Flight International puts the latest variant of Cessna's popular CitationJet through its paces
Peter Henley/WICHITA
Add a Collins Pro Line 21 avionics suite to a Cessna CitationJet, one of the world's best selling business jets, and increase its gross weight as well as payload. The result is the Citation CJ1, which Flight International recently flew from the company's plant at Mid Continental Airport, Wichita.
Because pilots tend to perform pre-flight and turnround inspections on their own small business aircraft, a walk-round tour was conducted with Chris Provencio, senior demonstration pilot. This production demonstrator, N389CJ, was fully finished and typical of an in-service CJ1. The high quality was obvious from the smoothness of the external paint finish, the tightly-stitched cream leather seats and the well-fitted panels.
The nose has a large baggage compartment which also gives access to servicing points for the oxygen system and windscreen de-icing fluid. Refuelling is via two overwing fillers. The hydraulic reservoir and sight gauge are behind a door in the fuselage side just to the rear of the starboard wing root.
The engines are mounted on the shoulder of the fuselage, rather than the waist, primarily to increase the gap between wing and cowling and thereby reduce airflow interference. The higher mounting position also helps to reduce cabin noise and allows easier access to the rear baggage compartment, the door for which is beneath the left engine.
The cabin door is behind the cockpit and in front of the port wing. It is hinged at its leading edge, latches in the open position and has 12 locking pins to secure it when closed. The steps are separate, mounted on the door strip and fold away neatly.
Clean and well finished
The straight wings are exceptionally clean and well finished, the leading edge anti-icing portion being smoothly blended with the upper surface to preserve good laminar flow.
The undercarriage has two mainwheels, each carried by a robust looking, trailing link leg and a single nosewheel. Landing lights are neatly flush mounted in the fuselage belly, their beams redirected forward through prismatic lenses.
The aircraft and, therefore, the cockpit, is small. The seats are not easy to enter but, once settled, the pilot is rewarded with a snug fit reminiscent of a classic Ferrari or a Hawker Hunter. The field of view is exceptional, most of the wing leading edge and the tip on his side being visible to each pilot.
The CJ1 is certificated for single pilot operation and, historically, about a quarter of the CJs and CitationJets are flown that way. The instrumentation is orientated for easy reach by the left seat occupant, although some switches such as the engine igniters and the anti-collision lights are quaintly positioned down by the pilot's left ankle. These switch positions cannot easily be monitored by the right seat occupant although a surprising number can be reached, in extremis, by the co-pilot.
My enthusiasm for this excellent little cockpit has to be tempered slightly by the fact that it was only just big enough for someone of my 6ft (1.8m) height. With the seat fully back and the rudder pedals fully forward, I was nevertheless rather folded up. Full-right hand-down deflection of the control yoke only just cleared my knee. The seat itself was comfortable, had a five-point harness and could be adjusted fore and aft; reclining the back rotated the entire seat and raised the front of the seat cushion. There are foldaway armrests inboard only.
Small cockpit, large displays
Surprisingly, this small cockpit quite adequately accommodates two large Collins Pro Line 21 liquid crystal displays both measuring 200mm x 250mm. Even more surprisingly, a customer option provides a third display for the co-pilot, although this particular aircraft had a basic flight instrument display at this position.
Whichever is fitted, the displays, navigation and communications controllers and standby instruments all fit neatly and conveniently into the tall instrument panel. A global navigation system is optional. The pressurisation controller, thrust levers, flap lever and airbrake (speed brake) selectors are all in the slim centre console. The undercarriage lever is mounted in the lower edge of the centre instrument panel by the captain's right knee and can easily be reached from either seat.
Cessna is enthusiastic about the CJ1's Williams-Rolls FJ44-1A turbofan engines which deliver 1,900 lbs-thrust (8.5kN) each and have fewer than 700 components compared with about 2,500 in most business jet engines. A major reduction in weight plus greater reliability and economy are claimed.
The CJ1 does not have an auxiliary power unit so engine start uses either a ground power unit or the aircraft battery. The engines have starter/generators.
The aircraft is easy to taxi precisely and accurately using the rudder pedal-controlled nosewheel steering and a little differential braking on tighter turns. The multi-disc wheel brakes are smooth and powerful but requiring quite high pedal forces.
The engine instruments are vertical strip presentations ranged across the top third of the multifunction display (MFD) on the central instrument panel. Each column is calibrated with left and right scales for the respective engines. They are clear and easy to read but lacked the compelling impact that comes with all indications for one engine on the left of the panel and all for the other engine on the right. So in an emergency there is arguably a greater chance of misidentifying an engine which has failed. The engine parameters displayed are N1% (fan speed), ITT (interturbine temperature °C), N2 (turbine speed), and oil temperature and pressure. The take-off weight was 4,500kg (10,000lbs), 300kg less than the maximum of 4,800kg, including 1,150kg of fuel.
Mid Continent airport is about 1,300ft (400m) above mean sea level. The weather was fine, the surface wind light and the temperature 22°C (72°F). A 15° flap setting was used. Provencio had determined from the performance charts that 97.9% N1 would be take-off power.
Take-off technique is to release the brakes, set N1, keep straight using nosewheel steering until the rudder becomes effective and rotate the aircraft to 10° nose-up, the flight direction bar having been pre-set to demand 10°.
