AC 21 .17-4 Appendix A
(3) Structural test requirement;
(4) Sampling percentage; and
(5) Process and material control.
(c) The applicant must multiply the highest pertinent special factor of safety in the design for each part of the structure by each limit and ultimate load, or ultimate load only, if there is no corresponding limit load, such as occurs with emergency condition loading.
Structural Occupant Protection PL.2270 Emergency conditions.
(a) The aircraft, even when damaged in an emergency landing, must protect each occupant against injury that would preclude egress when—
(1) Properly using safety equipment and features provided for in the design;
(2) The occupant experiences ultimate static inertia loads likely to occur in an emergency landing; and
(3) Items of mass, including engines, within, a bove, immediately adjacent to, or aft of the cabin, that could injure an occupant, experience ultimate static inertia loads likely to occur in an emergency landing.
(b) The emergency landing conditions specified in paragraph (a)(1) and (a)(2) of this section, must—
(1) Include dynamic conditions that are likely to occur in an emergency landing; and
(2) Not generate loads experienced by the occupants, which exceed established human injury criteria for human tolerance due to restraint or contact with objects in the aircraft.
(c) The aircraft must provide protection for all occupants, accounting for likely flight, ground, and emergency landing conditions.
(d) Each occupant protection system must perform its intended function and not create a hazard that could cause a secondary injury to an occupant. The occupant protection system must not prevent occupant egress or interfere with the operation of the aircraft when not in use.
(e) Each baggage and cargo compartment must—
(1) Be designed for its maximum weight of contents and for the critical load distributions at the maximum load factors corresponding to the flight and ground load conditions determined under these airworthiness criteria;
(2) Have a means to prevent the contents of the compartment from becoming a hazard by impacting occupants or shifting; and
(3) Protect any controls, wiring, lines, equipment, or accessories whose damage or failure would affect safe operations.
SUBPART D—DESIGN AND CONSTRUCTION PL.2300 Flight control systems.
(a) The applicant must design flight control systems to:
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AC 21 .17-4 Appendix A
(1) Operate easily, smoothly, and positively enough to allow proper performance of their functions;
(2) Protect against likely hazards; and
(3) Ensure that the flightcrew is made suitably aware whenever the means of primary flight control approaches the limits of control authority.
(b) The applicant must design trim systems or trim functions, if installed, to:
(1) Protect against inadvertent, incorrect, or abrupt trim operation; and
(2) Provide information that is required for safe operation.
(c) Features that protect the aircraft against loss of control, or exceeding critical limits, must be designed such that there are no adverse flight characteristics in aircraft response to flight-control inputs, unsteady atmospheric conditions, and other likely conditions, including simultaneous limiting events.
PL.2305 Landing gear systems.
(a) The landing gear must be designed to—
(1) Provide stable support and control to the aircraft during surface operation; and
(2) Account for likely system failures and likely operation environments (including anticipated limitation exceedances and emergency procedures).
(b) All aircraft must have a reliable means of—
(1) Stopping the aircraft with sufficient kinetic energy absorption to account for landing. Aircraft that are required to demonstrate aborted takeoff capability must account for this additional kinetic energy; and
(2) Holding the aircraft in position when parked.
(c) For aircraft that have a system that actuates the landing gear, there is—
(1) A positive means to keep the landing gear in the landing position; and
(2) An alternative means available to bring the landing gear in the landing position when a nondeployed system position would be a hazard.
PL.2310 Flotation.
(a) If certification for intended operations on water is requested, the aircraft must—
(1) Provide buoyancy of 80% in excess of the buoyancy required to support the maximum weight of the aircraft in fresh water; and
(2) Have sufficient margin so that the aircraft will stay afloat at rest in calm water without capsizing in case of a likely float or hull flooding.
