Airtest – Cessna Citation 3

It hasn’t all been smooth sailing though; introducing a totally new aircraft has its problems and the Citation Ill certainly went through its share of teething troubles. Some operators felt that development of the aircraft was being completed in the field and they were paying with inordinate downtime. Whilst there were only two ADs out on the aircraft, there were over 100 Service Bulletins and Service Letters against it. Cessna claim that these SBs and Sls are simply part of their ongoing product improvement programme and to their credit the factory has stood by its product support and warranty programme which in some cases has gone beyond the three year warranty period.

Taking a closer look at the Citation Ill, it is difficult not to notice the beautifully smooth and clean finish afforded by the bonding and flush riveting technique. The fuselage which is of circular section is constructed of three bonded assemblies joined at the upper centerline and cabin floor area. The bonding and riveting method ensures maximum strength and controls weight. The main cabin door and primary exit, is of the airstair type operated mechanically through a spring assisted cable and reel system. There is also a single, overwing, emergency exit located on the aft right-hand side of the cabin. Windshields are ‘bird resistant’ as required by FAR 25 and there are 2 DV windows. There is a fuselage tank located behind the pressure bulkhead but this stops ahead of the plane of rotation of the major engine components to meet the FAR 25 rotor burst requirements.

External baggage is located in a 66. 4 cubic foot, electrically heated compartment behind the fuselage tank, with access being behind the wing and under the right-hand engine nacelle. To the rear of the baggage compartment, entered through a hatch in the bottom of the fuselage, is the ‘hellhole’ affording access to miscellaneous aircraft systems. The single point refuelling port is located on the right rear fuselage just aft of the wing trailing edge.

The wing is an advanced supercritical section offering low drag at high speed, yet good approach and landing characteristics. This design also provides a large internal volume for strength and added fuel carrying capabilities. Built to the fail-safe design method, it is also bonded and riveted and constructed in three sections with the two outer panels joined to the centre carrythrough section, around two main spars providing true structural integrity. Each wing incorporates 1 aileron, 3 flap sections and 4 spoilers. The flaps (single slotted Fowler type) are of Kevlar/ graphite composite structure and are electrically actuated via flexible drive shafts. The ailerons and the outer spoiler panel provide roll control with the spoiler activated once the aileron is deflected more than three degrees. The centre two spoilers on each wing provide fully modulated, in-flight drag control whilst all eight spoilers are available for emergency descent and lift dump after touchdown.

The horizontal stabiliser is a one-piece swept design atop a vertical stabiliser and rudder in typical ‘T’ configuration to minimise drag. Trim is accomplished by varying the incidence on the horizontal stabiliser through an AC motor and backed up by a DC motor. The rudder incorporates a boost system to minimise yaw in asymmetric thrust situations.

The trailing link undercarriage is comprised of dual wheels and brakes and provides consistent smooth landings. The nose wheel is a single wheel with a chined tyre. The undercarriage is hydraulically actuated and has two emergency systems to extend it, should the primary systems fail. The first is a simple mechanical system utilising cables to release the uplocks to allow the gear to free fall and lock down. The second system is a pneumatic system to blow the gear down should the first system fail. Nose wheel steering is hydraulically actuated and has two levels of sensitivity. The tiller provides 75 degrees to the left or right and once on the runway steering can be effected through the rudder pedals which provide 6 degrees of authority to the left or right. For towing and with hydraulic power off, the nose wheel can be turned 90 degrees either side of centre.

The hydraulically powered brakes incorporate a fully modulated anti-skid system. An emergency pneumatic brake system is also provided. There is a standby electrically driven pump to provide hydraulic pressure to the brakes should the main system fail.

The Garrett powerplants, almost standard on corporate jets, are housed in composite structure nacelles. The TFE-731-38- 100S turbofan engine with a sea level ISA static thrust of 3,650Ib has been optimised for high altitude flight allowing the Citation Ill to cruise at F510. Thrust reverse is achieved through the hydraulic deployment of target-type Rohr Industries’ thrust reversers. Quite a neat installation. So that completes a quick look at the outside – now let’s look at the systems.

The 3,000psi hydraulic system is powered by two pressure compensated engine driven pumps. One driven by each engine. These are fed from a hydraulic reservoir with integral reserve and an auxiliary electric pump. The hydraulic system operates the undercarriage, anti-skid brakes, power steering, ailerons, roll control spoilers, speed brakes, ground spoilers, reversers and the air cycle machine blower.

The 28 volt DC electrical system is supplied by two 400 amp generators (one on each engine). Two generator control units provide voltage regulation with reverse current, overvoltage and feeder fault protection. A three phase, 200/115 volt AC, 5Kw alternator is also installed on each engine to supply power to de-ice the stabiliser. Two solid state static inverters supply the 115 volt, 400Hz power for the avionics.

Initial starting power, if an APU is not installed, comes from two 22 amp-hour, 24 volt nicad batteries. These are also available for emergency power supply.

The aircraft electrical distribution system employs a dual bus that is physically and electrically separated. Power to all essential equipment is maintained in the event a single power source fails.

