AC 27-1B, Chg 7 2/4/2016
(iv) Markings must follow requirements of §§ 27.1543 through 27.1555.
(2) Graphical and numerical-only displays of parameters or information should follow the guidance in section d. (1)(ii) above. Providing a numerical readout along with graphically presented information provides the pilot with complementary data of a specific value coupled with the awareness of where in the operating range that value resides.
(i) There should be graphical display of powerplant pressures and temperatures, fuel levels and pressures, and speeds.
(i) There should also be graphical presentation of other parameters with a range of normal if the pilot needs to monitor where a parameter is or is changing relative to a limit.
(C) Part-time vs. full-time display of information
(1) Powerplant instruments required by § 27.1305 should be displayed full time (i.e., continuous display). However, due to space limitations or display system design, EDS displays that allow for the de-selection of secondary powerplant instruments (e.g., engine oil temperature and pressure, transmission oil temperature, electrical information) required by § 27.1305 may be acceptable. There should be continuous display of primary power information (TQ, MGT, Ng, or their equivalents) and Rotor tachometer (Nr and Np).
(i) In order to allow the de-selection or part-time display of these parameters, compensatory features should be designed and provided to alert pilots to select and monitor § 27.1305 instruments prior to the parameter reaching a cautionary or warning limit.
(A) Algorithms and monitoring software can provide the capability to alert pilots about possible anomalies in a parameter's behavior. Pilots can then select the appropriate display, monitor the situation, and mitigate the situation prior to it becoming an abnormal condition.
(B) The monitoring function should automatically provide the same level of monitoring that would exist if there were continuous display of the individual engine gauges.
(1) To show compliance using part-time display of § 27.1305 required indicators, the applicant needs to show equivalence. Coordinate with engine and powerplant specialists since they will need to assist in the evaluation of the monitoring algorithm parameters. Depending on the strategy employed, the engine manufacturer may also need to be involved. Additionally, coordinate early with the FAA since there will need to be an equivalent level of safety.
(ii) System displays. Display of system information (e.g., hydraulic system information, electrical system information) other than powerplant information may be combined onto an EICAS or IIDS display or displayed on separate displays.
(A) Crew Alerting System (CAS) and Caution Advisory Warning System (CAWS). EDSS may include CAS message windows or CAS messages may display on a separate display. CAS messages must be easily seen and legible in all lighting conditions. The messages or labels must be easily understandable and use standardized acronyms or labels. Display of CAS messages should be located as close to the pilot's central line of vision as possible unless there is a Master Caution or Master Warning indicator in the pilot's primary field of view.
(1) Managing Messages and Prompts. The following general guidance applies to all messages and prompts:
• There should be an indication when there are additional messages not displaying that are in a message queue.
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(i) Within levels of urgency, messages should display in logical order.
(iii) If the length of the information for the message, prompt, or response options does not display on a single page, there should be an indication that additional message information
(2) The CAS display should be large enough to generate a display of all possible warnings that are in a worst-case scenario. The design should provide for sufficient space to display all possible warnings on the screen at once. To decrease the amount of cascading warnings, use algorithms to suppress subsequent cascading warnings that would appear because of an event. For example, loss of an engine could lead to cascading messages of warning-level conditions that resulted from the engine loss. Unless the pilot has to perform separate procedures to correct subsequent warnings from the procedures needed to handle the engine loss, there is no need to present them to the pilot.
(3) CAS message priority.
(i) If displaying CAS messages in a window within an EDS display, prioritize how they will appear. Normally, presentation of warning messages takes precedence over caution and advisory messages. There can be prioritization of new warnings by importance, recency, or other prioritization scheme.
(i) Caution message priority should be defined and easily understood by the pilot. Scrolling and paging-over to read overflow Caution messages is allowed. The scrolling function and control must be easily identified and used without undue concentration.
(7) Mission or ancillary displays.
(i) Displays added to the cockpit for specialized uses by a mission crewmember and not the pilot, such as FLIR displays, should be located outside of the pilot's secondary field of view, if possible, so as not to distract the pilot from flying the rotorcraft.
