Set the Boeing 737 course knob for ILS, localiser and VOR flying, understand LNAV logic, and diagnose common capture errors.
In a general Boeing 737 simulator, turn each COURSE/CRS knob to the published ILS or localiser front course, or to the VOR course you intend to track. The selector does not command a turn or alter an FMC route in LNAV; use HDG SEL or change the FMC route for that.
What does the 737 course knob control?
The course knob sets the radio-navigation course reference for its side of the flight deck. Most simulated 737 variants have left and right CRS selectors on the Mode Control Panel, corresponding broadly to the captain’s and first officer’s navigation displays and receivers.
Its precise effect depends on the aircraft model. In a detailed simulation it affects VOR, localiser and ILS presentation and the associated radio-navigation guidance; in a simpler add-on, part of that behaviour may be simplified or merely visual.
| Control or mode | What it controls | What it does not do |
|---|---|---|
| COURSE/CRS | Selected VOR, localiser or ILS course reference | Command the aeroplane to turn to that heading |
| HEADING with HDG SEL | The magnetic heading the autopilot or flight director should fly | Change the tuned radio course or FMC route |
| LNAV | Tracks the active FMC leg | Follow the number displayed in the CRS window |
How do you set the course for an ILS or localiser?
For a normal front-course ILS or localiser approach, set the charted front course, tune or verify the correct frequency, and arm the appropriate approach mode.
- Read the published approach course. Use the figure shown for the actual ILS or localiser procedure rather than estimating it from the runway number.
- Tune and verify the frequency. Some add-ons tune it automatically; others require manual tuning of NAV 1 and, when needed, NAV 2.
- Rotate the CRS selectors. Use the mouse wheel, click-drag control or assigned hardware input until the required value appears in each course window.
- Set both sides when appropriate. Matching left and right courses is normal for an ILS and is essential to a correctly configured dual-channel approach in add-ons that model one.
- Establish a sensible intercept. Approach the localiser from the correct side at a manageable angle. Be below the glideslope before expecting normal glideslope capture.
- Arm the correct mode. Use APP for a full ILS or VOR/LOC when only localiser guidance is required, then confirm the armed and captured modes on the Flight Mode Annunciator.
Runway numbers are rounded to the nearest ten degrees, while the charted localiser course is more precise and may be offset slightly from the runway centreline. Runway 27 therefore does not prove that the correct setting is exactly 270 degrees.
Our 737 descent and approach set-up sequence places this step in the wider arrival flow. MSFS users can also follow our MSFS 2024 ILS tuning and capture procedure.
This front-course advice applies to normal ILS and localiser approaches. A published back-course procedure needs procedure- and aircraft-specific handling, and many 737 add-ons do not model back-course guidance consistently.
How do you set a VOR course without reverse sensing?
For VOR navigation, set the course you actually intend to fly and check that the TO/FROM indication agrees with your plan.
- Tune the required VOR on the receiver used by your side of the flight deck.
- Confirm the station using its identifier if the simulation models ident audio or text.
- Choose inbound or outbound. A radial is always defined as extending away from the station; an inbound course is normally the reciprocal of that radial.
- Set the desired course with the relevant CRS knob.
- Check the deviation and TO/FROM indication. If the steering appears backwards, recheck whether you selected the course or its reciprocal.
For example, an aircraft east of a VOR can fly inbound towards it on course 270; that aircraft is initially on the 090 radial. Flying away from the station on the 090 radial requires course 090 and a FROM indication.
Why does the course knob do nothing in LNAV?
LNAV follows the active FMC leg, so changing the CRS window does not alter the aeroplane’s commanded path.
There is no normal 737 flight-deck setting called an LNAV log. If that search phrase brought you here, the relevant concept is usually LNAV logic: the FMC calculates lateral guidance from the programmed route, active waypoint and leg type. Developer or diagnostic logs supplied by individual add-ons are separate from the course selector.
To change the LNAV path, modify or activate the correct FMC leg; our guide to programming and checking a 737 FMC route covers that process. To leave LNAV and fly a selected heading instead, set the heading knob and engage HDG SEL.
LNAV may remain active while APP or VOR/LOC is armed. That is normal: LNAV continues steering until the localiser mode captures. The Flight Mode Annunciator, not the position of the course knob or an illuminated button alone, tells you which mode is actually controlling the aeroplane.
Should both 737 course selectors be set the same?
Set both course selectors to the same published front course for a normal ILS or localiser approach unless a specific procedure requires something different.
If you are flying single-channel and using only one receiver, the course on that side is the immediate operational reference. Matching both sides still prevents conflicting indications. For a dual-channel approach or simulated autoland, both receivers and both course settings normally need to agree, alongside the other aircraft-specific prerequisites.
The selectors may legitimately differ during raw-data training or when each pilot’s side is referencing a different VOR. A mismatch is therefore not automatically a fault; it must make sense for the navigation setup.
Why will the localiser or autopilot still not capture?
A correct course setting cannot compensate for a wrong frequency, poor intercept or incorrectly armed mode.
- Wrong or outdated frequency: the chart, simulator navigation database and installed scenery may represent different data cycles. If no localiser signal appears, verify the frequency against the data used by the simulator.
- Wrong receiver or pilot side: NAV 1 may be tuned correctly while the display or autopilot channel you are checking is associated with NAV 2.
- Reciprocal course entered: use the published front course for a normal ILS, not the opposite direction.
- APP or VOR/LOC not armed: turning the course knob never arms capture by itself. Check the Flight Mode Annunciator.
- Unstable intercept: excessive speed, a large intercept angle or joining from the wrong side can prevent reliable capture.
- Above the glideslope: the localiser may capture while the glideslope does not. Reposition below the beam rather than trying to chase it down from above.
- Still following LNAV: this is normal until LOC capture if approach mode is armed; it is a problem only when no radio-navigation mode has been armed.
- Input conflict: if the CRS value moves or snaps back, check duplicated controller bindings, cockpit-assistance features and automated co-pilot functions.
The dependable rule is: ILS or localiser — published front course; VOR — intended tracking course; LNAV — active FMC leg, not the course knob.