Advisory U.S. Department Circular of Transportation Federal Aviation Administration Subject: CRITERIA FOR APPROVAL OF Date: 3/9/84 AC No: 120-28C CATEGORY III LANDING Initiated by: AFO-210 Change:
WEATHER MINIMA only means, for obtaining approval of Category Illa or Category Illb PURPOSE. This advisory circular (AC) states an acceptable means and not the weather minima and the installation approval of the associated airborne systems.
2. FOCUS. The criteria contained in this AC are applicable to operators using large turbojet aircraft holding Federal Aviation Administration (FAA) operating authority issued under Parts 121, 129, and 135 of the Federal Aviation Regulations (FAR). The FAA approves Category III minima for operators under these parts by amending the applicant's operations specifications.
3. CANCELLATION. AC 120-28B, dated December 1, 1977, is cancelled.
4. RELATED READING MATERIAL. Additional information on Category IIIa/b operations may be found in FAA Order 8400.8, Procedures for the Approval of Facilities for FAR Part 121 and Part 135 Category III Operations, dated September 10, 1980. Copies may be obtained (for a nominal fee) by writing to the:
Federal Aviation Administration Document Inspection Facility Public Inquiry Center, APA-420 800 Independence Avenue, S.W.
Washington, D.C. 20591
5. DEFINITIONS • decision height (DH), or a DH below 100 feet (30 meters), and controlling runway a • Category IIIa. A precision instrument approach and landing with no visual range not less than 700 feet (200 meters).
b. Category IIIb. A precision instrument approach and landing with no DH, or with a DH below 50 feet (15 meters), and controlling runway visual range less than 700 feet (200 meters), but not less than 150 feet (50 meters).
c. Category IIIc. A precision instrument approach and landing with no DH and no runway visual range limitation.
d. Decision Height (DH). A specified height at which a missed approach must be initiated if the required visual reference to continue the approach to land has not been established.
AC 120-28C 3/9/84
e. Alert Height (AH). A height defined for operational use by pilots (100 feet or less above the highest elevation in the touchdown zone), above which a Category III approach would be discontinued and a missed approach initiated if a failure occurred in one of the required redundant operational systems in the airplane or in the relevant ground equipment. Below this height, the approach, flare, touchdown, and, if applicable, rollout may be safely accomplished following any failure in the airplane or associated Category III systems not shown to be extremely improbable. This height is based on characteristics of an aircraft and its particular fail-operational airborne Category III system.
f. Fail-Operational Category III System. An airborne system which provides redundant operational capability down to touchdown and, if applicable, through rollout. Fail-operational capability may be provided by automatic systems, manually flown systems, or a combination of both. The redundant operational systems must have no common failure modes, and need not be the same. If one of the required Category III systems fails below the AH, the flare, touchdown, and rollout, if applicable, can be accomplished using the remaining operational system or systems. In manually flown systems, the remaining operational system or systems must be available to either pilot without pilot action.
g. Automatic Fail-Operational Category III System. A fail-operational system which provides redundant operational capability using automatic systems. If one of the automatic systems fails below the AH, the flare, touchdown, and rollout, if applicable, can be accomplished using the remaining automatic system(s).
h. Fail-Passive Automatic Flight Control System. An automatic flight control system which, upon occurrence of any single failure, should not:
(1) Cause significant displacement of the aircraft from its approach path or altitude loss below the nominal glidepath.
(2) Upon system disconnection, involve any out-of-trim condition not easily controlled by the pilot.
