Vertical Fields of View of View Primary Secondary Horiz 0 15 _15 0 NOM NOM ON Vertical Field Figure AC 29 MG 20-2: Primary and Secondary Vertical Fields of View (B) Section 29.1321(d). This regulatory provision is also closely related to §§ 29.771(a) and 29.1322 (if the instrument has a failure light or flag). The evaluation considerations discussed under those sections are applicable here as well.
Demonstrations and tests intended to show compliance should use production quality hardware and be conducted in a variety of lighting conditions (for example, dark, bright forward field, shafting sunlight). Due to the effect other rotorcraft electrical systems have on individual systems, compliance tests should be conducted in the rotorcraft, although there may be submittal of supporting data from laboratory testing to supplement rotorcraft testing.
(ix) Section 29.1322. The regulation specifically applies to lights. However, this section of the guidance also discusses audio alerts since there is simultaneous use with visual alerts to relay information to the pilot.
(A) With the advent of the integrated electronic multifunction display (MFD) systems, many manufacturers are presenting warnings, cautions, and alerts on MFDs instead of on separate annunciation panels. Consequently, this regulation is applied routinely to these integrated electronic displays.
(1) The use of red and amber for encoding purposes other than warnings and cautions can create confusion on these displays.
(2) Use red only as a warning annunciation for emergency operational conditions when immediate flight crew recognition and action is required.
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AC 29-2C, Chg 7 2/4/2016
(3) Use amber only for cautionary alerting and when immediate crew awareness is required and subsequent action may be required. Use white or another unique color for advisory annunciations of operational conditions that require flight crew awareness but may not require any action.
(4) Use green only to indicate safe operating conditions.
(B) Applicants should describe each warning, caution, and advisory light, including the expected pilot response. Consider establishing a well-defined color coding philosophy consistently across the cockpit. A well -defined and consistent color philosophy can greatly reduce the likelihood of confusion and interpretation errors.
(C) Evaluations should be conducted in the rotorcraft using actual hardware. Testing should include a variety of lighting conditions. It is important that the selected colors maintain integrity (for example, red looks red, amber looks amber) and discriminability (that is, colors can be distinguished reliably from each other) from all potential viewing angles and under all expected lighting levels.
(D) ) CAS panels should be easily seen and labels and messages easily legible in all lighting conditions. The lighting of the panel should balance with the rest of the cockpit. Modification of CAS panels, such as filtering for NVIS lighting, should be evaluated in all lighting conditions and pilot viewing angles to ensure the CAS legends are easily seen and legible.
(E) Audio Alerts, Cautions, and Warnings:
(1) It is important to use audio alerts judiciously. Keep the number of audio alarms to the minimum necessary to provide the desired result. Too many alerts can become confusing, annoying, increase pilot workload, and detract from a pilot’s primary flight responsibilities.
(2) Spoken (voice) alerts can have advantages over other forms of audio warnings since they convey specific information without the pilot having to interpret a tone or revert to a visual display to determine the exact failure.
(3) Regardless of the method chosen to present audio alerts, evaluate them to determine that they are readily detectable, easily heard under all ambient noise conditions, and quickly and correctly interpreted.
(i) Ensure that the alerting tone or voice message is of sufficient intensity (loudness) that it clearly stands out against all normal background noise.
(ii) Audio levels should be easily set and controlled in the event one alert is overly loud and distracting (for example, an audio alert is diverted from a cockpit speaker to headsets, adjustment of the alert’s volume may be necessary to compensate for the lower ambient noise of a headset vs. the ambient noise in a cockpit.
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(x) Section 29.1357(d). Applicants may choose to use methods similar to those employed for § 29.777 to demonstrate the ability of the pilot to identify and reach a specific circuit breaker or fuse when essential to safety in flight. Applicants should describe how to evaluate the ability of the pilot to identify the device readily and whether it is installed on a circuit breaker panel or controlled using an electronic device (such as a screen that can display the circuit breaker status and is controllable). The use of a circuit breaker or fuse as a switch to power-on or power-off equipment is not an acceptable design practice since the circuit breaker or fuse are not intended to function as a switch.
(xi) Section 29.1381.
(A) This regulation directly correlates with § 29.773. The primary purpose of cockpit lighting is to allow the crew to quickly see, accurately locate, identify, and, if appropriate, interact with displays or controls under both low and high ambient lighting conditions. It is especially important to be able to easily read all of the illuminated information that appears on the warning, caution, or advisories displays. All illuminated information must be easily identifiable, readable, and controllable by the pilot under all ambient lighting environments (direct sunlight to total darkness). Cockpit lighting evaluations should ensure that:
(1) There is enough lighting to make the performance of all related tasks easy to accomplish with a high level of speed and accuracy.
