Gas turbine engine flange arrangement and method for retrofitting same

The gas turbine engine arrangement (10) comprises a compressor (11), a combustion chamber (12) and a turbine (13) connected one another. A casing (14) housing the compressor (11) has flanges (16) connectable to pipes (17) providing secondary air to the combustion chamber (12) and/or turbine (13). The flanges (16) define passages having an asymmetric cross section. A method for retrofitting a gas turbine engine arrangement (10) is also disclosed.