Rudolph “Rudy” John Enstrom (1916-2007) was born in Crystal Falls (Michigan) on June 23, 1916. In 1934 he graduated from Crystal Falls high school and completed his studies at Hemphill Engineering School in Detroit. He then returned to Crystal Falls to join his father in his lumber business. During those years he opened a shop to sell and service power saws. He also developed a gadget for eliminating pinching by the saws and almost went into production of that, but he couldn’t get materials during the war.
In 1949 he accepted a job at the Warner iron mine at Amasa (Crystal Falls) where he was employed as a surface foreman and master mechanic. Rudy had an unexplainable passion for aviation from a very young age. Several years later, what began as a dream became a reality. In his spare time he started to build an experimental helicopter using the shop in his father’s sawmill. The original model tested in 1943 had a 37/50 kW/hp engine with a flat belt drive and two counter rotating rotors. The blades were made of wooden spars covered with fabric. The helicopter didn’t fly due to vibrations. Despite this initial failure, he did not lose his enthusiasm. He went back to the drawing board. Building, rebuiding and correcting by trial and error. At that time, helicopters were just emerging and in their infancy stage.
Between 1943 and 1958 Rudy Enstrom built five different helicopters. In the course of the experiments he incorporated new devices of his own making.

To work undisturbed and avoid unwanted visits for operational tests, the helicopters were towed behind his car for four miles to a remote area. Enstrom got help from an electrical-plumbing contractor, the foreman of a dairy, a garage mechanic and his brother Harold. 
On March 19, 1958 Rudy Enstrom filed a request with the United States Patent Office for a control mechanism for helicopters which was patented on August 1, 1961.
In October 1958 the Warner iron mine was permanently closed and Rudy Enstrom, its master mechanic, joined the growing list of jobless miners and workers. In that period he received a job offer in Minnesota, but his wife Edith encouraged him to continue the helicopter tests first, as that could alter his future plans. Enstrom was at a crossroads. With more time on his hands then, he finally got his fifth helicopter to fly at a gravel pit near Crystal Falls. It didn’t do much, but it got off of the ground. Rudy had no helicopter flying instructions so he also had to learn to fly his own helicopter which was another challenge, but Rudy’s desire and determination were as strong as the steel he worked with.

A fortuitous encounter

The closing of the mine put John “Jack” M. Christensen (1927-2010), a Menominee native, in roughly the same boat with Rudy Enstrom. In 1951 Jack and his father started a company called Christensen Machinery and Supply Company. The company handled various industrial mining machinery and manufacturing carbide tools, selling primarily to iron mine companies and general industry in Northern Michigan. It was in his role as a machinery and tool salesman that Jack met Rudy Enstrom in 1956. One day, while discussing the sad industrial situation in the Upper Penisula, Rudy revealed that he was testing a homebuilt helicopter of his own conception. According to a statement by Jack Christensen, Rudy Enstrom was hoping to find financing for eventual production. Intrigued by the story, in January 1959 Jack Christensen, accompanied by three other businessmen from Menominee, met Rudy Enstrom who staged a demonstration for them. At that point they didn’t know what to think, but they all decided not to drop it, Christensen later said. Fascinated by the helicopter, they decided to contact Albert C. Ballauer, chief research and development engineer employed by Parsons Corporation Aircraft Division. Ballauer was an aeronautical engineer and a graduate of the University of Cincinnati who designed rotor blades for many of the world’s best known helicopters.  He was previously engaged in aircraft development work with Aeronca, Curtiss-Wright, Mc Donnell and the Parson Corporation. While working for Mc Donnell he was project engineer for the XH-20 “Little Henry”, the world’s first ram jet helicopter. He also acted as consultant to such Italian firms as Fiat and Aer Lualdi.

1959 - A decisive breakthrough

On February 14, 1959 at Liver lake, near his cabin, Rudy Enstrom gave a new flight demonstration, this time in front of representatives of the Parsons Corporation. That Saturday the experts arriving from Traverse City were looking at the results of more than 15 years of spare-time ingenuity of a man who had nothing other than a keen interest in helicopters to guide him in his work.

Ballauer agreed after looking at Enstrom’s machine that his straightforward, unsophisticated approach could be used as a starting point to build a helicopter with simplified engineering and consequently lower price. Rudy Enstrom constructed the frame of the entire fuselage, including that of the cabin, engine mounts, and tail assembly using electrical aluminum conduit, the only material light enough and readily available for the experimental model. Each piece was welded individually to form the triangular tail assembly. The two rotor blades were hand fashioned out of laminated spruce and covered with bonded layers of fiberglass. Each were balanced meticolously to eliminate as much vibration as possible. How many hours were spent by Rudy Enstrom in his basement shop, focal point of his efforts in developing his helicopters, is hard to estimate, although the figure would certainly be thousands.
Test pilot Fred Hill and engineer technician Frank Bolaro, both employed by Parsons Corporation, witnessed the test flight and were favorably impressed with the design features of the helicopter. Their favorable report increased the interest and confidence around the helicopter.

Birth of R. J. Enstrom Helicopter Corporation

After the opinions and recommandations of the rotary-wing engineers, Jack Christensen was finally convinced that Rudy’s dream could be realized to the advantage of an area which had lost much of its industry. Consequently, he started to talk about the project with many of his machinery customers and friends and was encouraged by their positive reception for the idea.
On April 17, 1959 a group of businessmen from the Upper Peninsula of Michigan and Illinois organised the R. J. Helicopter Corporation which financed construction of the first model, the Enstrom F-27. Jack Christensen, who assisted in forming the corporation, was elected president. Vice president and general manager was designated Rudy Enstrom and secretary-treasurer Richard Sawyer, a Menominee attorney. Members of the board of directors also included Albert H. Luke (who was one of the first helicopter instructor pilot in the Midwest), Alb C. Ballauer, Douglas E. Jones, a manufacturer of motor parts and Edgar E. Erdmann, a paper mill executive. After organizing the Corporation, Rudy Enstrom started to work full time on design and construction of a new prototype designated Enstrom F-27.
The model tested ipreviously in February could not be tested fully enough to make a complete evaluation. . Because it was constructed of materials that did not meet aircraft specifications in accordance with Civil Aeronautic Authority requirements (CAA) , it was put aside.
The garage at the rear of Rudy’s home, just outside the eastern limits of the city on M-69, was converted to a workshop, and all space devoted to the design and construction of the helicopter.
During that period, local newspapers such as The Diamond Drill, the Iron County News or the Menominee Herald-Leader and the Marinette Eagle-Star started to report the progress being made. 

