Purpose -This study seeks to present the initial requirements for medium altitude long endurance (MALE) UAV design of an increased reliability. Design/methodology/approach -Shows and describes the successive design phases of PW-103 MALE UAV. Findings -The analysis of the performances of the PW-103 UAV, powered by either a main or an auxiliary engine, demonstrated that auxiliary power unit improved flight safety significantly. Originality/value -Successive MALE UAV configurations developed in the design process were aerodynamically more efficient than their predecessors.
This paper presents an evaluation of available aircraft types and demonstrates the lack of a low cost aircraft optimized for fighting forest fires, spreading viscous liquids for land reclamation and spraying pesticides over forest areas. It shows that among critical areas demanding special consideration are (a) the development of mathematical models for the water bomb-aircraft separation and the aircraft transient dynamics following separation, (b) the identification of parameters influencing the coherence of the water column and effectiveness of water delivery for fire fighting, (c) choice of aircraft configuration and (d) hopper configuration. Design and numerical analysis have led to the selection of the biplane as the best aircraft. The main aerodynamic characteristics for the selected aircraft have been computed by means of panel methods, the so-called modified Hess method for thick wings and bodies and/or the vortex lattice method for thin lifting surfaces. Different gaps and staggers and their influence on aerodynamic characteristics have been analysed. It has been found that shifting the lower wing rearwards (positive stagger) while keeping the angle of attack constant results in a small increase of induced drag and an almost constant value of the lift curve slope as well as an increase in the pitching moment curve slope. The increase of drag is disadvantageous, whereas the increase of the pitching moment curve slope means that the neutral point of stability is moved forward (a disadvantage from the stability point of view). The influence of the biplane configuration on downwash in the vicinity of the horizontal plane and aircraft dynamic stability is also discussed. Another important concept—developed at PZL-Okecie and presented in this paper—consists in using parts from existing aircraft. The pilot's cabin, the rear part of the fuselage with control surfaces and wings originate from the PZL-106 ‘Kruk’. This diminishes the cost of design and prototype construction as well as of the cost of aircraft production. It has been shown that an important cost factor in the operation of such a fire-fighting aircraft is the weight of the agent which may be carried for the same fuel consumption. This cost factor, representing the economical efficiency of a fire-fighting aircraft, has been computed and compared for a number of fire-fighting aircraft. The design under consideration (called the PZL-240 ‘Pelikan’) has the above-mentioned factor equal to 14, whereas the average value for other aircraft is about 8.
Purpose This paper aims to present and discuss the requirements for flying targets which sometimes are contradictory to each other and to perform a trade-off analysis before the design activity is started. It also aims to demonstrate conceptual and preliminary design processes using a practical example of PW-61 configuration and to show how results of experimental flight tests using a scaled flying target will be described and analyzed before manufacturing the full scale flying target. Design/methodology/approach An important part of the paper consists of the selection of tailplane configuration of the flying target UAV to protect some expensive on-board systems against serious damages and to obtain a sufficient dynamic stability, independently of the amount of the petrol in fuel tank. Inverted V-tail, U-tail and H-tail configurations were considered and compared both, theoretically and in-flight experiments. Findings Flight dynamics models and associated computational procedures were useful both in a preliminary design phase and during the final assessment of the configuration after flight tests. Selection of the tailplane configuration for the flying target UAV is very important to protect some expensive on-board systems against serious damages and to obtain a sufficient dynamic stability, independent of the amount of the petrol in fuel tank. Practical implications Flying targets should be speedy, maneuverable, cheap, easy in deployment and multi-recoverable (if not destroyed by live ammunition), must have relatively low take-off weight and an endurance of at least 1 h. This paper can be useful for proper selection of requirements and preliminary design parameters to make the design process more economically effective. Originality/value This paper presents very efficient methods of assessing the design parameters of flying targets, especially in an early stage of the design process. Stability computations are performed based on equations of motion and are supplemented by flight tests using the scaled flying models. It can be considered as an original, not typical, but very practical approach because it delivers lots of data in the early design stages at relatively low cost.
This paper presents the development of an aerobatic aircraft including the influence of platform configuration on performance, elegance and safety of aerobatic manoeuvres. Several aircraft of different wing loadings were compared and the reduction of wing loading on manoeuvring slowdown was studied. Advantages of the biplane configuration influence on the desired properties of aerobatic aircraft were discussed in detail. Results of numerical simulations obtained for HARNAS-3 aircraft were compared with corresponding results received for EXTRA 300 aircraft. Some original design solutions for HARNAS-3, enabling easier control of this aircraft during the manoeuvring phase, were presented. Numerical simulations, wind tunnel tests and free flight experimental results for scaled-down HARNAS-3 models were presented, compared and discussed.
The article presents the concept of the SKORPION II anti-tank and antisubmarine system, which could be used as a universal system of destruction of ground and surface facilities or as a support system for air reconnaissance. The unique character of the Subsonic Anti-tank Scoring System SKORPION II and the lack of analogous solutions on the defense market make it difficult to determine the relationship of costs to other analogous projects. A certain approximation of the cost scale may be the comparison of SUAS with approximate prices of modern weaponry, e.g., Predator (single-engine, unmanned reconnaissance aircraft with control and data reading system)-USD 25 million, this price many times exceeds the estimated value of the system (estimated at PLN 1 million) SKORPION II. The cost of purchasing similar products usually does not take into account the fact that, after their purchase, the Polish user has no possibility of its development, because he has neither the knowledge nor the documentation enabling production of his own products of this class. The SKORPPION II system, which is the Subsonic unmanned anti-tank system, allows the levelling of the potential enemy's armour and should only be produced by Polish companies, which could provide a Polish presence outside the US and Israel.
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