AC 21.17-4 Appendix A
(c) A correlation must be established between the flight recorder readings of airspeed, altitude, and heading and the corresponding readings (taking into account correction factors) of the first pilot's instruments. The correlation must cover the airspeed range over which the aircraft is to be operated, the range of altitude to which the aircraft is limited, and 360 degrees of heading.
Correlation may be established on the ground as appropriate.
(d) Each recorder container must—
(1) Be either bright orange or bright yellow;
(2) Have reflective tape affixed to its external surface to facilitate its location under water; and
(3) Have an underwater locating device, when required by the operating rules of this chapter, on or adjacent to the container, which is secured in such a manner that they are not likely to be separated during crash impact.
(e) Any novel or unique design or operational characteristics of the aircraft shall be evaluated to determine if any dedicated parameters must be recorded on flight recorders in addition to or in place of existing requirements.
PL.1529 Instructions for continued airworthiness.
The applicant must prepare Instructions for Continued Airworthiness (ICA), in accordance with subparts K, L, and M, that are acceptable to the Administrator. ICA for the aircraft, engines, and propellers may be shown in a single aircraft ICA manual if the engine and propeller approvals are sought through the aircraft certification program. Alternatively, the applicant may provide individual ICA for the aircraft, engines, and propellers. The instructions may be incomplete at the time of type certification if a program exists to ensure their completion prior to delivery of the first aircraft, or issuance of a standard certificate of airworthiness, whichever occurs later.
S UBPART A—GENERAL PL.2000 Applicability and definitions.
(a) These airworthiness criteria prescribe airworthiness standards for the issuance of a type certificate, and changes to that type certificate, for powered-lift with maximum weights of 12,500 pounds or less and a maximum passenger seating configuration of six or less. The aircraft must be certificated in accordance with either the “essential performance” or “increased performance” requirements of these airworthiness criteria. The aircraft may also be type certificated as both “essential performance” and “increased performance” with appropriate and different operating limitations for each approval.
(b) For purposes of these airworthiness criteria, the following definitions apply:
(1) Essential performance means, in the event of a critical change of thrust, the aircraft has no guaranteed climb capability but is capable of controlled flight and an unscheduled landing is assumed.
(2) Increased performance means, in the event of a critical change of thrust, the aircraft is capable of climbing to a safe altitude, on a flightpath clear of obstacles, and maintaining level flight to a planned destination, a diversion location, or the point of departure.
(3) Phases of flight means ground operations, takeoff, climb, cruise, descent, approach, hover, and landing.
A-4
AC 21 .17-4 Appendix A
(4) Source of lift means one of three sources of lift: thrust‐borne, wing‐borne, and semi-thrust‐ borne. Thrust‐borne is defined as when the aircraft depends principally on engine-driven lift devices or engine thrust for lift. Wing‐borne is defined as when the aircraft depends principally on the lift from nonrotating airfoil surfaces. Semi‐thrust‐borne is the combination of thrust‐borne and wing‐borne, where both forms of lift are used to support the aircraft.
(5) Critical change of thrust means the most adverse effect on performance or handling qualities resulting from a failure or combination of failures of the propulsive system or flight control system, when applicable, either singular or in combination, not shown to be extremely improbable.
(6) Local events are failures of aircraft systems and components, other than the engine and propeller control system, that may affect the installed environment of the engine and propeller control system.
(7) Approved flight envelope refers to the range of conditions within which the FAA has deemed it safe to operate an aircraft. These conditions include, but are not limited to, combinations of weight and center of gravity, flight profiles, ambient conditions, and likely failures.
(8) Engine-driven lift device is a propeller that generates any combination of lift and principal forward thrust in semi-thrust-borne flight or lift only in thrust-borne flight.
PL.2010 Accepted means of compliance.
(a) An applicant must comply with these airworthiness criteria using a means of compliance, which may include consensus standards, accepted by the Administrator.
(b) An applicant requesting acceptance of a means of compliance must provide the means of compliance to the FAA in a form and manner acceptable to the Administrator.
SUBPART B—FLIGHT Performance PL.2100 Weight and center of gravity.
(a) The applicant must determine limits for weights and centers of gravity that provide for the safe operation of the aircraft.