After creation of the R. J. Enstrom Helicopter Corporation, many residents in that area began to read the news concerning the young company with great interest, catching glimpses of new job opportunities among other things.
On November 27, 1959 while the design and construction of the F-27 was under way, the company applied to Federal Aviation Administration (FAA) for a type certificate.
The R. J. Enstrom Helicopter Corporation was officially incorporated under the laws of the State of Michigan on December 22, 1959 and its office was initially established at Crystal Falls.

1960 – R. J. Enstrom Helicopter Corporation moves to Menominee County airport

On January 12, 1960 preliminary basic data concerning the F-27 prototype were publicily released. Most structural and mechanical construction of the prototype was completed in the subsequent months by Rudy Enstrom in his workshop. Drawings of each part were sent to a machine shop to be manufactured and then assembled. The Prescott company did most of the precision work, but some other local firms also assisted in the production of the first helicopter. At the same time, work on the design of a cockpit enclosure and interior control panel were completed by a Milwaukee industrial designer.
In that period the company hired its first employees. Among them, Richard L. Schmitt, who left a position with Boeing to assume design engineering responsabilities in connection with the final development and construction of the corporation’s new helicopter model. 
Officials of the CAA and Federal Aviation Administration (FAA) arrived in Crystal Falls to confer with members of the corporation and discuss steps necessary to obtain certification of the helicopter.
Using a check-list as reference, and a lengthy list of recommendations, the team continued the development program of a helicopter model that would meet the construction and engineering standards required by the two agencies. Also itemized, were required procedures in administration, procurement and parts identification.
Officers of the R. J. Enstrom Helicopter Corporation received formal assurance of cooperation and support for their project by the members of the Crystal Falls Chamber of Commerce, city officials, representatives of the Mastodon township, board and others interested. 
On May 2-5, 1960 during the annual meeting of the Helicopter Association of America, Rudy Enstrom, Jack Christensen and Alb Ballauer staffed a booth at the Sheraton Park Hotel in Washington D.C. On that occasion the founders attended the convention and had the opportunity to talk with such notables in the field of helicopter design and manufacture as Stanley Hiller and Igor Bensen. Featured speaker at the main banquet was President Dwight D. Eisenhover. 
By August 1, 1960 due to lack of space in Rudy’s garage, Menominee County Board of Supervisors awarded the concern a five year lease on a county-owned building covering 223 square meters (2,400 square feet) at Menominee County airport. Construction and assembly continued in the hangar shop purchased by the county from M and M Aviation Company a year before. 

The county also provided financial help for a small addition to the building to provide additional space for the engineering department and offices. Tests of each component were made before being assembled and tested as a complete unit. After completition of the first prototype (registration N915D) the FAA assigned a specific area, extending from Menominee to Crivitz, to be used by the corporation during early test flights.

First tie-down and test flights

Based on information gathered to date, it appears that the Enstrom F-27 made its first tie-down run-ups in October 1960 and that the first free flight was made by Albert Luke on November 12, 1960.

Other flights, mostly hovering tests, were made by Fred Hill who had more than 4,500 hours flying helicopters. On December 8, 1960 the company announced that the first series of test flights had been successfully completed. The first extensive tests were witnessed by FAA inspector Joseph Mocca. As a result of these tests, the FAA granted the firm an experimental airworthiness certificate.
While testing the helicopter, Albert Luke and Fred Hill were confronted with vibration problems. Ballauer believed this would be a relatively simple problem to fix. Modifications were made, but after about 25 hours of test, the engineers switched from the original two-bladed main rotor to a new three-bladed rigid-in-plane main rotor. The new rotor was installed in February 1961. Luke did a five-minute flight and was impressed by the smoothness. The vibration problems seemed to have disappeared.

On March 3, 1961 James S. Terrell was hired as test-pilot and made the first familiarisation flights. Terrell gave an enthusiastic report to the corporation members. He said the aircraft had been flown through several meneuvers, including hovering 90 degrees to the wind with a velocity of over 20 mph, flying sideways, forward and rearward. “Under all conditions the helicopter responded to the controls perfectly and was unusually smooth in operation” he said. “Even though the helicopter is a new ship in the experimental stage, it has very good flying characteristics” he added. During further tests, new problems emerged and the main rotor design was again modified.
At that time, the company employed 13 people, including 3 engineers, 2 licensed aircraft mechanics, a tool and die maker, a rotor blade specialist and a commercial test pilot.
Among the first employed were Robert Bretel, a layout draftsman (Bretel was responsible for the control system), Robert Bokatich engineering designer (was the third engineer responsible for the successful drive system), Homer Tessier shop superintendent, Robert “Bob” Tessier a machinist, Edward Malek, Earl Chervenka, Dick Schmid, Rosemary Law, Ernie Tykala.
While the two-seat N915D was being tested, the construction of two pre-production helicopters designated F-28 (N40042 and N40043) was undertaken.

