Refined Mobility: Cessna CJ4 flight test

The CJ4 is the latest development in the long evolution of the Cessna CitationJet/CJ series. While other manufacturers boast clean sheet of paper designs, Cessna has taken another tack by refining an already-capable airplane into the largest, fastest and longest-range CJ yet. 

The Cessna Aircraft Co. has been building light jets for a long time, and doing it wwell. The original FanJet 500, the prototype that spawned the Citation line, first flew in 1969. Since that time, Cessna has built upon the success of the original Citation to create a veritable dynasty of jets that have evolved to cover almost every segment of the business jet market. Cessna jets now span a range from the Citation Mustang personal jet to the muscular, super-mid-size Citation X (and its new successor, the upcoming Citation Ten). In total, it now boasts a worldwide fleet of over 6,100 Citations, which testifies to the potential that obviously existed in the original FanJet design. 

In 1989, some 18 years after the Citation first received certification, Cessna announced a makeover to its light jet line with the intended replacement of the Citation I with the Model 525 CitationJet: an airplane that would be more cost-effective to manufacture and would offer better performance and operating economies. The CitationJet would retain the original Citation fuselage cross-section, but was otherwise a new airplane, incorporating a new natural laminar flow wing, a stylish T-tail and the then-new Williams International/Rolls-Royce FJ44 engines. 

A milestone in the CJ family tree was the simultaneous introduction of the CJ1+, CJ2+ and CJ3, each of which incorporated full-authority digital engine controls (FADECs) for the first time. Among other benefits provided, the FADECs reduced idle thrust and allowed Cessna to dispense with the cute little thrust attenuator paddles that adorned the early CJs. 

I was particularly curious to fly the CJ4, as I had formerly flown both the original CitationJet and its successor, the CJ1. I thought quite highly of those airplanes, and was very interested to see how the little CJ had grown up. 

My chance to fly the CJ4 arose from a generous offer made by Ray Kuliavas, vice-president of Innotech-Execaire aircraft sales division, to let me ferry the airplane from Hamilton, Ont., to Calgary, Alta., for the Canadian Business Aviation Association 2011 convention this past July. 

Approaching the factory demonstrator, N424CJ, on the Hamilton International Airport ramp, I recall a feeling of familiarity: rather like meeting a long-lost relative. The CJ4 has the CitationJet family resemblance, but with rather more mature features. The most striking difference was the cockpit windows: the original protruding-bubble, acrylic windows have been replaced by a more streamlined forward fuselage incorporating electrically heated glass window panels. Gone is the hissing, bleed-air windscreen anti-ice system from earlier CJs and Citations. The CJ familiar T-tail remains, but it has grown in proportion with the airplane. 

The aircraft captain and demonstration pilot for my flight was Gary Read from Cessna in Wichita, Kan. Read conducted a combination preflight inspection and guided tour, allowing me to quickly get acquainted with the new model. 

Although the CJ4 has a largely conventional, riveted aluminum structure, the exterior surface looked like glass. I was told the CJ4 fuselage is built from the outside in, with the skins held under vacuum against moulds and the interior structure attached to it with structural adhesives. However it is done, the results are impressive. The fit and finish of the demonstrator were consistently excellent. 

The CJ4 has two generous unheated and unpressurized baggage compartments. The 15-cubic-foot (0.42-cubic-metre) nose compartment is accessible from either side of the aircraft. The aft baggage compartment has a 55-cubic-foot capacity and is accessible through a door beneath the left engine pylon. Single-point refueling is available via a receptacle in front of the right-wing leading edge, although there is no provision to preset the fuel quantity. Cessna retained the forward-hinged, single-piece cabin door, although Read pointed out that the CJ4 door is larger than on the previous CJs. The lavatory, meanwhile, has no provisions for external service.

The new wing is the biggest innovation, and is the first swept wing in the CJ family. Cessna touts the wing as being based upon the gently swept wing design of its highly successful Sovereign jet. Visually subtle, but critical to performance, the wings have 12.5 degrees of sweep and an increased area compared to the CJ3. The new wing gives the CJ4 a maximum operating Mach of 0.77. 