(b) The applicant must comply with each requirement of this subpart at critical combinations of weight and center of gravity within the aircraft's range of loading conditions using tolerances acceptable to the Administrator.
(c) The condition of the aircraft at the time of determining its empty weight and center of gravity must be well defined and easily repeatable.
PL.2105 Performance data.
(a) Unless otherwise prescribed, the aircraft must meet the performance requirements of this subpart in—
(1) Still air and standard atmospheric conditions at sea level for aircraft approved for essential performance; and
(2) Ambient atmospheric conditions within the approved flight envelope for aircraft approved for increased performance.
A-5
AC 21 .17-4 Appendix A
(b) Unless otherwise prescribed, the applicant must develop the performance data required by this subpart for the conditions within the approved flight envelope.
(c) The procedures used for determining takeoff and landing performance must consider all the applicable configurations and be executable consistently by pilots of average skill in the atmospheric conditions expected to be encountered in service.
(d) Performance data determined in accordance with this section must account for losses due to atmospheric conditions, cooling needs, installation, downwash considerations, and other demands on power sources.
(e) The hovering ceiling, in and out of ground effect, if applicable, must be determined within the approved flight envelope.
(f) Following a condition when the aircraft can no longer provide the commanded power or thrust required for continued safe flight and landing, the aircraft must be capable of a controlled emergency landing by gliding, autorotation, or an equivalent means to mitigate the risk of loss of power or thrust. The aircraft design must allow for the pilot to choose the direction and area of touchdown while reasonably protecting the occupants from injury. Upon landing, some damage to the aircraft may be acceptable.
PL.2110 Flight profiles The applicant must determine the flight profiles for which certification is being sought. Flight profiles refer to the grouping of flight phases, associated maneuvers, procedures, safe speeds inclusive of minimum speeds which may be stall speeds, operational conditions, and other critical flight references for the most adverse conditions consistent with the approved flight envelope.
PL.2115 Takeoff performance.
(a) The applicant must determine takeoff performance for all configurations for which approval is sought accounting for:
(1) The approved flight envelope, and
(2) Climb requirements.
(b) For aircraft approved for essential performance, the applicant must determine the takeoff performance to 50 feet above the takeoff surface such that a rejected takeoff resulting in safe stop or landing can be made at any point along the takeoff flight path following a critical change of thrust.
(c) For aircraft approved for increased performance, the applicant must determine the takeoff performance so that—
(1) Following a critical change of thrust prior to reaching the takeoff decision point, a rejected takeoff resulting in a safe stop or landing can be made. The takeoff decision point may be a speed, an altitude, or other critical flight parameters selected by the applicant; and
(2) Following a critical change of thrust after passing the takeoff decision point, the aircraft can—
(i) Continue the takeoff and climb to 50 feet above the takeoff surface; and A-6
AC 21 .17-4 Appendix A
(ii) Subsequently achieve the configuration and airspeed used in compliance with PL.2120.
PL.2120 Climb requirements.
(a) The applicant must demonstrate minimum climb performance out of ground effect at each weight, altitude, and ambient temperature within the operating limitations using the procedures published in t he flight manual.
(b) The applicant must determine the following all engines operating (AEO) climb performance requirements:
(1) A steady climb gradient of—
(i) at least 8.3 percent at the configuration and speed at the end of the takeoff, for aircraft approved for essential performance; or
(ii) at least 4.5 percent at the configuration and speed at the end of the takeoff, for aircraft approved for increased performance.
(2) For a balked landing, a climb gradient of 3 percent without creating undue pilot workload with the landing gear extended and in the landing configuration(s) selected by the applicant.
(c) For aircraft approved for essential performance, the climb performance after a critical change of thrust must be determined–
(1) Using applicable sources of lift along the takeoff flight path for which certification is being sought at the speeds and configurations selected by the applicant; and
(2) If level flight cannot be maintained during the transition from the takeoff to the enroute configuration, the total altitude loss must be determined for all combinations of weight, altitude, and ambient temperature.
(d) For aircraft approved for increased performance, the climb performance after a critical change of thrust must be such that:
(1) During the takeoff climb the aircraft has—
(i) At least a positive climb gradient with the aircraft at the configuration and speed determined at the end of the takeoff in PL.2115(c);
(ii) At a minimum of 200 feet above the takeoff surface, per the approved takeoff path for which certification is requested, a climb gradient of at least 2.5 percent with the aircraft at the configuration and speed selected by the applicant; and
(iii) At 1,000 feet above the takeoff surface, a climb gradient of at least 1.7 percent with the aircraft in the final takeoff speed and configuration selected by the applicant.
