ESTIMATION OF WING WEIGHT IN CONCEPTUAL DESIGN PHASE FOR TACTICAL UNMANNED AERIAL VEHICLS

New formula for wing weight estimation, in conceptual design phase is derived for a tactical unmanned aerial vehicle (TUAV). Formula is derived by analyzing existing UAVs of the weighs from 100 to 500 kg, and which have similar characteristics. The materials suggested for UAV weight design are aluminum alloys and aluminum based composite materials. Software tools are developed in Matlab to facilitate takeoff and component weight calculations. The least square method is applied to analyze statistical data in order to develop trend functions which correlate TUAVs empty weight and takeoff weight. Existing formulas, developed for general aviation, for wing and takeoff weight estimations are applied to TUAV and promising one are selected and adjusted to TUAV conceptual design phase. Wing weight is related to geometrical parameters, maximum speed, and takeoff weight of the TUAVs. All existing and newly developed formulas are applied to typical TUAV example to validate it applicability.


Introduction:
UAV's are defined as aircraft which flies without pilot inside it.It can be released into the air in several ways such as ordinary runway, by hand, by launcher, by rocket, from bigger airplane, or any other convenient mean.UAV sizes start from insect size to thousands of kilograms according to its mission, altitude, endurance, range, and payload carried.Tracking and controlling of the UAV's are done automatically or by wireless connections.It also can fly fully autonomously by computer programmed mission, starting from the takeoff moment until it returns controlled all time by computers inside it [1].Because UAVs have high-aspect-ratio wings and fly in low-density conditions, often at low speeds; airflow is characterized by low Reynolds Since conceptual design phase cost least, it is wise to perform it thoroughly and to postpone crucial decisions as late as possible since all subsequent phases are continuation of this phase.This will increase the cost of this phase but since its share in total cost is usually less than 5% increase is not significant, but can reduce significantly the cost of subsequent phases.It cannot be stressed enough that outcome of the conceptual design phase greatly depend on initial weight estimation of the UAV.This work will contribute to this problem by deriving equation for weight estimation.

Materials and Methods:
Methods of weight estimation are experimented for number of various kinds of TUAVs.
All of the dimension parameters of the wing geometry are presented in Comparing the outcome of the equation and the value of wing weight that we got from the figure, it is clear that there is approximately same.

Torenbeek method:
This equation applies to light transport aircrafts with takeoff weights less than 5600 kg. ( 4),( From Figure (4), fitting line indicates that the wing weight fraction for 100 kg is 8.5% and increased to reach 10.3% at 500 kg.For our aircraft which weighs 220 kg takeoff weight the wing weight fraction is 13.24 %.
By substitution in Torenbeek equation for parameters values that we got for aircraft which weighs 220 kg, the result is as follow:

Kundu method:
Kundu equation is derived and modified from general equation published by SAWE: [7].
The results of wing weight fraction (Ww/Wo) of Kundu equation according to the fitting line range between 18% at 100 kg and 22 % at 500 kg takeoff weight.
By substation in Kundu equation for takeoff weight and the other parameters we got before for our aircraft such as, wing area, aspect ratio, fuel fraction, thickness to cord ratio, taper ratio, and sweep angle, the result is as follow: numbers.Aerodynamic properties of such flying object are significantly different from properties of general aviation aircrafts or ultra-light aircrafts.New category of flaying vehicles need extensive research in low Reynolds number flight regime, searching for shapes of sufficiently high lift coefficients and reasonably low sensitivity to flow separation.The first sizing of the wing was done using the results of the parametric analysis and its design was a highly iterative process.The main design driver was to minimize the weight consideration, which led to some compromises.Models of conventional tactical UAVs weights between 100 to 500 kg are chosen for wing weight estimation.The parameters values of these UAVs are input to Matlab program to get the result on chart; the results are evaluated and compared with the results of calculated equations for UAV weights 220 kg as takeoff weight.Wing weight represents about 17-27% of the empty weight [2].
Figure (1) Raymer wing weight estimation Usaf equation we can see that the parameters of the equation are moderately used, so that the equation outcome is not affected dramatically by changing any parameter individually.The equation basically depends upon the fixed number (96.948), we can see that clearly in figure (2).The fixed number is very big for this equation.

Figure ( 5 )
Figure (5) Jay Gunlach wing weight estimation shows Wing weight from Kundu which represents 27.7 % of W o .