The CJ4 is a Twin Turbo-jet airplane,
Two Williams FJ 44-4A turbo-fan engines with Full Authority Digital Engine Control (FADEC) powers the aircraft.
Undercarriage, flaps, modulated speed brakes and ground spoilers are hydraulically operated.
The main flight controls are unassisted, cable controls except for a bleed-air rudder bias system to assist in directional control in the event of an engine-out condition.
The CJ4 received its first Type Certification in March 2010, under FAA CFR Part 23 Commuter Category including day, night, VFR, IFR and flight into known icing conditions. the CJ4 received EASA certification in May 2011.
The aircraft is compliant with all Reduced Vertical Separation Minimums (RVSM).
The CJ4 airframe is a conventional, pressurised, swept low-wing design using both bonded and riveted aluminium construction with some composite parts.
Engines are fitted to short pylons on the tail section of the fuselage, above the line of the wings. The swept ‘T-tail’ structure is similar to the other CE-525 models.
Landing Gear and Brakes
The CJ4 has a fully retractable, hydraulically actuated tricycle landing gear with mechanical up-locks, pneumatic backup deployment system and mechanical nose-wheel steering.
Trailing-link main landing gear legs have an electronic, anti-skid wheel-braking system. Each leg has a single tyre, the nose wheel is fitted with a chine each side to deflect surface contamination away from the engine intakes.
The aircraft may only be operated from paved surfaces.
The hydraulic systems for undercarriage deployment and normal braking are independent for undercarriage deployment hydraulic system.
Main brake pressure is provided through a dedicated DC electric hydraulic pump and accumulator.
The pneumatic back-up system is shared by the two parent systems providing emergency undercarriage lowering and emergency wheel braking when required. The electronic braking and anti-skid systems both require DC power and are not connected to the Emergency Bus. The anti-skid system provides touch-down protection.
With the anti skid system inoperative the required landing distance is almost doubled.
The cabin is entered through the main cabin door with folding airstair located in the forward, left side.
Emergency exit is provided through a single plug door at the opposite side behind the rear cabin window, just ahead of the right engine.
There are 4 main seats in a ’club 4’ arrangement at the centre of the cabin with a further 2 forward facing seats behind.
There is a further, side-facing seat (or optional 2 seat couch) opposite the main door at the front of the cabin and a further belted (toilet) seat at the back of the cabin.
There are 2 non-pressurized baggage compartments; 1 in the nose and one in the tail section, each with a smoke detection system.
The CJ4 has a fully automatic cabin pressurisation system. Cruise level, departure and landing elevation are determined from the FMS flight-plan entries made by the pilot.
The rate and differential scheduling for flight is then computed automatically.
Landing elevation may be entered manually.
There is no manual rate or pressure differential controller. Non-automatic or standby control of cabin pressure relies on the cabin altitude limiter (max 14,800’) and the maximum differential pressure relief valve (max 9 psi).
This abnormal operation requires the cabin to be depressurised by the pilot opening the ‘Cabin Dump’ valve before landing.
A high altitude mode will automatically schedule a lower cabin pressure (higher cabin altitude) for landing at airports above 8000’ elevation.
To avoid pressure bumping on take-off, once the power levers are set to take-off power, the pressurisation system will begin to pressurise the cabin very slightly (‘down’ to approx -200’) during the take-off roll.
For this, and other reasons, reduced power take-offs are not authorised in the CJ4.
A single oxygen bottle supplies the cockpit and cabin oxygen masks. The cockpit masks are quick donning with settings for oxygen/air mix, 100% oxygen and pressure flow for high altitude and smoke protection.
Drop-down masks are arranged above each passenger seat. These are set to deploy automatically at approximately 14,800’ cabin altitude or manually by selection from the cockpit.
The CJ4 has a manual oxygen shut-off valve in the cockpit. Whilst this is not uncommon in other aircraft, all of the other 525 series aircraft have an open system that cannot be isolated in this way.
A rapid check of oxygen flow may appear normal as oxygen residual pressure is released from the line when the crew mask is tested; even with the valve selected to off.
There is no CAS message or warning to the crew that this valve is selected to off and the oxygen system is disabled.
This presents the significant risk that pilots familiar with other 525 aircraft may take-off unaware that the oxygen system is disabled and crews converting to the CJ4 from other 525 variants must be familiar with this feature and its implications.
Maximum Level for Single-pilot Operations.
The CJ4 cabin volume is small and decompression will lead to a rapid reduction of pressure in the cabin and cockpit.
When pressurization is lost, the time of useful consciousness without additional emergency oxygen decreases critically as altitude is increased, to as little as a few seconds at 45,000 feet.
To minimize the risk of an unassisted pilot becoming incapacitated before the mask can be fitted correctly, an altitude restriction should be established for single-pilot operations without wearing the mask or above which altitude the pilot’s mask should be worn continuously.
The wings are a 3-spar design constructed of aluminium mounted beneath the cabin, each with an integral fuel tank.
