Study guide
16.1 Voice, Data Link, Position Reports, and Lost Communications
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
16.1 Voice, Data Link, Position Reports, and Lost Communications
Key Takeaways Explain This Topic AI
ACARS, CPDLC, ADS-C, ADS-B, and SELCAL have different functions; one working system does not prove every authorization.
Except in emergencies, § 121.99 company communications are independent of U.S.-operated systems.
A safety message requires receipt, understanding, and any required concurrence, not transmission alone.
§ 91.185 clearance-limit timing depends on whether the limit is an approach-start fix and whether EFC was received.
Last updated: October 2026
Communication Is a Completed Exchange
Aircraft dispatch communications connect the flight to operational-control support, while ATC communications provide traffic clearances and coordination. The two functions overlap in an emergency but are not interchangeable in ordinary operations. A dispatcher must understand each system's range, intended recipient, approval, latency, and fallback. A transmitted message that has not been received or understood is an incomplete safety communication.
Voice and coverage
VHF generally provides line-of-sight communications and is widely used in terminal and continental operations. Terrain, altitude, range, antenna/system status, and assigned frequencies affect availability. HF supports longer-range communications through propagation that can vary with atmosphere and ionospheric conditions. Satellite voice offers another path where approved and available, but coverage and reliability still need to be evaluated for the route and possible diversion altitudes.
SELCAL (selective calling) alerts a crew to an addressed call on a monitored communications arrangement. It does not itself carry a complete ATC clearance, supply aircraft position, or eliminate the need to establish the associated communication. Verify the appropriate checks and calling arrangements under the approved regional/company procedure rather than assuming a successful alert test proves all links remain available throughout flight.
Data links and surveillance
- System Primary function
- ACARS Aircraft/company and other supported addressed messaging over approved communication media
- CPDLC Controller–pilot data-link exchange for approved ATC messages
- ADS-C Contract-based position/surveillance reporting to an applicable ground system
- ADS-B Broadcast surveillance information; not a text-clearance exchange
- SATCOM Satellite communication medium supporting approved voice and/or data services
The medium and application differ. ACARS may use VHF, HF, or satellite transmission. CPDLC and ADS-C require the appropriate aircraft, system, operator, and airspace arrangements. A company ACARS reply does not prove an ATC CPDLC logon, and an ADS-C report does not represent PIC concurrence with a dispatch amendment.
Ordinary regulatory requirements
Section 121.99 requires domestic/flag route communications providing reliable and rapid links between the aircraft and dispatch and ATC through direct or approved arrangements. Except in an emergency, company dispatch systems must be independent of systems operated by the United States. Flag ETOPS adds the applicable voice and additional-system requirements, considering possible diversion routes and altitudes.
Supplemental flight following uses the approved §§ 121.125/127 arrangements and does not universally have the same inflight-center monitoring requirement. Before accepting a communication deferral, check the actual operation and authorization. A usable link on the planned cruise route does not automatically satisfy a lower diversion route or the required additional ETOPS path.
Protocol and workload
Identify the flight and intended recipient. State the operational issue, relevant time/location, required action or decision, and acknowledgment needed. Use clear units and UTC dates where applicable. Avoid ambiguous statements such as “alternate bad” when the crew needs to know which airport, what condition, when it applies, and what verified alternatives exist.
For a release amendment, distinguish an information update from a requested operational decision. Obtain the required PIC concurrence and record the completed exchange under the approved procedure. A data-link transmission status can show technical delivery while the crew has not yet reviewed the operational content. During takeoff, approach, or an emergency, prioritize concise safety information and use the carrier's appropriate urgent-contact method.
Position reports
Conventional voice position reporting can include aircraft identity, position and time, level, next position/estimate, and subsequent position as required by the applicable procedure. Automated reporting has its own contract and equipment conditions. Use the actual regional and company requirements; do not mandate every field on every radar-monitored domestic flight.
Dispatch compares progress with the planned route, estimated times, fuel trends, and relevant weather. An unexplained missing report triggers the approved follow-up and overdue process. A surveillance position and a company fuel report can originate at different times; do not combine them as if simultaneous without checking timestamps.
Lost communications under U.S. IFR rules
Section 91.185 first addresses operation in VFR conditions: if VFR is encountered, continue under VFR and land as soon as practicable. If IFR must continue, the route priorities are assigned, the route to the specified fix/route/airway when being radar vectored, the expected route where applicable, and the filed route when neither assigned nor expected applies. Use the highest of the last assigned altitude, applicable minimum IFR altitude, or altitude ATC advised may be expected, as applicable to the segment.
Clearance-limit timing is a separate test in § 91.185(c)(3) . If the limit is a fix from which an approach begins, commence descent/approach as close as possible to the EFC time received, or the appropriate filed/amended ETA if none was received. If it is not such a fix, leave at EFC if received, or on arrival if none, then proceed to an approach-start fix and commence as close as possible to the applicable ETA. An EFC does not create one universal timing instruction for every enroute hold.
Dispatcher support during failure
Attempt approved alternate links and coordinate relevant information with ATC and company contacts. Avoid inventing an aircraft clearance. The PIC follows the applicable rules and aircraft procedures; oceanic and foreign contingencies may have additional regional requirements. If a known inflight emergency requires dispatcher action and contact with the pilot cannot be established, § 121.557(b) requires declaring an emergency and taking necessary action.
For a fictional data-link failure, voice contact remains available and the flight is in radar coverage. Confirm which authorization or reporting function has failed, use the approved fallback, and evaluate route/capability effects. Do not treat every failed ACARS printer as total ATC radio failure, and do not treat a working company phone patch as proof that the original navigation/surveillance authorization remains satisfied.
Official References
Source check: 2026-10-12 . FAA AIM clearances and flight plans ; Lost communications § 91.185 ; Route communications § 121.99 ; FAA dispatcher PTS . For operational use, apply current issued authorizations and the assigned aircraft’s approved data.