FL,
Like Step Turn, I was also confused when I first saw the acronym HCAP. After some head-scratching and some research, I discovered that HCAP was just a re-badged GAPAN, which I had known about for many years.
While it's clear that HCAP does very good work in promoting aviation and recognizing outstanding achievements (with the notable exception of one recent award), I find it anachronistic that a professional aviation organization models itself on a medieval guild - a cartel/secret society set up to protect the interests of its members and establish a monopoly in its particular trade. It is no wonder that some people think HCAP is linked to Masonry.
Viewed from the outside, GAPAN/HCAP comes across as an "establishment" club, which view is reinforced by the headquarters address and the dinners in fancy dress.