Legacy Tails: Learjet 35A—Hold the Coffee

 - November 1, 2022, 8:33 AM
The cabin may be cramped, but speedy Learjet 35 flights don’t need to last very long.

Serving coffee on a Learjet 35 is a very bad idea. 

When Bill Lear created the Learjet in the early 1960s, he envisioned a small, fast, and simple airplane—a concept the marketplace embraced. His 20-series and the slightly elongated 30-series­ aircraft that followed sold briskly for more than 20 years, until long after he had left the company. Riding in the back of a Learjet once meant trips to the chiropractor and exercising bladder control, but it also meant the ultimate in aviation cool: speed.

Bill Lear first came to the idea of the Learjet while living in Switzerland in the late 1950s. He subsequently set up shop in Wichita, where he took big risks during the development of the Model 23, such as skipping construction of a production prototype on soft tooling. He fed his perpetually struggling company with investor money and earnings from the stereo eight-track tape player he had developed for automobiles. 

For some pilots, the airplane was too hot to handle. “The takeoff and landing speeds were like [those of] fighters,” said the late aerodynamicist James Raisbeck, who founded a company that develops Learjet modifications. “The stall speed was 120 knots and when it stalled [the airplane] would roll suddenly.” Several design changes tamed some of these tendencies in the follow-on Models 24 and 25, but 20-series Lears retain a deserved reputation for demanding much of their pilots. 

Lear sold his 60 percent share of Learjet in 1967 for $27 million to the Gates Rubber Company. Under Gates, Learjet would launch one of its most popular models, the 35, with production of 738 aircraft between 1973 and 1994. The 35 and the more ubiquitous and powerful 35A were basically model 25s with a slightly longer fuselage, bigger wings, and more powerful, fuel-efficient, and quieter Honeywell TFE731-2-2B engines (3,500 pounds of thrust, each). 

The aircraft requires a two-pilot crew and offers seating for up to eight passengers—although any more than six is decidedly uncomfortable. This is an airplane built for speed. The cabin measures a tight 12.9 feet long by 4.9 feet wide by 4.3 feet tall and volume is just 268 cu ft. The baggage “compartment” is something of an afterthought: a mere 40 cu ft of space you access by folding down the rear bench seat in the cabin. The good news is that you can access this in flight. The bad news is that, if those seats are occupied, someone has to move for you to do it. The aircraft’s available three-foot-wide cabin door and 9.4 psi cabin pressure differential, which allows the aircraft to maintain sea-level cabin altitude up to 25,700 feet, have made it a historical favorite with air ambulance providers. 

The 35A can fly at speeds up to 464 knots, has a brisk climb rate of 3,500 fpm, a maximum altitude of 45,000 feet, and a maximum range of 2,400 nm. Under standard temperature and altitude conditions, the aircraft can easily use runways shorter than 5,000 feet. But bring your gas card. The aircraft burns up to 200 gallons per hour at cruise power and has a fuel capacity of 931 U.S. gallons. By way of comparison, a similar aircraft of the era, a Cessna Citation V, burns 182 gallons an hour at cruise but is more than 30 knots slower. 

Numerous modification kits were fitted to the Learjet 35 series from both the factory and third-party providers that can increase gross weight, improve engine performance, range, and handling, reduce approach speeds and runway requirements, and add baggage capacity via wing lockers. Two key providers of these mods are Raisbeck and Avcon. About 30 percent of the in-service fleet has been modified with kits from one or both of these providers. Similarly, a variety of instrument panel modernizations are available. However, the aircraft’s low hull value makes it difficult to economically justify overinvesting in upgrades beyond those that are mandated by regulation such as ADS-B Out. You would be hard-pressed to find an aircraft retrofitted for Wi-Fi. 

More than 400 Learjet 35s are still in service. In the U.S., Michigan-based Royal Air Freight/Royal Air Charter operates one of the largest civil fleets while the U.S. Air Force still flies 18 for officer/executive transport with the designation C-21A. Used examples can be obtained for as little as $400,000, with updated aircraft in prime condition fetching near $1 million. 

My first introduction to the Learjet 35 came while employed with an aircraft seating company in the form of an engineering drawing with an accompanying photograph. The drawing was of a single, side-facing seat placed opposite the aircraft entry door. Lifting up the seat cushion revealed a commode seat atop a too-small stainless steel bowl that can be filled with blue-water disinfectant.

This, I was told, was the toilet. 

Thus, there is no lav in this airplane, per se. Rather a little “privacy” curtain in the front of the aircraft can be undone. If you are shy, this is not the airplane for you. And sometimes, there is no lav at all, according to John Yegerlehner, president of Spectra Jet in Springfield, Ohio, a company expert in the maintenance of the make and model. Yegerlehner has worked on 35s since 1988, beginning with the Air Force’s fleet, which once numbered into the 80s. 

“Ninety percent of our 35 customers disable the toilet,” said Yegerlehner. “They keep it dry so they don’t have to worry about corrosion or servicing it [after use]. The longest trips in the airplane are three to four hours and most people can hold it that long, or, if it’s a charter they will do shorter legs, land, and let people get out. It is such a pain to keep those things in working order.” 

Despite the restroom indignities, the 35 is an appealing aircraft for the right buyer, typically a Part 91 operator who flies 200 hours or less per year. Honeywell continues to support the engine, many of which are enrolled in its MSP Gold hourly service program. Yegerlehner said, despite the aircraft’s age and cabin limitations, values of some aircraft are increasing. “I had a customer who bought one five years ago for $450,000. He sold it last year for $750,000. Getting one in any condition is pretty much worth getting.”

However, like any other legacy aircraft, the 35/35A has some rather specific maintenance issues related to scarcity and the idiosyncrasies of its original manufacture. Yegerlehner notes that the aircraft was in a state of almost constant evolution during its production run and few aircraft are exactly alike. And big-ticket maintenance items including the thrust reversers, tip-tank boots, and landing gear can present some sourcing challenges as Bombardier no longer supports the aircraft save for engineering. 

The Aeronca engine thrust reversers need to be inspected every 1,400 hours and reassembled with new bushings and bearings. Any other defective components on the reversers discovered during the inspection need to be replaced and sometimes those can be hard to come by. The tip tank boots need to come off at the 12-year inspection and the rubber boots that are part of the connection from those tanks to the main wet wings need to be replaced as part of that process. Finding landing gear and replacement parts for it can also be a bit of an adventure, with major inspections on these components beginning at 6,000 landings. Yegerlehner’s firm has also discovered delaminated honeycomb floor boards during 12,000-hour inspections, when the wings and horizontal stabilizer must come off and be X-rayed. The floorboards needed replacement, an event he characterizes as “a pretty big deal.” A number of 35As currently on the market are coming up on the 12,000-hour mark and those inspections, along with the required replacement parts, can easily top $100,000. 

Parts support for classic Learjets, series 20-50, is provided by Global Parts in Augusta, Kansas. “They still have quite a bit of stock on a lot of things,” Yegerlehner said. Other parts can be obtained from various salvage yards in Kansas and Oklahoma, he said. 

Despite its age, Yegerlehner thinks the Learjet 35A is a good, reliable airplane. Royal Air still runs some of its 1970s vintage 35As up to six hours a day. “They have their normal failures like any other airplane, but on the whole, they are quite mission capable,” said Yegerlehner. 

But skip the coffee.