(2) From the initial height at the end of the takeoff in PL.2115(c), the aircraft path must be level or positive until the aircraft obtains the speed and climb performance defined in paragraph
(d)(1)(i) through (iii) of this section along the takeoff climb path.
(3) Enroute, the steady rate of climb (or descent) must be determined at each weight, altitude, and temperature for which certification is requested.
(4) During a discontinued approach at 200 feet above the landing surface, the climb gradient is not less than 2.5 percent at the configuration and speed selected by the applicant for the landing profile for which certification is requested.
A-7
AC 21 .17-4 Appendix A PL.2125 Climb information.
(a) The applicant must determine climb performance at each weight, altitude, and ambient temperature within the operating limitations using the procedures published in the flight manual.
(b) The applicant must determine climb performance accounting for any critical change of thrust.
(c) The applicant must determine the performance accordingly for the appropriate sources of lift applicable to the conditions defined in PL.2105(f).
PL.2130 Landing.
The applicant must determine the following, for critical combinations of weight, altitude, and temperatures within the operational limits:
(a) The approach and landing speeds and procedures, which allow a pilot of average skill to land within the published landing distance consistently and without causing damage or injury, and which allow for a safe transition to the balked landing conditions of these airworthiness criteria accounting for:
(1) All sources of lift for each approach and landing flight path for which certification is sought,
(2) Any minimum or maximum speed safety margins, and
(3) Minimum control speeds.
(b) For aircraft approved for essential performance, the applicant must determine the landing performance from a height of 50 feet above the landing surface. Additionally, the aircraft must be capable of performing a safe landing at any point along the approach flight path following a critical change of thrust.
(c) For aircraft approved for increased performance, the applicant must determine the landing performance from a height of 50 feet above the landing surface so that, following a critical change of thrust that occurs—
(1) Prior to the landing decision point, which may be a speed, an altitude, or other critical flight parameters selected by the applicant, the aircraft can:
(i) Land and stop safely on the landing surface; or
(ii) Transition to the balked landing condition and performance established in PL.2120.
(2) After passing the landing decision point, the aircraft can land and stop safely on the landing surface.
Flight Characteristics PL.2135 Controllability and maneuverability.
(a) The aircraft must be controllable and maneuverable, without requiring exceptional piloting skill, alertness, or strength, within the approved flight envelope—
(1) At all loading conditions for which certification is requested;
(2) During all phases of flight;
(3) In degraded flight control system operating modes and likely flight control or propulsion system failures;
A-8
AC 21.17-4 Appendix A
(4) During configuration changes;
(5) In thrust-borne operations with wind velocities from zero to at least 17 knots from any azimuth angle; and
(6) The aircraft must be able to safely complete a landing using the steepest approach gradient procedures.
(b) The applicant must determine critical control parameters, such as limited control power margins, and if applicable, account for those parameters in appropriate operating limitations.
(c) It must be possible to make a smooth transition from one flight condition to another (inclusive of changes in configuration, source of lift, phase of flight, or response type) without exceeding the approved flight envelope.
PL.2140 Trim.
(a) The aircraft must maintain lateral and directional trim without further force upon, or movement of, the primary flight controls or corresponding trim controls by the pilot, or the flight control system, under all normal operations while using applicable sources of lift.
(b) The aircraft must maintain longitudinal trim without further force upon, or movement of, the primary flight controls or corresponding trim controls by the pilot, or the flight control system, under the following conditions:
(1) Climb.
(2) Level flight.
(3) Descent.
(4) Approach.
(c) Residual control forces must not fatigue or distract the pilot during normal operations of the aircraft and likely abnormal or emergency operations. The trim system must not contain objectionable force characteristics.
PL.2145 Stability and handling qualities.
(a) Within the approved flight envelope, acceptable aircraft stability must be demonstrated in handling qualities sufficient to safely perform any task required for the intended aircraft operation without requiring exceptional pilot skill, strength, or alertness—
(1) In all conditions expected to be seen in service, and
(2) In likely failure conditions.
