·        The minimum flight crew must be established so that it is sufficient for safe operation, considering

        (a)   the workload on individual crewmembers;

        (b)   the accessibility and ease of operation of necessary controls by the appropriate crewmember; and

        (c)   the kind of operation authorized under § 25.1525.

        The criteria used in making the determinations required by this section are set forth in Appendix D. [14 CFR 25.1523]

        See also: 14 CFR 23.1523, 27.1523, and 29.1523 which are worded slightly differently.

·        This section applies to installed systems and equipment intended for flightcrew members' use in operating the airplane from their normally seated positions on the flight deck. The applicant must show that these systems and installed equipment, individually and in combination with other such systems and equipment, are designed so that qualified flightcrew members trained in their use can safely perform all of the tasks associated with the systems' and equipment's intended functions. Such installed equipment and systems must meet the following requirements: [14 CFR 25.1302]

        (a)   Flight deck controls must be installed to allow accomplishment of all the tasks required to safely perform the equipment's intended function, and information must be provided to the flightcrew that is necessary to accomplish the defined tasks.

        (b)   Flight deck controls and information intended for the flightcrew's use must:

                (1)   Be provided in a clear and unambiguous manner at a resolution and precision appropriate to the task;

                (2)   Be accessible and usable by the flightcrew in a manner consistent with the urgency, frequency, and duration of their tasks; and

                (3)   Enable flightcrew awareness, if awareness is required for safe operation, of the effects on the airplane or systems resulting from flightcrew actions.

        (c)   Operationally-relevant behavior of the installed equipment must be:

                (1)   Predictable and unambiguous, and

                (2)   Designed to enable the flightcrew to intervene in a manner appropriate to the task.

        (d)   To the extent practicable, installed equipment must incorporate means to enable the flightcrew to manage errors resulting from the kinds of flightcrew interactions with the equipment that can be reasonably expected in service. This paragraph does not apply to any of the following:

                (1)   Skill-related errors associated with manual control of the airplane;

                (2)   Errors that result from decisions, actions, or omissions committed with malicious intent;

                (3)   Errors arising from a crewmember's reckless decisions, actions, or omissions reflecting a substantial disregard for safety; and

                (4)   Errors resulting from acts or threats of violence, including actions taken under duress.

        See also: Chapter 8 Intended Function; Chapter 9 Error Management, Prevention, Detection, and Recovery

·        Relying on a requirement of “train to proficiency” may be unforeseeable, economically impracticable, or unachievable by some pilots without excessive mental workload as compensation. [AC 27-1B, AC 27.1303b(4)(ii)(B)(1); AC 29-2C, AC 29.1303b(4)(ii)(B)(1)]

·        The process and level of evaluation for determining minimum crew determination for these situations will depend on the differences between already certified models and configurations, and the model or configuration seeking certification. A much more thorough evaluation will be needed for a new model than for a follow-on model or one that has minor modifications made to the cockpit. Regardless of the level of difference or modification, all new or modified systems or procedures, or both, should be evaluated for impact on crew complement and the pilot/system interface. For airplanes with an established crew complement, the purpose of this testing will be to corroborate by demonstration the predicted crew workload submitted by the applicant in order to substantiate compliance with § 23.1523. Testing is also to provide an independent and comprehensive assessment of individual crewmember workload in a realistic operating environment. [PS-ACE100-2001-004, Appendix A]

·        The testing should be conducted using scenarios representative of the type of operations for which the airplane will be used. Testing should include various types of routes, navigational aids, environmental conditions and traffic densities. Particular attention should be given to tasks that involve planning and execution of emergency and non-normal procedures. When appropriate, dispatch under the Master Minimum Equipment List (MMEL) should also be considered in combination with other failures that are likely to result in significantly increased pilot/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. [PS-ACE100-2001-004, Appendix A]

·        Each pilot compartment and its equipment must allow the minimum flight crew (established under § 25.1523) to perform their duties without unreasonable concentration or fatigue. [14 CFR 25.771(a)] 

        See also: 14 CFR 23.771(a), 27.771(a), and 29.771(a) which are worded slightly differently.

