6.5 Earth Coordinates, UTC, Chart Projections, and Flight Instruments

FAA Aircraft Dispatcher Certificate ADX

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1 Chapter 1: Regulations, Certification & Operational Control

1.1 Part 65 Subpart C: Certification, Eligibility & Currency 1.2 Operational Control & Dispatcher-PIC Joint Responsibility 1.3 Domestic, Flag & Supplemental Operations Framework 1.4 Dispatch Release Elements, Signatures & Recordkeeping 1.5 Regulations, Manuals, Crew Qualifications, and Source Control

2 Chapter 2: Atmospheric Physics, Pressure Systems & Fronts

2.1 Atmospheric Structure, Standard Atmosphere & Altimetry 2.2 Air Masses, Frontal Systems & Frontogenesis 2.3 Atmospheric Stability, Lapse Rates & Cloud Formation 2.4 Earth Motion, Regional Weather, Local Winds, and Water Phase Changes

3 Chapter 3: Aviation Weather Hazards & Severe Weather Avoidance

3.1 Structural and Induction Icing: Types, Accretion & Operations 3.2 Thunderstorms, Squall Lines, Microbursts & Low-Level Windshear 3.3 Clear Air Turbulence (CAT), Mountain Waves & Jet Streams 3.4 Low Ceilings, Fog Types & Visibility Restrictions 3.5 Hurricanes, Typhoons, Tornadoes, and Tropical Dispatch Hazards

4 Chapter 4: Weather Observations, Forecasts & Advisories Decoding

4.1 METAR and SPECI Surface Observations: Decoding & Operations 4.2 Terminal Aerodrome Forecasts (TAF): Groups & Timing 4.3 Pilot Weather Reports (PIREP): Coding, Severity & Urgent Alerts 4.4 In-Flight Advisories: AIRMETs, SIGMETs & Convective SIGMETs 4.5 Weather Collection, NWS Facilities, GFA, and EWINS

5 Chapter 5: Aviation Weather Charts & Upper-Air Analysis

5.1 Surface Analysis & Radar Summary Charts 5.2 Constant Pressure Analysis & Winds Aloft (FB) 5.3 Significant Weather Prognostic Charts (SIGWX) 5.4 Satellite Imagery, Moisture-Stability Analysis, and Forecast Integration

6 Chapter 6: Air Navigation, Airspace Architecture & Route Structure

6.1 National Airspace System: Classes, Rules & Special Use 6.2 Ground-Based Navigation Aids & Standard Service Volumes 6.3 Area Navigation (RNAV), GNSS/GPS, PBN & RNP Fundamentals 6.4 En Route Airways, SIDs, STARs & Chart Interpretation 6.5 Earth Coordinates, UTC, Chart Projections, and Flight Instruments 6.6 North Atlantic, Pacific, RVSM, and Global Navigation Differences

7 Chapter 7: Instrument Approaches, Minimums & Airport Operations

7.1 Precision Approach Systems: ILS Categories & Tolerances 7.2 Non-Precision Approaches, RNAV & Decision Minimums (MDA/DA) 7.3 Takeoff Minimums, Lower-Than-Standard & Takeoff Alternates 7.4 Holding Procedures: Patterns, Speed Limits & Timing

8 Chapter 8: Subsonic Aerodynamics & Jet Aircraft Performance

8.1 Subsonic Jet Aerodynamics: Lift, Drag & Flight Regimes 8.2 High-Altitude Flight: Mach Number, Buffet & Coffin Corner 8.3 Transport Turbine Engines: Thrust, Specific Fuel & Bleed Air

9 Chapter 9: Transport Category Takeoff & Landing Runway Analysis

9.1 Takeoff Performance Speeds & Balanced Field Concept 9.2 Takeoff Climb Segments & Obstacle Clearance Gradients 9.3 Landing Performance: Field Lengths, 60% Rule & Contamination

10 Chapter 10: En Route Performance, Driftdown Profiles & ETOPS Operations

10.1 One/Two-Engine-Inoperative En Route Net Profiles & Driftdown 10.2 Extended-Range Operations (ETOPS): Philosophy & Regulations 10.3 ETOPS En Route Alternates: Adequate vs. Suitable & Critical Fuel