Control surfaces on the wing include aileron, hinged flaps, ground spoiler panels on the top and speed brake panels above and below each wing.
The right aileron incorporates an aerodynamic trim tab.
Wing leading edges are anti-iced using engine bleed air.
2 stall strips and 6 vortex generators on each wing contribute to the benign handling characteristics of the CJ4.
The main flight controls are all cable operated. Electrically operated aerodynamic trim tabs are fitted to the right aileron, right elevator and the rudder.
A secondary power circuit and control system is provided for the elevator trim, there is no manual trim mechanism available.
A rudder bias system uses engine bleed air to assist in directional control during engine-out operation.
A single autopilot is able to follow commands from one of 2 flight guidance computers (FGC) and is controlled through a single flight guidance panel (FGP) at the top centre of the main instrument panel.
The FGP is equally accessible from either cockpit seat.
The active FGC will take roll, pitch and yaw inputs from the selected PFD and accompanying AHRS, and compute flight guidance commands for the flight director and autopilot.
Lateral flight guidance modes include roll, heading, navigation and approach modes, with a half-bank function available. ‘Back-course’ approach mode is also available for use where these approaches are authorised.
Vertical guidance is computed by the active FGC and is available in pitch, flight level change (speed hold) and vertical speed modes.
A vertical navigation mode is also available when the primary navigation data is derived from the FMS.
The CJ4 is fitted with Two Williams FJ 44-4A turbofan engines with Full Authority Digital Engine Control (FADEC).
The engines are twin-spool (co-rotational) medium bypass turbofans with mixed exhaust and high-cycle pressure ratio.
Each engine produces approximately 3,600 lbs of thrust providing a considerable weight to thrust ratio of less than two and a half to one. There is no thrust reverse or thrust attenuation system.
Engine start sequence, power control, and shutdown is managed by the respective FADEC unit, each of which is independently powered by its own engine driven Permanent Magnet Alternator (PMA).
Back-up electrical power for the FADEC is the main aircraft electrical system. If a complete loss of aircraft electrical power occurs, each PMA will power its respective FADEC unit to maintain engine operation. Engine start, required thrust and shut down are selected by the pilot through the cockpit engine starter control buttons, thrust lever position and run/stop buttons respectively.
Distinctive détentes are provided at take-off, climb and maximum cruise power settings for ease of operation.
There is no separate fuel cut-off other than through the FIRE buttons, which also isolate the hydraulic pump and the generator field circuit on the respective side for emergency engine shutdown.
Each engine has a dual ignition system with 2 igniters controlled by the FADEC fired either singly or together as required by the FADEC. Ignition is activated automatically for starting and on approach to land and whenever a loss of combustion, excessively low engine speed or rapid deceleration is detected by the FADEC.
The pilot may also select ignition manually to on at any time.
Whenever ignition is active the message IGN appears in the EICAS display beside the N1 tapes.
Each wing houses an integral tank which feeds, via return fuel motive flow and ejector pumps, into a feeder hopper for the respective engine. Each side has a 433 usg capacity providing 2,914 lbs of useable fuel per side (= 5,828 lbs total useable capacity).
There is no cross flow system but fuel can be transferred from one hopper to the opposite hopper by the pilot moving the Fuel Transfer selector knob in the cockpit.
Maximum fuel imbalance for normal operations is 200lbs.
A Single Point Refuelling (SPR) system is available through an access panel in the fuselage, just ahead of the right wing leading edge root. Normal, over-wing refuelling caps are also provided on top of the outboard end of each wing tank.
Standby boost pumps are activated by FADEC for starting or if a low fuel pressure condition is detected, automatically during fuel transfer and if selected manually to ‘on’ by the pilot.
The Crew Alerting System (CAS) will display a message whenever an abnormal fuel system condition
is detected, a fuel boost pump is activated or fuel is being transferred. A separate “Low Fuel”
annunciator in the centre of the instrument panel also indicates a Low Fuel Level condition.
Instruments and Avionics
The CJ4 is equipped with dual Primary Flight Displays (PFD) and dual Multi-function Displays (MFD)
Collins Proline 21 EFIS displays and Collins 3000 series Flight Management System (FMS).
The aircraft is fitted with two Control Display Units (CDU) for the FMS.
The avionics and the FMS are fully integrated and some of the aircraft main systems are also operated through the FMS CDU (eg pressurisation).
Other main and ancillary aircraft systems are monitored and controlled through menus available from within the PFD or MFD screens (eg TAWS, weather radar, ACAS, electrical system status and Crew Alerting System (CAS).
The systems and avionics integration of the CJ4 means much of the information available to the pilot is via sub-menus from within a main PFD or MFD control panel selection.
The availability of this information is not immediately intuitive and pilots must have specific knowledge and systems familiarity to be able to access to the information quickly, when required.
The standby instrument display is a single ESIS unit in the centre of the instrument panel.
