MIL-HDBK-244A 6 apr 90.pdf

MIL-HDBK-244A
(c) Correct weapon carriage station - Most present day
aircraft are required to include a large variety of stores in their weapons
complement to meet their multi-role missions, which generally include several
of the following: intercept, combat air patrol, interdiction,close air
support, surveillance, early warning and anti-submarine. Coupled with the
large variety of weapons required for carriage is the need to have multistation
capability for maximum ordnance. Mating the proper weapon to the
correct carriage station requires that store separation anaylysis be performed
during early design phases.
(d) Variable store geometry- Since there are many types of .
ordnance presently available that change geometric characteristics
immediately upon employment, the changed geometry must be considered in
carriage station selection for satisfactoryaircraft/store compatibility.
(e) Ordnance exhaust plumes - Present day aircraft generally
carry some ordnance that contain rocket motors, such as 2.75 inch or 5
inch rockets, and air-to-air or air-to-surfacemissiles. Since the exhaust
plumes from rocket motors can cause aircraft engine flame-out or degraded
performance, selection of carriage stations for these types or ordnance must
include a consideration to provide sufficient distance away f+om-aircraft
engine inlets. The effect of rocket exhaust impinging uponnearby aircraft
structure such as the horizontal tail should be assessed together with the
design of structure to minimize severe erosion and corrosion problems and
heavy corrective maintenance time. The effect of metallic particles in the
exhaust plume on sensors or other devices in the store itself or adjacent
stores is another area which should be assessed. In some cases, the aircraft
may fly through the rocket exhaust after the store has been launched. When
such conditions occur, the above effects should be considered.
(f) Delivery accuracy- Both the initial store employment
trajectory and its subsequent terminal impact are largely dependent upon the
magnitude and direction of the net loads acting on the store at the instant
of release (i.e. inertial’,plus the carriage aerodynamic and interference
loads prevailing at the release flight condition). The integrated effect of
large drag and normalforces on the storecaused by separation transient
oscillations results in a trajectory deviation from that which would have
developed without the oscillation. The trajectories of unstable or
marginally stable stores are more seriously affected in this manner by large ~
and unsymmetrical carriage loads. Thus, the separation trajectories can be
unrepeatable or unpredictable. Another factor having a significant effect on
the delivery accuracy is the geometry of the store release station. For
example, if three stores are carried on a triple ejector rack (TER),with one
store ejected vertically and the other two at 45” from the vertical, the store
ejected vertically will impact the ground dozens of feet behind the other two,
simply because the other two stores are being ejected with a vertical
acceleration of 0.707g and the first is ejected at l.Og. This “g” difference
is entirely caused by the the geometry’of the TER. To enhance delivery
accuracy, it is imperative, therefore, that stores be carried and released in
aerodynamic fields of low interference that aid separation. Such,flow fields
generate low pitching and yawing moments about the store center of gravity,
which are desirable for gravity releases. Moreover, sufficiently rigid
structuremust be made available to the rack, to obviate rack flexure, maximize
allowable ejector impulse and make ejectorseparation impulses applied to the
store uniform-within the rack capability.
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