AC 20-191 such, the applicant must d emonstrate that the takeoff guidance system accounts for any differences, if any, between the runway centerline and the reference lateral path. The applicant should demonstrate c ompliance by flight test, or by a combination of flight test and simulation. Flight testing must cover those factors affecting the behavior of the aircraft (e.g., wind conditions, ILS characteristics, weight, center of gravity).
3.2.3.6.4 The applicant should demonstrate that when the airplane is displaced from the runway centerline at any point during the takeoff or rejected takeoff, including engine failure cases, the takeoff guidance system will allow the “ pilot flying” (PF) to control the airplane smoothly back to the intended path in a controlled and predictable manner. Minor overshoot or oscillations around the centerline are permissible when not leading to unacceptable flight crew workload.
3.2.3.6.5 The applicant should use the perfor mance envelope and conditions in Figure 3-1 for evaluating the takeoff guidance system.
• Takeoff with all engines operating,
• Engine failure at or slightly after V1- continued takeoff*,
• Engine failure just prior to V1- rejected takeoff *; and
• Engine failure at a speed prior to VMCG – rejected takeoff (VFAILURE< VMCG)*.
*Wind and runway conditions consistent with basic aircraft takeoff performance demonstrations.
3-3
AC 20-191 Figure 3-1. Performance Envelope for Evaluating Takeoff System Command Guidance V1 is takeoff decision speed VFAILURE – speed at which failure occurs VMCG is Ground Minimum Control Speed VLOF is Liftoff Speed Note 1: When showing compliance, the pilot may adjust the lateral flight path after liftoff to account for wind and drift effects.
Note 2: The 14m lateral region addresses tracking on the runway surface.
Note 3: The FAA expects the pilot to position the aircraft on the runway centerline.
Once on the runway, the takeoff guidance system should provide an indication to confirm proper operation.
Note 4: The lateral tracking criteria is referenced to the lateral offset of the aircraft’s centerline between the main landing gear (or aircraft center of gravity).
3.2.3.6.6 The system should have no characteristic making it difficult for a pilot to transition to a safe climb flight path, consistent 3-4
AC 20-191 with obstacle clearance for obj ects near the runway .
3.2.3.6.7 When demonstrating compliance, the applicant can take into consideration testing techniques such as normal pilot technique for responding to engine failure, application of rudder, maintaining safe bank angles, rotating to suitable pitch attitudes, and compensating for crosswind, as necessary .
3.2.3.6.8 When the rejected takeoff is the result of an engine failure , the actual performance should reflect the effects of a short-term increase in lateral deviation and then converge toward the centerline during the deceleration to a full stop.
3.2.3.6.9 During takeoff, the system must annunciate guidance signal loss to the flight crew.
3.2.3.6.10 The applicant should demonstrate t he vertical axis guidance of the takeoff system during normal operation provides an appropriate pitch attitude and climb speed when considering the following factors.
• A normal rate of rotation to the commanded pitch attitude, at VR-10 knots for all engines operating and VR-5 knots for an engine-out condition, does not result in a tail-strike.
• Acquire a pitch attitude resulting in the capture and tracking of the All-Engine Takeoff Climb Speed, V2 + X, where X is the All-Engine Speed Additive from the AFM (normally 10 knots or higher).
3.2.3.6.11 For engine-out operations, the applicant should demonstrate the takeoff guidance system provides commands to acquire a pitch attitude result ing in the capture and tracking of the following reference airspeeds.
• V2, for engine failure at or below V2. (The aircraft should attain this speed after liftoff.)
• Airspeed at engine failure, for failures between V2 and V2 + X.
• V2 + X, for failures at or above V2 + X. Alternatively, the applicant may use the airspeed at engine failure provided the system can achieve the minimum takeoff climb gradient at that speed.
3.2.3.6.12 The applicant should demonstrate t he workload associated with the use of the takeoff system compl ies with the Handling Quality Rating System (HQRS) criteria in AC 25-7, Flight Test Guide for Certification of Transport Category Airplanes, 3-5
AC 20-191 as amended, or equivalent cr iteria for the type of aircraft. The takeoff guidance system should provide required tracking performance with “ satisfactory” workload and pilot compensation, under foreseeable normal conditions. The takeoff guidance system may provide reduced (i.e., HQRS Rating Adequate) path tracking performance (e.g., up to 14m lateral deviation on the ground, ref . Figure 3-1) with adequate workload (i.e., heightened pilot effort and attention) during takeoffs with engine failures.