In May 1961 R. J. Enstrom Helicopter Corporation was far enough along to offer 300'000 $ in stock. Over 1,000 people, largely from the Menominee and Marinette areas became shareholders. The injection of capital allowed the young company to continue with its development plans. The following year, a similar block was offered and people lined up at the bank to spend $300,000 more for shares.
Back then, Enstrom  was owned by over 3,000 twin city area residents, but none of them controlled more than 5% of the stock.
In November Rudy Enstrom went to Washington D.C. where he met representatives of the three major branches of the armed services. The conference took place in the Pentagon office of General R. D. Meyer, commander of the Army Transportation Corps.

1962 – First flights of the pre-production models

In January 1962, Rudy Enstrom along with Jack Christensen, Alb Ballauer and James Terrell attended the HAI annual convention in Dallas. On display at the convention was a model of their helicopter. From that moment on the young company began to gain more national and international attention. With an initial estimated price of $24,950 the helicopter aroused great interest among operators. In this period the structure of the helicopter underwent rigid stress tests conducted by the FAA testing the helicopter’s chassis, tail section, undercarriage and shock absorbing characteristics and received FAA approval for all facets of the test. 
On May 27, 1962 the first of two pre-production F-28s (N40042) made its maiden flight. It differed from the first prototype in having a fully enclosed fuselage and tail structure, a three place cockpit and a three-blade rigid-in-plane main rotor which did not require lag hinges or dampers. The offset hinge minimized the effect of CG shifts and also caused the hub and fuselage to respond almost immediately to any change in rotor inclination resulting from control input. At the same time, the hinge increased in-flight stability trough its tendency to resist momentary changes in fuselage position caused by gusts.
Another rotor innovation was the use of flapping and feathering hinges with a unique laminated elastomeric bearing. This was a circular sandwich of microscopic layers of metal and plastic designed especially for applications involving movement through only a limited arc. Manufactured by the Marlin-Rockwell Company, the bearing could move freely in one plane in an oscillating motion while withstanding heavy centrifugal loads. The elastomeric bearing was designed to have a minimum service life of 1,000 hours. It had no moving parts and did not required lubrication.
During the summer 1962, the Enstrom F-28 powered by a 134/180 kW/hp Lycoming HO-360-A1A was extensively tested.

A newspaper article appearing in September 1962 states that FAA certification was scheduled for the first half of 1963, with first deliveries to be made in the second half of that year. Up to that moment, $750,000 USD were invested in the development program and certification process. 
Enstrom expected to sell the F-27 at a price of $27,400 USD, the lowest in the industry for a three-place helicopter (one of its direct competitors, the Hughes 269B, was sold at $29,875). 
In an interview with pilot and aviation journalist Andreas “Andy” Aastad (1922-2022), who worked on behalf of R. J. Enstrom Helicopter Corporation, Jack Christensen stated that the fully articulated rotor system proposed and developed by Paul L. Schultz was adopted after discarding the idea of an improved semi-rigid rotor system. 

A tragic incident

On November 13, 1962 test pilot James “Jim” Stuart Terrell lost his life while testing the first pre-production prototype N40042. He had just taken off from Menominee airport and had been airborne for about a minute and a half when some witnesses saw the craft plunge into a field about a mile north of the airport from an altitude of about 300 feet and catch fire.
Terrell, married and father of four children, was born on December 10, 1924 in Oceanview (Virginia). In June 1961 he moved to Menominee from Green Bay. 
A WWII veteran, he had been an army helicopter pilot from August 1949 through March 1958. His credits included tours of duty in Korea where he specialized in helicopters.
Before joining R. J. Enstrom Helicopter Corporation on March 9, 1961 he had been senior pilot with the Chicago Helicopter Airlift Division of the Butler Aviation Company. The 37 year-old was an experienced helicopter pilot with hundreds of hours logged.

FAA and Civil Aeronautics Board officials rushed to Menominee and joined Enstrom engineers to determine the exact cause of the crash. More than 100 area boy scouts assisted the following Saturday afternoon in a search for missing parts of the helicopter. Minute inspection of the wreckage was conducted to identify a possible mechanical problem. The accident came when Enstrom was in the final stages of showing compliance for the issuance of FAA type and production certificates to manufacture and sell the helicopter. Several thousand residents (most of them homefolks) of the Upper Penisula and Northern Wisconsin had a personal interest in the fatal crash. They had dug into their pockets to buy stock in the R. J. Enstrom Helicopter Corporation.
The investigation found nothing to indicate a mechanical malfunction or failure. The Milwaukee Sentinel published an article on February 19, 1963 stating that Terrell was trying various rates of climb when he lost rotor RPM. That was probably the cause of the tragic accident. A picture of the crashed helicopter published in some newspapers confirms without a shadow of a doubt one thing, i. e. that the rotor blades were rotating at low speed when the helicopter impacted the ground.

1963

It took federal agencies some months to decide that the helicopter was structurally and mechanically sound. Meanwhile as Christensen stated “we had to make a decision: do we go on, or do we stop? Stockholders urged the company to go on, and the second prototype (N40043) was in the air in May 1963”. 
The first test flight with the second prototype was made on May 15, 1963 by Mott Stanchfield who took the place of Jim Terrell as new test pilot.
In June 1963, the US Army mobility command announced that R. J. Enstrom Helicopter Corporation had been invited to compete for the LOH program, a multi-million dollar US Army aircraft contract.
Army aviation experts were sent to Menominee earlier that year and found the small firm and its product met exacting military requirements.
The residents and the stockholders crossed their fingers in the hope that the helicopter would be selected. A military contract could create as many as 500 new jobs in Menominee and hundreds more in Upper Penisula supplier plants.
The F-28 was sent to Fort Rucker (Alabama) on September 4, 1963 for 20 days of evaluation competition with helicopters from four aircraft corporations (Bell Helicopters, Hiller Aircraft, Hughes Tool Company and Brantly Helicopter Corporation). The Army planned to order 275 helicopters for use as basic trainers for new helicopter pilots. The selection process would be based at least partially on the results of the evaluation competition. Enstrom did not win the ciontract. The Hughes TH-55 Osage won and792 units were order by the US Army.
On November 13, 1963 the R. J. Enstrom Corporation moved into its new $75,000 USD building which covered a surface of 1,205 sq meters (13,000 square feet) while continuing to lease the old building next door.
Two days later on November 15, 1963 the FAA granted provisonal certification of the F-28, paving the way for final test phases. This was clear indication that the aircraft substantially met demanding FAA requirements.

