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Aviation History
1985
1985 - 0038.PDF
ESTIMATED OPERATING COST OF TYPICAL AGRICULTURAL AIRCRAFT Type Aircraft Engine Cost* ($—1984) Engine power (kW) Fuel flow (kg/hr) Depreciation ($/yr) Interest Taxes and licence Hangarage Insurance Total fixed cost Fuel and oil (S/hr) Maintenance/overhaul Total variable cost Total operating cost $/hr—200hr/yr —400hr/yr —600hr/yr M-18A AS2621R 180,000 746 91 18,900 17,010 5,670 2,970 10,913 55,463 71-5 69-7 141-2 418-5 279 8 233 6 " Estimated price. Will vary with optional equipment Piston AT-301A R.1340 100,000 448 85 10,500 9,450 3,150 1,650 7,463 32.213 66-8 46 8 113-6 274-6 194-1 167-2 Fixed-wing Thrush R.1340 120,000 448 85 12,600 11,340 3,780 1,980 8,325 38.025 668 46-8 113-6 303-7 208 6 176-9 Contact manufacturer for detailec Turbine T-Thrush PT6A-34 400,000 559 155 42,000 37,800 12,600 6,600 20,400 119,400 63 1 54-6 117 7 714-7 416-2 316 7 figures. AT-400 PT6A-15 275,000 507 145 28,875 25,988 8,663 4,538 15,009 83,072 59-1 48 5 107-5 522 9 315 2 2460 Rotary Turbine Sok>y/Bell47 AII.250-CB20 225,000 313 120 29,531 21,262 7,088 3,713 12,853 74,447 48 9 71-9 120 7 4930 306-9 244-8 spent treating isolated edge areas of the spray zone. These last two are compli cations, and may be neglected depending on operational circumstances. There is agreement on the phases of flight con sidered, but the emphasis made, and the way of calculating their duration vary. This can affect the conclusions reached about the best way to handle a particular mission. The time formula is only one of several possible logistic formulae. Some can be defined which relate to the consumption of other resources (fuel and oil, duty hours, airframe, and engine overhaul life). In airline operations, three main items are always determined for costing—block fuel, corresponding block time, and the payload available over the route. Since operating cost parameters are approximated, errors creep in. All methods suffer this problem; over-simplification worsens the situation. Operating costs have attracted much less attention from researchers, but every ag operator has his rule-of-thumb guide lines to apply for quotations and esti mates. Only two fully documented cost methods seem to have been published, one by Akesson and Yates to complement their logistic formula, and a more recent one by F. W. Gobetz of the United Tech nologies Research Centre. The first method, extending recommen dations by Desmond Norman, classifies aircraft into three fairly arbitrarily derived cost groups. Fixed and variable costs are separately listed, but no truly independent variables are used; operating costs depend only on the price group into which the aircraft falls. No account is taken of the ability of designers, manu facturers, and operators to influence fuel efficiency, maintainability, and unit cost, and the resulting operating cost levels. Gobetz's more recent and substantial work applies a more practical approach. He considers the actual aircraft price and the installed power—fixed or rotary-wing aircraft, and piston or turbine engine. This is more like the practice for transport and business aircraft operations, but the costing methods remain crude. It is important to distinguish between fixed and variable costs, the short-run costs associated with the possession of fixed assets (such as aircraft, and the means to operate them), and the costs of actually using them (which are avoidable if they are not used). Both the methods reviewed cope with this important distinction, the first method only crudely. Both are deficient since they oversimplify variables to an hourly cost. Maintenance and overhaul costs will depend in practice as much upon the number of flight cycles as upon hours flown. Fuel consumption will depend on the pattern of the operation and the time spent in each phase. Among fixed costs, the main elements are aircraft and spares depreciation over their useful life (seven to 12 years), interest charges (based on the capital cost), operator taxes and licence fees, hangar and airstrip charges, and insur ances. The variable costs are basically fuel and oil, and piloting. It is not usual at this stage to include the cost of ground-support facilities and staff. Obviously these and such items as crew expenses and administrative overheads need to be covered in the contract price. Provision of the chemical load is usually the responsibility of the party commis sioning the contract. The accompanying table (derived from the work of Peter Jackson) gives an idea of the hourly cost levels achievable with current production aircraft. The effect of varying annual aircraft utilisation is shown. Fixed costs tend to dominate the equations because of the low utilisations achievable, owing to the seasonal nature of spraying operations. The operator moves his fleet and workforce as the year progresses. The pattern tends to be one of a few periods of intense activity, inter spersed with longer, inactive periods when major overhaul work can be done at base. Most Western operations tend to be small and very specialised, with relatively few aircraft. Their financial performance is not always satisfactory and the laws of the business survival apply. Despite (or perhaps because of) the uncertainty, such companies tend to be fairly efficient, and offer excellent value for money. The motivation and enthusiasm engendered by the small-company atmosphere results in efficiency more than compensating for the small scale of operation. There are, perhaps, three main issues under debate in ag aviation. The choice between fixed- and rotary-wing (prin cipally concerning size and location of the areas to be treated and the surrounding terrain); the question of aircraft size and load carried (whether economies of scale can be achieved in practice); and the ideal means of propulsion (turbine or piston). Helicopters clearly have advantages with the very small field sizes often experi enced in Western Europe. They can be operated from points close to the spraying site, reduced ferry times compensating for lower speed and payload capacity. In diffi cult terrain, areas obstructed by trees, buildings, or power cables, the low speed and greater manoeuvrability is a positive advantage. For certain crops, rotor down- wash helps to distribute the chemicals more thoroughly and consistently, this « reducing the amount required. Helicopters are particularly suitable for applying ultra-low volume (ULV) chemicals, the use of which is an increasing trend. The open plains of the US Mid-West and Eastern Europe require larger, faster, and more productive fixed-wing aircraft, which can transit rapidly to distant sites ' and spray large areas economically. Increasing the aircraft size does bring genuine economies of scale. Only one pilot is needed, whether in an Agtruck (with a 280 US gall hopper) or in a Fieldmaster (700gal capacity). DC-3 size aircraft have been used for crop spraying; the US Forest Service includes converted DC-6s and DC- ' 7s. The use of aircraft with high work performance is often the policy in Eastern Europe, where the Antonov An-2 remains in widespread use. The point about turbine engines is that although they more than double the cost of a typical ag aircraft, they produce substantial benefits in general areas. The duty cycle of spraying is particularly arduous and actual engine overhaul lives are much shorter than normal. They offer advantages of easier handling, reduced vibration and pilot stress, less risk of fire on ground impact, and faster transit to the spray site. The greater power of turbines contributes to a greater lifting capacity. Turboprops have a greater fuel con sumption than equivalent piston units, but this is offset by a lower fuel price and often better availability. There is likely to be a move to more turbine powered and larger aircraft, and greater sophistication in the planning and costing of ag operations (e.g. the use of , microcomputer-based models). The basic shape of ag aircraft as dictated by pilot safety considerations, may not change unless the industry turns to remotely ' piloted aircraft. r Agricultural aviation is a complex and intriguing business, combining biological \ sciences with what some might regard as f the "black ' art" of aeronautics, and becoming ever more technical. If Man ever r does become self-sufficient in food, ag aviation will play a major part. This will "' be due in equal measure both to the efforts * of the pioneer ag fliers and to those of a new generation of "bio-aviators". D Genuine economics 36 FLIGHT International, 5 January 1985
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