(2) The pilot is able to recognize and see any hazardous condition or potential hazards quickly.
(3) There is visual comfort.
(4) The lighting does not introduce glare, reflections, or flicker.
(5) The lighting system provides the pilot with the ability to balance illumination levels across all instruments and illuminated equipment.
(B) Each lighted component should be evaluated for uniform lighting and balance both individually and with all other illuminated instruments. This includes other displays, controls, alerting systems and secondary lighting, all of which should be compatible with each other. Dimming controls should be examined for uniform operation from full bright to off. The dimming ranges should be sufficient to obtain adequate readability throughout the entire operational lighting environment. Consider the number of dimming controls in the cockpit. The more dimming controls the pilot must operate, the greater the workload and likelihood of confusion and operator error;
therefore, dimming controls should be kept to the minimum required.
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AC 29-2C, Chg 7 2/4/2016 (C) Evaluate all control markings to ensure they are visible and evenly illuminated during both night and day operations. Font size variations (i.e., character size, width, and height) of the illuminated displays can affect readability and perceived brightness. Variations in font size may create perceived lighting imbalances in the cockpit (see ARP 4103 for recommendations). Lighting of one control should not interfere with viewing and identification of adjacent controls. Also, evaluate alerting lights for adequate attention-getting value for both day and night operations.
(D) Inspection of the cockpit for glare and reflections should be part of the evaluation procedure. Evaluations should ensure that glare and reflections do not cause visual discomfort, impair viewing out of the window, or interfere with other visual tasks. Lighting tests may be conducted in a cockpit mockup or simulator, if available.
Rotorcraft ground and flight tests should be conducted for both day and night operations.
(E) Ensure that all necessary instruments and panels are easily legible in all daylight conditions. This is particularly important for CAWS panels and annunciators.
Lit indicators or panels added to the rotorcraft should be assessed for legibility in all regimes used when assessing § 29.773.
(xii) Section 29.1523. This regulation addresses the criteria for determining minimum crew through the evaluation of pilot workload. Pilot workload is affected by the kind of operation being performed. So the kinds of operations being sought in
29.1525 should be considered when developing a showing of compliance. Pilot workload should consider the effect of installed systems on the following:
(A) flight path control, (B) collision avoidance, (C) navigation, (D) communications, (E) operation and monitoring of all essential rotorcraft systems, (F) command decisions, and (G) the accessibility and ease of operation of necessary controls by the appropriate crewmember assuming:
(1) Crewmember at flight or duty station.
(2) Normal, non-normal, and emergency conditions.
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(xiii) Section 29.1525. This regulation does not differentiate between the types of activities and areas that must be considered for the different kinds of operations for which the rotorcraft is approved. A source to assist with workload areas is Appendix D to part 25, coupled with the kinds of operations sought in accordance with § 29.1525.
In many cases, the minimum crew size is set by design, before any pilot workload evaluations are conducted.. This is a common practice, as the rotorcraft performance characteristics and cockpit configuration may resemble other FAA certificated models produced by the manufacturer.
(A) The process and level of evaluation for determining minimum crew for these situations will depend on the differences between already certificated models and configurations, and the model or configuration seeking certification. There needs to be a much more thorough evaluation for a new model than for a follow-on model or a model with minor modifications to the cockpit. Regardless of the level of difference or modification, evaluate all new or modified systems or new procedures for impact on the proposed minimum crew and the pilot or system interface. For rotorcraft with an established minimum crew, the purpose of this testing will be to corroborate by demonstration the predicted crew workload submitted by applicants in order to substantiate compliance with § 29.1523. Testing is also to provide an independent and comprehensive assessment of individual crewmember workload in a realistic operating environment. Any problems or issues identified with the system would most likely be resolved through design or procedural changes.
(B) Supplemental type certificate or amended type certificate modifications to avionics systems can significantly alter pilot workload, particularly if the modification adds new digital or electronic display and flight guidance technology into an older, mostly “round-dial” or analog cockpit. Avionics modernization modifications normally change pilot interaction with the rotorcraft. Integration of modern systems with existing systems can create unintended workload changes that create issues with the pilot’s primary function of flying the rotorcraft. For example, the performance capabilities of an older autopilot can hamper the new capabilities of a more modern GPS installed in a rotorcraft. Enabling the new capabilities by relying on the pilot to compensate for the inadequate performance of the integration is not recommended and may raise issues regarding the original minimum crew determination.
