Complex sentence: After a few accidents due to engine problems the S1s were withdrawn from service in 1970 and in 1971 the RAF stood up their own OCU (237) to take over the training of both their own and the dwindling number of RN aircrews.
Split into simpler sentences: After a few accidents due to engine problems the S.1s were withdrawn from service in 1970. In 1971 the RAF stood up their own OCU (237 OCU) to take over the training of both their own and the dwindling number of RN aircrews.