All Older Boeings 737-300, -400, and -500 Are Under Emergency Fuselage Inspection

FAA issues airworthiness directive for Boeing Model 737-300, -400, and -500 series airplanes.

FAA emite diretriz de aeronavegabilidade para modelos de aviões Boeing séries 737-300, -400 e -500.

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• Airworthiness Directive 2011-08-51 FAA Diretriz de Aeronavegbilidade

Data: 05 ABRIL 2011

Diretriz de Aeronavegabilidade

Esta emergência foi resultada de um relatório indicando que um Modelo de  Boeing série 737-300, matrícula N632SW, experimentou uma descompressão rápida quando uma junção na cobertura do teto na corda S-4L entre a estação (BS) 664 e BS 727 rachou e abriu. A investigação mostrou que a rachadura foi localizada na superfície inferior da fileira de fixadores. A aeronave tinha acumulado 39.781 ciclos totais de voo e 48.740 horas totais de voo. Esta condição, se não corrigida, poderia resultar numa descompressão descontrolada no avião. Devido à junção na cobertura e a configuração do rasgão ser o mesmo nos modelos de Boeing das séries 737-400 e -500, estas aeronaves podem estar sujeitas à condição da insegurança identificada.

The Southwest Airlines jet forced to land last week after a gash opened in its fuselage had made an average of seven flights a day over its 15 years of service - a demanding schedule for any jetliner.

O avião da Southwest Linhas Aéreas forçado a pousar na última semana após um talho aberto na sua fuselagem tinha feito uma média de sete vôos por dia durante seus 15 anos de serviço – um programa de demanda para qualquer jato de linha aérea.

Federal Aviation Administration officials disclosed Tuesday that the Boeing 737-300 had flown 48,740 hours over its lifetime and gone through 39,781 flight cycles -- takeoffs and landings that tend to place the most stress on a plane's fuselage along with changes in cabin pressures.

Agentes da FAA revelaram na Terça-feira (5) que o Boeing 737-300 tinha voado 48.740 horas durante seu tempo de serviço e atingido 39.781 ciclos de vôo – decolagens e pousos que tendem a colocar o maior estresse na fuselagem do avião acompanhado de mudanças na pressão da cabine.

Aviation experts had initially speculated that the wear and tear Southwest planes typically endure - making an average of six flights per day - contributed to the incident. Southwest is the leading low-cost carrier in an industry that is highly competitive.

Especialistas em aviação tinham inicialmente especulado que o uso e o rasgão nos aviões que Southwest tipicamente sofreram – fazendo uma média de seis vôos por dia – contribuiu para o acidente. A Southwest é a líder de empresas aéreas de baixo-custo numa indústria que é altamente competitiva.

Flight 812, bound from Phoenix to Sacramento, had 118 passengers aboard when it made a safe emergency landing in Yuma, Ariz., Friday. There were no serious injuries.

After the incident, Southwest cancelled about 630 flights and inspected its 78 Boeing 737s, finding five others with fuselage cracks. The airline resumed normal flight operations Tuesday.

O Voo 812, saiu de Phoenix para Sacramento, tinha 118 passageiros a bordo quando ele fez um pouso de emergência em Yuma, Arizona, na Sexta-Feira (1). Não houve feridos graves.

Após o acidente, a Southwest cancelou cerca de 630 voos e inspecionou seus 78 Boeings 737s, encontrando cinco outros com rachaduras na fuselagem. A empresa aérea assumiu operações normais de vôo na Terça-feira (5).

Also on Tuesday, the FAA ordered all airlines to conduct detailed inspections within five days of older model Boeing 737-300s, 400s and 500s that have logged more than 35,000 flight cycles. The directive also requires airlines to check heavily-used 737s before they reach 30,000 cycles and orders that the older planes, which are mostly owned by Southwest, be re-inspected every 500 cycles.

Também na Terça-feira (5), a FAA ordenou a todas empresas de linhas aéreas a conduzir inspeções detalhadas dentro de cinco dias nos modelos antigos de Boeing 737-300, -400 e -500 que tenham acumulado mais que 35.000 ciclos de vôos. A diretriz também exige que as empresas verifiquem os Boeings 737 com uso pesado antes que eles atinjam 30.000 ciclos e ordena que os aviões mais velhos, os quais são principalmente pertencentes à Southwest, sejam re-inspecionados a cada 500 ciclos.

Paul Richter, chief project engineer for 737s at Boeing, said during a media briefing that the fatigue cracks suspected in the Southwest rupture occurred sooner than Boeing expected in the life of the plane. The company also issued a service order instructing airlines to check their planes.

Paul Richter, engenheiro chefe de projeto dos 737s na Boeing, disse durante uma explanação à mídia que a suspeitadas rachaduras por fadiga na ruptura do avião da Southwest ocorreram mais cedo do que o esperado na vida do avião. A companhia também emitiu uma ordem de serviço instruindo empresas aéreas  verificarem seus aviões.

