by
Matt Thurber
-
May 3, 2021, 8:55 AM
Textron Aviation’s largest jet—the Longitude—is gaining ground in the super-midsize market. As of the end of 2020, the company had delivered 31 Longitudes, following certification in September 2019.
Although it shares the flat-floor cabin width and height dimensions of the Latitude, the Longitude is a fairly big step up from its smaller sibling. With a maximum takeoff weight (mtow) of 39,500 pounds, the Longitude is longer, by 3 feet, 5 inches in cabin length and 10 feet 11 inches in overall length.
The Longitude’s extra 8,700 pounds in mtow enables it to carry another 3,706 pounds of useful load, most of that fuel (14,500 pounds total, or an extra 3,106 pounds compared with the Latitude). And that translates into significantly added range, enabling the Longitude to carry a full-fuel payload of 1,600 pounds (1,000 more than the Latitude) and fly 3,500 nm, compared with the Latitude’s 2,700 nm (each with four passengers).
Powered by two 7,665-pound thrust Honeywell HFT7700L turbofans, the Longitude’s maximum cruise speed is 483 ktas and maximum operating limit speed Mach 0.84, putting it way ahead of the Latitude’s 446 ktas and Mach .80.
Although some buyers might upgrade from a Latitude to a Longitude, most are likely comparing the biggest Citation to its super-midsize competitors, which include the Bombardier Challenger 350, Dassault Falcon 2000S, Embraer Praetor 600, and Gulfstream G280.
While slower than the Longitude (by 12 knots at high-speed cruise), the Praetor can fly about 500 nm further (but at a long-range cruise speed that is 16 knots slower). Both share the same six-foot cabin height, but the Praetor is wider at 6.8 feet versus the Longitude’s 6.4 feet and its cabin is a little more than 2.5 feet longer.
The Longitude and Challenger 350 are fairly close in performance, but the Longitude is slightly faster and has greater range (3,500 nm with four passengers versus the Challenger 350’s 3,200 nm with eight passengers), while the 350 has a wider cabin by about 9.5 inches.
Compared to the Falcon 2000S, a larger difference in cabin width is apparent, 7.7 feet in the Falcon versus the Longitude’s 6.4 feet, and the Falcon has two inches more height. Both offer about the same high-speed cruise over 480 ktas, but the Falcon’s maximum speed is higher at Mach .862. The Falcon’s range with six passengers is 3,350 nm compared with the Longitude’s four-passenger 3,500 nm.
Gulfstream’s G280 has slightly more height than the Longitude, but the G280’s cabin has a dropped floor instead of the flat floor of the rest of these airplanes. Its cabin is wider by half a foot and length just over half a foot longer. With a maximum operating speed of Mach .85, the G280 is slightly faster than the Longitude at Mach .84, and its range is also 100 nm longer.
The Longitude’s spacious flight deck features Garmin’s G5000 avionics suite with four touchscreen controllers.
Unique Design
When Textron Aviation announced the Longitude program at the EBACE show in 2012, many assumed that engineers took a shortcut by grafting the wing of the Hawker 4000 onto a longer Latitude fuselage. The Longitude wing does owe some heritage to the Hawker 4000, but only in the shape of the wing’s airfoil. The wing design itself is the product of optimized design not only aerodynamically but for manufacturing. In the Citation factory in Wichita, new vertical jigs and robotic manufacturing technology and machining processes are combined to create the Longitude’s new light and strong wing. The machined wing skins’ contours are peen-formed. Wing spars and ribs are also machined, and this contributes to a total wing part count 17 percent lower than earlier designs.
For this class of business jet, the cabin is the attraction for the buyer, and the Longitude designers took care to deliver a quiet and comfortable travel experience.
From the start of the design process, acoustics engineers applied the latest acoustic treatments to eliminating sources of noise in the cabin, something that potential customers had been seeking. These included careful placement of duct fans to minimize noise.
The low noise, a full two decibels lower in the aft cabin than the quietest of its competitors, according to Textron Aviation, combined with the low cabin altitude and high pressurization differential of 9.66 psi for an improved cabin experience. At the maximum operating altitude of 45,000 feet, cabin altitude is 5,950 feet. At FL410, cabin altitude drops below 5,000 feet.
The Longitude has one air-cycle machine that works with an inline heat exchanger to condition cabin air. Either system can handle the cabin’s air needs by itself, and if the air-cycle machine fails, the heat exchanger acts as a capable backup, although maximum altitude is then limited to FL400.
