Pilot Age and Porformance - Johns Hopkins research

ENGLISH PORTUGUÊS

1º - Experienced Pilots May Be At Risk Of DNA Damage From Ionizing Radiation

1º - Pilotos Experientes Podem Estar em Risco de Danos de DNA por Radiação Ionizada

2º - An airplane pilot's experience is a better indication of crash risk than his or her age, Johns Hopkins researchers say.

2º - Uma prática de piloto de avião é uma melhor indicação de risco de acidente aéreo do que a idade dele ou dela, pesquisadores da Johns Hopkins dizem.

Published on DEC 12, 2008

Publicado em 12 DEZEMBRO 2008
http://www.bma.org.uk/

The finding was published in the British Medical Journal ahead of print in the journal Environmental Medicine.

A descoberta foi publicada no Jornal Britânico de Medicina antes de imprimir no jornal de Medicina Ambiental.

Airline pilots who have flown for many years may be at risk of DNA damage from prolonged exposure to cosmic ionising radiation, suggests a study published ahead of print in Occupational and Environmental Medicine.

Pilotos de Linha Aérea que tem voado por muitos anos podem estar em risco de danos aos DNA por prolongada exposição à radiação cósmica ionizada, sugere um estudo publicado antes da impressão no Medicina do Trabalho e Ambiental.

The research team compared the rate of chromosomal (DNA) abnormalities in blood samples taken from 83 airline pilots and 50 university faculty members from the same US city.

A equipe de pesquisa comparou a taxa de anormalidade cromossomial em amostras de sangue tomada de 83 pilotos de linha aérea e de 50 membros de faculdade da universidade da mesma cidade nos USA.

The two groups were matched for age (35 to 56), sex (male), and smoking habit (light or non-smokers). Age and smoking are known risk factors for cumulative DNA damage.

Os dois grupos foram equiparados pela idade (35 a 56) sexo (masculino) e fumante ( leve ou não fumante). A idade e fumante são fatores de risco conhecidos para cumulativos danos ao DNA.

Fifty eight of the pilots (70%) had served in the military, and they had undertaken significantly more personal air travel than the university staff. Both these factors would have exposed them to more ionising radiation.

58 dos pilotos (70%) tinham trabalhado no milatarismo e eles tinham se incumbido significantemente de mais viagens aéreas pessoais do que o grupo da universidade. Ambos estes fatores teriam os exposto a mais radiação ionizada.

The researchers were looking in particular for the number of times pairs of chromosomes had changed places (translocations), expressed as a score per 100 cell equivalents (CE).

As pesquisas foram vistas em particular para o número de vezes que os pares de cromossomos tinham mudados de locais (transposição), explicitados com uma contagem de 100 células equivalentes (CE).

Chromosome translocations are a reliable indicator of cumulative DNA damage associated with radiation exposure as they are not rapidly eliminated from the blood like other forms of chromosomal abnormality.

As transposições cromossômicas são um indicador confiável de danos cumulativos ao DNA associado a exposição à radiação quando eles não são rapidamente eliminados do sangue como outras formas de anormalidade cromossomial.

The average frequency of chromosome translocation was higher among the pilots than the faculty staff (0.39 compared with 0.32/100 CE), but after adjusting for age and other influential factors, there was no difference.

A frequência média de transposição de cromossomos foi mais alta entre os pilotos do que nos funcionários da universidade (0.39 comparados com 0.32/100 CE), mas após o ajuste de idade e outros fatores de influência, não houve diferença.

But when the analysis focused on how long pilots had been flying, differences emerged.

Mas quando a análise focou em quanto tempo pilotos tinham estado voando, as diferenças surgiram.

The chromosome translocation frequency of those who had flown the most was more than twice that of those who had flown the least, after taking age into account.

A frequência de transposição cromossômica daqueles que tinha voado mais foi mais do que duas vezes que daqueles que tinham voando a menos, após levar a idade em conta.

Adjusting for the impact of cigarette smoking, personal air travel, and diagnostic x-ray procedures did not affect these findings.

Ajustando para o impacto de fumantes de cigarros, viagem aérea pessoal e procedimentos de diagnóstico por Raio-X não afetou estas descobertas.

Chromosomal abnormalities have been associated with an increased risk of cancer. And the authors conclude that their results suggest that highly experienced flight pilots may be exposed to "biologically significant doses of ionising radiation."

Anormalidades cromossomiais tem sido associadas com um aumento de risco de cancer. E os autores concluem que seus resultados sugerem que pilotos de vôo altamente experientes podem ser expostos a "doses biologicamente significantes de radiação ionizada".

Radiation is everywhere. It's been part of our environment since the planet was born. Radiation exists in the atmosphere, the ground, the water and even within our own bodies. It's called natural background radiation, and it's perfectly safe.

Radiação está em todo lugar. Ela tem sido parte de nosso ambiente desde que o planeta nasceu. Radiação existe na atmosfera, no solo, na água e mesmo dentro de nossos corpos. Ela é chamada Radiação de fundo natural e ela é perfeitamente segura.