FAA officials estimate that about 175 planes will be affected worldwide, including 80 in the United States. Domestic airlines must comply with the directive, whereas foreign carriers often honor the orders voluntarily.

Agentes da FAA estimam que cerca de 175 aviões serão afetados mundialmente, incluindo 80 nos Estados Unidos. Empresas de Linhas Aéreas Domésticas devem sujeitar-se à diretriz, enquanto empresas estrangeiras frequentemente honram as ordens voluntariamente.

Southwest Airlines Flight 812, a Boeing 737 carrying about 118 people out of Phoenix for Sacramento, Friday, diverted to Yuma Marine Corps air station in Arizona after an in-flight fuselage rupture caused rapid decompression at 36,000 feet. Passengers who called in to local news stations said a six foot long gash opened with a loud bang in the top of the cabin. They said the sky was visible through the opening and that some passengers lost consciousness during the rapid descent to 11,000 feet. According to Southwest, a flight attendant was the only one aboard to have suffered an injury. One passenger who saw the flight attendant speculated that the crewmember may have broken his nose. The NTSB has sent a Go Team to investigate the fuselage rupture.

Southwest Airlines Voo 812, um Boeing 737 carregando cerca de 118 pessoas de Phoenix para Sacramento, na Sexta-feira (1) alternou para estação aérea Yuma Marine Corps, no Arizona após uma ruptura da fuselagem em voo causando descompressão rápida a 36.000 pés. Passageiros que foram entrevistados por telefone pelas emissoras de notícia disseram que um talho abriu com 1,80 m com um estrondo antes no topo da cabine. Eles disseram que o céu estava visível através da abertura e que alguns passageiros perderam a consciência durante a descida rápida para 11.000 pés. De acordo com a Southwest, uma comissária de voo foi a única a bordo a sofrer ferimento. Um passageiro que viu a comissária de voo, especulou que a comissária pode ter quebrado seu nariz.

Have You Been Confident of Corrosion Has Been Kept From Your Plane?

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"We want to make airplanes that fly like birds," said Fu-Kuo Chang, a scientist at Stanford University who developed the sensors and co-authored a recent article about the technology in the journal, Advanced Materials. "Aircraft that have all the sensing information about what is happening around them, just like birds do."

Aircraft could soon be covered in new technological cobwebs. Inspired by the gossamer strands of spider webs, scientists from Stanford University have created an ultra-fine mesh of strain and temperature sensors.

Wrapped around an aircraft, the sensors could help craft monitor their internal well-being. This added awareness could prevent microscopic cracks from developing into catastrophic failures. Beyond aircraft, the new technology could create a new breed of intelligent automobiles, packaging and medical devices.

Aircraft and birds both have various ways to sense their environment. Birds have eyes to see, ears to hear and mouths to speak (or sing). Aircraft have their own versions of these organs, such as radar, which gathers information about the physical environment, and radio, which allows them to communicate.

But aircraft lack nerves. Unlike birds, they don't have a way to sense tiny changes inside their bodies. For instance, a bird in a dive can sense, through its nerves and other tissues, whether the strain is too great and if they need to pull up before their bones break.

The new spider web-inspired mesh would give aircraft two new senses birds have had for millions of years: strain and temperature. The new mesh contains tiny structures that can, say, measure the temperature along the entire body of the aircraft, or map the air pressure flowing around a wing.

The new sensor is a plastic polymer that has the gold sensors laid down on top of it, which monitor the skin of the aircraft. The Stanford scientists are already developing technology that will allow pilots to image the interior of their aircraft similar to the way pregnant women can see their unborn children.

By adding ultrasonic wave-inducing piezoelectric devices, pilots could constantly scan the aircraft to discover, say, microscopic cracks in the supports long before they developed into life-threatening failures.

"This will help ensure the safety of air transportation," said Frank Chang, a scientist at the University of California, Los Angeles who is familiar with the research but is not involved in it.

To paper an entire aircraft with sensors would ordinarily add significant weight, and therefore require more fuel, something airlines are anxious to avoid. To get around this problem the California scientists stripped the sensors down to the bare minimum of material, eliminating 99.7 percent of it.

Spider web-like sensors that can detect touch and temperature in aircraft are just the beginning, say the scientists. The new sensors could eventually lead to smarter cars, wound dressings that tell doctors how quickly a patient is healing, shirts that allow pregnant women to see their unborn child whenever they want, or even synthetic skin for robots.

"This will have very extensive usage and importance," besides just aircraft, said UCLA's Chang.

CAUSES OF CORROSION

Corrosion is the destruction of metal by electrochemical reaction with its environment. Figure 1 illustrates some typical sources of the corrosion that affects airplanes. As shown in figure, three conditions must exist simultaneously for corrosion to take place:

The presence of an anode and a cathode. This occurs when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential.

A metallic connector between the anode and cathode.

An electrolyte such as water.

