ESDU 79015
Undercarriage drag prediction methods.
Abstract:
ESDU 79015 gives two methods for estimating the drag; one is an approximate method for use at the project stage when the geometry is not fully defined and gives the overall drag, and the second is for use when the geometry is known and sums the individual contributions of each component with allowance for interference. For the first method a correlation of flight measured drags on civil transports led to a simple equation with an empirical constant whose value depends on whether flaps are deflected or not. For the second method graphs are provided by which the drags of wheels, struts, undercarriage bay and undercarriage doors can be predicted and the interference effects of multiple wheels and struts, and of flaps and wing with the installation, can be estimated. The data can be used with retractable or fixed undercarriages for which data deal with the drag of streamlined struts and spats. Comprehensive worked examples illustrate their use.Indexed under:
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Data Item ESDU 79015  

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This Data Item contains 16 interactive graph(s) as listed below.
Graph  Title 

Figure 1a  Drag coefficient ratio for wheels. Re_{w} < Re_{wcrit} 
Figure 1b  Drag coefficient ratio for wheels. Re_{w} >= Re_{wcrit} 
Figure 2  Interference factor on wheel drag due to presence of a plane surface 
Figure 3  Drag coefficient for struts of rectangular section 
Figure 4  Factor on strut drag due to inclanation of strut 
Figure 5a  Interference factor on strut drag due to presence of another strut. Factor for downstream strut of pair in series 
Figure 5b  Interference factor on strut drag due to presence of another strut. Factor for upstream strut of pair in series 
Figure 5c  Interference factor on strut drag due to presence of another strut. Factor for struts sidebyside 
Figure 6a  Interference factor on strut drag due to presence of a plane surface. H_{s}/d_{s} =< 0.7 
Figure 6b  Interference factor on strut drag due to presence of a plane surface. H_{s}/d_{s} > 0.7 
Figure 7  Drag coefficient for undercarriage bay cavity 
Figure 8  Coefficient in equation (4.13) for estimating installation drag factor due to wing thickness 
Figure 9  Coefficient in equation (4.14) for estimating installation drag factor due to flap deflection 
Figure 10  Interference drag coefficient for streamline struts placed sidebyside 
Figure 11  Coefficient in equation (5.10) for estimating interference drag at junction of two streamline struts 
Figure 12  Coefficient in equation (5.11) for estimating interference drag at junction of a streamline strut and a plane surface 