Two double-club seating areas are standard, but buyers can opt to replace the two pedestal seats on the left rear with a three-place couch. A single side-facing seat can be fitted opposite the main entry door, but this cuts into the galley space. The Longitude’s seats are new, one of the benefits of Textron Aviation’s purchase of Wichita-based furniture manufacturing assets from UTC Aerospace Systems in 2015. Textron Aviation now makes its own interior furnishings, which improves quality control and allows it to respond better to customer feedback.
The pairs of opposing seats can fold flat to create a bed, so that means four beds for the double-club configuration or three plus the couch, which unfolds into a larger bed. The couch has seatbelts for three passengers, which can be used for takeoff and landing, but it is wide enough to fit four while in flight. Opening the couch into a bed is a simple matter, with just a single point to grab to make the move.
Just forward of the main door on the left side is a 14-cu-ft closet with hanging storage and removable shelves. Another option is a stowable jumpseat at the forward side of the closet. The lightweight (40 pounds) jumpseat can be removed when not needed, and then that space can be used to store items that can fit into that vertical space, about 4 cu ft. The jumpseat can face forward or aft and is useable during takeoff and landing.
The extra length of the Longitude allowed for a larger galley with plenty of workspace and dedicated crystal storage, including space for long-stemmed wineglasses. Two hot water tanks are standard. An optional high-power electrical outlet allows for use of standard appliances like coffee makers, eliminating the need to spend tens of thousands of dollars on approved installed appliances. The outlet is mounted inside a stainless-steel surround to protect the galley from fire risk. This option allows use of appliances that draw up to 15 amps of AC power. A convection or microwave oven are also optional. Both the galley and cabin are available with optional stone flooring.
For passenger utility, there are two USB ports at each pedestal seat. Universal power outlets are available at seats 5 and 6, in the flight deck, and in the lavatory vanity. Gogo’s Avance L5 air-to-ground domestic U.S. airborne connectivity system is standard, and for travel outside the U.S., optional dual-channel Iridium or Inmarsat SwiftBroadband satcoms are available.
The cabin management system (CMS) is controlled wirelessly from a smart device app, with surround-sound provided by Alto Aviation. The app also controls temperature, lighting, and window shades, but separate controls for the latter two are also available at each seat. Textron Aviation has moved away from dedicated physical CMS controls, relying on app-based controls, to eliminate the problem of CMS obsolescence.
The audio/video system stores up to 400 GB of content, which can be sent via Bluetooth to smart devices. Updating of audio/video content is via a USB input port at seat 6. An HDMI and auxiliary audio input port are also located at seat 6. SiriusXM satellite radio is available as an option. For display of moving maps and other content, an optional 22-inch monitor can be mounted on the aft divider.
The lavatory can be used as a seat, but not for takeoff and landing. Added natural lighting comes from a window in the lavatory. An externally serviced vacuum--assist freshwater toilet was the result of customer input, and this is a first for a Citation. Its 6.4-gallon heated holding tank is located outside the pressure vessel, which keeps odors away from the cabin.
Behind the full-length mirror is access to the 98-cu-ft, 1,000-pound capacity baggage compartment. Up to two people at a time can access the baggage compartment in flight, with no altitude limits. Exterior access to the baggage compartment is easier with a low threshold at about 4.5 feet from the ground. For overseas operations, the optional life raft has a dedicated storage space in the baggage area.
The interior for the Longitude flown for this report included the optional three-place couch in the rear seating area.
Systems Details
The Garmin G5000 avionics in the Longitude are the latest iteration of the G3000/G5000 suite that Textron Aviation has adopted for most of its Citation business jets. Although not yet available, the Longitude is slated for an optional Garmin GHD 2100 head-up display (HUD), which will show imagery from an Elbit enhanced flight vision system (EFVS) and also Garmin’s synthetic vision system. The HUD will be a $284,000 option, while the EFVS will add another $550,000, according to the Longitude optional equipment guide.
“The big thing we're working on right now is HUD and EFVS,” said Kevin Steiner, director of engineering for the Longitude program. “That's an ongoing program to finish the development and certification activity, which will be a first for us as a company.” Two of Textron Aviation’s flight test Longitudes are equipped with HUD/EFVS, and certification activities are targeted for completion this year.
