ITA Instituto Tecnológico de Aeronáutica Cargas em Aviões Introdução
Objetivos do Projeto Estrutural O trabalho de rimeira imortância ara o rojetista de estruturas de aviões é o de rojetar uma estrutura com resistência e rigide adequadas ara as condições mais severas revistas no uso do avião, dando atenção aos seguintes ontos: minimiação do eso; comatibiliação das restrições aerodinâmicas com maximiação do esaço interno; redução dos custos de rodução; facilidade e baixo custo de manutenção; adequação na escolha dos materiais utiliados.
Requisitos Estruturais Resistência cargas máximas fadiga Rigide freqüências naturais aeroelasticidade
Aircraft Loads AIRLOADS - maneuver - gust - control deflection - comonent interaction - buffet INERTIA LOADS - due to accelerations POWER PLANT LOADS - thrust - torque - gyroscoic - vibration - duct ressure LANDING LOADS - vertical load factor - sin-u - sring-back - one wheel -braking TAKEOFF LOADS - catault TAXI LOADS - bums - turns OTHER LOADS -towing - jacking - ressuriation - crash landing
Cargas em Aviões Carga Limite carga máxima revista em condições normais de oeração Carga Final (ou Última) carga limite x fator de segurança
Requisitos 1) a estrutura do avião deve resistir às cargas limites sem aresentar deformação ermanente rejudicial; 2) A estrutura do avião deve resistir às cargas finais sem falhas.
Imlicações no Projeto * Carga Limite escoamento * Carga Última falha
Margens de Segurança a) Na condição limite MS carga de escoamento carga limite 1 b) Na condição última MS carga de falha carga última 1
Regulamentos Autoridades resonsáveis ela homologação estabelecem: Exigências de aeronavegabilidade. Requisitos de segurança.
Regulamentos USA Federal Aviation Regulations (FAR), emitidos ela Federal Aviation Agency (FAA) EUR Joint Aviation Regulations (JAR)
FAR 23 Airlane Categories (a). The normal category is limited to airlanes that have a seating configuration, excluding ilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 ounds or less, and intended for nonacrobatic oeration. Nonacrobatic oeration includes: (1). Any maneuver incident to normal flying; (2). Stalls (excet whi stalls); and (3). Lay eights, chandelles, and stee turns, in which the angle of bank is not more than 60 degrees.
FAR 23 Airlane Categories (b). The utility category is limited to airlanes that have a seating configuration, excluding ilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 ounds or less, and intended for limited acrobatic oeration. Airlanes certificated in the utility category may be used in any of the oerations covered under aragrah (a) of this section and in limited acrobatic oerations. Limited acrobatic oeration includes: (1). Sins (if aroved for the articular tye of airlane); and (2). Lay eights, chandelles, and stee turns, or similar maneuvers, in which the angle of bank is more than 60 degrees but not more than 90 degrees.
The commuter category oeration is limited to any maneuver incident to normal flying, stalls (excet whi stalls), and stee turns, in which the angle of bank is not more than 60 degrees. FAR 23 Airlane Categories (c). The acrobatic category is limited to airlanes that have a seating configuration, excluding ilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 ounds or less, and intended for use without restrictions, other than those shown to be necessary as a result of required flight tests. (d). The commuter category is limited to roeller-driven, multiengine airlanes that have a seating configuration, excluding ilot seats, of 19 or less, and a maximum certificated takeoff weight of 19,000 ounds or less.
FAR 23 Airlane Categories (e). Excet for commuter category, airlanes may be tye certificated in more than one category if the requirements of each requested category are met.
FAR 25 AIRWORTHINESS STANDARDS TRANSPORT CATEGORY AIRPLANES (JAR 25 - Large Aerolanes) Categoria transorte aviões esecificamente destinados ao transorte regular de assageiros e de cargas.
FAR 25 Subart C Structure
(c). If deflections under load would significantly change the distribution of external or internal loads, this redistribution must be taken into account. 25.301 - Loads. (a). Strength requirements are secified in terms of limit loads (the maximum loads to be exected in service) and ultimate loads (limit loads multilied by rescribed factors of safety). Unless otherwise rovided, rescribed loads are limit loads. (b). Unless otherwise rovided, the secified air, ground, and water loads must be laced in equilibrium with inertia forces, considering each item of mass in the airlane. These loads must be distributed to conservatively aroximate or closely reresent actual conditions. Methods used to determine load intensities and distribution must be validated by flight load measurement unless the methods used for determining those loading conditions are shown to be reliable.
25.303 - Factor of safety. Unless otherwise secified, a factor of safety of 1.5 must be alied to the rescribed limit load which are considered external loads on the structure. When a loading condition is rescribed in terms of ultimate loads, a factor of safety need not be alied unless otherwise secified.
