Low-Order Method for Predicting Aerodynamic Performance Degradation Due to Ground Icing

Abstract

Alow-ordermethod to computethe degradation in the maximum lift coefe cient of an aircraft due to distributed surfaceroughnesshasbeendeveloped.ThealgorithmisappliedtotheFokkerF28Mk1000,anaircraftinvolvedinan accidentinwhichgroundicingwasdeterminedtoplayasignie cantrole.Themethodconsistsoftwocomplementary portions. The e rst uses a low-orderpanel method to computethequasi-steady aerodynamiccharacteristics, in and out of groundeffect,ofthecompleteaircraftgeometryincluding one- ortwo-elemente aps,a boundary-layerfence, nacelles, and a horizontal tail. The numerical model then, in the second portion, generates an engineering estimate of the maximum lift coefe cient for the aircraft cone guration. The method is based on the assumptions that the pressure difference between the suction peak and the trailing edge of an airfoil is a maximum at the maximum lift coefe cient and that the condition in which one spanwise station of a wing in a stripwise analysis violates this maximum pressure difference rule is the point at which the maximum lift of the entire aircraft is generated. The application of the pressure difference rule is modie ed to account for the presence of the boundary-layer fence and can estimate (on the conservative side ) the effects of distributed surface roughness on the maximum lift coefe cient using an appropriate maximum allowable pressure difference.