By 1978, Lear had preliminary performance figures, production schedules and was taking orders for his all-graphite epoxy airplane. Later that year he died, leaving his wife and a small team in Reno with the command to "finish it."
Early designs of the Lear Fan included an inverted V tail and Lycoming LTS-101 engines. As engineering and testing progressed after Lear's death, the inverted V tail was replaced by a Yshaped tail, the vertical stabilizer and rudder pointing straight down. The LTS-101 engines were traded in favor of Pratt & Whitney of Canada PT6B free-shaft turbines, and the engine intake-exhaust ports were moved down to the sides of the rear fuselage. But the design team never flinched from a total composite airframe. As design questions were answered, so were the enormous financial problems facing the company. In just 10 days, 200 limited partnerships at $150,000 each were sold, raising $30 million in capital. The British Government, searching for production projects to supply jobs in Northern Ireland, promised $50 million if the airplane would fly in 1980, and deposits on orders for 180 Lear Fans kicked in a reported $20 million more. If the airplane could just make its first flight in 1980 to get the British bucks, the money problems would be over.
Working round the clock, more than 300 employees at LearAvia wrapped up the thousands of details, pushing for a December 30 first flight. Too-tight brake pads heated up and blew a tire during taxi tests that day. Then an accidentally discharged fire extinguisher ended hopes of flying on the last day of 1980. However, British officials in Reno to see the first flight declared New Year's Day to be December 32, 1980. The airplane flew and at least part of Bill Lear's dying wish was fulfilled.
Hank Beaird, who flew the first Lear Jet test flight in 1963, commanded the first flight of the Lear Fan 2100. The 17-minute hop went so smoothly that Beaird and copilot Dennis Newton traded seats so Newton could make the first landing from the left side.
That first flight, pressured by the British funding deadline, was not a normal exercise. The landing gear remained down because no gear retraction mechanism was installed. Leaks in the wing fuel tanks had forced use of a makeshift fuselage tank. The normal high-resolution airdata boom was not even installed. But the airplane flew: hundreds of people watched and cheered, and national TV news covered the final achievement of a great inventor. Sixty cases of champagne enhanced the celebration afterward.
The theoretical advantages of the pusher design have Graphite fabric for a wing panel is laid out in preparation for a high pressure and temperature treatment in the autoclave. A prop working behind the fuselage forces its wash into free air, increasing efficiency because flow over the fuselage is disturbed less, thus lowering drag. And the Lear Fan twin-engine arrangement, with two engines sharing the same prop, enhances single-engine performance.
The very first airplanes were pushers, but no recent pusher designs, except some seaplanes, have been commercial successes. The Cessna 337 Skymaster addressed the benefits of a centerline-thrust twin, but for many reasons never lived up to its promise. At one point, Beech considered building a single-engine turboprop pusher, but the idea never reached prototype stage.
Two of the disadvantages of a pusher design are its center-of-gravity considerations and increased mechanical requirements. To maintain a reasonable CG range, the engine cannot be mounted too near the tail. A forward-mounted engine requires a drive shaft and its associated bearings and supports, increasing weight and complexity.
However, by using two turbine engines with a single propeller, Lear Fan engineers actually save weight when that installation is compared to a conventional twin turboprop. The Lear Fan design eliminates the extra weight of independent nacelles, uses lighter reduction gearboxes on the engines and saves the weight of a second propeller.
The PT6B-35 engines used in the Lear Fan are variations of the world's most popular turboprop engine. The engines have been flat rated from 850 to 650 shaft horsepower, which means they can develop full power to an altitude near 17,000 feet. The PT6 family of engines has an excellent reliability record, and carries a recommended time between overhaul of 3,500 hours. Differences between the engines used by the Lear Fan and those that power conventional turboprops are exhaust ports on a single side for the Lear Fan and a different reduction gearbox. Pratt & Whitney has also designed the engines for top performance at the 41,000 foot cruise ceiling of the Lear Fan.
Two large drive shafts transmit power from the engines to a Western Gear transmission mounted inside the tail of the Lear Fan. One-way sprag clutches connect the drive shafts to the gearbox, so when an engine is not delivering power it is automatically uncoupled. The design is similar to the free: wheeling overdrive transmissions used by many automobiles in the 1950s. If an engine fails, the sprag clutch automatically takes it off line and there is nothing for the pilot to do except, when convenient, turn the fuel control off.