I always stop to critically look at the leading edges of wings, as the aerodynamic appliances installed thereupon can tell a story about the challenges the airplane overcame during certification. The CJ4 leading edges were clean, with the exception of several small triangular wedges that Cessna calls disruptors. They serve to energize the flow at high angles of attack and to tame the stall handling qualities. They must be effective, as the CJ4 is one of very few T-tail jets that did not require a stick pusher for certification. 

A pleasant big airplane feature on the CJ4 is the modulated speed brakes on the upper- and lower-wing surfaces. Additional spoiler panels are enabled via a weight-on-wheels sensor, but still require manual deployment to dump lift upon landing. These features, in addition to the digitally controlled, steel-disc, anti-skid brakes, afford reasonable landing performance without the need for complex thrust reversers. 

There is almost nothing to inspect on a jet engine. The oil quantity sight gauge is easily visible; however a ladder is required to add oil. The CJ4 incorporates two Williams/Rolls-Royce FJ44-4A turbofan engines with dual-channel FADECs. Each engine produces 3,621 pounds of thrust at sea level, static conditions, flat-rated to 26 degrees Celsius (79 degrees Fahrenheit). FADEC greatly simplifies engine management. Detents in the throttle quadrant have preset positions for idle, high-speed cruise, climb and takeoff. The FADECs assume responsibility for regulating power, synchronizing engine output and monitoring limitations during engine starting and operation. Power for the FADECs is self-generated from permanent magnet alternators mounted on each engine. The engines themselves have a 5,000-hour time before overhaul. 

On the CJ4, Cessna is using a lithium-ion battery for the first time. This provides about a 15-kilogram (33-pound) weight-savings over lead-acid alternatives. The 44-Ampere-hour battery also incorporates internal computer diagnostic monitoring, and the ability to report an internal malfunction or even the loss of a single cell. 

With the preflight inspection complete, it was time to settle into the cockpit and prepare to point the jet westward.

The CJ4 retains the traditional floor-mounted control yokes. The overall layout of the cockpit seemed familiar from my previous CitationJet experience, but improvements were in evidence. Lighted pushbuttons replaced toggle switches for most applications, and an evident effort was made to locate important controls at eye level and to minimize head-down time. The flight guidance panel was mounted, airliner style, under the glareshield. The control display units for the optional dual flight management systems (FMS) were mounted side-by-side on a new tilt panel beneath the main instrument panel. Relocation of the FMS facilitated data entry, and allowed for a centre console that is short and canted downward, making cockpit ingress more convenient. The avionics system is a four-screen version of Collins Pro Line 21, and follows the theme of improving efficiency and reducing pilot workload.

Owing to requirements for single-pilot certification, most of the system controls were on the left side of the panel. I could foresee no scenario where a solo pilot would need to reach across the cockpit in flight. Also, transitioning into the CJ4 is made easier and less costly by the fact that the CJ4 shares a common CE-525 type rating with its various CJ siblings.

As with most modern designs, this is a very electric jet. The electrical system incorporates both dual DC generators and dual AC alternators. In normal operation, the alternators power the electrically heated cockpit windows. In the event of a generator failure, the alternators can provide power through transformer rectifiers to supply the DC busses. Given the reliance upon electrical power, it is particularly re-assuring that even a dual generator failure would result in only a yellow, non-critical warning on the caution and advisory system and a limited loss of systems functionality. 

For the ferry flight to Calgary, our aircraft had a basic operating weight (BOW) of 10,416 pounds (4,725 kilograms), inclusive of the two crewmembers. With four passengers on board, 100 pounds of baggage and full fuel, our ramp weight was 16,970 pounds. This amounted almost precisely to the maximum takeoff weight of 16,950 pounds, or 100 pounds below the maximum ramp weight of 17,070 pounds. 

My eyebrows arched briefly as we discussed the loading numbers. In our configuration, the CJ4 had a full-fuel payload of 826 pounds, which amounted to only four passengers and minimal luggage. Admittedly, Cessna demonstrator was equipped with about 175 pounds of options above the published BOW, but our numbers imply that some missions may require a compromise between the 2,118-pound advertised maximum payload and the 2,002-nautical-mile (3,710-kilometre) advertised maximum range. 

