Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations 3023 includes brokers. The rule would have (a) * * * FOR FURTHER INFORMATION CONTACT: a carryover cost effect because each (2) * * * Norm Martenson, FAA, International subsequent replacement would require (xii) Primary enclosures constructed Office, ANM–116, Transport Airplane coated wire or some other acceptable on or after February 20, 1998 and floors Directorate, Aircraft Certification material, such as galvanized expanded replaced on or after that date, must Service, 1601 Lind Avenue SW., metal. However, the increased cost of comply with the requirements in this Renton, WA 98055–4056; telephone coated wire would be made up, at least paragraph (a)(2). On or after January 21, (425) 227–2196. partially, over time because coated wire 2000, all primary enclosures must be in SUPPLEMENTARY INFORMATION: will provide longer use. compliance with the requirements in This rule contains no reporting or this paragraph (a)(2). If the suspended Background recordkeeping requirements. floor of a primary enclosure is Ilyushin Aviation Complex, 45 constructed of metal strands, the strands Executive Order 12372 Leningradsky Prospect, Moscow, must either be greater than 1⁄8 of an inch 125190, Russia, has applied for Russian This program/activity is listed in the in diameter (9 gauge) or coated with a type certification of their Model Il–96T Catalog of Federal Domestic Assistance material such as plastic or fiberglass. airplane by the Aviation Register (AR) of under No. 10.025 and is subject to The suspended floor of any primary the Interstate Aviation Committee in Executive Order 12372, which requires enclosure must be strong enough so that accordance with existing AR standards. intergovernmental consultation with the floor does not sag or bend between The AR is authorized to perform State and local officials. (See 7 CFR part the structural supports. airworthiness certification functions on 3015, subpart V.) * * * * * behalf of the Commonwealth of Executive Order 12988 Independent States, including the § 3.11 [Amended] Russian government. In addition, This final rule has been reviewed 3. In § 3.11(a), the word ‘‘wire’’ is under Executive Order 12988, Civil Ilyushin applied for U.S. type removed from the last sentence, and the certification of the Model Il–96T on Justice Reform. It is not intended to word ‘‘mesh’’ is added in its place. have retroactive effect. This rule would February 16, 1993. not preempt any State or local laws, § 3.14 [Amended] Section 21.29 of 14 CFR part 21 of the Federal Aviation Regulations (FAR) regulations, or policies, unless they 4. In § 3.14(a)(9), the word ‘‘wire’’ is present an irreconcilable conflict with prescribes a reciprocal bilateral removed each time it appears. agreement between the U.S. and this rule. The Act does not provide Done in Washington, DC, this 13th day of administrative procedures which must exporting country as a requirement for January 1998. consideration of U.S. design or be exhausted prior to a judicial Craig A. Reed, challenge to the provisions of this rule. airworthiness approval of an imported Acting Administrator, Animal and Plant aeronautical product. Such agreements Paperwork Reduction Act Health Inspection Service. are known as bilateral aviation safety This rule contains no information [FR Doc. 98–1311 Filed 1–20–98; 8:45 am] agreements (BASA). Although the U.S. collection or recordkeeping BILLING CODE 3410±34±P does not presently have a BASA with requirements under the Paperwork Russia providing reciprocal acceptance Reduction Act of 1995 (44 U.S.C. 3501 of transport category airplanes, the FAA et seq.). DEPARTMENT OF TRANSPORTATION is working with the AR and Russian government officials to conclude an List of Subjects in 9 CFR Part 3 Federal Aviation Administration agreement of this nature. FAA Advisory Animal welfare, Marine mammals, Circular (AC) 21–23, Airworthiness Pets, Reporting and recordkeeping 14 CFR Part 25 Certification of Civil Aircraft, Engines, Propellers, and Related Products requirements, Research, Transportation. [Docket No. NM±139, Special Conditions Accordingly, 9 CFR part 3 is amended No. 25±ANM±135] Imported to the United States, provides as follows: further guidance in this regard. Special Conditions: Ilyushin Aviation A BASA with Russia may be PART 3ÐSTANDARDS Complex Model Il±96T Airplane concluded following successful completion of an assessment by the 1. The authority citation for part 3 AGENCY: Federal Aviation FAA and the AR of each other’s continues to read as follows: Administration (FAA), DOT. technical competence and regulatory Authority: 7 U.S.C. 2131–2159; 7 CFR 2.22, ACTION: Final special conditions. capability for performing airworthiness 2.80, and 371.2(d). certification functions. The scope of the SUMMARY: These special conditions are 2. Section 3.6 is amended as follows: agreement is defined by each authority issued for the Ilyushin Aviation a. In paragraph (a)(2)(x), the words in Implementation Procedures. FAA Complex Model Il–96T airplane. This ‘‘constructed of wire’’ are removed, and type certification of the Model Il–96T airplane will have novel and unusual the words ‘‘of mesh or slatted transport airplane is therefore design features when compared to the construction’’ are added in their place, conditional upon successful state of technology envisioned in the and the word ‘‘and’’ at the end of the implementation of a BASA with Russia, airworthiness standards of part 25 of the paragraph is removed. providing acceptance of transport b. In paragraph (a)(2)(xi), the period at Federal