1964

In February 1964, Lewis College put deposits down for two F-28 helicopters, to be used for student training and powerline patrols. These would be the first to be delivered, scheduled for that summer. This agreement was later cancelled for unknown reasons. Despite optimistic sales forecasts, the financial situation at the company continued to be tight. By October, operations were reduced as Enstrom found it impossible to pay any bills except those involving payroll or materials needed for certification. It was only doing development and test work as required for certification. All production was deferred. The company planned to complete and submit all data to the FAA by the middle of December. New financing would be required to get production of the F-28 underway.
Seeing the company’s financial difficulties and setback, in October 1964 Rudy J. Enstrom decided to leave the company. He accepted a job offer made by Lakeshore Inc. in Iron Mountain as chief of research and design. 
According to the annual report published in 1964, by contract executed on April 20, 1961 the company agreed to issue 1,200 shares of its capital stock each year for 5 years (aggregating $60,000) commencing retroactively in 1962 to Rudy Enstrom in consideration of his assignment of one patent and three patent applications to the company. Moreover, the company agreed to pay him a royalty of $100 for each helicopter sold using the patents.

1965

After more than 4 years of continuous work, on April 15, 1965 the Enstrom F-28 finally received coveted FAA type certificate number H1CE. 
On May 6, 1965 the Enstrom F-28 was elected Michigan’s product of the year. The F-28 competed with many products for this honor, including the brand new Ford Mustang motor vehicle, so winning was quite a spectacular achievement. 
On July 11, 1965 the pre-production prototype (N40043) was damaged beyond repair in a forced landing at Marquette County Airport. According to the NTSB report, the entire tail rotor assembly separated from the aircraft when blade grip attachment scews failed during the approach. Fortunately, neither the pilot nor his passenger were injured.
In August 1965, a third issue of $120,000 USD stock was offered.

1966-1967

Deliveries began early in December 1966 at a base price of $32,750 (by comparison, the cost of a Hughes 269B was $31,500, and the cost for a new Bell 47G3B-1 $47,950). 
In the summer of 1965, Jomac Air Associates Ltd. of Vancouver, British Columbia, acquired exclusive rights to sell Enstrom helicopters in Western Canada. This was followed by an agreement to purchase the first two Enstrom F-28 helicopters produced at the Enstrom factory in Menominee when they were completed in early 1966. On January 18, 1966 Michigan newspapers record the formal delivery of an Enstrom F-28 to P. Barry Jones in Menominee. Jones was the principal of Jomac Air Associates Ltd, the parent company of Northern Helicopters Ltd, an active commercial helicopter operator in Western Canada with its main operating base at the Abbotsford International Airport 40 miles east of Vancouver. 
On March 8, 1966 Canadian registration marks were issued to Northern Helicopters Ltd by Canada’s Department of Transport and allotted to F-28 s/n 4 N137E (CF-UFW) and F-28 s/n 007 N192E (CF-UFX) but were soon withdrawn on April 21, 1966 when the planned purchase and importation of these helicopters did not materialize.
F-28 s/n 4 N137E was displayed at the Abbotsford International Airshow on August 13-14, 1966 after leaving the Menominee factory in late July and passing through St. Louis, Wichita, Albuquerque, Los Angeles and San Francisco on a sales tour. During the tour and at the airshow, Enstrom publicized Northern Helicopters’ purchase of the first F-28 helicopters off their production line and the agreement for Jomac to sell Enstrom helicopters in Canada. 
In mid-December 1966, Northern Helicopters became engaged in a dispute with Canada’s Air Transport Board over compliance with administrative licensing requirements. 
In late December 1966, Enstrom F-28 s/n 5 CF-UVQ left the Menominee factory, stopping for display and marketing purposes at the Helicopter Association of America convention in Palm Springs, California January 15-19 before making its way to Vancouver and delivery to Jomac/Northern Helicopters.

By March 1967, Northern Helicopters Ltd, and its parent company Jomac Air Associates Ltd, had suffered significant financial difficulties due to loss of contracts during the licensing difficulties earlier in the year.
On May 11, 1967 the assets of Northern Helicopters were sold at a bankruptcy sale in Vancouver but by June 1967, newspapers reported that Northern Helicopters had re-started commercial helicopter operations in British Columbia from their base at the Abbotsford International Airport. There is no evidence that the company was ever involved with Enstrom helicopters again.
It is believed that all Enstrom helicopters in possession of Jomac and Northern Helicopters during their financial difficulties were returned to the manufacturer where they were eventually delivered to customers in the USA.

Canadian Centennial Copter

In 1967, newly manufactured Enstrom F-28 s/n 008 was temporarily donated by the manufacturer for use by Canadian private pilot Frank Ogden in his cross-Canada flight celebrating Canada’s centennial. The flight received funding from the governments of Canada and British Columbia and carried special post-marked envelopes that were mailed from each stop. The helicopter was flown on a temporary flight permit and certificate of registration as CF-CCP with the registered owner shown as Niagara Helicopters Limited of Niagara Falls, Ontario. The helicopter never appeared on the Canadian Civil Aircraft Register.
The flight started in Louisburg, Nova Scotia on June 1, 1967 and made at least 93 stops throughout Canada and Alaska (which was also celebrating its 100^th year of statehood) before its final stop in Cranbrook, British Columbia on September 11, 1967 before being returned to Enstrom on October 4, 1967. The helicopter flew over 400 hours, travelled over 26,000 miles and made over 2'200 landings during its time in Canada.

