AC 29.1517A. §29.1517 (AMENDMENT 29-59) LIMITING HEIGHT-VELOCITY ENVELOPE.
a. Explanation. Amendment 29-59 changed the title of the section from “Limiting height-speed envelope” to “Limiting height-velocity envelope” to be consistent with the title nomenclature of § 29.87, which was changed from “Limiting height-speed envelope” to “Height-velocity envelope” at amendment 29-39.
b. Procedures. The policy pertaining to the procedures in this section remain unchanged. For purposes of this AC, the terms “height-velocity” and “height-speed” are equivalent.
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AC 29.1519. § 29.1519 WEIGHT AND CENTER OF GRAVITY.
a. Explanation. This rule requires that weight and center of gravity (CG) combinations which are substantiated structurally and also found satisfactory during flight tests (per §§ 29.25 and 29.27) must be established as operating limits. A related portion in § 29.1583(c) further requires that weight and CG limitations be entered in the Rotorcraft Flight Manual Limitations Section. Both maximum and minimum weight must be established as operating limitations along with the corresponding longitudinal and lateral centers of gravity for each condition. Weight and CG limits are discussed in more detail in paragraphs AC 29.25 and AC 29.27.
b. Procedures.
(1) The results of shifts in center of gravity with fuel burn should be evaluated.
If it is possible to take off within the approved loading envelope and subsequently burn fuel to a condition which is significantly beyond the approved weight/CG envelope, then there should be appropriate instructions in the loading and/or operating procedures of the RFM to avoid this condition.
(2) Typical loading conditions should not result in weight/CG combinations outside of approved limits. A minimum of two loadings, appropriate to the rotorcraft configuration, should be evaluated. These should include critical combinations of maximum/minimum variables for fuel, passengers, and crew. If this results in loading outside approved limits, special interior placarding or cautionary information should be provided in appropriate sections of the Rotorcraft Flight Manual.
AC 29.1521. § 29.1521 (Amendment 29-34) POWERPLANT LIMITATIONS.
a. Explanation.
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(1) This rule requires that the various parameters and operating conditions listed under each type of operation be evaluated and established as operating limitations. The procedures for establishing and verifying each powerplant limitation are discussed in the powerplant section of this AC. This rule requires that powerplant limitations be established for four specific types of operation or power ratings: takeoff, continuous, 2 1/2-minute, and 30-minute. Additional limitations are required to account for engine and transmission cooling and minimum required fuel grade. The 2 1/2-minute and 30-minute limitations are optional requirements intended for use only on multiengine rotorcraft after failure of one engine. These limits are generally referred to as one-engine-inoperative (OEI) limitations.
(2) It is important to differentiate between the rotorcraft powerplant limitations and the engine limitations as established under Part 33. For some parameters, these two limits may be identical, but frequently the engines will be capable of exceeding the maximum limitations substantiated for the combined powerplant installation. Limitations established according to this rule may not exceed the engine limitations established in accordance with Part 33 but may be less than the Part 33 limits as desired by the applicant.
b. Procedures.
(1) Determine the limiting parameters for each required power rating according to the requirements of Part 29, Subpart E, Powerplant. (See applicable paragraphs of this AC for detailed procedures.)
(2) Provide the limitations established according to this rule to the rotorcraft crew through placards in accordance with § 29.1541, instrument markings in accordance with § 29.1549, and in the Rotorcraft Flight Manual Limitations Section in accordance with § 29.1583(b). (See paragraphs AC 29.1543 and AC 29.1583.)
AC 29.1521A. § 29.1521 (Amendment 29-26) POWERPLANT LIMITATIONS.
a. Explanation. Amendment 29- 26 revises §§ 29.1521(f) and (g) and adds a new § 29.1521(h). The changes to §§ 29.1521(f) and (g) introduce the term “OEI” to emphasize and clarify the limitations on the use of the 2 ½-minute and 30-minute power ratings. This change added the introductory phrase “unless otherwise authorized.” In order to authorize use of these ratings, additional qualification tests or other adequate safety measures have been instituted. Both §§ 29.1521(f) and (g) have been reworded to set forth specific limitations on the use of these ratings. These changes were made to clarify the eligibility of these ratings. The new § 29.1521(h) establishes and defines a new continuous OEI power rating using terminology similar to that developed for the 2 ½-minute and 30-minute power ratings. This change ensures proper recognition in the powerplant limitations listing required by § 29.1583.
b. Procedures. All of the policy material pertaining to this section remains in effect. Additionally, the following procedures should be considered:
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(1) Sections 29.1521(f) through (h) require limitations for OEI operation for multi-turbine engine powered rotorcraft. The same parameters required for the takeoff and continuous ratings should be established as limitations for each approved OEI rating (i.e., maximum rotational speed, time, gas temperature, and torque).
