Civil Aircraft

It is clear that European civil aircraft manufacturers adopted adhesive bonding for major structural elements much more rapidly than their American counterparts, but it is difficult to determine exactly why. Certainly a number of contributing factors are obvious. One was a history of success in incorporating adhesively bonded structure in military aircraft such as the Mosquito. Although the Mosquito was the most unusual and extreme example of adhesively bonded structure, other European wartime aircraft contained bonded structure as well. American military craft of the time were almost exclusively riveted aluminum structure. 

Though toughened phenolic adhesives remain in use for specific applications, toughened epoxy adhesives have dominated metallic bonding on civil aircraft since their development in the 1960s. Advances since then have been incremental and mostly revolving around manufacturing issues such as handleability and allowed out-time. 

Skins with bonded doublers have been used successfully on a large number of civil aircraft and are still used on new designs. The only widespread in-service problem with bonded doubler assemblies has been delamination caused by unstable surface preparation. Early fuselage skins with bonded doublers and inadequate surface preparation experienced severe delamination and subsequent corrosion. A majority of these delaminated doublers were the fail-safe tear straps (Fig. 27). Although the tear strap bond does not cany structural load, the bond... 

Corrosion inhibitor/lubricity improvement additives are used panicularly in militai y fuel for the dual puiyiose of passivating metal surfaces and improving the lubricating properties of the fuel in equipment such as fuel pumps. The militai y also specifies the use of a fuel system icing inhibitor as an additive to prevent filter blocking by ice crystal formation, because militai y aircraft tend not to use fuel line filter heaters, which are standard equipment on civil aircraft. 

Aviation gasoline, now usually found in use in light aircraft and older civil aircraft, has a narrower boiling range than conventional (automobile) gasoline, that is, 38 to 170°C (100 to 340°F) compared to approximately... 

Phosphate esters are also used as hydraulic fluids in civil aircraft where thermal stability is less important than their low-temperature viscosities and cold flow properties. Trialkyl and alkyl-aryl phosphates are used which, when formulated with a VI improver, give fluids with pour points of -55 to -65°C and a VI of 170-300. They are also chosen for other low-temperature applications for conditions such as those found on North Sea, and similar weather condition, oil rigs. 

The low-temperature fluidity requirements of the applications in which this fluid is used mandate a base oil of a relatively light nature which results in a low flash point. The specification requirement is 81°C minimum using the Pensky-Martens closed (PMC) method [22]. The US military concerns for the flammability of this fluid led to the requirement for a less flammable hydraulic fluid. Civil aircraft of the period were already using phosphate ester-based hydraulic fluids because of their fire resistance. But their very different chemistry meant they were incompatible with hydraulic systems developed for the mineral-type fluid and conversion of those systems to accommodate the phosphate ester fluid was considered too expensive. 

In the USA, the requirement for quality of jet fuels (list of the physical-chemical parameters and operational properties) for civil aircraft are made out as the ASTM D 1655 specification. Accordingly, the following fuels are made ... 

The requirements for British jet fuels for civil aircraft are established by the specification D, Eng. RD (DERD) 2494. Previously, it was developed for military aircraft. This is fuel of the kerosene type with a freezing temperature of -47°C. 

New Materials for Next-Generation Commercial Transports, Committee on New Materials for Advanced Civil Aircraft, National Research Council, 1966, p 33... 

We can hardly go around using our SD platforms on civil aircraft just because they have a dodgy processor," Ryle Thome said. 

The example chosen here is that of inspection of civil aircraft as part of the system for assuring the public that airworthiness is maintained throughout the service life of airframes, avionics, and aircraft structures. It is part of a maintenance process and is typical of many transportation applications, such as for maritime transport, heavy goods vehicles, or even the space shuttle. 

Airworthiness of civil aircraft depends upon a process by which a team composed of aircraft manufacturers, regulators, and one or more airlines predicts possible system failures. This process. Maintenance Steering Group 3 (MSG-3), considers possible failure pathways (e.g., in structures, controls, avionics) and for each pathway determines a recovery strategy. For structural failure, this may be replacement after a fixed service life, regular inspection to ensure detection, or an indication to crew of the malfunction. The concern here is with the reliability of the primary failure recovery system for aircraft structural inspection regular inspection to ensure detection. 

Susceptibility to interlaminar failure is a major weakness of advanced laminated composite materials. It can occur by in-plane shearing (i.e., sliding) (mode II). and out-of-plane shearing (i.e.. tearing) (mode III) as well as by tensile (mode I) deformation. Mode II loading is of particular interest, as values have been shown to correlate with compression after impact data [142.143]. which is required for such purposes as civil aircraft certification. 

Aircraft coatings normally consist of two coats. The topcoat used for civil aircraft is a high-gloss two-pack polyurethane product, cured with aliphatic isocyanates. Single-coat systems based on thermoplastic acrylic resins have been used for military aircraft, but are being replaced by polyurethane topcoats [11.10]. 

An important issue in the operation of modem civil aircraft is the management of pilot alertness. It is expected that a fiituie alertness management system will be based on a mathematieal model for alertness that incorporates several mecharrisms for the dyrramies of alertness (Folkard Akerstedt, 1992). This model will be built on an empirieal data base. The purpose of the present study is to provide additional knowledge about alertness dynamics that will contribute to an alertness management system in eivil aviation. 

Current civil aircraft applications have concentrated on replacing the secondary stracture with fibrous composites where the reinforcement media have either been carbon, glass, Kevlar or hybrids of these. The matrix material, a thermosetting epoxy system, is either a 125 °C or 180 °C curing system with the latter becoming dominant... 

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