALL knob to view the Com Nearest ACC function. Then, press ENT.
3.2.6 Com Nearest Flight Service Station (FSS) Frequencies The GNC 255, when interfaced with an appropriate GPS receiver, will report the 25 nearest Flight Service Station (FSS) frequencies. Turn SMALL Knob To Scroll Through Available Frequencies Figure 3-13 Com Nearest FSS Frequencies 3-8 1. Press FUNC to access the Functions. With the Com Frequency Function highlighted, turn the SMALL knob to view the Com Nearest FSS function. Then, press ENT. 2.
3.2.7 Com Nearest Weather (WX) Frequencies The GNC 255, when interfaced with an appropriate GPS receiver, will report the 25 nearest Weather (WX) frequencies. Turn SMALL Knob To Scroll Through Available Frequencies Figure 3-14 Com Nearest Weather Frequencies 1. Press FUNC to access the Functions. With the Com Frequency Function highlighted, turn the SMALL knob to view the Com Nearest Weather function. Then, press ENT. 2. Turn the SMALL knob to display the available Weather frequencies. 3.
3.3 Nav Frequencies The Nav Frequencies category in the Functions section contains remotely acquired frequencies (Remote), recently used frequencies (Recent), user-defined frequencies (User), and a database of all frequencies provided in the standard default memory (Database). 3.3.1 Recent Nav Frequencies The last 20 Nav frequencies used are kept in the list of Recent Nav Frequencies and can be accessed in this function. 1. Press FUNC to access the Functions.
3.3.2 Nav User Frequencies Up to 15 Nav User Frequencies can be saved with an assigned waypoint (WPT) identifier and Type. 3.3.2.1 Viewing the Nav User Frequency 1. Press FUNC to access the Functions. Turn the LARGE knob to select the Nav Frequency List Function. Turn the SMALL knob to view the Nav User Frequency function. Then, press ENT. Press ENT Key To Set Selected Freq As Standby Position In List. Turn SMALL Knob To Select Entry.
3.3.2.3 Editing a Nav User Frequency 1. Press FUNC. Turn the LARGE knob to reach the Nav functions and then turn the SMALL knob to select the Nav User Frequencies. Press ENT. Figure 3-18 Nav User Frequency Function 2. Turn the SMALL knob to select the desired Nav User frequency and then press ENT. Press the Cursor knob to enable editing. The frequency MHz value will be selected. Turn the SMALL knob to select the MHz frequency value.
3.3.3 Nav Database Frequencies The GNC 255 contains a large database of Nav frequencies that may be recalled by identifier. 1. Press FUNC to access the Functions. With the Nav Frequency Function highlighted, turn the SMALL knob to view the Nav Database function. Then, press ENT. 2. Turn the LARGE knob to move the cursor to highlight a character. 3. Turn the SMALL knob to select the desired character.
Duplicate Identifiers 1. When duplicate identifiers are found, press ENT. Duplicate Identifiers Found Press the ENT Key to Save the Displayed Value Press the CLR Key To Return to the Previous Menu Figure 3-23 Selected Nav Database Frequency 2. Turn the SMALL knob to select the desired identifier and then press ENT and continue as described above. Figure 3-24 Selected Ident from Nav Database 3. Set the selected identifier as the standby or active frequency.
2. Turn the SMALL knob to display the available VORs. 3. Press the ENT key to accept the displayed VOR and set it as the Standby frequency. Or, press the CLR key to return to the Functions display. 3.4 ICS Configuration The Internal Communications System (ICS) Configuration allows you to adjust the intercom, set the Nav/Aux volume, turn the Intercom On/Off, and turn the intercom speaker On/Off. 3.4.
3.4.2 Aux Audio The Aux function allows you to turn Aux Audio On/Off and set the volume value. 1. Press FUNC to access the Functions. Turn the LARGE knob to select the ICS Function. Turn the SMALL knob to view the Aux Volume function. Then, press the ENT key. Figure 3-29 Select the Aux Audio Function 2. Turn the SMALL knob to turn the Aux Audio On or Off. 3. Turn the LARGE knob to select the Aux Volume. Turn the SMALL knob to set the value. Then, press the ENT key.
