[October 25, 2013] IN FOCUS: Learjet 75 flight test Tweet (Flight International (UK) Via Acquire Media NewsEdge) The last few years have been particularly strong for Bombardier, as it worked to secure a leadership position in the business jet marketplace. According to the airframer's figures – which exclude the very-light jet and VVIP segments – Bombardier has increased its market share, based on deliveries, from 29% in 2008 to 33% in 2012. In 2012 alone Bombardier netted 343 orders – representing 64% of overall sales by value, and nearly five times more than nearest competitor Cessna. These new orders represent the fruit of Bombardier’s efforts to revitalise its product range. At the low-end, Bombardier is pushing the Learjet 70 and 75. These light and super-light models are based on the successful Learjet 40 and 45, of which 586 aircraft (including XR variants) have been delivered. Announced in 2012, the new jets follow a well-established formula for updating proven designs: improved aerodynamics, new or enhanced engines and upgraded avionics. Recently, Flight International was invited to put the newest Learjet through its paces at Bombardier’s Wichita development and production facility. I have some prior experience here: In 2012 I was afforded the opportunity to fly a modified Learjet 40, that incorporated the Garmin 5000-based Vision Flight Deck utilised on the Learjet 70 and 75. That preview aircraft was FTV2 – one of five aircraft used to develop the new aircraft. Garmin flight test pilot Tom Schaffstall accompanied me on the avionics-intensive flight, reported on in the 22 October 2012 edition of Flight International. Commentary in this article on the production-representative Learjet 75 flown incorporates observations made during my earlier flight in the avionics development aircraft. Aerodynamically, the most noteworthy change for the 75 is how the large winglets are oriented. They are less upright – canted at a 45˚ angle – than those on the Learjet 40XR and 45XR. While overall wing area remains unchanged at 312ft² (29m²), the 75 has a span of 51ft (15.5m) – around 1m longer than its predecessor. In general, for subsonic aircraft a higher aspect ratio (AR) wing will result in a higher lift to drag ratio (L/D). According to the Breguet range equation, an aircraft’s range is directly related to its L/D. Using the published wingspan and area data provided by Bombardier, the 75 has an AR of 8.31 – notably greater than the 7.32 seen on the 40XR and 45XR. According to Bombardier, the 75’s higher AR wing accounts for half of its 4% range improvement over the 45XR – 2,040nm (3,780km) versus 1,970nm (with four passengers and NBAA IFR reserves), with the other half attributed to its reduced weight. The main weight reducer is the Vision Flight Deck (VFD), which tips the scales around 90kg (198lb) lighter than the Honeywell Primus unit in the XR. The 75's fuel capacity is the same as the 45XR at 2,750kg (6,060lb). Since they share a common maximum take-off weight (MTOW), the additional weight-related range increase is due strictly to having to carry a lighter load, not any additional fuel. Like the XR models, the 75 has two Honeywell TFE731 turbofan engines. In the XR, -20BR models are used, with a thrust rating of 3,510lb-thrust (16kN), while the updated jets get the 3,840lb-thrust-rated -40BR variant. This shares the same fan and compressor as the -20BR, with the 10% thrust increase due to improvements in the hot section and digital electronic engine control (DEEC) programming. These improvements allow increased inspection intervals and reduced operating costs. Where the additional thrust will be most appreciated is during take-off. At sea level on a standard day the 75’s take-off distance is 1,353m (4,440ft) – 12% shorter than the 45XR’s 1,536m. While a notable improvement, the 75 still needs appreciably more runway than the Cessna Citation XLS+, which needs only 1,085m. Landing is a different matter, where the advantage swings to the 75. Sporting large brake-by-wire carbonfibre brakes, the 75 needs a landing field length (SL STD DAY MLW) of only 811m – 156m shorter than that listed for the Citation XLS+. Unlike the developmental aircraft I had flown, the preview flight 75 featured a production cabin interior. Unique in this segment is its double-club seating configuration. The 75 carries a 2013 BCA list price of $13.8 million. The next lowest-cost aircraft to offer a double club cabin is the Cessna Sovereign, with a price tag of $18.2 million. The 75’s cabin has a vertical oval cross-section that features a flat floor with 1.5m of headroom. The Citation XLS+, its closest competitor, has a 33cm-wide dropped aisle that increases aisle headroom to 1.73m – head and shoulders above that on the 75. Sidewall cabin width in the 75 is 1.56m, 12cm narrower than the Cessna XLS+, which shares its circular cross-section cabin with the Sovereign. While the XLS+’s dropped aisle will no doubt be appreciated when moving about the cabin, once seated the Learjet’s cabin will likely seem every bit as spacious as the Cessna’s. The closet opposite the cabin entry door in the XR models has been removed, allowing for an enlarged galley with a pull-out work surface. Hanging storage is now provided opposite the commode in the aft lavatory. With transcontinental range, cabin size is not all that matters. In the increasingly connected world, broadband access and digital entertainment rule the roost. Airborne broadband access is provided by one of two optional systems – SwiftBroadband or Iridium with ATG. The cabin management system (CMS) is Lufthansa’s HD kit. The high definition system has an ethernet backbone and allows for a number of interfaces, including an iPod docking station, as well as an optional Blu-ray player. Each of the eight cabin seats has touchscreen display. The 17.8cm stalk-mounted displays (only 11cm on the emergency exit seats) slot into the sidewall armrests. Wireless internet access is available in the cabin, but wireless streaming of digital media content from the system to passenger tablet-type devices is currently unavailable. I accompanied Bombardier demonstration pilot Greg Eastburn as he carried out the pre-flight