Task: Question Generation
Input (English): Passage: Since 1912 the Royal Danish Navy has operated aircraft either as a functional part of the navy or as flights conducted by the Royal Danish Air Force. Aviation pioneer Robert Svendsen purchased the first aircraft, a Henry Farman, and gave it to the navy who subsequently named it Glenten . Later the same year, a private funding effort made it possible to purchase two Donnet-Leveque flying boats named Maagen  and Ternen . At the outbreak of World War One the navy had two operational flying boats and five educated pilots making it possible to make daily reconnaissance flights over the Sound, monitoring German mine-laying activities. From 1914 to 1917, the Orlogsværftet  produced eight OV-flying boats and in 1915 and 1916 two naval flying stations were established in Copenhagen and Nyborg, mainly focusing on the two international seaways Øresund and Storebælt. After the war the Danish production of aircraft was stopped due to several crashes and an international surplus of warplanes. Following British advice, five Avro 504 were purchased for training purposes and based in Ringsted between the two important straits.
Output (English): Over how many years did Orlogsværftet produce 8 OV-flying boats?