Let me just clear up one thing-----
In Australia Canada and the USA Fly Runway Heading means fly the Heading without drift correction.
In the rest of the World Fly Runway Heading means fly the Track with drift correction.
Excerpt from my bible:---
Departure Tracking
If a SID or Departure Clearance specifies ‘Maintain Runway Heading' it is implied that a drift correction will be applied in order to maintain the runway track. Exceptions - USA, Canada and Australia require that “Runway Heading” be maintained without drift correction.'
Simple.
