THE BASIC DIRECTIONS OF IMPROVEMENT OF QUALITY THE UAV
EXTERNAL SURFACES
Prof. Nickolay
Zosimovych
Sharda University, Uttar
Pradesh, India
As a result of perfection of
forms modern and perspective UAV probes of typical geometrical parameters of a
surface have been made and the technique of appointment of admissions on
external surfaces is offered.
Key
words: Unmanned Aerial Vehicle (UAV), surface, aerodynamic quality, sinuosity,
technological roughness’s, ledge,
indent, constructive and technological actions, fuselage, fuel consumption, specifications,
flying vehicle (FV).
Introduction. Increase
of efficiency UAV is caused, on the one side, by a problem of fuel resources,
and with another side a tendency of change of structure of expenses for life
cycle aside reduction of a share of initial FV cost. Aircraft
engineering practice marks following basic ways of increase of FV efficiency [312]:
1. Application of
essentially new constructive decisions and materials (10…20%).
2.
Perfection of engines (20…30 %).
3.
Aerodynamics perfection (to 40 %).
The importance and urgency of improving the aerodynamic efficiency by improving the forms of modern and advanced FV, including by improving the quality of exterior surfaces, confirmed by the entire history of aviation.
Detailed
consideration of dependence of resistance from quality of performance of
external surfaces by manufacture shows that additional resistance can reach
2…10% at zero upward force [315]. The greatest share is brought by the
deviations increasing a lateral section, details for example acting in a stream
(approximately 5 %). Nearby 1.2 … 1.5 % are necessary on rivets and bolts
connections; 0.5 % on joints of sheets; leaky position of shutters and hatches gives
1.0…1.5 %; rough coloring (over 20 microns) – up to 
At
speed from above М=1.5 the size of
all components increases approximately twice and resistance from a sinuosity -
more than in 5 times. For the reasons specified above the resistance increase
through technological roughness’s for subsonic FV makes approximately 5…6 %, and
for supersonic (М=2-3) - 10…16% [315].
Perfection
of quality of external surfaces probably at the expense of constructive and
technological actions that in turn can lead to additional expenses. Therefore
an important question at definition of quality of external surfaces is the
choice of criterion for quantitative estimations of similar actions. As such
criterion for a quantitative estimation of losses from additional resistance it
is possible to accept the expense or fuel cost. The expediency of an estimation
of such kind is obvious, as fuel consumption is unique precisely measured
parameter at the given design stage UAV, directly reflecting infringement of
aerodynamics of a surface, both in manufacture, and in operation [313].
Problem statement. In development of designs FV
and, accordingly, technologies of their manufacture always crucial importance
had constant increase in speeds of flight [312]. Growth of speeds of flight not
only causes of application of new, more and more heat-resistant materials (fig.
1), but also is accompanied still nearby important for development of the
production technology of tendencies [234].
Рис.
1. Growing of speeds of flight of
FV: 1)
for aluminum designs; 2) for titanium designs; 3) for designs from special steels;
4) for designs from special alloys; 5) for subsonic UAV
It
first of all concerns change of forms of units FV [316, 317]. Simple
rectilinear forms of surfaces of units of a glider in process of growth of
speeds pass in complex surfaces of double curvature. To the production
technology the total disappearance of cylindrical formations of fuselages is
essential almost at speeds from above М=0.85 and linear
surfaces of wings and plumage, since the speeds from above М=2.0. On change by their surfaces characterized by
complex enough laws of formation of the form come [315].
The proceeding increase in speeds (at least to М=3,5…4,5) causes toughening of requirements to
accuracy of the external contours, interfaced to serious problems in the field
of technology and designing of units [317].
Deviation
of elements of a surface from a theoretical contour, a raising of heads of
bolts, rivets, screws in a stream, steps, a roughness etc. on everyone concrete
FV or group of planes are appointed in specifications developers.
Maximum
deviations on elements of aerodynamic surfaces are defined proceeding from
admissible sizes of additional resistance
and flow conditions on various modes. As a rule, specifications on the
form and quality of a surface of the airplane provide division of units into
zones according to their importance in formation of a streamline stream. Typical
requirements to parameters of quality of surfaces UAV are in a range of 
мм [312].
To the
first zone carry surfaces of units to which increased requirements on quality
of a flow are shown. Higher requirements are accepted for a wing 
мм, less high ones for
a fuselage at great numbers 
and thickness of an interface. Conditions of preservation of a laminar
flow are put in a basis of requirements at small numbers 
as there is an opinion that roughness’s start to influence, if their
height exceeds a thickness of a laminar local layer [134].
Additional
resistance from a surface sinuosity is in sedate dependence on size of a
deviation of a surface and its position concerning a forward edge [35]. This
circumstance is considered in specifications at definition of zones of surfaces
of units.
Taking
into account similar reasons restrictions of size of local roughness’s of type
of ledges, ledges, cracks and fixture heads are generated 
мм [312].
