Bill Lear Snr saw the cancelled Swiss FFA P-16 jet fighter as a basis for a twin-jet executive aircraft. He initiated preliminary design work at St Gallen, Switzerland, in November 1959 and sold his electronics company to the Siegler Corporation.
Using the basic design of the P 16’s wing, large tip fuel tanks and cruciform tail (hard tooling for which already existed), designed a compact fuselage that held two pilots and seven passengers. The engines were to be the civilian version of the military¬ proven General Electric J 85, which put out 2,850 pounds of thrust.
But the project soon bogged down, partly because of the Swiss Government’s rigidly structured bureaucracy and partly because Lear found himself constantly at odds with people who literally and figuratively didn’t speak his language. The final nail in the coffin may have been the Government’s attempt to tax the project before there was even sheet metal in the jigs. By early 1962, Lear was making arrangements to return to the U.S.
The SAAC designation was left behind, and the airplane became known simply as the Lear Jet Model 23.
While the competition featured cabins that were similiar in size to existing corporate aircraft, Lear produced a smaller, circular cross section that was both light and very strong.
When the number one airplane was still a few months from its first flight, Lear heard rumblings about the cruciform tail: some engineers doubted that the elevator, with its fixed horizontal stabilizer, would be able to hold up the nose in forward CG. Lear put the project behind schedule in order to install a T tail.
The prototype Lear Jet Model 23 (N801L) flew on 7 October 1963. Lear had hoped to save time by obtaining the type certificate under FAR Part 23 (the rules for aircraft under 12,500 pounds gross weight) rather than the more stringent Part 25, which governs transport category aircraft. But the Wichita FAA, then not very familiar with jets, tacked on some additional requirements that threatened to slow down certification. In reality, the airplane met or exceeded the most important of Part 25 criteria; the main exception was the bird proof windshield, later added as part of the changeover to the Model 24.
One of the FAAs additions required that Lear establish balanced field lengths; and it was here that disaster struck. Testing for single engine climb performance, with an FAA test pilot in the left seat and Lear’s pilot in the right, N801 Lima left the ground with one engine actually shut down (normally not done until the very end of the testing phase) and the spoilers inadvertently extended. In this configuration, it was something of a miracle that the airplane flew at all; as it was, even with the gear retracted, it refused to climb much beyond ground effect, and it just managed to clear some trees at the end of the field.
In the cockpit, meanwhile, confusion reigned: an engine restart was unsuccessful because of improper procedure, and neither pilot thought to check spoiler position. Soon the airplane began to settle slowly and, with a field just ahead, the pilots elected to put the gear down and ride it in. The loss of this prototype should have been a crippling blow.
The second and third prototype aircraft being first flown on 5 March and 15 May 1964 respectively. On July 31, 1964, less than two months after the accident and nine and a half months from the Lear Jet’s first flight, FAA Administrator Najeeb Halaby personally flew to Wichita to present the type certificate to Lear. The provisional airworthiness certificate took the plane out of the experimental class and authorised flights anywhere in the US for demonstration and service testing. Bill Lear promptly flew his jet to New York in 2 hr 21 min. The planned price of the Lear 23 was $575,000.
The first production Lear Jet was rolled out 20 months after ground was broken for the factory. Built in 135 days, it was delivered to the Rexall Drug & Chemical Corp of Cincinnati, Ohio, on 13 October 1964.
A new wing, incorporating milled skins to replace the use of built up material, was added at the 20th plane on the Lear Jet production line at Wichita.
Lear increased production to 10 airplanes per month. While the plant was being expanded, he began work on re-certifying the airplane under Part 25 (this later became the Model 24), developing a stretched version (the Model 25).
In 1965 a Lear 23 established a Los Angeles to New York and return record of 10 hrs 52 min flying time, and a time-to-climb record to 40,000 ft – 7 min 21 sec – with seven people on board.
Distinguishing a Model 23 from a 24, however, is tougher, mainly because most of the changes were internal (improvements in the various systems) and on paper (weight and performance numbers). The two most obvious external differences 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 vortex 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.)
Intended for single-pilot operation the basic layout was for a crew of two and for five to seven passengers.
There were 104 Model 23s built, although the serial numbers only run from 001 through 099. The difference is five A models, the existence of which stems from the backlog of orders just after the airplane received its type certificate. Lear, during the course of a normal day’s wheeling and dealing, would promise yet another airplane to a special customer. To keep this person from having to wait a year for delivery, Lear would sneak him in at the head of the line by creating an A model and bumping all the numbers back one.
In those days, there was no such thing as a standard Learjet. True, the basic airframe/engine combination had been frozen by the type certificate, but the systems and, in particular, the instrument panel were considered fair game for new ideas. The first 30 production aircraft to be completed were powered by 1293kg thrust General Electric CJ610-1 turbojets, but the remainder of the production run of a little over 100 Lear Jet 23s had CJ610-4s of similar thrust. To Lear, all Learjets, even those brought in for routine maintenance, were prototypes. As a result, pilots about to fly an airplane only a few serial numbers away from their usual one still had to take time to locate switches in the cockpit. The first 14 air¬planes provide the most extreme example of this. They all had left hand control panels, so confident was Lear that single pilot certification was just around the corner.
012 set three official world records during a round robin flight between Los Angeles and New York, making the trip in 10 hours and 21 minutes, with two refueling stops.
055 set a time to climb record. With seven people on board, it went to 40,000 feet in seven minutes and 21 seconds, a record that later fell to a Model 25.
Several Model 23s have passed the 10,000 hour mark.
Engine: 2 x GE CJ610-1.
MTOW: 12,500 lb.
Engine: 2 x General Electric CJ610-4 turbojets, 1293kg
Max take-off weight: 5670 kg / 12500 lb
Empty weight: 2790 kg / 6151 lb
Wingspan: 10.85 m / 35 ft 7 in
Length: 13.18 m / 43 ft 3 in
Height: 3.84 m / 12 ft 7 in
Wing area: 21.46 sq.m / 230.99 sq ft
Max. speed: 903 km/h / 561 mph
Cruise speed: 781 km/h / 485 mph
Ceiling: 13715 m / 45000 ft
Range: 2945 km / 1830 miles
ROC: 6,900 fpm.
All Aero 