11 Chapter 11: Aircraft Weight & Balance, Center of Gravity, and Loading

11.1 Transport Aircraft Structural Weight Limits: Definitions & Rules 11.2 Center of Gravity Computations: Datum, Arm, Moment & Index 11.3 Mean Aerodynamic Chord (%MAC) Computations & Stability 11.4 Payload-Range Analysis, Zero Fuel Weight Tradeoffs & Loading

12 Chapter 12: Destination Alternate Airport Selection & Weather Rules

12.1 Destination Alternate Selection: 91.169 & Part 121 1-2-3 Rule 12.2 Flag & Supplemental Operations Destination Alternate Rules 12.3 Derived Alternate Minimums: 1-Nav and 2-Nav Facility Rules

13 Chapter 13: Part 121 Fuel Planning, Reserves & En Route Re-Release

13.1 Part 121 Domestic Fuel Requirements: Reserves & Calculations 13.2 Part 121 Flag Fuel Requirements: 10% Reserve & Island Rules 13.3 Supplemental Fuel Requirements & Holding Fuel Management 13.4 Redispatch and En Route Re-release Procedures

14 Chapter 14: Transport Systems, Pressurization & MEL/CDL Procedures

14.1 Transport Jet Auxiliary Power, Electrical, Hydraulic & Pneumatic Systems 14.2 Cabin Pressurization, Rapid Decompression & Oxygen Requirements 14.3 Master Minimum Equipment List (MMEL), MEL & CDL Procedures 14.4 Flight Controls, Autoflight, Fuel, Oil, Brakes, and Fire Protection

15 Chapter 15: Hazardous Materials, Duty Regulations & Emergency Procedures

15.1 Dangerous Goods Carriage by Air (49 CFR Part 175) & NOTOC 15.2 Dispatcher Duty Limitations, Rest Requirements & Fatigue 15.3 Emergency Authority, Declaration & Diversion Decision-Making 15.4 NTSB Part 830 Accident Reporting & Wreckage Preservation 15.5 Security, Overdue Aircraft, and FAA Emergency Services

16 Chapter 16: Communications, ATC, and Flight Plan Procedures

16.1 Voice, Data Link, Position Reports, and Lost Communications 16.2 ATC Facilities, Separation, ICAO Flight Plans, and Traffic Management

17 Chapter 17: Human Factors and Practical Dispatch Applications

17.1 Dispatch Resource Management, Human Error, and Risk Decisions 17.2 Manual Flight Planning, PIC Briefing, Flight Watch, and Postflight Closeout

6.5 Earth Coordinates, UTC, Chart Projections, and Flight Instruments

Key Takeaways Explain This Topic AI

45.5° equals 45°30′, not 45°50′; coordinate formats and hemispheres matter.

Great-circle shortest distance and a wind-optimized route can differ.

UTC calculations must carry the date through midnight and forecast windows.

Heading, track, true/magnetic reference, and airspeed/groundspeed are distinct quantities.

FMS route/database and navigation integrity require independent crosschecks.

Last updated: October 2026

Translate Position and Time into a Usable Flight Plan

A dispatcher must read a route consistently across charts, flight-plan coordinates, navigation displays, and weather periods. Latitude, longitude, time reference, and chart projection are basic syllabus topics. A plausible-looking coordinate or local-time estimate can put a route in the wrong hemisphere or apply the wrong forecast. The practical skill is to identify the reference and verify every conversion.

Coordinates and distance

Latitude measures angular position north or south of the Equator. Longitude measures angular position east or west of the Greenwich reference meridian. Include hemisphere designators and the correct degrees/minutes format. A coordinate entered in decimal degrees must be converted if the receiving field requires degrees and minutes; the decimal part is not itself a minutes value.

For example, 45.5 degrees north equals 45°30′ N , because 0.5 × 60 = 30 minutes. Do not read it as 45°50′. A longitude of 120° west is not interchangeable with 120° east. At high latitudes, a small longitudinal angle corresponds to less surface distance than near the Equator because the meridians converge.

A nautical mile corresponds approximately to one minute of latitude. That relationship does not mean every minute of longitude is one nautical mile at every latitude. For short operational exercises, use the chart scale or approved navigation computation rather than applying a latitude shortcut to all directions and distances.