(b) If certification for emergency flotation is requested, the aircraft must:
(1) Be equipped with an approved emergency flotation system;
(2) Have flotation units of the emergency flotation system and their attachments to the aircraft capable of withstanding the applicable water loads; and A-17
AC 21.17-4 Appendix A
(3) Be shown to maintain its intended floating attitude in the sea conditions selected by the applicant.
(c) If certification with ditching provisions is requested, the aircraft must:
(1) Be equipped with an approved emergency flotation system that does not rely on manual activation;
(2) Withstand the applicable water loads; and
(3) Be shown to have a safe water entry and to maintain its intended floating attitude in the sea conditions selected by the applicant.
PL.2311 Bird Strike.
The aircraft must be capable of continued safe flight and landing after impact with a 2.2-lb (1.0 kg) bird.
Occupant System Design Protection PL.2315 Means of egress and emergency exits.
With the cabin configured for takeoff or landing, the aircraft is designed to:
(a) Facilitate rapid and safe evacuation of the aircraft in conditions likely to occur following an emergency landing, including on water if an emergency flotation system is included.
(b) Have means of egress (openings, exits, or emergency exits), that can be readily located and opened from the inside and outside. The means of opening must be simple and obvious and marked inside and outside the aircraft. If an emergency flotation system is included, the means of egress must be above the water in the intended floating attitude.
(c) Have easy access to emergency exits when present.
PL.2320 Occupant physical environment.
(a) The applicant must design the aircraft to—
(1) Allow clear communication between the flightcrew and passengers;
(2) Protect the pilot and flight controls from propellers; and
(3) Protect the occupants from serious injury due to damage to windshields, windows, and canopies.
(b) The aircraft must provide each occupant with air at a breathable pressure, free of hazardous concentrations of gases, vapors, and smoke during normal operations and likely failures.
(c) If a pressurization system is installed in the aircraft, it must be designed to protect against—
(1) Decompression to an unsafe level; and
(2) Excessive differential pressure.
(d) If an oxygen system is installed in the aircraft, it must—
(1) Effectively provide oxygen to each user to prevent the effects of hypoxia; and
(2) Be free from hazards in itself, in its method of operation, and its effect upon other components.
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AC 21 .17-4 Appendix A Fire and High Energy Protection PL.2325 Fire protection.
(a) The following materials must be self-extinguishing—
(1) Insulation on electrical wire and electrical cable; and
(2) Materials in the baggage and cargo compartments inaccessible in flight.
(b) The following materials must be flame resistant—
(1) Materials in each compartment accessible in flight; and
(2) Any equipment associated with any electrical cable installation and that would overheat in the event of circuit overload or fault.
(c) Thermal/acoustic materials in the fuselage, if installed, must not be a flame propagation hazard.
(d) Sources of heat within each baggage and cargo compartment that are capable of igniting adjacent objects must be shielded and insulated to prevent such ignition.
(e) Each baggage and cargo compartment must—
(1) Be located where a fire would be visible to the pilots and be accessible for the manual extinguishing of a fire,
(2) Be equipped with a smoke or fire detection system that warns the pilot, or
(3) Be constructed of, or lined with, fire resistant materials.
(f) There must be a means to extinguish any fire in the cabin such that the pilot, while seated, can easily access the fire extinguishing means.
(g) Each area where flammable fluids or vapors might escape by leakage of a fluid system must -
(1) Be defined; and
(2) Have a means to minimize the probability of fluid and vapor ignition, and the resultant hazard, if ignition occurs.
PL.2330 Fire protection in fire zones and adjacent areas.
(a) Flight controls, engine mounts, and other flight structures within or adjacent to fire zones must be capable of withstanding the effects of a fire.
(b) Engines in a fire zone must remain attached to the aircraft in the event of a fire.
(c) In fire zones, terminals, equipment, and electrical cables used during emergency procedures must perform their intended function in the event of a fire.
(d) A fire in a fire zone must not preclude continued safe flight and landing.
PL.2335 Lightning and static electricity protection.
(a) The aircraft must be protected against catastrophic effects from lightning.
