Historical clue formulations

• Powerful engine — 2017-09-24
• Powerful engine — 2013-04-20
• Kind of engine for an airplane — 2012-02-27
• Engine using a stream of compressed air — 2007-12-08
• Engine for missiles — 2000-06-01
• Big airplane engine — 2000-03-27
• Simple propulsion unit — 1997-03-15
• Airplane engine — 1994-10-11