Composites don’t make much difference in weight but enable more efficient man

An All-composites Learjet

When Bombardier Aerospace launched its newest from-the-ground-up midsize Learjet-now named the Learjet 85-the company's chief designers made two key decisions. The first, not announced until well after the launch, was that the structure-including wings, fuselage and tail-would be made of composite materials instead of the traditional aluminum used for most business jets. The second was to stick with classic Learjet styling.

Designing any new airplane allows a manufacturer the rare opportunity to break out of the box that defines a particular model. Since Bill Lear almost single-handedly created the (relatively) light business jet market in the 1960s with his iconic Learjet, the model lineup has grown but always retained its original shape, with a T-tail, skinny wings and a thin tubular fuselage.

With the Learjet 85, Bombardier designers have not only honored Lear's legacy, but also engineered what will be the largest and longest range Learjet ever. Those features are directly attributable to the model's composite construction, which uses carbon fiber and resin molded and baked into shape to make a strong and lighter airframe, and its mature yet efficient jet engines (Pratt & Whitney Canada PW307Bs). The composites don't make much difference in weight but do enable more efficient manufacturing, replacing thousands of metal parts with a few large components. Interior space is maximized, too, because composites are strong enough in smaller dimensions. Metal fuselages, for example, require circular bulkheads that shrink the space between cabin walls. Composites allow for thinner fuselage walls and more interior volume. Composites should also require less maintenance, but it will be many years before the service history can demonstrate this. While there are several other all-composite business and personal jets in the pipeline-some started well before the Learjet 85-the 85 could well be the first to make it to certification, production and customer deliveries.

With a 664-cubic-foot cabin, the model offers plenty of room for eight passengers in double-club seating, a full lavatory aft and a galley opposite the cabin entry door. Cabin height is 71 inches and the width is 73 inches at midline and 50 inches at the floor line.

Performance features include a comfortable 6,000-foot cabin altitude when flying at the maximum altitude of 49,000 feet, high-speed cruise of 470 knots, a long-range cruise speed of 448 knots and a 3,000-nautical-mile range with four passengers and two pilots. That range is sufficient to fly from Geneva to the Middle East or Canada and means no stops when flying across the U.S. or from North America to Brazil.

Bombardier expects certification and entry into service to occur in 2012 and anticipates no delays because of the insolvency of Grob Aerospace, which was slated to build the first prototypes. The composite structure of the Learjet 85 will be manufactured at Bombardier's Queretaro, Mexico facility and shipped to Wichita, Kan., for final assembly, interior completion, paint and delivery.

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