AIN Special Reports

Citation X+ Pilot Report

 - November 1, 2014, 5:25 AM
Cessna Citation X+

When it came time for a refresh of the Citation X, Cessna could have taken the existing airframe and updated the avionics, added winglets and redesigned the interior–as it did with other recent “plus” models such as the Sovereign+ and CJ3+–but engineers were able to unlock more performance when they created the X+. The result is a longer cabin and better performance, including a Mach-maximum operating speed (Mmo) of 0.935, which makes the Citation X+ the fastest civil airplane, a crown it will likely wear until a supersonic business jet hits the market.

The X+ received FAA certification on June 26. The legacy Citation X was introduced in 1990 and entered service in 1996. A cross-functional team from engineering, finance, customer service and support departments formed the core of the X+ development program, according to Michael Pierce, Textron Aviation manager of technical marketing. “I’ve been with it since it began and advocate on behalf of the customer. I try to drive as much voice-of-the-customer input as I can.”

That there is more to the X+ is not obvious just from the outside, where an additional 15 inches of fuselage length is evident and winglets are standard. Inside, the cockpit features the same Garmin G5000 Intrinzic flight deck, updated cabin and Clairity cabin management system (CMS) that refreshed the Sovereign+.

While the creature comforts in the larger cabin will be most welcome to passengers, what really makes the X+ shine is the stylish new cockpit, which adds a layer of modern technology to what had become a dated flight deck. As it does in the Sovereign+, the G5000 Intrinzic system marries Garmin’s flagship Part 25 avionics suite with Garmin’s butter-smooth autothrottles. In the X+’s case, however, add to that recipe an upgraded engine, Rolls-Royce’s 7,034-pound-thrust AE3007C2 with a high-flow fan and new first-stage compressor design that improves thrust in all regimes: takeoff by 4 percent; climb by 9 percent; and cruise by 7 percent. (The later-model X’s -C1 engine produced 6,764 pounds). Thrust-specific fuel consumption is 1.4 percent lower, and the engines are fitted with improved Fadecs carrying more memory for diagnostic capabilities and an interface for the Garmin autothrottles.

Time To Fly

On October 2 Cessna senior pilot Tim Baca and I taxied out for takeoff on Runway 1R at Wichita’s Mid-Continent Airport. A mess of heavy thunderstorms was dissipating east of Wichita, so we stayed west, but this gave us a great opportunity to play with the turbulence-detection and vertical-scan features of the Garmin GWX 70 solid-state radar.

Carrying just one passenger, Citation X+ N509CX (S/N 9) tipped the scales at well under the 36,600-pound mtow. The tanks carried 6,791 pounds of fuel, about half the 12,931-pound maximum. Our takeoff weight was just 28,956 pounds.

We planned a flight from Wichita to Liberal then Hays, Kan., and return to Wichita, without stops. Flight planning on the G5000 is simple: just tap the flight planning button on any of the four GTC 570 touchscreen controllers (two for each pilot) and type in the waypoints. It’s easy to add airways and procedures, too, including placement of a holding pattern just about anywhere. We did see one annoying characteristic of Garmin avionics, however. Baca was showing me how to input the flight plan while plugged into ground power, but because we didn’t save that as a saved route in the G5000, it was erased when ground power was removed to pull the airplane out of the hangar. So we had to re-input the plan after we started the APU. A neat feature with the new Garmin flight decks is the integration with the automatic pressurization system. Once the destination airport is plugged into the flight plan, the pressurization system automatically selects the destination elevation.

Cessna and Garmin are still working on the takeoff and landing data (Told) feature for the G5000, so pilots still need to set the speed bugs manually using the touchscreen controller. The Told feature should be available in next year’s first quarter. The X+ checklist is much simpler, thanks to the logical grouping of switches and controls in the new cockpit. The old rotary test is gone, although those systems still need to be tested, and this is done using the touchscreen controller. “The switchology helps reduce the workload,” Baca said.

Starting Fadec engines is such a no-brainer that it’s hardly worth mentioning. On the X+, the APU provides plenty of air for the start, eliminating the X’s dependency on a huffer cart for starting. With external power connected, the batteries automatically go offline, preventing possible overcharge. Most switches, including the APU, are now on the pedestal, and the tilt-panel area is much cleaner looking, with many switches now LED pushlights. The pedestal extends slightly farther aft, but is also angled downward more so it looks like it doesn’t take up as much space between the seats. Two air-conditioning packs are available and each can serve the cabin and cockpit, or if one fails, both areas. Simple environmental controls are available on the touchscreens.