(ii) Displays of non-required information not integrated into an EDS but intended to be used by the pilot should have all of the attributes and characteristics of an EDS. These displays can be located within the pilot's secondary field of view but not in the primary field of view and should not displace the display of required information.
(A) Display of non-required information should be assessed to ensure it does not provide misleading information to the pilot or information contrary to that provided by a required source. For example, an enhanced vision display should not display cues regarding rotorcraft position relative to hazards or navigation waypoints that are contrary to other information provided on the EDS.
(B) The intended function of a non-required information display should be specific and defined. For example, "Increase pilot situation awareness" is not an acceptable statement of intended function. A better statement of intended function is "Increase pilot awareness of hazard location relative to the rotorcrafti
(8) Reversionary Modes.
(i) General. Because EDS displays can integrate numerous required flight, powerplant, and system information into single displays, there is a greater opportunity for a fault to lead to the loss of the display of multiple parameters. To mitigate this, the use of reversionary modes and displays can ensure the continued display of required parameters. Reversionary modes are sometimes referred to as "compressed displays" or "composite displays."
(iI) Methodology.
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AC 27-1B, Chg 7 2/4/2016 (A) IFR. Refer to 14 CFR Appendix B to part 27 and Appendix B of this AC for information on the IFR requirements for normal category rotorcraft. Per Appendix B to part 27, the display of information essential for continued safe flight (i.e. attitude, altitude, airspeed, and heading) must be immediately available to the pilot flying without crewmember action after any single or combination of failures not shown to be extremely improbable. Automatic reversion displays allows this required information to be immediately available to the pilot flying without crewmember action. In IFR designs, it is expected that the first display failure should have no impact on the ability of the pilot to continue safe IFR flight to the planned destination.
(1) For rotorcraft with a certificated dual pilot installation, the copilot's instruments are allowed to be used as a standby source of primary information provided they can be used without undue concentration or fatigue by the pilot. For EDS displays, specific issues, such as the following, should be addressed:
(i) Pilots should easily see and interpret the displays from their normal seated position with minimal head movement.
(A) The copilot's systems should be within the pilot's secondary field of view.
(B) The display characteristics should support off-angle viewing in all lighting conditions.
(i) Pilots should be able to easily manipulate the displays with one hand from their normally seated position. Pilot access of the displays and controls must meet the requirements of § 27.777 when used by the pilot flying as primary flight information.
(2) Automatic reversion allows required information to remain visible to the pilot flying without crewmember action. The format and arrangement of the reversionary mode is discussed below.
(i) Automatic reversion should provide the required information within one second of the detected failure of a display or the display's inability to provide the information.
(II) Only for an undetectable loss of the display resulting from a backlight failure or broken display screen is a single button push by the pilot acceptable. The pilot should be able to recover the lost display of information within one second. However, the design of the display should be such that these types of failures are extremely improbable.
(B) VFR. For normal category rotorcraft certificated for VFR only, pilot action to enter a reversionary mode is acceptable.
(1) Pilots should be able to recover the information within one second with a single action.
(2) The reversionary control should be clearly marked and easily identifiable.
(3) The reversionary mode must provide all required information in an easily seen and readable format.
(ili) Arrangement. Arrangement of information in a compressed or composite mode must follow the requirements of § 27.1321 and should follow the guidance in section 27.1321 of this AC as closely as possible.
(A) Presentation of primary flight information should remain the same.
(B) Presentation of navigation information should provide for required information in as similar a location as possible as a normal display.
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(C) Powerplant and required system information should be arranged in a manner that is easily accessed and readable.
(D) CAS messaging should be displayed with the ability to display all possible warnings without overflow.
(iv) Reversionary mode display format.
(A) Format of the primary flight information should not change.
(B) HSI presentation in a reversionary mode should provide the same usability and function as the non-reversionary mode. Navigation information should still be available and as close to the same format as non-reversionary mode as possible.
(C) Presentation of primary powerplant information the pilot uses to set and monitor power should be prominent and graphically displayed.
(D) Presentation of powerplant information pilots use to assess the health and ability of the powerplant to develop power can revert to numerical displays if needed. Display of these parameters numerically should include secondary cueing for the pilot in the event a parameter exceeds a cautionary or limit value. For example, the numerical digit or field should provide a visual cue regarding its status as it would in a normal display (see § 27.1322).
e. System Requirements.
