Frank Christensen says he once tried to buy the Pitts Special type certificate but was turned away by the price. That apparently bothered him, because he went out and designed his own family of kit-built sport biplanes, and the results were on view for the first time at Oshkosh 1977.
The criteria were: unlimited-class aerobatic performance; a two-place cockpit; all the creature comforts the Pitts lacked; attractive styling; and, last but in a way most essential, that the airplane should be amateur-built. To certificate and sell the airplane in the normal market would be too confining and too expen-sive, Christensen felt. By selling it as a kit, he could channel his expenditures where they belonged - into providing materials of the highest quality - instead of into justifying everything to the FAA.
The Eagle is a biplane with a swept symmetrical wing structure of built-up wooden ribs and spars. The Eagle's bubble canopy, hinged oh the right side of the airplane, slides back to unlock and swings aside to admit the pilot and passenger to a long, wide tandem cockpit with a single instrument panel in front and dual controls. The fuselage is built from welded steel tube and covered with metal back to the rear cockpit, then fabric the rest of the way aft. The fabric-covered wings are built with wood ribbing over spruce spars. The amateur builder has the option of buying 26 kits in sequence, starting with the ailerons, to test his dexterity.
Many parts are prefabricated or partially prefabricated, and the Eagle's steel-tube structures are welded at the factory. Christen kits include everything you need to build them. Price in 1982: $41,000 (includes complete kit). Kit less engine and propeller, costs $26,000. Units delivered to June 1982: 450 started, 100 flying.
The Eagle I and I-F will be the single-place unlimited competition version, powered by a 260-horsepower Lycoming aerobatic engine; the F means fixed-pitch. The I model will compete at 1,262 pounds and carry 1,478 pounds at gross with a wing loading of 11.82 pounds per square foot. Its empty-weight power loading is 3.83 lbs. per hp. With a rate of climb of 2,640 fpm, it offers social climbers a vertical penetration of 1,650 feet.
The II, by comparison, is pure luxury, featuring a spacious forward cockpit with no intruding instructor's feet and a huge bubble canopy molded of a single hunk of clear plastic. It rides behind 200 hp Lycoming AEIO-360-AlD and a second -F version, except that this time, the F means the 260-hp en-gine of the I model. Its gross weight is 1,578 pounds, and it provides for an electrical system and a radio.
Both models are stressed to +9and- 6 Gs and have roll rates of 187 degrees per second and a power loading of 5.25 lbs/hp.
For a second time, Christensen turned his attention toward the Pitts factory (located at Afton, in the middle of nowhere in Wyoming). This time, he was successful: Pitts Aerobatics is now part of Christen Industries, and Christensen wants the Pitts and the Eagle, formerly arch rivals in the field of competition aerobatics, to live in harmony as stablemates.
Christensen himself, of course, developed the Eagle as a refined Pitts after purchase negotiations with Curtis Pitts fell through in the mid-1970s. Although the very existence of the Eagle testifies to which airplane Christensen thinks is better, he is quick to assure the Pitts purists that their airplane has its own special place in the past and in the future.
Christensen had no plans to axe the Pitts marque, but one model, the 200-hp two-seat S-2A, will mutate to become the factory-built Eagle. This is a crucial reason behind Christen Industries' acquisition of Pitts Aerobatics. It is the most direct route to a factory-built, certificated Eagle. For the purposes of certification, the factory-built Eagle will actually be a Pitts S-2A modified to Eagle standards.
The Christen Eagle is very similar to the S-2A: both share the same airfoil, span, length, engine and propeller, but the Eagle has less lower-wing dihedral, a further-aft CG, different cowling and landing gear, modified ailerons and linkages and a more spacious and better designed interior. Christensen sees the Eagle as being almost imperceptibly different: "Like a washed car, it runs smoother."
At the time he was developing the Eagle, Christensen was convinced that an unusual-ly complete kit would appeal to a larger market than would comparable homebuilts or factory-built airplanes. With 550 kits sold by 1975, it seems he was right.
The Eagle II is a two-seat sporting biplane that can be used for unlimited-class aerobatics as well as for advanced training. The Eagle II and II-F have a full electrical system (starter-alternator-battery). The Eagle II uses a 200-hp engine with constant-speed propeller. The Eagle II-F uses a 260-hp engine with fixed-pitch propeller. Characterized by their startling paint scheme, the Eagles feature swept symmetrical wings, a strong fuselage, and a blown canopy that covers both cockpits. With a roll rate of 187 degrees/second and a power loading of 7.89 lbs./hp, the Eagle is a strong performer. The fuselage is finished in metal from the cowling back to the rear cockpit. The midsection, all the way to the empennage, is covered in fabric. The fabric-covered wings are built with aluminum ribbing over spruce spars. The amateur builder has the option of buying 25 kits in sequence, starting with the ailerons, to test his or her dexterity.
The Eagle II, first offered in kit form in 1977, was still available in 1998 at US$55,000.
Engine: Lycoming AEIO-360-A1D, 200 hp.
Propeller: Hartzell® HC-C2YK-4/C7666A Constant Speed
Speed max: 184 mph.
Never Exceeded Speed: 210 mph
Cruise: 165 mph.
Range: 380 sm.
Stall: 58 mph.
ROC: 2100 fpm.
Take-off dist: 1450 ft.
Landing dist: 2100 ft.
Service ceiling: 22,000 ft.
Wing Loading: 12.62 lb/sqft
Power Loading: g 5.13 lb/sqft
Length: 17 feet 11 inches
Height: 6 feet 6 inches
Wing Span : 19 feet 11 inches
Wing area: 125 sq.ft.
Gross Weight: 1578 pounds
Competition Weight: 1290 pounds (with 190 pound pilot)
Empty Weight: 1025 pounds
Useful Load: 553 pounds
Roll Rate: 187 Degrees/second
Baggage Allowance: 30 pounds
Fuel Capacity: 25 U.S. Gallons (24 Usable)
Structural Limits: +6g, -4g Operational
Landing gear: tail wheel.
Aviat Eagle II
Engine: Lycoming IO-360A1D, 200 hp.
Length: 18.5 ft.
Wing span: 19.9 ft.
Wingarea: 125 sq.ft.
Empty wt: 1125 lbs.
Mtow: 1578 lbs.
Fuel cap: 25 USG.
Undercarriage: Tail wheel.
Cruise: 165 mph.
Stall: 58 mph.
Range: 440 sm.
ROC: 2100 fpm.
To dist: 1450 ft.
Ldg dist: 2100 ft.