Aviation Regulations (FAR). category airplanes. the end of the paragraph is removed, These special conditions contain the One of the key elements of any BASA and ‘‘; and’’ is added in its place. additional safety standards that the assessment program is the shadow c. A new paragraph (a)(2)(xii) is added Administrator considers necessary to certification program. Under the to read as follows: establish a level of safety equivalent to Russian shadow certification program, that provided by the airworthiness FAA specialists are ‘‘shadowing’’ their § 3.6 Primary enclosures. standards of part 25. AR counterpart specialists during AR * * * * * EFFECTIVE DATE: February 20, 1998. certification of an example of the 3024 Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations aeronautical product that the BASA is certification of the Model Il–96T, the 6 pallets. The two cargo compartments intended to cover. This program is FAA will therefore accept the Russian on the lower deck have a total volume intended to provide FAA assessment type certification basis, plus any of 6,900 cubic feet, and can specialists with ample opportunity to additional requirements, and these accommodate a total of 32 LD–3 evaluate the AR certification process special conditions. As the program containers or 9 P–6 pallets. The Il–96T and the AR specialists’ technical progresses, other features of the Model has a maximum takeoff weight of competencies to support the Il–96T may be determined to be novel 595,240 lbs. and a maximum landing airworthiness authority responsibilities or unusual. The equivalent certification weight of 485,000 lbs. The maximum inherent in a bilateral agreement. The basis may therefore include other cruise altitude is 43,000 feet. Ilyushin Model Il–96T was selected as special conditions or exemptions not The structure of the Il–96T is the product for this shadow certification pertinent to these special conditions. generally of conventional design and which, if successful, would lead to a Since noise certification and emission construction. The landing gear system U.S.-Russian BASA. Conclusion of the requirements are beyond the scope of employs a center landing gear for use BASA and related implementation the possible future bilateral agreement, during ground handling conditions with procedures would, in turn, be followed the FAA will make findings of heavy airplane weights. The structural by issuance of a U.S. type certificate for compliance with the applicable U.S. design also makes use of an electronic that model. noise, fuel venting, and exhaust flight control system which provides the Under the anticipated provisions of emission requirements. The U.S. noise potential for a wide range of structural the future BASA, the AR has elected to certification basis for the Model Il–96T and system interactions. certify that the Model Il–96T complies is 14 CFR part 36 of the FAR, as The Model Il–96T flight control with the AP–25 type certification amended by Amendments 36–1 through system is an electro-hydromechanical standards, plus any additional 36–21, and any subsequent amendments system utilizing both fly-by-wire (FBW) requirements identified by the FAA to that are applicable on the date on which and conventional mechanical (cables ensure an equivalent level of safety to the U.S. type certificate is issued. In and push-pull rods) linkages between that provided by the U.S. type addition to compliance with part 36, the pilot control column and control surface certification standards. The AP–25 statutory provisions of Public Law 92– hydraulic actuators in two airworthiness standards, which were 574, ‘‘Noise Control Act of 1972,’’ simultaneously operated and developed as the successor to the require that the FAA issue a finding of synchronized channels. The NLGS–3 standards of the former Soviet regulatory adequacy pursuant to Section conventional mechanical channel, in Union, were approved by the AR in 611 of that Act. The Model Il–96T must normal operation, functions as a passive November 1993 and implemented in also comply with the fuel venting and redundancy of the FBW channel and Russia in July 1994. These standards exhaust emission requirements of 14 provides feedback to the pilots via the have also been accepted by many of the CFR part 34 of the FAR, as amended by Automatic Feel Load System. other Commonwealth of Independent Amendment 34–1, and any subsequent Hydraulic power to the flight control States for type certification of transport amendments that are applicable on the system is simultaneously provided by category airplanes. They were date the type certificate is issued. four independent hydraulic systems. established after extensive Special conditions are prescribed Functions are shared among these harmonization with part 25 of the FAR under the provisions of § 21.16 of the and the European Joint Airworthiness systems in order to ensure airplane FAR when the applicable regulations for control in the event of loss of one, two, Requirements (JAR)–25. The AP–25 type certification do not contain standards are similar to part 25 of the or three systems. The four systems are adequate or appropriate standards pressurized by variable displacement FAR; however, there are certain because of novel or unusual design specified differences in the pumps driven by the engine accessory features. As discussed below, the new gearbox. In addition, the systems can be requirements of the two documents. Ilyushin Model Il–96T airplane Based on the application date of powered by electrically driven pumps. incorporates a number of such design A ram air turbine (RAT)-driven pump is February 16, 1993, the U.S. type features. certification standards are part 25 of the available as an emergency hydraulic FAR, as amended by Amendments 25– Il–96T Design Features power source. 