Jet engine maker Rolls-Royce pledged to buy back £1bn of shares if it succeeds in selling its energy gas turbine and compressor business to Germany's Siemens as it outlined plans to reduce capital spending in the next five years.Rolls said it had decided to return the proceeds of the sale to shareholders as it had no plans for any material acquisitions and had a strong balance sheet.The sale, announced on May 6th this year, is due to complete by the end of 2014.The company also confirmed group guidance for 2014 and 2015 and said it would reduce group capital spending towards 4% of underlying revenue within three to five years from the 2013 figure of 4.9%.It expects deliveries of its flagship Trent jet engines to top 4,000 by 2023.It also said it would continue to target a credit rating of between A- and A+.PW