Speedbrake, flaps and power levers are all redesigned. The speed brakes can be extended at any speed. For landing, when speed drops below Vref+15, an audible alert reminds the pilot to retract the speed brakes as the throttles move aft to a specific angle.

The cockpit was completely redesigned by the Cessna design team, led by vice president of interior design and engineering Cynthia Halsey. The control wheels are new, reflecting the cleaner look and the improved flow for the pilots. As Halsey put it in an earlier interview with AIN, “The pilots don’t have to reach around anymore and hit a switch panel; it’s right there at your fingertips. The stainless accents throughout, the leather wrap [on the yoke], it’s a driving machine. We wanted the pilot to feel like he was getting in a modern driving machine. And the [G5000] displays are so beautiful, it was a great canvas to work with.”

The parking brake is a new design, featuring an electric auxiliary hydraulic pump that allows the brake to be set without having the APU running. Flaps are now marked in “1, 2 and full” positions instead of 5, 15 and 30 degrees. In the first position, slats also actuate, and this is available up to 250 kias, or 180 knots for full flaps, the same as in the legacy X.

During engine start, the only move the pilot needs to make is advancing the power lever during the start sequence, then monitoring fuel flow, oil pressure and temperatures. There is no cutoff gate for the power levers to come over; they just need to be moved slightly from idle position, and the Fadec introduces fuel at the correct time. The flashing beacons automatically light up during start, one more item the pilot doesn’t have to think about, although this feature can be switched off in a G5000 systems page if desired.

The X+’s carbon brakes are surprisingly smooth, thanks to improved brake metering valves, and the tiller nosewheel steering makes precise turns easy. It is possible, with some twisting contortions, to see the wingtips from the cockpit.

We were cleared to expect FL400, with a “maintain 5,000 feet” stop on the way up. Taxiing onto the runway, I pushed the autothrottle engage button on the side of the left power lever then pushed the levers past 80 percent N1. This is where autothrottles shine; there is no need to fine-tune the power setting, the autothrottles take over and smoothly bring the power to maximum, which is bugged on the N1 gauge, allowing the pilot flying to concentrate on flying the airplane and the first officer to call out speeds and monitor performance.

The Citation X/X+ have hydraulically powered flight controls, and this was my first experience with this system. Hydraulic controls allow the airplane designer to fine-tune handling characteristics, which can result in a different feel for the pilot. The last large Cessna that I flew was the Sovereign+, and it shares many interface features with the X+, including the Intrinzic flight deck, autothrottles and system automation. But the Sovereign does not have hydraulic controls and thus has a much heavier feel on the controls. Rotating the X+ on takeoff, I pulled back too hard on the yoke and overcontrolled a bit until I got the hang of the lighter control feel.

Quicker Climb

The massive engines bolted to the slim area-ruled aft fuselage gave us an extra-strong push, and at our light weight we accelerated quickly to the 250-knot speed limit, climbing at 7,200 fpm through 5,000 feet. Baca smoothly handled the climb requests well in advance of ATC’s limits so we didn’t have to level off. Above 10,000 feet, we climbed at 285 kias, still powering upwards at 3,650 fpm, then settling down to 2,000 fpm through FL300, burning 1,580 pph in each engine. N1 was bugged at 89.6 and climb speed transitioned to Mach 0.852, and at FL390 we still made 1,000 fpm. At FL400, the X+’s automatic flight control system leveled off, smoothly coordinating the autothrottles and the pitch attitude to keep the occupants comfortable. Garmin’s autopilot uses more reliable clutch-free servos, which directly drive the flight control cables that are attached to the hydraulic power control units at the flight control surfaces.

The autothrottles are an integrated part of the X+ (and Sovereign+), so Garmin and Cessna engineers were able to approach the design from a systems perspective. The result is a well integrated “autothrust” system that tames the Citation X+ while extracting maximum performance. For example, the X+ can climb like crazy with a light load and at lower altitudes, and leveling off under those conditions could make passengers float uncomfortably. The G5000 system takes inputs from various sensors in the X+, adds predictive algorithms and carves out a parabolic intercept that keeps the load to less than 0.08 g so passengers hardly notice the level-off.

