A method of determining an inlet total air pressure (P1) of air at an air inlet of an aircraft engine , the method comprising: determining , at a computing device , a first parameter (P1IN) indicative of a first inlet total air pressure (P1IN) at the air inlet ; executing, at the computing device , a sequence that includes: determining , at the computing device , a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining , at the computing device , a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining , at the computing device , a static air pressure (PS1) at the air inlet ; determining , at the computing device , an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet ; generating , at the computing device , a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure (PS1); and substituting, at the computing device , the subsequent parameter (P1R) for the first parameter (P1IN); executing, at the computing device , at least one additional instance of the sequence with the subsequent parameter (P1R); and outputting, at the computing device , the subsequent parameter (P1R) as the inlet total air pressure (P1). determining , at a computing device , a first parameter (P1IN) indicative of a first inlet total air pressure (P1IN) at the air inlet ; executing, at the computing device , a sequence that includes: determining , at the computing device , a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining , at the computing device , a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining , at the computing device , a static air pressure (PS1) at the air inlet ; determining , at the computing device , an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet ; generating , at the computing device , a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure (PS1); and substituting, at the computing device , the subsequent parameter (P1R) for the first parameter (P1IN); determining , at the computing device , a mass air flow (W1C) passing through the air inlet based on the first parameter (P1IN); determining , at the computing device , a Mach number of air passing through the air inlet based on the mass air flow (W1C); determining , at the computing device , a static air pressure (PS1) at the air inlet ; determining , at the computing device , an air pressure ratio (P1R/PS1E) based on the Mach number, the air pressure ratio (P1R/PS1E) defined as a revised inlet total air pressure (P1R) over an estimated static air pressure (PS1E) at the air inlet ; generating , at the computing device , a subsequent parameter (P1R) indicative of the revised inlet total air pressure (P1R) based on the air pressure ratio (P1R/PS1E) and the static air pressure (PS1); and substituting, at the computing device , the subsequent parameter (P1R) for the first parameter (P1IN); executing, at the computing device , at least one additional instance of the sequence with the subsequent parameter (P1R); and outputting, at the computing device , the subsequent parameter (P1R) as the inlet total air pressure (P1). <EOS>