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,
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
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.