3.2.4 Integrity.
The applicant must demonstrate the takeoff guidance system provides command information as lateral guidance, which will enable maintaining the aircraft on the runway during the takeoff roll through acceleration to liftoff or, during a deceleration to a stop during a rejected takeoff.
3.2.4.1 The applicant must evaluate the design of the onboard components of the low-visibility system, separately and in relation to other systems, pursuant to 14 CFR Parts 23, 25, 27, and 29; and sections 23.2500, 23.2510, 23.2605,
25.1309, 27.1309, and 29.1309, respectively, as applicable. The following criteria is provided for the application of§ 25.1309 to the takeoff guidance system:
3.2.4.1.1 The takeoff guidance system design should not possess characteristics, in normal operation or when failed, that would degrade takeoff safety or lead to a hazardous condition .
3.2.4.1.2 The probability of the takeoff guidance system generating misleading information that could lead to an unsafe condition must be improbable when the flight crew is alerted to the condition by suitable fault annunciation or by information from other independent sources available within the pilot's primary field of view. For airworthiness, the applicant must demonstrate the effectiveness of the fault annunciation or information from other independent sources . Any single failure of the aircraft that could impact the takeoff path (e.g., engine failure, single electrical generator or bus failure, single Inertial Reference Unit (IRU) failure) must not cause loss of guidance information or give incorrect guidance information .
3.2.4.1.3 The probability of the takeoff guidance system generating misleading information that woul d be unsafe to follow, must be extremely improbable , if:
• No means are available for the takeoff system to detect and annunciate the failure, and
• No information is provided to the pilot to immediately 3-6
AC 20-191 detect the malfunction and take corrective action.
3.2.4.1.4 I LS. The applicant must establish the aircraft system response to loss of ILS localizer transmitter. The applicant must also establish the aircraft system response during a switchover from an active localizer or to an optional backup transmitter.
3.2.4.1.5 GLS. The applicant must establish the aircraft system response to loss of GLS guidance signals .
3.2.4.2 In the event of a probable failure (e.g., engine failure, electrical source failure), if the pilot follows the takeoff display and disregards external visual references, if applicable, the aircraft performance must meet the criteria illustrated in Figure 3-1.
In showing system compliance, the applicant may not factor the proportion of takeoffs made in low visibility into the probabilities of performance or failure effects.
3.2.5 Information, Annunciation, and Alerting.
This section identifies information, annunciations, and alerting criteria for the takeoff guidance system. The design of the controls, indicators, and alerts must minimize crew errors that could cause a hazard. The takeoff guidance system must present the mode and system malfunction indications in a manner compatible with the procedures and assigned tasks of the flight crew. The takeoff guidance system must group the indications in a logical and consistent manner and ensure they are visible under all expected normal lighting conditions.
3.2.5.1 Compliance.The design of the Information, Annunciation, and Alerting HUD must comply with 14 CFR §§ 23.2605, 25.1322, 27.1322, or 29.1322 as applicable. Reference AC 23.1311-1, AC 25.1322-1, AC 27-1, or AC 29- 2 for additional guidance.
3.2.5.2 Annunciation.The applicant must demonstrate prior to initiating takeoff and during takeoff, the takeoff guidance system provides positive indications of the following information to the flight crew:
• System status,
• Modes of engagement and operation, and
• Guidance source.
If pitch or speed or both guidance is also provided, the takeoff guidance system must detect and promptly announce to the pilot failures that would result in rotation at an unsafe speed, or an unsafe pitch rate or pitch angle.
3.2.5.3 Alerting.
The takeoff guidance system must alert the flight crew whenever a failure or 3-7
AC 20-191 condition prevents it f rom meeting the performance specified in sections
3.2.3 and 3.2.4. The removal of guidance alone is not adequate annunciation. Alerts must be timely, unambiguous, readily evident to each flight crew member, and compatible with the alerting philosophy of the airplane. Annunciations must be located to ensure rapid recognition and must not distract the pilot making the takeoff or significantly degrade the forward view.