Radiation is the transfer of energy from a source. It may be in the form of electromagnetic radiation such as x-rays and gamma rays. It may also be in the form of particles such as neutrons and protons.

Radiação é a tranferência de energia de uma fonte. Ela pode ser na forma de radiação eletromagnética tal como Raios-X e raios Gama. Ela pode ser também na forma de partículas tais como Neutrons e Protons.

Cosmic radiation is the collective term for the radiation which comes from the Sun and from the galaxies of the Universe (the galactic component). Cosmic radiation is ionising, i.e. it can displace charged particles from atoms. This can lead to the disruption of molecules in living cells. Processes in the cell repair most of this damage.

Radiação cósmica é o termo coletivo para radiação que vem do Sol e das galáxias do Universo, (a componente galática). Radiação cósmica é ionisante, isso é, ela pode deslocar partículas carregadas dos átomos. Isto pode conduzir ao rompimento de moléculas em células vivas.O
processamento na célula, repara muitos deste dano.

Ionizing radiation is energy in the form of particles or waves.
However, ionizing radiation is so high in energy it can break chemical bonds - meaning it can charge (or ionize) an atom that interacts with it. At a lower energy, it may strip off a couple of electrons. At a higher energy, it can destroy the nucleus of an atom. This means that when ionizing radiation passes through the tissues of the body, it actually has enough energy to damage DNA. It's why gamma rays, for example, are good at killing cancer cells through radiation treatment.

Radiação de ionização é a forma de energia de particulas ou ondas.Entretanto, radiação de ionização é tão alta em energia que ela pode quebrar ligações químicas - significando que ela pode carrregar [elétricamente] (ou ionizar) um átomo que interage com ela. Num [nível] mais baixo de energia, ela pode tirar um par de elétrons. Num [nível] mais alto de energia, ela pode destruir o núcleo do átomo. Isto significa que quando radiação de ionização passa através dos tecidos do
corpo, ela realmente tem energia suficiente para danificar o DNA. É porque os raios Gama, por exemplo, são bons para matar células cancerígenas através de tratamento por radiação.

Ionising radiation is measured in terms of absorbed dose, the energy deposited per unit mass. Equal absorbed doses of different types of radiation cause biological effects of different magnitudes, and thesensitivity of different tissues of the body differ. To account for this, tissue absorbed doses are multiplied by radiation weighting factors to give equivalent doses, and by tissue weighting factors to give the effective dose in sieverts (Sv) to the whole body.

Radiação ionizante é medida em temos de dose absorvida, a energia depositada por unidade de massa. Iguais doses absorvidas de deferentes tipos de radiação causam efeitos biológicos de diferentes magnitudes e a sensibilidade de diferentes tecidos do corpo diferem. Para calcular
isto, io tecido com doses absorvidas é multiplicado pelos fatores de peso de radiação para dar doses equivalentes, e por fatores de peso para dar a dose efetiva em Sieverts (Sv)para o corpo todo.

Aircraft capable of operating at altitudes greater than 15 km (49,000 feet) should carry an active radiationmonitor, which monitors current levels of radiation, to detect any significant short-term variation in radiation levels during flight.

Aeronaves capazes de operar em altitudes maiors que 49000 pés (15 Km) devem carregar um radiomonitor ativo, o qual monitora niveis atuais de radiação, para detectar qualquer significante variação de curto periodo em níveis de radiação durante o voo.

Air crew operating such high flying aircraft should be subject to the same general monitoring regime as for those operating between 8 and 15 km but account should be taken of the greater potential variability ofdose. Active monitoring may be used to assess the doses to which air
crew are exposed (rather than using a computer program to predict dose) or simply to provide a warning of high dose rates.

Tripulação de voo operando avião de voos altos, deve ser submetida ao mesmo regime de monitoramento geral bem como para aquelas operações entre 26000 pés (8 Km) e 49000 pés (15 Km), mas a conta deve ser tomada da maior variabilidade potencial da dose. Monitoramento ativo pode ser usado para avaliar as doses para as quais a tripulação de voo está exposta (de preferência usando um programa de computador para prever a dose) ou simplesmente fornecer um alerta de taxas de alta dose.

The concentration of ozone (triatomic oxygen, O3) and the intensity of cosmic radiation both increase with altitude. Ozone is easily converted to oxygen by heat and various catalytic processes. In modern jet aircraft, almost all ozone in the ambient air is converted to oxygen in
the compressors that provide pressurized air for the cabin.

A concentração de Ozônio (Oxigênio triatômico O3) e a intensidade de radiação cosmica ambas aumentam com a altitude. Ozônio pe facilmente convertido em Oxigênio pelo aquecimento e varios processos catalíticos.Nas moderanas aeronaves à jato, quase todo Ozônio no ambiente aéreo é convertido em Oxígênio nos compressores que fornecem ar pressurizado
para cabine.

