In Aircraft

BE-1732 Human factors in aircraft dispatch and maintenance safety Dr. N. Me Donald Univ. Dublin Trinity College... 

Titanium is not a rare element it is the most abundant transition metal after iron, and is widely distributed in the earth s surface, mainly as the dioxide TiOj and ilmenite FeTi03. It has become of commercial importance since World War II mainly because of its high strength-weight ratio (use in aircraft, especially supersonic), its... 

Flame-Retardant Treatments For Wool. Although wool is regarded as a naturally flame-resistant fiber, for certain appHcations, such as use in aircraft, it is necessary to meet more stringent requirements. The Zirpro process, developed for this purpose (122,123), is based on the exhaustion of negatively charged zirconium and titanium complexes on wool fiber under acidic conditions. Specific agents used for this purpose are potassium hexafluoro zirconate [16923-95-8] [16923-95-8] K ZrF, and potassium hexafluoro titanate [16919-27-0], K TiF. Various modifications of this process have been... 

Resihency provides another opportunity for the mbber functioning as a cushion between stainless steel loop clamps and fuel—hydraulic fluid lines in aircraft. Pratt and Whitney E-lOO military jet engine use (12) provides vibration damping without the clamp abraiding the tube surfaces in normal service as well as at temperatures down to —55°C. 

Dibasic acid esters and polyol esters are used as the bases in all aircraft jet-engine lubricants. They also are employed in aircraft greases that are subjected to wide temperature ranges. 

Viscosity improvers are primarily used in multigrade automotive engine oils, automatic transmission oils, power steering fluids, and gear oils. They also find use in aircraft and some industrial hydrauHc fluids for low temperature use. 

Ester fluids are modified with additives in much the same manner as petroleum oils. They are stabili2ed with an oxidation inhibitor, eg, 0.5 wt % phenothia2ine. Improved load capacity for gears and rolling bearings in aircraft engines is provided by 1—5% tricresyl phosphate. Zinc... 

A third group includes silver—nickel, silver—cadmium oxide, and silver—graphite combinations. These materials are characterized by low contact resistance, some resistance to arc erosion, and excellent non sticking characteristics. They can be considered intermediate in overall properties between silver alloys and silver or copper—refractory compositions. Silver—cadmium oxide compositions, the most popular of this class, have wide appHcation in aircraft relays, motor controllers, and line starters and controls. 

Demands for improved efficiency in aircraft gas turbines led to the use of a family of age hardenable, controlled expansion superaHoys for engine seals and casings. INCOLOY aHoys 903 [61107-16-2] (UNS N19903), 907 [107652-23-3] (UNS N19907), and 909 evolved from a continuing effort to improve the environmental resistance of this Cr-free, Fe—Ni—Co based system. 

A mixture of PhenoHc MicrobaUoons and resin binder has a putty-like consistency. It can be molded to shape, troweUed onto surfaces, or pressed into a core. Curing gives a high strength, low density (0.144 g/cm ) foam free of voids and dense areas, and without a brittle skin. Syntactic foams are used in widely diverse appHcations, including boat flotation aids stmctural parts in aircraft, submarines, and missiles stmctural cores for waU panels and ablative heat shields for reentry vehicles and rocket test engines. 

Aircraft Sealants. Polysulfides have been used for sealing fuel tanks and aircraft stmctural components since the 1940s. There are stringent requirements for these sealants. They must have outstanding resistance to fuels and exceUent adhesion to many different materials such as various metal aUoys and protective coatings used in aircraft constmction. The sealants must also perform in extremely variable weather conditions (10). The polysulfides have an exceUent performance record. 

Proprietary blend formulations based on polysulfone, polyethersulfone, and polyphenylsulfone are sold commercially by Amoco Corporation to meet various end use requirements. The blends based on polysulfone are sold under the MINDEL trademark. A glass fiber-reinforced blend based on PES is offered under the trade name RADEL AG-360. This offers most of the performance characteristics of 30% glass fiber-reinforced polyethersulfone but at a lower cost. Two blend product lines are offered based on PPSF. These are designated as the RADEL R-4000 and R-7000 series of products. The former is a lower cost alternative to RADEL R PPSF homopolymer offering most of the performance attributes unique to PPSF. The R-7000 series of resins have been formulated for use in aircraft interiors for civil air transport. They exhibit a very high degree of resistance to flammabihty and smoke release. 

