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zener current
zener current That flowing in insulator in electrical field
sufficiently intense to excite electrons direct from valence
to conduction.
zener diode Si junction diode having specific peak
inverse voltage, at which point it breaks down and
suddenly allows flow.
zener voltage 1 Field strength needed to initiate zener
current, about 10 6 V/mm.
2 That associated with reverse-VA of semiconductor,
more or less constant over wide range of current.
zenith Point on celestial sphere directly overhead.
Strictly this is observer’s *; astronomical * is where
plumb-line would intersect celestial sphere, and geographical
* is where line perpendicular to smooth Earth
would do so. These are not all synonymous.
zenith attraction Effect of planetary gravity on freefalling
body (originally, Earth on meteorite) of increasing
velocity and moving radiant toward zenith.
zenith distance Angular distance from celestial body to
zenith.
zenographic Of positions on surface of Jupiter, referred
to planet’s equator and specified reference meridian.
zeolite Natural hydrated silicate of Ca and Al; catalyst
used in Obogs filter beds.
zephyr Light warm westerly wind [Mediterraneon].
ZEPL Self-forging fragment submunition (G).
Zeppelin Though a proper name, often used to mean
any rigid airship.
zepto Multiplied by 10 -23 , symbol z; see zetta.
zero defects Conceptual (sometimes attainable) goal of
perfection, esp. in manufacturing industry (chiefly US).
zero-delivery pressure In delivery line of variabledisplacement
pump at normal operating speed with zero
stroke.
zero-draft forging One without draft, ie to finish
dimensions.
Zerodur Glass ceramic with very low coefficient of
expansion; used for LINS.
zero-force separation Interstage separation in which all
mechanical links have already been broken, including
all electrical connectors, etc.
zero-fuel weight MTOW minus total usable-fuel weight;
usually limiting case for wing bending moment because
wings are empty and fuselage is full. One symbol is W e ,
from empty.
zero-g See zero gravity.
zero-gravity Free-fall, weightlessness; or in deep space
remote from massive bodies.
zero gross gradient Altitude at which gross climb
gradient (all engines operating, corrected for anti-icing) is
zero.
Zerol Zero-spiral angle bevel gear.
zero lash Mechanism adjusted until there is no play or
backlash, eg by using hydraulic valve lifters in piston
engine.
zero-length launch Launching of vehicle from aircraft or
surface launcher in such a way that it is free as soon as it
begins to move; in case of aircraft rockets, hung on clips
instead of being accelerated along tubes or rails; for
surface launch, thrust away by rocket boost motors whose
vertical component is greater than weight. Sometimes
abb. to zero-launch; usually abb. Zell, * launch(ing).
zero-lifed Restored to new condition after having seen
service; applies esp. to airframe or engine and follows
ZGG
meticulous inspection and rectification such that flighttime
count may legally be restarted.
zero lift Angle of attack at which aerofoil generates
neither positive nor negative lift, ie no force normal to
airstream; usually an obvious negative AOA for traditional
cambered wing at below M crit but for supersonic
wing can be positive angle.
zero-lift line Drawn through trailing edge of aerofoil
parallel to relative wind when lift is zero.
zero meridian Prime Meridian, 0° longitude.
zero point Location of centre of NW at moment of
detonation; usually above or below ground zero.
zero-power transfer switch Automatically switches load
when waveform is passing through zero.
zero-range ring Circular arc forming range origin of
most weather radars, and many other polar-type displays
(most unusual to have origin as point).
zero rate of climb speed TAS at which, for an established
engine power [not necessarily maximum], drag reduces
climb gradient to zero.
Zero Reader Pioneer (Sperry) flight instrument with
cross-pointers driven by various selectable sensors to
control trajectory (vertical and lateral displacement), pilot
steering aircraft so that both needles cross at origin of
display in method first used on ILS meter. In most
respects similar to ILS meter that can accept inputs from
en route navaids and attitude sensors.
zero-splice Monolithic, made in one piece.
zero stage Extra axial stage added on front of existing
multi-stage axial compressor in new uprated version of
gas-turbine engine; can be overhung ahead of front
bearing and may or may not be preceded by inlet guide
vanes. Hence, more rarely, zero-**, for a second
additional upstream stage.
zero-thrust pitch Distance propeller advances in one
revolution when operating at normal speed but moved
through still air by external force so that it generates no
thrust; also called exponential mean pitch.
zero-timed Engine overhauled to Service limits, less
rigorous than factory-remanufactured.
zero-torque pitch Distance propeller advances in one
revolution when moved through still air by external force
at such a speed that its drive torque is zero; ie when windmilling
in frictionless bearings. Symbol P a .
zero/zero landing Totally blind helicopter landing
enveloped in snow.
zero/zero seat Ejection seat qualified for operation at
zero height, zero airspeed; ie pilot can safely eject from
parked aircraft.
zero-zero stage See zero stage.
Zerstörer Destroyer, large or long-range fighter (G,
WW2).
zetta Multiplied by 10 21 symbol Z; see zepto.
ZF Zero force (separation).
z F Moment arm about c.g. of net propulsive force;
usually acts in purely vertical plane, ie in pitch.
ZFCG Zero-fuel c.g.
ZFGW Zero-fuel gross weight [= ZFW].
ZFT Zero flight time (of hardware, or pilot recurrent
training or type-conversion entirely on simulator).
ZFW Zero-fuel weight.
ZG 1 Zero gravity (also Z-g).
2 Zerstörergeschwader (G, WW2).
ZGG Zero gross gradient.
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