A servo valve (1) comprises a pilot stage and a primary stage. The pilot stage includes a first spool (10) mounted for movement between a first position and a second position. The primary stage includes a second spool (2) mounted for movement between a third position and a fourth position. The pilot stage and the primary stage are arranged such that, in use, movement of the first spool (10)from the first position to the second position causes movement of the second spool (2) from the third position to the fourth position.
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