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Flight Parameters

FP02.gifThis is the total aircraft weight in ounces or grams. Stored in Planes database. Don't forget to adjust the weight if you change motors. This weight should be appropriate for the number and type of cells you have entered, since the program adjusts the weight with cell changes. ElectriCalc is not ambitious enough to keep up with the weight of hundreds of motor/gearbox combinations (or the weight of different props for that matter!).

FP03.gifThis is the wing loading, or ratio of plane weight to total wing area expressed in ounces per square foot or grams per square decimeter. This value is calculated and not stored in any database. If you enter a value for wing loading, the Plane Wt. and Wing Area will "light up". Double-clicking on either of these will recalculate that value to correspond to the specified loading. This is useful for things like determining a target weight for a model when you know the wing area and the desired wing loading Tolerable wing loading goes up as the size of the plane increases. 18 oz. per sq. ft. is good for "Speed 400" size planes. 24 oz. per sq. ft. is good for "40-size" planes. 30+ oz. per sq. ft. can be tolerated in the very large models. Biplanes require lower loading because the two wings in close proximity are not as efficient.

FP04.gifThis is the total wing area in square inches or square decimeters. Stored in Planes database. Wing area is normally considered to include the area over/under the fuselage. The area of a wing with non-parallel leading & trailing edges can be figured by taking the width at the center plus the width at the tip and multiplying by the length (perpendicular to fuselage) from the center to the tip.

FP05.gifThis is an aerodynamic constant used in calculating the thrust required to move the plane through the air at a given speed. Stored in Planes database This number can be entered here or a reasonably good estimate can be quickly made by selecting C drag from the menubar.. Wing struts and wires add a lot of drag. A good aerodynamics text is "Model Airplane Design and Performance for the Modeler" by Howard Chevalier. Reduction of drag in electric models is quite important. Biplanes in particular give disappointing flight times. Thick airfoils, fat fuselages, struts and wires should be avoided or minimized wherever possible. Remember that wing loading also contributes to drag.

FP06.gifThis is an alphanumeric representation of the motor configuration. Stored in Planes database. Information cannot be entered directly here, but can be selected by clicking the raised panel or the Multi menubar selection. Two motors in parallel have the same Kv , half the Rm , and twice the Io . Two in series have half the Kv, twice the Rm, and the same Io. Etc, etc.

FP07.gifThis is a description of the selected plane. Stored in Planes database.

FP08.gifThis is the Planes database control. If you click the big button, you jump to the Planes database. The smaller buttons step you back and forth through the database. Use CTRL_S as a shortcut to access the database. This selects the plane that is displayed. This includes the cell count, wiring resistance, prop diameter & pitch, weight, wing area, Cdrag, and motor configuration. It also selects a cell, motor/gearbox, and prop from their respective databases.

FP09.gifThis is the rate of climb at the maximum climb angle possible at the current throttle and speed slider settings. Climb rate drops off dramatically with speed because the drag increases as roughly the square of the speed, and the available thrust drops with increasing speed. The climb rate has a peak between stall and max speeds that is related to the lift, drag, and thrust relationships.

FP10.gifThis is the maximum sustainable climb angle at the current throttle and speed slider settings. It corresponds to the climb rate above. Physically, this number is derived from the amount of thrust remaining to lift the plane after subtracting that necessary to pull the plane through the air at the set speed. Climb angle (sustained) drops off dramatically with speed because the drag increases as roughly the square of the speed, and the available thrust also drops with increasing speed

FP11.gifThis is the maximum rate of climb obtainable at the current throttle setting, independent of the speed slider. It is obtained at the angle indicated. The steepest climb angle does not yield the fastest climb.

FP12.gifThis is the theoretical total height at the max climb rate for the indicated minutes. Although this number is calculated by multiplying the calculated max climb rate times the calculated minutes, it's really just a relative measure. It does not integrate this number over the discharge profile of the battery pack.

FP13.gifThis is the theoretical minimum flying speed using a rule of thumb based on the wing loading. It is only an approximation but normally close enough. This number is the standard rule of thumb of 3.7 times the square root of the wing loading in oz. per sq. ft or grams per sq. dm.

FP14.gifThis is the calculated maximum plane speed in level flight based on the thrust of the prop(s) and the drag of the plane. This is the speed where the thrust and drag curves cross. Climb rate is zero because there is no thrust available to lift the plane.

FP15.gifThis is a magic number computed by ElectriCalc to give you a measure of flying time assuming mild maneuvers and good throttle management. This number is based on sustaining an average climb rate and speed related to the rate-of-climb vs. speed curve. This calculated speed is then obtained by backing off the throttle and then calculating the run time. It's just a guideline, not something to lose sleep over.

FP16.gifThis ‘speedometer’ control sets the speed at which you want the performance calculations made. More speed . . . less climb, more drag . . . less thrust, etc. Clicking the arrows steps 1% and clicking in the white area steps 5%. Try stepping the speed from stall to max and watching the rate of climb first increase and then decrease.