The Longitude flight deck has four touchscreen controllers used to operate the avionics and many of the jet’s systems. Synthetic vision, ADS-B In and Out, Class A TAWS, and TCAS II Change 7.1 are standard features. Dual Honeywell Laseref VI ring-laser gyro-based inertial reference systems are available to replace the standard dual Litef AHRS. For authorization--required precision GPS approaches, RNP 0.3 is available. An Iridium-based satcom for the flight deck is standard and allows voice calls, text messaging, access to Garmin Connext weather, position reporting, and transmission of maintenance diagnostic data. A two-year subscription to the diagnostic data service comes with the purchase of a Longitude.
Garmin’s SurfaceWatch runway safety system is an optional feature, as are FANS 1/A+ and LINK 2000+/ATN B1 controller--pilot data link communications.
Also standard in the Longitude is Garmin’s new solid-state GWX 8000 StormOptix weather radar with a larger 14-inch antenna. Radar features include a high-definition 16-color palette with "greater color contouring," 3D volumetric scanning with automatic tilt adjustment to scan and depict hazardous weather, hail and lightning prediction, turbulence detection, advanced ground clutter suppression, and predictive wind-shear detection (which is optional). The wind-shear detection feature provides aural notifications and visual indications.
The Longitude is a relatively large airplane, and the Garmin autothrottle system helps lower the pilot workload, especially in busy terminal airspace. Autothrottles also enable other functionality, such as the emergency descent mode, low- and high-speed envelope protection, and coupled go-arounds after a missed approach.
With a predominately DC electrical system, the Longitude shares electrical architecture with the Latitude and Sovereign. The split-bus design has the left engine generator running the left electrical system and the right generator the righthand system independently, unless there is a failure requiring the systems be tied together. For backup, the Honeywell 36-150 APU has its own 500-amp DC generator and can run at up to FL350. The APU can also be operated unattended on the ground, a first for a Citation model. If something happens such as a fire or fuel leak while running unattended, the APU shuts itself down.
Two lightweight True Blue Power TB44 lithium-ion batteries are standard in the Longitude, but buyers can opt for NiCad batteries, which would add another 54 pounds. Buyers haven’t been selecting that option, according to Steiner.
There is one system that uses AC power on the Longitude, and that is the heated windshields, which are powered by inverters. This is the same system on the Latitude.
A unique feature on the Longitude is fly-by-wire control of the rudder and spoilers, which save weight and allow finer control of yaw, bank, and ground spoilers. The ailerons and elevators remain controlled with pushrods and cables, while the flaps and horizontal stabilizer trim are electrically actuated. The rudder is controlled electronically but actuated hydraulically. With fly-by-wire control, rudder deflection is scheduled against airspeed, limiting rudder travel at higher speeds. “It’s full-time yaw damping and turn coordination,” said Steiner.
For maximum redundancy, the rudder has two independent control systems, either of which can operate the rudder, and a rudder standby system in case those fail.
The fly-by-wire spoilers feature three panels on each wing. The inner panels are a ground spoiler only, while the outer two panels are speed brakes and also aid roll control. All of the panels deploy automatically as ground spoilers once the airplane senses weight on wheels.
Honeywell Power
The two Honeywell HTF7700L engines each deliver 7,665 pounds of thrust, flat-rated to 34 deg C. Honeywell delivers the engine integrated with the nacelle and thrust reversers, which makes hanging the engine on the airframe much simpler.
On-condition maintenance means there is no formal time-between-overhaul requirement for the engine. Some of its features include a wide-chord damperless fan, SLE compressor airfoil technology, low-emissions effusion-cooled combustor, and transpiration-cooled high--pressure turbine blades. Thrust reversers automatically reduce power starting at 85 knots after landing.
The HTF7000 series engine powers most of the Longitude’s competitors. “We focused on making sure we had good hot-high performance,” Steiner explained. “I think we have great performance compared to some of the other [aircraft] in this category.”
The single-point refueling panel is new, providing for complete control of the fueling process from outside the airplane. This allows selection of the fuel load at the panel and not relying on the truck’s automatic dispensing system. A remote oil-level sensor for the engines shows engine and APU oil levels at the fuel panel, although pilots can also check oil levels with traditional sight glasses.
Another aspect of simplified systems are the two ice detectors mounted just below the windshield. Instead of watching for ice buildup somewhere vulnerable on the airframe, now pilots simply wait for the icing CAS message then switch on the ice-protection systems. Pitot-static heat turns on automatically when needed, another feature that pilots don’t have to worry about.
