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Comparison of Generalized Approximate Cruise Range Solutions for Turbojet/Fan Aircraft
... In addition to the aircraft manufactures' published speed and maximum range for a particular model, much research has been done to try to improve the advertised performance of cruise flight. For instance, the research in [26] and [12], focused on the flight conditions that could increase the cruise range performance. ...
... In [27] and [12] variations of Breguet equation are used for range. The derivation of this range equation starts with the following definition of lift-to-drag ratio: ...
... where w is the ratio of the current aircraft weight to the aircraft weight at the start of cruise, E m 0 is the maximum lift-to-drag ratio defined by [12]: ...
With rising fuel costs there is an initiative to conserve fuel during fight. Several methods have been proposed to calculate an optimum speed to y during cruise flight to maximize the range of a particular aircraft. This paper compares 11 of these methods using the same aircraft model and discusses how to implement these techniques in an autothrottle. Alternative implementations also include adding the algorithm to the Flight Management System to use during flight planning, or to including it in the databases to use during dispatch calculations. The results show that the speeds calculated by these methods are more fuel efficient than the usual cruise operating speed.
Since flying at the optimum speed is not always practical, this research also looked at the design of the industry autothrottle. Improvements to the industry autothrottle speed control law were implemented to see if improvements to fuel consumption could be achieved at any speed. The results show that the improvements proposed did not improve the fuel consumption during the conditions simulated.
... Equation 3 includes the range parameter K, the best representative of the overall airplane performance. 6,[18][19][20] Due to size and range effects, this parameter exhibits an inverse relation with respect to range. The last unknown in Eq. 1 (the payload is assumed to be determined by the market and, consequently, perfectly known) is the reserve fuel; required for any contingency or to reach a suitable, alternate airport. ...
Air routes are mainly determined by the interaction of geographical, political, economic, and social factors. On another side, airlines use their aircraft for a diversity of missions. Because of both factors the actual utilization of transport aircraft is well inside the payload-range envelope, which means that the design features are oversized for most flights. The objective of this paper is to evaluate the savings that could be achieved if transport aircraft were designed for shorter ranges: i.e., closer to the actual utilization pattern. In this design scenario the maximum takeoff weight and the operating empty weight would be remarkably reduced. This would lead to a reduction in aircraft price, trip fuel, maintenance cost, landing and navigation charges, and environmental impact. Direct operating cost is used as the figure of merit of the reduced-range approach.
Approximate cruise range solutions are introduced for the constant altitude – constant high subsonic speed flight of turbojet/fan transport aircraft with cambered wing design. The variation of the specific fuel consumption with Mach number is also considered in derivation of the approximate solutions. The method aims at estimation of the cruise range of aircraft during conceptual or preliminary design phase. An application of the solutions is also presented.
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