(3) Cause any action of the flight control system that is not readily apparent to the pilot, either by control movement or advisory display.
i. Approved Simulator. For the purposes of this AC, approved simulators are those simulators approved by the principal operations inspector for the specific Category III maneuvers required in paragraph 10.
j. Rollout Control System. A system which provides either automatic control or instrument guidance for manual control of lateral steering for rollout until manual control of the aircraft by visual reference is assured.
k. Proof of Concept Testing. "Proof of concept testing" is defined as a generic demonstration in a full operational environment of facilities, weather, crew complement, aircraft systems, environmental systems, and any other relevant parameters necessary to show concept validity in terms of performance, system reliability, repeatability, and typical pilot response to failures as well as to demonstrate that an equivalent level of safety is provided. "Proof of concept" may be established by a combination of analysis, simulation and/or flight demonstrations in an operational environment. In certain cases, operational 2 Par 5
"proof of concept" may not be necessary if the validity of the concept was demonstrated during the type certification approval of the Category III airborne systems and the Director of Flight Operations determines, on a case-by-case basis, that "proof of concept" has been established.
DISCUSSION. To be acceptable for Category III operations, the automatic landing systems should meet the criteria in AC 20-57A, Automatic Landing Systems (ALS), and Appendix 1 of this AC; the rollout control system, if required, should meet the criteria in Appendix 2 or Appendix 3 of this AC, as appropriate.
systems should also enable Category III operations in accordance with the operational concepts discussed in this AC. The following criteria are issued to identify the airport and ground facilities, airborne systems, training requirements, and maintenance standards which, if met, will provide a basis for approval of Category III landing minima. The first principal change included in this revision permits certain aircraft with a fail-operational automatic landing system and a rollout control system to operate to Category IIIb weather minima on certain instrument landing system (ILS) facilities which previously were limited to use for Category IIIa approaches in the United States. The second change clarifies the systems' requirements and visual references necessary for various Category III operations. The effect of the changes will be to provide suitable credit for modern flight control and other aircraft systems and permit additional Category III approaches at U.S. and international facilities where such approaches may be safely conducted.
7. OPERATIONAL CONCEPTS. The weather conditions encountered in Category III operations range from an area where visual references are adequate for manual rollout in Category Illa, to an area where visual references are inadequate even for taxi operations in Category IIIc. To maintain a high level of safety during approach and landing operations in very low visibilities, the airborne system and ground support system requirements established for Category III operations should be compatible with the limited visual references that are available.
The primary mode of Category III operations is automatic-to-touchdown using automatic landing systems which do not require pilot intervention. However, pilot intervention should be anticipated in the unlikely event that the pilot detects or strongly suspects inadequate aircraft performance as well as when he determines that an automatic touchdown cannot be safely accomplished within the touchdown zone.
To be approved for Category III operations, the airplane and its associated systems should be shown to provide sufficient information to the flightcrew to permit the safe completion of the approach, touchdown, and rollout or the safe completion of a go-around from any altitude to touchdown, following any failure conditions not shown to be extremely improbable. Additionally, the design of the cockpit instrumentation, system comparators, and warning systems should be adequate in combination to assure that the pilot can verify that the aircraft will safely touchdown within the touchdown zone and safely rollout if the controlling runway visual range (RVR) is reported at or above minima.
Although the primary mode is automatic-to-touchdown, these operational concepts do not preclude the use of systems to conduct Category III operations with the pilot-in-the-active-control-loop if "proof of concept testing" demonstrates that these systems provide an equivalent level of safety.
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AC 120-28C 3/9/84
a. Safety of Go-Around From Any Point in the Approach. An aircraft approved for Category III operations should be capable of safely executing a go-around from any point in an approach prior to touchdown with the aircraft in a normal configuration. This is appropriate to provide for go-arounds due to air traffic control (ATC) contingencies, rejected landings, loss of visual reference, or missed approaches due to other reasons. The evaluation of this capability is based on normal Category III operations at the lowest controlling RVR authorized and should account for factors related to geometric limitations during the transition to go-around, the limited visual cues that are available, autopilot mode switching, and other pertinent factors. For aircraft in which a go-around from a very low altitude may result in an inadvertent touchdown, the safety of such a procedure should be established considering relevant factors such as operation of autospoilers, automatic braking systems, autopilot mode switching, autothrottles, and other pertinent systems associated with a low altitude go-around.