(b) The aircraft must be protected against hazardous effects caused by an accumulation of electrostatic charge.
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AC 21 .17-4 Appendix A SUBPART E—POWERPLANT PL.2400 Powerplant installation.
(a) For the purpose of this subpart, the aircraft powerplant installation must include each component necessary for propulsion, which affects propulsion safety.
(b) Each aircraft engine and propeller must have a type certificate or be approved under the aircraft type certificate using criteria found in subparts I and J. Engine-driven lift devices and related engine structures necessary to transmit loads from the device to the airframe must also comply with all applicable design load conditions and safety factors defined in subpart C.
(c) The applicant must construct and arrange each powerplant installation to account for—
(1) Likely operating conditions, including foreign-object threats;
(2) Sufficient clearance of moving parts to other aircraft parts and their surroundings;
(3) Likely hazards in operation including hazards to ground personnel; and
(4) Vibration, flutter, and fatigue.
(d) Hazardous accumulations of fluids, vapors, or gases must be isolated from the aircraft and personnel compartments and be safely contained or discharged.
(e) Powerplant components must comply with their component limitations and installation instructions or be shown not to create a hazard.
(f) Engine-driven lift devices and the engine, components, controls, and drive systems that support those devices must be shown to have sufficient endurance and durability.
PL.2405 Power or thrust control systems.
(a) Any power or thrust control system or powerplant control system must be designed so no unsafe condition results during normal operation of the system.
(b) Any single failure or likely combination of failures or malfunctions of a power or thrust control system or powerplant control system must not prevent continued safe flight and landing of the aircraft.
(c) Inadvertent flightcrew operation of a power or thrust control system or powerplant control system must be prevented, or if not prevented, must not prevent continued safe flight and landing of the aircraft.
PL.2410 Powerplant installation hazard assessment.
The applicant must assess each powerplant separately and in relation to other aircraft systems and installations to show that any hazard resulting from the likely failure of any powerplant system, component, or accessory will not—
(a) Prevent continued safe flight and landing or, if continued safe flight and landing cannot be ensured, the hazard has been minimized;
(b) Cause serious injury that may be avoided; and
(c) Require immediate action by any crewmember for continued operation of any remaining powerplant system.
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AC 21.17-4 Appendix A PL.2415 Powerplant ice protection.
(a) The aircraft design, including the inlet system, must prevent foreseeable accumulation of ice or snow that adversely affects powerplant operation.
(b) The powerplant installation design must prevent any accumulation of ice or snow that adversely affects powerplant operation, in those icing conditions for which certification is requested.
PL.2425 Powerplant operational characteristics.
(a) Each installed powerplant must operate without any hazardous characteristics during normal and emergency operation within the range of operating limitations for the aircraft and the engine.
(b) The design must provide for the shutdown and restart of the powerplant in flight within an established operational envelope.
PL.2430 Energy system.
(a) The energy system must—
(1) Be designed and arranged to provide independence within the system, so that failure of any one component will not result in unacceptable loss of energy supply;
(2) Be designed to prevent catastrophic events due to lightning strikes, taking into account direct and indirect effects on the aircraft;
(3) Provide the energy necessary to ensure each powerplant functions properly in all likely operating conditions;
(4) Provide the flightcrew with a means to determine the total useable energy available and provide uninterrupted supply of that energy when the system is correctly operated, accounting for likely energy fluctuations;
(5) Provide a means to safely remove or isolate the energy stored in the system from the aircraft;
and
(6) Be designed to retain energy under all likely operating conditions and to minimize hazards to occupants and first responders following an emergency landing or otherwise survivable impact (crash landing).
(b) Each energy-storage system must—
(1) Withstand the loads under likely operating conditions without failure; and
(2) Be isolated from personnel compartments and protected from likely hazards.
(c) Each energy-storage recharging system must be designed to—
(1) Prevent improper recharging; and
(2) Prevent the occurrence of hazard to the aircraft or to persons during recharging.