3.4.3 Intercom On/Off The Intercom On/Off function toggles intercom on and off. The intercom can also be toggled on/off with a remote switch, if installed. The Intercom On/ Off function must be set to On to make the Adjust Intercom function available. 1. Press FUNC to access the Functions. Turn the LARGE knob to select the ICS Function. Turn the SMALL knob to view the Intercom On/Off function. Then, press the ENT key.
3.5 System Configuration The System Configuration function will show the Software Version, Database Info, and Serial Number as well as, allowing you to set values for the Com spacing, Display Brightness, and Display Contrast, and use the Load Database feature to update databases. 3.5.1 Com Spacing Com spacing may be selected between 8.33 kHz and 25 kHz to allow for regional requirements. NOTE: When switching from 8.33 kHz to 25 kHz mode, any 8.
3.5.2 Display Brightness As it arrives from the factory, the GNC 255 automatically adjusts its display brightness for the current lighting conditions. A small sensor on the display is used for this function. A manual adjustment is available for controlling the brightness level of the display as an offset from the “normal” or zero position. The limits of the adjustment range are: -10 (Low Display Intensity) and 100 (High Display Intensity).
3.5.3 Display Contrast The Display Contrast has a range from -50 (Low Display Contrast) and 50 (High Display Contrast) with 0 as the default. The range can be adjusted by using the SMALL knob to adjust the value. 1. Press FUNC to access the Functions. Turn the LARGE knob to select the SYS Function. Turn the SMALL knob to view the Display Contrast function. Then, press the ENT key.
3.5.5 Load Database The GNC 255 has a USB connector to allow for easily updating the system databases. NOTE: Garmin recommends the use of a USB 2.0 compatible USB flash drive for updating the database. 1. Insert the supplied cable into the USB port on the top right corner of the GNC 255. 2. Insert the USB memory device into the other end of the cable. USB Port USB Cable USB Memory Device Figure 3-37 USB Update Progress 3. Press FUNC to access the Functions.
5. Wait until the updating process is complete and then remove the memory device and cable. The unit will reset automatically once the database is updated. 6. Verify the correct frequency database is loaded after power-up. 3.5.6 Software Version The software versions of the GNC 255 unit are displayed. This information is useful when contacting Customer Support. 1. Press FUNC to access the Functions. Turn the LARGE knob to select the SYS Function.
3.6 Timers The GNC 255 has both Count Up and Count Down timers, which may operate simultaneously and are shown in the lower right of the Com/Nav displays. The countdown timer always takes precedence if it is running. 3.6.1 Setting Up the Count Down Timer 1. Press FUNC to access the Functions. Turn the LARGE knob to select the Timer (TMR) function. Turn the SMALL knob to select either the Count Down Timer function. Now, press the ENT key.
3.6.2 Setting Up the Count Up Timer 1. Press FUNC to access the Functions. Turn the LARGE knob to select the Timer (TMR) function. Turn the SMALL knob to select the Count Up Timer function. Now, press the ENT key. Select Count Up Timer Figure 3-44 Select the Count Up Timer Function 2. Press the ENT key to Start or Stop the timer. Press the CLR key to reset the timer to 0:00.
When the Count Down Timer reaches 0:00, it will continue counting as a Count Up value. The Count Down Timer that is counting up will be highlighted. A Count Up Timer will continue counting separately. Count Down Timer Value Highlighted When Counting Up Figure 3-48 Count Down Timer Value Now Counting Up 190-01182-01 Rev.
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4 APPENDIX 4.1 Troubleshooting If efforts to resolve the problem fail, contact your dealer or the factory for technical assistance. The Garmin customer service staff will gladly assist you. Please have the following information ready: • System configuration (products, antennas, mounting locations, etc.) • Model No., part number, and serial number • Software versions • Description of the problem • Efforts made to isolate/solve the problem Garmin International, Inc.
Problem GNC 255 does not power on Possible Cause No power to the GNC 255 Faulty electrical wiring or connection No Nav audio Nav audio in Com GNC 255 does not transmit Intercom doesn’t function Can’t change active frequency OBS readout displays “---” 4-2 Output disabled or set to a low level Mixed with Com feature No power to Com Mic key connection It can be enabled or disabled via a remote mounted switch or via the menu. No voice activation, or if must talk too loud Com Radio not communicating.
