• www.faa.gov/air_traffic/publications/ifim/.
• http://www.paris.icao.int.
g. Warning Areas. International airspace has established warning areas to contain operations hazardous to non-participating aircraft. The FAA and the military may jointly use some of these areas. The FAA will issue instrument flight rules (IFR) clearances through these areas whenever hazardous operations are not taking place. Carefully review charts for those areas while flight planning, taking note of the area operating times and restrictions.
NOTE: Operators are also responsible for knowing the requirements for prohibited and restricted airspace in oceanic operations.
h. Altimeter Settings. Operations in international airspace demand that pilots are aware of, and understand the use of, the three types of altimeter settings.
NOTE: Most overseas airports give altimeter settings in hectopascals (hPa) (millibars). Therefore, it is imperative that pilots are able to convert inches of mercury to hPa or hPa to inches of mercury.
(1) Altitude Above Ground (QFE). A local altimeter setting equivalent to the barometric pressure measured at an airport altimeter datum, usually signifying the approach end of the runway is in use. At the airport altimeter datum, an altimeter set to QFE indicates zero altitude. If required to use QFE altimetry, altimeters are set to QFE while operating at or below the transition altitude and below the transition level. On the airport, the altimeter will read “0” feet.
(2) Barometric Pressure for Standard Altimeter Setting (QNE). Use the altimeter setting (en route) at or above the transition altitude (FL 180 in the United States). The altimeter setting is always 29.92 inches of mercury/1013.2 hPa for a QNE altitude.
NOTE: Transition levels differ from country to country and pilots should be particularly alert when making a climb or descent in a foreign area.
(3) Barometric Pressure for Local Altimeter Setting (QNH). A local altimeter setting equivalent to the barometric pressure measured at an airport altimeter datum and corrected to sea level pressure. At the airport altimeter datum, an altimeter set to QNH indicates airport elevation above mean sea level (MSL). Altimeters are set to QNH while operating at and below the transition altitude and below the transition level.
(a) For flights in the vicinity of airports, express the vertical position of aircraft in terms of QNH or QFE at or below the transition altitude and in terms of QNE at or above the transition level. While passing through the transition layer, express vertical position in terms of FLs when ascending and in terms of altitudes when descending.
(b) When an aircraft that receives a clearance as number one to land completes its approach using QFE, express the vertical position of the aircraft in terms of height above the airport elevation during that portion of its flight for which you may use QFE.
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i. Reporting of Operational and Meteorological Information. When an aircraft en route reports operational and/or routine meteorological information at points or times that require position reports, give the position report in a format that ATC requires.
j. National Security. Title 14 CFR part 99 governs national security in the control of air traffic. Following the events of September 11, 2001, the threat of terrorism has brought about numerous changes to security protection procedures in the United States. The FAA expects many additional changes in the United States and internationally will take place and operators should check the latest AIP and all NOTAMs to ensure compliance with security requirements.
Additionally, operators intending to operate in or cross any United States air defense identification zone (ADIZ) should make a detailed review of part 99 and the IFIM.
k. International Interception Procedures. There are occasions that require pilots to transmit instructions to pilots of intercepted aircraft. ICAO Annex 2, chapter 3, paragraph 3.8, and attachment A contains guidance for international interception procedures. Appendix 1 of Annex 2 contains international interception signals.
3-4. OCEANIC COMMUNICATIONS. Radio frequencies are constantly changing. Thus, it is important that operators consult current oceanic charts and the FAA Website at www.faa.gov/air_traffic/publications/ifim/ for the most up-to-date information.
a. Data Link Communications. We base data link requirements on ICAO standards (for additional guidance, see AC 120-70A, Operational Authorization Process for Use of Data Link Communication System, current edition). Operators should consult geographic-specific areas of this document. Operators can also consult the Future Air Navigation System (FANS) Operation Manual for data link procedures and operations.
b. Satellite Communications (SATCOM) Voice. The current requirements for remote oceanic operations are two HF radios. At this time, non-routine and emergency purposes only allow SATCOM Voice. As this technology evolves, operators must ensure that they comply with the latest authorizations.
c. In-flight Broadcast Procedures. Some remote geographic regions of the world, which provide only limited communication and ATS, require the pilots’ understanding and regular use of in-flight broadcast procedures.