During descent, when engine power is low, a build-up of ozone is prevented by catalytic converters. At usual cruising altitudes, the concentration of ozone in the cabin air is negligible. Cosmic radiation is the sum of solar and galactic radiation. At aviation altitudes, the cosmic ray field consists of high energy-ionizing radiation and neutrons. The atmosphere and the earth’s magnetic field are natural shields. Because of the orientation of the magnetic field and the
“flattening” of the atmosphere over the North and South Poles, the cosmic radiation levels are significantly higher at polar than at equatorial latitudes. The intensity of cosmic radiation levels
increases with altitude and dose rates of 1 – 3 microSv/hour on short haul and 5microSv/hour on long haul rotes are typical. For comparison, the natural background radiation from soil, water and building materials is about 2microSv per year in most countries.

Durante a descida, quando a potência do motor é baixa, uma maior formação de Ozônio é impedida pelos conversores catalíticos. Em altitudes de cruzeiro usuais, a concentração de Ozônio no ar da cabine é insignificante. Radiação cósmica é a soma de radiação solar e cosmica. Em altitudes de aviação, o campo de raios cósmicos consiste de radiação de alta energia de ionização e neutros. A atmosfera e o campo magnético da Terra são escudos naturais. Por causa da orientação do campo magnético da Terra e o "achatamento" da atmosfera sobre os polos Norte e Sul, os níveis de radiação cósmica são significante mais altos em latitudes polar que em altitudes equatoriais. A intensidade dos níveis de radição cósmica aumenta com a altitude e dosa taxas de 1 a 3 microSv/hora em rotas de curta distância e 5 microSv/hora em longa distância são tipicas. Para comparação, a radiação natural do solo, água e estruturas materiais é cerca de 2 microSv por ano em muitos paises.

The International Commission on Radiological Protection has set 1mSv per year as a basic safety standard for the protection of the health of the general public against the dangers arising from additional ionizing radiation.

A Comissão Internacional de Proteção Radiológica ajustou em 1 microSv por ano como o padrão básico de segurança para proteção da saúde do público em geral contra os perigos surgindo de adicional radiação de ionização.

Pilot Age and Performance

An airplane pilot's experience is a better indication of crash risk than his or her age, Johns Hopkins researchers say. They found in a study of 3,306 commuter plane pilots that those with more than 5,000 hours of flight experience had less than half the risk of a crash than less experienced counterparts.

Uma prática de pilotos de avião é a melhor indicação de risco de acidente aéreo do que sua idade, pesquisadores da Johns Hopkins Medical Institutions dizem. Eles descobriram num estudo de 3306 pilotos de aviões de vôos regionais que queles com mais de 5000 horas de experiÊncia de vôo tinham menos que a metada do risco de um acidente aéreo do que colegas experientes.

During the study period, the pilots flew 12.9 million flight hours and had 66 aviation crashes, yielding a crash rate of 5.1 per million pilot flight hours. Crash risk remained stable as the pilots aged from their late 40s to late 50s. One hundred and five study subjects died, 27 of whom were fatally injured in aviation crashes.

Durante o período de estudo, os pilotos voaram 12.9 milhões de horas de vôo e tiveram 66 acidentes aéreos, cedendo à taxa de acidente aéreo de 5.1 por milhão de horas de vôo como piloto. O risco de acidente aéreo permaneceu estável quando as idades dos pilotos avançaram dos 40 para os 50 anos. 105 (cento e cinco) submetidos ao estudo morreram, 27 deles foram feridos fatalmente em acidentes aéreos.

"Federal aviation regulations prohibit airline pilots from flying beyond the age of 60, but the relationship between pilot age and safety had never been rigorously assessed," says Guohua Li, M.D., Dr.P.H., lead author of the study and professor of emergency medicine and of health policy and management. "Performance in most flight-related tasks such as decision-making, tracking, takeoff and landing does not differ significantly between older and younger pilots. The lack of an association between pilot age and crash risk may reflect a strong healthy worker effect' from the rigorous medical standards and periodic physical examinations required for professional pilots."

"As regulamentações de aviação federal proibe pilotos de linhas aéreas de voarem além da idade de 60 anos, mas a relação entre idade de piloto e segurança nunca tinha sido rigorosamente avaliada", diz Guohua Li, M. D., Dr. P. H., autor principal do estudo e professor de medicina de emergência e de prática e administração de saúde. "Performance em muitas tarefas relacionadas ao vôo, tais como TOMADA DE DECISÃO, rotina, decolagem e pouso NÃO dieferem significantemente entre pilotos jovens e mais velhos. A falta de uma associação entre idade de piloto e risco de acidente pode ser reflexo dos rigorosos padrões médicos e exames físicos periódicos com forte efeito de trabalhador saudável requerido para pilotos profissionais".

Among the pilots studied by Li and colleagues, 99 percent were male and 69 percent were ages 45 to 49. On average, the pilots had 9,749 hours of total flight time and 287 flight hours in the six months prior to the start of the study. The majority of pilots (86 percent) did not have any health problems although 68 percent required corrective lenses for distant or near vision.

