Page 7 - Volume 20 Number 9

CJ
By LeRoy Cook
from Williams’ earlier experience with cruise-missile powerplants to become a powerful, yet parsimonious, business-jet engine. Williams International, in fact, was to receive the first production example of the CitationJet. Officially, the FJ44 was a Williams-Rolls, developed in partnership with Rolls-Royce.
Leveraging the Williams engine’s improved fuel specifics over the Pratt & Whitney JT-15D, Cessna went with a natural laminar-flow airfoil on an extended-span wing, 18 inches longer than the earlier Citation’s wing. A T-tail design replaced the old high-dihedral cruciform tail. Even with 6,000-pounds less total thrust than the 500, the CJ was to cruise 30 knots faster, range 10% farther and burn 19% less fuel, partly because it weighed 850 pounds less than its predecessor.
At the time of the first flight, the FJ44 engine had accumulated nearly 400 flight test hours, much it on the left pylon of a Citation 500 test-bed airplane. Most great advances in aircraft design result from employment of new propulsion technology; the Williams engines were to prove this theorem once again. Its 3.25:1 bypass ratio, using an efficient compressor system, cut fuel flow significantly while delivering adequate thrust for the lighter CJ. It also enabled cost savings to make the aircraft price competitive at $2,500,000 in 1988 dollars.
With careful manufacturing, the CJ’s natural laminar- flow wing could maintain its NLF back to the main spar, roughly 30% chord, using a chemical milling process in its skin and spar construction. By locating the fuselage tube atop the wing, a 57-inch cabin height could be achieved with a dropped aisle, and less drag resulted with the well-faired underslung wing. And with the lowered fuel tankage there was room in the wing for trailing-link maingear, forever banishing the “gotcha” touchdown of the stiff-legged Citation. Thrust attenuation paddles, much like those on Cessna’s T-37 trainer, were used to reduce the effect of residual thrust at idle, and an automatic deployment of the 35-degree landing flaps to 65 degrees after touchdown would reduce landing distance to 2,800 feet.
As with the Citation 500, the CitationJet was certificated under FAR Part 23, but was designed to the more-rigorous provisions of Part 25 transport airplane certification. At least, by the time the CJ arrived, single- pilot certification had become routine for Citations. The standard avionics package would be considered primitive 25 years later: the CJ featured Bendix/King panel-mounted equipment, including a KLN88 Loran C receiver, with a two-tube CRT EFIS.
Meanwhile, The Delays Continued
Many in the waiting assembly on first-flight day had airline connections to catch and had already surrendered their hotel rooms at the airport Marriot, having arrived the previous day in anticipation of a morning launch
While waiting on the weather to clear, first-flight attendees viewed the prototype in the hangar.
A Fresh Start
The CitationJet was breaking new ground, in an old, established way. The concept was to take the proven features of the Citation 500, first flown in September, 1969, and update it with the latest aerodynamic and propulsion technology. Attending the first- flight ceremonies was Dr. Sam Williams of Williams International, whose little FJ44 fanjet engine had evolved
SEPTEMBER 2016
TWIN & TURBINE • 5
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