Strontium Chromate. Strontium chromate [7789-06-2] SrCrO, is made by precipitation of a water-soluble chromate solution using a strontium salt or of chromic acid using a strontium hydroxide solution. It has a specific gravity of 3.84 and is used as alow toxicity, yellow pigment and as an anticorrosive primer for zinc, magnesium, alurninum, and alloys used in aircraft manufacture (8) (see Corrosion and corrosion control). 

Combustion. The primary reaction carried out in the gas turbine combustion chamber is oxidation of a fuel to release its heat content at constant pressure. Atomized fuel mixed with enough air to form a close-to-stoichiometric mixture is continuously fed into a primary zone. There its heat of formation is released at flame temperatures deterruined by the pressure. The heat content of the fuel is therefore a primary measure of the attainable efficiency of the overall system in terms of fuel consumed per unit of work output. Table 6 fists the net heat content of a number of typical gas turbine fuels. Net rather than gross heat content is a more significant measure because heat of vaporization of the water formed in combustion cannot be recovered in aircraft exhaust. The most desirable gas turbine fuels for use in aircraft, after hydrogen, are hydrocarbons. Fuels that are liquid at normal atmospheric pressure and temperature are the most practical and widely used aircraft fuels kerosene, with a distillation range from 150 to 300 °C, is the best compromise to combine maximum mass —heat content with other desirable properties. For ground turbines, a wide variety of gaseous and heavy fuels are acceptable. 

A gas turbine used in aircraft must be capable of handling a wide span of fuel and air flows because the thmst output, or pressure, covers the range from idle to full-powered takeoff. To accommodate this degree of flexibiUty in the combustor, fuel nozzles are usually designed with two streams (primary and secondary flow) or with alternate tows of nozzles that turn on only when secondary flow (or full thmst power) is needed. It is more difficult to vary the air streams to match the different fuel flows and, as a consequence, a combustor optimized for cmise conditions (most of the aircraft s operation) operates less efficiently at idle and full thmst. 

The lower volatihty of JP-8 is a significant factor in the U.S. Air Force conversion from JP-4, since fires and explosions under both combat and ordinary handling conditions have been attributed to the use of JP-4. In examining the safety aspects of fuel usage in aircraft, a definitive study (15) of the accident record of commercial and military jet transports concluded that kerosene-type fuel is safer than wide-cut fuel with respect to survival in crashes, in-flight fires, and ground fueling accidents. However, the difference in the overall accident record is small because most accidents are not fuel-related. 

Pentaerythritol with its four primary hydroxyl groups is used for the preparation of tetraesters and presents Httie difficulty except for its high melting point of 263°C, when pure. Pentaerythritol tetraesters are used in aircraft lubes, synthetic drying oils, and alkyds. Esters derived from trimethylo1 alkanes and dipentaerythritol are also used in alkyd resins (qv). Esterification may take place in situ during preparation of the alkyd. 

D. H. Middleton, ed.. Composite Materials in Aircraft Structures, Longman Scientific and Technical, London, 1990. 

Eor more demanding uses at higher temperatures, for example, in aircraft and aerospace and certain electrical and electronic appHcations, multifunctional epoxy resin systems based on epoxy novolac resins and the tetraglycidyl amine of methylenedianiline are used. The tetraglycidyl amine of methylenedianiline is currently the epoxy resin most often used in advance composites. Tetraglycidyl methylenedianiline [28768-32-3] (TGALDA) cured with diamino diphenyl sulfone [80-08-0] (DDS) was the first system to meet the performance requirements of the aerospace industry and is still used extensively. 

Current and Future Materials Usage in Aircraft Gas Turbine Engines, Metals and Ceramics Information Center, Battelle Laboratories, 505 King Avenue, Columbus, Ohio 43201, USA. 

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