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l. Approaching Waypoint. Within 2 minutes of each waypoint, both pilots should verify that the subsequent waypoint in the ND agrees with the current ATC clearance. Cross-check coordinates of the approaching waypoint and subsequent waypoints. Compare zone distance on the flight plan to that displayed on the navigation computer for the next leg. Compare computer flight plan ETA with ETA information displayed in navigation computers. (On some systems, you may accomplish this cross-check more easily during waypoint passage.)
m. After Passing Each Waypoint. Approximately 10 minutes after passing each waypoint, plot the present position information on the NDs on a navigation chart to confirm that the ATC clearance is satisfied. Confirm that the navigation systems have switched to the next flight segment (leg change). Verify that the aircraft is tracking along the next flight segment (tracking outbound).
n. Approaching the Inbound Gateway. Make certain preparations for the transition from long-range navigation to airways navigation. The FAA recommends the following practices:
• As soon as feasible, set up the navigation radios to receive the inbound gateway NAVAID.
• When the gateway NAVAID is providing reliable information, place the “radio/nav” switch in the “radio” position and steer the aircraft to acquire and maintain the proper inbound radial/bearing.
• Unless otherwise directed by ATC, fly the aircraft directly over the gateway.
• When over the gateway, record the position information from the navigation displays (ND). You can use this information to confirm system accuracy. Compare VOR, VOR/DME, NDB course and distance information with that displayed in navigation computers. The FAA recommends that you make system accuracy computations after arrival to avoid conflicts with other cockpit duties during the critical periods of descent, approach and landing.
o. After Arrival. Compute and record the individual navigation system errors and error rates (if applicable) for future reference. It is desirable to record this information in a document that remains aboard the aircraft to provide subsequent flightcrews with a recent history of system performance. This information may be used with most systems to predict individual system performance for future flights under similar circumstances. Additionally, this information may prove valuable to subsequent flightcrews for resolving navigation abnormalities, such as divergence between systems.
10-3. LRNS PROBLEMS AND RECOMMENDED ACTIONS. Although the accuracy and reliability of the newer navigation systems are excellent, malfunctions and failures occasionally occur. When a malfunction occurs, flightcrews should guard against jumping to conclusions since hasty actions are seldom necessary and may further complicate the situation. Experience has shown that successful resolution of navigation difficulties in oceanic areas usually requires a thorough, thoughtful process that normally begins during preflight planning.
The training program manuals and check airman program for air carrier operations should emphasize procedures followed in the event of partial and total instrument failure. Non-air carrier operators should be able to demonstrate this emphasis in their training programs if requesting an LOA for oceanic operations in special airspace. The following guidance is for consideration when encountering or suspecting navigation difficulties.
a. Navigation Errors. Monitoring procedures used during oceanic operations indicate the frequency and course of navigation errors. Considering that operators make thousands of flights, errors are actually rather infrequent. Navigation systems are generally so reliable that there is some concern about overconfidence. Therefore, crews should guard against complacency.
(1) Frequent Causes of Errors. Frequent causes of errors include the following:
• Making a mistake of 1° of latitude when inserting a forward waypoint.
• The crew received re-clearance by ATC but forgot to re-program the navigational system.
• The operator left the AP in the heading or de-coupled position after avoiding severe weather or they left it in the VOR position after departing the last domestic airspace VOR. In some cases, this occurred after distractions by selective calling (SELCAL) or flight deck warning indications.
• The controller and crew had different understandings of the clearance because the pilot heard what he/she wanted to hear rather than what they actually said.
(2) Rare Causes of Errors. Rare causes of errors include the following:
• The latitude/longitude coordinates displayed at the gate position were incorrect.
• Because of a defective chip in an aircraft system, and although the crew inserted the correct forward latitude, it “jumped” 1°. (INS only.)
• The aircraft has an advanced system that includes all waypoint coordinates already in the database equipped. The crew assumed the coordinates were correct, but one was not.