Section 29.923 includes requirements for qualification of the rotor drive system for 2 ½-minute, 30-minute, and continuous OEI powers. Section 29.1501(a) requires that information necessary for safe operation should be established as limitations. Thus the establishment of OEI powerplant limitations is required even though not specifically addressed in § 29.1521.
(2) It is important to differentiate between the rotorcraft powerplant limitations and the engine limitations as established under Part 33. For some parameters, these two limits may be identical, but frequently, the engines will be capable of exceeding the maximum limitations substantiated for the combined powerplant installation. Limitations established according to this rule may not exceed the engine limitations established in accordance with Part 33 but may be less than the Part 33 limits as desired by the applicant.
AC 29.1521B. § 29.1521 (Amendment 29-34) POWERPLANT LIMITATIONS.
a. Explanation . Amendment 29-34 adds §§ 29.1521(i) and (j). The new §§ 29.1521(i) and (j) introduce the 30-second and 2-minute OEI power rating limitations, respectively. These paragraphs define the limitations on the use of the 30- second and 2-minute power ratings using terminology similar to that developed for the 2 ½-minute and 30-minute power ratings. Additionally, these paragraphs require the ability to detect any damage which occurs due to the use of either 30-second or 2-minute OEI limits and requires that the procedures to inspect for such damage be provided in the instructions for continued airworthiness for either the engine and/or the airframe.
b. Procedures. All of the policy material pertaining to this section remains in effect. Additionally, the following procedures should be considered:
Sections 29.1521(i) and (j) require limitations for 30-second/2-minute OEI operation for multi-turbine engine powered rotorcraft. The same parameters required for the takeoff and continuous ratings should be established as limitations for each approved OEI rating (i.e., maximum rotational speed, time, gas temperature, and torque). These new ratings can only be approved as a rating in conjunction with the other. That is, a rotorcraft with a 30-second OEI rating must also have a 2-minute OEI rating and viceversa. The 30- second and 2-minute OEI ratings are also limited to use for continued operation of the remaining engine(s) upon failure or precautionary shutdown of an engine. Upon the use of 30- second or 2-minute OEI, an inspection for damage to the airframe and/or engine should be conducted. The inspection should be accomplished per the procedures furnished by the airframe and engine manufacturers, and any damage occurring due to the use of these new ratings should be detected using these inspection procedures. Section 29.923 includes requirements for qualification of the Page G - 11
rotor drive system for 30-second and 2-minute OEI powers. Section 29.1501(a) requires that information necessary for safe operation should be established as limitations. The limitation information provided in this paragraph should be provided in the flight manual. This includes the requirement for an inspection prior to further flight after the use of either 30-second or 2-minute OEI.
AC 29.1522. § 29.1522 (Amendment 29-17) AUXILIARY POWER UNIT LIMITATIONS.
a. Explanation.
(1) Any APU installed in a rotorcraft will have operating limitations which have been developed by design and testing. These APU operating limitations become part of the operating limitations for the rotorcraft.
(2) TSO-C77 establishes the minimum performance standards and limitations which gas turbine APU’s should meet in order to be identified with the TSO marking.
b. Procedure.
(1) Limitations for APU’s which meet the requirements of TSO-C77 will be contained in the APU model specification and in one or more manuals containing instructions for the installation, operation, servicing, maintenance, repair and overhaul of the APU. Data from these documents which are required by the TSO, should be included in the rotorcraft flight manual (RFM) and in maintenance manuals, as appropriate.
(2) APU’s which do not meet the requirements of TSO-C77 should have the design and operating limitations defined and included in the operating limitations section of appropriate rotorcraft manuals. TSO -C77 can be used as a guide to identify and develop the detailed data which will be included in the rotorcraft flight and maintenance manuals.
AC 29.1523. § 29.1523 MINIMUM FLIGHTCREW.
a. Explanation.
(1) This rule requires that the minimum crew necessary to show compliance with the requirements of Part 29 or for safe operation of the rotorcraft be established as an operating limitation.
