NOTE: State regulators and industry routinely scrutinize GNEs, altitude deviations, erosion of longitudinal separation, and non-approved operations in SAOs. The reduction of separation standards in oceanic areas requires special attention to navigation, altitude, and time to help mitigate the risk of lateral overlap or operational errors.
b. Monitoring Process Actions. Because of the large variety of circumstances existing in the relationships between states and their operators engaged in oceanic operations, we do not expect that all states will make maximum effort to comply with the responsibilities resulting from the application of special use airspace restrictions (such as MNPS) while keeping administrative arrangements within reasonable limits.
• Monitoring of the operator’s navigation performance in cooperation with the flightcrew.
• Monitoring of the operator by the state having jurisdiction over that operator to ensure that they apply adequate provisions while conducting authorized flight operation.
• Monitoring of actual navigation performance during normal flight operations by means of radar used by the ATC units of states providing service in the region.
• Monitoring can also be done on the basis of position reporting.
c. Monitoring by the Operators. Carry out post-flight monitoring and analysis for two important reasons: it facilitates the investigation of any reported GNE and assists in identifying any deterioration in equipment performance.
(1) Record Documentation. Decisions regarding monitoring of an aircraft’s navigation performance are largely the prerogative of individual operators. In deciding what records to keep, airlines should consider the stringent requirements associated with special use airspaces such as MNPS. Investigating all errors of 20 NM or greater in MNPS airspace is a requirement for airlines. Whether radar or the flightcrew observes these deviations, it is imperative to determine and eliminate the cause of the deviation. Therefore, operators should keep complete flight records so that they can make an analysis. The retention of these documents must include the original and any amended clearances.
(2) Documentation Requirements. Operators should review their documentation to ensure that it provides all the information required to reconstruct the flight. These records also satisfy the ICAO standard of keeping a journal. Specific requirements could include, but do not only apply to, the following:
• Record of the initial ramp position (latitude/longitude) in the LRNS, original planned flight track, and levels.
• Record of the LRNS gross error check, RVSM altimeter comparisons, and heading reference cross-checks before entering oceanic airspace.
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• Plotting charts to include post waypoint 10-minute plots.
• All ATC clearances and revisions.
• All position reports made to ATC (e.g., voice, data link).
• The master document used in the actual navigation of the flight, including a record of waypoint sequencing allocated to specific points, ETA, and actual times of arrival (ATA).
• Comments on any navigation problems relating to the flight, including any discrepancies relating to ATC clearances or information passed to the aircraft following ground radar observations, including weather deviations or wake turbulence areas.
d. Monitoring of the Operator by the State. You may take decisions regarding the monitoring of operators by the state unilaterally, but there should be a cooperative process concerning the specifications that satisfy the operator while planning and reviewing achieved performance. Much of this process involves FAA-approved procedures and monitoring to ensure compliance. Varied circumstances influence the relationships between states and their operators, and also impact monitoring functions. ICAO standards require operators to maintain an aircraft log in which the crew records the performance of the navigation equipment. Use this log as a basis for investigation if significant equipment deficiencies occur.
CHAPTER 4. ATLANTIC, CANADA, AND EUROPEAN OPERATIONS
4-1. ATLANTIC REGION. The Atlantic Region includes:
• Minimum Navigation Performance System (MNPS) airspace.
• North Atlantic (NAT) non-MNPS airspace (north of the equator).
• West Atlantic Route System (WATRS).
• South Atlantic (south of the equator).
a. Operations in MNPS Airspace and Operator Responsibilities. Operators travel in the NAT airspace more than any other oceanic airspace in the world.
Approximately 1,000 aircraft transit the NAT everyday. Operations in MNPS airspace have specific navigation and communication requirements. Operators are responsible for reviewing Notices to Airmen (NOTAM) and applicable reference material to determine the Communication, Navigation, and Surveillance (CNS) requirements.
b. General Aviation Oceanic Navigation Performance. Another area of concern in the NAT, as well as other areas, is that of general aviation oceanic navigation performance conducted by non-turbine light aircraft and Search and Rescue (SAR) missions conducted by International Civil Aviation Organization (ICAO) member states for U.S.-registered aircraft.