Entre os pilotos estudados por Li e colegas, 99 porcento eram homens e 69 porcento estavam com idade de 45 a 49 anos. Em média, os pilotos tinham 9749 horas totais de vôo e 287 horas de vôo nos 6 (seis) meses anteriores ao início do estudo. A maioria dos pilotos (86%) não tiveram qualquer problema de saúde embora 68 porcento usavam óculos de correção de visão para distante ou perto.

"Our study indicates that chronologic age by itself has little bearing on safety performance," says Susan P. Baker, co-author of the study and professor of health policy and management at Johns Hopkins' Bloomberg School of Public Health. "What really matters are age-related changes, such as health status and flight experience."

"Nosso estudo indica que idade cronológica por si só, tem pouco suporte sobre performance de segurança", diz Susan P. Baker, co-autora do estudo e professora de prática e administração de saúde na Johns Hopkins Bloomberg School of Public Healthy. "O que realmente importa são mudanças de idade relacionada, tais como estado de saúde e experiência de vôo".

Researchers tracked their exposure to flight and safety performance from 1987 to 1997, using records from the Federal Aviation Administration, the National Transportation Safety Board and the National Death Index as guidelines.

Os pesquisadores rastrearam exposições deles [pilotos] em vôo e performance de segurança, de 1987 a 1997, usando registros da Agência Federal de Aviação - FAA, o Conselho Nacional de Segurança de Transporte - NTSB e o Índice Nacional de Óbitos como diretriz.

Winglet for older Military Aircraft - Save Fuel

HISTORY OF WINGTIP DEVICES

Within a few years of the first heavier-than-air flight, the idea of beneficial wingtip devices was introduced. Lanchester patented the concept of awing end plate in 1897 and suggested that it would reduce wing drag at lowspeeds. Theoretical studies of end plates by Munk in 1921 were followedby studies of von Karman and Burgers and Mangler in the 1930s, a patenton nonplanar wings was granted to Cone in 1962, and a paper on the topic was published by Lundry and Lissaman in 1968. This work was paralleled by many experimental studies (see, for example, National Advisory Committeefor Aeronautics (NACA) work from 1928 to 1950 ), most of which did not attain the potential savings suggested by the theory. This was partly due to simplistic design, which often included low-aspect-ratio, untwisted, flat-plate airfoils. Recognition of the importance of winglet location, twist, and aspect ratio was clear in the patent of Vogt in 1951 and in a variety ofother nonplanar wingtip geometries studied and patented by Cone. In the early 1970s, Whitcomb10 of the National Aeronautics and Space Administration(NASA) defined and tested high-aspect-ratio, carefully designed nonplanar wingtips, termed “winglets,” which were soon to appear on numerous aircraft, including Rutan’s VariEze in 1975 and the Learjet 28/29in 1977. The winglet of the Boeing 747-400 has a much lower dihedral angle than the Whitcomb winglet, and since that time, numerous vertical,canted, and horizontal wingtip extensions have been put into commercialand military service.

M.M. Munk, 1921, “The minimum induced drag of aerofoils,” NACA Report 121.T. von Karman and J.M. Burgers, “General aerodynamic theory—perfect fluids,” InAerodynamic Theory, W.F. Durand, ed., Berlin/Vienna: Julius Springer-Verlag, 1934-1936,and New York: Dover Publications, 1963, Div. , Vol. II, pp. 216-221.W. Mangler, 1938, “The lift distribution of wings with end plates,” NACA TM 856;transl. by J. Vanier from “Die Auftriebsverteilung am Tragflügel mit Endscheiben,” Luftfahrtforschung14:64-569.C.D. Cone, Minimum Induced Drag Airfoil Body, U.S. Patent 3,270,988, September1966.J.L. Lundry and P.B.S. Llssaman, 1968, “A numerical solution for the minimuminduced drag of nonplanar wings,” Journal of Aircraft 5(1).Paul E. Hemke, 1928, “Drag of wings with end plates,” NACA TR-267.John M. Riebe and James M. Watson, 1950, “The effect of end plates on swept wingsat low speed,” NACA TN-2229.

Introduction to wingtip aerodynamics

Much of the drag of an aircraft is related to the lift generated by its wing. To create this lift, the wing pushes downward on the air it encounters and leaves behind a wake with a complex field of velocities. This air behind the wing moves downward then outward, while the air outboard of the wing tips moves upward, then inward, forming two large vortices.

The energy required to create this wake is reflected in the airplane’s“induced” or “vortex” drag. For most aircraft, induced drag constitutes a large fraction, typically 40 percent, of cruise drag. During takeoff, induced drag is even more significant, typically accounting for 80-90 percent of the aircraft’s climb drag. And while takeoff constitutes only a short portion of the flight, changes in aircraft performance at these conditions influence the overall design and so have an indirect, but powerful, effect on the aircraft’scruise performance. Consequently, concepts that reduce induced drag canhave significant effects on fuel consumption. 11 Richard Vogt, Twisted Wing Tip Fin for Airplanes, U.S. Patent 2,576,981, December 1951.C.D.