·        The human factors certification plans should identify the aspects of the flightcrew interface that might require significant or sustained mental or physical effort that may lead to fatigue. There are many factors that can affect fatigue, such as noise, vibration, seat comfort, poorly designed controls or displays and excessive control forces. Methods of compliance should focus on evaluation procedures that examine potential concentration demands and sources of fatigue for the flightcrew. [PS-ACE100-2001-004, Appendix A]

See also: PS-ANM100-01-03(A), Appendix A, 1 which is worded slightly differently.

·        Applicants should show the integrated design does not adversely impact workload, errors, or safe flightcrew performance per § 25.1302 given the context of the entire flight regime. Examples of such impacts would be increased time to: [AC 25.1302-1, 5-8.e(2)]

        (a)   interpret a function,

        (b)   make a decision, or

        (c)   take appropriate actions.

See also: AMC 25.1302, 5.7.5 which is worded slightly differently.

·        The applicant should show that the proposed function will not inappropriately draw attention away from other flight deck information and tasks in a way that degrades flight crew performance and decreases the overall level of safety [AMC 25.1302, 5.7.5*]

·        Because each new system integrated into the flightdeck may have a positive or negative effect on workload, each must be evaluated both in isolation and in combination with the other systems for

        compliance with § 25.1523. This is to ensure the overall workload is acceptable, i.e., that performance of flight tasks is not adversely impacted and the flightcrew’s detection and interpretation of information does not lead to unacceptable response times. Special attention should be paid to part 25 Appendix D and, specifically, compliance for items that the appendix lists as (b), workload factors. These include “accessibility, ease, and simplicity of operation of all necessary flight, power, and equipment controls.” [AC 25.1302-1, 5-8.e(3)]

See also: AMC 25.1302, 5.7.5 which is worded slightly differently.

·        Two examples of integrated design features that may or may not impact error and workload are as follows: [AC 25.1302-1, 5-8.e(3)]

        (a)   Presenting the same information in two different formats. Presenting altitude information concurrently in tape and round-dial formats, for example, may increase workload. Yet different formats may be suitable depending on the design and the flightcrew task. An analog display of engine revolutions-per-minute can facilitate a quick scan, whereas a digital numeric display can facilitate precise inputs. The applicant is responsible for demonstrating compliance with § 25.1523 and showing that differences in the formats of information presented do not result in unacceptable workload levels.

        (b)   Presenting conflicting information. Systems may exhibit minor differences between each flight crewmember station, but all such differences should be evaluated specifically to ensure that the potential for interpretation error is minimized, or that a method exists for the flightcrew to detect incorrect information, or that the effects of these errors can be precluded such as a baro-altimeter that is set wrong.

See also: AMC 25.1302, 5.7.5 which is worded slightly differently.

·        The following criteria are considered by the Agency in determining the minimum flight crew under § 25.1523: [14 CFR 25.1523, Appendix D]

        (a)   Basic workload functions. The following basic workload functions are considered:

                (1)   Flight path control.

                (2)   Collision avoidance.

                (3)   Navigation.

                (4)   Communications.

                (5)   Operation and monitoring of aircraft engines and systems.

                (6)   Command decisions.

        (b)   Workload factors. The following workload factors are considered significant when analyzing and demonstrating workload for minimum flight crew determination:

                (1)   The accessibility, ease, and simplicity of operation of all necessary flight, power, and equipment controls, including emergency fuel shutoff valves, electrical controls, electronic controls, pressurization system controls, and engine controls.

                (2)   The accessibility and conspicuity of all necessary instruments and failure warning devices such as fire warning, electrical system malfunction, and other failure or caution indicators. The extent to which such instruments or devices direct the proper corrective action is also considered.

                (3)   The number, urgency, and complexity of operating procedures with particular consideration given to the specific fuel management schedule imposed by center of gravity, structural or other considerations of an airworthiness nature, and to the ability of each engine to operate at all times from a single tank or source which is automatically replenished if fuel is also stored in other tanks.

                (4)   The degree and duration of concentrated mental and physical effort involved in normal operation and in diagnosing and coping with malfunctions and emergencies.