(1) Navigation Charts. Commercially-published navigation charts contain details of communication procedures on inserted panels. In addition, the North Atlantic Systems Planning Group (NAT SPG) publishes the North Atlantic MNPS Airspace Operation Manual, which is available on the following Web site: www.paris.icao.int/. This North Atlantic MNPS Airspace Operations Manual details all aspects of North Atlantic Operations (NAT/OPS) and includes communication and navigation procedures. The guidance and information material contained here concerns flight operations in the NAT region. It deals primarily with approval for operations in the NAT region and with the planning and management of such operations. It addresses mainly state aviation authorities/administrations and ATS Provider States and Operators.
(2) Operation Manuals. Some of the material in this document is of interest to pilots;
however, more detailed information for pilots is in the North Atlantic MNPS Airspace
Operations Manual (issued by the European and North Atlantic (EUR/NAT) Offices of ICAO) and in the North Atlantic International General Aviation Operations Manual (issued by the FAA). NAT SPG, on its behalf, produce these two manuals. Although primarily intended for use by pilots, it is important that the operators use the manuals to ensure that flightcrews, for whom they are responsible for, have adequate training and equipment for NAT/OPS.
NOTE: You can download the North Atlantic International General Aviation Operations Manual from the FAA Web site at www.faa.gov/atpubs.
d. Summary of Communication and Reporting Procedures. Maintain continuous contact with the controlling agency. This can be through VHF, HF, data link, SATCOM Voice or Selective Call (SELCAL). The range of VHF is approximately 200 NM; communication beyond that distance requires HF or SATCOM data link. A family of frequencies is normally assigned based on route and/or the state where the aircraft is registered. En route charts list these families of frequencies.
e. Emergency Frequencies.
• VHF: 121.5.
• Ultrahigh frequency (UHF): 243.0.
• HF: 2182/4125.
3-5. NAVIGATION PROCEDURES (NAVIGATION SENSORS—INERTIAL NAVIGATION SYSTEM (INS), INERTIAL REFERENCE SYSTEMS (IRS), OR GNSS).
a. Journey Logbooks. ICAO Annex 2 requires the use of a journey logbook, also known as the “master” document. This “master” document is typically a computer flight plan (CFP).
Operator procedures must include a designated “master” document for use on the flight deck.
This document must include information that sequentially lists the waypoints that define the routes, distances between the waypoints, and any other navigation information pertinent to the cleared route. Misuse of the master document can result in serious navigational errors.
b. Application of Master Document. Strict procedures should be used in the management of this document. These procedures should include the following:
NOTE: These procedures are general; operators should consult specific guidance based on the type of long range navigation system (LRNS) configuration.
• Use only one copy of the master document in the cockpit.
• Use a waypoint/numbering sequence procedure from the outset of the flight. Enter this sequence on the master document and also use it to store waypoints in the navigational computer. Adopt the appropriate symbology to indicate the status of each waypoint listed on the master document. For example:
• Verify the waypoints by comparing the master document and the LRNS;
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• Circle the waypoint, waypoint number, or symbol to signify that another crewmember independently cross-checks the entry of the coordinates in the navigation computer;
• Tick or diagonally slash the circled waypoint, waypoint number, or symbol to signify the cross-checking of track and distance information within a specified tolerance; and NOTE: Some operators use a diagonal line approaching a waypoint to confirm a subsequent waypoint to include coordinates, track, and distance.
• Cross out the circled waypoint, waypoint number, or symbol to signify that the aircraft has passed the waypoint. Pilots must verify all navigational information contained in the master document against the best available primary data source.
Cross out old waypoints and insert the new information.
• If they receive an ATS route change or the ATC clearance changes, pilots must update the master document to reflect the change.
• While obtaining ATC clearances, it is recommended to wear headsets because loudspeaker distortion is known to result in errors. Two qualified crewmembers must monitor and independently verify all clearances received. The crew should read all waypoint coordinates back in detail unless approved local procedures make this unnecessary. In that case, cross-check each detail with the master document.