If the occurrence of any failure condition in the airplane or its associated systems, including critical engine failure, could preclude the flightcrew from executing a safe go-around from low altitude, Category III operations may be conducted with these airplanes only if the total airborne system has the capability to permit an approach, touchdown, and rollout to be safely continued and completed following any failure conditions not shown to be extremely improbable. Additionally, in the event of such a failure after passing 100 feet above ground level (AGL), the cockpit cues or indications should not cause the flightcrew to attempt a go-around.
If an automatic go-around capability is provided, it should be demonstrated that a go-around can be safely initiated and completed from any altitude to touchdown.
If the automatic go-around mode can be engaged at or after touchdown, it should be shown to be nonhazardous. The ability to initiate an automatic go-around at or after touchdown is not required.
Information should be provided to the crew regarding appropriate procedures for go-around and expected altitude loss during a properly executed automatic or manual go-around. Expected height loss should be provided to the crew as a function of go-around initiation altitude for the region below 100 feet AGL. In the event that an aircraft has been demonstrated to be capable of Category III operations with an engine inoperative, height loss information should also be provided for the engine-out case.
b. Fail-Passive Category III Operations. Fail-passive Category III operations are conducted with a 50-foot DH and are limited to Category IIIa.
Since a fail-passive Category III system does not necessarily provide sufficient redundancy to successfully continue the approach and landing to touchdown following any failure in the flight control system not shown to be extremely improbable, a DH of 50 feet is specified. A DH is established to ensure that, prior to passing 50 feet, the pilot determines that adequate visual reference is available to verify that the aircraft is in a position which will permit a successful landing in the touchdown zone. If this visual reference is not established prior to passing DH, a go-around will be executed. A missed approach will also be initiated if, after passing DH, visual cues are lost or a reduction in visual cues occurs which prevent the pilot from continuing to verify that the 4 Par 7
AC 120-28C 3/9/84 aircraft is in a position which will permit a successful landing in the touchdown zone. In the event of a failure of the system at any point in the approach to touchdown, a missed approach will normally be required.
If the need to initiate a go-around below 100 feet AGL due to airplane failure conditions has been shown to be improbable, a fail-passive automatic landing system may be used for Category Illa if the system is shown to provide the capability to safely touchdown in the touchdown zone or to safely complete a go-around from any altitude to touchdown following any failure conditions not shown to be extremely improbable.
Due to considerations of approach geometry related to factors such as "wheel to glide slope antenna height," "wheel to pilots eye height," and cockpit visibility, authorization for fail-passive Category IIla operations may not be appropriate for all sizes or types of aircraft. Applicability of Category III to such fail-passive systems is limited to those aircraft for which the concept can be shown to apply by "proof of concept testing."
Typical arrangements which could be used to meet the requirements for operating to a 50-foot Category IIIa DH include the following:
(1) A single, monitored fail-passive flight control system with automatic landing.
(2) A fail-operational automatic landing system which has reverted to fail-passive due to the occurrence of a failure during flight, or has been dispatched in a fail-passive configuration.
(3) A monitored fail-passive head up display (HUD) or head down display (HDD) designed for a pilot-in-the-active-control-loop flight guidance system with instrument displays suitable for monitoring, by the pilot-not-flying, of the overall performance of the Category III system and the performance of the pilot flying.
operations are conducted with fail-operational flight control systems for use to Fail-Operational Category III Operations. Fail-operational Category I11 touchdown in Category IIIa, and through rollout to safe taxi speeds in the lower limits of Category IIIb. The required redundancy may be provided by multiple automatic landing and rollout systems, by an approved manual backup capability to the primary automatic system, or by multiple advanced/sophisticated pilot-in-the-active-control-loop systems. If credit is taken for manual capability, it should be suitable for landing to touchdown by reference to instruments alone for Category Illa or for landing and rollout by reference to instruments alone for Category IIIb.
The reliability and performance of the required redundant operational systems should be such that continued safe operation to landing in Category Illa or landing and rollout in Category IIIb can be achieved following any failure conditions, not shown to be extremely improbable, which could occur below 100 feet AGL.
