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Gates Lear 24


lear24

 

The 5670kg gross weight limit to which the Lear Jet 23 had been developed proved in practice to be an unnecessary constraint. Most operators were already using two-man crews and, subsequently, CAB licensing requirements for low-capacity jet aircraft were eased. This allowed Lear to take advantage of the basic strength of the design to develop a new version, to FAR.25 standards, with a gross weight of 6123kg. Announced in October 1965, the Learjet 24 introduced among other improvements increased cabin pressurisation for operation at higher altitude.


Distinguishing a Model 23 from a 24, however, is tougher, mainly because most of the changes were internal (im-provements in the various systems) and on paper (weight and performance num-bers). The two most obvious external dif-ferences are the vortex generators-small metal tabs that project above the wing ahead of the ailerons and the windshield. A Model 23 has a set of vor-tex generators on the underside of the wing as well as the upper surface; 24s have them only on the upper surface. The Model 24's windshield, befitting a transport-category airplane, is a bird -proof design with a T-shaped stiffener on the vertical post separating the two halves; if this stiffener is missing, you are looking at a Model 23. The factory's records, in 1978, indicated that 12 of the 88 Model 23s still flying were Model 24s in every respect except serial number.)


The first Learjet 24 was flown on 24 February 1966 and gained certification the following month. In 1967 Bill Lear's holdings in Lear Jet Corporation were acquired by the Gates Rubber Company. As a result, in January 1970 the Lear Jet Corporation was renamed the Gates Learjet Corporation. A year earlier the company had started delivery of a new Learjet 24B, differing primarily by having uprated 1338kg thrust General Electric CJ610-6 engines giving an additional 100 lb thrust over the -4. The Lear 24B was certified in 1969.

lear24b
Lear 24B


A lighter-weight Learjet 24C was then under development, but this was abandoned in December 1970 in favour of the Learjet 24D. This offered greater range as a result of increased fuel capacity and certification for operation at a higher gross weight. It was recognisable externally by deletion of the non-structural bullet at the junction of the horizontal and vertical tail surfaces and by having square instead of oval cabin windows. A Model 24D/A was also available with take-off weight restricted to 5669kg.


In 1976 these two versions were superseded by the Learjet 24E and Learjet 24F, introducing a new cambered wing and aerodynamic improvements to reduce stall and approach speeds. Although the two models were generally similar, the Learjet 24F differed by having almost 18 per cent greater fuel capacity. Production of the Learjet 24E was terminated during 1979, and that of the Learjet 24F during 1980, 258 model 24s having been built.


The improved model 24 with airline transport category certification was introduced, and in 1968, a stretched 10-seat model 25 was offered. This aircraft has the most exceptional climb rate in its class. The All Learjets are approved for operation at 45,000 feet, and they have much better short-field performance than is common in this category of aircraft. One reason for the climb and takeoff advantage is weight: The model 23, which needs only 2,300 feet to clear a 50-foot obstacle at gross-weight takeoff, weighs only 6,500 pounds empty and grosses at 12,500 pounds. It can fly at 26,000 feet with one engine inoperable.


Gates certified its Century III 24/25 Learjets to cruise at 51,000 feet, higher by 5,900 feet than the max for any other FAA-certified commercial aircraft. Since pressurization failure at that altitude could be fatal no matter how enthusiastic one's emergency descent were, the FAA's certifi-cation tests were the same ones they'd planned to give the abortive Boeing SST- including firing pistols point-blank at the cabin windows.

LR-24
Engine: GE CJ601-4.
MTOW: 13000 lb.
Max cruise alt: 45,000ft.

LR-24B
Engines: 2 x GE CJ610-6.
MTOW: 13,500 lb.

Lear 24E
Engines: 2 x General Electric CJ610-6, 2950 lb.
Seats: 8.
Wing loading: 55.6 lb/sq.ft.
Pwr loading: 2.19 lb/lb.
Max TO wt: 12,900 lb.
Operating wt: 7440 lb.
Equipped useful load: 5420 lb.
Payload max fuel: 692 lb.
Zero fuel wt: 11,400 lb.
Range max fuel/cruise: 1171 nm/2.5 hr.
Range max fuel / range: 1442 nm/ 3.5 hr.
Service ceiling: 45,000 ft.
Max cruise: 464 kt.
Max range cruise: 418 kt.
Vmc: 103 kt.
Stall: 88-116 kt.
1.3 Vso: 114 kt.
ROC: 7220 fpm.
SE ROC: 2225 fpm @ 220 kt.
SE Service ceiling: 28,500 ft.
BFL: 3000 ft.
Cabin press: 8.9 psi.
Fuel cap: 4791 lb.

LR-24D-XR

Range: 2000 nm.
Cert alt: 50,000ft.
Cruise: M0.82.
Seats: 8.

Lear 24F
Engines: 2 x GE CJ610-6, 2950 lb.
Seats: 8.
Length: 43 ft 3 in.
Wing loading: 58.3 lb/sq.ft.
Pwr loading: 2.29 lb/lb.
Max TO wt: 13,500 lb.
Operating wt: 7545 lb.
Equipped useful load: 5955 lb.
Payload max fuel: 327 lb.
Zero fuel wt: 11,400 lb.
Range max fuel/cruise: 1403 nm/3 hr.
Range max fuel / range: 1651 nm/ 4 hr.
Service ceiling: 45,000 ft.
Max cruise: 464 kt.
Max range cruise: 418 kt.
Vmc: 103 kt.
Stall: 88-118 kt.
1.3 Vso: 114 kt.
ROC: 7100 fpm.
SE ROC: 2050 fpm @ 220 kt.
SE Service ceiling: 27,000 ft.
BFL: 3297 ft.
Cabin press: 8.9 psi.
Fuel cap: 5628 lb.

Learjet 24F
Engines: 2 x General Electric CJ610-8A turbojets, 1338kg
Wingspan: 10.85 m / 35 ft 7 in
Length: 13.18 m / 43 ft 3 in
Height: 3.73 m / 12 ft 3 in
Wing area: 21.53 sq.m / 231.75 sq ft
Max take-off weight: 6123 kg / 13499 lb
Empty weight: 3204 kg / 7064 lb
Max. speed: 880 km/h / 547 mph
Cruise speed: 793 km/h / 493 mph
Ceiling: 15545 m / 51000 ft
Range: 2731 km / 1697 miles

 

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