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Setting the correct course for an airport is a critical aspect of flying, and it involves aligning the aircraft with the runway during the approach. While newer Boeing models like the 777 do not have the Course mode, the 737 features an autopilot mode where pilots can set a course instead of a heading. This allows the aircraft to fly along a specified line towards a selected VOR frequency and direction. This guide will explain how to set the airport course in a Boeing aircraft, specifically focusing on the 737 model, covering both manual and autopilot procedures.
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What You'll Learn
Using autopilot to set the course
The autopilot in Boeing aircraft can be used to set the course and fly the aircraft. To engage the autopilot, certain conditions must be met, including:
- Airspeed is above stall speed and below maximum speed.
- Pitch angle is between 25° and -15° and bank angle is less than 45°.
- Flight control inputs are neutral and the aircraft is trimmed out.
- Aircraft altitude is at least 100 feet above the ground after takeoff or above 400 feet prior to landing.
The autopilot can be used to set the course in different ways, depending on the aircraft type and the approach being used. Here are some common methods:
Using the Flight Mode Annunciator (FMA):
The FMA is an essential instrument when using the autopilot. It displays the current autopilot status and activated modes. To set the course, the pilot can use the knobs to adjust the speed, altitude, and heading. The heading knob has a button that can be pushed to activate the heading mode.
Autopilot "Course" Mode:
Some Boeing aircraft, like the 737, have an autopilot "Course" mode. Instead of setting a specific heading, the pilot can set a "course" by telling the aircraft to fly along a particular radial out of a VOR, which is selected on the NAV1 radio and the Course knob. However, newer Boeings like the 777 and 747 do not have this feature and use the FMC to select waypoints.
ILS (Instrument Landing System) Approach:
During an ILS approach, the pilot tunes the ILS frequency of the runway they plan to land on and dials it into the active portion of the Nav radios. The course dials are then set to match the heading of the runway. By selecting APR mode on the EFIS selector, the pilot can ensure alignment with the localizer (LOC) and glideslope (GS). Once the autopilot captures the localizer, the aircraft can descend and follow the GS beam.
Area Navigation Approaches (RNV-Approaches):
RNV-Approaches use GPS signals and radio-navaid triangulation to compute the aircraft's position accurately. While this accuracy is not sufficient for automatic landing, it allows the autopilot to steer the aircraft along the planned route. The pilot selects the RNV approach in the navigation menu or via the MCDU/MFD in the cockpit and engages the NAV mode.
Auto-Tuning:
When a route is programmed, auto-tuning is enabled. The pilot can push the APP button to arm the localizer and glide-slope or use the LOC, LOC/FAC, or VOR/LOC buttons to arm only the localizer capture. As the localizer moves towards the center, the autopilot turns to the selected course and captures the localizer.
It is important to note that the autopilot compensates for wind drift in certain modes, and pilots can always manually intervene and take control if needed.
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Tuning the frequency of the navaid
Understanding Navaids
Navaids, or navigational aids, operate within specific frequency bands, such as the VHF (Very High Frequency) band for VOR (VHF Omnidirectional Range) systems. These frequencies are essential for aircraft navigation and require precise tuning.
Tuning Procedures:
When tuning the frequency of a navaid, follow these steps:
- Identify the Navaid: Determine which navaid you need to tune. This could be a VOR, ILS (Instrument Landing System), or another system.
- Determine the Frequency: Find the correct frequency for the navaid you intend to use. This information can be obtained from navigation charts or databases.
- Tune the Radio: Adjust the settings on your aircraft's navigation radio to match the desired navaid frequency.
- Set the Course: After tuning to the correct frequency, use the course selector to set the final approach course. This ensures that your autopilot and manual displays function correctly.
- Verify Alignment: For ILS approaches, select APR mode on the EFIS selector to verify alignment with the localizer (LOC) and glideslope (GS).
- Consider Backup Methods: Even if you're using modern systems like FMS with VNAV and LNAV, setting the course as a backup is good practice. This allows for a traditional flying revert if any issues arise with the FMC or LNAV.
Navaid Frequency Considerations:
When working with navaid frequencies, keep the following in mind:
- Interference and Protection: Same-frequency navaids are typically spaced well beyond the radio horizon to prevent interference. However, certain conditions, like propagation perturbations, can increase distant station signals, potentially causing co-channel interference.
- Malfunction Reporting: Report any suspected navaid malfunctions, including erratic course indications, improper coded identification, or frequency interference. This assists in prompt correction and ensures the reliability of navigation systems.
- Standard Service Volumes (SSVs): The FAA publishes SSVs for most navaids, ensuring adequate signal strength and freedom from interference within a three-dimensional volume. However, SSVs don't account for potential blockage from terrain or obstructions.
- Navigation Database Checks: While rare, there are instances of close-frequency navaids. Regularly update your navigation databases and refer to sources like Skybrary and AVweb for information on potential frequency confusions.