(b) The aircraft must not exhibit any divergent stability characteristics in any axis.
(c) Handling qualities must be based primarily on positive control movement or forces by assessing task execution, pilot workload, acceptable cues, and pilot compensation during appropriate maneuvers and operations.
PL.2150 Minimum safe flight characteristics and warning.
For each flight profile established under PL.2110, the aircraft must:
A-9
AC 21 .17-4 Appendix A
(a) Exhibit controllable flight characteristics, including but not limited to stalls in straight flight, turning flight, and accelerated turning flight.
(b) Not have the tendency to inadvertently depart controlled safe flight after a sudden change of thrust.
(c) Have a clear and distinctive warning that provides sufficient margin to prevent inadvertent departure from controlled flight.
PL.2155 Ground and water handling characteristics.
For aircraft intended for operation on land or water, the aircraft must have controllable longitudinal and directional handling characteristics during taxi, takeoff, and landing operations.
PL.2160 Vibration, buffeting, and high-speed characteristics.
(a) Each part of the aircraft must be free from excessive vibration and buffeting under each appropriate speed and power condition. Vibration and buffeting, for operations up to VD/MD, must not interfere with the control of the aircraft or cause excessive fatigue to the flightcrew.
Stall warning buffet within these limits is allowable.
(b) For inadvertent excursions beyond the maximum approved speed, the aircraft must be able to safely recover back to its approved flight envelope without requiring exceptional piloting skill, strength, or alertness. This recovery may not result in structural damage or loss of control.
PL.2165 Performance and flight characteristics requirements for flight in atmospheric icing conditions.
(a) An applicant who requests certification for flight in atmospheric icing conditions must show the following in the icing conditions for which certification is requested:
(1) Compliance with each requirement of this subpart, except those applicable to spins and any that must be demonstrated at speeds in excess of—
(i) 250 knots calibrated airspeed (CAS);
(ii) VMO/MMO or VNE; or
(iii) A speed at which the applicant demonstrates the airframe will be free of ice accretion.
(b) The applicant must provide a means to detect icing conditions for which certification is not requested and show the aircraft’s ability to avoid or exit those icing conditions.
(c) The applicant must develop an operating limitation to prohibit intentional flight, including takeoff and landing, into icing conditions for which the aircraft is not certified to operate.
SUBPART C—STRUCTURES PL.2200 Structural design envelope.
The applicant must determine the structural design envelope, which describes the range and limits of aircraft design and operational parameters for which the applicant will show compliance with the requirements of this subpart. The applicant must account for all aircraft design and operational parameters that affect structural loads, strength, durability, and aeroelasticity, including:
A-10
AC 21 .17-4 Appendix A
(a) Structural design airspeeds, landing descent speeds, and any other airspeed limitation at which the applicant must show compliance to the requirements of this subpart. The structural design airspeeds must—
(1) Be sufficiently greater than the stalling speed of the aircraft to safeguard against loss of control in turbulent air, while in wing-borne flight;
(2) Be sufficiently greater than the minimum speed of the aircraft while in thrust-borne and semithrust-borne flight to safeguard against loss of control in turbulent air; and
(3) Provide sufficient margin for the establishment of practical operational limiting airspeeds.
(b) Design maneuvering load factors not less than those, which service history shows, may occur within the structural design envelope.
(c) Inertial properties including weight, center of gravity, and mass moments of inertia, accounting for—
(1) Each critical weight from the aircraft empty weight to the maximum weight; and
(2) The weight and distribution of occupants, payload, and energy-storage systems.
(d) Characteristics of aircraft control systems, including range of motion and tolerances for control surfaces, high lift devices, or other moveable surfaces.
(e) Each critical altitude up to the maximum altitude.
(f) Engine-driven lift device rotational speed and ranges, and the maximum rearward and sideward flight speeds.
(g) Thrust‐borne, wing‐borne, and semi‐thrust‐borne flight configurations, with associated flight load envelopes.
PL.2205 Interaction of systems and structures.
For aircraft equipped with systems that modify structural performance, alleviate the impact of this subpart's requirements, or provide a means of compliance with this subpart, the applicant must account for the influence and failure of these systems when showing compliance with the requirements of this subpart.
Structural Loads PL.2210 Structural design loads.