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AC 120-28C 3/9/84 An AH should be specified in all fail-operational Category III operations and operations with fail-operational Category III systems are normally conducted in accordance with the AH concept. This is consistent with the system design philosophy which requires the airborne system to be capable of successfully completing a touchdown and, if applicable, a rollout following a failure which occurs after passing 100 feet AGL. As specified in Appendix 1, it must be shown that an unsafe landing is extremely improbable based on various exposure times which are established for different types of operations. These exposure times are based on the time necessary to complete various phases of the approach, landing, and rollout beginning from a point at least 100 feet AGL.
In the event that an aircraft design provides for inhibiting certain noncritical warning system functions after passing this point, such inhibiting features should not occur at height above 500 feet AGL. Conversely, even though certain alerts or warnings are inhibited, such a feature does not preclude an aircraft operator from setting an AH at a value lower than the height at which they are inhibited because touchdown would occur within the prescribed touchdown area even though a noncritical system failure occurs below this height and the warning is inhibited.
If a DH is used by an airline for fail-operational Category III, it should be compatible with the flight control and display systems installed in the airplane and with the AH to be used operationally. A DH limitation is only applied to fail-operational systems in special cases: where a unique design feature in the airborne system or ground support system requires a DH limitation, or where a foreign country requires the use of a DH to conduct operations in that particular country. Additionally, an airline may apply a DH limitation to fail-operational systems even though the use of a DH is not specifically required by these special cases.
The following are typical arrangements by which the requirement for failoperational systems may be met:
(1) Two or more monitored autopilots or integrated autopilot/flight director systems each with dual channels making up an automatic, fail-operational system designed so that at least one system remains operative after a failure.
(2) Three autopilots or integrated autopilot/flight director systems designed so that at least two remain operative after a failure to permit comparison and provide necessary hardover protection.
(3) A monitored fail-passive automatic flight control system with automatic landing capability to touchdown and rollout, if applicable, plus an independent and adequately failure-protected flight guidance system with dual displays.
(4) If "proof of concept" has been acceptably demonstrated for manually flown systems, two or more independent and adequately failure-protected pilot-in-the-active-control-loop flight guidance systems with independent displays may be used.
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For the flight guidance systems described in subparagraphs c(3) and c(4), the displays should include flare or flare and rollout commands, as applicable, displayed to each pilot. The raw data and flight guidance command displays, HDD or HUD, must provide sufficient guidance so that a pilot of average skill can demonstrate a touchdown dispersion which meets the criteria of AC 20-57A and, if applicable, the rollout control system criteria of Appendix 2 or Appendix 3 of this AC, as applicable. This demonstration is required over any portion of the approach and landing for which manual control or manual takeover is considered a part of the Category III system.
Category III Operations Conducted with an Alert Height. The AH is specified by an operator of an aircraft and approved by the FAA. This height must be compatible with aircraft system configuration, training, ground facilities, and other factors pertinent to the air carrier's operation. Although AH will be less than or equal to 100 feet AGL, it should generally be set at 100 feet AGL. By setting the AH at 100 feet AGL the aircraft may continue, in the event that a failure occurs in an element of the Category III system prior to beginning the final approach segment, to Category I or Category II minima as appropriate to the weather conditions and the equipment which remains operational on the aircraft.
This is desirable to permit and encourage the use of Category III approaches and procedures by allowing continuation of an approach to Category I or Category II minima, as appropriate, without the need to reinitiate an approach.
Additionally, for those aircraft equipped with Category Ill systems which have the capability to continue Category IIla operations in the fail-passive configuration following a failure which precludes a fail-operational approach and landing, the approach may be continued, to the 50-foot DH, using the operative fail-passive system if the controlling RVR is reported at or above Category Illa minima and the landing may be completed if the necessary visual references are established prior to passing the DH.
e. Category IIIa Operational Concepts. Category IIIa operations can be conducted with either fail-operational or fail-passive automatic landing systems with minima no lower than 700 RVR (200 meters). If the system's reliability is such that the need for a go-around below 100 feet AGL due to airplane failure conditions is shown to be improbable, Category Illa operations may be conducted with systems which permit either the safe completion of the landing or the safe completion of the go-around following any failure condition not shown to be extremely improbable.