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Setting the course dials to match the runway heading
Understanding the Basics:
Firstly, it's important to understand the difference between "heading" and "course". Heading refers to the direction in which the aircraft's nose is pointed. On the other hand, the course is the desired path or route to be followed to reach a specific destination or waypoint. In the context of landing, the course relates to the runway heading, which is the direction of the runway.
Identifying the Runway Heading:
Before setting the course dials, you need to identify the runway heading for the airport you are approaching. Runway headings are typically indicated by a number, such as 27 or 28, and they represent the orientation of the runway in degrees. For example, a runway designated as 27 could have a heading of 273 degrees.
Tuning the Nav Radios:
Once you know the runway heading, you need to tune your navigation radios accordingly. Look up the ILS (Instrument Landing System) frequency for the runway you are approaching. This information can usually be found on approach charts or through air traffic control communications. Dial in this ILS frequency into the active portion of your Nav radios in the center console.
Setting the Course Dials:
Now, you can set the course dials to match the runway heading. Adjust the course dial to the exact heading of the runway you identified earlier. By doing this, you are programming the aircraft to follow the desired path toward the runway during your approach.
Selecting the Appropriate Mode:
After setting the course dials, select the APR (Approach) mode on the EFIS (Electronic Flight Instrument System) selector. This mode will provide you with vital information about your alignment with the localizer (LOC) and glideslope (GS). The localizer helps you stay on course with the runway heading, while the glideslope guides you to the correct descent angle for a safe landing.
By following these steps and setting the course dials to match the runway heading, you are ensuring that your aircraft is properly aligned with the runway during the approach. This precision is crucial for safe landing procedures, especially in low-visibility conditions or when operating in complex airspace.
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Selecting the APR mode on the EFIS selector
The APR mode, also known as the Autopilot APR Mode, is used in conjunction with the EFIS (Electronic Flight Instrument System) selector. This mode is particularly useful when flying an ILS (Instrument Landing System) approach. The EFIS selector allows you to choose between different display modes, such as PLAN, ARC, and ROSE NAV, with only one mode active at a time.
To select the APR mode, follow these steps:
- Dial in the heading of the runway you plan to land on. This step ensures that your aircraft is aligned with the runway's heading during the approach.
- Tune the frequency of the navaid. Each runway has a specific ILS frequency that you need to dial into the active portion of the Nav radios in the center console.
- Look up the final approach course on the approach plate. The ILS approach chart for the airport will provide you with the necessary frequency and course information, which may differ from the runway number.
- Set the course via the EFIS selector. After obtaining the final approach course information, use the EFIS selector to set the course, ensuring that your autopilot and manual display function correctly.
- Verify alignment with the localizer (LOC) and glideslope (GS). By selecting the APR mode on the EFIS selector, you can confirm that your aircraft is properly aligned with the localizer and glideslope during the approach.
It is important to note that newer Boeing aircraft, such as the 777, may not have the APR mode feature. Instead, they utilize a system where you enter the VOR into the FMC and then select an inbound or outbound course to track.
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Using the CRS selector
The CRS Selector is used to set the desired course for a specific navigation source, such as a VOR (VHF Omnidirectional Range) or an ILS (Instrument Landing System) approach. It is important to note that it doesn't have to be the approaching airport or runway heading, but it often aligns with the runway during an ILS approach.
When using the CRS Selector, you must first tune your navigation radio to the desired VOR or ILS frequency. This ensures that you are connected to the correct station. Once you have identified the correct station, you can proceed to set the desired course using the CRS Selector. For example, if you are entering an ILS approach for runway 21, you will set your CRS (course) heading to 210. This way, when your ILS indicator shows that you are too far left, you know you are too far left relative to the heading you are travelling.
In the case of a VOR, you will set the CRS to the desired radial you want to track to or from the VOR station. This helps you establish your aircraft's position relative to the station and enables you to fly along specific airways. For instance, if you are approaching runway 10, you would set the runway 10 heading or enter 100 in the course selector. It is important to remember that directions on a compass are typically displayed in three digits, so 10 degrees would be 010 degrees.
After setting the desired course, you can engage the appropriate autopilot mode, such as NAV, VOR/LOC, or APPR, to follow the selected course. This allows your aircraft to automatically navigate towards the set course.
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Frequently asked questions
The course selector is used to select a bearing (ADF), radial (VOR) or an approach course (ILS).
First, set up the frequency and look up the final approach course, i.e., the exact orientation of the runway. Then, dial in the final approach course via the course selector. Once you're close enough, you should see yourself aligning with the ILS and you can hit the APP button to do an automated ILS approach.
You need to set the course selector so that the autopilot knows which radial to follow. Tune the frequency of the navaid, look up the final approach course on the approach plate and set that via the course selector.
No, newer Boeings such as the 777 do not have this feature.