These aircraft have strayed off course and imposed a severe manpower and economic strain on those states conducting the SAR missions. This situation has a negative impact on international relations between the United States and other ICAO member states. These ICAO member states do not require U.S.-registered aircraft making oceanic flights and departing from the United States to have a letter of authorization (LOA) and/or an inspection unless they are to penetrate MNPS airspace. These member states require the same aircraft, however, submit to an inspection of both the aircraft and the flightcrew if departing from or flying over Canada.
c. MNPS Airspace. The largest amount of air traffic in any region is over the NAT between Europe and the United States. Most air carriers plan eastbound flight departures in the evenings so that morning arrival in Europe will permit a full day’s business or touring. Air carriers plan westbound flight departures for just the reverse reason (leaving in the morning so passengers arrive in the United States at a convenient local time). The westbound flights do not create a problem in air traffic congestion due to the breadth of the eastern coast of the United States. However, eastbound flights arriving in Europe from North America converge on the relatively small geographic area of the United Kingdom and have to be filtered onto extremely crowded European routes. Because of this situation, ICAO procedures adopted following agreement between member states strictly control traffic control across the NAT.
d. NAT Non-MNPS Airspace.
• Unrestricted operations require dual long-range navigation system (LRNS) and dual long-range communication system (LRCS).
• Restricted operations over Greenland and Iceland are dependent upon specific routing.
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e. WATRS. Restricted operations require dual LRNS and dual LRCS. This airspace is now Required Navigation Performance 10 (RNP-10) with a separation standard of 50 nautical mile (NM) lateral and 10 or 15 minute longitudinal. Some routings will require at least single long-range navigation system (S-LRNS) and Single Long-Range Communication System (SLRCS).
f. South Atlantic (South of the Equator). Operations require dual LRNS and dual LRCS.
NOTE: See the following Web site for more information on the North Atlantic MNPS Airspace Operations Manual: www.paris.icao.int.
4-2. COMMUNICATIONS. Require two independent, operational high frequency (HF) radios.
Shortly after departing northeast Canada, terminate radar service, requiring you to make position reports to air traffic control (ATC) on very high frequency (VHF) or Automatic Dependent Surveillance (ADS). At this time, crews should ensure they have established a HF and Selective Call (SELCAL) guard with the assigned ATC facility to comply with the requirement of continuous two-way ATC communication capability. At the latest, do this before leaving VHF coverage. Choose the HF frequency by the height of the sun, not the time of day.
a. Iceland. FAA recommends that crews review the Icelandic AIP on radio procedures.
Even without instruction, maintain contact with Reykjavik Control when in VHF range. You might receive radar vectors around an area of military operations or they may need to provide spacing for crossing traffic. When not in contact with Reykjavik Control on VHF, give position reports to Iceland Radio or applicable HF NAT frequencies. Iceland Radio forwards position reports to the next ATC facility for coordination purposes.
b. Position Reports North of 70°. North of 70°NORTH latitude, give position reports every 20° of longitude (between 10° and 50°WEST longitude). South of 70°NORTH latitude, give the position every 10° of longitude (between 5° and 65°WEST longitude). When operating on a random route, weather—including midpoint weather—is given with position reports. Give the position, fuel, and weather for the fix followed by the midpoint latitude and longitude, temperature, and wind. For example, “at 6135 NORTH, 45 WEST, minus 54, 250 diagonal 40.”
To state “midpoint weather” or longitude only is not enough information for entry into the meteorology computers. For example, if the longitude of the midpoint “W045” is entered into the flight management computer (FMC) on the LEGS page and then brought down to the scratchpad, it will show the latitude as well as the longitude of the midpoint. Report wind to the nearest 10° and 5°knots.
NOTE: When using HF or Controller-Pilot Data Link Communication (CPDLC), send only mandatory fix position reports.
4-3. NAVIGATION. Navigation requires two independent, operational LRNSs. For the Airspace Operations Manual, see the following Web site: www.paris.icao.int. The Class II navigation chapter in the flight manual explains the encoding of database waypoints such as 6230N. These waypoints programmed in the FMC for our convenience along the most heavily traveled routes represent latitude and longitude coordinates. Operating north of 67° N.,
however, it is necessary to load the 7-character (i.e., N72W050) or the full 15-character latitude/longitude coordinates because database waypoints do not exist.
4-4. SURVEILLANCE—CANADIAN CONTROL AREAS.
