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the part is cleaned and soaked with a fluorescent penetrant for an appropriate length of time. Then the part
is rinsed, and all the penetrant is cleaned from its surface.
The part is vibrated while it is being examined under a black light. If the vibration opens up a
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 80
crack that has accepted some of the penetrant, the crack will show up as a blinking light.
blip (radar indication). A spot of light on a radar scope caused by a received signal, or a return from a
reflecting object. Blips are also called echoes.
blisk (turbine engine component). A turbine stage machined from a single slab of steel. The disk and
blades are an integral unit.
blister (evidence of corrosion). A raised spot on a piece of metal that contains the salts of corrosion.
Corrosion forms under the surface of the metal, and since its salts have so much more volume than
the metal they displace, the surface layer of metal is pushed out to form the blister.
blizzard (meteorology). Severe weather conditions characterized by low temperatures and strong winds
bearing a great amount of snow, either falling or picked up from the ground.
block diagram. A functional diagram of a system in which the units are represented by blocks that
describe the functions of the unit and show its relationship to the other units of the system. Arrows between
the blocks show the direction of flow of energy or information within the system. Block diagrams do not
show any of the actual components.
“Blocked” (air traffic control communications). The phrase used to indicate that a radio transmission has
been distorted or interrupted due to multiple simultaneous radio transmissions.
block heater (sheet metalworking tool). An electrical heater embedded in the die used for hot dimpling
sheet metal.
blocking capacitor (electronic circuit component). A capacitor having a high impedance to DC and
low-frequency AC, but a low impedance, or a small opposition, to the AC signal being passed through the
circuit.
block plane. A small hand-held woodcutting tool used for cutting across the grain of wood and for planing
the ends of a board to make them smooth.
block test (aircraft engine test). An operational test of an aircraft engine installed in a test cell.
Block tests are used to determine the condition of the engine.
block-to-block time (aircraft records). The amount of elapsed time between an aircraft leaving the
departure ramp for the purpose of flight and its reaching the arrival ramp at the end of the flight.
bloom (metal processing). A semifinished mass of steel formed from an ingot in the process of being
rolled into a billet.
blow-in doors. Spring-loaded doors in the inlet duct of some turbojet or turbofan engine installations that
are opened by an air pressure differential when the inlet air pressure becomes a certain amount lower than
that of the ambient air.
Air flowing through the doors adds to the normal inlet air passing through the engine and helps
prevent compressor stall.
blow molding. A form of plastic molding in which a hollow tube of thermoplastic material is heated inside
a mold.
Air pressure is applied to the inside of the tube, and the soft plastic material is forced out against
the walls of the mold. The outside of the part takes the form of the inside of the mold. The mold is then
opened and the molded part removed.
blow-by (reciprocating engine malfunction). The loss of pressure in the engine cylinder caused by
leakage past the piston rings.
blow-down turbine (reciprocating engine component). A power-recovery device used in the exhaust
system of a reciprocating engine.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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A blow-down turbine is a velocity-type turbine driven by the exhaust gases from the engine and
coupled through a fluid coupling to the engine crankshaft. Blow-down turbines are also called
power-recovery turbines, or PRTs.
blower (reciprocating engine component). An internal gear-driven supercharger in an aircraft
reciprocating engine.
Blowers increase the pressure of the air after it passes through the carburetor and improve the
uniformity of the distribution of the fuel-air mixture to all the cylinders.
blower section (reciprocating engine crankcase section). The section of an aircraft reciprocating engine
crankcase that houses the internal, gear-driven supercharger.
blower. A mechanical device, such as a fan, used to move a volume of air.
blowing dust (meteorology). Dust particles picked up locally from the surface and blown about in clouds
or sheets.
blowing sand (meteorology). Sand picked up locally from the surface and blown about in clouds or sheets.
　
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