3.2.5.3.1 Annunciations.During takeoff, whenever the takeoff guidance system does not provide valid guidance appropriate for the takeoff operation, it must clearly annunciate the failure to the flight crew, and the invalid guidance must be removed. The location of the annunciation must be positioned to ensure rapid recognition without distracting the pilot or significantly degrading the forward view.
3.2.5.3.2 Warnings.The takeoff guidance system must provide warnings for conditions requiring immediate pilot awareness and action
(e.g., failure of the guidance system).
3.2.5.3.3 Cautions.The takeoff guidance system must provide cautions for conditions requiring immediate pilot awareness and possible subsequent pilot action. These alerts need not generate a Master Caution light that would be contrary to the takeoff alert inhibit philosophy. Caution annunciations should not cause flight crew distraction during takeoff roll.
3.2.5.3.4 Advisories.The takeoff guidance system must provide advisories for conditions requiring pilot awareness in a timely manner. It should not generate advisories after takeoff commences.
3.2.5.3.5 System Status.
The takeoff guidance system should provide a system status
(e.g., status of built-in test equipment (BITE)/self-test).
3.2.6 Availability.
The probability of loss of takeoff guidance system should be remote.
3.3 Airborne Systems for Takeoff.
This section covers the criteria for a HUD that is integrated with ILS localizer or GBAS signals. In all cases, this AC assumes the sensors used for approach and landing will guide the aircraft during takeoff.
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AC 20-191
3.3.1 HUD for Ta keoff Guidance.
The following criteria apply if an applicant employs a HUD to provide takeoff guidance:
3.3.1.1 The workload associated with use of the HUD must comply with 14 CFR §§
23.2610, 25.1523, 27.1523, or 29.1523 as applicable. Reference AC 23.1523 and AC 23.1311-1; AC 25.1523-1 and AC 25-11, AC 27-1; or AC 29-2 as applicable for additional guidance.
3.3.1.2 The HUD installation and display presentation must meet 14 CFR §§
23.2600(a), 25.773, 27.773, or 29.773 as applicable. Reference AC 23.1311- 1; or AC 25.773 and AC 25-11, appendix F; or AC 27-1; or AC 29-2 for additional guidance.
3.3.1.3 For the entire takeoff path and for all normal and non-normal conditions, except loss of the HUD itself, the HUD takeoff system must provide acceptable guidance and flight information to enable the PF to complete the takeoff or abort the takeoff. HUD takeoff system use should not require excessive workload, exceptional skill, or excessive reference to other cockpit displays.
3.3.2 GBAS.
An applicant may use the guidance in this chapter to obtain airworthiness approval of a GBAS receiver for low visibility takeoff guidance. In addition, the applicant must evaluate the effect of loss and signal reacquisition during takeoffs .
3.4 Takeoff Guidance Evaluation.
An applicant should submit performance data for components used for takeoff guidance.
3.4.1 Certification Plan .
The applicant should provide a certification plan that includes a description of the aircraft systems, the certification basis, the certification methods, and compliance documentation. The certification plan should describe how any non-aircraft elements relate to the operation of aircraft systems from a performance, integrity, and availability perspective.
3.4.1.1 For ILS-based system elements, the applicant can predicate satisfaction of these performance provisions upon compliance with the ICAO Standards and Recommended Practices (SARPs), equivalent State standard, or by reference to an acceptable standard for performance of any navigation service.
3.4.1.2 For a Global Navigation Satellite System (GNSS) based system such as GBAS, the applicant can predicate satisfaction of these performance 3-9
AC 20-191 provisions upon compliance with either the ICAO SARPs, or equivalent State s tandards. The applicant should address any gaps or shortfalls in performance and how they relate to the aircraft system certification plan.
3.4.1.3 The certification plan should describe any new or novel system concepts or operational philosophy as applicable. The FAA will determine the need for additional criteria and provisions beyond this AC.