The autopilot also incorporates Garmin’s electronic stability and protection (ESP), which, coupled with the autothrottles, adds envelope protection features. Even with the autothrottles not engaged and the autopilot off, ESP adds an increasing level of force to the flight controls and adds or reduces power to keep the X+ within a safe envelope. Exceeding preset boundaries by, say, banking too steeply will cause the pilot to feel a nudge in the opposite direction, removing some of the excessive bank angle. If the jet slows too much, the autothrottles add power, or they remove power if speed climbs too high, and the autopilot joins in, too, if needed. Cessna also chose Garmin’s emergency descent mode (EDM) feature, which automatically engages if it detects a cabin altitude climbing above 14,000 feet (rapid or slow decompression), turns the airplane 90 degrees away from its course and descends at Vmo to 14,000 feet.

The autothrottles drive servos to move the power levers so pilots can always visualize the power setting. Pilots can override the autothrottles at any time, just by moving the power levers.

It took just 15 minutes to climb to FL400. The X+ has an interesting design feature that is evident when the airplane levels off. The autothrottles move the power back to the cruise setting, and it can take as much as 10 minutes for the speed to settle down. Baca prefers to click the autothrottles off momentarily, then re-engage them. With the speed bug set to a higher number than the airplane can achieve in those conditions, the autothrottle sets climb power to try to reach that speed. The result is a quicker acceleration to the maximum cruise speed once leveled off. With power set back to high-speed cruise, we zipped along at 525 ktas (Mach 0.90) burning 1,150 pph per engine at ISA +7 degrees C. Cabin altitude was 5,700 feet.

We decided to climb to FL450 to see what conditions there were like (maximum altitude is FL510 feet, but maximum speed is achievable at FL350). At that altitude, maximum cruise power was 88.8 percent N1 and fuel burn dropped to 940 pph each, for a speed of Mach 0.888 at ISA +3 degrees C, true airspeed of 508 knots and cabin altitude 6,800 feet.

We reached our highest speed–not quite the X+’s Mmo of Mach 0.935–during the descent, Mach 0.928. Leveling off briefly at FL410, we found that the maximum available thrust delivered Mach 0.898. A white box pops up on the PFD to indicate “at thr limit” in these conditions. Back down at FL350 at ISA +7, we were again at the thrust limit and reached Mach 0.902 while burning 1,440 pph per side. Weight at this point was about 27,000 pounds. We continued descending and returned to Wichita.

ATC brought us in way too high so I popped out the speedbrakes, which added no noticeable change to the feel of the airplane beyond helping us drop rapidly. I hand-flew the ILS to Runway 1R and again was surprised at the lightness of the controls and how the X+ feels completely different from the SUV-like Sovereign+. Baca reminded me to crab into the crosswind during the landing instead of slipping and risking scraping an expensive wingtip. As we descended below 500 feet, a chime reminded us to stow the speedbrakes, and the autothrottles automatically pulled the power back to idle. Baca explained that there was no need to flare and to just fly onto the runway. The sight picture looked odd and it felt like we were about to touch down on the nosewheel, but the main wheels touched first and then I pushed the nose down, stepped on the brakes and added reverse thrust for a reasonably smooth touchdown.

Interior Improvements

Like the Sovereign+, the X+’s interior is completely new, from the Clairity CMS to the seats. In a first for Cessna, the new seats were designed and built in-house, including qualification to the dynamic seat testing standards. Over a two-year process, Cessna interior designers and human-factors specialists worked with passengers of various sizes, having them sit in seat-shaped foam, measuring and carving the foam to fit, then building a seat frame around the resulting foam shapes. “People feel like they’re sitting in the seats, rather than on them,” said Pierce. The seats are canted inward four degrees to keep passengers’ feet centered on the flat part of the raised floor. Stowable armrests slide into the seat back when not in use, avoiding the problem of bumping into armrests that just fold up but not out of the way. Optional seat features include lumbar adjustments and footrests on rear-facing seats (they are standard on forward-facing seats). In the larger center four-club section, a stowage drawer for flat items such as laptop computers takes advantage of previously unused space in the raised floor between the seats. The drawer slides open into the dropped aisle.