• Although the crew had the correct coordinates available, the information inserted into the system was from an incorrect company flight plan.
b. Detection of System Failure. In general, we usually consider system failure to have occurred when one of the following situations develop:
• Activation of a warning indicator that cannot be reset;
• Self-diagnostic or built-in test equipment (BITE) indicates that the system is unreliable;
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• The position error over a known geographic location exceeds the maximum permissible tolerance established for a particular navigation system; or
• The system’s operation is so abnormal that, despite the absence of warning or malfunction indications, the flightcrew considers the system no longer useful for navigation.
c. Detection of System Degradation or Malfunction.
(1) Identifying a Faulty System. While system failures are usually straight forward, malfunctions or gradual system degradations are usually more difficult to detect. This is particularly true when only two systems are onboard. A divergence between the navigation systems, a situation that often occurs gradually, usually detects navigation difficulties of this type. This factor may reduce the possibility of identifying the faulty system unless operators diligently use periodic cross-checking practices. Consider the following factors when attempting to identify a faulty system:
• Check the BITE codes for indications of system fault.
• Review the gateway gross error check for indications of the most accurate system.
• If you maintain a regular record of system performance and it is available, a review of the record may give a clue as to which system is faulty.
• If possible, use VOR, automatic direction finder (ADF), DR, airborne radar, or other NAVAIDs to obtain a position fix.
• Cross-check heading, groundspeed, track, and wind information between systems and compare this information with the best known positive information such as position over a fix.
• Attempt to contact nearby aircraft to obtain wind or groundspeed and drift correction information that may identify the malfunctioning system.
• The compass deviation check may provide a clue as to which system is faulty for systems such as INS.
(2) Determining a Faulty System. Even though you take these steps, a divergence between systems may occur, but the flightcrew may be unable to determine which system is at fault. When this occurs, use the practices described in the following paragraph.
d. Recommended Actions Following System Failure. After detecting a system malfunction or failure, inform ATC that the flight is experiencing navigation difficulties so that you can adjust the separation criteria, if necessary. Reporting malfunctions to ATC is an ICAO requirement and 14 CFR part 91 requires compliance. If you can identify the failed system with a high degree of confidence and the other system appears normal, the best course of action may be Par 10-3 Page 123
Page 124 Par 10-3 to fly the normal system and carefully monitor its performance using any additional NAVAIDs available. In the unlikely event that a total navigation failure occurs and other aids are unavailable, the only action may be to fly by contingency DR using the flight plan headings and times. Under these circumstances, flightcrews should continue to use all means available to obtain as much navigational information as possible. Flightcrews should be alert for visual sightings of other aircraft, since a hazard may exist due to an inadvertent deviation from the assigned track. In some cases, it may be possible to establish and maintain visual contact with another aircraft on the same track.
e. Recommended Action Following a Divergence Between Systems. Since a small divergence between systems may be normal, evaluate the significance of the divergence. In general terms, if the divergence is less than 10 NM, the best course may be to closely monitor system performance and continue to steer the system considered most accurate. If the divergence between systems is greater than 10 NM, it may degrade one of the systems. Therefore, make attempts to determine which system may be faulty. If you cannot determine the faulty system using the practices described in this section, and both systems appear normal, the action most likely to limit gross tracking error may be to position the aircraft so that the actual track is midway between the cross-track differences for as long as the position uncertainty exists. Advise ATC that you are experiencing navigation difficulties so that you may adjust separation criteria as necessary. Give consideration to abandoning this “split-the-difference” practice if the divergence exceeds the separation criteria currently in effect on the route of flight. If a divergence of this magnitude occurs and you cannot isolate the faulty system, the best course may be to fly by contingency procedures using the best known wind information. However, in some cases, the best known information may be flight plan headings and times.
