Known primarily for his significant contributions to aviation technology, Leonard Michael Greene (1918-2006) was an American inventor who held over two-hundred patents. Many of Greene’s patents are related to aviation, with one of the most noteworthy being his Aircraft Stall Warning device which, as the name suggests, warns pilots of imminent aerodynamic stall. This is where the critical angle of attack, typically around 15 degrees, of the foil is exceeded resulting in a sudden reduction in lift. The warning device makes pilots aware that the airflow over the wings is not providing lift, allowing them to take the necessary action.
Greene’s invention was prompted by his witnessing an aircraft crash caused by stall when he was working as an aerodynamicist and engineering test pilot for Grumman Aircraft Corporation during World War II. At that time aerodynamic stalls were the cause of the majority of aviation accidents deaths and by the mid-1940s Greene had developed a way of warning the pilot timeously. His first warning device was powered by flashlight batteries, consisting of threaded bolts, a bicycle horn and an assortment of other components – rudimentary, but a step in the right direction. Greene filed to patent his device in 1944, with the patent being issued in 1949. In 1946, Greene founded the Safe Flight Instrument Corporation in White Plains, NY, where he developed, refined and marketed the aircraft stall warning device. The company went from strength to strength and has remained dedicated to the production of aviation safety and performance equipment for sixty years, with its principle products, many of which were invented by Greene,including FAA approved Stall Warning Systems, Angle-of-Attack Systems, Speed Control Systems, Speed Command of Attitude and Thrust (SCAT) systems, AutoPower, Airborne and Wind Shear Warning Systems and N1 Computer Systems.
Leonard Greene’s 2001 book Inventorship: The Art of Innovation details how he found creative inspiration in the simplest of things, with an example being his invention of a device to prevent the sonic boom caused by a supersonic aircraft when breaking the sound barrier by using a hollow fuselage and ducts to suck in, compress and release air through the aircraft’s tail – with his inspiration being the lowly earthworm’s method of moving through dirt by eating and excreting it.
Greene remained actively involved in Safe Flight Instrument Corporation until he passed away in 2006. His inventions and dedication to making flight safer has benefited millions of people who today view air travel as routine.
They may be well beyond the scope of the average businessman, but supersonic business jets are fast becoming hot property. With the ever-increasing demand for fast business jets, the market for small supersonic jets has exploded. Most of the major aircraft companies are gearing up for the demand by developing their own range of small super-fast jets and, despite massive price tags, it would seem consumers are lining up to purchase them.
When any aircraft travels through the air it continuously produces air-pressure waves similar to the waves seen behind a ship when its bow ploughs through the water. When an aircraft exceeds the speed of sound, known as supersonic speed or Mach I, at about 760 miles per hour measured at sea level, it continually generates shockwaves which drop as a trail of sonic boom along its flight path. In relation to the aircraft, sonic boom sweeps backwards, away from the aircraft, in a cone shape. A person on the ground will hear the sonic boom as an explosion, similar to a clap of thunder, when the shock waves on the edges of the cone cross his location.