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YBC
YBC Years between calibrations.
YBCO Yttrium barium copper oxide.
YbYAG Ytterbium/YAG.
YC 1 Tourist class.
2 Yaw computer.
YCV Ship class: aircraft transportation lighter (USN).
YCZ Yellow caution zone (runway lighting).
YD, Y/D Yaw damper.
yd Yards [rarely, yds].
YDA 1 Yesterday.
2 Yaw-damper actuator.
YDC Yaw-damper computer.
YE Young Engineers [Liphook, GU30 7AZ] (UK).
yellow General colour for caution [in many airborne and
ground systems], also called amber.
yellow arc Range on dial instrument indicating caution,
or higher than normal.
yellow card 1 Formal warning to airshow participant
following single serious breach of rules or potentially
serious flying error.
2 Warning notice from captain to passenger[s].
yellow caution zone Region (of runway or glideslope
angle) marked by yellow or amber lights.
yellow gear/stuff Aircraft GSE vehicles on airfield or
carrier (service carts, tugs, dollies, handling and storeloading
equipment).
yellow sector 1 Area on left of ILS centreline (on right if
using back course).
2 Arc on traditional ASI which should not be entered in
severe turbulence.
YES Youth and Education Strut (PFA).
yield 1 Explosive power of NW, measured in TNT equivalent
weights and usually given as: very low, under 1 kt;
low, 1–10 kt; medium, 10–50 kt; high, 50–500 kt; very high,
over 500 kt (0.5 Mt).
2 Revenue per traffic unit, eg per tonne-km, pax-mile,
etc.
yield factor of safety Specified factor used in some airworthiness
requirements to prevent permanent deformation of
structures.
yield load Limit load × yield factor of safety.
yield point Unit tensile stress at which deformation
continues (to breakage) without further increase in applied
load. Measured by loading specimen to point where a
permanent set occurs, typically 0.2%. This is slightly higher
than elastic limit and not normally approached in practice.
yield strength Unit stress corresponding to a specified
permanent elongation, for light alloys usually taken as
0.2%.
yield stress Ambiguously, stress at yield point, which may
be higher than at yield strength; except in the case of ductile
materials that experience strain hardening, the greatest that
material can reach.
YIG Yttrium indium garnet.
YL Year lease (suffix to two digits of year).
YM Young Members; B adds Board; S adds Section
(RAeS).
YMS 1 Yield management system.
2 See YM.
Y n The n th quadrature signal sample applied to a digital
filter during any one integration period.
yocto Prefix, multiplied by 10 -24 , symbol y; see yotta.
Yoder rolling Manufacture of complex sections by
Y ζ
sequential precision rolling operations tailored to each
section.
yoke 1 Control column of large aircraft in which roll
input is by two laterally pivoted handgrips in form of a Y.
Occasionally refers to a wheel or spectacles.
2 Main magnetic structure of electrical machine
supporting poles and conveying flux round linkage on each
side of armature.
3 Frame on which are wound CRT deflection coils, or
case of high-permeability metal surrounding such coils.
4 Interconnecting cross-member or tie.
5 In particular, tie linking helicopter main-rotor blade to
hub.
6 Forked mounting, eg passing both sides of nosewheel.
yoke clip Alternative name for yokemount.
yokemount On centre of handwheel or spectacles (eg, for
document or notepad).
YOS Years of service.
YOT “You over there,” man in right-hand seat of sideby-side
military cockpit. (colloq.).
yotta Multipled by 10 24 symbol Y; see yocto.
Young-Helmholtz Original theory of colour vision, based
on receptors for red/green/blue.
Youngman flap Patented (Fairey) trailing-edge flap
carried on struts below trailing edge and in addition to
normal deflection also having a negative (usually –30°)
setting for use as dive brake.
Young’s modulus Basic measure of material strength
under tension, ratio of normal stress (within limit of
proportionality) to strain, ie ratio of tensile load per unit
cross-section area to elongation per unit length, within
elastic limit, symbol E. SI units kN/m 2 or MN/m 2 .
yo-yo Family of air-combat manoeuvres in horizontal
and vertical planes intended to reduce angle-off or hold
nose/tail separation and thus prevent overshoot of
defender’s turn. Hi-speed * trades speed for height, lo-speed
* opposite.
YP Yield point.
YPA Young Pilots’ Association (UK).
YR Your.
yr Year.
YS Yield strength (or stress).
YSAS Yaw-stability augmentation system.
YSZ Yttria-stabilized zirconia.
Y T Side force due to asymmetric thrust.
y T Lateral offset distance of mean thrust.
YTD year to date.
YTS Youth training scheme (UK).
Y TS Cross-stream distance across test section (tunnel).
ytterbium Yb, silvery metal, density 6.97, MPt 824°C,
increasing use in electronics and steels.
yttrium Y, soft silvery metal, density 4.47, MPt 1,522°C,
used in alloys, glasses, semiconductors and YAG, YIG.
Y2K 2000 AD.
Y 2 O 3 Yttrium oxide.
yugging Uncommanded rapid unsteadiness, usually
up/down and rocking movements, between aircraft in
formation aerobatic team, usually caused by turbulence.
Yukawa potential Describes meson field about a nucleon.
Y v Force derivations on the fuselage; (Y v ) B is due to the
fuselage, (Y v ) F is due to the fin, and (Ȳ - ) is the actual aerodynamic
side force.
Y VS Cross-stream distance along vane set (tunnel).
Y ζ Y-zeta, side force due to rudder deflection.
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