10-4. PROVING TESTS AND VALIDATION FLIGHTS. Title 14 CFR parts 121 and 135 require evaluation of an operator’s ability to conduct operations safely and in accordance with the applicable regulations before issuing an operating certificate or authorizing a certificate holder to serve an area or route. The testing method used by the FAA to determine an operator’s capabilities are validation flights. Sections 121.93, 121.113, and 135.145 require an operator to demonstrate the ability to conduct operations over proposed routes or areas in compliance with regulatory requirements before receiving FAA authority to conduct these operations. The FAA requires validation flights for authorization to add any areas of operation beyond the continent of North America and Mexico, and before issuing authorization for special means of navigation.
Though proving tests and validation flights satisfy different requirements, it is common practice for operators to conduct both tests simultaneously. However, validation flights are important to consideration of oceanic operations (14 CFR part 119, § 119.59).
a. Validation Flights. Sections 121.93, 121.113, and 135.145 require operators to show the capability to conduct line operations safely and in compliance with regulatory requirements before receiving authorization to conduct those operations in revenue service. The most common method of validating an operator’s capability is to observe flight operations. The FAA normally requires validation flights before issuing OpSpecs granting authority to conduct operations beyond the populated areas of the North American (NAM) continent. When the FAA conducts a validation flight, they conduct an in-depth review of the applicable portions of the operator’s proposed procedures, including flight following, training programs, manuals, facilities, and maintenance programs. There are four situations that require validation flights in association
with approval of Class II navigation: initial approval; addition of an LRNS or a flight navigator;
operations into new areas; and addition of special or unique navigation procedures. Validation flights are required when an operator proposes to conduct operations that require confirmation of the ability to operate an aircraft type within specified performance limitations. These limitations are based on the character of the terrain, extended over-water, the type of operation, and the performance of the aircraft. Validation flights are also required when an operator proposes to conduct in-flight or ground maneuvers that require special operational authorizations.
b. Carriage of Revenue Passengers on Validation Flights. Title 14 CFR does not forbid the carriage of revenue passengers on validation flights. The operator may receive FAA authorization to carry revenue passengers during the validation flight when the proposed operation is similar to those in the applicant’s previous experience. However, validation flights do not normally permit the carriage of revenue passengers in the following situations:
• When the operator is seeking initial approval to conduct Class II navigation in any airspace designated as a special area of operation;
• When the operator is seeking approval to conduct Class II navigation by an LRNS or by using a flight navigator not previously approved for that means of navigation;
• When the operator is seeking approval to conduct Class II navigation by means of a long-range navigation procedure not previously approved for that operator; and
• When the operator has not previously operated a specific aircraft type in operations requiring special performance authorization.
c. Special Areas of Operation (SAO). Certain areas of Class II airspace are considered special operating airspace for purposes of validation. These areas include the following:
• Northern Canadian areas of magnetic unreliability;
• NAT/MNPS airspace and Canadian MNPS airspace;
• Central Pacific (CENPAC) composite airspace and Northern Pacific (NOPAC) airspace;
• Arctic Ocean and Antarctic airspace; and
• Politically sensitive areas of operation.
d. Special Navigation Procedures. Validation flights are normally required when an applicant proposes to use navigation procedures not previously demonstrated. These procedures include the following:
• Pilotage, including DR;
• Flight navigator procedures;
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• Celestial navigation;
• Pressure pattern and Bellamy drift DR;
• Free gyro or grid procedures; and
• Any combination of the preceding procedures.
e. Other Situations Requiring Validation Flights. Special operational authorizations and special performance authorizations may also require validation flights. The FAA encourages operators who require additional information on validation flights to contact their local FAA Flight Standards District Office (FSDO).
