sm_fortressblast_drop is a ConVar in Fortress Blast that was added at release. It controls whether or not players have a chance to drop powerups on death (how big that chance is is determined by
sm_fortressblast_drop_rate). If the ConVar is set to 0, dropping powerups on death will be disabled. If the ConVar is set to 1, powerups will only have a chance to drop if the map does not contain a powerup spawns file. If the ConVar is set to 2, the chance to drop a powerup will always be enabled, although dropping a powerup is not guaranteed as it is still restricted to the chance mentioned above.
The default value of this ConVar is 1.