On January 15-18, 1967 at the Helicopter Association of America’s annual meeting in Palm Springs, California, Jack Christensen stated that the firm had 25 orders from 10 operators in the USA, New Zealand, Argentina, Sweden, Austria and South Africa. According to Mott Stanchfield (Director of Sales) his company expected to deliver 35-40 F-28s during 1967. In the course of an interview with a journalist from Flight magazine, he confirmed that improvements and refinements were incorporated in the F-28 during 1966. The list included: improved cabin heating system, night landing, better isolation engine/drive system vibration, tinted cockpit windshield and door plexiglas, improved door sealing and latching, improved upholstering and cockpit appointments and an automatic belt tensioning device to increase power belt tension upon demand for power. Up to that moment (January 1967), all F-28s had accumulated a combined total of 1,364 hours of flight. 
The company intended to develop a full list of accessories, including agricultural equipment, flotation gear, cargo racks, cargo hook, etc. 
In 1967, Enstrom Helicopter Corporation responded to a new request for a tender from the US Army Aviation Materiel Command for primary helicopter trainers. In order to meet the specified performance, an improved version known as the F-28A was developed. It had increased power and performance. A prototype of this model was evaluated by the Army, first at Fort Rucker (Alabama) and later at the Army Training Center in Fort Wolters (Texas).

At both locations the helicopter performed well and met performance requirements but was again not selected.
The Enstrom F-28A was generally similar to the F-28 with the exception of a modified drive reduction ratio, so that the main rotor would turn more slowly allowing the engine to run at 2,900 rpm at 205 hp. This increased the aircraft’s useful load by 200 lbs (91 kg). Improvements in visibility, accessibility and convenience were incorporated in this new model, of which deliveries were initially scheduled to begin in April 1968.
The Enstrom model F-28A was added to the F-28 type certificate number H1CE on May 28, 1968.

Growth of the company (by January 1967 it employed 57 people), and expanding financial requirements, dictated the need for additional capital beginning in 1967. The lack of money prevented manufacturing on any large scale (in 1967 the company delivered 5 aircraft). Late that year rumors began to circulate in the Twin Cities about a possible sale of Enstrom to a West Coast company. Few knew that negotiations regarding the possible purchase by Pacific Airmotive had begun nearly a year before the purchase was completed.
On September 12, 1967 Pacific Airmotive had been acquired by Purex Corporation Ltd. of Lakewood, California. Purex Corporation produced home cleaning agents and a variety of other products. 
It is interesting to report that in October 1967 a 10-year contract with Twyford Moors Ltd of Eastleight, Hants, to assemble F-28s in England was announced. Many F-28s were subsequently exported to England.

1968

On January 5, 1968 it was announced that R. J. Enstrom Corporation had been sold to Pacific Airmotive Corporation of Burbank, California. The new owner insisted on the development of a turbine-powered helicopter, which was initiated almost immediately. The result was the emergence of the T-28 essentially utilizing the F-28A with a 220 hp Garrett AiResearch TSE-36-1 shaft-turbine engine. Unfortunately, the new program was complicated and generated a substantial increase in expenditures, which was a big problem for a relatively small company not yet producing a significant income.
In October 1968 the capital requirement was finally satisfied. Enstrom was now back on track. Infusion of new capital allowed the acquisition of additional equipment, floor space and personnel, which sharply increased production of helicopters. The manufacturing facility in Menominee was expanded. A total of 1,200 sq meters (13,000 sq ft) of floor space were added to existing plant facilities. Also, research and development programs that had been held in abeyance were activated. 
In addition to its F-28A program, Enstrom planned to put the T-28 into production at the beginning of the second half of 1969. Various media reported that, to meet anticipated demand for the T-28, Enstrom gave an order for 500 turbines to AiResearch. However this seems rather unlikely. 
During the last 6 months of 1969, the company added approximately 100 new personnel. Late that year Enstrom was employing about 170 people and a total of 12 F-28s were delivered. 

1969

In January 1969 at the annual HAA show, Enstrom’s test pilot Mike Meger attracted attention with his flight demostration of an F-28A. 
During the spring of 1969 the Enstrom F-28A was exhibited in many US States. In May, at the annual American Helicopter Society Forum in Washington D.C., the new turbine-powered T-28 was presented to the military as a potential training helicopter.
In June 1969, Enstrom employed about 150 people and was manufacturing nearly a helicopter a week. New sales offices were established across the country under the direction of Andreas “Andy” Aastad, then vice-president of marketing.
At its peak of operations, up to 177 people were employed. The number of employees then declined to just 80 in late 1969 and the early part of 1970 when the constant problem of the finance reemerged. Pacific Airmotive stated that it would not continue to absorb losses incurred by the local firm. Due to the shortage of cash, helicopters were not finished because some required parts could not be paid for. In October 1969, Jack Christensen, who had been at the helm of the company since its founding, resigned his position.

1970

The Purex Corporation shut down Enstrom operations on February 13, 1970, a day which later became known as “black Friday”, saying that sales had failed to materialize as expected. Only 5 helicopters were sold in the 6 months before the closure, and only 1 in the preceding 3 months. The operating losses were becoming so severe and the outlook for recovery so poor, that the decision to close down and sell off the operation became obvious to management. The assets of the firm were offered for sale.
For the 80 employees, as well as most of Menominee residents, it was a dreaded day not soon to be forgotten. The closing of the company led many to believe that Menominee was in the midst of an economic depression with little future for a recovery.
A period of time followed during which much effort was expended attempting to find a future for the firm. On December 24, 1970 the Franklin Capital Corporation of Livonia (Michigan) arrived in Menominee to announce its intention to purchase the R. J. Enstrom Corporation with the declared aim to resume series manufacturing. 
The inhabitants of the region were happy about the nice surprise that came just on Christmas Eve, except that a few weeks later Franklin Capital Corporation chose not to complete the deal.
It was at that moment that Francis Lee Bailey (1930-2021), whose prowess as a criminal lawyer in the preceding decade has made him one the most famed attorneys in the world, entered the scene.