Even with that compromise, the CJ4 does offer considerable operating flexibility (and few jets will actually allow you to fill the seats and fill the tanks in any case). Based upon Cessna notional empty aircraft weight, one could fill the seats and carry about 50 pounds of baggage per person to a range of almost 1,500 nautical miles. Beyond that range, you may need to either stop for fuel or leave someone behind.

Engine starting was FADEC simplicity. With the pre-start checks completed, the engine run/stop button was selected to run, and the associated engine starter pushbutton was depressed. Under the FADECs watchful eyes, the engines started themselves. Following a few more checks, it was time to taxi. 

While the Pro Line 21 incorporates integrated electronic checklists, I couldn’t help but notice that Cessna demonstration pilot Read was reading the checks from a printed reference card. My curiosity piqued, we paused to switch momentarily to the electronic format. A few keystrokes brought the appropriate checks to view on the multi-function display. The process was controlled through the avionics’ cursor control panel, with a pushbutton input required to progress down the checklist. A digitized voice prompted us as we completed the checks. It seemed to me that the automation actually increased our button-pushing workload, relegating us to working the checklist in lieu of working the aircraft. Not a particularly useful feature. A bit obnoxious, admitted Read, as he resorted back to the printed checklist. 

It was a beautiful summer day in Hamilton; the Automatic Terminal Information Service (ATIS) was reporting 20 C with winds from 260 degrees at 10 knots. At Hamilton 780-foot mean-sea-level elevation, this put the density altitude at 1,700 feet. Under these conditions, and with 15-degree flap selected, the FMS calculated a takeoff decision speed, or V1, of 103 knots; a rotation speed, or VR, of 104 knots; and a takeoff safety speed, or V2, of 116 knots. According to the FMS, the takeoff field length was a respectable 3,220 feet. 

Taxiing out to the runway, I found the idle thrust to be pleasantly low, and I was easily able to regulate taxi speed without riding the brakes. The direct mechanical nosewheel steering was suitably responsive, and tight turns could be managed using differential braking. 

We lined up on runway 24 and advanced the throttles three detents to set static takeoff thrust: click, click, click. FADEC made it easy. Even now at nearly maximum gross takeoff weight (having burned off fuel during the taxi), the acceleration was satisfying, and we were ready to rotate promptly. The published performance numbers seemed realistic. I found the rotation forces were just right, and I could capture the flight director command bars without effort. The elevator trim easily kept up with the trim changes during landing gear and flap retraction. As we settled into the climb, I recall checking my seat position, as the glareshield seemed to slightly obstruct the view ahead. My seat position was fine, so I’ll have to conclude that the glareshield was indeed a bit high. 

My ambition to time the climb to our planned cruising altitude of FL430 (Flight Level 430, a.k.a. 43,000 feet) was thwarted by a series of step climbs from air traffic control (ATC). However, when using the published climb schedule of 240 knots indicated airspeed (KIAS) to Mach 0.65, I found the CJ4 was a strong climber, indicating in excess of 2,000-feet-a-minute through FL290. In spite of ATC assistance, it took us only 26 minutes to level at FL430. Cessna claims the CJ4 can reach its certified ceiling of FL450 in 28 minutes, and can do so even at maximum operating weight. I believe them. 

We set the throttles to the cruise detent and watched the speed slowly stabilize. At FL430, under ISA +1 C conditions (i.e., 1 C above International Standard Atmosphere), our true airspeed was 422 knots, with a total fuel flow of 1,080 pounds an hour. For these conditions, the flight planning guide predicted 425 knots true airspeed (KTAS) at a fuel flow of 1,059 pounds an hour. After some inquisitive poking at the data-link winds-aloft depiction, Read determined that there might be some fuel savings to be found at higher altitude and obtained clearance to climb to FL450. At that altitude, under ISA +3 C conditions, we obtained a true airspeed of 428 knots, burning 1,000 pounds of fuel an hour. Impressive cruise efficiency, although, again, slightly below published performance. 