                (5)   The extent of required monitoring of the fuel, hydraulic, pressurization, electrical, electronic, deicing, and other systems while en route.

                (6)   The actions requiring a crewmember to be unavailable at his assigned duty station, including: observation of systems, emergency operation of any control, and emergencies in any compartment.

                (7)   The degree of automation provided in the aircraft systems to afford (after failures or malfunctions) automatic crossover or isolation of difficulties to minimize the need for flight crew action to guard against loss of hydraulic or electric power to flight controls or to other essential systems.

                (8)   The communications and navigation workload.

                (9)   The possibility of increased workload associated with any emergency that may lead to other emergencies.

                (10) Incapacitation of a flight crewmember whenever the applicable operating rule requires a minimum flight crew of at least two pilots.

        (c)   Kind of operation authorized. The determination of the kind of operation authorized requires consideration of the operating rules under which the airplane will be operated. Unless an applicant desires approval for a more limited kind of operation. It is assumed that each airplane certificated under this part will operate under IFR conditions.

·        The following is a listing of recognized workload factors considered significant when analyzing and demonstrating workload for minimum flight crew determination: [AC 23.1523, Appendix 2]

        1.     The impact of basic airplane flight characteristics on stability and ease of flight path control. Some factors such as trimmability, coupling, response to turbulence, damping characteristics, control breakout forces and control force gradients should be considered in assessing suitability of flight path control. The essential elements are the physical effort, mental effort and time required to track and analyze flight path control features, and the interaction with other workload functions.

        2.     The accessibility, ease, and simplicity of operation of all necessary flight, power, and equipment controls, including emergency fuel shutoff valves, electrical controls, electronic controls, pressurization system controls, and engine controls.

        3.     The accessibility and conspicuity of all necessary instruments and failure warning devices such as fire warning, electrical system malfunction, and other failure or caution indicators. The extent to which such instruments or devices direct the proper corrective action is also considered.

        4.     The complexity and difficulty of operation of the fuel system, with particular consideration given to the required fuel management schedule necessitated by e.g. structural, or other airworthiness considerations. Additionally, the ability of each engine to operate continuously from a single tank or source that is automatically replenished from other tanks if the total fuel supply is stored in more than one tank.

        5.     The degree and duration of concentrated mental and physical effort involved in normal operation and in diagnosing and coping with malfunctions and emergencies, including accomplishment of checklist, and location and accessibility of switches and valves.

        6.     The extent of required monitoring of the fuel, hydraulic, pressurization, electrical, electronic, deicing, and other systems while en route and recording of engine readings, and so forth.

        7.     The degree of automation provided in the event of a failure or malfunction in any of the aircraft systems. Such automation should ensure continuous operation of the system by providing automatic crossover or isolation of difficulties and minimize the need for flight crew action.

        8.     The communications and navigation workload.

        9.     The possibility of increased workload associated with any emergency that may lead to other emergencies.

        10.  Passenger problems.

        11.  Incapacitation of a flight crewmember whenever the applicable operating rule requires a minimum flight crew of at least two pilots

·        To meet the general requirements of § 25.1302, the applicant must show that functions of the proposed design are allocated so that: [AC 25.1302-1, 5-6.b(1)]

        (a)   the flightcrew can be expected to complete their allocated tasks successfully in both normal and non-normal operational conditions, within the bounds of acceptable workload and without requiring undue concentration, exceptional skill or strength, or causing undue fatigue (see § 25.1523, part 25 Appendix D, and AC 25.1523** for workload evaluation). Flightcrew population demographics should be considered (for example age and gender) when determining exceptional strength;

        (b)   the flightcrew’s interaction with the system enables them to understand the situation, and enables timely detection of failures and flightcrew intervention when appropriate; and

        (c)   task sharing and distribution of tasks among flightcrew members and the system during normal and non-normal operations is considered.

        See also: AMC 25.1302, 5.5.2 which is worded slightly differently.

·        Equipment operating procedures should be designed to maximize operational suitability, minimize pilot workload, and minimize reliance on pilot memory. [TSO-C146c/RTCA DO-229D, 2.2.1.1.2]