Cessna Citation X

The Cessna Citation X is a medium-sized business jet airplane designed to fly at high subsonic speeds. It is the fastest business jet available, and the third fastest civil airplane that has ever flown, after the Concorde and Tupolev Tu-144.

Contents

1 Overview

2 Airframe

3 Engines

4 Powered Controls

5 Avionics

6 Key performance figures

7 Timeline

Overview

The Citation X is operated by two crew and carries from eight to twelve passengers. Some major characteristics are summarized below.

Wingspan - 63.6 ft (19.4 m)
Length - 72.3 ft (22.0 m)
Height - 19.0 ft (5.8 m)
Aspect Ratio - 7.8
Wing Area - 527 ft² (50 m²)
Tailplane Span - 26 ft (7.9 m)
Dihedral - 2°
Wing Sweep - 37°

The aircraft incorporates a number of innovative design features. One attribute that is often first noticed is the large diameter of the engine intakes. This feature, related to the high bypass ratio turbofan, reduces the noise from the engines and improves fuel efficiency. Another obvious characteristic is the highly swept wing, in order to increase the critical Mach number and therefore the top speed. The Citation X has 37 degrees of sweepback at the quarter chord, more than any other business jet and, among civil aircraft, second only to the Boeing 747's 37.5 degrees. The horizontal and vertical stabilizers are also highly swept and are arranged in a T-tail configuration.

Airframe

A significant amount of effort throughout the design process was directed towards reducing the Citation X's total drag. The resulting design includes an area-ruled fuselage for efficient transonic flight, and the aforementioned highly swept supercritical wing. Unlike those on previous Citation aircraft, the Citation X's wing is slung below the fuselage rather than passing through it. This allows increased volume in the fuselage, a one-piece wing, and simplified wing-fuselage connections.

Engines

The Citation X is powered by two Rolls-Royce/Allison AE3007C1 turbofan engines, each with a thrust of 6700 lbf (30 kN), pod-mounted on the sides of the rear fuselage. It is the first Cessna aircraft to be powered by a Rolls-Royce engine. The engine has solid titanium blades and a three-stage low-pressure turbine. The engine's fan has a 5 to 1 bypass ratio for improved fuel efficiency and low acoustic signature.

Powered Controls

Another first for Cessna is the inclusion of powered controls in the Citation X. The controls are powered by dual-hydraulic systems for redundancy. There are two elevators and the tailplane is all-moving for trim. The rudder is in two pieces: the lower portion is hydraulically-powered and the upper portion is electrically-powered. Each wing has five spoiler panels, to be used both for roll control (in addition to the ailerons) and as speed brakes. One of the major challenges of the Citation X design was finding enough space in the wing to run all the necessary hydraulic lines. As Paul Kalberer, the chief engineer of the Citation X program, explained, the Citation X needs just as many hydraulic pumps and actuators as a Boeing aircraft, but has much less space inside the wings.

Avionics

Honeywell provides the avionics system. The Honeywell Primus 2000 flight director system is composed of five 7"x8" LCD screens. Dual flight management systems with GPS are standard.

Key performance figures

Cessna advertises the Citation X as the fastest business aircraft available. It has a top speed of Mach 0.92, which at its normal flight altitude of 43000 feet (13 km) is about 510 knots (945 km/h). Since the retirement of the Concorde, no civil aircraft flies at a higher Mach number. The Citation X has a range of about 3300 nautical miles (6,100 km), although this requires less than full payload (only one or two passengers) and a cruise Mach number of 0.82. It can easily travel between any two points in the continental United States, such as New York to Los Angeles, a distance of 2139 nautical miles (3,961 km). The Citation X can only perform a limited number of transatlantic routes, such as New York - Paris, a distance of 3159 nautical miles(5850 km), and is incapable of transpacific flights. The range decreases as the Mach number increases beyond 0.82, meaning customers are forced to choose between speed and range. The Citation X takes off in 5140 feet (1567 m) and lands in 3400 feet (1036 m). It has good fuel consumption, burning the same amount of fuel at Mach 0.9 that its competitors burn at Mach 0.8, due to its efficient engines and low-drag configuration. Another key accomplishment is the 70 knot (130 km/h) buffet margin (that is, the difference in speed between the stall buffet and the high-speed buffet). Many transonic airplanes at high altitudes have the stall buffet speed only 5 knots (9 km/h) below the high-speed buffet. The Citation X's wide margin allows for steep turns at high altitudes, which can be useful in emergency maneuvering. The wide margin also means that the speed does not have to be maintained at a precise value for safe operation of the airplane.

