As the very last Learjet produced to draw on the Learjet 24’s legacy, the Learjet 31 holds a special place in the hearts of enthusiasts and owners alike. Fast, sleek, and ever-reliable, it has built a deserved reputation as a sleek jet that flies as good as it looks.
1990 / Learjet 31 / Model Specs
The Learjet 31 is the last aircraft to lean onto the Learjet 24’s type certificate from 1996. The aircraft requires a crew of two and can seat up to eight passengers. Its empty weight is set at 9857 lbs, with a maximum take-off weight of 15500 lbs for the standard model and 17700 lbs for the Learjet 31A. The aircraft is powered by two Garrett TFE731-2 engines, later upgraded to the more powerful TFE731-2C.
It incorporates tried and tested components from older Learjet aircraft, mating the Longhorn wing debuted in 1979 by the Learjet 55 to the classic Learjet 35A fuselage. Many of its systems were also inherited, such as the parallel bus, a DC electrical system with bus-tie breakers, a bleed air system operated by on/off switches in the cockpit, an analog pressurization system, and an entry door which is manually opened but retracted with a motor. The gear is fitted with outstanding anti-skid brakes, which allow for great landing performance even in contaminated runway conditions. Check out the different types of Learjet Plane Types and Models in our complete guide here!
Learjet 31 / Model Prices
Between 1990 and 2003, the Learjet 31 was sold for $4.1 million.
Learjet 31 / Performance and Handling
The Model 31’s hot rod reputation has been rightfully earned. As a result of mating the small Learjet 35 fuselage to the Learjet 55’s aerodynamically-refined longhorn wing, the Learjet 31 turned out to be a light and clean design, powered by a pair of powerful Garrett TFE731-2 turbofans producing 3500 lbf each. This combination made its performance unmatched in the business jet category, a feat even more impressive when factoring in that the Learjet 31 achieves this while also having better fuel efficiency than the competition.
Maximum speed is set at Mach 0.81, with a cruise speed of 448 knots. The aircraft’s stall speed with flaps and gear deployed is 84 knots, rather low for a jet of its size. Its high cruise altitudes between FL430 and FL470 make the weather a non-issue for the most part, as the Model 31 allows pilots to happily cruise above clouds and turbulence.
As is the case with other Learjet 23 descendants, the Learjet 31 can comfortably cruise at a whopping 51000 ft, which is why you will often see Learjet pilots proudly wearing pins that say “510” on their lapels. Climb speeds are set at 5480 ft/min, a number unmatched in its category.
The Longhorn wing and the tailcone’s anhedral delta fins gave the Learjet 31 very docile and predictable low-speed handling. Testament to the aircraft’s quality is that it flies slow as well as the Citation 500 series while also enjoying much higher top and cruise speeds.
The aerodynamic refinements removed certain low-speed vices that owners of previous Learjet models brought up. The improvements were such that the Learjet 31 finally could get rid of the stall barrier stick pusher, and the yaw damper was removed from the minimum necessary equipment list. Thanks to its sound wing design, low weight, and powerful engines, the aircraft’s take-off, and landing runs are considerably short for a jet, achieving good performance even in contaminated runways without serious difficulties.
Learjet 31 / Model Maintenance Schedule
The Learjet 31’s maintenance and inspection schedule mandate A-checks at 300 hours, B-checks at 600 hours, C-checks at 1200 hours, and D-checks every 2400 hours, or 12, 24, 48, and 96 months respectively, whichever is reached first. A wing and horizontal demating are required at the 12000-hour mark. Every 12 years, the Model 31 must undergo fuselage X-ray checks as well. The demating and X-ray inspections are the most costly maintenance items for Learjet 31 owners, costing between $150000 and $200000 each, depending on the airframe’s specific conditions.
The TFE731 engines must undergo a major periodic inspection every 1400 hours, plus a core zone inspection and overhaul after 4200 hours. The most popular coverage option is the Honeywell MSP Gold, which costs around $660 per hour of flight for both engines combined. Circumstantially, certain operators with worn-out engines have preferred to buy used TFE731-2 units to replace theirs instead, with a cost of $120 per flight hour.
On average, Time Aerospace in Colorado Springs recommends budgeting $250 per flight hour spent in maintenance, with an additional $50 for each landing to account for wear on the brakes and tires.
Learjet 31 / Modifications and Upgrades
The original version, dubbed Model 31, is the last Learjet design that traces back to Bill Lear’s original Model 23 from 1963. The core of the aircraft came about as a combination of preexisting fuselage and wing designs used on other Learjet models. Its 51000ft maximum cruise altitude is unrivaled by the vast majority of civilian aircraft.