Cone, Minimum Induced Drag Airfoil Body, U.S. Patent 3,270,988, September1966. 10 Richard T. Whitcomb, 1976, “A design approach and selected wind-tunnel results athigh subsonic speeds for wing-tip mounted winglets,” NASA TN D-8260. 11 Ilan Kroo, 2005, “Nonplanar wing concepts for increased aircraft efficiency,” VKILecture Series on Innovative Configurations and Advanced Concepts for Future Civil Aircraft, June 6-10.

Since the 1970s, when the price of aviation fuel began to spiral upward, airlines and aircraft manufacturers have explored many ways to reduce fuel consumption by improving the operating efficiency of their aircraft. Fuel economy concerns have been particularly keen for operators of commercial aircraft, which typically fly many hours per day in competitive markets, but they have been growing for military aircraft as well. The fuel consumed by the U.S. Air Force is in excess of 3 billion gallons per year, which is over 8 million gallons per day. Aviation fuel accounts for much of this total, and the aircraft used by the Air Force for airlift, aerial refueling, and intelligence, surveillance, and reconnaissance (ISR) - which are the aircraft covered in this study - account for over half of all aviation fuel.

One very visible action taken by commercial airframe manufacturers and operators to reduce fuel consumption is the modification of an aircraft’s wingtip by installing, for example, near-vertical “winglets” to reduce aerodynamic drag. Experience shows that these tip devices reduce block fuel consumption (total fuel burn from engine start at the beginning of a flight to engine shutdown at the end of that flight) of the modified aircraft by Ron Sega, 2006, “Air Force energy strategy,” Worldwide Energy Conference and Trade Show, Arlington, Va., April 19.

Data provided by Defense Energy Support Center (DESC) on fuel usage by missiondesign series for FY05.

3-5 percent, depending on the trip length. These wingtip modifications are offered as options to the original design of many newer commercial jetliners but are also available for retrofit to selected older aircraft. To date, however, only one military-unique aircraft (the C-17 transport) features winglets, though some studies have been conducted on the feasibility of retrofitting tip modification devices on other military aircraft.In light of its growing concerns about rising fuel costs, the Air Force asked the National Research Council (NRC) to evaluate its aircraft inventory and to identify those aircraft that may be good candidates for winglet modifications. Specifically, the Air Force asked the NRC to perform the following four tasks:
1. Examine the feasibility of modifying Air Force airlift, aerial refueling,and ISR aircraft with winglets, to include a cost-effectiveness analysis of the feasible winglet modifications in net present value(NPV) terms.
2. Determine the market price of aviation fuel at which incorporating winglets would be beneficial for each platform.
3. Consider impacts to aircraft maintenance and flight operations(including ground operations).
4. Offer investment strategies the Air Force could implement with commercial partners to minimize Air Force capital investment and maximize investment return.

Although the statement of task above refers specifically to “winglets,”the Committee on Assessment of Aircraft Winglets for Large Aircraft Fuel Efficiency chose to broaden the scope of its deliberations slightly by including a variety of possible modifications to the wingtip (e.g., wingtip spanextensions). Thus, in this report, the term “winglet” denotes the traditional, nearly vertical wingtip design, while “wingtip modifications” is used to refer to the more general set of wingtip designs, including winglets and wingtip extensions, aimed at reducing aerodynamic drag.

These tasks call for a quantitative assessment of the costs and benefits of winglet modifications on a variety of platforms. In a comprehensive analysis, one would need to include the nonrecurring engineering costs of.

This range of 3-5 percent block fuel savings, derived from commercial experience, is lower than the 5-7 percent cited by the U.S. House of Representatives Armed Services Committeein Report 109-452, which may reflect fuel savings under cruise conditions.

Wing analysis and wingtip design, the costs of materials, manpower, and out-of-service time to accomplish the modification, financial implications, training costs, potential impacts on maintenance docks and hangar space, costs associated with software and technical manual revisions, and any impacts on maintenance, operations, or mission accomplishment.

Benefits to be considered would include not only improved fuel economy but also improved payload-range capability, improved takeoff performance, and less takeoff noise. In most cases, quantitative data on these costs and benefits were not known or not available. However, the committee did use preliminary NPV calculations to estimate payback periods for wingtip modification investments on various platforms by treating fuel costs, savings, and wing modification costs parametrically. These calculations supplemented the committee’s expert judgment on which platforms appear to be the best candidates for wingtip modification.

CANDIDATE AIRCRAFT IN THE Air force INVENTORY

Given the emphasis on fuel economy in the study’s statement of task, the committee began by considering those aircraft that consume the greatest amount of fuel. The five that stand out most clearly are, in order of annual fuel usage by fleet, the C-17, KC-135R/T,C-5, KC-10, and C-130H/J. The C-17 already has winglets, and the KC-135 and KC-10, which are closely related tothe Boeing707 and DC-10 commercial airframes, respectively, have been studied previously for wingtip modifications.