(1) All parameters in EDS displays are to be designed in accordance with the relevant TSOs.
TSOA does not mean that the function or hardware meets the airworthiness certification requirements for the rotorcraft in which it is to be installed.
(2) A safety assessment should be provided as part of finding compliance with § 27.1309. The following sections of this AC contain guidance on safety assessments:
• Section 27.1309, paragraphs d. (Safety Assessment), f. (Software), and g. (Airborne Electronic Hardware (AEH)).
• MG 21 (FHA).
(3) Special considerations when determining failure condition classifications. Consideration should be given to the type of operation that the system is intended to support. For example, failure condition classifications for IFR installations are generally higher than VFR. Information contained on a PFD is usually more critical, in most cases, than information on a MFD.
(1) VER.
(A) In a rotorcraft certificated to operate only under VFR, misleading information will typically have a higher hazard categorization than a loss of information. The design should provide mitigation to both as much as feasible since VER operations at night can occur in areas that do not provide pilots with good visual cues regarding the horizon or ground features.
(B) PFD. Display of any non-required information such as synthetic vision should not display misleading information. Loss of non-required information should not lead to confusion or affect the ability of the pilot to access or assess required flight information.
(C) Display of powerplant information. 14 CFR 27.1305 contains the required powerplant instrument data to be displayed. Although each item is required, care should be taken with the loss of the following, as applicable: low fuel warning, oil pressure warning for each gearbox, tachometer, and OEI power levels.
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AC 27-1B, Chg 7 2/4/2016
(ii) IFR. Regulations for rotorcraft certificated for IFR operations are found in Appendix B to part 27.
(iii) Field-Loadable Software (FLS) as part of the TC/STC/ASC/ASTC installation. FLS is software that can be loaded without removal of the equipment from the rotorcraft installation. FLS can refer to either executable code or data. FLS might also include software loaded into a line replaceable unit (LRU) or hardware element at a repair station or shop. When obtaining certification approval for utilization of the FLS capability, refer to the guidance in FAA Order 8110.49.
(iv) Navigation Database Qualification. For area navigation equipment, the navigation database is an essential component of the ability of the equipment to perform its intended function.
RTCA Document DO-200A, Standards for Processing Aeronautical Data, contains guidelines pertaining to the navigation database. Consider obtaining a Type 2 Letter of Authorization for databases used for Localizer Performance with Vertical Guidance in addition to the required documentation. See AC 20-153A for additional information.
(4) Environmental qualification. EDS displays should meet the appropriate RTCA Document DO- 160G environmental qualifications for rotorcraft. Rotorcraft environments can be more hostile than fixedwing environments. Give special attention to the temperature and vibration qualifications. See section
27.1309 of this AC for more guidance.
(i) Cooling.
(A) Perform cooling evaluations for the installed components.
(B) Temperature Survey to Determine Proper Cooling of EDS Components.
(1) Equipment Requiring Cooling Test. As with any avionics equipment, good engineering judgment may deem that all components of the EDS should have an in-flight temperature survey performed to ascertain that the thermal environmental tolerance of the system components is not exceeded. Usually, the following general guidelines may be used to aid in determining when an in-flight temperature survey is warranted.
(1) Equipment specified by the manufacturer to require forced air cooling (by an airframe-mounted system) usually requires a temperature survey.
(I) Equipment that is not specified as requiring forced air-cooling may usually have its critical thermal environment substantiated by laboratory testing.