As discussed in paragraph 7b, fail-passive Category IIIa operations are conducted The DH is established to ensure that, prior to passing 50 feet, the pilot determines that adequate visual reference is available to verify that the aircraft is in a position which will permit a successful landing in the For Category IIIa fail-operational approach and landing (as discussed in paragraph 7c) without a rollout control system, visual reference with the touchdown zone is required and should be verified prior to the minimum height specified by the operator for that particular aircraft type. These visual cues combined with controlling transmissometer RVR reports of visibility at or above minima are necessary to verify that the initial landing rollout can be accomplished visually.
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Lacking visual reference prior to the specified minimum height or in the event of receiving a report of controlling RVR below minima prior to this height, a go-around should be accomplished.
For Category IIla fail-operational approach and landing (as discussed in paragraph 7c) with a rollout control system, the availability of visual reference is not a specific requirement for continuation of an approach to touchdown. The design of the cockpit instrumentation, system comparators, and warning systems should be adequate in combination to assure that the pilot can verify that the aircraft will safely touchdown within the touchdown zone and safely rollout if the controlling RVR is reported at or above approved minima.
f. Category IIIb Operational Concepts. Category IIIb operations are conducted with fail-operational landing systems which include a rollout control system for lateral steering control for rollout until manual control of the aircraft by visual reference is assured. These operations are conducted with systems which, after passing 100 feet AGL, permit the safe completion of the approach, touchdown, and rollout following any failure conditions not shown to be extremely improbable.
The rollout control system should meet the criteria in Appendix 2 or Appendix 3, as appropriate.
the cockpit instrumentation, system comparators, and warning systems should be with operat on in don of 1 apper vitol recheme the design of adequate in combination to assure that the pilot can verify that the aircraft will safely touchdown within the touchdown zone and safely rollout if the controlling To be approved for Category IIlb operations with fail-passive rollout control systems, it should be demonstrated under the most critical conditions expected in service that the airplane and its associated systems provide sufficient capability for the pilot to control the airplane so as to remain on the runway and stop within the runway length available following any airplane failure conditions not shown to be extremely improbable.
To be approved for Category IIlb operations with fail-operational rollout control systems, aircraft system failures not shown to be extremely improbable (after touchdown and until the point where the pilot's ability to manually control the aircraft by visual reference is assured) should not preclude the ability of the rollout control system to control the airplane so as to remain on the runway or present cues or indications to the pilot that would cause him/her to attempt a manual rollout using visual references. These capabilities should be demonstrated under the most critical condition expected in service.
Category IIIb operations may be conducted to minima as low as 300 RVR (100 meters) with fail-operational Category IIIb landing systems which incorporate a rollout control system which meets the criteria of Appendix 2.
Category IIIb operations may be conducted to minima as low as 150 RVR (50 meters) with fail-operational Category IIIb landing systems which incorporate a rollout control system which meets the criteria of Appendix 3.
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If "proof of concept" has been acceptably demonstrated, Category IIIb operations may be conducted to minima as low as 600 RVR (175 meters) with fail-operational Category IIIb landing systems which incorporate rollout control systems deemed to be "non-hazardous" which comply with the tracking performance requirements of Appendix 2 or Appendix 3.
Runway Field Length Requirements. As in other operations, the runway field length requirements for Category III operations are based on the provisions of Section 121.195(b) of the FAR. If an automatic braking system is used and the 3 any which tre cler the not dry, the reguled frost wongth on this data.
However, to ensure that a high level of safety is maintained if other deceleration means are used, the runway available for landing in Category III conditions should be the distance obtained by multiplying the required field length specified in Section 121.195(b) by the following factors:
(1) Category IIIa. The factor to be applied to determine the required field length is 1.15.