Empennage deicing is a Cox & Company electro-mechanical expulsion deicing system. “The beauty of that is I'm not stealing bleed air off the engines,” Steiner said. “The wing leading edges use bleed air, but instead of pumping the warm out the wingtips, the Longitude system reroutes the warm air back through the leading edges to prevent melted ice from refreezing.
“We tried to focus on not just great performance, but let's also try and make the airplane very simple and easy to operate for both the crew,” he said.
The trailing-link landing gear is designed and manufactured by Textron Aviation using a special blend of corrosion--resistant stainless steel. “We’re trying to take lessons learned throughout the history of our fleet and do as much as we can to help in the corrosion environment,” said Steiner.
The design changes extend into the emergency landing gear system, which is entirely mechanical with no nitrogen--driven pneumatic backup system. This saves a lot of time during maintenance of the landing gear and while testing the emergency gear-down system, Steiner explained.
Anti-skid carbon brakes are electronically controlled and powered by dual hydraulic sources, each of which can power the brakes by itself. Emergency braking is from a hydraulic accumulator.
The airplane’s hydraulic systems feature a new power transfer and conversion unit (PTCU) developed by the Textron Aviation engineering team. The PTCU serves as either an electrical generator, powered by the hydraulic systems, or as an electric motor that can run one hydraulic system, or it can use one hydraulic system to run the other failed hydraulic system. The big benefit of the PTCU is its ability to provide backup electrical power in case of failure of the two engine-driven generators and the APU-driven generator. “As long as I have a hydraulic system functioning, with this device I can generate hydraulic or electric power using the hydraulic systems,” Steiner explained. “It's a great way to provide that extra layer of redundancy in the electrical system.”
On final for the Runway 31L RNAV approach to KHIO with autothrottles and autopilot engaged, ready for the test of the coupled go-around capability. Photo: Matt Thurber
Flying the Longitude
With a full-fuel payload of 1,600 pounds, the Longitude can fly with eight passenger seats occupied and still fly a long way with a sea level balanced field length takeoff distance of 4,810 feet. After taking off at maximum weight, the Longitude can climb to FL430 in 20 minutes. Some of the long-distance flights that have been done in the Longitude include Denver to Hawaii, Singapore to Sydney, and Columbus, Ohio, to Paris.
Textron Aviation demo pilots Alan Pitcher and David Bodiak conveniently flew the Longitude to Hillsboro Airport near Portland, Oregon, so I didn’t have to travel for this report.
The Longitude had 8,340 pounds of fuel onboard, and our ramp weight was 32,265 pounds. Weather was nearly clear with light winds, but we would have a 5-knot tailwind for takeoff on runway 31L. The rolling takeoff distance calculated by the G5000 avionics was 3,799 feet, plenty of margin on Hillsboro’s 6,600-foot runway.
Plugging in the crew weights and flight plan is so simple with the G5000 touchscreen controllers, it’s hardly even worth mentioning. With flaps 2 selected, V1 was calculated at 106 knots, VR 112 knots, and V2 124 knots.
Pitcher, in the right seat, set up the Longitude for a climb to FL410 for a speed check, departing on the BERNI3 SID south to Newport and Roseburg then east to Redmond before returning to land at Hillsboro. Bodiak sat in the cabin.
The hydraulically steered nose wheel is controlled by a tiller, which can move the nose wheel up to 80.5 degrees. The steering is smooth and precise and when combined with the 7.5 degrees of rudder steering allows a turn radius of 81 feet.
Cleared for takeoff, I lined up the Longitude on 31L and moved my left hand from the tiller to the yoke while advancing the power until the autothrottles took over. The HTF7700L turbofans spooled up quickly and accelerated the Longitude with a noticeable push, and it seemed as if Pitcher’s “rotate” call came especially promptly. I lifted the nose into the flight director V bars and the Longitude rose quickly, and it was a short time until we neared our 4,000-foot clearance level. Luckily, the approach controller cleared us to climb to FL270 so we didn’t have to stop down low. After a brief halt, we resumed the climb. Passing through FL380, the Longitude was still climbing at 2,600 fpm.
At FL410, we sped up to Mach .84 and at ISA -3 deg C, true airspeed settled at 479 knots. Fuel flow was 980 pph for each engine. Cabin altitude was just 4,900 feet. Slowing to a long-range cruise speed, Mach .739, dropped the true airspeed to 421 knots and 700 pph per engine. But typical long-range cruise is at Mach .80, which would deliver 457 ktas at FL410 and fuel burn not too much lower than maximum cruise; the Longitude likes to go fast.