Francis Lee Bailey carried the ball in his own-capable hands, raised the money and bought the company.
Efforts to restart series production of the F-28 culminated on January 23, 1971 when he arrived at Menominee County Airport to announce that he had purchased Enstrom, which was renamed Enstrom Helicopter Corporation. In the end, for area residents nothing about the good news Enstrom announced on Christmas Eve changed, except the owner.
Francis Lee Bailey was considered an expert in the field of business aviation, he flew and owned airplanes as well as a Brantly B-2B helicopter.
Bailey was confident the Enstrom model and the Brantly B-2B, formerly produced by Brantly Helicopter Corporation, had great potential. He stated that the Brantly Helicopter Corporation “would be acquired by Enstrom with the combined operation to be located here in Menominee”.
Jack Christensen, former president of the R. J. Enstrom Corporation, was rehired and named by Francis Lee Bailey vice president and general manager. One of his first challenges was to rehire the employees who had been laid off. However only some of them accepted the offer. Among them some key personnel.
Paul L. Schultz, who had been vice president of engineering with the “old” Enstrom Corporation, was renamed to that position. When Bailey took over there were about 50 Enstrom F-28s flying.
Under the direction of Francis Lee Bailey, Enstrom picked up speed again. Production and sales increased dramatically.

1971

On May 14, 1971 Enstrom unveiled a new possible use of its F-28A. At St. Joseph-Lloyd Hospital a new version of the firm’s police and rescue model known as the Enstrom Guardian II was presented. This new version was equipped with a specially designed nose able to carry an injured person on a litter. Conceived and reared at Enstrom, it allowed the conversion of the helicopter from a three-seater to emergency use quickly, and with no effect on the helicopter’s stability. 

1972

On September 30, 1972 residents of the region were invited to join Enstrom Helicopter Corporation in celebrating the production of its 100th helicopter, an Enstrom F-28A delivered to Skytel Aviation based in Fort Lauderdale, Florida.

That same day, hundreds watched Francis Lee Bailey symbolically started digging the foundations for a new factory extension. The new 31,400 square foot (2,920 sq meters) additional manufacturing space cost $250,000 and allowed all phases of production to be completed under one roof. Until that moment, several buildings in Menominee were used, some for production and some for assembly.

1973

The new Enstrom 280 Shark was unveiled in January 1973 at the 25th annual convention of the Helicopter Association of America in Las Vegas. During the convention Bailey told a Herald-Leader journalist that his company was working on different projects. One of them was a 2-plus-2 model with a narrower cockpit for more speed. He also stated that Enstrom was considering the installation of a Bendix autopilot for the 280 Shark as it would enable hands-off flight for cruising similar to fixed-wing aircraft.
In 1977 the 280 Shark, designed by Robert Jenny of Enstrom Corporation and Gregory Fossella Associates Inc. of Boston, was selected by a jury of industrial designers working for internationally prestigious Fortune Magazine, as one of the best designed factory-made products available in America.
In March 1973 Enstrom manufactured about seven F-28A helicopters per month and employed a work force of about 90 people.
In May 1973 Francis Lee Bailey annouced that a distributorship contract had been signed with Spooner Aviation of Shoreham, Sussex, England directed by Roy Spooner. The manager of the company was Dennis Kenyon (1932-2020), who later became well known throughout the helicopter and airshow world for his astonishing helicopter flying displays, particularly in Enstroms.
Dennis Kenyon visited Enstrom factory where he saw its chief pilot Mike Meger flying an aerobatic display with an F-28A, and a new fire was lit. Dannis Kenyon represented Great Britain in four World Helicopter Championships, winning the aerobatic freestyle title in 1992. He made his last display in July 2018 in an Enstrom Shark at the age of 85! 
On August 25, 1973 area residents were invited at Menominee airport for the grand opening of the new plant facilities. The public was invited to tour the plant and Mike Meger, who won the freestyle event during the world helicopter competition organized on June 23-28, 1973 in Middle Wallop (England), gave a stunning air demonstration using an Enstrom F-28A. 
Meger was a WWII veteran. During the war he piloted B-24s, completing more than 50 missions over Africa and Italy. By the time he won the championship, he had over 14,000 hours on helicopters, and over 4,000 hours on aeroplanes.

1975

On December 16, 1975 an article published on the Menominee Herald-Leader annonunced that Enstrom Helicopter Corporation was considering a new expansion program expected to begin in 1978. The expansion (cost 1 million dollars) was due to an expected backlog of the new turbo-charged model helicopters (F-28C and 280 Shark). Bailey affirmed that “the expansion will be conducted in two stages. We will expand at the present site to the north and then will also expand to the south during the second phase. The expansion depends a lot on how sales go. There is the possibility of going to three shifts and employing about 175 additional men. The new turbo-charged models were requested by 42 firms”.
With the appearance of the new F-280 (certified on September 13, 1974), and the F-28C (certified on December 8, 1975) with better performance due to the turbocharged engine, production of the Enstrom F-28A was planned to end.

1976

In March 1976 Ernest Medina, vice-president of the Enstrom Helicopter Corporation, met local media to give additional information about the layoff of 50 Enstrom employees. Solicited by the journalists, he explained that the temporary layoff was due to a shortage of critical parts such as main gear box housings and shafts. Enstrom employed 133 people. Medina stated that the company was in a good financial position, but that a delay in receiving money transfers from foreign countries for finished helicopters resulted in a decrease in cash flow. Most employees were later re-hired.
In August, the company announced that it was planning a new expansion program. Included in the plans was a new 84 by 240 foot (25 x 73 meters) building addition and eventual hiring of new employees. Bailey said that several countries had expressed interest in buying Enstrom helicopters, and there was a large number of back orders.
In the course of 1976, with the introduction of the new model 280 Shark and F-28C, series production of the F-28A ceased.
Up until 1976, this version is the one produced in the largest number with 316 units manufactured between 1968 and 1976 (s/n 15 to 330 excluding s/n 304). 

