British engineering firm Rolls Royce said on Friday that it was maintaining its full year guidance for 2015, but warned over a potential hit to revenues as a result of unfavourable currency rates.The company's 2015 guidance excluded the effects of foreign exchange translation. "Compared with 2014, average rates for Sterling have weakened against the US dollar but strengthened against the euro and the Norwegian Kroner,"it said.Rolls Royce said that if rates remain at the average levels seen so far in 2015, these movements would be broadly offsetting for earnings. On revenue, however, the impact would be significant."We would expect a roughly £350m reduction from translation," said the company.Rolls Royce announced in April that the company would be welcome Warren East as its new chief executive in July.