Besides wingtip devices, there are other methods to reduce aircraftfuel consumption, but since they were not mentioned in the statement of task, the committee did not examine them in detail, nor did it examine theextent to which the Air Force might already be using some of these methods.
Likewise, it did not make any formal recommendations concerning them.
However, the committee suggests this is an area that should be considered as potentially providing significant fuel savings to the Air Force.

Feasibility and Cost Effectiveness of Modifying Air Force Aircraft

Finding: The committee’s analysis for a broad range of fuel prices andwith the data available to it on potential improvements in block fuel savings, modification cost estimates, operational parameters for the aircraft, and so forth indicates that wingtip modifications offer significant potential for improved fuel economy in certain Air Force aircraft, particularly the KC-135R/T and the KC-10.

To assess the feasibility and cost-effectiveness of wingtip modifications, the committee began by investigating those aircraft in the Air Force inventory that burn the most fuel. In decreasing order of annual fuel burn (by fleet), they are the C-17, KC-135R/T, C-5, KC-10, and C-130H/J. Based on factors such as estimated fuel savings, cost of modification, operational flexibility, mission profiles, and remaining service life, the committee ranked these aircraft in order of their likely suitability for wingtip modifications.

Potential for Wingtip Modifications to Benefit Air Force Aircraft

Finding: Most of the aircraft in the Air Force inventory that derive from commercial aircraft now operating with winglets already have winglets, or the decision has been made to install winglets. The remaining AirForce aircraft that are derivatives of commercial aircraft do not appear to be good candidates for wingtip modifications.

Winglet Status of Air Force Aircraft Derived from Commercial Airframes

Air Force Aircraft Commercial Equivalent Inventory Winglets

COMMERCIAL EXPERIENCE

There are a number of very successful applications of winglets and wingtip extensions in the world’s commercial airplane fleet. These programs have been successful for a number of reasons, most notably because they have enhanced the economic value of the subject commercial airplanes. These wingtip device strategies have been employed both on new design aircraft and as post production retrofits on existing aircraft. The following is a summary of the strategies employed by the main commercial airframe manufacturers and two commercial airlines.

BENEFITS OF WINGTIP MODIFICATIONS

Reduced Fuel Burn

By reducing drag, wingtip devices help the aircraft operate more efficiently and, in turn, reduce fuel burn. The fuel savings benefits of wingtip modifications depend on the mission flight profile, particularly the range and time spent at cruise speed.

Commercial experience with winglet retrofits on the Boeing 737-300/700/800 indicate a 1.5 percent block fuel savings for trips of 250 nautical miles (nmi), increasing to 4 percent for trips of 2,000 nmi .15

For the Boeing 757-200 and 767-300, block fuel savings were 2 percent for 500 nmi trips and 6 percent for 6,000 nmi. On an annual basis, winglets were projected to result in savings to commercial operators of up to 130,000 gallons of fuel per aircraft on the 737-800 and up to 300,000 gallons per aircraft on the 757-200 .16 Reduced fuel consumption translates directly into a reduction in operating cost.

Increased Payload-Range Capability

If less fuel is required to accomplish a particular mission at a specific takeoff weight, then that credit can be realized in more than one way. For example, the aircraft can carry more weight (more payload) the same distance or it can carry the same payload farther (greater range). The increase in payload-range capability made possible by winglets on one commercial aircraft, the Boeing 737-800. The benefits begin to become apparent for ranges beyond 2,000 nmi. Between the 2,000 and 3,000 nmi range, winglets enable 80 nmi more range or 910 lb more payload. Beyond the 3,000 nmi range, winglets allow for 130 nmi more range or 5,800 lb more payload .17

In the commercial world, this capability translates into operational flexibility - for example, it offers a greater choice of aircraft along certain routes or the opening up of new routes and destinations that were not previously within range.

The increased payload-range capability is valued in military aircraft applications just as it is in commercial aircraft applications. Carrying more payload to the same distance could mean fewer sorties to accomplish a specific goal, or it could allow servicing more customers with the same number of operational aircraft.

Improved Takeoff Performance

The reduced drag associated with wingtip modifications reduces the thrust levels required for takeoff (reducing community noise at the sametime) and enables faster second-segment climb. This increased climb rate allows the use of airports having shorter runways and allows for operations from airports located at higher altitudes and in hotter climates. Alternatively, these advantages may be traded for carrying higher payloads or acombination of both.

Critical performance constraints for military aircraft can be dictated by either airfield constraints or a combat situation. For example, at an airfield in hostile territory, a steep climb out may be desired to reduce the time an aircraft is vulnerable to surface-to-air threat systems around the airfield.

Another example would be takeoff and landing constraints at a commercial airport where military tankers, airlift, or ISR platforms may also have tooperate.

Fuel Price Analysis

To illustrate the types of costs and benefits that might be realized through wingtip modifications (e.g., winglets) that would produce a reductionin fuel burn, the committee performed its own preliminary NPV analysis for the KC-135R/T and the KC-10. The analysis was used to determine whether wingtip modifications for selected aircraft would payfor themselves well before the aircraft are due to retire. Since it is not possibleto know the modification costs and fuel savings without performing adetailed engineering analysis, these were treated as parameters in the model.