Problem Display shows “Incorrect Calibration Checksum” at start-up Possible Cause Corrupted system calibration parameters Action Contact factory Table 4-1 Troubleshooting 4.2 Updating the Frequency Database The GNC 255 uses a standard USB memory device to load the frequency database into the GNC 255. The memory device is not provided by Garmin. The Frequency database is stored internally and the USB memory device is only used to transfer the database into the unit.
4.3 Messages When a Message has been issued by the unit, the Message will be shown on the display. After viewing the messages, touch the ENT key to acknowledge the message and return to the previously viewed page. An acknowledged message will not be redisplayed even if the condition persists. Messages provide an aid to troubleshooting system operation. Message Press ENT To Acknowledge Figure 4-1 Message - Com PTT Key Stuck Message Description Action COM RADIO Com radio needs service.
Message Description COOLING FAN - The GTN cooling fan is The cooling fan has powered, but it is not turning at the desired failed. RPM. DISPLAY Display board needs service. GLIDESLOPE Glideslope receiver needs service. The display board is indicating that it needs service. The glideslope board is indicating that it needs service. The glideslope board may continue to function. The glideslope board GLIDESLOPE Glideslope receiver is not communicating property with the has failed. system.
Message REMOTE KEY STUCK Com remote transfer key is stuck. REMOTE KEY STUCK Com remote frequency increment key is stuck. REMOTE KEY STUCK Com remote frequency decrement key is stuck. 4-6 Description Action The remote com transfer (COM RMT XFR) key/switch has been in pressed position for at least 30 seconds. This input will now be ignored. This input is not available in all installations. The remote com frequency increment (COM CHAN UP) key/ switch has been in pressed position for at least 30 seconds.
Message REMOTE KEY STUCK Nav remote transfer key is stuck. VLOC RECEIVER Navigation receiver needs service. VLOC RECEIVER Navigation receiver has failed. Description Action The remote nav transfer (NAV RMT XFR) key/ switch has been in pressed position for at least 30 seconds. This input will now be ignored. This input is not available in all installations. The nav radio is reporting that it needs service. The nav radio may continue to function.
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INDEX FSS 3-8 Functions 1-4, 3-1 A G Appendix 4-1 Getting started 1-1 B I Basic operation 2-1 Brightness 3-19 ICS 3-15 ID 1-2 Intercom 3-17 C Cautions ii, 2-6 Clear 1-3 Com database frequencies 3-5, 3-6, 3-7, 3-8, 3-9 Com frequencies 3-2 Com PTT 3-18 Com radio 2-1 Com;Select frequency 2-1 Com spacing 3-18 Com user frequencies 3-3 Com volume 1-2 Contrast 3-20 Controls 1-2 Cursor 1-3 Customer service i, 4-1 K Knobs 1-3 L Locking screw 1-1 M Menus 1-3 Message 4-4 Monitoring 1-4, 2-2 Morse code 1-1
R Recent com frequencies 3-2 Recent nav frequencies 3-10 Record of Revisions vi Registration v Remote frequency control 2-5 Reverse look-up 2-4 Revisions vi S Saving a com channel 2-2 Saving a nav channel 2-6 Serial Number 3-22 Software version 3-22 Speaker On/Off 3-17 Squelch 1-2 Stuck mic 2-5 Support v System configuration 3-18 T Timers 3-23 To-From 1-3 Troubleshooting 4-1, 4-4 U Updating frequency database 4-3 USB 1-4, 3-21 User frequencies 3-3, 3-11 V Volume 1-2 W Warranty i Index-2 Garmin GNC 25
© 2012 GARMIN Corporation GARMIN International, Inc. 1200 East 151st Street, Olathe, Kansas 66062, U.S.A. Tel. 913/397.8200 or 800/800.1020 Fax 913/397.8282 Garmin AT, Inc. 2345 Turner Rd., S.E., Salem, Oregon 97302, U.S.A. Tel. 503/581.8101 or 800/525.6726 Fax. 503/364.2138 Garmin (Europe) Ltd. Liberty House, Bulls Copse Road, Hounsdown Business Park, Southampton, SO40 9RB, U.K. Tel. +44 (0) 870 850 1243 Fax +44 (0) 238 052 4004 GARMIN Corporation No. 68, Zhangshu 2nd Road, Xizhi Dist.
