Before you can elect a chairperson, you need to propose the committee and have 5 people sign up.
From the Wiki:
Committees can be created for any reason. They require five members and need to be approved by the board.
When it comes to decisions, committees are not independent. They really only have the power to make suggestions or spend money which has been allocated to them via donations or by action of the Board of Directors.
The board and membership often times follow the recommendations of the committees, but are not required to.
More information about the rules regarding committees is available here.