Great circles, rhumb lines, and projections

A great circle follows the shortest surface path between two points on a spherical Earth model. A rhumb line crosses meridians at a constant angle, maintaining constant true course. A route selected for least time or fuel can differ from the geometrically shortest route because of winds, weather avoidance, airspace, performance, and airport constraints.

A Mercator projection represents rhumb lines conveniently as straight lines but distorts scale toward the poles. A Lambert conformal conic projection is useful across many midlatitude aeronautical charts and approximately represents great-circle segments over suitable distances. A gnomonic projection represents great circles as straight lines with its own distortion. The projection explains chart geometry; it does not authorize use of an outdated or inappropriate chart for IFR planning.

Planning concept Question to ask

Coordinate Which format, hemisphere, and datum apply?

Distance Which chart scale or approved calculation is used?

Track Is it true, magnetic, great-circle, or another defined course?

Chart Which projection, coverage, cycle, and units apply?

Route Does the cleared/authorized path actually follow the planned geometry?

UTC and date rollover

Coordinated Universal Time (UTC) is the shared reference for aviation weather and many flight records. Local time zones and seasonal clock changes are not fixed offsets everywhere year-round. Use the appropriate conversion for scheduling, then retain UTC and date explicitly in the operational calculations.

A hypothetical flight departs at 2340Z on the 12th and has an estimated duration of one hour fifty minutes. Arrival is 0130Z on the 13th , not 2530Z on the 12th. The destination ETA ± one-hour window crosses the date boundary: 0030Z–0230Z on the 13th. Select TAF groups using the encoded day/hour dates, and include any amendment that changes those periods.

Crossing the International Date Line also changes the local calendar relationship. Elapsed time and UTC remain consistent. Do not count fuel endurance or dispatcher duty by subtracting two displayed local clock times without accounting for their dates and zones.

Heading, course, and wind

Course/track describes the desired or actual ground path. Heading describes the aircraft nose direction. Wind can require a heading different from course and makes groundspeed different from true airspeed. Magnetic variation changes the relationship between true and magnetic directions; compass deviation is an aircraft-specific magnetic-instrument effect.

For a supplied true course of 100° and east variation of 12°, the corresponding magnetic course is 88° . If the approved wind calculation supplies a true heading of 108° for that course, the magnetic heading is 96° . Keep the references separate; do not apply variation twice or confuse heading with track. Use the stated weather/ATC direction reference rather than assuming every wind report uses the same convention.

Airspeed and altimetry errors

IAS is indicated airspeed. CAS corrects instrument and position error. EAS also addresses compressibility. TAS describes speed through the air, while groundspeed adds the wind-vector effect. High density altitude changes the relationship between indicated and true speeds; a chart can require a particular speed type. Read its labels before substituting an FMS groundspeed for an aerodynamic input.

Pitot/static blockage can make airspeed, altimeter, or vertical-speed indications misleading depending on which openings are blocked and the drain/configuration state. Position error, instrument error, nonstandard temperature, and incorrect pressure settings are different error sources. A plausible altitude indication can therefore coexist with inadequate true obstacle clearance in cold air.

Airborne navigation instruments and automation

Modern transports can combine EFIS , FMS , inertial reference/navigation, GNSS, VOR/DME, and other sensors. The FMS database and active route must be checked against current charts and clearance. An inertial system can accumulate error; a GNSS position can lose integrity; a display can retain a route that no longer matches ATC authorization. Redundant displays do not prove independent navigation sources.

Transponders and altitude encoding support surveillance but do not themselves establish accurate onboard navigation. A dispatcher considers a defect's MEL restrictions, route approvals, required surveillance/navigation capability, and airport procedures. During flight, the crew uses approved abnormal procedures and available alternatives; dispatch supplies relevant route, weather, navaid, and airport information.

Verification exercise

A fictional flight plan contains an east/west coordinate reversal, a local arrival time lacking a date, and a stale navigation database indication. Identify each independent defect before computing fuel or assigning alternates. Correct the coordinate using its actual source, establish the UTC date/time, and verify the approved database/procedure basis. Then rebuild the route and relevant weather windows. Correct arithmetic performed on those wrong references would still be an incorrect dispatch solution.

Official References

Source check: 2026-10-12 . FAA AIM navigation guidance ; FAA aeronautical handbooks and current addenda ; Current AC 91-70 oceanic guidance . For operational use, apply current issued authorizations and the assigned aircraft’s approved data.