After mating components from its predecessors, the Learjet 31 added delta fins to the bottom of the fuselage for improved yaw stability and a so-called ski-locker, which made it perfect for storing gear on skiing or golf trips.
Compared to larger jets entering the market, however, the Learjet 31 was deemed lacking in comfort facilities – highlights of this were its small baggage space, no galley, and rather primitive toilet facilities. These were somewhat offset by what in earnest was a shortcoming of the Model 31, its greatly diminished range compared to the Model 35 due to the deletion of the wingtip tanks in favor of the Longhorn winglets.
The lacking galley and washroom situation do not make themselves as noticeable when the aircraft is unable to fly transatlantic or one-stop transamerican routes. These tradeoffs had a noticeable impact on Model 31’s sales, with only 38 being delivered to users before the production line began building the Learjet 31A instead.
Introduced in 1990, the Learjet 31A fully replaced the base model as the line’s chief offering in the category. The Model 31A’s main innovations were centered around avionics. The flight deck was outfitted with the Bendix King Electronic Flight Information 50, plus the Universal 1M, 1B, and 1C flight management system, a redundant KFC 3100 pitch and roll autopilot, and a flight director coupled with the yaw damper. Communication radios were Bendix King VCS-40A models, while navigation transceivers were of the VN-411B line. The Model 31A also boasts a boosted rudder system, increasing the aircraft’s maximum crosswind limits.
Ten years after its introduction, the Learjet 31A has revised again but did not have its designation changed. Newly-built aircraft had their N2 digital electronic engine control (DEEC) unit replaced for an N1 DEEC, while thrust reversers were introduced as standard equipment instead of add-ons. This further improved the aircraft’s already noteworthy runway capabilities.
The TFE731-2 engines were replaced by the TFE731-2C, boasting higher thrust, better fuel efficiency, and revised maintenance protocols. Learjet 31 units built before this can have the new engines fitted during major work as aftermarket add-ons. Another minor change concerns the air conditioning system, with the original global R12 being replaced by the R134A unit, divided into cabin and cockpit sections which allowed for pilots and passengers to pick settings comfortable to them instead of one party having to compromise.
The last Learjet 31 derivative designed was the Learjet 31A/ER, a further revision of the aircraft aimed at overcoming the range issues that had harmed sales until then. The installation of expanded fuel tanks brought the Model 31A/ER’s range to 1911 nautical miles, a number matching the excellent performance boosted by the Learjet 35 line. In total, over 200 Learjet 31 units were built and delivered until production shifted to the first clean sheet design by Bombardier, the Learjet 45 family.
There are many aftermarket modifications available for the Learjet 31. Aviation firm Raisbeck offers the ZR Lite aerodynamic-enhancement kit, aimed at reducing the Model 31’s transonic drag. Weighing only 32 lbs, this modification can increase the range by at least 100 nmi. Further range enhancements can be achieved with an optional fuel tank increase, bringing capacity up by another 500 lbs and effecting a range boost of 200 nmi.
A single-point pressure refueling (SPPR) port can be installed so that wing and fuselage tanks are filled simultaneously. In the default aircraft, pilots must use the DC-powered boost pumps to transfer fuel from the fuselage onto the wing tanks. Another benefit of the SPPR option is that it adds standard fuel heaters, removing the need for anti-icing additives in the fuel.
For additional passenger comfort and easier loading and unloading of large items and luggage, owners can opt for a 36-inch wide entry door. Raisbeck also offers an external luggage compartment, allowing passengers to only bring what they actually want and need aboard into the cabin instead of cramming the area with suitcases.
Learjet 31 / Where to Find Replacement Parts
Procuring spare parts for the Learjet 31 has its ups and downs. As a business jet manufactured by Bombardier, its owners have access to the Canadian aerospace giant’s customer support network, which introduced a parts stock network to help locate, purchase and deliver components to owners from shops anywhere in the world.
Due to the aircraft’s relatively modest production run, which ended many years ago, certain components have become increasingly hard to find in suitable conditions. Learjet 31 owners usually recommend tracking down some of the shops which have a large stock of Learjet parts and using them to secure items ahead of time.
Learjet 31 / Model Common Problems
The main complaint about the Learjet 31 line is its range. While the Longhorn wing brought aerodynamic improvements, which helped reduce fuel consumption, they came at the cost of removing the signature wingtip tanks inherited from Switzerland’s canceled FFA P-16 fighter-bomber. While the Learjet 35A had an NBAA range of 1924 nmi, this was cut rather drastically to 1290 nmi with the Learjet 31. Operators report that the Learjet 31 is the perfect 1000-mile jet, being able to comfortably meet such ranges without compromising on passengers, baggage, or fuel reserves.