(2) Category IIIb.
(i) Minima: 600 RVR (175 meters). The factor to be applied to determine the required field length is 1.15.
(ii) Minima: 300 RVR (100 meters) • (A) For grooved or PFC runways reported clear and dry as well and not dry, the factor to be applied to determine the required field length is 1.3. However, this factor may be reduced to 1.15 if antiskid and reverse thrust systems are both installed and these systems are fully operational.
(B) Operations are not appropriate on ungrooved/non-porous friction coarse runways.
(iii) Minima: 150 RVR (50 meters).
(A) For grooved or PFC runways reported clear and dry as well as clear but not dry, the factor to be applied to determine the required field length is 1.3. Factors as low as 1.15 may be authorized in the future if operational experience indicates that the runway surface treatments (i.e., grooving, PFC) and runway maintenance practices (i.e., friction measurement and cleaning) are compatible with these lower factors. To use factors as low as 1.15, antiskid and reverse thrust systems should be installed and should be fully operational.
(B) Operations are not appropriate on ungrooved/non-porous friction coarse runways.
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(C) A procedural means is not appropriate to meet the provisions for deceleration in paragraph 9c.
8. AIRPORTS AND GROUND FACILITIES.
a. U.S. Airports.
(1) An applicant may be authorized to use minima as low as 700 RVR (200 meters) for Category IIIa or 300 RVR (100 meters) for Category IIIb at designated airports which meet the criteria described in subparagraph a(2).
Category IIIb minima as low as 150 RVR (50 meters) may be authorized in the future if operational experience indicates that the airborne and ground support equipment are compatible with the lower minima. Due to limitations of transmissometers and lighting systems, however, the interim limits for U.S. Category IIIb operations are 600 RVR (175 meters) on U.S. facilities until suitable facility upgrading is completed. Additionally, unless the runways are grooved or have PFC surfaces,, Category III operations are limited to minima no lower than 600 RVR (175 meters).
(2) The ground-based system will have failure-survival capabilities such that total loss of localizer and/or glidepath guidance when the airplane is below 100 feet AGL will be extremely improbable. However, transient loss of guidance which occurs during the detection of a ground system failure and reversion to the backup transmitter is probable. Therefore, the airborne equipment should be able to accommodate these transient conditions. Precautions will be taken to control traffic in critical areas over and on the airport to avoid ILS overflight and reflection interference. The basic ground facility requirements are as follows:
(1) For Category IIIa minima - ILS systems of U.S. Type II or Type III (or foreign equivalent). However, for Category Illa operations, aircraft which have not been shown to have satisfactory autoland performance using U.S. Type Il facilities will be restricted for Category Illa to runways having U.S. Type III facilities.
(11) For Category IIIb minima - U.S. Type II, Type III, or foreign equivalent facilities may be used to 600 RVR (175 meters). However, until suitable facility upgrading is completed, only U.S. Type III or equivalent foreign facilities may be used for operations below 600 RVR (175 meters).
(iii) An approach light system which meets U.S. requirements for an ALSF-I or ALSF-II configuration or International Civil Aviation Organization (ICAO) equivalent in foreign countries. However, Category III approaches and landings may be continued if sequence flashers are inoperative.
(iv) Standard touchdown zone lights in accordance with AC 150/5340-4C, Installation Details for Runway Centerline and Touchdown Zone Lighting Systems, or ICAO equivalent in foreign countries.
(v) Standard centerline lights as specified in AC 150/5340-4C, or ICAO equivalent in foreign countries.
(vi) Precision instrument runway marking in accordance with AC 150/5340-1E, Marking of Paved Areas on Airports, or ICAO equivalent in foreign countries.
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(vii) For Category IIIa, 3 RVR transmissometers are required, unless it can be shown that 2 RVR transmissometers can meet the operational needs for a particular runway. For Category IIIb, 3 transmissometers are required and they should read in 100-foot (25 meter) increments or less for landing minima below 600 RVR (175 meters) .
