title: Scrum Burndown issues
body: <p>We have been using Scrum for around 9 months and it has largely been successful. However our burndown charts rarely look like the 'model' charts, instead resembling more of a terrifying rollercoaster ride with some vomit inducing climbs and drops.</p>
  
  <p>To try and combat this we are spending more time before the sprint prototyping and designing but we still seem to discover much more work during the sprint than initially thought. Note: By this I mean the work required to meet the backlog is more involved than first thought rather than we have identified new items for the backlog.</p>
  
  <p>Is this a common problem with Scrum and does anyone have any tips to help smooth the ride?</p>
  
  <p>I should point out that most of our development work is not greenfield, so we are maintaining functionality in an existing large and complex application. Is scrum less suited to this type of development simply because you don't know what problems the existing code is going to throw up?</p>
  
  <p>Just how much time should we be spending before the sprint starts working out the detail of the development?</p>
  
  <p>UPDATE: We are having more success and a smoother ride now. This is largely because we have taken a more pessimistic view when estimating which is giving us more breathing space to deal with things when they dont go to plan. You could say its allowing us to be more 'agile'. We are also trying to change the perception that the burn down chart is some kind of schedule rather than an indication of scope v resources.</p>