The range for modification costs was chosen from list prices and committeeestimates. For fuel savings, the calculations were done for block fuel savingsof 3 percent and 5 percent, consistent with commercial airline experienceand the findings of this report. Results were calculated for the worst-case (highest modification cost and lowest fuel savings) and best-case (lowest modification cost and highest fuel savings) payback periods at a fuel costof $2.50 per gallon. The committee assumed an annual fuel cost escalation rate of 3 percent and a discount rate of 3 percent.In the KC-135R/T best case, net savings become positive 9 years after starting the modification program. All 417 aircraft in the inventory aremodified. Total net savings to the Air Force are approximately $400 million(FY07 $). In the KC-135R/T worst case, net savings become positive24 years after starting the modification program. Only 217 of the 417 aircraft in the inventory are modified (the others are not modified because they are expected to be retired from the inventory before reaching the end of their payback periods). Total net savings to the Air Force are approximately$36 million (FY07 $).

Impacts on Aircraft Maintenance and Flight Operations

Commercial experience with aircraft that have installed winglets has shown that there have been no significant impacts on aircraft maintenance, flight operations, or ground operations (gate space, taxiways, hangars, etc.).

Similarly, the Air Force has not experienced any significant impacts on aircraft maintenance or flight operations for aircraft it currently operateswith winglets, and the committee does not expect any major problems withmodifications to other aircraft under consideration.

Concluding remarks

It is clear that aerodynamic improvements, including winglets, can make significant contributions to the efficiency of aircraft and should be considered for the military fleets discussed in this report. In each case, however, the appropriateness of such structural modifications must be determined fleet by fleet. These decisions are very complex and will depend on many factors, including the design of the aircraft structures, design margin within those structures, the condition of the structures, mission profiles, utilization rates, fuel consumption rates, fuel prices, and the remaining life of the aircraft. The Air Force should support the analysis required and make the appropriate modifications as quickly as possible. There are also other ways to reduce fuel consumption, many of which have already been adopted by the commercial airlines. The committee believes it is important for these other strategies to be considered, and while they were not the focus of this study and the extent to which the Air Force may already be using some of these strategies was not examined.

Aeronautics and Transportation - NASA 51 Highest Priorities

Air transportation system is vital to the economic well-being and security of nations. To support continued U.S. leadership in aviation, Congress and NASA requested that the National Research Council undertake a decadal survey of civil aeronautics research and technology (R&T) priorities that would help NASA fulfill its responsibility to preserve U.S. leadership in aeronautics technology.

The United States is a leader in global aeronautics, and the National Aeronautics and Space Administration(NASA) has a critical role to play in preserving that position of leadership. NASA researchfacilities and expertise support research by other parts of the federal government and industry, and theresults of research conducted and/or sponsored by NASA are embodied in key elements of the U.S. airtransportation system, military aviation, and the space program. Maintaining a position of leadership inany field requires staying ahead of the competition by being the first to recognize and bridge each newgap into the future. This is generally a challenging task; were it not so, others would have overtaken theleader to set a faster pace. NASA aeronautics research can maintain a leadership position and carry onthis tradition as long as its research is properly prioritized and research tasks are executed with enoughdepth and vigor to produce meaningful results in a timely fashion.

OVERVIEW OF THE DECADAL SURVEY OF CIVIL AERONAUTICS

The Decadal Survey of Civil Aeronautics (NRC, 2006) presents a set of strategic objectives that thenext decade of research and technology development should strive to achieve. It also provides a set ofthe highest-priority R&T challenges- characterized by five common themes - and an analysis of keybarriers that must be overcome to reach the strategic objectives. The purpose of the Decadal Survey isto develop a foundation for the future - a decadal strategy for the federal government’s involvement incivil aeronautics, with a particular emphasis on NASA’s research portfolio.

The Decadal Survey of Civil Aeronautics also includes guidance on how federal resources allocated for aeronautics research should be distributed between in-house and external organizations, how aeronauticsresearch can take advantage of advances in crosscutting technology funded by federal agenciesand private industry, and how far along the development and technology readiness path federal agenciesshould advance key aeronautics technologies. It also provides a set of overall findings and recommendationsto provide a cumulative, integrated view of civil aeronautics R&T challenges and priorities.

The Decadal Survey focuses on five areas that encompass the R&T of greatest relevance to civil aeronautics:

• Area A: Aerodynamics and aeroacoustics.

• Area B: Propulsion and power.

• Area C: Materials and structures.

• Area D: Dynamics, navigation, and control, and avionics.

• Area E: Intelligent and autonomous systems, operations and decision making, human integrated systems, and networking and communications.

The Decadal Survey then identifies and prioritizes within each area a set of key R&T challenges according to their ability to accomplish strategic objectives for U.S. aeronautics research. At the time the study was conducted, the federal government had yet to define what those strategic objectives shouldbe. Therefore, in order to conduct the ranking, the authors of the Decadal Survey identified and definedsix strategic objectives that, in their estimation, should motivate and guide the next decade of civil aeronautics research in the United States, pending the release of a national research and development(R&D) plan for aeronautics.