3-6. POSITION PLOTTING.
a. Plotting and Systematic Cross-Checking of Navigation Information. During all phases of flight in Class II navigation, each operator’s long-range navigation program (LRNP) will require the standardized application of disciplined, systematic cross-checking of navigation information.
(1) Plotting Procedures Impact. Plotting procedures have had a significant impact on the reduction of gross navigation errors (GNE). There is a requirement to plot the route of flight on a plotting chart and to plot the computer position approximately 10 minutes after waypoint passage. This may or may not require plotting, depending upon the distance between the standard ICAO ground-based NAVAIDs. This applies to all operators.
(2) Turbojet Operations. All turbojet operations, where the route segment between the operational service volume of ICAO standard ground-based NAVAIDs exceeds 725 NM, require plotting procedures.
(3) Turboprop Operations. All turboprop operations, where the route segment between the operational service volume of ICAO standard ground-based NAVAIDs exceeds 450 NM, require plotting procedures.
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(4) Plotting Procedures for Special Conditions. The Administrator requires plotting procedures for routes of shorter duration that transit airspace where special conditions exist, such as reduced lateral and vertical separation standards, high density traffic, proximity, or potentially hostile border areas.
(5) Reviewing and Revising Approvals. Review and revise any existing approvals that differ from the plotting requirements in this chapter and Class II navigation procedures as necessary. Direction and guidance is available from the navigation specialists in coordination with AFS-400.
(6) Plotting Charts. The FAA requires crews to use a plotting chart to provide themselves with a visual presentation of the intended route. Regardless of the type of LRNS in use, operators must use plotting charts. Plotting the route will increase SA and reveal errors or discrepancies in the navigational coordinates that flightcrews can correct before such errors can cause a deviation from the ATC cleared route. As the flight progresses, plotting the position approximately 10 minutes after passing each waypoint helps confirm that the flight is on course.
If the plotted position indicates off track, the flight may have deviated unintentionally and the flightcrew should investigate at once.
(7) Plotting Chart Requirements. The plotting chart must include, at a minimum:
• The route of the currently effective ATC clearance;
• Clearly depicted waypoints using standardized symbology; and
• Ten-minute plotted positions after passing each oceanic waypoint, including coordinates, time, and graphic depictions of all ETPs.
NOTE: Operators’ SA should include such items as alternate airports and proximity of other tracks.
b. Human Factors Issues for Confirmation of Currently Effective ATC Clearance.
When cross-checking the LRNS entries or the plotting chart entries, pilots should read from “entered” data back to the master document.
c. Relief Crewmembers. Flightcrews conducting long-range operations may include a relief pilot. In such cases, crews must ensure the continuity of the operation and brief the relief pilot on all current operational issues affecting the flight.
d. INS/IRS/Inertial Reference Units (IRU) System Alignment. Complete INS alignment and switch the equipment to “nav” mode prior to releasing the parking brake at the ramp. There are various ways of ensuring that there is adequate time for this operation.
(1) Align Mode. Have the first crewmember on the flight deck place the system in “align” mode as early as possible. At short transit stops, leave the equipment in “nav” mode provided that the system errors are not so large as to require INS realignment. The decision to realign may depend on the size of the error as well as the length and nature of the next leg. You cannot recharge INS batteries, which usually have a limited-life, onboard if allowed to run down.
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(2) Monitor Ground Power Interruption. If the INS is left in “nav” mode during a transit stop, or if you switch the INS on for alignment, it is imperative that an individual is responsible for monitoring ground power interruption.
(3) Overheat Protection. Some INS systems provide overheat protection in “standby” and “align,” but not in other modes.
(4) Align at Tropical Terminals. During stops at tropical terminals, put the mode selector directly to “align” (not through “standby,” which would cause realignment).
e. Initial Insertion of Latitude and Longitude. Early in the course of the preflight check, load the aircraft’s position into the INS and verify. Check this position against an authoritative reference source before insertion. Any latitude error in the initial position will introduce a systematic error that you cannot remove during flight by updating, resulting in erroneous position indications. Check for a correct insertion of present position before the “align” mode is selected and the position is recorded in the master document. Subsequently, both pilots independently make silent position checks during an early stage of the preflight check. In the case of some INS, insertion errors exceeding 1º of latitude will activate a malfunction light.