(2) Temperature Survey Testing. The temperature tests for the EDS units should consist of a short-term test of approximately 30 minutes, which accounts for a rotorcraft that has heat-soaked on the ramp. A factor of 25° F should be added to the maximum corrected temperature to account for "greenhouse effect." A long-term test should be accomplished at various altitudes and limiting (low and high) airspeeds. All avionic equipment should be turned on during the long-term tests, and the cockpit panel lights should be operated at full intensity. The environmental control unit or air-conditioning system should not be operated during the short-term and long-term tests; however, any windows or vents, which are part of the basic TC of the rotorcraft, may be utilized to ventilate the pilot's stations during the long-term test. Both of these tests should be corrected to the maximum temperature for which the rotorcraft is certificated (maximum outside air temperature) and a standard lapse rate for altitude (i.e.,
3.6° F/1,000 feet), as specified in this guidance (refer to section 27.1309 of this AC). This lapse rate should be applied regardless of the hot day sea level temperature the applicant chooses to certificate for operation. If an airframe cooling system is necessary to keep the display units within acceptable temperature limits, then the pilot(s) must be made aware of a failure or malfunction of this required cooling system. Some type of cockpit visual annunciation with the capability to perform a preflight test is usually utilized to fulfill this requirement.
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(ii) HIRF. Perform HIRF testing in accordance with § 27.1317 and the guidance in section
27.1317 of this AC.
(5) Night vision imaging system (NVIS) lighting. If the EDS is designed with night vision goggle (NVG) compatibility for installation in a NVIS lighting modified cockpit, refer to MG-16 of this AC and RTCA Document DO-275, "Night Vision Imaging System Lighting," for lighting performance guidance.
Modifications to EDS displays should preserve color uniformity across the cockpit. Most EDSs incorporate color; as a result, in order to preserve the EDS colors close to the rotorcraft's designed colors, the NVIS lighting system should be modified to be compatible with Class B NVGs. Lighting compatible with Class A NVGs may not provide the correct color hues (e.g., red colors tend to look orange or amber, yellow colors tend to have a green tint in daylight, etc.).
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CHAPTER 3
AIRWORTHINESS STANDARDS
NORMAL CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG) AC 27 MG 20. HUMAN FACTORS (HF)
a. Background. The purpose of this miscellaneous guidance section is to provide applicants with general guidelines on how to approach compliance with 14 CFR part 27 sections that have provision relating to human factors (HF) or human performance. The intent of this guidance is to assist in understanding the HF implications of the more frequently referenced regulations. This guidance also provides examples of how to address HF implications when demonstrating compliance with these regulations. This information should help determine whether HF-related requirements have been adequately addressed.
(1) Developments in technology and the affordability of advanced avionics provide for the installation of sophisticated systems into rotorcraft. As a result, the level and characteristics of pilots' interactions with cockpit and avionics systems is changing, particularly for rotorcraft that are not capable of operating under instrument flight rules (IFR). Additionally, integrating new technologies, such as a satellite-based augmentation system (SBAS) or wide area augmentation system (WAAS) increases the rotorcraft's avionics capabilities to perform functions and operations it was not previously capable of performing. These new capabilities create HF issues related to pilot workload that should be evaluated along with the systems integration. Poor system integration often results in applicants relying on the pilot to work around a design issue. This approach, coupled with complex pilot interfaces, can lead to pilot error and may inhibit the pilot's ability to recover from errors without undue concentration or fatigue.
Some HF implications are straightforward and easily complied with, while others may be more complex.
A partial list of rules that have HF implications, particularly those that relate to pilot workload, is included in paragraph b. (2) below. The HF guidance contained in this MG is consistent with the goals identified in the FAA Industry Guide to Product Certification (Jan 99) and the FAA Industry Guide to Avionics Approvals (Apr 01).
(2) The requirements of part 27 Subparts A through G apply to rotorcraft approved for both VFR and IFR operations. Rotorcraft approved for IFR operations must also meet the requirements of Appendix B to part 27 (Airworthiness Criteria for Helicopter Instrument Flight). Additionally, Appendix D to part 25 contains information regarding criteria for minimum crew determination for airplanes operating under FR conditions, which may be beneficial for determinations in rotorcraft.
(3) As a normal part of the certification project, the applicant and the FAA AUTHORITY usually establish an early and formal written certification plan on the certification basis, the methods of compliance, and the schedules for completing the certification project. Both parties should ensure coverage of the HF aspects of the rules in the plan. If the applicant chooses, it can submit a separate human factors certification plan. These early discussions can reduce the applicant's time and cost to obtain certification.
(4) The flight test team usually performs the HF evaluations. However, HF engineers and test pilots should be involved early in the design, during cockpit integration tests, and early in the humanmachine interface evaluations. Identify and develop pilot-system interfaces and interactions in the basic design to reduce the risk of having an interface issue identified after the system design is final.
b. Related Regulations and Documents.