The story of Enstrom Helicopters of course continues, but in a separate article to be published. 

Civil employement

The Enstrom F-28A was mainly used for pilot training, private flights, photographic flights, traffic surveillance, newsreporting for newspapers, radio and television stations, and less frequently in agriculture to spray or dust crops.
In the past, various police forces used this aircraft as a 'flying observation post' in support of road police units.
Among the operators were for example Oakland County Sheriff’s department in Pontiac, Michigan, New Jersey State Police and DeKalb County Police Department.
Back in 1969 the  Police Department of Pasadena, California purchased 2 Enstrom F-28As and set up its helicopter section on a purely experimental basis. Four officers were appointed to it and started flight training. First patrols were flown on July 1, 1970 with a crew of 2 officers (1 pilot and 1 observer).

The patrol program included helicopters on two five-hours shifts per day. Personnel included 3 policemen pilots, 3 observers and 1 helicopter mechanic. The helicopters patrolled areas of particular crimes and were highly successful. Day patrols were flown at 500 ft, night shifts at 800 ft. According to a report written in 1977, after about 7 years nearly 18,000 hours of operation were logged by the F-28As. One of the pilots retired after 6 years and 3,425 accident-free hours.

Technical description

The following technical information is extracted from the maintenance manual published in 1972. 
The airframe of the Enstrom F-28A is composed of three main sections: the tail cone assembly, cabin assembly and the centre section.
The tail cone assembly is a semi-monocoque structure and attaches to the pylon assembly with three bolts for easy removal and installation. 
An all-metal, fixed position stabilizer adjusted to -4° is installed on the tail cone assembly for longitudinal stability.
The cabin is fabricated from molded fiberglass and is an integral unit. It is attached to the forward side of the pylon assembly by six bolts and encompasses the structural aluminum seat portion plus instrument panel, cyclic, collective, and tail rotor controls. The tinted Plexiglas windshield and full glass doors, plus upper and lower deck windows, provide good visibility.

The cabin interior is a full three-place, side-by-side seating arrangement (width 155 cm or 61 inches) for maximum pilot and passenger comfort and safety. The instrument panel is on the horizontal plane for more natural scanning and is conveniently located for dual pilot viewing.
The pylon structure assembly is fabricated from steel tubing and houses the engine, the belt engagement and idler assembly and clutch. The landing gear attaches to the lower section of the pylon structure at four points.
Ground handling wheels are provided for moving the helicopter and can be easily removed. Four air-oil struts soften landing loads and aid in leveling the helicopter while on the ground.

Cabin heat

The cabin heat control is located at the left-hand side of the pilot’s seat on the floor. By moving the control in or out, the pilot regulates the amount of cabin heat through the output louvers located in the center of the floor under the instrument panel.

Baggage compartment

The baggage storage compartment is located in the tail cone assembly aft of the engine compartment. Access to the area is through a single door located on the right-hand side and has a lock for external locking. The capacity of the compartment is approximately 0.3 cubic metres (11 cu ft) and has an allowable loading capacity of 27/60 kg/lbs.

Power plant

The Enstrom F-28A is powered by a four cylinder Lycoming HIO-360-C1A (or HIO-360-C1B) 153/205 kW/hp. The engine is air cooled and installed horizontally. It employs a wet sump lubrication system. A bayonet-type oil quantity gauge with graduated markings is part of the oil tank filler cap and is accessible through the left-hand side cowling of the engine. Engine oil cooling is accomplished by an oil cooler with thermostatic valves and by-pass provisions. It is located on the right-hand side of the engine compartment. Oil temperature and pressure gauges are located on the instrument panel. The engine weighs 146/322 kg/lbs and consumes about 55 litres/h (14-15 USG/h) of 100/130 octane fuel (100 LL).

Air/filter induction system

The air filter is installed in the induction plenum chamber which is located in the bottom of the lower cowling below the engine.
The fuel injector requires an alternate air source in the event the air filter becomes ice covered or plugged. A spring-loaded door between the engine compartment and the air filter housing is designed to open as pressure builds up due to a clogged filter. This provides warm air from the engine compartment to the fuel injector.

Fuel system

The system consists of two interconnected glass-fibre fuel tanks which feed simultaneously to the engine. They are located on the left and right side of the aircraft over the engine compartment. The tanks have an individual fuel capacity of 15 USG (56.7 litres)  each (100/130 octane). Each fuel tank is gravity fed to a central distributing line which connects to the electric boost pump and engine driven pump. The fuel control valve is an off-on type and is located on the firewall next to the pilot’s left shoulder. Each tank has an individual drain valve at the bottom. There is also a main gascolator filter located aft of the firewall in the engine compartment which extends beyond the side panel.
The fuel boost pump switch and fuel pressure warning lights are located on the instrument panel. 

Rotor system

The main rotor is a three-blade, fully articulated system this means that the blades are hinge-mounted to be free to lead-lag, flap and feather. The fully articulated system in the F-28A provides smooth control responses in all modes of flight and due to the kinetic energy stored in the heavy rotor blades, allows for easy-to-perform safe autorotation landings in the event of a power failure. The rotor assembly is mechanically simple and consists of three all-metal bonded blades, upper and lower rotor hub plates, universal blocks, blade grip assemblies and lead lag hydraulic dampers. The excellent hydraulic dampers govern the lead-lag motion and aid in the dynamic stability of the F-28A. The main rotor rotates at 330 rpm (autorotation range 313-385 rpm). 