The instrument is powered by its own dry-cell battery. This instrument receives information from its own (standby) AHRS and ADC and is designed to provide attitude, heading, airspeed and altitude indications for 55 minutes following the loss of the main aircraft power supply.
The CJ4 is equipped with a fitted ELT.
Electronic Flight Bag (EFB)
The CJ4 is equipped with the Collins Integrated Flight Information System (IFIS) including electronic terminal charts (en route charts are not available from the system).
Chart prioritisation is offered according to the FMS flight plan, with origin and destination charts immediately available on either MFD, however It’s not possible to view a full chart page on the MFD due to the screen size. Only approximately ¾ of the chart is visible, although it is possible to scroll the chart to see the top or bottom.
Collins IFIS complies, in most respects, with the requirements of Class 3 EFB. The installed software applications qualify as Type B. However, the IFIS system is powered through the aircraft’s main DC power system. The system is not on the emergency bus and so there is no standby power for the system.
The system is not therefore suitable for approval for a paperless operation and back-up charts must always be carried on board.
Own ship position (FMS position) is presented on many of these charts. Where own ship position is not available the ø symbol is presented in the top right corner. A digital reproduction of the chart title is continuously displayed when the chart is in view whether scrolled, zoomed or rotated.
Many of the charts are not drawn exactly to scale and the aircraft position may therefore appear incorrect. Unless a digital Airport Moving Map (AMM) has been used for the taxi chart, the error in the chart can be so large as to present the incorrect taxiway under the aircraft position symbol.
This can be misleading and pilots must be made aware that, when referring to the aircraft symbol, the apparent position may be incorrect.
Due to the risk of inaccurate position display it is imperative that pilots are made aware that the IFIS charts are there for convenience and situation awareness only and are not to be used for navigation, either in the air or on the ground – particularly in conditions of low visibility.
Satellite derived graphical weather data overlays, enhanced map overlays (geopolitical, airways, airspace etc) and ACARS data are also available from this system as options.
Other electronic flight bag items such as performance calculations, load sheet and aircraft log did not form part of this system at the time of the OEB evaluation. It is understood that these programmes will become available. If, ultimately, these are intended for operational use a further OEB evaluation may be required on these elements of the IFIS.
The CJ4 has a single, closed-centre hydraulic system. This is unlike all the other C525 aeroplanes, which have an open system that is pressurised on demand by the closing of a single bypass valve.
The CJ4 system is continually pressurised to 3000 psi by two engine-driven pumps providing hydraulic power on demand to the four hydraulic aircraft subsystems. Landing gear actuation, wing flaps, speed brakes and ground spoilers all use this hydraulic pressure for operation. Wheel brakes use their own dedicated hydraulic supply and accumulator and are not part of this system.
The CJ4 uses two DC starter-generators as the main source of electrical power through two, Digital Generator Control Units (DGCU). DC power is then distributed through a series of DC buses and shared by way of a cross-feed bus, protected each way by 225 amp current limiters, in the event of a single generator shutdown.
Backup DC power is available from two engine-driven alternators, normally providing AC power to the windshield heating system. In the event of dual generator shutdown, one or both alternators are automatically switched through their respective Transformer Rectifier Units (TRUs) to provide essential DC power. Power storage for starting (and emergency power – see below) is available from a single 26.4 volt, 44 amp-hour lithium-ion main aircraft battery. A nickel-cadmium or lead acid battery is available as an option if required.
In the event of the battery becoming the only source of electrical power, automatic load shedding is achieved by the pilot selecting the emergency bus.
The battery will then supply power to essential systems, including the main pilot’s PFD, AHRS 1, ADC 1 and essential avionics for at least 30 minutes of flight. The Electronic Standby Instrument System (ESIS) display is powered by its own dry-cell battery.
This instrument is supplied by its own AHRS and ADC and is designed to provide indications for 55 minutes.
Any ancillary unit (except windshield heat) that requires AC power generates its own AC through a dedicated inverter within that unit.
The main electrical system also provides back-up power to the FADEC unit for each engine.
Crew Alerting System
The CJ4 systems are monitored through the Crew Alerting System (CAS). There are over 100 CAS messages that could appear (normally appearing in the upper part of the MFD) either on the ground or during flight.
The messages are colour-coded cyan (blue) amber and red to reflect normal, cautionary and emergency conditions as appropriate. It is not reasonable for the pilot to remember all the appropriate actions for each of these and a comprehensive Quick Reference Handbook (QRH) need so be immediately available in the cockpit for every flight.
The systems architecture is such that emergency memory items are few, however the inter-relationship between systems and their automation means that a series of messages may appear at one time, revealing a number of symptoms that may be the result of a single system fault. Uninformed reliance on the QRH may cause confusion and result in inappropriate action or delay by the pilot.
Although, the most urgent or compelling message is normally prioritised to the top of the visible list, any such situation requires a thorough understanding of the systems by the pilot.