Swept Wing Question

[ATPMBA]

I have been reading Davies book, “Handling the Big Jets”. He mentions a swept wing “tricks” the airflow into thinking it is flying at a slower speed which delays the shock wave. My question, is the airfoil the designers selected for the aircraft perpendicular to the leading edge of the wing or is it parallel to the longitudinal axis of the aircraft?

[John Farley]

Both aerofoils would be considered by an Aerodynamicist to be the same with the one parallel with the airflow merely having a lower thickness chord ratio compared to the section taken perpendicular to the leading edge.

If that seems strange then if you check an aircraft spec you might well find comments like "the wing uses a 12% Clark Y or 10% Clark Y" where Clark Y specifies the section.