3.4.2 Performance Evaluation.
For new systems and any significant changes to an existing system, the applicant should demonstrate the performance of the aircraft and its systems by flight tests. Flight tests should include those maneuvers that are reasonably representative of actual expected conditions and should cover the range of parameters affecting the behavior of the aircraft (e.g., wind speed, ILS, or GBAS characteristics, aircraft configurations, weight, center of gravity, and non-normal events).
3.4.2.1 The performance evaluation should verify the takeoff guidance system meets the centerline tracking performance guidance specified in section
3.2.3.6.
3.4.2.2 The applicant should demonstrate the system performance in non-visual conditions for:
• Normal operations,
• Engine failure cases, and
• Recovery from displacements from non-normal events.
3.4.2.3 The applicant should demonstrate this performance to have a satisfactory level of workload and pilot compensation. The methods defined in AC 25-7 or AC 23-8 are acceptable.
3.4.2.4 The applicant should show the takeoff guidance meets its stated performance criteria without the use of any outside visual references.
Note: The pilot may begin the takeoff using external visual reference, but from a speed no greater than 50% of V1, the pilot should follow the guidance commands as accurately as possible without using the external view. The applicant may need to safely integrate a view limiting means during the demonstration.
3.4.2.5 The takeoff guidance system performance demonstration should comprise a sufficient number of takeoffs to show the system meets its intended function under any foreseeable operating conditions. The number of takeoffs specified below is adequate for this compliance demonstration. Note, however, the FAA may require more demonstrations depending on aircraft characteristics and design, or difficulties encountered during testing.
• Twenty (20) normal, all-engine takeoffs, 3-10
AC 20-191
• Ten (10) completed takeoffs, with simulated engine failure at or after th e appropriate VFAILURE. The assessment must consider all critical cases, and
• Ten (10) rejected takeoffs, some with simulated engine failure just prior to V1, and at least one run with simulated engine failure at a speed less than VMCG.
Note 1: EASA’s AMC AWO 431 recommends a different number of takeoffs.
Note 2: An applicant may propose an alternate method of compliance in their certification plan or through issue paper. An example of an alternate method could be a reduced number of takeoffs for the takeoff guidance system performance demonstration with rationale for a reduction in flighttesting. Examples of rationale could include recognition for modeling and simulation testing done as part of the demonstration or a similar previously certified system with consistent flight test data.
3.4.2.6 The applicant may seek credit for an earlier demonstration of the takeoff guidance system. New testing of the aircraft may be necessary if the FAA deems credit for design similarity or performance is not appropriate. In cases where the aircraft’s performance dynamics associated with retarding the throttle to idle do not adequately simulate the dynamics of an engine failure, the FAA may require an actual engine shutdown.
3.4.2.7 The applicant should demonstrate the takeoff guidance system performance with headwinds for which credit is sought, and at least 150 percent of the tailwinds, and crosswinds for which credit is sought. Headwinds and crosswinds must be 15 knots or greater.
3.4.2.8 The applicant should demonstrate the operation does not exhibit any guidance or control characteristics that would cause the flight crew to react in an inappropriate or unsafe manner.
3.4.2.9 The demonstration aircraft should be configured with the appropriate instruments to record the time history of track with respect to the extended runway and the climb profile after liftoff to a reasonable point (e.g., departure end of the runway) as a means to show satisfactory performance.
3.4.2.10 The applicant should demonstrate no display or failure characteristics degrade the flight crew’s ability to adequately monitor takeoff performance.
Examples of takeoff performance parameters to monitor include acceleration, engine performance, takeoff speed callouts, attitude, and airspeed. The demonstration should include the entire takeoff, and transition 3-11
AC 20-191 to the enroute climb speed and configuration, for all normal, abnormal, and emergency situations.
3.4.2.11 The performance evaluation must demonstrate that the takeoff guidance system provides command information as lateral guidance, which will enable maintaining the aircraft on the runway during the takeoff roll through acceleration to liftoff or, during a deceleration to a stop during a rejected takeoff. The evaluation must also demonstrate the failure annunciation criteria of section 3.2.5, as well as the crew’s ability to immediately detect and mitigate non-annunciated failures.