1 through 25–77, and these special Normal electrical power is supplied General conditions. In addition, the type by four constant frequency generators, certification basis includes the sections The Model Il–96T airplane presented one on each engine. An auxiliary power of part 25, as amended by Amendment for U.S. type certification is a long unit (APU) providing electrical and 25–80, pertaining to lightning range, four engine, transport category hydraulic supply is available for ground protection. Compliance with those cargo airplane powered by four (4) Pratt use only and is not used in flight. Five sections is required under the & Whitney PW2337 engines with 37,500 batteries provide an alternative source provisions of § 21.17(a)(1)(ii). lbs. thrust ratings and incorporating of electrical power for loads required to Because the AR has elected to certify Rockwell/Collins avionics. It is continue safe flight and landing in the that the Model Il–96T complies with the designed to be flown by a two-man case of failure of four generators. Russian type certification standards, the crew; however, it incorporates seats for The engine control system consists of FAA will make a comparison of the 2 additional crewmembers. The airplane a dual-channel electronic engine control Russian type certification basis and the is intended for cargo operation only and (EEC) mounted on the fan case of each U.S. type certification standards is designed to carry cargo on main and engine. Each EEC interfaces with described above. Based on this lower decks. The aircraft cargo loading various airplane computer systems. The comparison, the FAA will prescribe any system includes a large main deck cargo EEC provides gas generator control, additional requirements that are door (15.91 feet × 9.43 feet) and two engine limit protection, power necessary to ensure that the Model Il– lower deck cargo doors (8.69 feet × 5.74 management, thrust reverser control, 96T meets a level of safety equivalent to feet). The main cargo compartment on and engine parameter inputs for the that provided by the U.S. type the upper deck has a volume of 20,480 flight deck displays. The engine EEC certification standards. For U.S. cubic feet and can accommodate 25 P– and associated airplane related systems Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations 3025 form the complete propulsion control envisioned in the structural design and become part of the type certification system. regulations of part 25 of the FAR for basis in accordance with § 21.17(a)(2). Pitch and roll control inputs are made transport airplanes. Special Condition 3 Discussion of Comments through conventional flight deck central provides comprehensive criteria in control columns. The flight instruments which the structural design safety Notice of proposed special conditions are displayed on six cathode ray tube margins are dependent on systems No. SC–97–2–NM was published in the (CRT) displays. Two CRT’s are mounted reliability. Federal Register on April 9, 1997 (62 FR directly in front of both the pilot and 17117). No comments were received, Systems copilot and display primary flight and the special conditions are adopted instruments and navigational 4. Protection From Unwanted Effects of as proposed. information. The other two CRT’s are High Intensity Radiated Fields (HIRF) Applicability located in the center of the instrument These special conditions are panel and display engine parameters, The use of fly-by-wire designs to applicable initially to the Ilyushin warnings, and system diagnostics. command and control engines and flight Model Il–96T airplane. Should Ilyushin The type design of the Model Il–96T control surfaces increases the airplane’s Aviation Complex apply at a later date contains novel or unusual design susceptibility to HIRF sources external for a change to the type certificate to features not envisioned by the to the airplane. The airworthiness include another model incorporating the applicable part 25 airworthiness regulations do not provide adequate same novel or unusual design features, standards and therefore special requirements for protection from the special conditions would apply to conditions are considered necessary in unwanted effects of HIRF. that model as well under the provisions the following areas: High intensity radiated fields have the potential to cause adverse and of § 21.101(a)(1). Airframe potentially hazardous effects on fly-by- Conclusion 1. Center Landing Gear wire systems if design measures are not taken to ensure the immunity of such This action affects only certain The Ilyushin Il–96T landing gear systems. This is particularly true with unusual or novel design features on one arrangement includes a center braking the trend toward increased power levels model series of airplanes. It is not a rule landing gear under the fuselage. The from ground based transmitters and the of general applicability and affects only center main landing gear does not differ advent of space and satellite the manufacturer who applied to the from that of the right or left main communications. FAA for approval of these features on landing gear in construction and the airplane. The Model Il–96T is being designed performs the same functions. The with electrical interfaces between crew List of Subjects in 14 CFR Part 25 current landing gear design criteria are inputs and (1) the flight control applicable to conventional landing gear Aircraft, Aviation Safety, Reporting surfaces, and (2) the engines. These arrangements. Special Condition No. 1 and recordkeeping requirements. interfaces, and the interconnection provides additional taxi, takeoff, and The authority citation for these among the electronic subsystems landing criteria for this arrangement. special conditions is as follows: controlling these functions, can be 2. Design Maneuver Requirements susceptible to disruption of both Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704. In a conventional airplane with a command/response signals and the The Special Conditions hydro-mechanical flight control system, operational mode logic as a result of pilot inputs directly affect control electrical and magnetic interference. Accordingly, pursuant to the surface movement (both rate and Traditional airplane designs have authority delegated to me by the displacement) for a given flight utilized mechanical means to connect Administrator, the following special condition. In the Il–96T, the pilot’s the primary flight controls and the conditions are issued as part of the type controls and the flight control surfaces engine to the flight deck. This certification basis for the Ilyushin are connected through the electronic traditional design results in control Aviation Complex Model Il–96T series flight control system, which introduces paths that are substantially immune to airplanes. additional surface movements based on the effects of HIRF. A special condition 1. Center Landing Gear. its design control laws. The control is required to ensure that critical and Notwithstanding § 25.477 of the FAR, surface movement during maneuvers essential systems be designed and the requirements of §§ 25.473 and differs from the pilot control installed to preclude component 25.479 through § 25.485 apply, except as displacements in terms of both rate and damage and system upset or noted: displacement. The additional effects of malfunction due to the unwanted effects (a) In addition to the requirements of the electronic flight control system are of HIRF. Therefore, Special Condition § 25.473, landing should be considered not reflected in the current FAR; No. 4 is provided. on a level runway and on a runway therefore, Special Condition No. 2 is Special conditions may be issued and having a convex upward shape that may provided. amended, as necessary, as part of the be approximated by a slope of 1.5 type certification basis if the percent with the horizontal at main 3. Interaction of Systems and Structure Administrator finds that the landing gear stations. The maximum The Ilyushin Model Il–96T is airworthiness standards designated in loads determined from these two equipped with an electrical flight accordance with § 21.17(a)(1) do not conditions must be applied to each control system and a load alleviation contain adequate or appropriate safety main landing gear and to the center system that effects both gust and standards because of novel or unusual landing gear. maneuver loads. These systems can design features of an airplane. (b) The requirements of § 25.483 directly, or as a result of failure or Special conditions, as appropriate, are apply and, in addition, the condition malfunction, affect structural issued in accordance with § 11.49 after represented by the following figure also performance. This degree of system and public notice, as required by §§ 11.28 applies: structures interaction was not and 11.29(b), effective October 14, 1980, BILLING CODE 4910±13±P 3026 Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations

BILLING CODE 4910±13±C 1.0 and the coefficient of friction must pilot effort as specified in § 25.397 (c) In lieu of the requirements of be 0.8. concerning pilot effort forces, the § 25.485, the following apply: (2) The airplane is assumed to be in cockpit pitching control device is (1) The airplane is considered to be in static equilibrium, with the loads being suddenly moved to obtain extreme the level attitude with only the main applied at the ground contact points. positive pitching acceleration (nose up). and central wheels contacting the (3) All of the main gear units must be In defining the tail load condition, the ground. designed for the scrubbing or torsion response of the airplane must be taken loads, or both, induced by pivoting (2) Vertical reactions of one-half of the into account. Airplane loads which during ground maneuvers produced by: maximum vertical reaction obtained at occur subsequent to the point at which (i) Towing at the nose gear, no brakes each main and center gear in the level the normal acceleration at the center of applied; and landing conditions should be gravity exceeds the maximum positive (ii) Application of symmetrical or considered. The vertical loads must be limit maneuvering factor, n, need not be unsymmetrical forward thrust to aid combined with side loads that for the considered. pivoting and with or without braking on (b) Pitch maneuvering loads induced main gear are 0.8 of the vertical reaction the outside main gear closest to the by the system. In addition to the (on one side) acting inward and 0.6 of pivot center. requirements of § 25.331(c) of the FAR, the vertical reaction (on the other side) (f) The following applies to the center it must be established that pitch acting outward, and for the center gear landing gear in lieu of § 25.723, ‘‘Shock maneuver loads induced by the system are 0.7 of the vertical reaction acting in absorption tests’’: itself (e.g. abrupt changes in orders the same direction