Fix a FlightFactor A350 that stays high on RNAV approaches in X-Plane by checking FCU altitude, descent modes, FMS sequencing and vertical-path support.
In X-Plane, the FlightFactor A350 usually stays high on an RNAV approach because descent was not authorised, the FCU altitude or mode selection prevents it, or the FMS has no usable vertical path. An inactive final leg, incorrect constraints, mismatched navdata, a route shortcut, or interception from above can produce the same symptom.
Why does the FlightFactor A350 fly above the RNAV path?
The quickest diagnosis is to match what the FMA and navigation display show with the most likely failure.
| What you see | Likely cause | Check first |
|---|---|---|
| Top of descent has passed; FMA shows ALT or ALT CST | Descent was not commanded, or the aircraft is holding a selected altitude or constraint | FCU altitude, next restriction and active vertical mode |
| Vertical path is below the aircraft | A late direct-to, vector, level-off or delayed descent left insufficient distance | Remaining track miles and altitude to lose |
| Lateral guidance works but no vertical deviation appears | The procedure has no supported vertical path, or the final leg is not active | Approach minima, transition and FMS sequencing |
| The aircraft levels unexpectedly | A database or manually entered altitude constraint is stopping descent | The active flight-plan leg and its restriction |
| The aircraft descends but remains high and fast | Excess speed, a tailwind or late deceleration has created an energy problem | Speed target, descent mode and available distance |
The top-of-descent symbol is advisory; reaching it does not make the A350 descend. The pilot must set an altitude permitted by the clearance and engage an appropriate descent mode. Turning the altitude selector alone is not enough.
A direct-to can remove many miles from the calculated profile, while blindly deleting every flight-plan discontinuity can create an unrealistic connection across a vectors segment. Old navdata is not automatically faulty, but a mismatch between the chart and database can change waypoint order, constraints or the available transition. Our X-Plane VNAV descent and mode-capture checklist covers these wider causes in more detail.
Does every RNAV approach give the A350 vertical guidance?
No: RNAV describes area navigation, not a guarantee of an automatically flyable glidepath.
| Charted minima or procedure | What to expect | Correct response |
|---|---|---|
| LNAV | Lateral guidance only, even if the FMS draws an advisory descent profile | Observe the published step-down altitudes and use a suitable selected vertical mode or calculated continuous descent |
| LNAV/VNAV | Barometric vertical guidance may be available if the procedure is coded correctly and supported by the aircraft build | Confirm that a vertical path and the required final-approach mode are actually displayed |
| LPV | Requires modelled SBAS capability; loading the procedure does not prove that the FlightFactor A350 supports its glidepath | Use it only when the aircraft provides the appropriate guidance and annunciation |
| RNP AR | May require specialised capability and procedure logic not fully represented by every add-on build | Check the minima and required capability rather than assuming support from the procedure name |
The minima line is more useful than the words RNAV or RNP in the approach title. If the FMS has lateral legs but no descent angle, vertical-deviation indication or final vertical mode, treat the approach as lacking automatic vertical guidance. Our explanation of lateral-only RNP procedures and supported vertical guidance shows how to fly the alternatives without chasing a path that does not exist.
How do I set up an RNAV descent in the FlightFactor A350?
A reliable RNAV descent requires the correct procedure, a continuous flight plan, an authorised descent and capture from a sensible position.
- Verify the procedure and transition. Match the runway, approach identifier, transition and minima with the procedure you intend to fly. Use our guide to checking transitions, altitude restrictions and minima on procedure charts if the database route differs from the chart.
- Inspect the remaining flight-plan legs. Confirm waypoint order and identify any discontinuity, vectors leg or manual segment. Connect a discontinuity only when the route is genuinely meant to continue directly to the next fix.
- Check every altitude constraint. Look for an incorrect manually entered value and distinguish between at, at-or-above and at-or-below restrictions. A single bad constraint can force an unnecessary level-off or an impossible descent.
- Complete the approach data. Enter the requested QNH, temperature, wind and minima. Change from standard pressure to local pressure at the appropriate point, and make sure hPa and inHg have not been confused.