(C) Assessment of pilot workload is critical in evaluating the effectiveness of the integration of new technology with old. Net pilot workload may not increase or decrease, but it may change from simple aviation to one of systems management. The type of workload change should be assessed to evaluate the integration of systems.
Designs that incorporate special “pilot work-arounds” to account for incompatibilities between the new system and the existing systems may raise certification issues. These “pilot work-arounds” can create issues for operators trying to exploit the new capabilities of the system because they may not meet requirements in part 91 or part 135. Any time a design requires the pilot to compensate or change the way he operates in the cockpit to account for an integration issue, it should be questioned and corrected.
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AC 29-2C, Chg 7 2/4/2016 (D) Assess the workload through a logical process of analysis, measurement and demonstration. One acceptable analytical approach would assess workload as a percentage of time available to perform tasks (time-line analysis). Use an evaluation that collects objective and subjective data from subject pilots. The FAA and U.S Air Force developed a report for certification use to assist in evaluation of pilot workload. This report, “Assessment of Crew Workload Measurement Methods, Techniques, and Procedures,” Volume II (Report No. WRDC-TR-89-7006), provides guidance for selecting and using a number of subjective, physiological, and performance based workload measurement techniques.
(E) Depending on the level of integration required, use of a buildup approach may be helpful. Use of integrated bench tests, ground mock-ups, and if possible ground tests with an installed system helps identify issues early. Use of video and audio recordings can assist in analyzing pilot interactions with systems in all phases of testing including flight tests. Test flights should assess workload in all expected environments and for all operations requested in accordance with § 29.1525, part 91, and part 135.
(F An evaluation team is usually assembled when certificated systems and the proposed system are significantly different. Such a team includes applicant test pilots, certification authority test pilots, and, if the certification team deems it advisable, “line pilots” who routinely fly similar rotorcraft. The testing should be conducted using scenarios representative of the type of operations used for the rotorcraft. Testing should include various types of routes, navigational aids, environmental conditions and traffic densities. Give particular attention to tasks that involve planning and execution of emergency and non-normal procedures. When appropriate, also consider dispatch under the Master Minimum Equipment List in combination with other failures that are likely to result in significantly increased pilot and crew workload. Since display format and media also influence workload, the number, size, location, type of display, and presentation format should also be part of the overall evaluation.
(G) Discussion of minimum crew and the associated crew workload between the involved certification authorities and the applicant should take place early in the development cycle. These discussions should focus on identification of design features that are likely to affect crew workload. These design features need to be evaluated to ensure that they do not place excessive workload demands on any crewmember. Applicants should submit a test plan describing the details of the evaluation approach. Although developed for transport category airplanes, AC 25.1523 also contains useful information to address this rule.
(xiv) Section 29.1555(a). The intent of this regulatory provision is to ensure that pilots can quickly and unambiguously identify the function and understand the method of operation for each cockpit control. In conventional designs, the marking or labeling of controls may be accomplished using text that describes the function of that control. With the advent of MFDs and integrated systems, there is an emerging trend to integrate control functions into these displays. Many traditional systems (e.g., fuel, Page MG 20 -24
power, electrical, warning, and caution) are being integrated into a single display along with their associated control function and corresponding labels. The operation of these systems is accomplished via interaction with MFD controls (bezel switches, touch screens, etc.) and software control labels or icons that appear on the display screen.
Carefully evaluate the design of these labels and their associated meanings to determine that they adequately convey and completely define the control function and system operation. Often, a single text message or acronym may not be sufficient to completely describe the function and operation of that control.
(A) There has also been a growing trend to use icons rather than text on some of these displays. The symbol used can often be difficult to interpret or require training for the pilot to remember what it means. The overuse of symbols may require the pilot to revert to a manual for interpretation. Therefore, ensure that pilots will be able to identify control functions with an acceptable level of accuracy and consistency and in a timely manner. If icons are used, there should be no reduction in the level of pilot performance when compared with performance obtained using text labeling, and can be measured using time to interpret and accuracy of interpretation of that control function.
(B) There has also been a trend toward using multifunction controls (softkeys) more in rotorcraft. Pilots must be able to quickly and reliably identify the function controlled by these software labels. Pilots should be capable of performing controlrelated tasks to the same performance standards that would result from the use of conventional controls, unless the decrement is inconsequential and the design enables other significant performance gains or design simplifications.
