The project on development of UAV-system with remotely piloted aircraft of plane type for the Russian customer.

The project on development of a system with the remotely the piloted aircraft (RPA) of plane type on the request of the Russian customer was carried out in 2014.

The project consisted of 2 tasks.

Task No 1

Within the first task works were performed on definition of functional and nomenclature structure of the systems for UAV and ground part of complex with RPA in compliance with the tasks which are carried out by a the UAV system and assumed by the customer flight and technical as well as weight characteristics of RPA.

For the solution of this task the analysis of functional systems of foreign UAV analogs of plane type with the maximum take-off weight in the range of 900 – 2000 kg was carried out.

By results of the analysis the list of the considered UAV-analogs was made, attendees at the analyzed RPA systems are listed, the short description of functionality of each of the specified systems was given, all noted features of RPA are underlined.In total at this stage 9 unmanned aircrafts were analysed among which there were UAVs as RQ-1A/MQ-1A “PREDATOR” and MQ-1C “GREY EAGLE” from General Atomics company (USA), “HERON-1″ and “SUPER HERON” from IAI (Israel), “ANKA A” from Turkish Aerospace Industries (Turkey), etc.

pred-grey_eagle
Examples of the considered planes as prototypes.
The important consistent patterns determined during the analysis according to the specific characteristics allowing to design the RPA such as the specific weight carried to an engine power unit, the relative mass of payload, specific load of a wing and another were given in conclusions.

On the basis of the analysis of analogs of UAV-system it was offered of ECAR proposals to the functional view of a perspective UAV-system with RPA having the flight technical characteristics provided by customers.

Offers, both according to the list of functional systems of the aircraft, and by ground part of a UAV-system were created. Offers on separate units or systems in general, potentially suitable for installation on RPA or a ground part of the system, with the indication of critical characteristics were given (dimensions, weight, torques for drives, the size and type of supply voltage, etc.).On each system or the unit information on their function, in relation to the projected RPA was provided to the customer, offers on structure of systems, the description of operating modes, and also all the available information on the supply products and materials assumed to application were given.

Much less information on a ground part of a UAV-system was found. Nevertheless, proposals on ground control station which is a basic element of a ground part of a UAV-system, to the antenna terminal of a direct air bond and the antenna terminal of satellite communication, a complex of provision of take-off and landing of RPA in the manual and automatic modes and to a complex of land service were submitted.

Task No 2

Within the second task on the basis of the analysis of functional and physical structure of systems of a UAV-system with RPA, works on definition of optimum configuration of RPA were performed.The customer sets the task to work the concept of single-engine and two-engine options of RPA on the basis of preliminary tactical-technique characteristics. The two-engine option was considered as reserve option as had similar operation tasks, provided a touch the payload and time of barraging, and, respectively, losing to single-engine option on all cost indexes, but won that potentially could not have those serious restrictions on operation which any single-engine aircraft has.

The conceptual provisions which are been the basis for creation of both options and calculations which would prove the main geometrical, weight and characteristics of CG location for both options of RPA had to be result of this work. After that it was necessary to develop and by one option of a general view drawing and layouts for each option.

Because the payload and tasks specified in technical specification were identical to single-engine and two-engine options of RPA, the decision was made that in the course of development it is necessary to provide the greatest possible unification on configuration of compartments of the equipment between single-engine and two-engine RPA options. Single-engine UAV was taken for basic option.

Taking into account need of placement of the lengthy antenna of Airborne Radar of Side Review (ARSR) as basic element of payload for which it was necessary to create the most effective working conditions, in the first approach the scheme with the pushing propeller and a location of ARSR in forward part of a fuselage was chosen.

The following concept was proposed:

 

The main factor determining a shape of cross section of a fuselage was the nose zone of a fuselage where ARSR antenna, the antenna of satellite communication system, blocks of the airplane and payload equipment and a nose landing gear have to be placed at the same time.

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Fuselage cross-section in a zone of the ARSR, SCS installation and a wheel of a nose landing gear.
The geometry of a fuselage surfaces had to be such that in a zone of the radiating elements of ARSR antennas and the antenna of satellite communication external panels, whenever possible, were equidistant to working surfaces of these antennas, providing thereby the minimum losses by transfer and reception of a signal. Thus flat sites of a surface and sites of transitions from one to other surface with small radiuses, as probable zones of emergence of aerodynamic failures had to be excluded.

At a choice of aerodynamic configuration of RPA it was decided conscious to refuse any exotic aerodynamic schemes, nevertheless, work so “captured” ECAR participants of the project that they in an initiative order offered numerous alternatives.

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Alternative options of aerodynamic configuration.
At a choice of parameters of a wing the requirement for long time of flight at the minimum speed was a major factor. Besides parameters of a wing of planes prototypes were taken into account.In compliance with it the wing of big wing aspect ratio with the high-bearing profiles was chosen. The pushing propeller scheme allows to realize on such wing high values of lift-drag ratio and, respectively, big time of flight with the minimum fuel consumption.Some options of aerodynamic configuration of RPA, connected, generally with options of tail unit, conditions of its attachment to fuselage, and also options with the pulling and pushing propellers were considered.

