Safe Flight Instrument Corporation

1946

Safe Flight Instrument Corporation produces a wide array of devices to make flying safer and more manageable. From their earliest flying lessons, all pilots are made familiar with the urgent whine of the stall warning indicator, the lifesaving alarm that sounds when airflow over the wings has slowed to a critical level. Safe Flight founder Leonard M. Greene invented that instrument in the late 1940s, and went on to earn more than 100 other patents.

The company has produced more than 600,000 stall warning indicators. Other products include angle-of-attack systems, airborne wind shear warning systems, automatic throttles, and engine monitoring devices. Customers include most aircraft manufacturers, as well as the U.S. military and business jet operators.

Origins

Safe Flight Instrument Corporation founder Leonard M. Greene came from an entrepreneurial family. According to his book, Inventorship: The Art of Innovation, his father had started a rubber cement company in a hayloft. Greene, who had four siblings, started inventing toys for himself as a child, according to a profile in Technology Review.

Greene presented research to the Institute of Aeronautical Sciences on the problem of breaking the sound barrier while still in his 20s. He was in charge of theoretical aerodynamics for Grumman Aircraft at the time, notes Aviation Week & Space Technology. Another critical aviation problem caught his interest after he witnessed an aircraft accident.

Planes need air to flow over their wings in order to fly controllably. If this airflow is disturbed or slowed past a certain point, the wings will lose their lift and the plane will fall--a condition known as a stall. In this case, there is a danger of the aircraft spinning sideways uncontrollably. Stall-spin accidents accounted for more than half of all aviation fatalities in the 1940s. Greene witnessed one of these accidents firsthand at the age of 19.

There are maneuvers to recover from a stall, given sufficient altitude and situational awareness. Greene developed a device--the Stall Warning Indicator--that alerted the pilot whenever a stall was impending. According to Technology Review, the design was very simple. A small sensor was installed near the critical point where airflow would separate from the wing in a stall. When wind passed the sensor at a dangerous angle, it would trip a circuit connected to a horn and light in the cockpit.

The first Stall Warning Indicators, introduced in 1946, sold for $17 each, according to Greene. Greene reports that he started his company in a rented carriage house with an initial investment of $14,000. The company had three employees.

The first Stall Warning Indicators, introduced in 1946, sold for $17 each, according to Greene.

1947–1981

The Saturday Evening Post (October 25, 1947) dubbed the stall warning indicator perhaps the "greatest lifesaver since the invention of the parachute." The device was made standard equipment in most aircraft by 1950, and the company would sell 500,000 units in the next 50 years.

In the 1950s, Safe Flight led the way in developing automatic throttle systems. These were used in a variety of business aircraft and airliners. The autothrottles led to the development of the SCAT (Speed, Command, Attitude, Thrust) system, which TWA put on its entire fleet in the mid-1960s.

Activism in the 1970s and 1980s

By 1971, Safe Flight was reporting sales of $2.4 million. New products in the early 1970s included an autopilot for sailboats.

In 1972, Greene responded to IBM's new policy of mandatory retirement at age 60 by placing an ad in a local business journal seeking to hire talent from among its displaced executives. This stance against age discrimination was but one aspect of Greene's social activism. Leonard Greene also was known for his efforts to hire the disabled and for writing on ways to end poverty.

In the 1970s, Greene established the Institute for Socioeconomic Studies in White Plains, New York. He advocated replacing most social programs with a direct income supplement, which he believed would be more efficient than the existing cumbersome bureaucracy. Greene helped form Corporate Angel Network in 1981 to provide cancer patients transportation to distant treatment sites using space available on corporate jets.

Warning Against Wind Shear in the 1980s

In the late 1970s, Safe Flight developed an onboard wind shear warning system designed to alert pilots to microbursts--the sudden, forceful downdrafts that were particularly dangerous during landings. The device also could calculate the best maneuver for flying out of wind shear. Unlike airport-based devices of the day (before Doppler radar), the Safe Flight unit was virtually immune to false alarms.

1974–2001

The units cost $10,000 to $13,000 each. By the mid-1980s, Boeing was incorporating Safe Flight's wind shear technology into its new airliners. It had been used by makers of corporate aircraft for several years, and was available as a retrofit for numerous aircraft types.

Ground Proximity in the 1990s

Leonard Greene was named to the National Inventors Hall of Fame in 1991. He continued to work on aviation-related problems.

Safe Flight teamed with SCI Systems, Inc. of Huntsville, Alabama, to develop an updated ground-proximity warning system (GPWS) in the early 1990s. GPWS had been mandatory equipment on commercial airliners since 1974; new regulations were requiring their installation on 10 to 30 passenger aircraft by 1994. The partnership with SCI was placed on the "back burner," however, when Safe Flight gave priority to its wind shear detection business, reported Business & Commercial Aviation.

In 1994, Greene patented an idea for a supersonic aircraft with a reduced sonic boom. He patented a propulsion system for such a plane in 1995, noted Aviation Week & Space Technology, assigning these patents to Boeing.

Other projects during the 1990s included "stick shakers" for alerting pilots to engine conditions through vibrations. In 1998 the company began developing a guidance system to help pilots avoid spatial disorientation during the last 30 feet of a landing, Randy Greene later told Business & Commercial Aviation.

In 2001, Safe Flight patented a technology to help aircraft avoid collisions with power lines. Safe Flight's device detected the 50- to 60-hertz signal emitted by alternating current. The "Powerline Detection System" was aimed primarily at helicopters. Units sold for $10,000 each, much less than competing products.

Regrouping After 9/11

2001–2004

Safe Flight Executive Vice-President Don Greene, the adopted son of the company's founder, perished in the September 11, 2001 terrorist attacks on the United States. An experienced aviator, he was a passenger on United Airlines Flight 93.

The company leadership was soon restructured. Another one of Leonard Greene's sons, Randall (Randy) Greene, replaced his father as president and chief executive officer. Randall Greene was a very experienced pilot who had led projects at Bendix Avionics and AlliedSignal Aerospace and had developed a new version of the Rockwell Commander aircraft.

Leonard Greene remained chairman. By this time, he had accumulated more than 8,000 flying hours. He was honored by the U.S. Patent and Trademark Office as part of its bicentennial celebrations in 2002.

Safe Flight had about 150 employees at the time. Many stayed with the company for their entire career. Randy Greene told Business & Commercial Aviation, "Safe Flight doesn't have layoffs. Ever."

The company was developing new helicopter products, including an Exceedance Warning System to alert pilots when engines were being operated outside accepted parameters. Another device displayed the status of a helicopter's landing light.

Safe Flight was promoting its new AutoPower automatic throttle, a computerized cruise control. Another important system was the N1 Computer, which adjusted jet thrust settings for optimum power based on real time air conditions. This freed pilots from having to look up settings on charts. By May 2004, Safe Flight had sold 600 N1 Computers to Cessna for use in Citation business jets.