Weight empty (typically equipped) - 21,600 lb (9,800 kg)
Max fuel weight - 12,931 lb
Max T-O weight - 36,100 lb
Max ramp weight - 36,400 lb
Max landing weight - 31,800 lb
Max zero-fuel weight - 24,400 lb
Max wing loading - 68.50 lb/ft²
Max power loading - 2.67 lb/lb st
Max operating Mach No. (MMO) - 0.92
S/L to FL080 - 270 kt
FL080 to FL306 - 350 kt
Max cruising Mach Number, mid-cruise weight at FL370 - 0.91
Max cruising speed at FL350 - 525 kt
Max rate of climb at S/L - 3,650 ft/min
Max certified altitude - 51,000 ft
T-O balanced field length (FAR Pt 25) - 5,140 ft
FAR Part 25 landing field length - 3,400 ft
IFR range with two crew, M0.82 - 3,216 n miles

Timeline

The development of the Citation X was first announced at the National Business Aviation Association Convention in New Orleans in October 1990.

Originally scheduled for August 1995, the certification of the Cessna Citation X was delayed several times. First, failure of the airframe and engine to meet Federal Aviation Administration requirements caused the planned certification date to be postponed to late November 1995. The main reasons for the delays were troubles integrating the avionics and the engine to the aircraft, engines flaming out at high altitude and low speed (airflow was insufficient at high angles of attack because of the interference of the wing), the engines not meeting the bird strike criteria and directional stability challenges. Efforts to increase the maximum take-off weight of the Citation X by about 800 pounds led to another delay in the FAA certification schedule, this time to April 1996. These changes were aimed at permitting a full-fuel payload of 1,400 pounds (seven passengers) but Cessna had difficulty achieving a balance between reducing Citation X cabin noise and minimizing the extra weight of sound-dampening materials. The certification, FAA FAR Part 25, Amendment 74, Certification 3, was finally achieved on June 3, 1996.

The first Citation X was delivered in June 1996 to golfer and long-time Cessna customer Arnold Palmer. Once in use, the Citation X continued to set speed records. Arnold Palmer set one of them in September of 1997: 473 knots on a 5000 km closed course. In February 1997, the Citation X design team was awarded the National Aeronautic Association's Robert J. Collier Trophy. The Citation X was approved by Transport Canada on May 22,1998 and by the European Joint Aviation Authorities in 1999. In October 2000, Cessna announced an upgrade for all Citation Xs to be delivered after January 1, 2002. The main characteristics of this upgraded version are a 5% increase in thrust, a 400 lb increase in maximum take-off weight and improved Honeywell avionics.

When the Citation X was announced, the previous Citation family, the 650 series, which includes the Citations III, VI, and VII, was eight years old. In 1990, Cessna made a proposition for an improved 650 model to their Customer Advisory Council. The council was interested in some new elements such as increased speed and a pressurized baggage compartment. This pushed Cessna towards the Citation X program, which became the new 750 series.

Moreover, Cessna wanted to improve the image of the Citation family. The Citation models that emerged in the 1970s were originally intended to be practical and with good handling qualities. Consequently, they turned out to be much slower than the competing Learjets. Cessna had difficulties in shedding of the popular image of the Citation as a slow airplane, even though their jets had eventually become as fast as the competition.

Despite Cessna's long history of building business jets and the number of aircraft in the Citation family, the Citation X was in many ways a completely new aircraft. The wing, tail, tail cone, gear, and systems are designed from scratch and not based on pre-existing aircraft. The Citation X is also the first aircraft to use a Rolls-Royce engine and fully-integrated avionics. Although the Citation X may look similar to its predecessors, it is almost entirely composed of new parts. Part commonality is limited to some cockpit controls, the windshield, and the tail light bulb. The pressure bulkhead is also similar to previous designs. The Citation X has the same fuselage diameter as the Citations VI and VII; however, the wing attachment to the fuselage is different from the attachment in any previous Citation. See also:List of civil aircraft

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