The six strategic objectives from the Decadal Survey of Civil Aeronautics are as follows (NRC, 2006, p. 1):

In the same way, the research plans for the Next Generation

Air Transportation System (NGATS)

Air Traffic Management(ATM)-Airportal and ATM-Airspace

Projects were prepared before the Next Generation Air Transportation System Joint

Planning and Development Office (JPDO) had formally established R&D requirements.

As a result the Airportal and Airspace Projects are a good-faith effort to meet expected JPDO requirements in both content and timing, pending release of an R&D:
• Increase capacity.

• Improve safety and reliability.

• Increase efficiency and performance.

• Reduce energy consumption and environmental impact.

• Take advantage of synergies with national and homeland security.

• Support the space program.

A quality function deployment (QFD) process was used to identify and rank-order a total of 89 R&T challenges in relation to their potential to achieve the above strategic objectives. The Decadal Survey recommends that NASA use the 51 highest-priority challenges as the foundation for the futureof NASA’s civil aeronautics research program during the next decade (see Table 1-1).

The Decadal Survey of Civil Aeronautics identifies several R&T challenges that are a high national priority, but they are not a high priority for NASA. This was the case if the challenge was poorly aligned with NASA’s mission, if other organizations were likely to overcome the challenge, if NASA lacked the supporting infrastructure to investigate a particular challenge, and/or if the level of risk associatedwith the challenge was inappropriate for NASA research. The following challenges from the Decadal Survey fall into this category (i.e., high national priority, but not a high NASA priority):

• B11. Alternative fuels and additives for propulsion that could broaden fuel sources and/or lessenenvironmentalimpact

• B13. Improved propulsion system tolerance to weather, inlet distortion, wake ingestion, birdstrike, and foreign object damage

• C11. Novel coatings

• C13. Advanced airframe alloys

• D11. Secure network-centric avionics architectures and systems to provide low-cost, efficient,fault-tolerant,onboard communications systems for data link and data transfer

• D13. More efficient certification processes for complex systems

• E11. Automated systems and dynamic strategies to facilitate allocation of airspace and airportresources

• E13. Feasibility of deploying an affordable broad-area, precision navigation capability compatiblewith international standards

• E17. Change management techniques applicable to the U.S air transportation systemGiven the statement of task for this study, this report does not address NASA research as it relatesto the above challenges or other challenges that are not included in

The Decadal Survey also makes eight recommendations that summarize action necessaryto properly prioritize civil aeronautics R&T and achieve the relevant strategic objectives.requirements document by the JPDO. Likewise, the committee’s assessments necessarily reflect the status of those projects atthat point in their evolution. QFD is a group decision-making methodology often used in product design.

The Decadal Survey of Civil Aeronautics assumes that risk is too low for NASA if it is so low that industry can easilycomplete the research, and the risk is too high if the scientific and technical hurdles are so high that there is very little chanceof success.

The numbering of the challenges here and throughout this report is in accordance with the numbering scheme in the DecadalSurvey of Civil Aeronautics (NRC, 2006).

WORKFORCE

There are - among NASA, the academic community, and the civilian aerospace industry - enoughskilled research personnel to adequately support the current aeronautics research programs at NASAand nationwide, at least for the next decade or so. NASA may experience some localized problems atsome centers, but the requisite intellectual capacity exists at other centers and/or in organizations outside NASA. Thus, NASA should be able to achieve its research goals, for example, by using NASA ResearchAnnouncements or other procurement mechanisms; through the use of higher, locally competitive salariesin selected disciplines at some centers; and/or by creatinga virtual workforce that integrates stafffrom multiple centers with the skills necessary to address a particular research task. The content of the NASA aeronautics program, which has a large portfolio of tool development but little or no opportunitiesfor flight tests, may in some cases hamper the ability to recruit new staff as compared with the spaceexploration program. In addition, there will likely be increased requirements for specialized or newskill sets. Workforce problems and inefficiencies can also arise from fluctuations in national aerospaceengineering employment and from uneven funding in particular areas of endeavor.

REFERENCES

NRC (National Research Council). 2006. Decadal Survey of Civil Aeronautics:

Foundation for the Future. Washington, D.C.: The National Academies Press.

Available online at
http://www.nap.edu/catalog.php?record_id=11664.

NRC. 2007. Building a Better NASA Workforce: Meeting the Workforce Needs for the National Vision for Space Exploration. Washington,D.C.: The National Academies Press.

Available online at www.nap.edu/catalog.php?record_id=11916.

NSTC (National Science and Technology Council). 2006. National Aeronautics Research and Development Policy. Washington, D.C.: Officeof Science and Technology Policy.

Available online at www.ostp.gov/html/NationalAeroR&DPolicy12-19-06.pdf.

NSTC. 2007. National Plan for Aeronautics Research and Development and Related Infrastructure. Washington, D.C.: Office of Science andTechnology Policy.

Available online at www.aeronautics.nasa.gov/releases/12_21_07_release.htm.