It was noted that, despite prevalence (“Predator”, “Grey Eagle”, “Anka A”), all options with tail unit on a fuselage have an organic shortcoming – a small effective shoulder of tail unit.It is problematic to increase it because lengthening of tail part of a fuselage with shift of the engine results in need of lengthening and nose part of a fuselage, necessary for centering preservation back, and without shift of the engine there is a need of introduction to structure of engine-propeller group of a shaft with big length back that considerably complicates a design. Also other shortcomings inherent in this scheme were noted.

For two-engine option some aerodynamic schemes with the engines installed on a wing with the pulling and pushing screws were also considered.

It was noted that all schemes with the pulling screws and an arrangement of ARSR antenna in nose part of fuselage have that shortcoming that to have to do nose part of a fuselage longer to avoid influence of propeller on work of ARSR antenna.The option with placement of ARSR antenna behind a wing seriously complicates the load bearing scheme of fuselage since it is required to organize big on length cutout in highly loaded tail part of a fuselage.  

In addition to the analysis of schemes for each considered option flight technical characteristics, weights and CG location of the plane were counted. Thus the analysis of some options already at this stage showed that the received maximum take-off weight of the airplane exceeds settlement weight at others option, and sometimes and the proposed by customer weight.

On the basis of the above described layout studies and calculations the table of estimates of options by various criteria according to which for the subsequent detailed study together with the customer the choice was made: for single-engine the option is H-shaped scheme of the tail unit which is taken out on tail beams, and for two-engine option is the option with the pushing propeller were made. After a choice of the most rational schemes single-engine and the two-engine of RPA the following modifications of a design were carried out:

 

Aerodynamic schemes of a wing were defined by the main mode of RPA flight – barraging on minimum admissible speed. To such flight most there corresponds the rectangular wing of a trapezoid form with big aspect ratio. As material of a wing it was supposed to use composites based on a glass and carbon fabrics. High-lift devices of a wing were offered in the form of several sections of simple one-slot-hole flaps, one aileron and one dropped aileron. During the work four constructive schemes and schemes of installation of a wing on a fuselage were considered. Also the structure and load bearing schemes of tail unit, the scheme of installation of the power plant, preliminary design of the chassis and the scheme of retraction and opening, the scheme of partitioning and placement of units in the standard 40-foot sea container were similarly worked.

In addition, the scheme of cooling system of ARSR antenna and equipment blocks in a nose compartment of a fuselage was worked and submitted on configuration on request of the customer.

During the work on the two-engine option many design solutions received during the work on single-engine option were used.

Also as well as for single-engine option, the nose part of two-engine option of the plane has a beam-longeron design with non-loaded skin. The central part, where the fuel tank is placed, has a design like “semi-monocoque” with the loaded skin, the supported by longitudinal beams and frames. The tail part has a design like “monocoque” with several longitudinal beams and frames in a zone of tail unit attachment and is intended, first of all, for tail unit attachment and transfer of loads from it to the central part of a fuselage.

The beam-longeron structure and load bearing scheme of fuselage allows to use most fully internal volumes of a fuselage, and also provides easy access to the equipment.

Aerodynamic schemes of a two-engine option wing have many similar items to the scheme for single-engine that is defined by identical tasks and operational requirements. For this option three structure and load bearing schemes of the wing and the scheme of wing attachment to the fuselage were also considered.

Except T-shaped tail unit other options of tail unit were in addition considered on the request of the Customer at this investigation phase also: traditional scheme and V-shaped tail unit. However the analysis of the specified schemes didn’t show essential advantage in comparison with T-shaped tail unit which was accepted as the main option.

The report on the completed work contained a detailed list of the equipment of both options of RPA, calculations of weights and CG location.

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Lists of the equipment and calculation of weights.
In-detail described methodology of flight technical characteristics calculation for both options of RPA was provided to the customer.Calculation of speed and required engine power was carried out for conditions of horizontal flight at the maximum working height when performing a task during which the maximum quantity of payload equipment works.Missing data for calculations were looked for on various sources of information, extrapolated, being based on the available basic data.The required fuel capacity was defined on the basis of the previous calculations of engine power, the demanded flight time on an operating mode and provided by the engine manufacture the engine specific fuel consumption curves. It was proved that for both options of RPA the set time of barraging is secured with the maximum height of flight, and with a smaller height of flight or at its step change can even be exceeded.
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Pages of calculations.
Thus it was shown that the two-engine option has an essential gap between the provided and required engine power characteristics, in comparison with single-engine option at which required power was close to a limit of opportunities of the engine. Proceeding from it, for the two-engine option estimated calculations for option with the increased flight time were carried out (IFT-option).All materials were delivered to the customer and received a positive feedback. And single-engine option of the designed RPA was exposed by the customer in the form of table model on MAKS-2015 air show.
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Table model of RPA on the MAKS-2015.