FIGURE 2. CANADA—NORTHERN, SOUTHERN, AND ARCTIC CONTROL AREAS
a. Northern, Southern, and Arctic CTA. Northern Control Area (NCA) and Southern Control Area (SCA) tracks Alfa through Kilo require Class II navigation on all or a portion of the route. Class II navigation procedures should begin at the track entry point unless the flight is still in radar contact or within 200 miles of a VHF Omnidirectional Range/distance measuring equipment (VOR/DME) in order to permit radio updating of the FMC position. For example, track Kilo begins within 200 miles of a VOR, while the aircraft is still in radar contact (or true).
Courses and distances between the Flight Plan Forecast and the FMC LEGS page are in accordance with the procedures set forth in the Flight Operation Manual (FOM). In this case, Class II navigation procedures would not be required until both radar contact and distance measuring equipment (DME) updating was lost. (Displayed on Position page 2/3.) However, track Delta begins at a non-directional radio beacon (NDB) with the nearest VOR at a distance of 445 NM. In this case, Class II navigation procedures should begin approaching the track entry point.
(1) Flights within SCAs, NCAs, and Arctic Control Areas (ACA). All flight within the SCA will use magnetic heading reference while flight within the NCA and ACA will reference to true north.
(2) NCA and ACA: Areas of Magnetic Unreliability (AMU). The FAA designates the NCA and ACA as AMUs due to their proximity to the magnetic North Pole.
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(3) Switch Instructions. Flights operating within these areas should position the HDG/MAG REF switch to TRUE. Reposition this switch to NORMAL when leaving the NCA or ACA. On some aircraft when descending from cruise altitude amber, the navigation display (ND) will display TRUE as a reminder that you did not reselect NORMAL.
b. Position Reports. Position is reported in Canada’s NCA and SCA by track letter and longitude only. Over 90° West on NCA route Charlie, state the position: “Charlie, nine zero west.” If you give the position report to air traffic control (ATC) (Edmonton or Montreal Centers), give only section one (position) and omit fuel and weather. The company receives any position report given to general purpose (GP) (call sign “radio”).
4-5. EUROPEAN REGION.
a. Airport Weather. The principal movement of air over Great Britain and Northwestern Europe is from the west. Since air coming from this direction has a long history over the ocean, the climate is maritime with moderate temperatures, ample and evenly-distributed rainfall, low amount of sunshine, and frequent low clouds and fog with associated poor visibility. Moreover, the waters of the northeastern Atlantic are relatively warm for their latitude due to the Gulf Stream, the Icelandic low pressure cell, and the pressure field over the continent of Europe.
These undergo a reversal with the seasons, from high pressure in winter to low pressure in summer. Seasonal variations in precipitation amounts and in frequency of cyclonic circulation patterns are quite small, indicating an essential similarity of flow patterns throughout the year.
However, there are very important differences in the seasonal weather as there is a greater frequency of low ceilings and poor visibility during the winter than in the summer.
b. Amsterdam. The greatest frequency of below minimum weather occurs in December when conditions below 200 feet and 1/2 mile occur nearly 10 percent of the time. The coldest month is January with average daily temperatures of 31 Fahrenheit degrees. While there is an even amount of rainfall throughout the year, the heavy month is normally August.
c. Brussels. December through March have the highest frequency of low ceilings and visibility, with fog prevalent from September through February.
d. Frankfurt. The normal winter season begins in late October or early November. The transition from winter to spring is a slow process and the frequency of low ceilings and visibility is at a minimum. The weather is generally warm and fair, but precipitation averages are highest from June through August. During the winter months, fog, snow, and low clouds produce low ceilings. In the summer, showers and/or thunderstorms and early morning fog cause below minimum conditions.
(1) Temperature and Rainfall. The average annual temperature at Frankfurt is 49 Fahrenheit degrees. The coldest month is January and the highest is in July with 95°F-100°F range. The total annual precipitation at Frankfurt is about 25 inches. The maximum rainfall occurs in the summer. There is not much variation between months as the amount falling during the time with the most rain is about twice that of the driest month.
(2) Thunderstorms and Fog. Thunderstorms occur from May through September with a frequency of four to eight per month. These thunderstorms have a tendency to develop over the Page 52 Par 4-4
hills surrounding the Frankfurt area and pass over the field during the late afternoon hours. Fog in the summer usually dissipates by 9 or 10 a.m. The two major weather features are thunderstorms and fog.
e. London Heathrow. Heathrow is about 15 miles west of London at an elevation of 80 feet. The airport lies in a built up area south and east of the major sources of smoke pollution.
