The FAA has awarded multiple supplemental type certificates (STCs) to Stevens Aviation for a comprehensive avionics and airframe modification package for the Learjet 35 called the Lear4Ever program. Based on an up-close look at the airplane used for certification, the upgrade appears to deliver on early promises and is sure to pique the interest of operators of the iconic business twinjet.
The first modified Learjet 35 was delivered on August 26 to Steve Bass at a ceremony held at Stevens Aviation’s Greenville, S.C. base, where the work on the Learjet was accomplished. In addition to interior and exterior refurb work, the main elements of the Lear4Ever program are new Universal Avionics glass panel displays with synthetic vision and Raisbeck ZR Lite performance modifications. The first Lear4Ever Learjet 35 is at the NBAA static display, and Stevens is also showing demos of the Universal EFI-890R avionics package in a fuselage mockup at its booth (No. 5400).
The Learjet 35 is the second Learjet and the second Part 25 jet to receive FAA approval for installation of the Universal Avionics EFI-890R package. Stevens Aviation last year certified the Universal installation in a Learjet 25, and much of that work helped the company develop the Learjet 35 program. Stevens is also an authorized Learjet service center, and the modifications can be done at any of its locations.
The Learjet 35 is an ideal airframe for this type of upgrade, according to Frank Golden, a technical sales specialist for Stevens Aviation. More than 650 Learjet 35s are still flying, 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.
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 mod on a Model 35. During the six months it took to do this first Learjet 35, Stevens technicians also performed the wing demate inspection. The project would be much faster if just the avionics upgrade were being performed, Golden said, but with all the other modifications, “It’s really a six-month project.”
The FAA granted 10 avionics STCs to Stevens Aviation for the Lear4Ever program. Along with pounds of old wiring, Stevens’s technicians removed the Learjet 35’s heavy “iron” gyros (Jet Electronics and Technology Vertisyns) and most of the old avionics. The only avionics wiring that wasn’t removed was that between the autopilot and servos, as the existing autopilot was retained.
Installing the three-LCD Universal EFI-890R system in the Learjet 35’s panel is challenging because a large outflow valve is mounted on the forward pressure bulkhead 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’s technicians built a full-size plywood model of the Learjet’s nose structure for all the new avionics and wiring. Now Stevens has a pre-assembled fixture that it can use to begin manufacturing wiring harnesses before a customer’s airplane arrives at the hangar, and this speeds up the 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 FMS units, Vision 1 synthetic vision and TAWS, Bass’s Lear4Ever installation includes Avcon RVSM upgrades; 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 receiver.
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 TFE731 engines. The Learjet 35 with the Universal EFI-890R avionics could accommodate the EIU and display engine data either at the top of the center MFD 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, although it will require another STC.
Other Lear4Ever modifications include Avcon delta fins, Raisbeck Engineering ZR Lite horizontal winglets and flap trailing edges plus aft fuselage locker, fresh exterior paint and a custom Stevens Aviation “Benchmark” interior with RosenView VX moving-map unit and DVD player and dual Flight Display Systems seven-inch LCDs.