Raisbeck earns STC for Learjet 35/36ZR mod

Aviation International News » November 2004
December 18, 2007, 6:24 AM

After four years of development and almost 500 hours of flight testing, the Raisbeck ZR Lite System for the Learjet 35/36 has earned an STC.

According to James Raisbeck, CEO of Raisbeck Engineering, the system significantly increases aircraft performance. He said certification flight tests substantiated an overall cruise drag reduction of approximately 6 percent as well as drag reduction in all phases of flight from takeoff to landing.

“What we have been able to substantiate is an increased initial cruise altitude, higher cruise speed, longer range and reduced block fuel consumption,” Raisbeck told AIN. “The aircraft is capable of more payload or range from restricting airports such as Aspen. It also makes available to Lear 35/36 operators airports that the airplane could not previously use. At the same weight the Lear 35/36ZR Lite can take off from runways shorter by as much as 1,000 feet; or the airplane can take off from the same mtow-restricted airport up to 1,000 pounds heavier.”

The STC includes recontoured trailing-edge flaps, outboard trailing- edge horizontal winglets called bat-wings, wing leading-edge vortillons, a new takeoff flap speed schedule and new 14-degree takeoff flaps for improved field length performance.

Raisbeck likened batwings to horizontal winglets. “They tend to unload the lift adjacent to the airplane’s tip tanks and as a result significantly reduce the rolled-up vortices shed at the wing/tank junction,” he explained. The effect is to reduce overall drag at low speed, in climb conditions and during cruise up to and including Mmo.

According to Raisbeck, a major goal was to give the aircraft more docile stall characteristics. The company added to each wing leading edge two uniquely tailored vortillons similar to those found on the Gulfstream IV/450 and Learjet 40/45.

The operational result is a 6-percent increase in range (at equal fuel load), shorter times to climb, higher initial cruise altitudes, lower fuel-burn rates and an increased allowable mtow from higher-altitude airports and shorter sea-level runways.

The package is made primarily of advanced composite material so the net installed weight for the entire kit is only 32 pounds. Raisbeck Engineering is directly supervising the first 10 installations at Galvin Flying Service, Seattle. Subsequent installations will be available at other Learjet major maintenance facilities.

Raisbeck has slashed the price to $94,500 (plus installation) from the original $260,000 (uninstalled). In April, when the company still hadn’t received any takers, it announced it was seeking at least 20 “conditional” orders at $200,000 (installed, including paint), to justify finishing the program.

Raisbeck is now taking order positions for this year and next year.

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