Restriction from ceiling and even more visibility is frequent in winter. During summer, ceilings below 1,500 feet and/or visibility below 3 miles occur only on 12 percent of the afternoons and evenings. Reports of conditions below these limits during winter occur in 49 percent of the early evening. Moreover, reports of conditions below 300 feet and/or less than 1 mile occur nearly 15 percent of the time in the winter. During this season, high-pressure systems that break off from northeastward extensions of the Azores High drift across the area. Clearing skies in the area of the high permit radiation cooling and formation of ground fog in the low-level stagnant, moist air. When such fog forms, it is quite persistent and may last for several days. In mid-winter, the sun is not effective in dissipating the fog since there is less than eight hours of daylight and the sun is not far above the horizon. Ground fog may occur during the warmer season, but it is usually confined to the morning hours. Smoke pollution often occurs with fog to further restrict visibility. This is a problem at Heathrow with light easterly winds. For London in midsummer, the mean daily temperature averages 55 Fahrenheit degrees and the maximum is 74 Fahrenheit degrees. In midwinter, the mean daily minimum is about 36°F to 48°F. Northerly wind components are most common in the spring and southerly components in the fall. Winds greater than 25 miles per hour (mph) are rare in the London area.
f. Milan Malpensa. The average daily maximum is 63 Fahrenheit degrees and the average daily minimum is 47 Fahrenheit degrees. It can be as hot as 96 Fahrenheit degrees in July and August and as cold as 5 Fahrenheit degrees in January and February. Precipitation is well distributed and averages 31.6 inches for the year as October and November are the wettest months. According to records, the maximum rainfall in a 24-hour period occurred during a November with 4.1 inches. There is a total of 79 days per year with 0.04 inches or more. Snow may lie on the ground for several days in the winter. Fog is most frequent during the winter when it can be extremely heavy and last for many hours. Summer is relatively fog free and ceilings improve considerably as hot summer winds come in from the Mediterranean.
g. Munich. Snow covers the ground on average of 57 days during the winter months.
While snow may fall frequently, the falls are light and rarely heavy enough to register as a problem at the airport. There is a high occurrence of low ceilings during the month of December.
h. Paris Charles De Gaulle. The Atlantic Ocean is 150 to 200 NM west of Paris, the English Channel is 75 NM to the northwest and the North Sea is 125 NM to the north. Winds from these directions are generally moisture laden in the lower levels.
(1) Average Temperature. There is relatively little obstruction to the airflow from the Mediterranean via the Rhone Valley of southern France. The Rhone Valley is part of a broad gap between the Pyrenees and the Alps through which warm, moist air masses may move. As a result, there is a relatively small annual range of average temperature and a rather even distribution of precipitation. Average temperature is 37 Fahrenheit degrees in January and Par 4-5 Page 53
Page 54 Par 4-5 66 Fahrenheit degrees in July with extremes of 4°Fahrenheit degrees and 104°Fahrenheit degrees.
(2) Ceilings and Visibility. The fog season starts in September and reaches a maximum in November, December, and January when the frequency of ceilings and visibility at or below 300 feet and 1 mile approaches 25 percent. In mid-winter, the sun is rather ineffective at dissipating fog. Due to differences of surrounding topography and airport elevations, Paris airports may have significant differences in visibility. The prevailing winds at Paris are west-southwest. Southerly and northerly winds occur with moderate frequency. In January and February, winds in excess of 25 mph are common.
CHAPTER 5. NORTH PACIFIC OCEANIC OPERATIONS
5-1. INTRODUCTION. Apply required navigation performance 10 (RNP-10) throughout the Asian/Pacific region. Flights in the Northern Pacific (NOPAC) en route to Asia do not have to contend with the same traffic density as in North Atlantic Operations (NAT/OPS). Although navigation in the NOPAC once involved serious political implications if a navigation error occurred, this is no longer the case because of the implementation of a RNP-10 navigation requirement on the NOPAC routes and on the Central East Pacific (CEP) routes between Hawaii and the west coast of the United States. In addition, the implementation of Reduced Vertical Separation Minimums (RVSM) between flight level (FL) 290 and 410 inclusive requires special training, special navigation equipment, and operational approvals. For details of approval requirements and any changes in the mandatory FLs, see the following Web site:
www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/oceanic/.