(C) Evaluate control markings to ensure application of a logical and consistent labeling convention throughout the cockpit. The evaluation should also consider electronic control labeling, particularly as applied across all display pages. It is important that the expected pilot population immediately and clearly understands the terminology chosen for that control function. The evaluation should verify that the terms chosen conform to standardized aviation conventions. A list of standard terms and acronyms accepted by certification authorities can be found in Appendix O of RTCA Document DO-229C, “Minimum Operational Performance Standard for Global Positioning System/Wide Area Augmentation System Airborne Equipment,” dated November 28, 2001.
(D) It is also important to have consistent function labels. A function should have the same name regardless of the display page on which it appears.
Perform evaluations to determine consistent placement of labels on the same key of the display when pages are changed. The evaluator should ensure that all identical functions that are available across multiple screens or pages are consistently mapped to the same control to the maximum extent possible. Failure to consistently position soft-key functions can increase the time required to search and find a given function and increase the likelihood of entry error. One must also assess whether frequently used Page MG 20 - 25
AC 29-2C, Chg 7 2/4/2016 functions are readily accessible. In most cases, frequently used functions will require a dedicated control to provide adequate accessibility.
(E) Conduct all of the assessments as early in the program as possible. In addition, these assessments should include a sample of test pilots that are not familiar with the system. This can aid in the determination of the intuitiveness of labels and potential for misinterpretation.
i. Sample HF Compliance Matrix. Figure AC 29-2 MG-20–3 shows a sample matrix and is not all-inclusive. An actual matrix will likely be more complex and longer depending on the type of project.
Regulatory Requirement Compliance Documentation § 29.771. Pilot compartment.
For each pilot compartment -
(a)The compartment and its equipment must allow each pilot to perform his duties without unreasonable concentration or fatigue;
√ √ Report No.
60-002 § 29.777. Cockpit controls.
Cockpit controls must be -
(b)Located and arranged with respect to the pilots’ seats so that there is full and unrestricted movement of each control without interference from the cockpit structure or the pilot’s clothing when pilots from 5’2” to 6’0” in height are seated.
√ √ Report No.
60-004 § 29.1321. Arrangement and visibility. (g) - If a visual indicator is provided to indicate malfunction of an instrument, it must be effective under all probable cockpit lighting conditions.
√ √ √ Report No.
60-004 § 29.1381. Instrument lights.
The instrument lights must - (a) Make each instrument, switch, and other devices for which they are provided easily readable;
and… √ √ Report No.
60-012 Page MG 20 -26
§ 29.1381. Instrument lights.
The instrument lights must - (b) Be installed so that - (1) Their direct rays are shielded from the pilot's eyes and (2) No objectionable reflections are visible to the pilot.
√ √ Report No.
60-010 § 29.1555. Control markings. (a) Each cockpit control, other than primary flight controls or control whose function is obvious, must be plainly marked as to its function and method of operation.
√ √ √ Report No.
60-010 Figure AC 29 MG 20-3. Sample HF Compliance Matrix Page MG 20 - 27
CHAPTER 3
AIRWORTHINESS STANDARDS
TRANSPORT CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG) AC 29 MG 21 GUIDANCE ON CREATING A SYSTEM LEVEL FUNCTIONAL HAZARD ASSESSMENT (FHA).
a. Purpose.
(1) This MG provides guidance for developing a system level functional hazard assessment (FHA) and is derived from the Society of Automotive Engineers (SAE) Aerospace Recommended Practices Document (ARP) 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment. This MG helps answer the questions of when and how to complete a system level FHA. The FHA approach provided in this MG utilizes the Air Transportation Association (ATA) chapter code structure. In this MG, we provide a FHA table format that lists the most commonly used functions for each major system type and associated information identified in ARP 4761.
(2) This MG describes acceptable guidance for developing an FHA for an aircraft and its systems, in support of compliance with 14 CFR 29.1301 and 29.1309, and other applicable regulations. An applicant for a type certificate (TC), amended TC, supplemental type certificate (STC), amended STC, and technical standard order authorization (TSOA) may use SAE ARP 4754a, Guidelines for Development of Civil Aircraft and Systems, dated December 21, 2010, in conjunction with applicable ACs, to comply with the regulations.
b. References and Related Documents.
(1) Applicable regulations: 14 CFR 29.1301 and 29.1309.
(2) Applicable ACs.
(i) AC 20-115C, Airborne Software Assurance.
(ii) AC 20-152, RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware.
(iii) AC 20-170, Integrated Modular Avionics Development, Verification, Integration, and Approval Using RTCA/DO-297 and Technical Standard Order-C153.
(3) Industry Standards (or latest FAA recognized version).