(a) The applicant must:
(1) Determine the applicable structural design loads resulting from likely externally or internally applied pressures, forces, or moments that may occur in flight, ground and water operations, ground and water handling, and while the aircraft is parked or moored.
(2) Determine the loads required by paragraph (a)(1) of this section at all critical combinations of parameters, on and within the boundaries of the structural design envelope.
(3) Determine the loads required for durability.
(b) The magnitude and distribution of the applicable structural design loads required by this section must be based on physical principles.
A-11
AC 21.17-4 Appendix A PL.2215 Flight load conditions.
(a) The applicant must determine the structural design loads resulting from the following flight conditions:
(1) Atmospheric gusts where the magnitude and gradient of these gusts are based on measured gust statistics.
(2) Symmetric and asymmetric maneuvers.
(3) Asymmetric thrust resulting from the failure of a propeller or engine.
(b) There must be no vibration or buffeting severe enough to result in structural damage, at any speed up to dive speed, within the structural design envelope, in any configuration and power setting.
PL.2220 Ground and water load conditions.
The applicant must determine the structural design loads resulting from taxi, takeoff, landing, and handling conditions on the applicable surface in normal and adverse attitudes and configurations.
PL.2225 Component loading conditions.
The applicant must determine the structural design loads acting on:
(a) Each engine mount and its supporting structure such that both are designed to withstand loads resulting from—
(1) Powerplant operation combined with flight gust and maneuver loads; and
(2) For non-reciprocating powerplants, sudden powerplant stoppage.
(b) Each flight control and high-lift surface, their associated system and supporting structure resulting from—
(1) The inertia of each surface and mass balance attachment;
(2) Flight gusts and maneuvers;
(3) Pilot or automated system inputs;
(4) System induced conditions, including jamming and friction; and
(5) Taxi, takeoff, and landing operations on the applicable surface, including downwind taxi and gusts occurring on the applicable surface.
(c) A pressurized cabin resulting from the pressurization differential—
(1) From zero up to the maximum relief pressure combined with gust and maneuver loads;
(2) From zero up to the maximum relief pressure combined with ground and water loads if the aircraft may land with the cabin pressurized; and
(3) At the maximum relief pressure multiplied by 1.33 for aircraft to be approved for operation to 45,000 feet or by a factor of 1.67 for aircraft to be approved for operation above 45,000 feet, omitting all other loads.
A-12
AC 21 .17-4 Appendix A
(d) Engine-driven lift device assemblies, considering loads resulting from flight and ground conditions, as well limit input torque at any engine-driven lift device rotational speed.
PL.2230 Limit and ultimate loads.
The applicant must determine—
(a) The limit loads, which are equal to the structural design loads unless otherwise specified elsewhere in these airworthiness criteria; and
(b) The ultimate loads, which are equal to the limit loads multiplied by a 1.5 factor of safety unless otherwise specified elsewhere in these airworthiness criteria.
Structural Performance PL.2235 Structural strength.
The structure must support:
(a) Limit loads without—
(1) Interference with the safe operation of the aircraft; and
(2) Detrimental or permanent deformation.
(b) Ultimate loads.
PL.2240 Structural durability.
(a) The applicant must develop and implement inspections or other procedures to prevent structural failures due to foreseeable causes of strength degradation, which could result in serious or fatal injuries, or extended periods of operation with reduced safety margins. Each of the inspections or other procedures developed under this section must be included in the Airworthiness Limitations Section of the ICA, required by PL.1529.
(b) If safety-by-design (fail-safe) is used to comply with paragraph (a) of this section, safety-byinspection (damage tolerance) must also be incorporated to reliably detect structural damage before the damage could result in structural failure.
(c) For pressurized aircraft:
(1) The aircraft must be capable of continued safe flight and landing following a sudden release of cabin pressure, including sudden releases caused by door and window failures.
(2) For aircraft with maximum operating altitude greater than 41,000 feet, the procedures developed for compliance with paragraph (a) of this section must be capable of detecting damage to the pressurized cabin structure before the damage could result in rapid decompression that would result in serious or fatal injuries.
(d) The aircraft must be designed to minimize hazards to the aircraft due to structural damage caused by high-energy fragments from an uncontained engine or rotating machinery failure.
