Stevens Aviation celebrated delivery of the first Lear4Ever-modified Learjet 35 at a ceremony held at the company’s Greenville, S.C. headquarters on August 26. The first modified Learjet 35 was delivered to Steve Bass, who bought the airplane from Stevens after the mods were accomplished. In addition to interior and exterior refurb work, the main elements of the Lear4Ever program are new Universal Avionics glass-panel avionics with synthetic vision and Raisbeck ZR Lite performance modifications.
The Learjet 35 is the second Learjet and the second Part 25 jet to receive FAA approval for installation of the Universal Avionics package. Stevens Aviation last year certified the Universal installation in a Learjet 25 owned by long-time Learjet pilot and operator Roger Humiston, who was on hand to witness the delivery of the first Lear4Ever Learjet 35. Much of the work done on Humiston’s Learjet 25 helped Stevens get a jump start on the Learjet 35 program. Stevens is an authorized Learjet service center, and the modification can be done at any of its five locations.
The Learjet 35 is an ideal airframe for this type of upgrade, according to Frank Golden, a technical sales specialist for Stevens Aviation. Some 650 Learjet 35s are still flying in the civil sector, with a few more in military service. And the Learjet 35 airframe has no life limit, just a mandatory 12,000-hour wing-fuselage demate inspection. “You can fly forever as long as you do everything in the maintenance manual,” Golden said. Stevens plans to offer the mods for Learjet 25s as well, although the market may be more limited given the 25’s less efficient GE CJ610 engines.
Bass’s Learjet 35 is a 1982 model that had 11,400 hours on the airframe when Stevens bought it to perform the first Lear4Ever modifications on a model 35. During the six months it took to do this first Learjet 35, Stevens technicians performed the wing demate inspection. The project would be much faster if just the avionics upgrade were being performed, Golden said.
The FAA granted 10 avionics STCs to Stevens Aviation for the Lear4Ever program. Along with pounds of old wiring, the Stevens technicians removed the Learjet 35’s heavy “iron” gyros (Jet Electronics and Technology Vertisyns) and old avionics. The only avionics wiring that wasn’t removed was the wiring between the autopilot and servos, because the existing autopilot was retained.
Mounting the Universal EFI-890R three-LCD panels in the Learjet 35’s panel is challenging because a large outflow valve is installed on the forward pressure bulkhead right in front of the center of the instrument panel. Stevens faced the same problem in the Learjet 25 installation, and the Universal displays fit just right, with a small amount of space left between the outflow valve and the back of the center display.
To make sure that all the equipment fits correctly, Stevens technicians built a full-size plywood model of the Learjet’s nose structure to fit all the new avionics and route the wiring. Now the company has a pre-assembled fixture that it can use to begin manufacturing wiring harnesses before a customer’s airplane arrives at the hangar to speed up the installation job. “Everything is wrung out before we put it in,” Golden said, “right to the bulkhead connectors.”
In addition to the Universal EFI-890R system with dual UNS-1Fw FMSes, Vision-1 synthetic vision and TAWS, Bass’s Lear4Ever installation includes Avcon RVSM, dual Rockwell Collins AHS-1000 AHRS (replacing the iron gyros), L-3 GH-3100 emergency backup instrument, Rockwell Collins navcoms controlled by a Universal Avionics radio control unit with Rockwell CLT-23 as a backup control unit and WSI weather data.
The current Lear4Ever Learjet 35 mod retains the original engine instrumentation, although Universal has certified its engine-interface unit (EIU) on the Falcon 50, which, like the Learjet 35, is powered by Honeywell TFE731s. The Learjet 35 with the Universal 890R avionics could accommodate the EIU and display engine data either at the top of one of the center MFDs or on a fourth display, which could fit into the Learjet panel, according to Universal COO Paul DeHerrera. “It’s a slam dunk for us to install EIUs in the Lear4Ever,” he said.
Other Lear4Ever modifications include Avcon delta fins, Raisbeck ZR Lite horizontal winglets and flap trailing edges, a custom Stevens Aviation “Benchmark” interior with RosenView VX moving-map unit and DVD player and dual Flight Display Systems seven-inch LCDs and fresh exterior paint.
ZR Lite performance improvements include 25-percent faster time to climb, 3,000- to 4,000-foot higher initial cruise altitude, an increase in cruise speed, lower N1 and ITT at equal Mach, 5-percent decrease in block fuel at equal altitudes and Mach and
5- to 10-percent increased range. Takeoff performance also improves, thanks to a new 14-degree flap setting.