The relevant speeds are decision speed (V1) 102kt (190km/h), rotate (VR) 105kt and V2 (safety) 108kt. A progressive continuous pull is needed to rotate the CJ1 to the 10° attitude, but the stick force is light. Provencio retracted the undercarriage and flap, although both levers could have come easily to my hand. Rec-ommended climb speed for the day was 190kt.
The CJ1 was instantly a delight to fly. No pitch change is associated with undercarriage or flap travel after take-off, and the control forces are light and well harmonised in pitch, roll and yaw. The breakout forces are light and the control surfaces powerful and effective. Although light and nimble to manoeuvre, there is no associated tendency to be too lively and depart from trimmed conditions. The handling characteristics are ideal for single pilot flying as the aircraft can be relied on to take care of itself for a few seconds as the pilot busies himself with air traffic clearances and the other routine distractions of single pilot instrument flying.
Cessna has achieved this harmonious handling through simple, mechanically operated primary flying control surfaces. The ailerons, elevators and rudder are trimmed manually and have trim position indicators on the trim wheels. The elevators also have electric trim through the usual two-pole switch on the control wheel. The mechanical pitch trim wheel is within easy reach (near the captain's right knee) and is so effective to use that it will doubtless be the preferred control for many CJ1 pilots.
Airbrake operation
The airbrakes (speed brakes) have two panels per wing, one extending from the top surface and one underwing. They are electrically controlled (through a guarded switch towards the rear of the centre console) and hydraulically operated. They can be either retracted or extended but have no intermediate positions. Extending them causes little pitch change but noticeable aerodynamic noise. With the thrust levers at flight idle, airbrakes extended, and airspeed of 230kts, the rate of descent is 40m/s (7,800ft per minute).
The CJ1 is not designed to be a long-range, high-altitude, high-speed aircraft. Its maximum operating altitude is 41,000ft and maximum operating speeds Mach 0.71 or 263kt indicated airspeed. Its range with instrument flight rules reserves is around 2,035km (1,100nm). The flight test CJ1 took seven minutes to climb through flight level (FL) 180 and a further 10 minutes to reach FL310. At about FL350 it began to run out of breath and much of its normal operations would presumably be in the lower 30s or below. Therefore its straight wing serves it well and handling at 35,000ft remained crisp. The aircraft exhibited no aerodynamic Mach effects and does not have, or need, a Mach trimmer. There is no provision for reduced vertical separation minima operations.
A snapshot check showed the CJ1 to have good longitudinal static stability and to be exceptionally well damped directionally. A pilot not used to the aircraft would be hard pressed to tell, merely from handling characteristics, whether the yaw damper was in or out. A 45° left bank to 45° right bank roll took 3.5s. During high angles of bank, the deep cockpit side windows give an exceptional field of view for this class of aircraft.
The CJ1 has a useful angle-of-attack (AoA) indication to the left of the captain's primary flight display (PFD), calibrated from 0.1 to 1.0. For each flap configuration, 0.6 is calibrated to represent the approach speed for 15° flaps and threshold (reference) speed for 35° flaps. It is therefore a useful instrument for flying the aircraft on the approach.
It also was useful during the two stalls flown. Provencio advised the Cessna-recommended training technique for stalling which requires the engines to be set at 50% N1 rather than power off. This technique would appear to be an engine, rather than airframe, consideration. It presumably helps protect the engines from compressor stalls at high AoA.
Clean, at 16,000ft, the stickshaker operated at 100kt and the stall occurred at 93kt and an AoA of about 0.85. With undercarriage down and flap 35° the figures were 87kt stickshaker, 82kt stall and AoA about 0.93. Aileron and rudder remained effective down to the stall which was benign and predictable.
Finally, a coupled approach to an instrument landing system approach and some visual circuits (traffic patterns) were flown. The autopilot flew the aircraft accurately and smoothly, and speed regulation by the pilot using the thrust levers was straight forward.
This aircraft has the optional Universal UNS-1K flight management system with its control display unit conveniently placed on the centre console. Similarly, the autopilot mode selection, and the altitude and heading set knobs are in the centre console. Radio and navigation frequencies are easily selected via the stack of controllers to the right of the central instrument panel. Basic mode selection on both the PFD and MFD is via bezel-mounted keys (or press-to-select buttons) and the displays themselves are relatively large, easy to read and uncluttered.
Thrust attenuators
The CJ1 has hydraulically-operated, electrically-controlled flaps. There is a take-off and approach position of 15° and a full flap position of 35°. There is an additional ground flaps position of 60° for extra drag on the landing roll and for use on the ground only. Any intermediate position between 0° and 35° can be selected.
The engines have thrust attenuators (not a full thrust reverse system). They are vertical paddles which normally align themselves behind the engine alongside the engine pylon. When selected, the paddles swing outboard across the jet eflux. They are hydraulically operated and deploy automatically when the thrust levers are idle, the aircraft on the ground and the selection switch pre-set to AUTO.
The landing threshold speed for weight (VRef) was 104kt. The CJ1 was easy to land, behaved nicely in ground effect and had a compliant, forgiving main undercarriage. The wheel brakes, ground flaps and thrust attenuators combined well to kill the lift once on the runway and slow the aircraft effectively.
The CJ1 was a particularly engaging aircraft to fly, with excellent handling qualities, simple systems, adequate performance and integrated avionics - all of which enhanced the single-pilot capability while in no way diminishing the pleasure of two-pilot operation.
Source: Flight International