(1) HF related regulations. Not all of the regulations listed require specific HF means of compliance. Some are self-explanatory and straightforward, while compliance with others is determined during flight test as part of their normal course of testing and evaluation. However, each regulation should be noted in the certification plan.
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AC 27-1B, Chg 7 2/4/2016
(2) Many of the regulations with HF implication are also within the purview of other engineering disciplines; therefore, demonstration of compliance with 14 CFR part 27 may include more than one engineering discipline. For regulations with HF implications, consider identifying which discipline or individual will be responsible for demonstrating compliance with these regulations. The following contains a partial list of part 27 regulations related to human factors and performance.
14 CFR Section Title
27.2(a)(1)-(2) Special retroactive requirements.
27.33(b) (3), (c)(2), (e) Main rotor speed and pitch limits.
27.45(a), (f) General.
27.51(a) Takeoff.
27.75(a), (b) Landing.
27.141(b) General.
27.143(a), (d), (e) Controllability and maneuverability.
27.151(a), (b) Flight controls.
27.161(b) Trim control.
27.171 Stability: general.
27.177 Static directional stability.
27.239 Spray characteristics.
27.251 Vibration.
27.561(a), (b) General.
27.611 Inspection provisions.
Stability augmentation, automatic, and power-
27.672(a), (b), (c)(1)(2) (3) operated systems.
27.679(a), (b) Control system locks.
27.685(d)(10) Control system details.
27.771 (a), (b), (c) Pilot compartment.
27.773(a)(1), (b) Pilot compartment view.
27.777(a), (b) Cockpit controls.
27.779(a), (b) Motion and effect of cockpit controls.
27.783(b) Doors.
27.785 Seats, berths, litters, safety belts, and harnesses.
27.801(a), (b), (d) Ditching.
27.805 (b) Flight crew emergency exits.
27.807 (a), (b), (d) Emergency exits.
27.859(g) (3) Heating systems.
27.863(c) Flammable fluid fire protection.
27.865(b)(1)(2), (c)(3)(5) External loads.
27.901(b)(2)(5) Installation.
27.921 Rotor brake.
27.955(c) Fuel flow.
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14 CFR Section Title 27,995(b) Fuel valves.
27.999(b)(2)(3)(i) Fuel system drains.
27.1141(a), (c), (d) Powerplant controls: general.
27.1143(b), (c), (d) Engine controls.
27.1145(a), (b) Ignition switches.
27.1147 Mixture controls.
27.1151 Rotor brake controls.
27.1189(b)(c) Shutoff means.
27.1301(a), (b) Function and installation.
27.1303 Flight and navigation instruments.
27.1305 Powerplant instruments.
27.1309(a), (b), (c) Equipment, systems, and installations.
27.1321 Arrangement and visibility.
27.1322 Warning, caution, and advisory lights.
27.1329 Automatic pilot system.
27.1335 Flight director systems.
27.1337 (b), (e)(2) Powerplant instruments.
27.1351(d) General.
27.1357(d) Circuit protective devices.
27.1361(a), (c) Master switch.
27.1367(b), (c) Switches.
27.1381 Instrument lights.
27.1383(b), (c) Landing lights.
27.1401(a)(1) Anticollision light system.
27.1411(a), (b)(1) General.
27.1415(b), (d) Ditching equipment.
27.1501(b) General.
27.1523 Minimum flight crew.
27.1525 Kinds of operations.
27.1541(b)(1) General.
27.1543(b) Instrument markings: General.
27.1545 Airspeed indicator.
27.1549 Powerplant instruments.
27.1555 Control markings.
27.1559 Limitations placard.
27.1561 Safety equipment.
27.1583 Operating limitations.
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AC 27-1B, Chg 7 2/4/2016 14 CFR Section Title Appendix B to Part 27, IV Static longitudinal stability.
Appendix B to Part 27, VI Dynamic stability.
Appendix B to Part 27, VIl Stability augmentation system (SAS).
Appendix B to Part 27, VIII Equipment, systems, and installation.
