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.


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    Title :

    Aerodynamic, dynamic and conceptual design of a fire-fighting aircraft


    Contributors:
    Goraj, Z (author) / Frydrychewicz, A (author) / Ransom, E C P (author) / Self, A (author) / Wagstaff, P (author)


    Publication date :

    2001-03-01


    Size :

    22 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English





    Aerodynamic, dynamic and conceptual design of a fire-fighting aircraft

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