However, very few systems provide similar protection against erroneous longitudinal insertion errors. At all times, take care to ensure that previously inserted coordinates are correct.
f. Verification of Present Position/Initial Position. Regardless of the type of LRNS or the method of insertion, crews will verify current ramp position in the LRNS against current aeronautical publications.
g. INS Loading of Initial Waypoints. Two people working in sequence and independently must conduct the entry of waypoint data into the navigation system as a coordinated operation. One should key in the data and the other person should recall and confirm the data against source information. It is not sufficient for one crewmember to simply observe another crewmember entering the data. The pilots should use waypoint 1 for the ramp position of the aircraft. The pilots should load at least two additional waypoints while the aircraft is on the ramp or they may load all waypoints at this time. However, it is more important to ensure that the second waypoint is inserted accurately than to attempt to load all waypoint data. The second waypoint should associate with the first significant position along the route (approximately 100 NM from departure point). Positions associated with ATC standard instrument departures (SID) should not normally be used for this purpose. During flight, the control display unit (CDU) should maintain at least two current waypoints beyond the navigated sector until the pilots load the destination ramp coordinates. The pilots should be responsible for loading, recalling, and checking the accuracy of the loaded waypoints. Each pilot should cross-check the other’s work.
In no case should this process engage the attention of both pilots simultaneously during flight.
An acceptable procedure is for the pilots to independently load their own waypoints and then cross-check them. The pilot responsible for verification should work from the CDU display to the master document, lessening the risk of seeing what is expected rather than the actual information. After the pilots load the initial waypoints, they should select the route between waypoints 1 and 2 and the auto track change.
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h. INS Flight Plan Check. The purpose of the flight plan check is to ensure complete compatibility between the master document and the programming of the navigation system. To verify the correct distance from the ramp position to waypoint 2, select “dis/time.” You may have to consider an appropriate allowance since the great circle distance shown on the CDUs may be less than the flight plan as a consequence of the additional mileage involved in ATC SIDs. However, a significant disparity requires a recheck of “pos” and waypoint 2 coordinates:
• Select “remote” and track change 1-2. Check the accuracy of the indicated distance against that listed in the master document.
• Select “dstrk” and check that the desired track indicated on the CDU is the same as that in the master document. This track check will reveal any errors in the latitude and longitude designators.
• Perform similar track and distance checks for subsequent pairs of waypoints and any discrepancies between the CDU information and the master document.
Coordinate these checks against the master document between themselves.
• After checking each leg of the flight as described above, make a note on the master document using the appropriate symbols.
i. INS Procedures Leaving the Ramp. If the aircraft moves before initiating the “nav” mode, realign the INS. Relocate the aircraft so that it does not block the gate or otherwise interfere with traffic while the realignment takes place. After leaving the ramp, check INS groundspeeds. Perform a check of the malfunction codes while the aircraft stops but after it has taxied at least part of the way to the takeoff position. Any significant groundspeed indication while stationary may indicate a faulty unit.
j. In-flight. If you conduct the initial part of the flight along airways, the flightcrews should use the airways facilities as the primary NAVAIDs and monitor the aircraft navigation system to ascertain which system is giving the most accurate performance.
k. Approaching the Ocean. The FAA requires crews to verify the accuracy of the LRNS before entering Class II airspace. Crews must complete the accuracy verification (without updates) using ground-based NAVAIDs. The crew will conduct the gross error check of the LRNS in Class I airspace. The crew may use an ATC radar plot to verify the gross error check. The crew will record the coordinates and the time of the gross error check.
(1) Aircraft Position Check with NAVAIDs. Before entering oceanic airspace, check the aircraft’s position as accurately as possible by using external NAVAIDs to ascertain which aircraft navigation system to use. This may require DME and/or VOR/DME checks to determine navigation system errors through displayed and actual positions.
(2) Updating Navigation the System. In the event of significant discrepancies (greater than 2 NM), consider updating the navigation system. We do not normally recommend updating when the discrepancy is less than 6 NM.