(3) Advisory Circulars (AC) and Related Documents (refer to the current version).
Note: ACS, orders, and policy statement memoranda are available on the FAA website: www.faa.gov.
(i) ACS.
AC Title 20-175 Controls for Flight Deck Systems 21-40 Guide for Obtaining a Supplemental Type Certificate 27-1 Certification of Normal Category Rotorcraft (Sections related to Appendix B and the requirements within Appendix B identified in the certification plan with HF/HP issues) 29-2 Certification of Transport Category Rotorcraft (Sections related to Appendix B and the requirements within Appendix B identified in the certification plan with HF/HP issues) Page MG 20 -4
(ii) Related Documents.
Document Title SAE- ARP 4155 Human Interface Design Methodology for Integrated Display Symbology SAE-ARP 4033 Pilot-System Integration SAE-ARP 4102 Flight Deck Panels, Controls, and Displays SAE-ARP 4102-7 Electronic Displays SAE-ARP 4927 Integration Procedures for the Introduction of New Systems to the Cockpit SAE-ARD 50019 Human Engineering Issues for Enhanced Vision Systems DOT/FAA/RD-93/5 Human Factors for Flight Deck Certification Personnel DOT/FAA/AM-13/21 Multi-Function Displays: A Guide for Human Factors Evaluation
c. Scope.
(1) The objective of this MG is to provide guidance regarding the regulatory HF components that should be considered during a certification project for rotorcraft. While applicants are the main target audience, this guidance can be used by all FAA project team members including:
(i) Aircraft Evaluation Group (AEG) inspectors,
(ii) avionics engineers, (ilI) project managers,
(iv) flight test pilots and engineers,
(v) HF specialists and engineers,
(vi) propulsion engineers, and
(vii) systems engineers.
(2) This MG is general and high level, covering the HF aspects of certificating a rotorcraft or system installation on a new or previously-certificated normal category rotorcraft. It is intended to guide applicants and certification engineers on what they should consider regarding HF during project planning and execution Page MG 20 - 5
AC 27-1B, Chg 7 2/4/2016
d. System Description.
(1) General. Develop a system description with enough detail to provide for a common understanding of the design, function, and operation of the system. Thoroughly detail any new or novel features, interfaces, controls, or other pilot-system interfaces that pilots will use.
(2) Intended function (§ 27.1301).
(i) Describe the intended function of the major pilot-system interfaces. In order to assess the potential hazards posed by the installation of a system, there must be a clear understanding of the function provided by the system and the declared intended function. Accomplish this by providing a detailed description of how the system supports the specified function(s). For example, describing a function or component, such as a display, as "for pilot situation awareness only" or "for situational awareness only" is not adequate regardless of whether the function or component is required by the regulations. A better example for a non-required function might be "to increase terrain awareness."
Identify the following items, as appropriate, focusing on new or unique features that affect the crew interface or the allocation of tasks between the pilot and the rotorcraft systems:
(A) The intended function of the system from the pilot's perspective (coupling between the pilot and the system).
(B) The role of the pilot relative to the system.
(C) The degree of integration or independence with other flight deck equipment.
(D) The novelty of the system or features of the system.
(E) The criticality of the system and alerting mechanism.
(F) Methods to reduce the occurrence and consequences of crew error when interacting with the system.
(G) The system features accessible to the pilot other than those normally considered needed for flight. For example, whether field loadable software, maintenance, and configuration functions are accessible by the pilot in flight and on the ground, or whether they are accessible only by maintenance personnel.
(ii) Use the following information to evaluate whether the intended functions and associated tasks are sufficiently detailed and specific:
(A) Whether each feature includes a statement of the intended function and a description of the task associated with this feature.
(B) Whether there are assessments, decisions, or actions required by the pilot for these intended functions.
(C) Whether other information is to be used in conjunction with these intended functions (for example, other cockpit systems), in combination with the system.
(D) Whether the operational environment in which these intended functions are to be used is adequately described (e.g., VFR, IFR, phase of flight).
(3) Cockpit layout (§§ 27.771, 27.773, 27.777, 27.1303, 27.1305, 27.1321, 27.1329, and Appendix B to part 27).
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