(viii) Arrangements to permit immediate voice communications to the pilot for sudden RVR changes are required, but automatic transmission of RVR data to the pilot is not required.
Obstacle clearance and ILS critical area protection requirements for precision approaches will be provided in accordance with TERPS Chapter 9, and Order 7110.65C, Air Traffic Control, paragraph 974. This includes use of appropriate signs, markings, stop bars, lights, or other means to provide protection from inadvertent intrusion of aircraft or ground vehicles on runways, taxiways, or obstacle-free areas and to provide protection of ILS signals in reduced visibility conditions.
(x) An established system and/or procedure acceptable to FAA which provides for positive control over aircraft and vehicles on the airport to assure that the active runway is clear and that obstacle free zones and ILS critical areas are protected as necessary for low visibility operations.
Prior to approval of Category III minima for a particular aircraft type on any facility not formerly approved for Category III use for that type of aircraft, acceptable autoland, or autoland and rollout performance if applicable, should be verified. This verification may be made by airline and/or FAA observation of automatic landings during line operations or training flights in weather conditions at or above Category II minima to determine adequacy of the facility for that type aircraft. In certain special cases, as designated by the FAA, where U.S. Type II facilities are used at locations where the characteristics of the prethreshold terrain may induce abnormal performance in certain automatic flight control systems, additional analysis or flight demonstrations in line service may be required for each aircraft type prior to approval of Category III
b. Foreign Airports. An applicant having U.S. Category III approval may be authorized to use Category III minima at foreign airports on the FAA-approved list. Airports are approved and listed when the following conditions are met:
(1) The airport is approved for Category III operations by the appropriate foreign airport authority.
(2) The visual aids are equivalent to those used for U.S. Category III approaches.
(3) Electronic ground aids are at least equivalent to those designated for U.S. Category III approaches.
(4) The FAA office having responsibility for the area in which the foreign facility is located has reviewed and verified the conditions in subparagraphs b(1), b(2), and b(3).
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The major factors to be considered when approving such airports will be the equivalence with U.S. standards of the approach light systems, high intensity runway lights, in-runway lights, quality and integrity of the electronic approach and landing guidance systems, runway marking, procedures for reporting runway the systems at foreign airports may not be exactly in accordance with U.S. standards, it is important that any foreign facilities used for Category III provide the necessary information or functions consistent with the intent of the U.S. standards. Carriers desiring Category III approvals at foreign airports or runways not on the FAA-approved list should submit such requests through their FAA principal operations inspector to the Air Transportation Division, AFO-200, FAA Headquarters, Washington, D.C.
9. AIRBORNE SYSTEMS.
a. Equipment for Category Illa. The following equipment, in addition to the instrument and radio equipment required by the FAR, is the minimum airborne equipment considered necessary:
(1) Two ILS localizer and glide-slope receivers which meet the performance requirements outlined in Appendix 1, paragraphs 7a and 7b.
(2) Two approved radio (radar) altimeter systems which meet the performance requirements outlined in Appendix 1, paragraph 7e.
(3) Redundant flight control systems which meet the requirements of Appendix 1, paragraph 7c.
(4) Missed approach guidance appropriate for Category III operations as follows:
Attitude gyro (or equivalent) indicators with calibrated pitch attitude markings or preestablished computed pitch command display, or (i1) Approved flightpath angle display.
NOTE: An automatic go-around system may be used with either of the above.
(5) Autothrottle control system which meets the requirements of Appendix 1 for operations approved without a DH. For operations with a 50-foot DH, autothrottles are required unless it has been demonstrated by "proof of concept testing" that operations can be safely conducted without their use.
Performance requirements are listed in Appendix 1 if an autothrottle system is required.
(6) Failure detection and warning capability as described in Appendix 1, paragraphs 7c and 7g.
b. Equipment for Category IIIb. Additional equipment, over and above that specified in paragraphs 7c and 9a, is required for Category Illb operations.
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