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(i) RTCA Document DO-178CB, Software Considerations in Airborne Systems and Equipment Certification, dated December 13, 2011.
(ii) RTCA Document DO-254, Design Assurance Guidance for Airborne Electronic Hardware, dated April 19, 2000.
(iii) RTCA Document DO-297, Integrated Modular Avionics (IMA) Development Guidance and Certification Considerations, dated November 8, 2005.
c. Background. The FAA recognizes the importance of timely completion of an FHA to minimize TC, amended TC, STC, amended STC, and TSOA project delays and potential risks of redesigns required late in a project because of information obtained from the completed FHA. Applicants are expected to not only properly complete FHAs as early as possible to minimize the risks described above, but also obtain FAA acceptance of the FHAs.
d. When to create an FHA. The FAA expects a discussion of the FHA take place during the very early stages of the TC, amended TC, STC, amended STC project (i.e., during the Familiarization Briefing). This will provide the FAA with the necessary design safety aspects information while the development is still in the conceptual and requirements definition phases. Since the FHA process is designed to provide the system level safety and derived requirements, it is imperative that the applicant obtain FAA acceptance of the FHA as early as possible in the systems development (i.e., prior to submitting the certification plan). This will minimize the risk of the applicant’s design requiring changes late in the program to satisfy safety requirements obtained from the completed FHA.
e. How to create an FHA.
(1) The process to create an FHA can be considered fairly complicated if doing it for the first time. T his guidance presumes that an applicant is familiar with ARP 4761 and is looking for some additional guidance in recognizing some of the likely functions of each system and the associated failure conditions (FC) that should be reflected in a FHA. The table in Figure AC 29 MG 21- 1 provides a snapshot of considerations an applicant should address when examining their design for a systematic safety review.
This table is not a complete list nor are the FCs listed in the figure applicable for all designs.
(2) One additional item is the need to include a complete list of assumptions made when developing the FHA. These assumptions may include the intended aircraft (single or dual engine, existing certificated interfacing equipment), type of operation
(e.g., IFR, VFR, category A), crew composition (e.g., single pilot, dual pilot), etc. These should be listed in the front of the document prior to the functional failure conditions matrix.
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(3) The set of tables in Figure AC 29 MG 21-1 provides examples of a format for the system level FHA as identified in the reference ARPs. Guidance is also included for typical entries for the columns with a short description of each as follows:
(i) ATA. This column was taken from the “Joint Aircraft System/Component (JASC) Code Table” document to provide a complete list of systems defined on an aircraft. It is not a typical column entry for an FHA and should not be considered as such. However, it provides systematic approach to identify various aircraft systems.
(ii) Function Description. A concise description of the sub-functions for each top level system. For example, the oil system is made up of sub-functions such as oil pressure, oil temperature, and oil quantity.
(iii) Failure Condition (FC). A goal of this guidance is to encourage the author of an FHA to use the verbiage established in this guidance as a means to provide some standardization and minimize confusion when reviewing FHAs. Typical entries in this column include “Loss of …”, “Unannunciated loss of …”, “Misleading data to the flight crew …”, “Malfunction of …”, along with environmental conditions (e.g., day and night VFR, IFR, Icing).
(iv) Phase of Operation. In this column, the typical entries are Hover, Takeoff, Climb, Cruise, Descent, Approach/Landing, or any combination as appropriate.
(v) Effect of the Failure on the Aircraft, Crew and Occupants. Describe the effects of the failure on the aircraft, aircraft system, flightcrew workload, and occupant safety and comfort. The inclusion of mitigating design features within this column entry is not appropriate and should not be included. Instead, any mitigation required to meet the failure classification should be included in the System Safety Assessment. Each type of effect, not only the effect on flight crew workload, should be analyzed. The effect on the degradation of the system should not be overlooked, as this can result in a higher classification.
(vi) Classification of the FC. This is typically the most challenging entry in the process since it is completely qualitative and requires input from multiple subject matter experts. It requires the participation of various disciplines such as safety analysts, design engineers, engineers responsible for software or complex hardware, human factors specialists, and flight test personnel. After the applicant has determined the classification levels, the results must have concurrence from the certification authority.
This may require lengthy discussions and should occur very early in the certification process.
(A) Some appropriate entries are no effect (NE), minor (MIN), major (MAJ), hazardous (HAZ) or catastrophic (CAT). The definition for each can be found in section 29.1309 of this AC. Note that this column in Figure AC 29 MG 21-1 was intentionally left blank because of the variation of appropriate classifications for a similar failure condition.
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