function onLocalPreCollision( event )
    --Some code
   elseif (not event.target.Skipped or event.target.Skipped == event.other) and event.other.myName == "sensor" then
        if event.contact ~= nil then
            event.contact.isEnabled = false
            event.target.Skipped = event.other
            if event.target.name == "copter" then
                   timer.performWithDelay(1000, function(event) startParas(event.target) end, 1, false)
             end
        end
   end
end

function setUpSensor()
    local attacher = display.newRect( 0, 0, 0, 20)
    attacher.myName = "attacher"
    attacher.x = display.contentWidth -15
    attacher.y = 0
    physics.addBody(attacher, "static")

    local sensor = display.newRect( 0, 0, 1, display.contentHeight - 50)
    sensor.myName = "sensor"
    sensor.x = display.contentWidth -15
    sensor.y = display.contentHeight / 2
    physics.addBody(sensor, "dynamic", collisionTable.sensorProp)

    myJoint = physics.newJoint( "distance", attacher, sensor, attacher.x, attacher.y, sensor.x,sensor.y )
end

function createEnemy()
    --...Some code...
    enemy.name = enemyName
    enemy:addEventListener( "preCollision", onLocalPreCollision )
    --...Some more code...
end

function startParas(copter)

  local paraNum = math.random(1, 5)
    if paraNum > 0 then
        timer.performWithDelay(150, function(event) createPara(copter) end, paraNum, false)
    end
end

function createPara(copter)
    if copter.x ~= nil then
        --Check to see if the copter is in the scene before the parachuter jumps
        if tonumber(copter.x) > 50 and tonumber(copter.x) < 470 then
            if copter.isAlive then
                local paraChuter = getSprite( spriteData.paraChuterData )
                paraChuter.name = getSpriteName( spriteData.paraChuterData )
                paraChuter.x = copter.x-10
                paraChuter.y = copter.y+5
                physics.addBody(paraChuter, "dynamic", physicsData:get("paraglider"))
                paraChuter:play()
                paraChuter.isFixedRotation = true
                paraChuter.linearDamping = 5
            end
        end
    end
end