10-5. INS NAVIGATION—SPECIAL PRACTICES AND PROCEDURES.
a. Preflight. Since INS is a self-contained device and not a position fixing device, it will retain and possibly increment any error induced during alignment throughout the flight unless you remove it through updating procedures. Therefore, during preflight, exercise care to ensure that you insert the accurate present position information into the INS. Although most INSs will automatically detect large errors in present position latitude during alignment, large errors in present position longitude may exist without activating a warning indication. When cross-checking present position coordinates, be alert for the correct hemispheric indicator (that is, N., S., E., W.) as well as the correct numerical values. Since you cannot realign most INSs in-flight, it may require special procedures such as ground realignment to correct a significant error in present position. If the INS in use has the capability of “gang-loading” (simultaneous loading) by use of a remote feature, take care so that you cross-check any data entered by this method separately on each individual INS to detect data insertion errors. Verify the INS software identification and modification status codes to ensure installation of the proper equipment and utilization of the appropriate operating checklist. The operating checklists should include a means of ensuring that the INS is ready to navigate and that the operator activated the navigation mode prior to moving the aircraft. Any movement of the aircraft prior to activating the navigation mode may induce very large errors that only ground realignment can correct.
After placing the system in the navigation mode, check the INS groundspeed when the aircraft is stationary. An erroneous reading of more than a few knots may indicate a faulty or less reliable unit. If this occurs, check the malfunction codes.
b. In-Flight Updating. INS is essentially accurate and reliable, but it is possible to introduce errors in an attempt to improve accuracy by in-flight updating. On the other hand, INS errors generally increase with time and are not self-correcting. If large tracking errors occur, they may significantly degrade aircraft safety and separation criteria. Consider these factors in any decision relative to in-flight updating. As a guide to flightcrews, some operators consider that unless the ground facility provides a precise check and unless the error is fairly significant (for example, more than 6 NM or 2 NM/hour), it is preferable to retain the error rather than update.
10-6. FAA APPROVAL OF GLOBAL POSITIONING SYSTEM (GPS) EQUIPMENT AND OPERATIONS.
a. Portable Units. Handle all portable electronic systems and portable GPS units in accordance with § 91.21. The operator of the aircraft must determine that each portable electronic device they use the aircraft they operate will not cause interference with the navigation and communications systems. Mount yoke mounts usually sold with a portable GPS unit to prevent interference with the operation of the aircraft controls. Install permanent mounts and externally mounted antennas for use with a portable GPS unit in a FAA-approved manner. A critical aspect of any GPS installation is the installation of the antenna. Shadowing by the aircraft structure can adversely affect the operation of the GPS equipment. Electrical noise or static in the vicinity of the antenna can adversely affect the performance of the system. Use portable GPS receivers as a supplemental aid to VFR in conjunction with an approved primary means of navigation.
b. GPS Equipment Classes. GPS equipment is categorized into classes A, B, and C (ref. TSO-C129, TSO-C129A, TSO-C145, and TSO-C146).
(1) Class A. Equipment incorporating both the GPS sensor and navigation capability.
This equipment incorporates receiver autonomous integrity monitoring (RAIM).
• Class A1 equipment includes en route, terminal, and non-precision approach navigation capability.
• Class A2 equipment includes only en route and terminal navigation capability.
(2) Class B. Equipment consisting of a GPS sensor that provides data to an integrated navigation system (i.e., flight management system (FMS), multi-sensor navigation system, etc.).
• Class BI equipment includes RAIM and provides en route, terminal, and non-precision approach capability.
• Class B2 equipment includes RAIM and provides only en route and terminal capability.
• Class B3 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route, terminal, and non-precision approach capability.
• Class B4 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides only en route and terminal capability.
(3) Class C. Equipment consisting of a GPS sensor that provides data to an integrated navigation system (i.e., FMS, multi-sensor navigation system, etc.) that provides enhanced guidance to an AP or flight director (FD) in order to reduce FTE.
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• Class C1 equipment includes RAIM and provides en route, terminal, and non-precision approach capability.
• Class C2 equipment includes RAIM and provides only en route and terminal capability.
• Class C3 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides en route, terminal, and non-precision approach capability.