PL.2440 Powerplant fire protection.
There must be means to isolate and mitigate hazards to the aircraft in the event of a powerplant system fire or overheat in operation.
SUBPART F—EQUIPMENT A-21
AC 21.17-4 Appendix A PL.2500 Aircraft level systems requirements.
This section applies generally to installed equipment and systems unless a section of these airworthiness criteria imposes requirements for a specific piece of equipment, system, or systems.
(a) The equipment and systems required for an aircraft to operate safely in the kinds of operations for which certification is requested must be designed and installed to—
(1) Meet the level of safety applicable to the certification and performance level of the aircraft;
and
(2) Perform their intended function throughout the operating and environmental limits for which the aircraft is certificated.
(b) The systems and equipment not covered by paragraph (a) of this section, considered separately and in relation to other systems, must be designed and installed so their operation does not have an adverse effect on the aircraft or its occupants.
PL.2505 Function and installation.
When installed, each item of equipment must function as intended.
PL.2510 Equipment, systems, and installations.
This section applies to failures or abnormal operation of any equipment or system installed on the aircraft unless superseded by requirements contained in another section of these airworthiness criteria for which failures or abnormal operations are specified. The applicant must design and install each system and equipment, such that there is a logical and acceptable inverse relationship between the average probability and the severity of failure conditions to the extent that:
(a) Each catastrophic failure condition is extremely improbable;
(b) Each hazardous failure condition is extremely remote; and
(c) Each major failure condition is remote.
PL.2515 Electrical- and electronic-system lightning protection.
(a) Each electrical or electronic system that performs a function, the failure of which would prevent the continued safe flight and landing of the aircraft, must be designed and installed such that—
(1) The function at the aircraft level is not adversely affected during and after the time the aircraft is exposed to lightning; and
(2) The system recovers normal operation of that function in a timely manner after the aircraft is exposed to lightning unless the system’s recovery conflicts with other operational or functional requirements of the system.
(b) For an aircraft approved for operation under instrument flight rules (IFR), each electrical and electronic system that performs a function, the failure of which would reduce the capability of the aircraft or the ability of the flightcrew to respond to an adverse operating condition, must be designed and installed such that the system recovers normal operation of that function in a timely manner after the aircraft is exposed to lightning.
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AC 21 .17-4 Appendix A PL.2520 High-intensity Radiated Fields (HIRF) protection.
(a) Each electrical or electronic system that performs a function, the failure of which would prevent the continued safe flight and landing of the aircraft, must be designed and installed such that—
(1) The function at the aircraft level is not adversely affected during and after the time the aircraft is exposed to the HIRF environment; and
(2) The system recovers normal operation of that function in a timely manner after the aircraft is exposed to the HIRF environment, unless the system's recovery conflicts with other operational or functional requirements of the system.
(b) For aircraft approved for IFR operations, each electrical and electronic system that performs a function, the failure of which would reduce the capability of the aircraft or the ability of the flightcrew to respond to an adverse operating condition, must be designed and installed such that the system recovers normal operation of that function in a timely manner after the aircraft is exposed to the HIRF environment.
PL.2525 System power generation, storage, and distribution.
The power generation, storage, and distribution for any system must be designed and installed to—
(a) Supply the power required for operation of connected loads during all intended operating conditions;
(b) Ensure no single failure or malfunction of any one power supply, distribution system, or other utilization system will prevent the system from supplying the essential loads required for continued safe flight and landing; and
(c) Have enough capacity, if the primary source fails, to supply essential loads, including noncontinuous essential loads for the time needed to complete the function required for continued safe flight and landing.
PL.2530 External and cockpit lighting.
(a) The applicant must design and install all lights to minimize any adverse effects on the performance of flightcrew duties.
(b) Any position and anti-collision lights, if required by 14 CFR part 91, must have the intensities, flash rate, colors, fields of coverage, and other characteristics to provide sufficient time for another aircraft to avoid a collision.
