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dynamic heating
dynamic heating Heating of the surface of an aircraft by
virtue of its motion through the air. Heat is generated
because the air at the surface is brought to rest relative to
the aircraft, either by direct impact in the stagnation
region or by the action of viscosity elsewhere. For practical
purposes, synonymous with aerodynamic heating and
kinetic heating.
dynamic hot bench Test facility enabling items such as
avionics or auxiliary power systems to be connected as if
they were in the aircraft.
dynamic lift Aerodynamic lift due to the movement of
the air relative to a lighter-than-air aircraft.
dynamic load A load imposed by dynamic action, as
distinct from a static load. Specifically, with respect to
aircraft, rockets or spacecraft, a load due to acceleration
as imposed by manoeuvring, landing, gusts, firing guns,
etc.
dynamic meteorology The branch of meteorology that
treats of the motions of the atmosphere and their relations
to other meteorological phenomena.
dynamic model A model of an aircraft (or other object)
in which linear dimensions, mass and inertia are so represented
as to make the motion of the model correspond to
that of the full-scale aircraft.
dynamic particle filter One which separates particulate
solids from moving fluid by making them move relative to
fluid; most common are centrifugal filter and momentum
separation.
dynamic pressure 1 Pressure of a fluid resulting from its
motion when brought to rest on a surface, given by
q=½ρV 2 ; where ρ is density and V free-stream velocity;
in incompressible flow, difference between total pressure
and static pressure.
2 Pressure exerted on stagnation point(s) on a body by
virtue of its motion through a fluid.
dynamic RAM Constructed of periodically refreshed
capacitor elements.
dynamics Main rotating parts of helicopter airframe.
dynamic sampling Concentration by flight recorder on
one particular aspect of aircraft behaviour, esp. a
malfunctioning channel.
dynamic scale Scale of flow about a model relative to a
flow about full-scale body; if two flows have same
Reynolds number, both are at same **.
dynamic sidelobe level That exceeded for 3 per cent of
time on each main-beam scan.
dynamic similarity 1 Relationship between model and
full-scale body when, by virtue of similarity between
dimensions, mass distributions, or elastic characteristics,
aeroelastic motions are similar.
2 Similarity between fluid flows about a model and fullscale
body when both have same Reynolds number.
Dzus rail
dynamic-situation modelling Program which seeks to
create a framework for producing a real-time representation
of the battlespace.
dynamic soaring Soaring by making use of kinetic
energy of air movements.
dynamic stability Characteristic of a body that causes it,
when disturbed from steady motion, to damp oscillations
set up and gradually return to original state; used esp. of
helicopters.
dynamic stall Transient or fluctuating separation of flow
over an aerofoil, especially a helicopter rotor blade,
subjected to rapidly varying angle of attack which periodically
takes it beyond the normal stall angle.
dynamic storage In EDP (1), storage in which information
is continuously changing position, as in delay line or
magnetic drum.
dynamic system See dynamics.
dynamic thrust Work done by fan or propeller in
imparting forward motion, equal to mass of air handled
per second multiplied by (V s –V), where V s is slipstream
velocity and V aircraft speed.
dynamic viscosity Shear stress in a medium divided by
shear velocity gradient, in each case between notional
adjacent layers. Symbol µ, = υρ (kinematic viscosity
multiplied by density), units ML -1 T -1 . The SI unit Nsm -2
or P a. S, has no name, but see poise, = SI unit 10.
dynamometer Device designed to measure shaft power;
torque or transmission * measures torque or torsional
deflection of shaft; electric and hydraulic * measure power
by electrical or fluid resistance; fan brake * uses air friction,
and prony brake * applies torque by mechanical
friction.
dynamotor A d.c. generator and electric motor having
common set of field poles and two or more armature
windings; one armature is wound for low-voltage d.c. and
serves as motor; other serves as generator for high-voltage
d.c.
Dynarohr Sound-suppressing multicell lining of engine
fan cases and ducts (Rohr).
dyne Abb. dyn, unit of force sufficient to accelerate 1 g
at 1 cm s –2 ; = 10 –5 ––––
1
N or g or 2.248 10 –6 981
lb.
dynode Electrode of electron multiplier which emits
secondary electrons when bombarded by electrons.
dysbarism Decompression sickness, usually caused by
release of nitrogen bubbles into blood at very low
pressure.
DZ 1 Drop (or dropping) zone.
2 light drizzle.
DZAA Drop-zone assembly aid.
Dzus fastener Countersunk screw with slotted shank
anchored in removable or hinged panel, which hooks with
half-turn into wire anchor on airframe.
Dzus rail Mounting rail for LRUs.
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