Learjet 31

The Learjet Model 31 is, arguably, the ultimate realization of the original Learjet series dating back to the Model 23 of 1963. Essentially combining the fuselage and engines of the model 35/36 with the “Longhorn” wing of the 28, 29 and 55 models, results in performance which is equaled by few aircraft. Normal cruise altitudes range from 41,000 to 47,000 feet (12,500-14,900 m) and the aircraft's maximum cruise altitude of 51,000 feet (15,500 m) is a distinction shared by only a handful of civil aircraft. Improvements over earlier models, such as “Delta-Fins” and a “Ski-Locker” increased the utility and improved the performance of the model 31. The addition of Delta-Fins at the bottom of the empennage simplified the certification process of the aircraft by eliminating the need for a “stick pusher” stall avoidance device. Increased directional stability, as a result of the Delta-Fins, was also a welcome benefit. However, a small cabin with little baggage space and no galley, and relatively short range because the Learjet 35/36's tip tanks were eliminated in favor of the winglet-equipped Longhorn airfoil, led to only 38 Learjet 31s being built.[3]

A Learjet 31A jet belonging to the Government of Balochistan, Pakistan

The Learjet 31A was announced in 1990 as a replacement. The model 31A boasted numerous modifications, however the most notable changes would take place on the flight deck. Key modifications and updates to the model 31A cockpit and avionics include; a Bendix King (now Honeywell after the merger with Allied Signal) Electronic Flight Information System 50, with Universal 1M, 1B and 1C flight management system, a dual KFC 3100 two-axis autopilot and flight director with yaw damper, and dual Bendix King (Radios sold to Chelton Avionics when Allied Signal combined with Honeywell) VCS-40A com units, VN-411B Series III navigation receivers.

In the year 2000 the Learjet 31A was again revised. Takeoff and landing weights were increased.[4] The original design N₂ digital electronic engine control (DEEC) was replaced with an N₁ DEEC,[4][5] and the thrust reversers became standard equipment. Another notable improvement is Honeywell's TFE731-2 to -2C engine upgrade.[3] The original R12 freon air conditioning system was replaced with an R134A system divided into two zones - cockpit and cabin.[5]

The extended range version of the Learjet 31A, has a range of 1911 nm (2199 miles or 3539 km). Overall the numerous enhancements have led to more than 200 Learjet 31s in service with private operators and governments worldwide.[3]