(c) Any position lights, if required by 14 CFR part 91, must include red lighting on the left side of the aircraft, green lighting on the right side of the aircraft, spaced laterally as far apart as practicable, and white lighting facing aft, located on an aft portion of the aircraft or on the wing tips.
(d) Any taxi and landing lights must be designed and installed so they provide sufficient light for night operations.
(e) For aircraft intended for operations on water, riding lights must provide a white light visible in clear atmospheric conditions.
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AC 21.17-4 Appendix A PL.2535 Safety equipment.
Safety and survival equipment, required by the operating rules of title 14, chapter I, must be reliable, readily accessible, easily identifiable, and clearly marked to identify its method of operation.
PL.2540 Flight in icing conditions.
An applicant who requests certification for flight in icing conditions must show the following in the icing conditions for which certification is requested:
(a) The ice protection system provides for safe operation; and
(b) The aircraft design must provide protection from slowing to less than the minimum speeds defined in the flight profiles established under PL.2110 when the autopilot is operating.
PL.2545 Pressurized systems elements.
Pressurized systems must withstand appropriate proof and burst pressures.
PL.2550 Equipment containing high-energy rotors.
Equipment containing high-energy rotors must be designed or installed to protect the occupants and aircraft from uncontained fragments.
SUBPART G—FLIGHTCREW INTERFACE AND OTHER INFORMATION PL.2600 Flightcrew interface.
(a) The pilot compartment, its equipment, and its arrangement to include pilot view, must allow each pilot to perform their duties for all sources of lift and phases of flight and perform any maneuvers within the approved flight envelope of the aircraft, without excessive concentration, skill, alertness, or fatigue.
(b) The applicant must install flight, navigation, surveillance, and powerplant controls and displays, as needed, so qualified flightcrew can monitor and perform defined tasks associated with the intended functions of systems and equipment, without excessive concentration, skill, alertness, or fatigue. The system and equipment design must minimize flightcrew errors, which could result in additional hazards.
PL.2605 Installation and operation.
(a) Each item of installed equipment related to the flightcrew interface must be labelled, if applicable, as to it identification, function, or operating limitations, or any combination of these factors.
(b) There must be a discernible means of providing system operating parameters required to operate the aircraft, including warnings, cautions, and normal indications to the responsible crewmember.
(c) Information concerning an unsafe system operating condition must be provided in a timely manner to the crewmember responsible for taking corrective action. The information must be clear enough to avoid likely crewmember errors.
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AC 21 .17-4 Appendix A PL.2610 Instrument markings, control markings, and placards.
(a) Each aircraft must display in a conspicuous manner any placard and instrument marking necessary for operation.
(b) The design must clearly indicate the function of each cockpit control, other than primary flight controls.
(c) The applicant must include instrument marking and placard information in the Aircraft Flight Manual.
PL.2615 Flight, navigation, and powerplant instruments.
(a) Installed systems must provide the flightcrew member who sets or monitors parameters for the flight, navigation, and powerplant, the information necessary to do so during each phase of flight and source of lift. This information must—
(1) Be presented in a manner that the crewmember can monitor the parameter and determine trends, as needed, to operate the aircraft; and
(2) Include limitations, unless the limitations cannot be exceeded in all intended operations.
(b) Indication systems that integrate the display of flight or powerplant parameters to operate the aircraft, or are required by the operating rules of title 14, chapter I, must—
(1) Not inhibit the primary display of flight or powerplant parameters needed by any flightcrew member in any normal mode of operation; and
(2) In combination with other systems, be designed and installed so information essential for continued safe flight and landing will be available to the flightcrew in a timely manner after any single failure or probable combination of failures.
PL.2620 Aircraft flight manual.
The applicant must provide an Aircraft Flight Manual that must be delivered with each aircraft.
(a) The Aircraft Flight Manual must contain the following information—
(1) Aircraft operating limitations;
(2) Aircraft operating procedures;
(3) Performance information;
(4) Loading information; and
(5) Other information that is necessary for safe operation because of design, operating, or handling characteristics.