as main gear side (1) The center landing gear should not made possible by electrical rather than loads. (Drag load=0) fail in a test demonstrating its reserve mechanical combination of different (d) In addition to the requirements of energy absorption capacity at design inputs) are acceptably accounted for. § 25.489, ‘‘Ground handling landing weight, assuming airplane lift (c) Roll maneuver loads. In lieu of conditions,’’ the following applies: The no greater than the airplane weight compliance with § 25.349(a) of the FAR, airplane should be considered to be on acting during an impact simulating: the following conditions, speeds, spoiler a level runway and on a runway having (i) A center landing gear descent and aileron deflections (except as the a convex upward shape that may be velocity of 120 percent of the maximum deflections may be limited by pilot approximated by a slope of 1.5 percent aircraft descent velocity at the time of effort) must be considered in with the horizontal at main landing gear center landing gear ground contact; or combination with an airplane load stations. The ground reactions must be (ii) A 12 fps airplane landing impact factor of zero and of two-thirds of the distributed to the individual landing taking into account both the main and positive maneuvering factor used in gear units in a rational or conservative center landing gears acting during the design. In determining the required manner (zero lift, shock struts in the impact, whichever is more critical. aileron and spoiler deflections, the static position). 2. Design Maneuver Requirements. (a) torsional flexibility of the wing must be (e) In lieu of the requirements of Maximum elevator displacement at VA. considered in accordance with § 25.503, the following apply: In lieu of compliance with § 25.331(c)(1) § 25.301(b). (1) The airplane is assumed to pivot of the FAR, the airplane is assumed to (1) Conditions corresponding to about one of the outer main gears with be flying in steady level flight (point A1 steady rolling velocities must be the brakes locked on the selected gear. within the maneuvering envelope of investigated. In addition, conditions The limit vertical load factor must be § 25.333(b)) and, except as limited by corresponding to maximum angular Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations 3027

acceleration must be investigated. For (1) Maneuvering. At speeds from VMC limit loads. In particular, any significant the angular acceleration conditions, zero to VD, the following maneuvers must be nonlinearity (rate of displacement of rolling velocity may be assumed in the considered. In computing the tail loads, control surface, thresholds, or any other absence of a rational time history the yawing velocity may be assumed to system nonlinearities) must be investigation of the maneuver. be zero: accounted for in a realistic or (2) At VA, sudden deflection of the (i) With the airplane in unaccelerated conservative way when deriving limit cockpit roll control up to the limit is flight at zero yaw, it is assumed that the loads from limit conditions. assumed. The position of the cockpit cockpit yaw control device (pedal) is (2) The airplane must meet the roll control must be maintained until a suddenly displaced (with critical rate) strength requirements of part 25 (static steady roll rate is achieved and then to the maximum deflection, as limited strength, residual strength), using the must be returned suddenly to the by the stops. specified factors to derive ultimate loads (ii) With the cockpit yaw control neutral position. from the limit loads defined above. The device (pedal) deflected as specified in (3) At VC, the cockpit roll control effect of nonlinearities must be subparagraph (1) of this paragraph, it is must be moved suddenly and investigated beyond limit conditions to assumed that the airplane yaws to the maintained so as to achieve a rate of roll ensure the behavior of the systems resulting sideslip angle (beyond the not less than that obtained in paragraph presents no anomaly compared to the (2). static sideslip angle). (iii) With the airplane yawed to the behavior below limit conditions. (4) At VD, the cockpit roll control static sideslip angle with the cockpit However, conditions beyond limit must be moved suddenly and yaw control device deflected as conditions need not be considered when maintained so as to achieve a rate of roll specified in sub-paragraph (1) of this it can be shown that the airplane has not less than one third of that obtained paragraph, it is assumed that the cockpit design features that make it impossible in paragraph (2) of this paragraph. yaw control device is returned to to exceed those limit conditions. (5) It must also be established that roll neutral. (3) The airplane must meet the maneuver loads induced by the system 3. Interaction of Systems and aeroelastic stability requirements of itself (i.e., abrupt changes in orders Structure. (a) General. For an airplane § 25.629. made possible rather than mechanical equipped with flight control systems, (c) System in the failure condition. combination of different inputs) are load alleviation systems, or flutter For any system failure condition not acceptably accounted for. control systems that directly, or as a shown to be extremely improbable, the (d) Yaw maneuver loads. In lieu of result of a failure or malfunction, affect following apply: compliance with § 25.351 of the FAR, its structural performance, the influence (1) At the time of occurrence. Starting the airplane must be designed for loads of these systems and their failure resulting