5-2. COMMUNICATIONS. Use standard International Civil Aviation Organization (ICAO) terminology throughout the Pacific and Far East regions. In the Pacific, monitor an air-to-air frequency of 123.45 along with very high frequency (VHF) 121.5. There is no ICAO inter-flight communication frequency assigned for the route between NRT and BKK, including the South China Sea, but commonly use 123.45.
a. Air Traffic Control (ATC). When operating in airspace controlled by Oakland Oceanic (KZAK) and Tokyo Oceanic (RJTG), use Automatic Dependent Surveillance-Contract (ADS-C) and Controller-Pilot Data Link Communications (CPDLC) as the primary means of ATC communication and position reporting. When operating on or near the NOPAC routes in Anchorage Center or Anchorage Oceanic (PAZA), they require VHF or high frequency (HF).
Also use ADS and CPDLC in the Anchorage Control Area (CTA). When an ATC handoff to Anchorage occurs, utilize CPDLC to make position reports. If operating in Russian airspace, use VHF or HF communication. If you plan a flight along BLUE 337, you may use CPDLC in airspace controlled by Magadan Control (GDXB). Similar to other areas where CPDLC is active, you should accomplish a logon 15 to 45 minutes prior to crossing the flight information region (FIR), unless an automatic logon occurs.
b. HF Radios. Areas where VHF communication with ATC is not available, whether or not CPDLC is in use, require HF radios. Before entering an area using CPDLC, obtain the primary and secondary HF frequencies and a Selective Call (SELCAL) check from the general purpose (GP) radio facility serving the area. Advise the radio operator that the flight is CPDLC equipped. Use the GP facility San Francisco ARINC when departing Seattle. Eastbound departures from Tokyo will use Tokyo Radio. As an example, a flight departing the West Coast for Tokyo with routing through Oakland’s oceanic airspace would use the following terminology: “San Francisco Radio, (Aircraft xxx) will be Seattle to Tokyo, requesting primary and secondary HF, we are CPDLC equipped.” Relay this last statement to Oakland, which sets the stage for a CPDLC ATC link when sending the first position report.
c. Backup Communication. Although HF communication is a mandatory backup for a CPDLC link, primary and secondary HF frequencies and SELCAL checks are necessary for Par 5-1 Page 55
operation along all routes in the NOPAC including Russian airspace. We recommend to occasionally refresh these HF frequencies while en route.
d. VHF ATC. Communication is available along most of the route between Tokyo and Bangkok. A short segment in the South China Sea approaching the coast of Vietnam will require communication with Hong Kong Radio on HF. Normally perform an HF radio and SELCAL check with Tokyo Radio at NRT but achieving an HF contact at BKK can be difficult. Attempt a contact with Hong Kong Radio on 8942 first.
e. HF Reception Test. If all else fails at the gate, confirm HF reception on WWV frequencies 5000, 10000 or 15000 and check transmitter operation for an audible side tone. Try Hong Kong Radio again when airborne. Frequency 8942 is the most likely HF assignment leaving Ho Chi Minh Control.
f. Outside of an ADS or CPDLC Area. Position reporting in the Pacific and over Russia is accomplished verbally in the conventional Aircraft Report (AIREP) section 1 format. With either method, give reports at compulsory reporting points, FIR boundaries, or requested waypoints. When operating south of the NOPAC routes, make position reports every 10° of longitude. These positions generally conform to the output points on the Flight Plan Forecast. On the route between Tokyo and Bangkok or Hong Kong, Japanese airspace as far south as Okinawa does not require position reports due to positive radar control.
g. Company (Part 121 Operations). A communication link must exist between a flight and airline dispatch at all times in every part of the world. Reliable SATCOM Voice communication capability exists in all areas of the Pacific and Far East operations. This includes Russian airspace along routes approved for these aircraft. The SATCOM Voice directory may contain menus with Pacific area direct-dial line selections such as the following examples:
• NOPAC ATC (Oakland, Anchorage, Tokyo, Naha).
• ASIA ATC (Hong Kong, Singapore).
• DISPATCH.
• STATION OPS.
• ARINC (San Francisco).
h. VHF ACARS. Coverage extends from the U.S. and Canadian Pacific Coast out to the western-most point of the Aleutian Island chain. After a gap south of the Kamchatka Peninsula, coverage resumes over the Japanese Islands and continues into the South China Sea. VHF ACARS is again available in Thailand. Beyond these areas, communication for companies is available by HF Long Distance Operational Control (LDOC) in addition to SATCOM Voice and SATCOM data link. San Francisco ARINC and LDOC service spans nearly the entire Pacific Ocean and reaches well into Russian airspace.
i. Flight Management Computer (FMC) Aircraft. On the FMC aircraft, arm automatic position reporting when sending an uplink request for wind data. Should this feature be inoperative, airline dispatch will expect the crew to make periodic manual position reports.