(2) The determination of minimum crew requirements is typically based on a subjective pilot assessment of the crew requirements for safe operation of each rotorcraft design. Certain regulations, such as the requirements for instrument flight rules (IFR), have specific quantitative differences between single-pilot and two-pilot requirements. However, most often the minimum crew requirement will be based on Page G - 12
more subjective considerations such as location of necessary controls, pilot workload to accomplish required tasks, type of operation, and overall complexity of the rotorcraft design.
(3) Minimum crew requirements for the same type design may vary with the kind of operation. Many rotorcraft have been approved for a single- pilot crew for visual flight rules (VFR) operations but require a two-pilot crew for IFR operations. Other kinds of operations that may require more than one crewmember to meet type certification requirements are night operations, operations into known icing conditions, operations in falling and blowing snow, extended overwater operations, and external load operations.
(4) It is important to distinguish between the minimum crew requirements for compliance with Part 29 type certification regulations and the minimum crew requirements of the various operating regulations (Parts 61, 91, 121, 133, 135, and
137). A rotorcraft may be type certified for a minimum crew of one and still be required to have a crew of two or more by the operating regulations for certain types of operation or by the workload associated with an operating environment. Therefore, an applicant should carefully consider the possible operational uses of any rotorcraft design and become familiar with the applicable operating regulations as well as the type certification requirements early in the design process.
(5) Although the rotorcraft configuration is typically certified with the pilot-in-command station in the right seat, the left seat may be used for the pilot-in-command if, in addition to the flight controls required to control the rotorcraft, the following are included for the pilot: throttle control including ability to shut down all engines, airspeed indication, altitude indication, rotor and engine RPM, and engine torque and exhaust gas temperature. The authority should evaluate a change to the pilot-in-command station.
(6) The applicant is encouraged to contact the responsible type certification office as early in the design phase as possible to initiate the qualitative assessment process. Cockpit layout drawings, instrument panel mockups, and full -scale cockpit mockups can be used to determine if required controls are accessible and to begin the pilot workload assessment for certain operations.
b. Procedures .
(1) General.
(i) A systematic evaluation and test plan is required for any new or modified rotorcraft. The methods for showing compliance should emphasize the use of acceptable analytical, simulation, and flight test techniques. The crew complement should be studied through a logical process of estimating, measuring, and then demonstrating the workload imposed by a particular cockpit design. When the minimum crew requirements have been determined, they should be included in the limitations section of the Rotorcraft Flight Manual in accordance with § 29.1583(d).
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(ii) Appropriate analysis should be conducted by the applicant early in the design process. The specific method(s) of analysis should be selected on the basis of its predictive validity, sensitivity, reliability, applicability to the particular cockpit configuration, and availability of a suitable reference for comparison.
(2) Analytical Approach.
(i) One analytical approach defines workload as a percentage of the time available to perform tasks (Time Line Analysis). This process may be applied to an appropriate set of flight segments in which operationally important time constraints can be identified. This method is useful for evaluation of cockpit changes relating to overt pilot work such as control movements and data inputs. The generally accepted practice involves careful selection of the limited set of flight scenarios and time segments that represent the range of operational requirements (including the range of normal and non normal procedures.) Time line analysis yields useful data when tasks must be performed within operationally significant time constraints. The adequacy of this method is very much dependent on an accurate determination of the time available.
Absolute standards are not available for interpretation of obtained time required scores, but such records can be used to identify high or simultaneous workload demands for later testing in a simulator or aircraft, and comparisons can be made with overt workload demands in proven aircraft. However, the impact of cockpit changes on planning and decisionmaking is difficult to quantify by this method.
(ii) The most frequently used basis for deciding that a new design is acceptable is a comparison of a new design with previous designs proven in operational service. By making specific evaluations using the acceptable human factors techniques, and comparing new designs to a known baseline, it is possible to proceed with confidence that the changes incorporated in the new designs accomplish the intended result. When the new cockpit is considered, certain components may be proposed as replacements for conventional items, and some degree of rearrangement may be contemplated. New avionics systems may need to be fitted into existing panels, and newly automated systems may replace current indicators and controls. As a result of this evolutionary characteristic of the cockpit design process, there is frequently a reference cockpit design, which is usually a conventional aircraft that has been through the test of operational usage. If the new design represents an evolution, improvement attempt, or other deviation from this reference cockpit, the potential exists to make direct comparisons. Service experience should be researched to assure that any existing problems are understood and not perpetuated.
(iii) If preliminary analysis by the certification team identify potential problem areas, these areas should receive more extensive evaluation and data collection in order to verify compliance with § 29.1523. These concerns should be adequately addressed in the manufacturer’s demonstration plan when submitted to the FAA/AUTHORITY.