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(3) Influential Factors in System Updating. The duration of the flight before the oceanic boundary and the accuracy of the external navigation system are factors that influence any decision to update the system. If the system received an update, follow the proper procedures with the aid of a prepared checklist.
(4) Auto-Coupling. Select the navigation system that performs the most accurately for auto-coupling. In view of the importance of following the correct track in oceanic airspace, some operators advise that the third pilot or equivalent crewmember should check the inserted waypoints using appropriate source information.
l. Oceanic Entry. Crews must ensure they have given an accurate estimated time of arrival (ETA) to ATC for their oceanic entry point. They must also ensure they entered the ocean at the cleared FL.
m. Oceanic Boundary Position Report. Just prior to the oceanic boundary and prior to any waypoint, the crew should monitor, record, and verify the present position coordinates.
Check and verify the coordinates for the next waypoint. When the CDU alert light comes on, the crew should note and record the present position on the master document. Verify this information against the current clearance on the master document. Annotate the waypoint number on the master document with the appropriate symbol to indicate its verification. If you make the oceanic boundary position report over a VOR facility, select the appropriate radial to the first oceanic waypoint as a further check shows that the navigation system is tracking according to the current clearance. If DME is available, you can also perform a distance check.
n. Approaching an Oceanic Waypoint. Two minutes before reaching each oceanic waypoint, crews should verify the accuracy of the subsequent waypoint. This verification should include the expected outbound course and distance of the currently effective ATC clearance.
o. At Each Oceanic Waypoint. Crews must ensure that when overhead each oceanic waypoint, the aircraft turns to the anticipated heading and that the distance to the next waypoint is accurate. Verify the coordinates of the next waypoint against the master document. After the ATC position report is sent, plot the present position to ensure that the tracking is correct. The crew should be particularly alert in maintaining SELCAL watch in the event of possible ATC followup to the position watch.
NOTE: Crews must not assume the aircraft has automatically transitioned to the next waypoint.
p. Ten-Minute Position Plotting. Approximately 10 minutes after transitioning each oceanic waypoint, crews will plot their LRNS position and note the coordinates and time on the plotting chart. When sending the ATC position report, copy the coordinates from the master document or the present position and you can read the next two forward positions from the CDU.
As soon as the waypoint alert light goes on, check the present position coordinates of each navigation system against the current clearance to ensure that the position report coincides with the actual position of the aircraft and the ATC clearance.
q. Routine Monitoring. Operators must ensure they have procedures in their International Operations Manual concerning which page(s) the PIC will routinely monitor versus the pages the Page 32 Par 3-6
SIC routinely monitors. For example, the PIC may monitor the cross-track error (XTK) page and the second in command (SIC) may monitor distance/time.
(1) Position Coordinates. There are a number of ways in which you may accidentally disconnect the autopilot (AP) from the command mode. Crews should make regular checks of correct engagement. Although it is a common practice to display “dist/track,” the FAA recommends that the navigation system coupled to the AP display the present position coordinates throughout the flight. If plotting the coordinates at roughly 20-minute intervals, they will confirm that the flight is on track according to the ATC clearance. Distance-to-go information should be available on the instrument panel, and the waypoint alert light provides a reminder of the proximity of the waypoint.
(2) XTK and Track Angle Error (TKE). If a crew makes a position check and verification at each waypoint and 10 minutes after each waypoint, additional plotting every 20 minutes may be counterproductive during routine flight. The navigation equipment not used to steer the aircraft should display XTK and TKE. Monitor these indicators with XTK displayed on the horizontal situation indicator (HSI) when feasible.
r. Use of Radar. Aircraft equipped with airborne weather radar capable of ground mapping should use the radar to observe any land masses as an aid to determining the accuracy of their navigation. The flightcrews must use the radar on a constant basis during flight to monitor navigation system accuracy.
s. Approaching Landfall. When the aircraft is approaching the first landfall NAVAID, it should acquire the appropriate inbound radial as soon as the flightcrew is confident that the NAVAID information is accurate.
t. Navigation System Accuracy Check. At the end of each flight, determine the accuracy of the navigational system to facilitate correction of performance. You may perform a check to determine the radial error at the ramp position as soon as the aircraft parks. Radial errors for INSs in excess of 2 NM per hour are generally considered excessive (part 121, appendix G).