from the conditions specified from 1g level flight conditions, a conditions shall be taken into account realistic scenario, including pilot in subparagraphs (a) and (b) of this in showing compliance with subparts C paragraph. Unbalanced aerodynamic corrective actions, must be established and D of part 25 of the FAR. to determine the loads occurring at the moments about the center of gravity (b) System fully operative. With the time of failure and immediately after must be reacted in a rational or system fully operative, the following failure. The airplane must be able to conservative manner, considering the apply: principal masses furnishing the reacting (1) Limit loads must be derived in all withstand these loads, multiplied by an inertia forces. Physical limitations of the normal operating configurations of the appropriate factor of safety, related to airplane from the cockpit yaw control systems from all the deterministic limit the probability of occurrence of the device to the control surface deflection, conditions specified in subpart C, taking failure. These loads should be such as control stop position, maximum into account any special behavior of considered as ultimate loads for this power and displacement rate of the such systems or associated functions, or evaluation. The factor of safety is servo controls, and control law limiters any effect on the structural performance defined as follows: may be taken into account. of the airplane that may occur up to the BILLING CODE 4910±13±P 3028 Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations

BILLING CODE 4910±13±C divergence must be shown at increased failure condition, if the loads could (i) The loads must also be used in the speeds, so that the above margins are continue to the end of the flight. These damage tolerance evaluation required in maintained. loads must be combined with the § 25.571(b), if the failure condition is (iii) Notwithstanding subparagraph (1) deterministic limit load conditions probable. The loads may be considered of this paragraph, failures of the system specified in subpart C. that result in forced structural vibrations as ultimate loads for the damage tolerant (oscillatory failures) must not produce (ii) For static strength substantiation, evaluation. peak loads that could result in each part of the structure must be able (ii) Freedom from flutter and permanent deformation of primary to withstand the loads specified in divergence must be shown at speeds up structure. subparagraph (2)(i) of this paragraph to VD or 1.15 VC, whichever is greater. (2) For the continuation of the flight. multiplied by a safety factor depending However, at altitudes where the speed is For the airplane, in the failed on the probability of being in this failure limited by Mach number, compliance configuration and considering any state. need be shown only up to MD, as appropriate flight limitations, the The factor of safety is defined as defined in § 25.335(d). For failure following apply: follows: conditions that result in speed increases (i) Static and residual strength must BILLING CODE 4910±13±P beyond VC/MC, freedom from flutter and be determined for loads induced by the

BILLING CODE 4910±13±C (iii) For residual strength combined with the loads introduced by Qj=(Tj)(Pj) where: substantiation as defined in § 25.571(b), the failure condition plus two-thirds of for structures also affected by failure of the load increments of the conditions Tj=Average time spent in failure the system and with damage in condition j (in hours) specified in § 25.571(b) in both positive combination with the system failure, a and negative directions (if appropriate). Pj=Probability of occurrence of failure reduction factor may be applied to the The reduction factor is defined as mode j (per hour) residual strength loads of § 25.571(b). follows: Note: If Pj is greater than 10¥3 per flight However, the residual strength level hour, then a 1.5 factor of safety must be used. must not be less than the 1g flight load, BILLING CODE 4910±13±P

BILLING CODE 4910±13±C Note: If Pj is greater than 10¥3 per flight (iv) Freedom from flutter and Qj=(Tj)(Pj) where: hour, then a residual strength factor of 1.0 divergence must be shown up to a speed Tj=Average time spent in failure must be used. determined by the following figure: condition j (in hours) Pj=Probability of occurrence of failure BILLING 4910±13±P mode j (per hour) Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations 3029

BILLING CODE 4910±13±C (2) An evaluation must be made of the applicable to structure, the failure of V1=Clearance speed as defined in necessity to signal, during the flight, the which could prevent continued safe § 25.629(b)(2). existence of any failure condition that flight and landing. The following V2=Clearance speed as defined in could significantly affect the structural definitions are applicable to this special § 25.629(b)(1). capability of the airplane and for which condition: Qj=(Tj)(Pj) where: the associated reduction in Structural performance: Capability of Tj=Average time spent in failure airworthiness can be minimized by the airplane to meet the structural condition j (in hours) suitable flight limitations. The requirements of part 25. Pj=Probability of occurrence of failure assessment of the need for such signals Flight limitations: Limitations that mode j (per hour) must be carried out in a manner can be applied to the airplane flight Note: If Pj is greater than 10¥3 per flight consistent with the approved general conditions following an inflight hour, then the flutter clearance speed must