Cobra Kit built helicopter design
|The Cobra's body is moulded with kevlar reinforced composite materials. This gave it a very futuristic look for its time.|
Based on a design by Harold Emigh, the new Kevlar based Cobra retains the reliability and component engineering of its time tested Commuter II.
There has never been an invention which sparked more intense desire in common man to possess it than the helicopter.
Since its beginnings in W W I I as a rescue and observation vehicle, its prominence in the world of aviation continues to grow. From the very first cumbersome Sikorskis which began operating from platforms and ships in very limited numbers in 1944 and 1945, to its presence in the first "helicopter war" - the Vietnam Conflict - where it spelled salvation for our troops and downed pilots but destruction for the enemy - the helicopter can perform magic as no other airplane or vehicle is capable.
Every day in every developed country, helicopters are at work: They transfer people from rooftop to airport; fight forrest fires in remote mountains and canyons; spray crops to increase the production of food for our hungry world; report on traffic congestion over radio and television stations; land on highways to transport accident victims to the nearest hospital; hover over escaping criminals, directing police ground units to their location; capture movie magic with vibrationless Tyler mounts holding heavy motion picture cameras; lift cumbersome heating and airconditioning equipment to rooftops; string powerlines across canyons; and drop off rock stars behind their stages when they want to avoid traffic jams and clamoring groupies.
|Engine type||Lycoming 0-320-A2B|
|Power||150hp @ 2700rpm|
|Fuel requirement||80 octane AvGas or auto fuel|
|Ignition||Dual (2 plugs/cylinder)|
|Fuel rate||10 gal/hr|
|Oil type||SAE 40/80|
|Range||200mi plus reserve|
|Seating||2-place side by side|
|The Cobra's main rotor drive transmission assembly, swashplate and tail rotor drive common on all models except the Predator|
They have been called many names - whirlybirds, fling-wings, wopwops, hoptycopters, choppers, and helos. Some of the military attack birds could hold more ordnance than many W W I I fighters. They are incredibly useful flying machines which have a reputation of being very hard to fly, hard to maintain and very expensive to own. Nevertheless, the helicopter is the "do everything" aircraft of choice. How did the world opterate before Igor had his brainstorm? With far less facility, I'm sure.
Years ago, there were a few fairly inexpensive helicopters, like Brantly and Enstrom, which met the demands of General Aviation pilots to a degree. Today, the least expensive in the Robinson R-22 _ a diminutive two-passenger with a small 150 Lycoming for power. The little Robinson is in great demand as a trainer and for use by airborne traffic reporters. Its still somewhat limited performance and still hefty pricetag, even by todays standards, kept the little R-22 from being the :helicopter in every garage" which many envisioned would be the norm in the years after W W I I.
One of the reasons why this has not yet been achieved is that a helicopter is a very complex machine. It has many crutial moving parts which must be scrupulously maintained. Furthermore, because they are not inherintly stable, they must be flown with both hands at all times. The use of helicopter controls is foreign to the learned flight responses of the fixed - wing pilots and a new set of reflexes must be learned. And many felt that only the expensive helicopters were safe.
Some homebuilders disagreed with the last statement. They thought that most of the design parameters were too complex, and that there must be an easier way to perform the same job. Some even beleive that the ultimate helicopter mechanisms have not yet been invented.
Companies like Rotorway in Arizona, directed by genius designer B.J. Schramm, have struggled for decades perfecting homebuilt helicopters only to be forced into bankrupcy because of rising costs and liability problems. Other helicopter companies have attempted to rise from the ashes of other helicopter companies. All who have attempted to conquer this market agree, though, that its an uphill battle.
The story of Harold "Pop" Emigh, respected North American Rockwell aeronautical engineer, and his Helicom Commuter I I homebuilt helicopter could almost be used as a textbook on the homebuilt helicopter business.
Harold Emigh's first contribution to private aircraft development was his Emigh Trojan, an advanced all - metal two - passenger light aircraft whose flying surfaces had the ribs on the outside of the wing. Furthermore, it was designed so that the right wing could be flipped over to become the left wing, etc., and the right horizontal fin and elevator could become the left horizontal fin and elevator, or stood on in and become the verticle fin and rudder. All parts were interchangeable, and when assembled, its performance was excellent. Lauded world - wide as a revolutionary design because of its ruggedness and simplicity, the Trojan easily won federal certification. Unfortunately, the aviation market was not ready for this tricycle - gear aircraft, so production dwindled and was shut down after a few years.
|The Emigh Trojan|
As an engineer, Emigh went on to design the Navajo Ballistic Missile System, the Polaris Navigation System, the B-70 and was called out of retirement to assist on the space recovery program. Throughout all those years, he gained considerable experience in stress analysis and the values of materials which would be necessary for reliability and production.
In 1954, after extensive testing and perfecting, Emigh brought out his Helicom helicopter which was sold continuously until the early 1970s as the Commuter I and I I. Hundreds were successfully built from Emigh kits and flown safely for many hours. While the design had great merit, the Helicom was somewhat similar in concept to the famous Bell 47, still being used around the world for various tasks. Extremely slow, but inexpensive to own
and operate, the Bell 47 was a classic helicopter design.
|Emigh Prototype Kit Helicopter|
How the Helicom Commuter I and I I homebuilt helicopters came about is an interesting story: Setting their goal on a lightweight and simple personal helicopter, Pop Emigh, his son Harold Emigh Jr., Program Director at North American Space conceprts, and Mr. William Foster began the mission of desigining and engineering. The drawing board received a real workout as plans and dimensions were devised - from the paper plans, to the machined parts, the first Helicom grew.
Several approaches to the construction of their helicopter were examined. Emigh wanted his helicopter to be simple, but not too simple, as people tend to take shortcuts if a design is too simple. After weight and power requirements were determined, the decision to use an aircraft engine seemed obvious. With minimal modifications, the Continental engine could provide the power - to - weight ratio required. Many Continentals were used in the single - seaters before the switch to Lycoming.
Emigh found that V-belts and pulleys would not suffice for the tail rotor drive. The adjustments would such attention that a simple drive shaft with universals would work much more easily, eliminating all stretch and alignment problems. The clutch design first incorporated was a common centrifugal type but Emigh did not like it. He designed a new style, one which would allow the engine to engage the blades more smoothly without jolting them as the old style tended to do.
NOTE: Cobra Helicopters are no longer in existence and their Cobra, Mustang and Predator helicopters are no longer in production. Article date 1990 courtesy Norm Goyer.