The extra 15 inches of length isn’t just a plug added to the X’s fuselage but is part of an entirely new fuselage, according to Pierce. Most of the extra room shows up in the forward club section (an additional 8.6 inches). The rear club section adds 4.4 inches, and there are an extra two inches in the galley and two more inches in the lavatory. This adds up to more than 15 inches because the lavatory area was reconfigured to add extra space. The X+ cabin is 25 feet, two inches long, compared with the 23-foot, seven-inch cabin in the X. The width and dropped-aisle height are the same at five feet six inches and five feet eight inches respectively. The table in the forward club section is now wide enough so that two people can comfortably crack open their laptops.

Rather than traditional round drink holders in the side ledges, designers opened those up completely with a rail and anti-skid material so passengers can use that area to hold anything: wallets, phones, tablets, books and so on. Flip-out arms cradle drinks in the side rail area, too.

Every seat has powered USB ports and a touchscreen control panel for the Clairity CMS. The panel stays dark until touched, then comes alive with controls for lighting, entertainment, window shades and environment (for the VIP chair only, but this can be moved to any seat position). Passengers can send text messages to any seat using the Clairity controls. The control panel also displays a moving map with flight progress. Buyers can customize the displays on the panels with company logos, photos, passenger names and so on. This Clairity system is the hard-wired version, unlike some of the other new Citations such as the M2 and upcoming Latitude, which are equipped with wireless versions that don’t require the touchscreen panel. The Clairity system is built on a fiber-optic backbone developed by Heads Up Technologies.

The X+ cabin’s Blu-ray player can be hooked up to optional surround-sound speakers and additional monitors. Passengers can bring their own content and plug their devices into the CMS and play movies on the bulkhead monitor or music on the cabin speakers.

Further Improvements

The elliptical winglets that were available as a retrofit on the legacy X are standard on the X+ and enhance climb, speed at altitude and hot-and-high performance.

The electrical system now features an essential bus architecture with common grounds in the interior that help eliminate intermittent problems with interior components, Pierce said. The alternators that provided electricity for windshield heat on the legacy X now can supply backup power through transformer rectifier units to the emergency bus to keep the PFD and MFD running in case of a dual generator failure.

Kevlar hydraulic hoses were replaced with stainless steel and rerouted outside the pressure vessel.

Diagnostic information is now available on the G5000 MFD, so technicians don’t have to plug in a laptop to download maintenance information. Cessna’s Aircraft Recording System (AReS) is installed, and this basically records everything that goes through a printed circuit board in the airplane to help technicians diagnose problems. In the cockpit, pilots can push an event marker button to store 30 minutes worth of information surrounding an anomaly for later analysis.

The new flight deck and modern G5000 avionics shave as much as 150 pounds from the empty weight. ADS-B out is standard now, as well as Link 2000+ for European operations. One Gogo Biz Internet/Wi-Fi system is standard. Also included are dual Honeywell Laseref VI inertial reference units, RNP 0.3 FMS, Tcas II with Change 7.1, Class A Taws and a single HF radio. Optional avionics include SiriusXM WX, Garmin worldwide weather (via Iridium), lightning detection, a second HF radio and an ICAO Type 1A FDR.

A future upgrade to the G5000 avionics is Garmin’s SurfaceWatch system, which warns the pilot about issues on the airport surface, such as trying to take off on a taxiway or too short a runway. This will be an optional feature and will also be integrated with ADS-B in.

Climb rate with anti-ice on is improved substantially. “This is something that people weren’t happy with,” Pierce said. While the legacy X can climb to FL430 in 28 minutes, the X+ can climb to FL450 in 23 minutes.

Full-fuel payload on the X+ is 136 pounds higher and maximum payload 214 pounds greater. Long-range cruise speed (Mach 0.82) is 190 nm farther (3,242 nm) in the X+. What is interesting is that the difference between long-range and high-speed cruise for the X+ is even narrower, making the decision to go fast easier. In the legacy X, the difference is 183 nm, but in the X+ it is 135 nm, not a huge change but still a narrowing of the gap between the two speeds. “This has always been an exciting airplane,” Pierce concluded. “It does what it does well.”