Eliminating these three conditions in airplanes is restricted by practicality, functionality, and feasibility. Dissimilar metal contact cannot always be avoided because of weight, cost, and functional issues, but the potential for corrosion can be minimized by using surface treatments, plating, painting, and sealing. Water cannot be avoided, but it can be controlled with drain paths, drain holes, sealants, and corrosion-inhibiting compounds. Controlling the presence of water is usually the most effective means of preventing corrosion

Two of the most destructive forms of corrosion are stress corrosion cracking (SCC), also known as environmental assisted stress corrosion, and exfoliation corrosion. SCC occurs rapidly and follows the grain boundaries in aluminum alloys. Exfoliation corrosion also follows grain boundaries. It occurs in multiple planes, causing a leaf-like separation of the metal grain structure. Both forms of corrosion cause a loss of load-carrying capability. The most effective way to control this kind of corrosion is to use materials that are not susceptible to SCC at design stress levels or have a grain structure that is not susceptible to exfoliation.

An increasing number of operators are now providing ETOPS service to their passengers. For example, 76 percent of 767 operators and 42 percent of 757 operators are flying ETOPS routes. Several operators have discovered that the cost of ETOPS maintenance, compared to its benefits, also offers them a significant cost advantage when flying their non-ETOPS routes and when operating their non-ETOPS airplanes.

REFERENCE

DAVID BANIS
ENGINEER
MATERIALS TECHNOLOGY
BOEING COMMERCIAL AIRPLANES GROUP


J. ARTHUR MARCEAU
ENGINEER (RETIRED)
MATERIALS TECHNOLOGY
BOEING COMMERCIAL AIRPLANES GROUP


MICHAEL MOHAGHEGH
ENGINEER
STRUCTURES ENGINEERING
BOEING COMMERCIAL AIRPLANES GROUP


HARRY KINNISON, PH.D.
ETOPS MAINTENANCE PROGRAMS
MAINTENANCE AND GROUND OPERATIONS SYSTEMS
BOEING COMMERCIAL AIRPLANES GROUP

Aircraft Dents and Cracks - Maintenance with sensors

Energy-autonomous Sensors Find Dents And Cracks In Aircraft

Aircraft maintenance will be easier in future, with sensors monitoring the aircraft skin. If they discover any dents or cracks they will send a radio message to a monitoring unit. The energy needed for this will be obtained from temperature differences.

Sensores autônomos de energia  descobrem mossas e rachaduras em aeronaves

Manutenção de aeronaves será mais fácil no futuro, com sensores monitorando a fuselagem da aeronave. Se eles descobrem quaisquer mossas ou rachaduras, eles enviarão uma mensagem por rádio para a unidade monitora. A energia necessária para isto será obtida da diferença de temperaturas.

If a bird collides with a plane the consequences can be fatal, not only for the creature itself. The impact can deform the structure of the aircraft fuselage, causing stresses in the material which can later turn into cracks. In future, sensors in the aircraft skin will detect such damage at an early stage and simplify maintenance and repair work. The sensors are light - they don’t need any cables or batteries. They draw their energy from the temperature difference between the outside air (about minus 20 to minus 50 degrees Celsius) and the passenger cabin (about 20 degrees Celsius). Because there are no batteries to change, the sensors can be located at inaccessible places on the aircraft.

Se um pássaro colide com um avião as consequencias podem ser fatais, não somente para a criatura em si. O impacto pode deformar a estrutura da fuselagem da eronave, causando stress no material o qual pode mais tarde virar rachaduras. No futuro, sensores na fuselagem da aeronave detectarão tais avarias num estágio prévio e simplificará a manutenção e trabalho de reparo. Os sensores são luzes - elas não precisam de qualquer cabo [fios] ou baterias. Elas retirarão sua energia da diferença de temperatura entre o ar externo (cerca de -20ºC a - 50ºC) e a cabine de passageiros (cerca de +20ºC). Por causa de não haver baterias a carregar, os sensores podem ser localizados em lugares inacessíveis na aeronave.

 

The applications for energy-autonomous sensors are numerous. In automobiles they could help to reduce weight by removing the need for heavy cable assemblies. They would also be useful in old buildings, where they could be easily affixed to walls e.g. to monitor dampness. Their use in the medical sector is feasible too. A sensor system integrated in a running shirt could monitor an athlete’s pulse during training, and hearing aids could obtain their energy from body heat.

 

As aplicações para sensores autônomos de energia são numerosas. Em automóveis eles poderiam ajudar reduzir peso pela remoção da necessidade de cabos pesados na montagem. Eles também seriam úteis em prédios antigos, onde eles poderiam ser facilmente afixados nas paredes para monitorar umidade.

O uso deles no setor médico é viável também. Um sistema de sensor integrado numa camiseta poderia monitorar a pulsação do atleta durante os exercícios físicos e aparelhos de audição poderiam obter suas energias do calor do corpo.

 

Texto original em inglês  Fraunhofer