- Industry: Aviation
- Number of terms: 16387
- Number of blossaries: 0
- Company Profile:
Aviation Supplies & Academics, Inc. (ASA) develops and markets aviation supplies, software, and books for pilots, flight instructors, flight engineers, airline professionals, air traffic controllers, flight attendants, aviation technicians and enthusiasts. Established in 1947, ASA also provides ...
A type of airflow over an airfoil in which the air passes over the surface in smooth layers with a minimum of turbulence. With most airfoils, there is a layer of air adjacent to the surface that flows in a random fashion, even sometimes reversing its direction of flow. This is called the boundary layer.
A laminar-flow airfoil is designed in such a way that the boundary layer has a minimum thickness, and nearly all the air flows in smooth layers. Laminar flow of the air decreases the drag produced by the airfoil.
Industry:Aviation
A type of airplane control wheel that may be moved from in front of the left seat to a position in front of the right seat. This is done so the airplane can be flown from either seat. To throw the wheel over, a pin in the control column is released, and the upper part of the column on which the wheel is mounted pivots so it can be moved from one side to the other.
Industry:Aviation
A type of airplane wing construction that uses several small spars extending along the span of the wing to carry the structural loads. Multiple small spars carry the load better and weigh less than the two larger spars used in many aircraft wings.
Industry:Aviation
A type of alternating current induction motor used for light-duty, constant-speed loads, such as fans, blowers, and tape players. A coil excited by single-phase alternating current is wound around a laminated steel frame, and a squirrel-cage rotor is mounted in bearings attached to the frame. Shading coils made of one or two bands of heavy copper are installed around diagonally opposite pole shoes, the part of the frame around the rotor.
Current induced into the shading coils by the AC in the exciter coil demagnetizes the part of the pole shoe around which it is wound. The AC alternately magnetizes and demagnetizes the corners of the pole shoes, producing a rotating magnetic field which the squirrel-cage rotor follows. Shaded-pole motors have a relatively constant speed, but their torque is quite low.
Industry:Aviation
A type of alternating current motor in which the line voltage is connected across stationary windings in the motor housing. The rotor of an induction motor is made in the form of a “squirrel cage.” Bars of copper or aluminum are embedded in slots in a laminated soft-iron core, and are welded to heavy copper or aluminum plates on each end of the core. There is no electrical connection to the rotor.
The stator winding serves as the primary of a transformer, and the bars and end plates of the rotor act as the secondary. Current induced into the rotor bars causes a magnetic field that reacts with the field of the stator, and this reaction causes the rotor to turn. The magnetic field of the stator of a single-phase induction motor does not rotate, but rather it pulses on and off. A separate start winding is wound in the stator to produce a rotating field for starting a single-phase motor. The phase of the current in the start winding is shifted by a capacitor or inductor so that it is different from the phase of the current in the run winding. This shifted phase produces a rotating magnetic field.
As soon as the rotor is turning at the correct speed, the start winding is automatically disconnected, and the inertia of the heavy rotor keeps it spinning in the pulsing magnetic field produced by the run winding. Three-phase induction motors do not need separate start windings, because the three separate phase windings produce a rotating magnetic field.
Industry:Aviation
A type of alternating current motor that has a main and an auxiliary winding connected in parallel. The phase of the current flowing in the auxiliary, or start, winding is shifted from that flowing in the main winding, either by a capacitor or by a large difference in the resistance in the two windings. The phase difference between the current flowing in the two field windings produces a rotating magnetic field which starts the rotor spinning.
When the rotor is spinning at a specified speed, a centrifugal switch opens the auxiliary-winding circuit, and the motor operates with only the main winding.
Industry:Aviation
A type of ammeter installed between the generator output and the main bus in an aircraft electrical system. Loadmeters are calibrated in percentage of the generator’s rated output, rather than in amperes.
Industry:Aviation
A type of anti-friction bearing. Needle bearings are made of a series of relatively long, small-diameter rollers (the needles) made of hardened steel. The needles ride between two hardened and polished steel races. One race is pressed into the housing, and the other race is pressed onto the rotating shaft. Needle bearings are effective for radial loads only.
Industry:Aviation
A type of automatic control system in which part of the output is fed back into the input to help control the action. In an automatic pilot system, an attitude sensor detects a wing dropping and generates an error signal that causes the servo to move the aileron down.
A servo feedback signal is sent from the aileron to the attitude sensor, indicating that corrective action is being taken. The attitude sensor progressively cancels its error signal as the deflected aileron brings the wings back to a level attitude. By the time the wings are level, the error signal is eliminated and the aileron is no longer deflected.
Industry:Aviation
A type of automatic selector valve installed in a critical portion of a fluid power system. Fluid for normal operation of the system flows through the shuttle valve into the actuating cylinder. But if the normal system pressure fails, emergency fluid pressure can be directed into the actuator through the shuttle valve.
Shuttle valves are used in aircraft landing gear and brake systems to allow compressed air to be used to extend the landing gear or apply the brakes if the normal hydraulic system should fail.
Industry:Aviation