warning philosophy for the airplane. occurrence and which are included in not be less than V2. (3) During flight, any failure condition the flight manual (e.g., speed limitations, avoidance of severe weather (v) Freedom from flutter and not shown to be extremely improbable, conditions, etc.). divergence must also be shown up to V1 in which the safety factor existing between the airplane strength capability Operational limitations: Limitations, in the above figure for any probable including flight limitations, that can be system failure condition combined with and loads induced by the deterministic limit conditions of subpart C of part 25 applied to the airplane operating any damage required or selected for conditions before dispatch (e.g., payload investigation in § 25.571(b). is reduced to 1.3 or less, must be signaled to the crew if appropriate limitations). (vi) If the time likely to be spent in the Probabilistic terms: The probabilistic procedures and limitations can be failure condition is not small compared terms (probable, improbable, extremely provided so that the crew can take to the damage propagation period, or if improbable) used in this special the loads induced by the failure action to minimize the associated condition should be understood as condition may have a significant reduction in airworthiness during the defined in AC 25.1309–1. influence on the damage propagation, remainder of the flight. Failure condition: The term failure then the effects of the particular failure (e) Dispatch with failure conditions. If condition is defined in AC 25.1309–1; condition must be addressed and the the airplane is to be knowingly however, this special condition applies corresponding inspection intervals dispatched in a system failure condition only to system failure conditions that adjusted to adequately cover this that reduces the structural performance have a direct impact on the structural situation. of the airplane, then operational performance of the airplane (e.g., failure (vii) If the mission analysis method is limitations must be provided whose conditions that induce loads or change used to account for continuous effects, combined with those of the the response of the airplane to inputs turbulence, all the systems failure failure condition, allow the airplane to such as gusts or pilot actions). conditions associated with their meet the structural requirements 4. Protection from Unwanted Effects probability must be accounted for in a described in paragraph (b) of this of High Intensity Radiated Fields rational or conservative manner in order special condition. Subsequent system (HIRF). In the absence of specific to ensure that the probability of failures must also be considered. requirements for protection from the exceeding the limit load is not higher Discussion: This special condition is unwanted effects of HIRF, the following than the prescribed value of the current intended to be applicable to flight apply: requirement. controls, load alleviation systems, and Each airplane system that performs (d) Warning considerations. For flutter control systems. The criteria critical functions must be designed and system failure detection and warning, provided by the special condition only installed to ensure that the operation the following apply: address the direct structural and operational capabilities of these (1) Before flight, the system must be consequences of the systems responses systems to perform critical functions are checked for failure conditions, not and performances and therefore cannot not adversely affected when the airplane shown to be extremely improbable, that be considered in isolation but should be is exposed to high intensity radiated degrade the structural capability of the included in the overall safety evaluation fields. airplane below the level intended in of the airplane. The presentation of Discussion: The Ilyushin Model Il– paragraph (b) of this special condition. these criteria may, in some instances, 96T will utilize electrical and electronic The crew must be made aware of these duplicate standards already established systems that perform critical functions. failures, if they exist, before flight. for this evaluation. The criteria are These systems include the electronic 3030 Federal Register / Vol. 63, No. 13 / Wednesday, January 21, 1998 / Rules and Regulations displays, integrated avionics computer, electromagnetic field strength of 100 MHz should be recorded. The test electronic engine controls, etc. The volts per meter, without the benefit of should be repeated with an appropriate existing airworthiness regulations do airplane structural shielding, in the modulation applied to the test signal. At not contain adequate or appropriate frequency range of 10 KHz to 18 GHz. each test point, the amplitude of the RF safety standards for the protection of Compliance Method: This paragraph test signal should be adjusted to the these systems from the effects of HIRF describes an acceptable method of peak values recorded during the which are external to the airplane. showing compliance with the HIRF unmodulated test. The modulation Airplane designs that utilize metal energy protection requirements. should be selected as the signal most skins and mechanical command and (1) Compliance Plan: The applicant likely to disrupt operation of the control means have traditionally been should present a plan for Aviation equipment under test based on its shown to be immune from the effects of Register approval, outlining how design characteristics. For example, HIRF energy from ground-based and compliance with