Enstrom Helicopter Corporation

In the 1940s, a lumberman and mechanic named Rudy Enstrom started work towards his goal of building a helicopter. This effort started in a rural area of the Upper Peninsula of Michigan and was subsequently discovered by some local businessmen in the late 1950s. Enstrom Corporation was officially organized in 1959 in Menominee, Michigan.

Experienced aviation designers were recruited and the original prototypes gave way to a more thoroughly engineered product. The project was led by Jack Christensen, Alb Belauer, and Paul Schultz. Initial FAA certification was achieved for the F-28 model in April 1965, which was built in limited quantities. A more powerful version, the F-28A, was certified in May 1968. This helicopter entered full rate production, and over 300 helicopters of this model were manufactured.


Funding for the Company was initially provided by a small group of local businessmen. Shares in the Company's stock were then sold to the general public and proved to be quite popular with local residents of Northern Wisconsin and the Upper Peninsula of Michigan. By 1968 the total number of individual shareholders had passed the 10,000 mark. In October 1968, the Purex Corporation purchased controlling interest in Enstrom. At that time, Purex's PAC Group was the nation's largest support organization for commercial aviation, with operations such as Airwork and Pacific Airmotive. Purex's principal objective was to develop a turbine-powered model to add to the Enstrom product line. The engine selected, a fixed shaft Garrett model that was previously used for auxiliary ground power, was not successfully integrated with the airframe. After this technical reversal in 1970, Purex halted the turbine development and curtailed the existing piston helicopter manufacturing operations.

In late 1970, F. Lee Bailey, a noted trial attorney, began negotiations with Purex to purchase the company. The transaction was concluded in January 1971, and Mr. Bailey changed the company name from R.J. Enstrom Corporation to the Enstrom Helicopter Corporation. Aided by a very strong General Aviation market, Mr. Bailey successfully upgraded Enstrom's marketing activities and the F-28A became a commercial success. A  collaboration between a Boston industrial design firm and the Enstrom engineering team yielded a new aerodynamically styled airframe, the 280 Shark. The new model was certified in September 1974 and immediately put into production. The Shark was later named by Fortune Magazine as one of the 25 best factory-made products in the United States.

Enstrom engineering then focused on developing a turbo-charged version to solve the problem of reduced power under conditions of high temperature, humidity, or altitude. Enstrom obtained a Supplemental Type Certificate for the installation of a turbo-charger on a beefed up Lycoming engine. The power plant changed and several other product improvements were incorporated into the F-28C and 280C models that were certified in 1975. These models proved quite popular and production of the F-28A and 280 was phased out in 1976. Sales of light helicopters were booming in the late 1970s, particularly those of the light turbine, four/five place, Bell Jet Ranger and Hughes 500. Annual sales of these two models grew to over 500 units per year. Enstrom attempted to exploit the low end of this growing market segment by developing a stretched four-seat version of its piston-powered helicopter. Mr. Bailey recruited more engineers and general management personnel and named the new future product the 280L Hawk. He also took Enstrom back to private ownership by buying back the small minority public holding.

The Hawk first flew in December 1978, and was well received at the annual helicopter convention in January 1979. Unfortunately, the technical and financial requirements for this new product were significantly underestimated. After Mr. Bailey determined that he could not raise sufficient funding to finish and launch this new product, he decided to exit the business. Under new private ownership in early 1980, the Hawk project was put on hold and engineering efforts were redirected towards integration of a higher power piston engine in the F-28 and 280 body styles. Engine power was increased from 205 horsepower to 225 horsepower and a throttle correlator was introduced as standard equipment. These new models, the F-28F and 280F, were FAA certified in December 1980,  and initial deliveries started in 1981.

A series of product improvements, including skid gear fairings, a new air scoop and new vertical stabilizers, were introduced in the 280FX model. Certification was achieved in January 1985, and the 280FX replaced the 280F in production. The 280FX was the fastest piston-powered helicopter in the world.


In 1988, Enstrom won its first major military contract when it was selected to provide 15 280FX helicopters to the Chilean Army for pilot training. This was followed by a competitive win in Peru to supply 10 F-28F helicopters to the Army. Later, Enstrom was selected by the Colombian Air Force to provide 12 F-28F helicopters for pilot training. Enstrom also supplied a flight simulator with a visual system to Colombia. As recently as 2001, a fleet of 280FX training helicopters was delivered to the Venezuelan National Guard.

After preliminary market and design studies validated a satisfiable need, Enstrom initiated the development of a larger, turbine-powered helicopter in 1988. Two versions were to be developed: a three-seat military trainer, the TH-28, and a five-seat, commercial helicopter, the 480. Two major engineering tasks were identified to be tackled by separate teams:

1. Integration of an Allison 250-C20 turbine engine with the Enstrom drive train and rotor system, with initial verification through flight test in a standard 280FX body.

2. Design of a new, open cabin that would be 75% larger than the F-28F/280FX cabins. This would also require a new control system, fuel system, and landing gear.

The turbine-powered 280FX first flew in 1989 and the TH-28 first flew in 1990. The first 480 was airborne in 1993. A rigorous certification program included four test aircraft and over 1500 hours of flight test, as well as extensive ground testing and component fatigue testing. The TH-28 was granted FAA certification to C.A.R. Part 6 standards in September, 1992. The 480 was FAA certified to FAR 27 standards in December, 1994. The TH-28 and 480 were the first F.A.A. certified helicopters that were developed with a Computer Aided Design (CAD) drawing package, contrary to the claims of some other helicopter manufacturers. The Enstrom 480 quickly established itself as the best value for money aircraft in the light turbine class. Recent Enstrom engineering efforts have been focused on adding optional capabilities to the 480 and design refinements for improved performance and reliability.


The Enstrom 480 quickly established itself as an international product, with over 70% of the first fifty deliveries leaving the United States to international destinations. Engineering efforts focused on adding mission capabilities. Law enforcement missions were facilitated with FLIR and searchlight installations. Over water capability was established with the certification of emergency pop-out floats. Utility applications were expanded with the certification of a cargo hook. Winter use was enhanced with snow shoes.

With its large cabin and high capacity fuel system, Enstrom 480 operators soon found themselves desiring a higher gross weight rating. In response, Enstrom initiated a design and certification program to increase the 480's gross weight, and therefore, the useful load.

The more capable 480B was F.A.A. certified in February, 2001. The gross weight and useful load were increased by approximately 150 pounds. Through drive train upgrades, performance was maintained at the new higher gross weights and improved at the prior operating weights. The main rotor gearbox was upgraded to handle 6% more power through the addition of pressurized filtration of the lubricant. More power could be tapped from the highly derated Rolls Royce/ Allison 250-C20W turbine powerplant.

Included in the 480B certification program was a new vibration-dampening system for the cyclic control system. Providing most of the benefits of a hydraulic system without the cost, complexity, and reliability issues; this system is available for retrofit to earlier 480's.