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(iv) If the new design represents a significant change in level of automation or pilot duties, analytic comparison to a reference design may have lessened value. Without a firm data base on the time required to accomplish both normally required and contingency duties, more complete and realistic simulation and flight testing will be required.
(3) Testing.
(i) In the case of the minimum crew determination, the final decision is reserved until the rotorcraft has been flown by experienced flight test pilots trained and current in the aircraft. More assurance is derived from actual flight tests than from earlier simulator tests or other synthetic or computer model procedures.
(ii) The test program should address the workload functions and factors listed below. For example, an evaluation of communications workload should include the basic workload required to properly operate the aircraft in the environment for which approval is sought. The goal is to evaluate workload with the proposed crew complement during realistic operating conditions, including representative air traffic and weather.
(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, and engine controls.
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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, 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 any 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.
AC 29.1525. § 29.1525 (Amendment 29-24) KINDS OF OPERATION.
This rule states that the kinds of operation to which the rotorcraft is limited are established by demonstrated compliance with applicable certification requirements (primarily flight) and the equipment requirements established for that kind of operation.
The basic flight characteristics requirements of Part 29 are suitable for day VFR approval. Additional night considerations appear in § 29.141(c) and in the operating rules. IFR requirements are addressed in § 29.141(c) and Appendix B to Part 29.
Additional IFR equipment requirements are contained in the operating rules. Icing certification criteria are contained in paragraph AC 29.877. External load requirements for certification may be found in §§ 29.25(c) and 29.865(c) in addition to Part 133.
Related § 29.1525(d) further requires that the approved kinds of operation must be listed in the operating limitations section of the Rotorcraft Flight Manual. The Page G - 16
equipment that is necessary for a specific kind of operation other than basic day VFR operation should also be listed in the limitations section of the RFM.
AC 29.1527. § 29.1527 (Amendment 29-15) MAXIMUM OPERATING ALTITUDE.
a. Explanation. This rule requires that the maximum altitude for operation of the rotorcraft must be established as an operating limitation. The rule is intended to establish en route altitude as an operating limit. The requirements for maximum takeoff and landing altitude are contained in other portions of the rule. (See discussion in paragraph AC 29.45.b(3).) T he en route limit may be established by any of the preceding subparts of the rule involving flight, structural, powerplant, equipment or related functional requirements of those subparts. Maximum operating altitude is ordinarily specified initially by the manufacturer and substantiated throughout the type certification program by each engineering discipline. Maximum operating altitude must be established in terms of pressure altitude unless the pilot is provided with some equally functional means of observing specified altitude limits (e.g., a density altitude indicator if maximum altitude is specified in terms of density altitude). A related requirement in § 29.1583 specifies that maximum operating altitude must be established as an operating limitation in the Rotorcraft Flight Manual and further that any limiting factors must be identified and explained.
b. Procedures. Each FAA/AUTHORITY engineering discipline must assure that data and testing are adequate to properly substantiate and qualify all critical components to the maximum operating altitude of the rotorcraft. The design or maximum substantiated altitude should be specified in the Type Inspection Authorization. The flight test program mu st include at least one test flight to the maximum approved altitude and this flight must include functional testing of all critical aircraft components. Due to specific requi rements in § 29.21(b), no extrapolation of these results is allowed.
AC 29.1529. § 29.1529 (Amendment 29-20) INSTRUCTIONS FOR CONTINUED AIRWORTHINESS (MAINTENANCE MANUAL).
a. Airworthiness Limitations Section
(1) Explanation. The FAA/AUTHORIT Y has long recognized the necessity to have a maintenance manual for rotorcraft due to the unique and generally complicated and critical design features.
(i) Airworthiness Limitations Section.
(A) Amendment 29-4, October 1968, established the requirement for a separate and specific airworthiness limitations section. Section 43.15 was already in place. New § 43.16 was added to the maintenance rules, and § 91.163(c) was added to the operating rules to require compliance with this section of the maintenance manual.
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AC 29-2C, Chg 1 2/12/03 (B) Amendment 29-20, October 1980, revised the rule and added Appendix A containing requirements for preparation of instructions for continued airworthiness, including the airworthiness limitations section. Instructions for continued airworthiness replaced “rotorcraft maintenance manual” in the standard. The maintenance rules, §§ 43.15 and 43.16, and § 91.163(c) of the operating rules also refer to, or require, compliance with certain parts of the instructions for continued airworthiness. The airworthiness limitations were intended to define the limits of the type certification approval of the fatigue characteristics of “critical flight structure.”