The flight controls employ pushrod and cable systems to actuate the rudder, elevator and ailerons. The rudder and ailerons can be manually trimmed by tab wheels installed on the pedestal. Pitch trim, as previously mentioned, is accomplished through the use of control wheel mounted switches which activate an AC motor. The back-up system is powered by a DC motor. There is an integral control lock provided which holds the ailerons, rudder, elevator and throttles. The ailerons are hydraulically powered, but can be used manually should there be a hydraulic failure.

The four spoilers on each wing are also hydraulically powered.

The outboard spoiler with the aileron provides roll control. The two centre spoilers are used as speed brakes and the inboard spoiler is used as a ground spoiler. In the event of a main hydraulic failure an electrically driven stand-by pump will supply pressure for the roll control spoilers.

The fuel system with a capacity of 7,384Ibs is divided into three sections, one tank in each wing and a fuselage tank. The fuselage tank feeds the wings. Refuelling can be accomplished through either pressure refuelling or overwing. The primary fuel pumps are ejector pumps, with DC electric pumps for starting and backup. The gauging system is of the capacitance type. There is no requirement for ‘Prist’ or any such additives as the tanks are coated for protection and fuel heaters are provided.

The 9. 7psi cabin differential provides an 8,000ft cabin at a cruise altitude of 51,000ft. Bleed air from each engine, governed by an electro-pneumatic pressurisation control system, provides the source for pressurising the cabin. The bleed air is routed through dual air cycle machines, either of which is capable of maintaining sufficient flow through the cabin should the other fail. Cabin temperature, controlled from the flight deck, is maintained by mixing high temperature bleed air with the cooled air from the dual air cycle machines. Conditioned air flows through sidewall ducts while cool air flows through overhead eyeball vents.

Engine bleed air is also used for anti-ice protection of the engine inlets, the windshield, rain removal from the windshield and anti-ice of the wing leading edge. The angle-of-attack probes, static vents and pitot tubes utilise DC power for anti-icing whilst the leading edge of the horizontal stabiliser utilises AC power. The Citation Ill cabin, whilst not the largest in its class, is nonetheless very comfortable and has an airy feeling about it. The dropped aisle allows 5’10” of walk around headroom for about half the length of the cabin’. Then there is a flat floor section for the rear pair of seats with another dropped section in the toilet area to allow full headroom. A typical cabin layout has six individual seats and a sideways facing seat with a forward galley.

Most Chief Executives will find a cabin design to their liking as Cessna offers a virtually unlimited choice.

The flight deck is of typical Cessna design, not unlike the other Citations. It is quite comfortable and well laid out. The five tube EFIS installed in the demonstrator is optional and very nice to fly with. All other instruments, including the Citation tape engine instruments are conventional and any pilot will feel right at home in the Citation Ill flight deck after only a few minutes of being ‘strapped in’.

Taxiing is straight forward. One uses the tiller for general manoeuvering and then once on the taxiway, the rudder pedals will keep the aircraft straight. Once lined up on the runway the rudder pedals are sufficient to control the aircraft on the takeoff roll. V1 approaches quite rapidly and there is only a light force required to rotate the aircraft with no tendency to over rotate. The general feel is typically Cessna, light, stable and positive with excellent roll control. Although one can notice the difference when the hydraulic assist is switched off, the ailerons suddenly become very heavy. The normal climb is at 250 KIAS transitioning to . 67 Mach. I must admit that I was a little disappointed in the general climb performance. Perhaps I expected more from that supercritical wing, however, that is not to say that climb performance is shabby – it is just average.

The real strength of this aircraft comes from the fact that it will always go straight to F430 before it needs to step climb further and once straight and level, it quickly accelerates to an excellent cruise speed of M. 83 with a fuel flow of around 1,200Ibs/hr. Cabin noise levels in cruise are about average for a jet of this class but the flight deck is quiet up until the time when one extends the recognition/landing lights in the nose cone. Needless to say one sequences the approach to extend the lights when down to approach speeds. At these lower speeds the emitted noise is almost indiscernible. The other annoying noise I recalled was what I perceived to be an avionics cooling fan. Whilst this was only a soft hum, it would grate on the nerves on a long flight.

Speed control of the big Citation is excellent. One can maintain a given climb or cruise speed very easily and a smooth extension of the speed brakes allows an almost indiscernible deceleration with very little pitch trim required. In the traffic pattern, the Citation III feels equally at home as it does cruising M. 83 at F450. Roll response and speed control are excellent and with a stall speed of 97kts at max landing weight of 20,000lbs the approach is comfortably slow and easily controllable. Once the power is cut, the aircraft’s clean aerodynamics allow it to float down the runway, but this is something rectified by practice and familiarity. Touchdown on the trailing link undercarriage is almost always very smooth and the dual anti-skid braking system together with the Rohr thrust reversers will slow the aircraft very quickly. Cessna, as always, have done their homework and produced a fine handling aircraft. The aerodynamics and construction are ‘state-of-the-art and the marketplace has responded by making the Citation III one of the better sellers in its class, even against some well established types require stage If your company’s travel requirements lengths of main 2,000nm, then the Citation Ill could verywell be your aircraft.