Learjet 24

The Learjet 24 is an American six-to-eight-seat (two crew and four to six passengers) twin-engine, high-speed business jet, which was manufactured by Learjet as the successor to the Learjet 23.
History.
The Learjet 24 was designed as an improved version of the Learjet 23, which was limited to gross weight. Engineers designed the model 24 to accept up to the full gross weight permitted by FAR-25 standards.
Other improvements introduced in the Learjet 24 included:
With these changes, the LJ24 became the first business jet to be certified under FAR-25.
The first flight of a Learjet 24 took place on January 24, 1966. From May 23 to 26, 1966, a Learjet 24 flew around the world in 50 hours and 20 minutes flying time as a demonstration of its capabilities.
Different variants were the 24A, B, C, D, E and F, with changes of takeoff weight, in-fuselage fuel tank, range, cabin and engines.
Altogether 259 Model 24s were built, and in 2001, there were still 210 Learjet 24s in use. Thirty-nine LJ24s have been lost through accidents.
Noise compliance.
In 2013, the FAA modified 14 CFR part 91 rules to prohibit the operation of jets weighing 75,000 pounds or less that are not stage 3 noise compliant after December 31, 2015. The Learjet 24 is listed explicitly in Federal Register 78 FR 39576. Any Learjet 24s that have not been modified by installing Stage 3 noise compliant engines or have not had "hushkits" installed for non-compliant engines will not be permitted to fly in the contiguous 48 states after December 31, 2015. "14 CFR §91.883 Special flight authorizations for jet airplanes weighing 75,000 pounds or less" – lists special flight authorizations that may be granted for operation after December 31, 2015.
Variants.
Learjet 24A.
Standard version. Converted from existing Learjet 23. Takeoff weight . FAA certified on November 9, 1966. 81 aircraft built.
Learjet 24B.
Improved variant, powered by two thrust General Electric CJ610-6 turbojet engines, and maximum take-off weight. FAA certified December 17, 1968. 49 aircraft built.
Learjet 24C.
A light-weight version of the 24B, fuselage tank not fitted which would have caused a reduction in range. The Learjet 24C project was abandoned in December 1970. Take-off weight . None built.
Learjet 24D.
Similar to Learjet 24C, however by changing surface tanks range and takeoff weight were increased to . Round cabin windows replaced by angular. FAA certified July 17, 1970. Replaced the 24B in production. A reduced gross weight (restricted to version was also available (the 24D/A). 99 built.
Learjet 24D/A.
Light-weight version with a restricted take-off weight of 5,669 kg (12,500 lb).
Learjet 24E and 24F.
Two new versions were announced in 1976 the 24E and 24F, they introduced a new cambered wing and aerodynamic improvements to reduce stall and approach speed (Century III wing). The 24E did not have a fuselage fuel tank for higher payload but shorter range. Some 24E models had the fuselage tank installed later to restore range. Powered by two thrust General Electric CJ610-8A turbojet engines. On April 15, 1977, the FAA approved extended ceiling to , the highest level then achieved in civilian aviation. 29 aircraft built.
Operators.
Mainly used by private individuals and corporations, one aircraft was used by NASA as the Lear Jet Observatory
Accidents and incidents.
On January 6, 1977, Dolly Sinatra the mother of Frank Sinatra was one of four killed when Learjet 24 "N12MK" crashed into a mountain following a departure from Palm Springs Airport, United States. 