3.4.2.12 The applicant should demonstrate the aircraft system response to loss of the takeoff guidance signal and appropriate annunciation to the flight crew.
3.4.2.13 Pilot Experience Levels. The applicant must demonstrate the takeoff guidance system meets the performance provisions in this chapter with pilots of varying experience levels.
3.4.2.14 Failure cases should typically be spontaneous and unpredictable on the subject’s or evaluation pilot’s part.
3.4.3 Safety Assessment.
In addition to any specific safety-related criteria identified in this chapter, the applicant must conduct a safety assessment of all aircraft’s takeoff system and associated components, considered separately and in conjunction with other systems, to show compliance with §§ 23.2500, 23.2510, 23.2605, 25.1309, 27.1309, or 29.1309 per the guidance contained in AC 23.1309-1, 25.1309-1, AC 27-1, or AC 29-2, respectively.
3.4.3.1 The applicant must consider the responses to failures of navigation facilities, taking into account pertinent criteria for navigation facilities.
3.4.3.2 The applicant’s documented safety analysis conclusions must include:
3.4.3.2.1 Pursuant to §§ 23.2500, 23.2510, 23.2605, 25.1309 , 27.1309, or 29.1309, a Functional Hazard Assessment (FHA) conducted in accordance with AC 23.1309-1, AC 25.1309-1, AC 27-1, or AC 29-2, respectively; results summary from the fault tree analysis, demonstrated compliance, and probability determinations for significant functional hazards.
3.4.3.2.2 Information regarding “alleviating flight crew actions” considered in the safety analysis. This information should list appropriate alleviating actions and be consistent with the test validation. If alleviating actions are identified, the applicant should describe the alleviating actions in a form suitable to aid in developing:
• Pertinent provisions of the Aircraft Flight Manual (AFM) 3-12
AC 20-191 procedures section(s)
• Flig ht Crew Operating Manual (FCOM) provisions, or equivalent
• Pilot qualification criteria (e.g., training requirements, Flight Standardization Board (FSB) provisions)
• Any other reference material necessary for an operator or flight crew to use the system safely.
3.4.3.2.3 Information to support preparation of any maintenance and preventive maintenance procedures necessary for safety, such as:
• Certification Maintenance Requirements (CMR),
• Periodic checks, or
• Other checks, as necessary (e.g., return to service).
3.4.3.2.4 Information applicable to lim itations, as necessary.
3.4.3.2.5 Information necessary for development of Non-normal Procedures.
3.5 AFM.
Pursuant to 14 CFR §§ 23.1581, 25.1581, 27.1581, or 29.1581, as applicable, an applicant must furnish AFM with each aircraft. The AFM should contain the following information:
3.5.1 The criteria and configurations used for the takeoff system demonstration.
3.5.2 Any constraints or limitations necessary for safe operation.
3.5.3 Acceptable normal and non-normal procedures.
3.5.4 The type of navigation facilities used as a basis for certification. This should not be taken as a limitation on the use of other facilities. The AFM may contain a statement regarding the type of facilities or condition s known to be unacceptable for use (e.g ., ILS localizer or GLS) .
3.5.5 Applicable atmospheric conditions under which the system was demonstrated (e.g., headwind, crosswind, tailwind).
3.5.6 All necessary performance, procedure, or configuration data to permit an operator to determine climb gradient and transition distances for safe obstacle clearance during a takeoff operation ; Note that this information need not be specifically included in the AFM if it is available to the operator using some other method acceptable to the 3-13
AC 20-191 operator and manufacturer (e.g., Flight Crew Operating Manual (FCOM), su pplementary performance information, separate AFM appendix).
3.5.7 For a takeoff system meeting the provisions of this chapter, the Normal Procedures, Normal Operations, or equivalent section, of the AFM should also contain the following statements:
• “The airborne system has been demonstrated to meet the airworthiness guidance of AC 20-191 (Chapter 3) for [specify the pertinent takeoff capability section(s) criteria met] when the following equipment is installed and operative:”
• “[list pertinent equipment]”
• “This AFM provision does not constitute operational approval for low visibility takeoff use of the system.”
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