Gates Lear 28 Longhorn
In January 1979 the company gained certification of the Learjet 28 and Learjet 29 Longhorn. Basically similar to the 10-seat Learjet 25D, these two models introduced a new wing of increased span.
Learjet’s Longhorn series combines a revolutionary wing design, two of the most advanced engines introduced to the market, and 51,000-foot performance. The line of five aircraft has been designated the Learjet 28 and Learjet 29, both powered by General Electric turbojets, and the Learjet 54/55/56, and those three are powered by twin Garrett AiResearch fanjets. All the models are designed with a larger wing incorporating near-vertical winglets that have replaced the traditional Learjet tiptanks. The wing’s increased aspect ratio and super-critical winglets provide substantial aerodynamic improvements that in turn produce greater fuel efficiency and improved flight performance at high and low altitudes. The wing also has been responsible for significantly improved short-field performance. The balanced field length for the 28/29 series is only 2,520 feet and 3,520 feet for the 54/55/56 series. In addition, the 28/29 is able to climb from takeoff directly to 51,000 feet.
The Learjet 28 had 10-seat accommodation, but the longer-range Learjet 29 traded two passengers for an additional 379 litres of fuel. However, wing manufacturing costs were considered prohibitive against the performance improvements gained and further development of both the Learjet 28 (five built) and 29 (two built) were terminated in August 1982. Around the same time, when sales of the Model 25 had reached 368, production was phased out in favour of the Learjet 35 and 36.
LR-28 Learjet Longhorn 28
Engines: 2 x General Electric CJ610-8A, 2950 lbs thrust.
Length: 47.6 ft. / 14.52 m
Height: 12.3 ft. / 3.73 m
Wingspan: 43.8 ft. / 13.34 m
Wing area: 265 sq.ft. / 24.6 sq.m
Wing aspect ratio: 7.2.
Maximum ramp weight: 15,500 lbs.
Maximum takeoff weight: 15,000 lbs.
Standard empty weight: 8968 lbs.
Maximum useful load: 6532 lbs.
Zero-fuel weight: 11,000 lbs.
Maximum landing weight: 14,300 lbs.
Wing loading: 56.7 lbs/sq.ft. / 277.0 kg/sq.m
Power loading: 2.5 lbs/lb.
Maximum usable fuel: 4684 lbs.
Best rate of climb: 6925 fpm.
Certificated ceiling: 51,000 ft.
Max pressurisation differential: 9.4 psi.
8000 ft cabin alt @: 51,000 ft.
Maximum single-engine rate of climb: 2125 fpm @ 220 kts.
Single-engine climb gradient: 580 ft/nm.
Single-engine ceiling: 29,000 ft.
Maximum speed: 477 kts.
Normal cruise @ 47,000ft: 448 kts.
Fuel flow @ normal cruise: 1047 pph.
Stalling speed gear/flaps down: 90 kts.
Balanced field length 2,520ft