Main rotor blade chord 24.13 cm (9.5”) and main rotor disk area 74.78 mq (805 sq ft).
One of the distinctive characteristics of the Enstrom F-28A in the lack of exposed pitch change links on the main rotor. These are installed inside the main rotor shaft, helping to lower aerodynamic drag.
The anti-torque rotor counteracts the torque of the main rotor and functions to maintain or change the helicopter heading. The tail rotor is a two-bladed, teetering, delta-hinge type assembly. Each blade is connected to a common hub. Blade pitch change is accomplished by movement of the pilot’s directional control pedals that are connected to a pitch control assembly mounted on the tail rotor 90° gear box.  Blade pitch provides control of torque and change of directional headings. Power to drive the tail rotor is taken from the input shaft of the main transmission. The tail rotor rotates at 2,365 rpm. Tail rotor blade chord 8.6 cm (3.375” inches).

Clutch engaging lever

The main rotor is driven by a single “Poly-V” belt from the engine to the ring and pinion reduction drive. The clutch engagement lever is located to the right side of the pilot’s seat on the forward face of the seat structure. The clutch lever is provided as a means of engaging and disengaging the rotor drive system. The rotor drive system is engaged by pulling the clutch lever upward and rearward until the lever hits the stop and the warning light goes out. The handle can then be stowed by lifting it straight up and pivoting it down to the floor. When it is in the stowed position, the handle lie flat on the floor. 

Transmission system

The main transmission unit provides an 8.7871:1 reduction ratio between the engine and the main rotor. The transmission incorporates a free-wheeling unit in the upper pulley assembly which is mounted on the output pinion shaft. The free-wheeling unit provides a disconnect from the engine in the event of a power failure and permits the main and tail rotors to rotate in order to accomplish safe autorotation landings.

Six pints of oil are used in the transmission. The main rotor transmission has a sight gauge which is located on the aft right-hand side and is visible through an opening in the baggage compartment. A main rotor transmission temperature gauge is located on the instrument panel and is red-lined at 220° F.
The tail rotor trasmission, mounted at the aft end of the tail cone, supports and drives the tail rotor. The tail rotor transmission is equipped with a self-contained lubricant supply and level gauge at the rear of the housing with a magnetic plug that can be removed to inspect for metal particles.

Flight controls

Cyclic trim and center feel will be provided by electric motor actuated spring trim capsules controlled by a switch on the pilot’s stick. Collective pitch throttle coordination is provided by a very simple arrangement of offset centers in the throttle linkage. The throttle grip rotates approximately 120 degrees from closed to full open. Tail rotor control is a simple cable system operating a set of bell cranks which are mounted external to the tail rotor gear box.

Weight and dimensions

The Enstrom F-28A has a MTOW of 975 kg (2,150 lbs) and the empty weight (no accessories, fuel or oil) is 658 kg (1,450 lbs). The useful load is 317 kg (700 lbs).

Optional equipment

The optional equipment list for the Enstrom F-28A included many accessories, some of which are listed here: dual controls, snow shoes, litter kit (Stokes type litters could be installed on the right or both sides of the fuselage), throttle correlator, cabin heater and float landing gear. The float installation kit consists of two multi-cell (5 compartments) inflatable floats, attachment fittings, right engine side cowl modified for installation of induction air box, relocated pitot tube, lenghtened universal blocks, tail rotor strike indicators, and two landing lights.
Another optional piece of equipment is the external mounting of the auxiliary fuel tank. When installed, it permits an additional 22 USG of fuel capacity. It can be installed on the right side only.

The cargo hook installation allows the transportation of external loads. External load limit is 227 kg (500 lbs), with MTOW remaining at 975 kg (2,150 lbs).

Performance

The table below shows the main performance of the Enstrom F-28A in standard atmospheric conditions and no wind conditions:

The Enstrom F-28A in Switzerland

A total of five Enstrom F-28As were registered in Switzerland with the following call-signs: HB-XEA, HB-XEB, HB-XEC, HB-XED and HB-XER.  The first registered, HB-XEA, was purchased during the summer of 1973 by Werner and Ruedi Eichenberger who managed a flight school.

The Eichenberger Flugschule in Buttwil, which had been operating since July 11, 1970 at the small Aargau airport in Buttwil, became Enstrom’s main operator (and brand representative) in Switzerland.
Werner Eichenberger (1927-2020) a glider and aeroplane flight instructor, went to Menominee in June 1973 for a period of two weeks with the purpose of obtaining primary flight training. During the visit he observed some maintenance and assembly procedures. Back in Switzeland he obtained his helicopter pilot's licence and later became a helicopter flight instructor. 
With more than 6,000 hours of flight on the F-28/280 series, Werner Eichenberger is almost certainly the pilot who logged the most hours on the Enstrom helicopters in Switzerland. 
The Swiss Enstrom F-28As were mainly used for flight school, scenic and photographic flights.
These helicopters, which were frequently leased to private pilots, were victims of various flight accidents. 
HB-XEA was damaged by Werner Eichenberger on September 2, 1973 in Bad Ragaz/GR. The pilot, who had obtained his licence only a few weeks before, had 43h30m of flight time to his credit and was surprised by a loss of engine power on approach. An abrupt landing ensued, which seriously damaged the helicopter. The successive inquiry established that the incident was caused by an engine mechanical problem. After being repaired, the helicopter was used until it was sold to an English buyer who registered it as G-KOLY in 1976.
Other Swiss operators included Air Material and Flight Yourself. 
All the Swiss F-28As incurred in-flight accidents. Some were caused by inexperienced pilots while others were caused by mechanical problems.

On May 18, 1978 HB-XED was damaged at Pompaples/VD in a forced landing following a failure of one of upper jack strut bearings. The investigation revealed that the cause of the failure was a lack of lubrication.
The problem had been reported to operators by the manufacturer the previous year in ‘Service information letter no. 0059 issued on February 15, 1977.

The Enstrom F-28A that remained longest in service was HB-XER. It was used from June 1975 to May 1981 by Air Material and later until February 1989 by Robert Ducret. It was then sold in England where it continued to fly under the new registration G-BBPL.