Keep records on each individual navigation system performance.
u. Monitoring During Distractions. Training and drills ensure that minor emergencies or interruptions of normal routine do not distract the crew to the extent of mishandling the navigation system. If the AP disconnects during flight, re-engage it carefully to ensure that you follow the correct procedure.
v. Avoiding Confusion Between Magnetic and True. To cover all navigation requirements, some air carriers produce flight plans that include both magnetic and true tracks. If crews are changing to a new system, there is a risk of confusion in selecting the correct values.
Operators should devise drills to reduce this risk and ensure that training covers this subject.
Crews that check or update their LRNS by reference to VORs located in the Canadian Northern Control Area (NCA) should remember to not align them with reference to magnetic north.
w. Navigation in Areas of Magnetic Unreliability (AMU). The FAA designates Canada’s NCA and Arctic Control Area (ACA) as AMUs. Although Canadian publications sometimes refer to it as the area of compass unreliability, they are the same. The magnetic North Par 3-6 Page 33
Pole is at approximately 75°N 100°W and is slowly moving as it circles the true pole every 960 years. This is why we see current navigation charts occasionally changing an instrument landing system (ILS) course by 1º.
(1) Magnetic North Pole. When you approach the magnetic North Pole, horizontal magnetic influences decrease and vertical magnetic influences increase to a point where the compass is no longer reliable (the magnetic pole is below the aircraft). It is common to see the compass drifting aimlessly or tilting in its case due to the vertical component even when hundreds of miles from the magnetic North Pole. The better the magnetic compass, the closer to the magnetic pole it will operate. Within about 250 miles of the magnetic pole, all aircraft magnetic compasses will be useless. As a result, some VORs, runways, and radar vectors in Canada’s NCA and ACA are oriented to true north.
(2) AMU. When operating in the AMU, move the HDG REF switch to TRUE when the Canada HI 4 chart defines the course with a °T. Add two additional items to the master flight plan checklist: TRUE HDG adjacent to the first true heading leg and MAG HDG at the end of the AMU. This will serve as a reminder to return to a normal heading reference. The primary reason for selecting TRUE HDG in the NCA and ACA is to provide a more realistic navigation display (ND) heading presentation, thus avoiding rapidly changing heading indications. This will help with radar vectors in TRUE and comply with Canadian Air Regulations.
x. Navigation in Areas of Convergence. Because of the rapid changes in variation and due to meridian convergence, you may note a considerable difference between the flight plan course and the flight management computer (FMC) course when conducting the Class II navigation checks. The flight plan entry consists of the average for the leg while the FMC displays the course at the start of the leg. If a significant difference exists between the two, then you can confirm the course by checking it in TRUE, which will eliminate the large changes in variation. In the far north, convergence is so great that even in TRUE there may be a considerable difference between the flight plan and the FMC. If this is the case, check the FMC against the Canada HI 4 chart. The course at the start of the leg on the chart should agree with the FMC. If averaging the outbound and inbound courses of the leg on the Canada HI 4, the result should closely agree with the flight plan.
NOTE: The direct route from Thule to Cambridge Bay in a southwesterly direction begins on a course of 254°T and ends on 219°T. This is a 35° change because of convergence. The variation at Thule is 66°W and the variation at Cambridge Bay is 25°E. This results in a magnetic course of 320°M departing Thule and a 194°M course arriving over Cambridge Bay. This change of 126°M is due to the effects of convergence and variation while flying a great circle route. It is evident that even though the flight in this example is south of 82°N, select a true heading reference, thus allowing a more realistic heading presentation. If this were flown as a single leg, it would be necessary to do the Class II course check using the Canada HI 4 chart as described above in order to get a valid check. The FMC in TRUE should closely agree with the charted outbound course of 254°T and the flight plan should closely agree with the average of 254°T outbound and 219°T inbound, which is 236°T.