Operators have noticed certain items can fall short of their advertised maintenance periods. The starter generators usually need to be worked on at 1000 hours as opposed to the published 1400-hour interval scheduled in the manual. Certain hydraulic components, in particular the flap, spoiler, and landing gear actuators, are known to be rather prone to leaking, which can put the crew in rather uncomfortable positions if aggravated. As the aircraft ages, owners have reported that the vapor cycle compressor lines can deteriorate, leading to air leaks, and the electric de-icing points on the horizontal stabilizer occasionally fail.
Learjet 31 / Insurance Options
According to business aviation company Guardian Jet, a Learjet 31 with a moderately experienced crew can get hull and liability insurance for around $26000 annually.
Learjet 31 / Model Resale Value
The average price range for the Learjet 31 family in the used market is between $650000 and $800000. The model is known for having a good turnaround in the market, with usually around 3 trading hands each year.
Major factors in determining a Learjet 31’s resale value include the aircraft’s version, modifications, maintenance status, remaining engine life, and overall condition. Great attention is paid to the engine’s program, with units enrolled in Honeywell’s MSP commanding much higher fees than an equivalent jet without it.
Learjet 31 / Owner Reviews
The Learjet 31 family has been a hit among owners. Owners love its excellent climb and speed performance, matched with low fuel consumption and rather modest maintenance costs for the most part. Another operator favorite is the aircraft’s reliability, meaning a Model 31 owned is a Model 31 flown regularly and with little downtime.
The hot rod spirit of the Learjet 31 is also a favorite among pilots. Its designers managed to marry good fast climb and cruise performance with very docile handling at low speeds, a feat previously unachievable with previous Learjet models, which were notorious for their temperamental nature when slow.
The good handling characteristics of the Learjet 31 were proven in an unusual fashion in 2018. Pilots flying a Model 31A from England to Portugal successfully performed an aileron roll, with a maximum load of 2.9G. The stunt caused no damage to the aircraft whatsoever and was only noticed during a standard company review of flight recorder data which accused extreme bank angles in that flight. Aerobatics are forbidden in the Learjet 31, but the aircraft’s ability to successfully perform such a maneuver without any consequences is a testament to its good handling and ruggedness.
The spare parts situation has caused problems to owners who do not have the inclination to search around, and it has been aggravated by the reduced useful life of certain components in practice. The range has been a common complaint about those who often need to make far trips, though this has been fully rectified with the Learjet 31A/ER.
Learjet 31 / Similar Aircraft
The Learjet 31 faces stiff competition in its niche. Cessna’s Citation line offers the Citation II and S/II. Compared to the Learjet, they fall significantly behind in terms of speed, climb, and service ceiling, though this is compensated in passenger comfort by having a noticeably larger cabin and factory-installed external baggage compartments. In the particular case of the Citation S/II, it exceeds Learjet 31’s standard range as well. Beechcraft’s Hawker 400 almost bridges the performance gap, matches the Model 31’s range, and significantly exceeds it in cabin comforts.
The Learjet 31 is only properly beaten across the board by the Cessna Citation V: it has excellent landing and take-off performance, a considerably longer cabin, matching cruise speeds, and a better range. These advantages do not come for free, however, with the Citation V being considerably more expensive than the Learjet 31.
Learjet 31 / Clubs You can Join
There are no major Learjet 31 type clubs due to the fleet’s ownership being mostly composed of executive aviation companies. However, there are many Learjet 31 pilots and owners active in forums and groups on social media websites who are able to share their expertise with current and prospective owners of this unique aircraft.
FAQ: Frequently Asked Questions
Question: How much is a Learjet 31?
Answer: A new Learjet 31 used to cost $4.1 million. However, second-hand units now sell for around $800000.
Question: How far can a Learjet 31A fly?
Answer: The Learjet 31A has a range of 1290 nautical miles, but this can be expanded by up to 300 miles via a combination of fuel capability expansions and aerodynamic refinement kits.
Question: Are Learjets still made?
Answer: No. The Learjet 31’s serial production ran from 1990 to 2003 before being replaced by the Learjet 45, built until 2012. The last Learjet to be produced was the Model 75, with its production completed in 2021.
Question: How high can a Learjet fly?
Answer: The Learjet 31 family shares the maximum ceiling for the line, being able to cruise at 51000 ft.
Question: Does a Learjet have a toilet?
Answer: Yes. The Model 31 has rudimentary toilet facilities located at the front of the aircraft, with privacy curtains fitted front and aft of it.
Research Citations
https://www.aopa.org/news-and-media/all-news/2014/july/pilot/t_ql
https://www.avbuyer.com/articles/jets-comparison/cessna-citation-cj4-vs-learjet-31a-er-55703
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