How do I fly an RNP approach in a flight simulator?

To fly an RNP approach in a flight simulator, we load the published approach into the FMS or GPS, verify every waypoint and altitude constraint, then fly lateral guidance in LNAV or NAV and vertical guidance with VNAV, GP or step-down altitudes as the avionics allow. The critical part is checking what kind of RNAV/RNP approach you actually loaded, because the mode logic and minima are not always the same.

What is an RNP approach in a flight simulator?

An RNP approach is an area-navigation approach that relies on onboard navigation performance rather than ground-based beams like an ILS. In practice, most sim pilots will see it published as an RNAV approach using GNSS, sometimes with minima labelled LNAV, LNAV/VNAV or LPV.

That matters because the way we fly it depends on the type of guidance available. Some aircraft and simulators can follow both lateral and vertical guidance almost like an ILS. Others only provide lateral guidance, which means we must manage descent manually using the charted step-down altitudes.

Also, not every simulator models RNP exactly. Some default avionics treat many RNP procedures as generic RNAV approaches, and advanced features such as curved RF legs or tightly controlled RNP AR procedures may not work properly unless the aircraft and navdata support them.

What do I need before starting the approach?

Before we fly any RNP approach, we need three things to agree with each other: the approach chart, the loaded procedure in the avionics, and the type of guidance the aircraft can actually fly. If one of those is wrong, the approach can look normal until final, then unravel quickly.

• Current navdata: old navdata can mean missing fixes, wrong transitions or altitude errors.
• The correct transition: loading the wrong initial or intermediate transition can place you on the wrong side of the procedure.
• Correct altimeter setting: especially important for baro-VNAV and all altitude checks.
• Appropriate minima: use LNAV, LNAV/VNAV, LPV or other minima that match your avionics.
• Missed approach brief: know the heading, altitude and first fix before intercepting final.

RNP, RNAV, LNAV and LPV: what is the difference?

Sim pilots often use these terms interchangeably, but they are not identical. This is where many unstable approaches begin.

How do I actually fly an RNP approach?

1. Load the approach into the FMS or GPS, including the correct transition and runway. Do not assume the box picked the right one automatically. We always cross-check the sequence of fixes against the chart.
2. Review the minima and final approach fix. Identify whether you are flying LNAV, LNAV/VNAV, LPV or another line of minima. Note the final approach fix altitude, missed approach point and any step-down fixes.
3. Check the route for discontinuities or odd turns. A broken flight plan, duplicated fix or unexpected hold can make the aircraft turn away at exactly the wrong moment. If the avionics show curved legs, verify that your aircraft can actually fly them.
4. Set up the aircraft early. We aim to be established, slowed down and fully briefed before the initial or intermediate approach segment. Late configuration changes are one of the main reasons sim pilots chase the path all the way down final.
5. Intercept the approach in NAV or LNAV. If ATC vectors you onto final, arm the lateral mode you normally use for FMS tracking. On many aircraft that is LNAV or NAV rather than approach mode at first.
6. Confirm the active waypoint sequence. Make sure the avionics have sequenced to the correct inbound leg and are not still navigating to an earlier fix. This sounds basic, but it catches a lot of failed approaches in sims.
7. Manage vertical guidance correctly. If the approach supports vertical guidance and your avionics model it, arm the relevant mode before the final descent point. Depending on the aircraft, that may be VNAV, GP capture through approach mode, or a similar vertical mode. If no usable vertical guidance exists, descend manually at the published fixes.
8. Watch for glidepath, not glideslope. On RNAV approaches, the vertical indication is often a glidepath rather than an ILS glideslope. In some cockpits the mode annunciation will differ, and some autopilots will not capture it unless the correct approach type is active.
9. Cross-check every altitude. Even with VNAV or GP active, we still verify that the aircraft crosses each fix at or above, at, or at or below the charted altitude. In simulators, vertical guidance can be wrong if the database, altimeter or mode logic is off.
10. At minima, decide. If the runway environment is in sight and you are stable, continue. If not, execute the published missed approach immediately and let the avionics sequence to the missed approach only when appropriate for your aircraft.

Do I use APP mode on an RNP approach?

Sometimes yes, sometimes no. This is one of the biggest gotchas because different avionics families behave differently.

On some aircraft, we use APP or APR mode to capture an RNAV glidepath, much as we would on an ILS. On others, APP is really intended for localiser and glideslope capture, while RNAV vertical guidance is better flown with VNAV or an FMS approach mode. If you press APP and nothing sensible happens, the aircraft may simply not use that mode for non-ILS approaches.

The safe rule is this: follow the mode logic your aircraft models, but do not trust it blindly. The charted altitude profile is the final authority, not the magenta line.

How do I fly an RNP approach with no vertical guidance?

If you only have LNAV minima, treat the approach as lateral guidance only. The FMS will keep you on centreline, but it may not provide an approved descent path.

In that case, we descend to each published altitude at the correct fix, just as we would on a non-precision approach. Some avionics display an advisory glidepath; that can help with situational awareness, but unless the procedure and aircraft support proper vertical guidance, we do not substitute it for the published altitudes and minima.

Common mistakes when flying RNP approaches in sims

• Using the wrong minima: flying LPV-style all the way down when only LNAV minima are available.
• Arming the wrong autopilot mode: especially using an ILS-oriented mode that will not capture RNAV vertical guidance.
• Skipping altitude checks: trusting VNAV or GP even when the aircraft is clearly high or low.
• Loading vectors instead of the full transition: then wondering why fixes or descent constraints are missing.
• Flying too fast on final: many autopilots can track the path while the aircraft itself is unstable.
• Bad sequencing at the final approach fix: the aircraft may turn, level off or dive if the active leg is wrong.
• Assuming every RNAV approach is a true RNP operation: a lot of simulators simplify this.

Simulator limitations you should expect

RNP approaches expose weak spots in sim avionics more quickly than an ILS does. If something looks odd, it may be the software rather than your technique.

• RF legs may be drawn incorrectly or flown as straight segments.
• Baro-VNAV behaviour may be simplified.
• Approach mode annunciations may not match real aircraft logic exactly.
• Missed approach sequencing can be inconsistent, especially if you disconnect automation late.
• Default GPS units may provide advisory guidance that looks more authoritative than it really is.

That is why we always fly the chart first and the automation second. If the box disagrees with the published procedure, the published procedure wins.

A practical technique that works well

If you want a dependable sim technique, brief the approach like this: identify the approach type, confirm the final approach fix altitude, note whether you expect LNAV only or vertical guidance, and decide in advance which lateral and vertical modes you will use. Then get configured early and verify each fix crossing on the way down.

That keeps the workload under control. It also makes it obvious when the avionics are doing something suspect, which is half the battle with simulated RNP procedures.

Quick answer: the shortest correct method

Load the correct RNAV/RNP procedure, verify the fixes and altitudes, intercept final in LNAV or NAV, use VNAV or approach glidepath only if your aircraft and the selected minima support it, and cross-check every altitude to decision altitude or MDA. If the runway is not in sight at minima, go around.