aircraft engineering
Civil Aircraft Engineers and Aircraft Sheet Metal Workers
Metal repair procedures for civil aircraft engineers.
Aircraft mechanics will tell you the airframe of a fixed wing aircraft is generally considered to consist of five principal units; the fuselage, wings, stabilizers, flight control surfaces, and landing gear.
Aircraft principal structural elements (PSE) and joints are designed to carry loads by distributing them as stresses. The elements and joints as originally fabricated are strong enough to resist these stresses, and must remain so after any repairs. Long, thin elements are called members. Some examples of members are the metal tubes that form engine mount and fuselage trusses and frames, beams used as wing spars, and longerons and stringers of metal-skinned fuselages and wings. Longerons and stringers are designed to carry principally axial loads, but are sometimes required to carry side loads and bending moments, as when they frame cutouts in metal-skinned structures. Truss members are designed to carry axial (tension and compression) loads applied to their ends only. Frame members are designed to carry side loads and bending moments in addition to axial loads. Beam members are designed to carry side loads and bending moments that are usually large compared to their axial loads. Beams that must resist large axial loads, particularly compression loads, in combination with side loads and bending moments are called beam-columns. Other structural elements such as metal skins, plates, shells, wing ribs, bulkheads, ring frames, intercostal members, gussets, and other reinforcements, and fittings are designed to resist complex stresses, sometimes in three dimensions.
Aerospace recruitment of technical staff. Read the rest of this entry »
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Landing Gear Maintenance by Licensed Aircraft Engineers
During inspection and before removing any accumulated dirt, aircraft mechanics must closely observe the area being inspected while the wingtips are gently rocked up and down. Excessive motion between normally close-fitting landing gear components may indicate wear, cracks, or improper adjustment. If a crack exists, it will generally be indicated by dirt or metallic particles which tend to outline the fault. Seepage of rust inhibiting oils, used to coat internal surfaces of steel tubes, also assists in the early detection of cracks. In addition, a sooty, oily residue around bolts, rivets, and pins is a good indication of looseness or wear.
a. Thoroughly clean and re-inspect the landing gear to determine the extent of any damage or wear. MRO teams may discover that some components require removal and complete disassembly for detailed inspection. Other components may require the assistance of stress engineers to do a specific check using an ndt inspection process such as dye penetrant inspection, magnetic particle inspection, radiographic, ultrasonic, or eddy current inspection. The frequency, degree of thoroughness, and selection of inspection methods are dependent upon the age, use, and general condition of the landing gear.
b. Qualified technical staff must inspect the aircraft or landing gear structure surrounding any visible damage, to ensure that no secondary damage remains undetected. Forces can be transmitted along the affected member to remote areas where subsequent normal loads can cause failure at a later date. Read the rest of this entry »
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Gas Turbine Aircraft Engine Design and Operation: The Way It Works
Conventional gas turbine jet engines, like the turbofan, have been around for years. They power almost all commercial aircraft and are very reliable. Every time you board a commercial aircraft, this technology is providing safe and efficient power to get you to your destination.
A gas turbine engine varies greatly in design from the engine in your car. Air enters the front of the engine through the fan section, which runs on the N1 or low-pressure shaft. In high by-pass engines, which are the most efficient, 4 times the air that continues into the core of the engine, or more, is directed around the engine producing thrust. Then the air entering the core of the engine reaches the compressor section. Here, the air is compressed in stages as it continues rearward. Since air does not like to flow from areas of low pressure to high pressure, turbine engines rely on the cascade effect. The compressor, running on the N2 shaft or high-pressure shaft, contains stages of rotor blades. These rotor blades are small titanium airfoils radiating from the shaft. Just like an aircraft wing moving through the air, these blades are positioned to produce an area of low pressure on the top and high pressure underneath. Since these blades are angled forward, the low pressure area is facing forward in the engine and the high pressure faces rearward. In between each set of rotating rotor blades, there is a ring of stationary blades called the stator vanes. These are identical titanium airfoil shaped blades positioned opposite to the rotor blades. As the area of high pressure behind the rotor blades pass the area of low pressure in front of the stator blades, the air flows from the high pressure to low pressure. This is continued through the compressor section until the pressure is increased much higher than the outside pressure. Read the rest of this entry »
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