The latest Learjet sets the stage for the company's future
In this age of advertising hype, the word new is probably the most well-worn term in the English language. In the case of the Learjet 45, though, the description fits, but you might not notice it at first glance. The shapely 45 does indeed look right at home in the Learjet product line, which also includes the 31A and the 60.
But make no mistake, the Learjet 45 is all new — well, almost. The 45's nosewheel is interchangeable with the one on the 31A, admits Bill Greer, vice president of engineering at Learjet.
Because the 45 relies on the same classic good looks employed by the previous Learjets — a shape that now dates back more than 30 years — one might assume that the marketing department won out over the engineers. The engineers have no complaints, however. They admit that even when starting with a clean sheet of paper, they could not design a more efficient planform that would fit the Learjet 45's mission requirements.
The 45 looks much like its siblings, but looks can most certainly be deceiving.
Global markets
The 45 is the company's first all-new design since Bill Lear developed the Lear Jet 23 in the early 1960s. In developing the 45, Learjet took advantage of all the progress in engineering and manufacturing that has occurred since then. In addition, the company leveraged the manufacturing prowess of its sister companies under the Bombardier, Incorporated, umbrella. For example, de Havilland in Toronto did the detailed wing design and is manufacturing the wing. Short Brothers of Belfast, Northern Ireland, another Bombardier company, took on the details of the fuselage design and manufacturing. Meanwhile, Learjet itself is managing the program and is responsible for final assembly at its Wichita plants. Learjet is also conducting all of the certification work.
Rounding out the 45's international stature are smaller components from more than a dozen other suppliers around the world.
The logistics of time zones, languages, and different computer programs took months to work out, according to Learjet officials. During the design phase, video conferencing with other parts of the world became a way of life for many Learjet engineers. But in the end, the pieces all came together and they all fit, thanks in large part to some very sophisticated computer software that was used to design the components. The computers not only aided the aerodynamic design, but they also will simplify manufacturing. The 45 has half as many parts as the older Learjet 35, greatly reducing manufacturing costs and time, and parts inventories.
The result, once all the electrons settled, was Learjet 45-001, which first flew on October 7, 1995. Since then, two other test aircraft have been constructed. They are scheduled to join the flight test program within the next few weeks. Certification is slated for late 1996, and first deliveries are expected in early 1997. Average flyaway price for a well-equipped Model 45 will be about $6 million. The 45's price and performance pit it against such entrenched competitors as the Cessna Citation V Ultra and the Raytheon Beechjet 400A.
From the left seat
According to James P. Dwyer, Learjet's chief of experimental flight test, February 17 was a red-letter day in the program. Pilots on that day first performed roll-control disconnects, testing a system that will permit pilots to fly the aircraft either by spoilerons or ailerons alone in the event the flight controls become jammed. Such redundancy in flight controls is required under the latest FAR Part 25 and European Joint Airworthiness certification criteria.
The 45 is equipped with full-time fly-by-wire spoilerons to supplement mechanical aileron control. If the ailerons were to become disabled, the pilot could still control roll by using the spoilerons. If the spoilerons jam, roll control can be managed from the copilot's side by using just the ailerons. Preparing for such roll- control disconnects will be a standard part of the Learjet 45 simulator training being developed by FlightSafety International.
Another unusual flight control system is the digitally controlled auto-configuration trim system. That system automatically adjusts the operating speed of the elevator trim based on aircraft speed. At higher speeds where small trim changes are required, the system slows the trim speed. At slower airspeeds, the trim system speeds up, thereby decreasing pilot work load and increasing passenger comfort. The system also has the ability to adjust trim positions automatically, based on gear and flap configurations. Dwyer reports, however, that the 45 seems to require minimal trim manipulation with configuration changes.
All in the family
The Learjet 45 fills a hole in the company's product line. It is a place to step up to from the smaller Learjet 31A. For those needing a bit more range, Learjet offers the Model 60. The 45's 1,850-nautical mile IFR range is about 600 nm less than the 60's and about on par with the 35. A max operating speed of 0.81 Mach is about equal to the 35 and the 31A, while the max operating altitude of Flight Level 510 is 6,000 feet higher than the 35 and equal to the 31A and 60.
The 45's cabin, with an oval cross section, is longer and wider than that of the 60, but the Model 60's round fuselage has a larger circumference. The oval fuselage means greater headroom next to the sidewalls.
The 45's cabin can accommodate up to eight passengers, plus an aft lavatory and a forward refreshment center. A flat cabin floor makes it easy for the passengers to move about.
Up front, the pilots will fly behind a four-tube electronic flight instrumentation system by Honeywell. The 45 is the first mid-sized business jet to utilize Honeywell's Primus 1000 integrated avionics system and engine instrument/crew advisory system (EICAS). The Primus 1000's four 8 2 7-inch tubes depict dual primary flight displays, a multi-function display, and the EICAS display. The standard Primus 650 color radar system uses Honeywell's rain echo attenuation compensation technique (React), which detects and compensates for attenuation caused by heavy rainfall. The optional Primus 870 radar system adds Doppler turbulence detection to the pot, giving the pilots even more information to work with.
Lofting the Learjet 45 to FL510 are a pair of AlliedSignal TFE731-20 turbofans, each producing 3,500 pounds of thrust at takeoff. Takeoff distance at a maximum gross weight of 19,500 pounds is predicted to be 4,200 feet. Landing distance should work out to be 2,900 feet.
The performance numbers are typical of the rest of the Learjet family. What sets the new 45 apart from its siblings is the fact that it is a brand-new model, a design with growth in mind. Expect Learjet to launch a follow-on stretched airplane next. The manufacturing efficiencies made possible by the computer-aided design mean that Learjet will probably retire most of its current products over the next decade or so and replace them with variants of the Model 45. In that sense, the 45 may well be as important to the company as the revolutionary Lear Jet 23 was 30 years ago.
Related Articles
