Hi Guys,
You will find what you're looking for on the Sennheiser website, here:
http://www.sennheiser.com/sennheiser...ducts_aviation
"Connector Assignments" is the pdf you're looking for. You can buy the adapter from the standard Boeing type (2 plugs) to the XLR5 connector used on the airbus from Transair etc for about £30. You will find that you will spend the better part of £30 on the bits you need to make it yourself. I've made one so far for my HMEC25, and just doing another two. If you do, solder very carefully.
Hope this helps.
high-flyer