Akron, Ohio-based B. F. Goodrich Co. reported third-quarter net income of $16.6 million, a sharp increase over the same three months last year. However, sales for tire, chemicals and aerospace and defense-products firm were down in the 1986 quarter, compared to a year ago. Lower sales in the latest quarter reflected the formation of the Uniroyal Goodrich tire joint venture, the company said. For the first nine months of 1986, net income showed a profit, compared to a loss, on sales that were less than the same period in 1985. Results for the first nine months of 1985 included a one-time charge of $365 million for restructuring the company's businesses. "Our chemical and aerospace businesses performed well during the quarter with each unit producing higher operating income than last year. We are beginning to see the inmprovement we expect from these operations," Chairman John Ong said. "Goodrich is clearly a different company from a year ago. This has been a year of transition as we implemented our restructuring program and established the Uniroyal Goodrich joint venture."