http://www.heathrow.com/file_source/...fact_sheet.pdf
The international standard approach for most airports in the world is set at 3 degrees, except for obstacle clearance (e.g. buildings, mountains etc.). Recent experience at Frankfurt airport has demonstrated that slightly steeper approach angles are possible in the short to medium term to reduce noise for people living nearby.
Starting on 14 September 2015 we will be trialling an approach angle of 3.2 degrees. This requires no modifications to aircraft equipment or specific pilot training. The trial has been approved by the CAA and is planned to run until 16 March 2016.