How do you read IFR en-route charts for flight simulation?

To read an IFR en-route chart in a flight simulator, choose the low- or high-altitude chart for your planned level, trace the route through airways and fixes, read each leg’s course and distance, respect published altitude limits, then verify every waypoint and navaid against the simulator’s navigation database.

For general flight simulation—including Microsoft Flight Simulator, X-Plane, Prepar3D and FSX—the method is broadly the same. Symbol shapes, units and altitude terminology vary between chart authorities, however, so the chart’s title block, marginal notes and legend always override a rule of thumb.

Which IFR en-route chart should you use?

Use the chart covering both your geographical area and intended cruising level.

Do not select a chart purely from the aircraft type. A business jet flying below the upper-route boundary may still require a low-altitude chart. Under the US chart system, low charts normally cover routes below 18,000 feet MSL and high charts begin at FL180; boundaries and terminology elsewhere can differ.

Check the chart’s effective date against the navigation-data cycle used by the aircraft. Our guide to sourcing current sectional and IFR en-route chart files explains the chart side of that check.

An en-route sheet covers the portion between terminal areas. It does not replace the SID, STAR, approach plate or airport diagram; see how the complete chart set fits together during a simulated flight.

What do the IFR chart symbols and numbers mean?

Each charted line, label and number describes either a route, a position, a course, a distance, a navaid or a vertical limit.

A frequent error is following one airway straight across another. Crossing lines do not create a usable intersection unless the chart marks a fix or navaid there. Likewise, never estimate course or distance by measuring the printed map; use the published values.

How do you read en-route minimum altitudes?

Read the altitude attached to the exact route segment, then fly at or above the highest applicable minimum unless an upper limit prevents it.

• MEA — minimum en-route altitude: normally provides required obstacle clearance and acceptable navaid coverage for the full segment under that chart authority’s criteria.
• MOCA — minimum obstruction clearance altitude: provides obstacle clearance but may guarantee conventional navaid reception only near the station. Under US rules, the VOR reception guarantee normally extends within 22 NM of the facility.
• MRA — minimum reception altitude: the lowest altitude at which a particular fix can be reliably determined using the specified navigation source.
• MCA — minimum crossing altitude: an altitude that must be reached before or when crossing a fix in the indicated direction.
• MAA — maximum authorised altitude: the highest usable altitude for that route segment, often because of navigation-signal limitations.
• Grid or off-route altitude: a broad-area obstacle-clearance figure. It is not automatically an airway MEA and does not guarantee navigation, communications or controlled-airspace protection.

Abbreviations are not universal. Some chart systems use different forms of minimum safe altitude or route altitude, and values may be expressed as feet or flight levels. Check the legend before interpreting an isolated number.

How do you turn an en-route chart into a flight plan?

Build the flight plan by recording each entry fix, airway, exit fix and direct segment in the order shown on the chart.

1. Confirm coverage and dates. Select the correct low- or high-altitude sheets, read their legends and compare their effective dates with the aircraft’s navigation database.
2. Find the terminal connection points. Start at the final fix of the SID or another suitable departure-area fix. Finish at the first STAR fix or an appropriate arrival-area fix.
3. Trace connected segments. Follow each airway from a valid entry point to a valid exit. Watch for route-designator changes, one-way restrictions and minimum-altitude changes.
4. Write the route string. An illustrative entry such as ABCDE V123 FGHIJ means join airway V123 at ABCDE and leave it at FGHIJ. If the avionics cannot accept airway entry, load every intervening fix individually.
5. Build the vertical plan. Note the MEA or other governing minimum on every leg. Then choose a cruise altitude that also suits direction-of-flight rules, terrain, aircraft performance and any simulated ATC clearance.
6. Load and inspect the avionics. Confirm waypoint order, coordinates, airway name and leg type. Remove unexpected route discontinuities only after deciding what published connection should replace them.
7. Cross-check while flying. Compare the charted course, distance and next fix with the CDI, HSI, FMS or moving map. Our method for converting charted fixes, courses and radials into cockpit actions covers that practical scan.

Can you fly a conventional airway with GPS?

You can fly a conventional airway with GPS or an FMS when the onboard database contains the correct route and fixes, but the chart still defines where that airway runs.

For procedure realism, tune and identify the underlying VORs when the aircraft and route use conventional navigation. An RNAV route instead requires suitable simulated RNAV or GPS capability; its line on the chart is not permission to approximate it with headings. Route prefixes differ by country, although US T- and Q-routes generally identify RNAV routes.

If you are practising raw-data navigation, our primer on tuning and tracking VORs and NDBs explains station identification, TO/FROM indications and course interception.

Why does the simulator route not match the chart?

A simulator route usually disagrees with the chart because the two are using different navigation-data cycles or different databases.

• Cycle mismatch: an airway may have been rerouted, renamed or withdrawn after the simulator’s data was compiled.
• Separate simulator databases: the world map, built-in ATC, aircraft FMS and third-party aircraft can each use different route data.
• Wrong waypoint selected: duplicate or similar identifiers can place a waypoint hundreds of miles from the intended route.
• Magnetic-reference differences: charts and avionics based on different magnetic epochs may show slightly different courses while joining the same two fixes.
• Automatic direct legs: a planner may silently replace a missing airway with DCT, producing a plausible-looking magenta line that is not the charted route.

Compare the chart date and FMS cycle first, then inspect every suspect fix by coordinates and neighbouring waypoints. Where matching data is unavailable, use one internally consistent chart-and-database combination. Updating only one component can make the disagreement worse.

Common IFR en-route chart mistakes

Most chart-reading errors come from assigning the right-looking number or symbol to the wrong route segment.

• Treating a line crossing as an intersection when no fix is marked.
• Reading a segment distance as a course, frequency or altitude.
• Using a grid minimum as though it were an airway MEA.
• Assuming the published minimum is the best cruise altitude rather than the lowest permitted one under specified criteria.
• Using direct-to between airway fixes and still considering the aircraft to be on the published airway.
• Trusting the moving-map line without checking identifiers, leg sequence and coordinates.
• Flying a reciprocal of a printed course without checking whether the route is directional or whether the reverse course is separately published.