(e) Engine-driven lift devices, control mechanisms, components, and related engine structure necessary to transmit loads from the engine-driven lift device to the airframe must comply with the damage tolerance and fatigue criteria of this section.
PL.2241 Aeromechanical stability.
A-13
AC 21 .17-4 Appendix A
(a) The aircraft must be free from dangerous oscillations and aeromechanical instabilities, including ground resonance and air resonance—
(1) For all configurations and conditions of operation on the ground and in flight, and
(2) Accounting for critical failures, malfunctions, and adverse conditions.
(b) The applicant must establish tolerances for all critical quantities that affect aeromechanical stability.
PL.2245 Aeroelasticity.
(a) The aircraft including the engine-driven lift devices must be free from flutter, control reversal, and divergence—
(1) At all speeds within and sufficiently beyond the structural design envelope;
(2) For any configuration and condition of operation;
(3) Under each appropriate rotational speed and power condition;
(4) Accounting for critical degrees of freedom, including critical structural modes; and
(5) Accounting for any critical failures, malfunctions, and adverse conditions.
(b) The applicant must establish tolerances for all quantities that affect aeroelastic stability.
Design PL.2250 Design and construction principles.
(a) The applicant must design each part, article, and assembly for the expected operating conditions of the aircraft.
(b) Design data must adequately define the part, article, or assembly configuration, its design features, and any materials and processes used.
(c) The applicant must determine the suitability of each design detail and part having an important bearing on safety in operations.
(d) The control system must be free from jamming, excessive friction, and excessive deflection when the aircraft is subjected to expected limit airloads.
(e) Doors, canopies, and exits must be protected against inadvertent opening in flight, unless shown to create no hazard when opened in flight.
(f) For critical parts, other than those that meet the definition of a critical part under Subpart I or J, the following requirements apply:
(1) A critical part is a part, the failure of which could have a catastrophic effect upon the aircraft, and for which critical characteristics have been identified which must be controlled to ensure the required level of integrity.
(2) If the type design includes critical parts, a critical parts list shall be established. Procedures shall be established to define the critical design characteristics, identify processes that affect those characteristics, and identify the design change and process change controls necessary for showing compliance with the quality assurance requirements of 14 CFR part 21.
A-14
AC 21 .17-4 Appendix A PL.2255 Protection of structure.
(a) The applicant must protect each part of the aircraft, including small parts such as fasteners, against deterioration or loss of strength due to any cause likely to occur in the expected operational environment.
(b) Each part of the aircraft must have adequate provisions for ventilation and drainage.
(c) For each part that requires maintenance, preventive maintenance, or servicing, the applicant must incorporate a means into the aircraft design to allow such actions to be accomplished.
PL.2260 Materials and processes.
(a) The applicant must determine the suitability and durability of materials used for parts, articles, and assemblies, accounting for the effects of likely environmental conditions expected in service, the failure of which could prevent continued safe flight and landing.
(b) The methods and processes of fabrication and assembly used must produce consistently sound structures. If a fabrication process requires close control to reach this objective, the applicant must perform the process under an approved process specification.
(c) Except as provided in paragraphs (f) and (g) of this section, the applicant must select design values that ensure material strength with probabilities that account for the criticality of the structural element. Design values must account for the probability of structural failure due to material variability.
(d) If material strength properties are required, a determination of those properties must be based on sufficient tests of material meeting specifications to establish design values on a statistical basis.
(e) If thermal effects are significant on a critical component or structure under normal operating conditions, the applicant must determine those effects on allowable stresses used for design.
(f) Design values, greater than the minimums specified by this section, may be used, where only guaranteed minimum values are normally allowed, if a specimen of each individual item is tested before use to determine that the actual strength properties of that particular item will equal or exceed those used in the design.
(g) An applicant may use other material design values if approved by the Administrator.
PL.2265 Special factors of safety.
(a) The applicant must determine a special factor of safety for each critical design value for each part, article, or assembly for which that critical design value is uncertain, and for each part, article, or assembly that is—
(1) Likely to deteriorate in service before normal replacement; or
(2) Subject to appreciable variability because of uncertainties in manufacturing processes or inspection methods.
(b) The applicant must determine a special factor of safety using quality controls and specifications that account for each—
(1) Type of application;
(2) Inspection method;
A-15