3840 The Learjet 85: Historical Evolution, Critical Challenges and Lessons from a Misguided Program
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Paper
Abstract
The story of the Learjet 85 (LJ85) starts with the Learjet 60 (LJ60). In 2004 the LJ60 was the largest Learjet in production, however it suffered from many problems that were causing it to lose valuable market share. Foremost was that the LJ60 used the same basic wing and main landing gear (MLG) design that traced its lineage all the way back to the Learjet 23 in the early 1960’s. Based off the original Swiss fighter jet wing design, this design was thin, very strong, high speed optimized and originally came equipped with tip tanks for additional fuel storage. It was now being used on a plane that weighed twice as much, had winglets instead of tip tanks and was limited to the same small size wheels. The following issues were the result:
1. Poor landing performance due to high landing speeds and undersized brakes
2. Large fuselage tank required due to small wing fuel volume
3. CG issues due to short MAC length and large fuel moment change
By the Summer of 2005, Learjet was ready for an internal launch of our new project. It was a design that would have instantly been recognized as a Learjet in both the performance and the external lines. Heritage aluminum structure and classic manual flight control systems would be used in line with all previous models. Newer LJ45 style systems and wing aerodynamics would be combined with a lengthened LJ60 fuselage to create a low-cost successor to the long in the tooth LJ60. It was called various official program names over the next year, but many of the employees liked to call it the Learjet 65.