the HIRF energy flight control systems might be airborne transmitters. With the trend protection requirements will be susceptible to 3 Hz square wave toward increased power levels from attained. This plan should also propose modulation while the video signals for these sources, plus the advent of space pass/fail criteria for the operation of CRT displays may be susceptible to 400 and satellite communications, the critical systems in the HIRF Hz sinusoidal modulation. If the worst environment. immunity of the airplane to HIRF energy case modulation is unknown or cannot (2) System Criticality: A hazard must be established. No universally be determined, default modulations can analysis should be performed by the accepted guidance to define the be used. Suggested default values are 1 applicant for approval by Aviation maximum energy level in which civilian KHz sine wave with 80% depth of airplane system installations must be Register to identify electrical and/or electronic systems which perform modulation in the frequency range from capable of operating safely has been 10 KHz to 400 MHz and 1 KHz square established. critical functions. These systems are candidates for the application of HIRF wave with greater than 90% depth of For the purposes of this special modulation from 400 MHz to 18 GHz. condition, the following definition energy protection requirements. (3) Compliance Verification: For frequencies where the unmodulated applies: signal caused deviations from normal Critical Functions: Functions whose Compliance with the HIRF energy protection requirements may be operation of the EUT, several different failure would contribute to or cause a modulating signals with various wave- failure condition that would prevent the demonstrated by tests, analysis, models, similarity with existing systems, or a forms and frequencies should be continued safe flight and landing of the applied. Modern laboratory equipment airplane. At this time the FAA and other combination thereof as acceptable to Aviation Register. Service experience may not be able to continuously scan airworthiness authorities are unable to alone is not acceptable since such the spectrum in the manner of analog precisely define or control the HIRF experience in normal flight operations equipment. These units will only energy level to which the airplane will may not include an exposure to the generate discrete frequencies. For such be exposed in service. Therefore, the HIRF environmental condition. equipment, the number of test points FAA hereby defines two acceptable (4) Pass/Fail Criteria: Acceptable and the dwell time at each test point interim methods for complying with the system performance is attained by requirement for protection of systems must be specified. For each decade of demonstrating that the system under that perform critical functions. the frequency test spectrum (a ten times consideration continues to perform its increase in frequency (i.e., 10 Kz to 100 (1) The applicant may demonstrate intended function during and after KHz) there should be at least 25 test that the critical systems, as installed in exposure to the required the airplane, are protected from the points, and for the decades from 10 electromagnetic fields. Deviations from MHz to 100 MHz, and 100 MHz to 1 external HIRF threat environment system specification may be acceptable defined in the following table: GHz there should be a minimum of 180 depending on an independent test points each. The dwell time at each assessment of the deviations for each Field Strength test point should be at least 0.5 second. application. Frequency peak average (6) Data Submittal: An (V/M) V/M (5) Test Methods and Procedures: RTCA document DO–160C, Section 20, accomplishment report should be 10 KHz-500 KHz ...... 60 60 provides information on acceptable test submitted to the Aviation Register 500 KHz-2 MHz ...... 80 80 procedures. In addition, the following showing fulfillment of the HIRF energy 2 MHz-30 MHz ...... 200 200 information on modulation is presented protection requirements. This report 30 MHz-100 MHz ...... 33 33 to supplement that found in DO–160C. should contain test results, analysis and 100 MHz-200 MHz .... 150 33 other pertinent data. 200 MHz-400 MHz .... 56 33 Equipment and subsystem radiated 400 MHz-1 GHz ...... 4,020 935 susceptibility qualification tests should (7) Maintenance Requirements: The 1 GHz-2 GHz ...... 7,850 1,750 be conducted by slowly scanning the applicant (manufacturer) must provide 2 GHz-4 GHz ...... 6,000 1,150 entire frequency spectrum with an maintenance requirements to assure the 4 GHz-6 GHz ...... 6,800 310 unmodulated signal which produces the continued airworthiness of the installed 6 GHz-8 GHz ...... 3,600 666 required average electric field strength system(s). 8 GHz-12 GHz ...... 5,100 1,270 as the equipment under test (EUT) and 12 GHz-18 GHz ...... 3,500 551 its wiring. A peak level detector should Issued in Renton, Washington, on 18 GHz-40 GHz ...... 2,400 750 be used to monitor the peak values of December 16, 1997. the signal and these values should be Gilbert L. Thompson, or, recorded at each test point. The EUT Assistant Manager, Transport Airplane (2) The applicant may demonstrate by should not be damaged by this test and Directorate, Aircraft Certification Service, laboratory test that the critical systems should operate normally for frequencies ANM–101. elements and their associated wiring under 400 MHz. Deviations from normal [FR Doc. 98–865 Filed 1–20–98; 8:45 am] harnesses can withstand a peak operation for test frequencies above 400 BILLING CODE 4910±13±P