Patent ID: 7556221

Claim:
A method of protecting an airfoil from undue ice accumulation during flight, said method comprising delay-rectifying steps for removing delay-induced ice accumulation and routine-deicing steps performed after the delay-rectifying steps; wherein the delay-rectifying steps and the routine-deicing steps are performed by an electrothermal device comprising a parting strip (PS) and at least a first set of spanwise-aligned deicing zones, the parting strip (PS) being positioned to heat the leading edge region of the airfoil, the first zone set comprising an upper fore zone (UF 1 ), a lower fore zone (LF 1 ), an upper aft zone (UA 1 ), and a lower aft zone (LA 1 ); wherein the delay-rectifying steps comprise: for a first time period (t 1 ) continuously heating the parting strip (PS), continuously heating the first upper fore zone (UF 1 ), continuously heating the first lower fore zone (LF 1 ), not heating the first upper aft zone (UA 1 ), not heating the first lower aft zone (LA 1 ), wherein the routine-deicing steps comprise: continuously heating the parting strip (PS), intermittently heating the first upper aft zone (UA 1 ), intermittently heating the first lower aft zone (LA 1 ).