Question: A hot air engine was based on a device by which English engineer and aeronautical legend?
Context: Per Lindstrand (born September 8, 1948) is a Swedish aeronautical engineer, pilot, adventurer and entrepreneur.  He is particularly known for his series of record-breaking trans-oceanic hot air balloon flights and, later, attempts to be the first to fly a Rozière balloon around the Earth – all with British entrepreneur, Sir Richard Branson.  He is also the founder of eponymous Lindstrand Balloons hot air balloon manufacturer based in Oswestry, England. A hot air engine (historically called an air engine or caloric engine) is any heat engine that uses the expansion and contraction of air under the influence of a temperature change to convert thermal energy into mechanical work.  These engines may be based on a number of thermodynamic cycles encompassing both open cycle devices such as those of Sir George Cayley and John Ericsson and the closed cycle engine of Robert Stirling.  Hot air engines are distinct from the better known internal combustion based engine and steam engine. Elliott J. Stoddard invented and patented two versions of the Stoddard engine, the first in 1919 and the second in 1933.  The general engine classification is an external combustion engine with valves and single-phase gaseous working fluid (i.e. a "hot air engine").  The internal working fluid was originally air, although in modern versions, other gases such as helium or hydrogen may be used. A working fluid is a pressurized gas or liquid that actuates a machine.  Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder.  More generally, in a thermodynamic system, the working fluid is a liquid or gas that absorbs or transmits energy. A compressed-air vehicle (CAV) is powered by an air engine, using compressed air, which is stored in a tank.  Instead of mixing fuel with air and burning it in the engine to drive pistons with hot expanding gases, compressed-air vehicles use the expansion of compressed air to drive the pistons.  One manufacturer claims to have designed an engine that is 90 percent efficient. A powered attic ventilator, or attic fan, is a ventilation fan which regulates the heat level of a building's attic by exhausting hot air.  A thermostat is used to automatically turn the fan off and on, while sometimes a manual switch is used.  An attic fan can be gable mounted or roof mounted.  Additional vents are required to draw in fresh air as the hot air is exhausted.  Attic fans are typically used in warmer months, when temperatures in an attic can exceed 120 °F .  A fan may be installed in an attic for the different purpose of cooling a whole house, venting hot air out via the attic; such fans are often called whole-house fans. Victor Zagainov (May 31, 1953 - October 5, 2002) was a hot air balloon pilot and astronomer from Kazakhstan.  He was the first and only hot air balloon champion of the USSR (1991), Hot Air Balloon champion of the Republic of Kazakhstan (1993), the winner of the International Balloon Grand Prix Todi (Italy) (1993), the champion of the CIS (1996).  He organized Grand Prix of Zagainov and was awarded Fédération Aéronautique Internationale (FAI) Diploma for Outstanding Airmanship (Award ID# 5349) and the FAI Air Sport Medal (Award ID# 5244) in 2003. A Daboll trumpet is an air trumpet foghorn which was developed by an American, Celadon Leeds Daboll, of New London, Connecticut.  It was basically a small coal-fired hot air engine, which compressed air in a cylinder on top of which was a reed horn. A Manson-Guise engine is an improved version of a Manson engine.  It is a type of hot air engine, converting a temperature difference into motion.  There is a hot side and a cold side to the engine.  Providing there is a large enough temperature difference between the two sides the engine will run.  The Manson-Guise engine is probably the simplest type of hot air engines having only a single con-rod, with a displacer piston and power piston that move at the same time.  Manson-Guise engines seem to be fairly unique in the fact that they can run in either direction (flywheel can run clockwise or anti-clockwise). Sir George Cayley, 6th Baronet (27 December 1773 – 15 December 1857) was a prolific English engineer and is one of the most important people in the history of aeronautics.  Many consider him to be the first true scientific aerial investigator and the first person to understand the underlying principles and forces of flight.
Answer: George Cayley