Using the Message To Company feature in the ACARS menu, sending a Route Report from the CDU ROUTE page or line selecting REPORT on the POS REPORT page will ensure to alert the Page 56 Par 5-2
Par 5-2 Page 57 dispatcher. Do not forward HF position reports to ATC and CPDLC downlinks; only forward position reports, sent to GP radio, to the company.
5-3. NAVIGATION.
a. Class II Navigation. The NOPAC requires Class II navigation procedures and position plotting. Use a North Pacific/Mid-Pacific plotting chart. Russian airspace also requires Class II navigation procedures when operating beyond the range of non-directional radio beacons (NDB) which define the airways. VHF Omnidirectional Range/distance measuring equipment (VOR/DME) Navigational Aids (NAVAID) are practically nonexistent in Russia. Due to the proximity of NDBs along GREEN 212 between VALTA and TAKHTAYAMSK, Class I navigation on this segment is approved. We encourage utilizing raw data navigation information along these routes and will require tuning NDBs on the control display unit (CDU) NAV/RAD page. Russian Class II areas do not require plotting since you accomplish flight along established airways.
b. Class I Navigation. Class I exists on the route between Tokyo and Bangkok and does not require position plotting. En route NAVAID outages, however, have the potential for turning almost any long-range international flight into one requiring Class II navigation procedures. As a result, accomplish the basic Class II navigation checks on all flights exceeding 1,000 NM outside North America. These would include:
• Magnetic compass deviation check.
• Air data inertial reference unit (ADIRU)/FMC gross error check.
• Navigation source validation.
c. Gross Error Check. Russian airspace requires an ADIRU/FMC gross error check prior to entering regardless of whether you consider the routing Class I or Class II Navigation.
d. NAVAIDs in Asia. Both VORs and NDBs may not operate continuously. An asterisk (*) preceding the frequency indicates that they may be off the air. Thus, if a NAVAID appears to be off the air, operators may make a request to the controller to reinstate operations. NDBs shown on the en route chart with an underlined alpha identifier (e.g., ABC) require the addition of a “B” (for BFO (beat frequency oscillator)) to the frequency (e.g., 321B) for proper tuning on the NAV/RAD page.
e. RNP-10. RNP of 10 NM is the standard for operating along routes between North America and Japan where 50-mile lateral separation applies. This includes the Pacific Organized Track System (PACOTS) and most of the NOPAC routes.
f. RNP-4. RNP of 4 NM is now available in Oakland airspace for properly-equipped aircraft that have the required authorizations. This is the standard for the 30-mile lateral and longitudinal separation.
5-4. SURVEILLANCE.
a. Automatic Dependent Surveillance-Contract (ADS-C). ADS-C is an Air Traffic Service (ATS) application established by contract in which aircraft automatically transmit, via data link, data derived from onboard navigation systems. As a minimum, the data includes a 3-D position, the corresponding time of the position data, and a Figure of Merit that characterizes the accuracy of the position data. You may provide additional data as appropriate.
b. ADS Data. It uses the various systems aboard the aircraft to provide aircraft position, velocity, intent, and meteorological data. The aircraft can transmit this data to the ATS provider system for estimating and predicting aircraft position.
c. ADS-C Reports. The ATS provider applies a contract request to an aircraft. ADS-C reports are issued by the aircraft per the contract request. The contract identifies the types of information and the conditions that the aircraft transmit.
d. Contract Types. A periodic contract, event contract, and demand contract all define three types of reporting. The aircraft may also initiate emergency reporting, which is a special case of periodic reporting. In response to a periodic contract, the aircraft assembles and transmits a message containing the fields at the interval specified in the contract request. Event contracts define certain events (such as an altitude change), which causes the aircraft to send a report, independent of any periodic contract in effect. Send one demand contract each time the ATS provider system commands it. The contract request may specify several different data groups.
These include the basic position report, which contains 3-D position and time, and additional on-request groups. These groups include aircraft and wind velocity, vertical speed, and limited waypoint information.
e. ATS Provider Capabilities. They may issue multiple simultaneous contracts to a single aircraft, including one periodic and one event contract. Any number of demand contracts may supplement one periodic and one event contract. Up to four separate ATS provider systems may initiate ADS-Cs simultaneously with a single aircraft.
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