(b) The portions of the Aircraft Flight Manual containing the information specified in paragraphs
(a)(1) through (a)(4) of this section must be approved by the FAA in a manner specified by the Administrator.
SUBPART H—AIRWORTHINESS CRITERIA FOR INSTRUMENT FLIGHT PL.2701 General.
A powered-lift may not be type certificated for operation under the instrument flight rules (IFR) unless it meets the design and installation requirements contained in this subpart.
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AC 21 .17-4 Appendix A PL.2703 IFR flight envelope.
The applicant must determine an approved IFR flight envelope specifically for operations for flight into IFR conditions. If the approved IFR flight envelope differs from the approved flight envelope, then the applicant must use instrument flight speeds to comply with this subpart.
PL.2705 Definitions.
(a) VYI means instrument climb speed, utilized instead of VY for compliance with the climb requirements for instrument flight, if different than climb speed as defined in PL.2120.
(b) VMINI means instrument flight minimum speed, utilized in complying with minimum limit speed requirements for instrument flight, if different than the flight profiles established under PL.2110.
(c) A practical flight envelope means a flight envelope where, in the event of flight control, propulsive, or stability augmentation malfunctions, compliance with controllability and maneuverability requirements must be demonstrated.
PL.2707 Trim.
The aircraft must meet the requirements in PL.2140 for all approved IFR airspeeds, power settings, and configurations appropriate to the type.
PL.2709 Stability and handling qualities.
The aircraft must meet the requirements in PL.2145 for the approved IFR airspeeds, power settings, and configurations appropriate to the type.
PL.2711 Stability augmentation.
For any failure or combination of failures not shown to be extremely improbable, the aircraft must be capable of continued safe flight and landing. In addition—
(a) The aircraft must remain safely controllable when the failure or malfunction occurs within the approved IFR flight envelope; and
(b) The overall flight characteristics must allow for prolonged flight without undue pilot effort.
Additional unrelated probable failures affecting the control system must be considered. In addition—
(1) The controllability, maneuverability, and stability requirements in subpart B must be met throughout a practical flight envelope; and
(2) The flight control, trim, and flying qualities must not be reduced below that needed for continued safe flight and l anding.
PL.2713 Equipment, systems, and installation.
The basic equipment and installation must comply with PL.2500, PL.2505, PL.2510, PL.2525 and PL.2615, with the following additions:
(a) Instrument systems and other systems essential for IFR flight that could be adversely affected by icing must be adequately protected when exposed to atmospheric icing conditions.
(b) For each instrument essential for instrument flight— A-26
AC 21.17-4 Appendix A
(1) The equipment, systems, and installations must be designed so that one display of the information essential for continued safe flight and l anding will remain available to the flying pilot after any single failure or combination of failures that is not shown to be extremely improbable either—
(i) Without pilot action, or
(ii) With pilot action if the aircraft exhibits sufficient flying qualities under PL.2709.
(2) Instruments, systems, or equipment that are interconnected for a second pilot must be designed to ensure continued normal functioning of pilot and copilot instruments in the event of any malfunction not shown to be extremely improbable.
(3) For single-pilot configurations, instruments which require a static source must be provided with a means of selecting a calibrated alternate source.
PL.2715 Aircraft flight manual.
An Aircraft Flight Manual or Aircraft Flight Manual IFR Supplement must be provided and must contain—
(a) Limitations. The approved IFR flight envelope, the IFR flightcrew composition, the revised kinds of operation, and the steepest IFR precision approach gradient for which the powered-lift is approved;
(b) Procedures. Required information for proper operation of IFR systems and the recommended procedures in the event of stability augmentation or electrical system failures; and
(c) Performance. If VYI differs from VY, climb performance at VYI and with maximum continuous power throughout the ranges of weight, altitude, and temperature for which approval is requested.
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