Fix PMDG VNAV not engaging in MSFS by checking FMC data, route activation, MCP altitude, flight directors and the flight mode annunciator.
PMDG VNAV in Microsoft Flight Simulator usually fails because the FMC route is inactive, PERF INIT is incomplete, the active leg is invalid, or the MCP altitude blocks the profile. Complete and execute the FMC setup, set an appropriate MCP altitude, switch on both flight directors, then confirm the mode on the FMA.
These checks apply broadly to PMDG Boeing aircraft. CDU page names, descent-intervention controls and take-off mode transitions can differ slightly between models.
How do I get PMDG VNAV to engage?
Work through the setup in this order; most failures come from an incomplete FMC or an altitude selected on the MCP that prevents the commanded movement.
- Activate and execute the route. The CDU should show an active route such as
ACT RTE, not merely an entered route waiting for activation. Execute any pending modification. - Complete PERF INIT. Enter or confirm zero-fuel weight, reserves, cost index and cruise altitude. Complete the model's normal thrust-limit and take-off-reference pages as well. A route import does not fill every required performance field; our airliner FMC setup explanation covers how the route and performance pages fit together.
- Inspect the LEGS page. Confirm that the expected waypoint is active and that no route discontinuity breaks the climb or descent profile. Do not delete a deliberate vectors segment simply to remove every discontinuity.
- Check the departure position. The selected runway and departure should match where the aircraft actually starts. An active leg far behind the aircraft or on the wrong side of the route can prevent sensible guidance.
- Set the MCP altitude correctly. For a climb, select the cleared altitude above the aircraft. Before descent, select a cleared altitude below the aircraft. VNAV will not climb above or descend below the MCP altitude.
- Switch on both flight directors. Arm the autothrottle if automatic thrust is wanted. Autothrottle is separate from VNAV availability, while the flight directors are part of the AFDS mode logic.
- Select VNAV and read the FMA. The flight mode annunciator at the top of the primary flight display is the authoritative indication. The light in the VNAV button alone does not prove that VNAV is actively controlling pitch.
What should the flight mode annunciator show?
The FMA tells you whether VNAV is active, armed, blocked by altitude or replaced by another vertical mode.
| FMA indication | What it means | What to check |
|---|---|---|
VNAV SPD | VNAV is active and commanding pitch to maintain its target speed. | This is normal during much of the climb and during some path-recovery situations. |
VNAV PTH | The aircraft is following the calculated vertical path. | This is the expected mode through a managed descent when the path is captured. |
VNAV ALT | VNAV remains engaged, but the aircraft has levelled at an MCP-selected altitude. | Check whether the MCP altitude is blocking the next climb or descent segment. |
TO/GA | Take-off guidance is still the active pitch mode. | VNAV may be armed and waiting for the normal post-lift-off mode transition. |
ALT HOLD, V/S or LVL CHG | Another vertical mode is controlling the aircraft. | Correct the FMC and altitude setup, then reselect VNAV when interception is appropriate. |
Why does VNAV arm but not climb after take-off?
VNAV does not normally replace TO/GA while the aircraft is still on the runway; it transitions after lift-off when the AFDS conditions for that PMDG model are met.
Set the MCP altitude above the aircraft, verify that the route and performance pages are complete, and watch the FMA rather than assuming the autopilot must already be engaged. With the autopilot off, VNAV can command the flight-director bars, but the pilot must follow them manually. If CMD itself will not engage, use our autopilot engagement checks for Microsoft Flight Simulator.
Why won't PMDG VNAV descend at top of descent?
PMDG VNAV usually remains level at top of descent because the MCP altitude has not been lowered, the route contains a break, or another vertical mode has taken control.
- Lower the MCP before TOD: select the next cleared altitude below the aircraft. Lowering it does not cause an immediate descent before TOD; it gives VNAV permission to follow the profile when required.
- Check the active route: an unexecuted arrival change, missing waypoint or discontinuity can remove or move the calculated descent path.
- Allow for a moving TOD: changes to winds, speed, runway, arrival or altitude constraints can shift the top-of-descent marker.
- Use early-descent logic deliberately: if the CDU offers
DES NOW, or the aircraft provides an altitude-intervention function, use the procedure for that PMDG model and verify the resulting FMA. Repeated altitude-intervention presses can remove intervening FMC constraints. - Recover a high path: if the CDU reports that drag is required, reduce energy with the permitted speedbrake setting.
LVL CHGorV/Scan help recapture the path, but they replace VNAV while active; monitor speed closely and reselect VNAV only when a sensible intercept exists.
Does importing a flight plan prepare VNAV automatically?
Importing a route does not complete the performance data or guarantee that every leg is valid in the PMDG FMC.
A plan visible on the Microsoft Flight Simulator World Map is not proof that the PMDG CDU contains an active, executed route. With the PMDG 737, follow the correct SimBrief import and route-activation procedure, then complete PERF INIT manually.
Different navigation-data cycles can also produce missing waypoints, changed procedures or unexpected discontinuities. Correct the route rather than blindly joining two legs that were never intended to connect.
Can VNAV work without the autopilot?
VNAV can provide flight-director commands without CMD engaged, but it will not physically fly the pitch commands unless the autopilot is connected.
Autothrottle, autopilot and VNAV are related but separate systems. Selecting V/S, LVL CHG or ALT HOLD replaces VNAV as the active vertical mode even though the FMC route remains available.
What if PMDG VNAV still will not engage?
A persistent failure after a correct setup points to a stale aircraft state, conflicting control input or an installation problem rather than normal VNAV logic.
- Read the CDU scratchpad message. Correct the named problem instead of repeatedly pressing VNAV. Missing performance data and invalid route geometry should be fixed in the FMC first.
- Test a simple flight. Load a normal PMDG panel state on the ground, enter a short route manually and avoid complex arrivals. This separates a basic aircraft problem from a faulty imported plan.
- Disable interfering automation. Turn off AI piloting and assisted control features for the test. Check hardware bindings for buttons or axes repeatedly commanding vertical speed, altitude hold or level change.
- Remove relevant add-on conflicts. Temporarily disable cockpit, avionics or autopilot modifications that can affect the PMDG aircraft. Ordinary scenery is unlikely to cause a VNAV mode failure.
- Update through the correct purchase channel. PMDG and Marketplace installations use different update workflows. For the 737, follow our PMDG 737 update and repair procedure before reinstalling the whole simulator.