- Authorise descent near top of descent. Set only the altitude to which the aircraft is cleared and command managed DES. Do not dial below a clearance simply to make the aeroplane chase the profile.
- Manage the energy early. A high speed target, tailwind or delayed deceleration may prevent the aircraft from regaining the path. Reduce speed in time and use speedbrake within the aircraft's operating limits when needed.
- Activate and arm the correct functions. Activating the approach phase changes the speed schedule; it is not the same as arming final vertical guidance. Make sure the correct final leg is active before arming the supported approach mode.
- Read the FMA. Confirm that the expected lateral and vertical modes are active rather than assuming the autopilot is following every magenta indication.
What should the flight mode annunciator show?
The flight mode annunciator is the authoritative indication of what the FlightFactor A350 autopilot is doing.
- ALT means the aircraft is holding the selected altitude. It will not descend merely because the calculated path has moved below it.
- ALT CST indicates a level-off at a flight-plan altitude constraint.
- DES indicates managed descent using the FMS profile, subject to the selected altitude, constraints and available aircraft performance.
- OP DES commands descent towards the selected altitude but does not mean the aircraft is tracking the calculated vertical profile.
- V/S or FPA provides a selected vertical rate or angle. The pilot remains responsible for meeting every restriction and intercepting the path correctly.
- APP NAV with FINAL APP, or the equivalent indications implemented by the installed build, shows that final lateral and vertical approach guidance is active.
An armed mode is not yet an active mode. A magenta approach line on the navigation display also proves only that lateral geometry is loaded; it does not confirm that a vertical path has been captured.
Why will FINAL APP not capture from above?
FINAL APP normally needs to intercept a valid vertical path from on or below it, within a sensible capture angle.
If the vertical-deviation indication is already well below the aircraft, repeated approach-mode selections will not command a steep dive. If cleared, use managed descent, open descent or an appropriate selected flight-path angle to return towards the profile while respecting all altitude restrictions. Re-arm final guidance only from a credible intercept position.
Do not use the PAPI alone to decide whether the FMS is wrong. The visual glidepath and coded RNAV path can have different origins and threshold-crossing geometry. A large or increasing FMS vertical deviation is the more useful sign that the aircraft has lost the calculated profile.
How can I recover if the A350 is already too high?
Recover only when enough distance remains to descend, slow and configure without violating a restriction; otherwise, go around.
- Identify the actual problem. Check the selected altitude, active leg, next constraint, vertical deviation and FMA mode before changing anything.
- Estimate the required distance. A rough planning check is about three nautical miles for each 1,000 feet to lose, with additional distance needed for deceleration and configuration. This is a planning aid, not a replacement for the FMS prediction.
- Increase descent only if permitted. Use an appropriate descent mode and speedbrake within limits. Do not exceed flap or landing-gear extension speeds in an attempt to rescue the approach.
- Respect the constraints. Level at a mandatory restriction rather than chasing the path through it, and never select an uncleared lower altitude solely to force descent.
- Discontinue an unstable approach. If the aircraft remains high, fast or incorrectly configured at the chosen stabilisation gate, fly the missed approach and set up again with an earlier descent.
When is it probably a FlightFactor A350 bug?
An add-on fault becomes likely when a supported vertical path is displayed, the correct final leg is active, the aircraft approaches from below, the required modes are armed, and capture still fails repeatedly.
Repeat the test using a FlightFactor build intended for the installed major X-Plane version. Use the same procedure and transition in a clean flight, and temporarily remove unrelated scripts or plug-ins that can change autopilot, flight controls or navigation data. An inconsistent chart and database cycle should be corrected before treating the failure as an aircraft bug.
After a repeatable failure, record the X-Plane version, aircraft build, runway and approach, transition, navdata cycle, active leg, relevant constraints, FCU altitude and FMA indications. Inspect Log.txt for aircraft or plug-in errors and preserve it before starting another X-Plane session, which can overwrite the previous log. Those details separate a genuine systems fault from unsupported guidance, bad sequencing or a descent-mode mistake.