Before reaching Redmond, we turned back towards Newport so the controller could give us some airspace to work in clear of traffic.
One new G5000 feature that I couldn’t help noticing is heading sync. This is a new Garmin feature in G3000/G5000 avionics, where when the autopilot is on and in NAV mode, a push of the HDG button keeps the heading bug synchronized. The words SYNC MODE show up under the heading box, indicating that the heading bug will move to new headings as the airplane changes heading while following navigation guidance. This cuts down on having to repeatedly push the heading button to sync the heading after turns while in NAV mode.
During the descent, I let the speed build up to see how the overspeed protection worked. As the airspeed turned red and started into the barberpole on the speed tape, the autothrottle pulled the power back to reduce speed, then the autopilot eased the nose higher. I pulled out the speed brakes during the descent and while at top speed and they deployed smoothly with little rumble and no pitch change.
Continuing the descent, I leveled off at 10,000 feet for some airwork. I slowed to 220 knots for some steep turns, a 180-degree turn to the left followed immediately by a turn to the right. I probably should have slowed to 200 or 180 knots; the Longitude is somewhat heavy on the controls, but they do get lighter at slower speeds, and the steep turns were a good handling exercise.
I tried the low-speed protection by slowing the Longitude in level flight all the way to stick shaker, and once again the autothrottles intervened, bringing the speed back up to keep us safe. With gear and flaps down, I flew around for a few minutes to get a feel for how the Longitude would handle at landing speeds. The controls did feel lighter at slower speeds, but the Longitude is a large airplane and sprightly handling isn’t a feature in larger jets with conventional elevator and aileron controls.
To put the autopilot through another of its paces, I flew the first approach at Hillsboro, the RNAV 31L, fully coupled and planned to try a coupled go-around. The Longitude’s G5000 avionics have another useful new feature, the ability to set a VREF+ speed, so if you want the flight director to command VRef plus a gust factor, you can dial that in. We didn’t need any factor, so left it at VREF +0.
The Garmin autopilot did a perfect job flying the glidepath and upon reaching minimums I pushed the TO/GA button on the left power lever and the Longitude transitioned smoothly back into a climb. I didn’t want to leave the traffic pattern, so shut the autopilot off with the yoke master disconnect switch and turned left to shoot another approach, this time hand-flown but with autothrottles on.
With the flight director guidance and vectors from the approach controller, I turned back onto the final approach course then with landing gear and flaps down, slowed to VREF.
Landing the Longitude smoothly was easy with the trailing-beam main gear, leaving no temptation to try to massage the flare to touch down gently. As the Longitude neared the runway, the autothrottles brought the power back and I backed them up by making sure the levers were at idle, then pulled the yoke back just a bit to level the nose. The main wheels touched just right, then I lowered the nose and stepped on the brakes while adding reverse thrust. By that time, however, we already had slowed below 85 knots and the reverse thrust was dialing back automatically so wasn’t really needed.
The Longitude is a capable airplane with excellent performance, a pilot-friendly flight deck, and a cabin that is optimized for passenger convenience and comfort. That the Longitude is one of NetJets’ most popular fractional-share options underscores its overall utility.
Cessna Citation Longitude Specifications and Performance
Price:
(typically completed and equipped) $29.765 million
Engines:
(2) Honeywell HTF7700L, 7,665 lbs
Avionics:
Garmin G5000
Passengers:
(typical) 2 crew + 9 pax
Range:
(NBAA reserves, 4 pax, 200-nm alternate) 3,500 nm at Mach 0.80
High-speed cruise:
483 ktas/Mach 0.84
Long-range cruise speed:
457 ktas/Mach 0.80
Fuel capacity:
14,500 lbs
Max payload w/full fuel:
1,600 lbs
Maximum altitude:
45,000 ft
Cabin altitude at ceiling:
5,950 ft
Max takeoff weight:
39,500 lbs
Balanced field length at mtow:
(sea level, standard) 4,810 ft
Landing distance: 3,170 ft
Length:
73.1 ft
Wingspan:
68.9 ft
Height:
19.4 ft
Cabin
Volume:
755 cu ft
Width:
6.4 ft
Height:
6 ft
Length:
(seating area) 25.2 ft
Baggage capacity:
98 cu ft/1,000 lbs
FAA certification:
FAR Part 25
Number built:
31 (Dec. 31, 2020)
Aircraft
https://www.ainonline.com/aviation-news/business-aviation/2021-05-03/cessna-citation-longitude-pilot-report