OBS Mode
Continuous
Bearing Pointer
Garmin G1000 Setup for NDB Approaches
Proper configuration of your Garmin G1000 is essential before initiating an NDB approach. This preparatory phase ensures accuracy and adherence to published procedure requirements, particularly when operating in airspace where specific configurations are required.
Initial G1000 Configuration Steps
| Configuration Item | Setting | Purpose | Critical Notes |
|---|---|---|---|
| Altimeter Setting | Hectopascals (hPa) | European standard compliance | Required for EASA operations |
| Communication Frequencies | 8.33 kHz channel spacing | European airspace requirement | Primary and standby frequencies |
| Bearing Pointers | ADF on BRG1, GPS on BRG2 | NDB tracking and situational awareness | Essential for navaid monitoring |
| NDB Frequency | 850 kHz (Cranfield) | ADF receiver tuning | Manual input required |
| Flight Plan Entry | EGTC as waypoint | GPS-based navigation reference | OBS mode activated at this fix |
Step-by-Step G1000 Configuration
The following sequence covers the complete G1000 setup workflow for flying an NDB approach with GPS overlay. Each step must be completed in order before entering the approach segment.
Enter the NDB frequency into the ADF receiver using the G1000's audio panel or ADF tuning page. For the Cranfield NDB, this is 850 kHz. Verify the identifier is receiving correctly — the ADF needle should swing to point toward the beacon once the frequency is active and the station is in range.
Do not proceed with the approach until you confirm the ADF is receiving a valid ident. An ADF needle that is erratic or pointing away from the expected bearing indicates a station or tuning problem.
Use the FMS knob to navigate to the Procedures page and select the NDB approach for your destination runway. If the approach is in the G1000 database, load it normally. If it is not in the database, manually enter the airport waypoint and use OBS mode to set the inbound course on the CDI.
When the approach is loaded and you are cleared for the approach, activate OBS mode by pressing the OBS softkey. This suspends automatic waypoint sequencing and allows you to manually set and hold a course, turning the GPS CDI into a course-based needle similar to a VOR indicator.
On the G1000 MFD or HSI page, configure BRG1 or BRG2 to display ADF. This adds the RMI-style bearing pointer to the HSI, showing the relative bearing to the NDB at all times. This pointer is your primary monitoring tool for the NDB throughout the approach.
With ADF on one bearing pointer and GPS on the other, you have both the primary navaid bearing and the GPS course reference visible simultaneously on the HSI. Cross-checking both during the approach is the key to maintaining situational awareness when the two sources may show slightly different indications.
From the Final Approach Fix inbound, fly GPS CDI for lateral guidance — the CDI reflects your OBS-set course and provides course deviation information to the runway extended centerline. At the same time, monitor the NDB bearing pointer continuously as your primary navaid cross-check.
The bearing pointer should point progressively more ahead of the aircraft as you track inbound. Any unexpected swing or erratic movement of the ADF needle should prompt you to cross-check your position and consider the missed approach if approach continuity is in question. Never abandon NDB monitoring in favor of GPS alone past the FAF.
If the required visual references are not established at the Minimum Descent Altitude, execute the published missed approach procedure immediately. Apply go-around power, establish a positive rate of climb, and follow the published missed approach course from the NDB minimums.
Transition from heading mode to OBS mode as needed to manage the missed approach holding entry efficiently. If the missed approach involves a hold over the NDB, use the bearing pointer to confirm station passage and time the entry accordingly.
Executing the NDB Approach with OBS at Cranfield (EGTC)
The execution phase requires methodical progression through each segment of the approach. OBS mode transforms your GPS into a course-based navigation source, providing lateral deviation guidance even when the approach is not natively supported in the G1000 database.
Approach Procedure Phases
Phase 1: Initial Approach
Waypoint Activation: Once the NDB frequency is active, navigate directly to the EGTC waypoint using the G1000's direct-to function. This establishes your initial reference point for the approach.
Outbound Course Establishment: Upon reaching the NDB, maintain your initial approach altitude (typically 2500 feet) and activate OBS mode. Rotate the course selector to the outbound course (219 degrees from EGTC). This configuration lets you treat the GPS fix like a VOR radial and provides familiar course deviation cues for the outbound segment.
Phase 2: Outbound Segment
Tracking Outbound: Monitor both the bearing pointer (ADF needle) and the GPS distance readout. Fly outbound on the selected course until reaching the designated distance — typically 9 nautical miles DME from EGTC for the Cranfield approach.
| Phase | Distance from EGTC | Altitude | Course | Action Required |
|---|---|---|---|---|
| Initial Approach | At NDB | 2500 ft | 219 deg | Outbound tracking |
| Outbound Limit | 9.0 NM | 2500 ft | 219 deg | Begin inbound turn |
| Final Approach Fix | 6.6 NM | 2500 ft | 032 deg | Begin descent |
| Minimum Descent Altitude | Variable | 730 ft | 032 deg | Visual reference required |
Phase 3: Inbound Segment
Inbound Turn and Course Set: At the outbound limit, execute a left turn to intercept the inbound course (032 degrees for Runway 03 at Cranfield). Adjust the OBS course selector to this inbound heading. The CDI now provides lateral guidance for the final approach segment.