Results of researches. By working out of
constructive and technological decisions it is necessary to define the
requirements shown to quality of object of manufacture and technological
processes, in particular to appoint maximum deviations of aerodynamic surfaces.
To
typical deviations of geometrical parameters of elements carry out next [312]:
1) smooth
deviations from the theoretical contour, measured by comparison of an actual
surface from the ideal. In practice as the ideal accept a surface set in one of
systems:
а) the measuring machine on the basis of mathematical model
of a surface;
б) reference surface in the form of its
breadboard model;
в) flat carriers of the form and the sizes at
use plaza and sample methods, means of spatial coordination, control templates
or assembly equipment;
2) eminence of one
part of a surface over another against a stream (so-called ‘step’) or on a stream
(‘ledge’). Geometrical parameters appreciate by results of excess measurements;
3) smoothness of
transition of one part of a surface in another (so-called ‘sinuosity’),
characterized in the length of a wave and amplitude. The sinuosity is
classified on character of display [321] - cylindrical or spatial. This kind of
an error of an external surface is defined by discrepancy of manufacturing and
design assemblage in which result there are the internal pressure covering all
sections or its parts. Local deformations occur owing to formation of
connections (rivets, welded seams). Sinuosity measure or concerning a base
line, a tangent to the maximum roughness (ruler), or by results of comparison
of an actual surface with ideal [312]. At a smooth deviation of contours on
sinuosity size on base
makes
where 
is scope of an error. At the set size of the admission
it is necessary to accept 
4) local excess of
elements of a surface in the form of acting (sinking down) heads of fixture. These
errors are registered by means of universal and special measuring instruments. The
basic geometrical parameters of deviations are the height 
and diameter 
[321];
5) cracks through
or without an exit between elements of a surface of the unit. These errors also
are measured by universal tools or special templates and characterized by the
relation of width 
to depth 
т.е. 
or the admission for width of a
through crack [321];
6) punching of an
external surface of the unit owing to defects of a surface. These errors are
limited by an equivalent aperture on area unit [312] (Fig. 1).
Fig. 1. The typical
geometrical parameters of a surface limited to admissions: 1) cylindrical
sinuosity; 2) spatial sinuosity; 3) crack (a backlash); 4) ledge against a stream;
5) ledge on a stream; 6) punching
Admissions
on a relative positioning of global surfaces of separate units and units among
themselves in this case are not considered.
Technique
of appointment of admissions on external contours of flying vehicles. For the purpose of definition of a generality of the constructive and
technological decisions accepted in specifications, revealing of the reasons
defining size of the admission have been analyzed specifications for more 30 FV
various types and appointment.
Fig. 2. Dependence
of change of the admission on a deviation from a contour of the unit from speed
Fig. 3. Dependence
of change of the admission on parameters of a sinuosity of a surface from speed
Fig. 4. Dependence
of change of the admission on parameters of a ledge of a surface from speed
Fig. 5. Dependence
of change of the admission on parameters of a crack of a surface from speed
Fig. 6. Dependence
of change of the admission on immersing parameters in a surface from speed
Fig. 7. Dependence
of change of the admission on parameters of a ledge from a surface in from
speed
On Fig.
2-7 the schedules constructed by results of statistical processing set in specifications
of admissions are presented.
Conclusion. The analysis of appointment of
admissions on external surfaces of units FV, practice of their appointment and
realization in manufacture allow to draw following conclusions:
1. Practically FV in
one interval of numbers
admissions on performance of geometrical elements of an external
surface are identical to all and decrease with growth 
Admissions for supersonic UAV
approximately twice it is less, than admissions for the subsonic
ones. The general feature is the task of various requirements for a wing,
plumage, a fuselage, gondolas and flows. The highest requirements to quality of
an external surface are shown to a wing, as to the unit creating carrying force.
2.
Necessity of decrease in weight and durability increase has caused
transition from a traditional modular design for power compartments to the
monolithic. Application of composite materials that has led to change of
conditions of realization of the admissions set on external contours extends. In
due to manufacture automation methods of the task and means of reproduction of
surfaces forming contour UAV will change. In these
circumstances of a condition of realization of admissions it is necessary to consider in two aspects: in design, i.e. according to the possibilities of formation of the set accuracy of contours put in a design, and in industrial and technological, i.e. according to possibilities of existing and perspective technological processes and the equipment providing set accuracy.
3. Experimental researches
of the isolated roughness are put in a basis of calculation of resistance from roughness’s
taking into account its site in the boundary layer. The roughness height is
defined by admissible size of additional resistance 
. Practical technique to an establishment of dependences and functional
communications between values of admissions and expenses by the generalized
criterion and consequently, and to a choice of economically optimum admissions,
still it is not defined unequivocally. Therefore for the generalized criterion
accept additional fuel consumption because of resistance of roughnesses, as
influence of additional resistance on speed almost slightly.
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