25.305 - Strength and deformation. (a). The structure must be able to suort limit loads without any detrimental ermanent deformation. At any load u to limit loads, the deformation may not interfere with safe oeration. (b). The structure must be able to suort ultimate loads without failure for at least 3 seconds. However, when roof of strength is shown by dynamic tests simulating actual load conditions, the 3-second limit does not aly. Static tests conducted to ultimate load must include the ultimate deflections and ultimate deformation induced by the loading. When analytical methods are used to show comliance with the ultimate load strength requirements, it must be shown that- (1). The effects of deformation are not significant; (2). The deformations involved are fully accounted for in the analysis; or (3). The methods and assumtions used are sufficient to cover the effects of these deformations.
25.305 - Strength and deformation. (c). Where structural flexibility is such that any rate of load alication likely to occur in the oerating conditions might roduce transient stresses areciably higher than those corresonding to static loads, the effects of this rate of alication must be considered. (d). Reserved (e). The airlane must be designed to withstand any vibration and buffeting that might occur in any likely oerating condition u to V D /M D, including stall and robable inadvertent excursions beyond the boundaries of the buffet onset enveloe. This must be shown by analysis, flight tests, or other tests found necessary by the Administrator. (f). Unless shown to be extremely imrobable, the airlane must be designed to withstand any forced structural vibration resulting from any failure, malfunction or adverse condition in the flight control system. These must be considered limit loads and must be investigated at airseeds u to V C /M C.
25.307 - Proof of structure. (a). Comliance with the strength and deformation requirements of this subart must be shown for each critical loading condition. Structural analysis may be used only if the structure conforms to that for which exerience has shown this method to be reliable. The Administrator may require ultimate load tests in cases where limit load tests may be inadequate. (b). [Reserved] (c). [Reserved] (d). When static or dynamic tests are used to show comliance with the requirements of 25.305(b) for flight structures, aroriate material correction factors must be alied to the test results, unless the structure, or art thereof, being tested has features such that a number of elements contribute to the total strength of the structure and the failure of one element results in the redistribution of the load through alternate load aths.
Critical Conditions L1011
Critical Conditions Tyical Fighter
Eixos de Referência Eixos do avião: utiliados na análise estrutural.
Cargas de Inércia e Fator de Carga g a W F n a g W W F a a + + 1 g a W F F n a g W F F x xa x x xa Vôo Nivelado
Cargas de Inércia e Fator de Carga Vôo não Nivelado ( ) θ θ cos cos + + g a W W a g W W F n a ( ) θ θ sen g a W Wsen a g W W F F n x x xa x
Cargas de Inércia e Fator de Carga Caso Geral n j ( F ) ( F ) e j W W i j ( ) F e j Somatório das forças externas na direção j (excluídas todas e quaisquer forças de inércia) ( ) F i j Somatório das forças de inércia na direção j (incluídas as comonentes do eso)
Cargas de Inércia e Fator de Carga Vôo em Arfagem Acelerada θ& &
Cargas de Inércia e Fator de Carga Fator de carga na resença de aceleração de arfagem ( W ) g r & θ θ ( W ) g & θ r cosθ ( W ) x && θ g x ( W ) n ( W ) θ& & g ( W ) n CG & θ θ r ( Fi ) n W + W x & θ g x ( F ) nx W W i x x & θ g
Cargas de Inércia e Fator de Carga Fator de carga na resença de aceleração de arfagem ( Fi ) n W + W x & θ g ( n ) ( F ) i W n θ & g x ( Fi ) nx W W x & θ g ( n ) x ( F ) i x W n θ + & g
Exemlo 1 Determinar as forças atuantes sobre o iloto: CG 5 Distâncias em mm Peso do iloto: 760N Peso do avião: 445.000N I y 4,52x10 6 Kg.m 2
Exemlo 1 Fatores de Carga no CG W 445.000N V 1,335 10 6 N H 4,41 10 5 N n W V 1,335 10 445000 6 3,000 n x W H 4,41 10 4,45 10 5 5 0,991
Aceleração de Arfagem Aceleração de Arfagem M y Vx V H H I V 1,335 10 H 4,41 10 x y V H 4,52 10 2,13m 3,05m 6 6 5 Kg. m N N 6 ( 3,05) 4,186 10 Nm 6 5 1,335 10 2,13 4,41 10 2 M y 6 M y 4,186 10 N. m + I && yθ 0 & θ 0,927rad / s 6 2 I 4,52 10 Kg. m y 2
Fatores de Carga e Forças no Piloto n nx 0,991 & θ 0,927rad / x 3,000 9,45m 1,00m ( W ) 760N s 2 ( ) n ( ) n x Fatores de Carga no Piloto P P ( 0,927) ( 9,45) 2, 107 3,000 9,81 ( 0,927) 0,991+ 1,00 0,897 9,81 Forças no Piloto ( F ) ( W ) ( n ) 760 2,107 1.601 N ( F ) ( W ) ( n ) 760 0,897 682 N x x (ara trás) (ara cima)