(ii) Rotorcraft type designs are unique in comparison to airplane designs in that transmissions and rotors and some elements of flight control systems have critical components that may be adversely affected by operating conditions and time in service. The FAA/AUTHORITY-approved airworthiness limitations section may include such items as gear sets, bearings, etc., of the rotorcraft type design if a finite life was established during the type certification program and/or if the FAA/AUTHORITY determined that mandatory inspections and/or replacement of the component (part) was necessary to maintain airworthiness of the rotorcraft. For example, a drive spline, gear, or bearing was serviceable after concluding the ground endurance test and/or FAA/AUTHORITY flight test program. However, an FAA/AUTHORITY-mandated inspection or replacement of the component was considered essential for airworthiness of the rotorcraft type design and necessary for type certification. Time between overhaul (TBO) of components is not part of the airworthiness limitations. If an inspection or replacement of a part in an assembly is required, the inspection interval or replacement time and the part number should be included in the limitations. The inspection interval or replacement time may or may not coincide with the recommended overhaul interval of the assembly. (See t he comments for Proposal 8-25, § XX.4 in the preamble of Amendment 29-20 (45 FR 60154, September 11, 1980). Note that parts considered unserviceable at the conclusion of the ground endurance test of § 29.923 are not acceptable for type certification.
(iii) Certain components must be identified by part number (or equivalent) and serial number (or equivalent). Sect ion 29.1529(a)(1) and (2) of Amendment 29-4 and § 45.14 of Amendment 45-12 list the requirements. The part number of parts and/or components requiring inspections and/or replacement as a result of § 29.571 or other standards must be listed in the airworthiness limitations section of the manual or another separate, segregated section of the manual appropriate to the rules.
(2) Procedures.
(i) General.
(A) The rule of Amendment 29-4 and its predecessor stated that the maintenance manual must contain all information that the applicant considers essential for proper maintenance. Amendment 29- 4 also added the requirement for an airworthiness limitations section. Amendment 29-20 revised § 29.1529 and added Page G - 18
Appendix A that now contains the requirements for content and preparation of the manual. The airworthiness limitations section of the manual, and any revisions thereto, must be FAA/AUTHORITY approved. The “continued airworthiness” sections, which contain the manufacturer’s recommendations for continued airworthiness are not FAA/AUTHORITY approved.
(B) The airworthiness limitations section contains information derived primarily but not solely from the data approved under § 29.571. In addition to replacement times and inspections, where appropriate, some of the basic usage assumptions made in the fatigue evaluation, which the operator can reliably assess (such as numbers of ground-air-ground cycles) should be identified. These should be noted in the airworthiness limitations so that the operator may take appropriate action (see MG 8 and MG 11). Approval of this section of the manual must be completed before type certification. See Part 29, Appendix A, paragraph A29.4 of Amendment 29-20. (For further information, see the comments for Proposal 8-25, § XX.4 in the preamble of Amendment 29-20 (45 FR 60154, September 11, 1980)).
(C) Part 29, Appendix A, paragraphs A29.3(a) and (b) pertain to the content of the instructions for continued airworthiness. For example, scheduling, overhauls (including recommended overhaul periods or TBO), inspections, and servicing information are included in this section of the manual.
(ii) Identifying and Serializing Fatigue Critical Components.
(A) Part numbers and serial numbers must be applied to fatigue life limited components as noted in §§ 45.14 and 29.1529(a)(1) and (2) of Amendment 29-4. Electric arc marking m ethods should not be used due to possible internal arcing, pitting of surfaces, and changes in physical or chemical characteristics due to the local high temperature at the arcs.
(B) Vibrating pencils, nameplates, or permanent inks may be used.
However, serial numbers should be applied on each part such that material is upset or displaced on the part, thereby attaining a more permanent number. When material is upset or displaced, the component's integrity and fatigue tolerance must not be compromised, for example, the least critical or lowest stressed area should be used.
(C) For small parts, the rule (§ 45.14) allows markings that are equivalent to part and serial numbers. Markings or symbols may be used to enable the identification of a part as one for which a replacement time, inspection interval, or related procedure is specified in the airworthiness limitations section. The FAA/AUTHORITY-stated identification of such small parts is clearly essential for safety and may not be relieved. With adoption of Amendment 29-20, the marking requirements that were contained in § 29.1529 are now contained in § 45.14, Amendment 45-12.
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