The method of calculation of the interferential aerodynamic characteristics of stores, which are separated from the aircraft

Аuthors

Pravidlo M. N.¹, Korizhin O. V.^2*

1. Toropov Machine-Building Design Bureau "Vimpel", 90, Volokolamskoe shosse, Moscow, 125424, Russia
2. Russian Aircraft Corporation «MiG», 6, Leningradskoe shosse, Moscow, 125171, Russia

*e-mail: olegkorizhin@gmail.com

Abstract

The development of the effective aviation armament system is one of the important issues that arise during the design of new and modernization of the existing military aircraft. In addition to weapon control system, sighting systems, etc. the aviation armament system includes the weapon launchers with the munitions that are installed on them. A multitude of technical decisions, which are aimed at the safe separation of the munitions from the delivery aircraft, is implemented to provide for the usage of aviation weapons. In general the safe separation refers to fulfilling the following requirements during the store flight in the vicinity of the delivery aircraft after its release from the launcher:

 - retention of the store spatial stability during its flight after the separation from the aircraft (for stores with a control and targeting system);
 - absence of thermodynamic impact from the exhaust jet of the store engine on the functioning of the airplane propulsion system, airplane structural elements and other stores that are installed on it.

Technical decisions of integrated nature are required to provide for the munitions release. Such decisions define the essential parameters of all objects that make up the munitions separation system, namely, the «delivery aircraft — launcher — munition» system. These parameters include the following [2]:

 1) for the delivery aircraft: linear and angular coordinates of the store in transport position;
 2) for the weapon launcher: the increments of the linear and angular coordinates and velocities of the store, which take place during its movement on the launcher;
 3) for the controlled stores: configuration and settings of the stabilization system during the flight in the vicinity of the delivery aircraft; the preliminary deflections of the tales and the overload during the initial movement of the store away from the delivery airplane (the values of these parameters are assigned by the control system after the store separation from the launcher).

Violation of the boundary values of the above- mentioned groups of parameters can result in aircraft or store damage, which may cause an accident or store mission failure. The separated store may become unstable, which can lead to mission failure or collision with other stores (during the separation of several stores) or adjacent airplanes of the operations group.

Technical decisions, which are aimed at providing for the usage of aviation weapons, are checked with the help of simulation of the store launch and subsequent analysis of store spatial movement in the vicinity of the delivery airplane. At that an important role is played by the reliability of interferential aerodynamic characteristics of the store-airplane system in the vicinity of the delivery airplane and characteristics of the isolated separated store.

Interferential characteristics in transport position and in the aircraft vicinity generally depend on a wide range of parameters such as:

 - the position of the store relative to the airplane  linear and angular coordinates of the relative store position;
 - the variant of munitions installation N_I, the presence of suspended loads on adjacent stations or the proximity of the aircraft structure;
 - the aircraft angles of attack and sideslip â during the store launch;
 - speed and altitude of aircraft flight, which is represented by Mach number M.

The dependence of the interferential coefficients can be formally represented by the following function:

Thus the problem of determination of the interferential characteristics of the cargo-airplane system is multifactorial and includes all of the following: the design parameters, the location of the load on the airplane, the environmental parameters, the altitude and speed of airplane flight.

The described method allows the designers to determine the interferential aerodynamic characteristics of the delivery airplanes and stores of various shapes at early development stages without conducting the wind tunnel experiments. This can reduce the cost of wind tunnel tests and time, which is required for the optimization of the store aerodynamic configuration and its placement on the airplane, significantly.

The results, which were obtained by using the described method, can be used to calculate the parameters of separation of loads from the aircraft and separation safety evaluation.

The data, which was processed by using multidimensional (multivariate) interpolation, allows the researcher to analyze the interpolated dependencies based on all the factors that influence the interferential coefficient values. 

Keywords:

aerodynamic characteristics, safe-detachment, system of gas-dynamic analysis, CFD, multidimensional interpolation, solid modeling

References

1. Chechik D.L. Vooruzhenie letatelnyh apparatov (Aircraft weapons), Moscow, MAI, 2002, 164 p.
2. Pravidlo M.N. Vestnik Moskovskogo aviatsionnogo instituta, 2010, vol. 17, no. 4, pp. 17-25.
3. Pravidlo M.N. Elektronnyi zhurnal «Trudy MAI», 2010, no. 37, available at: http://www.mai.ru/science/trudy/ eng/published.php?ID=13418 (accessed 21.04.2010).
4. Dean John P., Clifton James D., Bodkin David J. Computational Stability and Control Analysis of Fighter Aircraft. HPS Insights, 2009, no. 09, pp. 8-10.
5. Babcock Judson. Applied Computation Fluid Dynamics in Support of Aircraft, Store Compatibility and Weapons Integration, 2007, pp. 21-27.
6. MATLAB HELP. MathWorks^®. Gridded Interpolant class, available at: http://www.mathworks.com/help/ matlab/ref/griddedinterpolant-class.html (accessed 08.02.2014)
7. Atmosfera standartnaya. Parametry. GOST 4401-81 (Standard atmosphere. Parameters. All-Union State Standard 4401-81), Moscow, Standarty, 2004, 180 p.