• Class C4 equipment requires the integrated navigation system to provide a level of GPS integrity equivalent to RAIM and provides only en route and terminal capability.
c. Avionics Installations and Continued Airworthiness. The operator must ensure that they properly install and maintain the equipment. No special maintenance requirements, other than the standard practices currently applicable to navigation or landing systems, are unique to GPS.
d. Certification of GPS Installations and GPS IFR Operations. Provide documentation that validates approval of the installed GPS airborne receiver in accordance with and the current editions of Advisory Circular (AC) 20-130, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, or AC 20-138, Airworthiness Approval of Global Navigation Satellite System (GNSS) Equipment, as appropriate, or other applicable airworthiness criteria established for GPS installations. When it has established that the airborne system receives certification for GPS IFR operations, use the following criteria to determine the operational suitability of airborne systems for GPS IFR use:
FIGURE 10. GPS EQUIPMENT CLASSES TSO-C129
EQUIPMENT CLASS RAIM Integrated Navigation System to Provide RAIM Equivalent.
OCEANIC EN ROUTE
TERMINAL NON-PRECISION
APPROACH
CAPABLE Class A – GPS sensor and navigation capability A1 Yes Yes Yes Yes Yes A2 Yes Yes Yes Yes No Class B – GPS sensor data to an integrated navigation system (i.e., FMS, multi-sensor navigation system, etc.)
B1 Yes Yes Yes Yes Yes B2 Yes Yes Yes Yes No B3 Yes Yes Yes Yes Yes B4 Yes Yes Yes Yes No Class C – GPS sensor data to an integrated navigation system (as in Class B) that provides enhanced guidance to an autopilot (AP) or flight director (FD) to reduce flight technical errors. Limited to part 121 or equivalent criteria.
C1 Yes Yes Yes Yes Yes C2 Yes Yes Yes Yes No C3 Yes Yes Yes Yes Yes C4 Yes Yes Yes Yes No GPS Approval Required For Authorized Use
EQUIPMENT TYPE
INSTALLATION
APPROVAL
REQUIRED
OPERATIONAL
APPROVAL
REQUIRED IFR EN ROUTE IFR
TERMINAL
IFR APPROACH Hand Held X VFR Panel Mount X Par 10-6 Page 129
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X X X X X IFR Oceanic/Remote
X X X X IFR En Route, Terminal, and Approach
X X X X X
e. GPS Equipment Approval and Installation for Class II Navigation and Remote Areas.
• For Class II navigation requiring only the use of a single long-range navigation system (S-LRNS), you may use a GPS IFR installation with a TSO C-129, 129A (or TSO C-145 or TSO C-146, as applicable) authorized navigation system as the only required LRNS.
• For Class II navigation requiring the use of two LRNSs, you may use a single GPS IFR installation with a TSO C-129, 129A (or TSO C-145 or TSO C-146, as applicable) authorized navigation system in conjunction with another approved LRNS, such as an inertial system.
• For Class II navigation requiring the use of two LRNSs, you may use GPS IFR systems for both of the required LRNSs if both GPS units are TSO-C129 or 129A units approved for IFR use and both units also meet the additional requirements specified in FAA Notice 8110.60, GPS as a Primary Means of Navigation for Oceanic/Remote Operations. Specific operational procedures must be accomplished, including performing a fault detection and exclusion (FDE) availability prediction or both GPS units are TSO C-145 or TSO C-146 units approved for IFR use. Accomplish specific operational procedures, including performing a RAIM availability prediction.
f. Aircraft Flight Manual (AFM)/Aircraft Flight Manual Supplement (AFMS) documentation. Aircraft certificated to use GPS as the only LRNSs when two LRNSs are required will have the following statement in the AFM or AFMS: “The ____ GPS equipment as installed has been found to comply with the requirements for GPS primary means of Class II navigation in oceanic and remote airspace, when used in conjunction with the FDE prediction program. This does not constitute operational approval.”