Descent and Configuration: Identify the Final Approach Fix (FAF) at 6.6 nautical miles DME from EGTC. Begin descent from 2500 feet to the Minimum Descent Altitude of 730 feet. Configure the aircraft with appropriate flaps and manage airspeed in the 95–100 knot range. Set the MDA in the altimeter pre-select for enhanced situational awareness.
Phase 4: Final Approach
Final Approach Segment: Continuously cross-check the NDB bearing pointer and GPS CDI for lateral guidance. Make heading corrections as needed to maintain the inbound course. Reference the published approach chart to verify compliance with all altitude and distance restrictions.
Missed Approach Procedure: If visual references are not established at the MDA, initiate the published missed approach. Climb to a safe altitude and execute the specified turn or hold, typically returning to the NDB for holding entry. Use heading mode initially, then transition to OBS mode to manage the holding entry.
Essential Tips for OBS and NDB Approaches
Set OBS Before the FAF
Verify ADF Ident Continuously
Cross-Check Distance Against Altitude
Brief the Missed Approach Thoroughly
Technical Specifications and Performance
| Parameter | Value | Units | Notes |
|---|---|---|---|
| NDB Frequency | 850 | kHz | Non-directional beacon |
| Runway | 03/21 | - | Primary approach runway |
| Minimum Descent Altitude | 730 | feet | QNH setting required |
| Final Approach Course | 032 | degrees | Magnetic heading |
| Approach Speed | 95–100 | knots | Target airspeed range |
| Visibility Minimum | 1500 | meters | Required for approach |
Conclusion
Flying an NDB approach with GPS overlay on the Garmin G1000 combines the reliability of GPS lateral guidance with the procedural rigor of primary navaid monitoring. Proficiency requires more than knowing where the OBS button is — it requires understanding why each configuration step matters and what to do when the primary navaid behaves unexpectedly.
The combination of OBS mode, bearing pointer configuration, and continuous ADF monitoring represents a complete workflow that instrument pilots can apply to any NDB approach, not just the Cranfield procedure. These fundamentals transfer directly to other non-precision approaches where GPS overlay is used in lieu of a database-loaded procedure.
Regular practice in a simulator is the most efficient way to build fluency with this workflow. Repeating the configuration sequence — tuning the NDB, loading the approach, setting OBS, configuring bearing pointers, and monitoring through the FAF — builds the procedural memory that makes the actual approach manageable in IMC.
Frequently Asked Questions
NDB approaches are often not stored as loadable procedures in the G1000 database, particularly at smaller or international airports. OBS mode suspends the GPS autopilot's automatic waypoint sequencing and lets you manually set a course on the CDI — essentially turning the GPS into a course-based needle similar to a VOR indicator. Without OBS mode, the GPS would sequence to the next waypoint on its own rather than holding the inbound course you need for the approach.
The bearing pointer (configured to ADF) shows the relative bearing to the NDB beacon — it always points directly at the station, like a traditional RMI needle. The CDI, when OBS mode is active, shows course deviation from the inbound track you have dialed in. During the approach you use the CDI for lateral guidance to stay on centerline, and the bearing pointer to monitor the primary navaid. They complement each other: the CDI tells you where you are relative to the course, and the bearing pointer confirms the actual position of the NDB.
No. The G1000 GPS provides supplemental lateral guidance via OBS mode, but the ADF remains the primary navaid for the approach. You are required to monitor the ADF bearing pointer continuously from the FAF to the missed approach point. If the ADF signal becomes unreliable or the ident cannot be confirmed, the GPS alone is not a compliant substitute — you would need to execute the missed approach. Think of GPS overlay as a precision aid, not a replacement.
From the Final Approach Fix inbound, monitor the GPS CDI for lateral course deviation, the ADF bearing pointer for continuous NDB confirmation, your altitude against the published Minimum Descent Altitude, and GPS distance to track position along the final segment. The bearing pointer should point progressively more ahead of the aircraft as you track inbound to the beacon. Any erratic movement of the ADF needle is a signal to cross-check your position and consider the missed approach if something does not add up.
The underlying concept applies to most panel-mounted GPS navigators that support OBS mode, including the Garmin GTN series and older GNS 430/530 units. The specific button labels and menu paths differ, but the principle is the same: activate OBS mode to suspend automatic sequencing, dial in the inbound course, and use the CDI for lateral guidance while monitoring the primary navaid separately. Always verify how OBS mode behaves on the specific unit you are flying before using this technique in actual instrument conditions.
Practice NDB Approaches in the Simulator
Build OBS mode fluency and NDB approach proficiency with airline pilot instruction in our G1000 NXi simulator.
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