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y. Weather Deviations. Temporary diversions from track are sometimes necessary, but obtain prior ATC clearance. Such diversions can cause GNEs if you do not re-engage the navigation mode of the AP. Selection of the AP turbulence mode (if applicable) can disengage the AP from the navigation system. After using turbulence mode, fly the aircraft back to the desired track before re-engaging the AP. For inertial platform aircraft, the following steps are useful in preventing GNEs as a result of diversions around severe weather:
• Use the AP turn control knob to turn the aircraft in the desired direction.
• The AP engage switch will automatically move from “command” to “manual.”
• The altitude mode switch will either remain on “altitude hold,” or if in the “altitude select” mode, will trip to “off.”
• Set the steering CDU selector to XTK/TKE to provide a continuous display of cross-track data.
• If encountering turbulence, you may use the “turb” setting on the speed mode selector. In this case, the altitude mode switch automatically positions to “off.”
• Both radio INS switches remain in the INS position. This provides a visual display of the navigation situation on the HSI. Even if more than 8 NM off the track, the pegged needle on the HSI is a reminder of that fact and confirms whether the aircraft is tracking towards, away from, or parallel to the desired track.
• Use the turn control knob to maneuver the aircraft as necessary.
• When clear of the severe weather, steer the aircraft back to the desired track, guided by the steering CDU to zero the XTK indication.
• When the aircraft returns to the desired track, set the AP engage switch to “command” and the altitude mode switch to “altitude hold.” The navigation mode selector should still be in the INS position.
• The captain and first officer, or the entire crew if possible, should monitor the diversion maneuver to ensure that the aircraft has returned to the desired track and if you properly re-engaged the AP for command INS operation.
• After completing return to route, check the assigned Mach number and advise ATC.
z. ATC Re-Clearance. Scrutiny groups determined that a re-clearance scenario is the greatest contributor to an oceanic error (e.g., GNE, Large Height Deviation (LHD)). Experience suggests that when ATC issues a clearance involving rerouting and new waypoints, the risk of error increases. The procedures used to copy the ATC clearance, load and check the waypoints, verify the flight plan information, and prepare a new plotting chart should be the same as the procedures for beginning a flight. Designate one pilot to fly the aircraft while the other pilot reprograms the navigation systems and amends the cockpit documents. In the event that a Par 3-6 Page 35
re-clearance involves a direct routing, retain the data relevant to the original route in case ATC requires the aircraft to return to its original course.
aa. Detecting Failures. Inertial and global positioning system (GPS) installations typically include comparator and/or warning devices, but the crew must still make frequent comparison checks. With three systems onboard, identification of a defective system should be straightforward. Identifying system failures with two systems is more difficult. If a significant deviation occurs in oceanic airspace, contact nearby aircraft on 123.45 MHz and obtain information to aid in identifying a system failure. Maintain and keep a record of GPS or inertial performance available for crews. The following are suggestions for recordkeeping:
• Before takeoff and while stationary, note the inertial groundspeed and position indicators. These may give an indication of system accuracy.
• Note the accuracy of each unit before reaching oceanic airspace, preferably while passing a convenient short-range facility. Make a further record at the destination regarding terminal error after first canceling any in-flight updates made.
• You can make compass deviation checks (inertial only) to determine deviation values for the magnetic compass systems so that you can check the accuracy of the inertial heading outputs in-flight.
bb. Identifying Faulty Systems.
• Check malfunction codes for indications unserviceability.
• Refer to records for indications of prior problems.
• Obtain a fix, possibly using the weather radar, in order to determine position relative to information from other systems.
• Communicate with nearby aircraft on air-to-air VHF to compare information on spot wind, groundspeed, and drift. Compare information from the prognostic chart to the system readout if there is no contact with any aircraft. Use this method as a last resort and preferably should use it with another method of verification.
• Use the heading method (inertial only). Simultaneously read both the inertial and magnetic compass indicators. Obtain the mean to the nearest degree to get an acceptably accurate true heading value to compare to the inertial readings and determine what reading is inaccurate.
• Situations may arise when distance or cross-track differences develop between two LRNSs, but the crew cannot identify the faulty system. If three systems are onboard, accept the two agreeing systems as reliable signals. If, however, only two systems are onboard and they disagree, most operators believe that the best procedure in this instance is to fly the aircraft halfway between the cross-track Page 36 Par 3-6