As with any jet, the conditions for maximum cruising speed and maximum range don’t coincide. The published maximum range of 2,002 nautical miles requires flight at the certified ceiling of FL450, where cruise speeds are 20-25 knots below maximum. The published maximum cruise speed of 453 KTAS would normally occur in the low-30,000-foot range, but the additional airspeed would come at the cost of considerable increase in fuel flow. In the interest of efficiency, said Read, most CJ4 operators will cruise in the forty-thousands. To its credit, Cessna publishes the maximum range figures at the high-speed-cruise-power setting. 

At one point, I excused myself from the cockpit to assess the CJ4 attributes from our passengers’ perspective. Cessna CJ4 demonstrator was equipped with the optional two-place divan in the forward cabin across from the entry door, and six-place, club-forward seating in the aft cabin. With the inclusion of the belted-seat lavatory, the cabin could accommodate nine passengers. I found the sound level comfortable between adjacent seats; typical of a light jet, however, it was necessary to raise one voice somewhat to be heard down the length of the fuselage. Not to worry, the Rockwell Collins Venue cabin management system provides ample alternatives to conversation. The Venue plays media on a Blu-ray/DVD/CD-compatible drive or from a 100-gigabyte hard drive. One bulkhead-mounted monitor and two 10.6-inch (27-centimetre) swivelling LCD monitors are standard; a receptacle behind each main cabin seat provides flexibility in display positioning. The system also includes an Iridium satellite telephone, a single-channel XM receiver and a moving map display. A clever panel affords control of the split-zone climate control system, LED cabin lighting and the electric, pleated window shades. I played with the window shades for a while before recalling that better toys were awaiting me back in the cockpit.

Somewhere over southern Saskatchewan, I asked Read whether we should get a destination weather update. In my old-fashioned thinking, I imagined making the request on the radio. Read poked some buttons on the panel and the weather appeared on the multi-function display (MFD). I am now officially spoiled: having seen the Nexrad data-link capability on the CJ4, I will never again be satisfied to fly without it. Data such as winds-aloft and convective activity anywhere along our route of flight were depicted in a map presentation on the MFD. 

The Pro Line 21 integrated flight information system also incorporates a database that included navaids, airways, airports and approach charts. The charts were clear, bright and nicely readable under direct sunlight. The Pro Line FMS, meanwhile, knew our arrival routing, so it automatically loaded the appropriate arrival chart. Having loaded the Calgary ATIS, we set-up for the instrument landing system (ILS) approach to runway 16, and manually loaded the approach chart. Next, I loaded the Calgary airport taxi chart, and we were ready to descend.

Read set-up a vertical navigation profile to intercept the ILS. Upon interception of the descent gradient, I retarded the throttles to idle, engaged the autopilot, and watched it guide our glide down toward Calgary International Airport. Then, I got a chance to appreciate the modulated speed brakes as they helped manage our energy during the descent. For our arrival in Calgary, the FMS said we weighed 12,400 pounds. Our landing reference speed, or Vref, was 100 KIAS, and we would require 2,688 feet of landing distance at Calgary 3,557-foot elevation. 

Our visual ILS approach into Calgary was my opportunity to hand-fly the CJ4, and it was an overall pleasant experience. I was initially a bit fast during the transition to the approach, and once again relied upon the unobtrusive modulated speed brakes to decelerate to the 200 KIAS landing-gear-and-flap-operating limit. Selection of 15 degrees flap resulted in some ballooning, but the trim afforded timely correction. Like all Citations, the CJ4 low wing seems inclined to float in ground effect, making approach speed control important. 

The touchdown was a satisfying non-event. At ATC request, we rolled long and exited the runway at the end: a busy day of Canadian Business Aviation Association convention arrivals was shaping up in Calgary.

The Citation and CJ lineage evolved during a period when Cessna had far less competition in the light jet market. Those days, however, are gone. There can be no doubt that Cessna was spurred on in the development of the CJ4 by some appealing clean sheet of paper designs from its competitors, but Cessna has certainly proven up to the challenge. With a well-equipped cockpit, efficient FADEC engines and a fast swept wing, the CJ4 is a mild-mannered jet with excellent operational flexibility  very much the next level of refinement in Cessna already successful light jet design.