g. FDE Availability Prediction Program. FDE is the capability of GPS to detect a satellite failure that affects navigation and automatically excludes that satellite from the navigation solution. All operators using GPS as the only LRNSs when Class II navigation requires two LRNSs must utilize an FAA-approved FDE prediction program for the installed GPS equipment that is capable of predicting, prior to departure, the maximum outage duration of the loss of fault exclusion, the loss of fault detection, and the loss of navigation function for flight on a specified route. The “specified route of flight” is a series of waypoints to include the route to any required alternates with the time specified by a velocity or series of velocities. Since you may not maintain specific groundspeeds, perform the pre-departure prediction for the range of expected groundspeeds. This FDE prediction program must use the same FDE algorithm (a step-by-step procedure for solving a problem) employed by the installed GPS equipment and you must develop it using an acceptable software development methodology. The FDE prediction program must provide the capability to manually designate satellites that are scheduled to be unavailable in order to perform the prediction accurately. Evaluate the FDE prediction program as part of the navigation system’s installation approval. You can find the requirements for the FDE prediction algorithm in FAA Notice 8110.60, or its successor.
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h. Operational Control Restrictions for Class II Navigation in Oceanic and Remote Areas.
(1) FDE Prediction Program. Prior to departure, the operator must use the FDE prediction program to demonstrate that there are no outages in the capability to navigate the specified route of flight and the FDE prediction program determines whether the GPS constellation is robust enough to provide a navigation solution for the specified route of flight.
Any predicted satellite outages that affect the capability of GPS equipment to provide the navigation function on the specified route of flight requires cancellation, delay, or re-routing of the flight.
(2) Fault Exclusions and Acceptable Durations. Once the navigation function is verified and the equipment can navigate on the specified route of flight, the operator must use the FDE prediction program to demonstrate that the maximum outage of the capability of the equipment to provide fault exclusion for the specified route of flight does not exceed the acceptable duration. Fault exclusion is the ability to exclude a failed satellite from the navigation solution. The acceptable duration is equal to the time it would take to exit the protected airspace, assuming a 35 NM per hour cross-track navigation system error growth rate when starting from the center of the route. For example, a 60 NM lateral separation minimum yields 51 minutes acceptable duration (30 NM divided by 35 NM per hour). If the fault exclusion outage exceeds the acceptable duration, the operator must cancel, delay, or re-route the flight. If the fault exclusion outage exceeds the acceptable duration on the specific route of flight, the operator must cancel, delay, or re-route the flight.
i. En Route Procedures for GPS Class II Navigation in Oceanic and Remote Areas.
(1) Degraded Navigation Capability. If the GPS displays a loss of navigation function alert, the pilot should maintain heading and altitude until they regain GPS navigation. The pilot will report degraded navigation capability to ATC in accordance with § 91.187. Additionally, flightcrew members operating under part 121 will notify the appropriate dispatch or flight following facility of any degraded navigation capability in accordance with the air carrier’s FAA-approved procedures. For at least one hour, the approved long-range GPS units have the ability to automatically provide electronic DR navigation solutions based on last known information. There are strict procedural requirements for dispatch and en route RAIM to ensure satellite coverage along the oceanic routes and that no outages are scheduled to occur during the planned flight. Each operator’s long-range navigation program should require the standardized application of disciplined, systematic cross-checking of navigation information during all phases of flight during Class II navigation.
(2) Satellite Fault Detection Outage. If the GPS displays an indication that a fault detection function outage (e.g., RAIM) is not available, provide navigation integrity by comparing the GPS position with a position computed by extrapolating the last verified position with true airspeed (TAS), heading, and estimated winds. If the positions do not agree to within 10 NM, the pilot should immediately maintain heading and altitude until they regain the exclusion function or navigation integrity and report degraded navigation capability to ATC in accordance with § 91.187.
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