walkround. The inspection procedure was similar to other business jets, with only a few panels needing to be opened, however, the 75’s wing caught my eye during the inspection. It is a fixed leading edge with three discrete steps/profiles. The unusual design is optimised to give the wing slatted-like performance at low speeds, without sacrificing high-speed efficiency. While the passengers are well cosseted, it was when I sat down in the cockpit that I was reminded of how well the flightdeck is appointed. The forward panel is graced with three large 14in Garmin wide-format displays, which provide twice the viewing area of the XR’s four CRT displays. While the interchangeable panels have 12 buttons on their lower bezel edge, the primary interface for the VFD is via two pedestal-mounted control display units (CDUs). The Garmin GTC 570 CDUs feature a 5.7in HD touchscreen. As I had experienced on my previous flight I found the GTC 570’s infrared-based virtual button-push feature to be quite effective, and only recognising authentic “pushes.†While there is no tactile feedback, audible feedback is available, with a “clunk†sound signifying an unexecuted push. Pre-start checks were accomplished by reference to a paper checklist, rather than the 75’s standard electronic checklist. The 75’s APU was started while still connected to an external power cart, saving wear and tear on the lead acid battery. Once the APU was on line the external cart was disconnected. Both engines were started with the APU powering the starter generators. The engine start governed by the DEEC was a simple “initiate-and-monitor†affair. After setting the flaps to “8†and the completion of the post start checks, a slight power advance was needed to start the 75 rolling. The pedal-controlled electric nose wheel steering offered +/-70˚ of movement, and allowed for precise tracking of taxiway centerlines. One unique feature of the NWS system is the ability to exceed 70˚ of deflection. A large, sharp pedal input will swivel the nose wheel past 70˚ and allow for a very tight turn radius – especially handy in confined ramp spaces. During the short taxi to Wichita airport’s runway 19R for departure I monitored our progress on the airfield diagram of Garmin’s SafeTaxi display – a feature becoming quite common on new aircraft, which can only enhance safety. Once aligned on the runway and cleared for take-off, I advanced the throttles from IDLE to the “TO†take-off detent. As we accelerated down the runway the DEEC set N1 to 93.9%. Takeoff V-speeds were displayed on the primary flight display’s airspeed tape, allowing me to cross-check Eastburn’s callouts. Yoke forces during rotation were moderate, with pitch force changes encountered during acceleration and clean up easily nulled with pitch trim. An initial climb speed of 250KIAS was captured and held, and we turned to the west for our transit to the working area. Once headed west I engaged the autopilot in the HDG (heading) and VS (vertical speed) modes. With the throttles in the MCT detent, the DEECs kept the engines at the desired maximum climb power setting. Passing 32,400ft pressure altitude, a climb speed of Mach 0.70 was captured and held with the autopilot in the FLC (flight level change) mode. Time from brake release to level off at Flight level 430 (43,000ft) was less than 17min. At maximum take-off weight of 9,752kg the 75 can climb directly to 45,000ft – 6,000ft below its maximum operating altitude of 51,000ft. Once level I let the 75 accelerate at MCT power. Reaching 221KIAS, about 94% N1 held a high speed cruise of M0.78. Test day conditions were ISA-5˚C, and true airspeed was 444kt (822km/h), with total fuel flow just 1,150PPH. After slowing to 215KIAS, 90.8% N1 held a long range cruise speed of M0.76. A total fuel flow of 1,020PPH gave a true airspeed of 433kt, lending credence to Bombardier’s published maximum range figure of 3,778km. While at altitude and M0.78 I completed several 45˚ to 55˚angle of bank steep turns. At 220KIAS there was no buffet and yoke forces in pitch were linear during the nearly 2g pull. Back in the day, Learjets used to have a reputation for being difficult at altitude. I have only flown Series 40 and 70 Learjets, and it has been my experience that they are very docile at altitude, able to do 2g manoeuvring with no airframe buffet. Time in the preview profile did not allow me to sample the passenger cabin at altitude. I did, however, note that the 75’s 9.9psi delta-p pressurisation system gave a cabin altitude of 6,500ft at 43,000ft. At 51,000ft cabin altitude is a reasonable 8,000ft. After completion of the high altitude events we started a descent to Hutchinson, Kansas, for a GPS approach. I started the aircraft down using the vertical speed mode of the autopilot. Once established in the descent Eastburn guided me through engaging the VNAV descent mode. With the G5000 a VNAV descent is computed as either an angle or rate of descent. The default setting is a 3˚ angle of descent. Once engaged, it computed a straight-line descent path to our target altitude of 3,200ft MSL at ZENOS – a point on the RNAV GPS 13 localizer performance with vertical guidance (LPV) approach at Hutchinson. With no auto-throttle it is up to the pilot to maintain the desired descent airspeed. One shortcoming with the VNAV profile is that it does not account for a speed reduction (and linear distance) if needed at the transition Level. I kept the autopilot coupled for the approach, watching it accomplish the procedure turn entry and course reversal to final. Having one’s “own-ship†position presented on the ChartView display definitely increased my situational awareness during the approach. From the pilot’s perspective on final a LPV approach is flown much like a full instrument landing system. Once fully configured I needed only to monitor the autopilot’s performance and keep the aircraft at the target speed of 115KIAS. At minimums Eastburn called for a go around. I disconnected the autopilot and hand-flew the missed approach. Once cleaned up we turned to the southeast for our transit to Wichita. En route to Wichita I was able to further familiarise myself with the VFD’s capabilities. With the primary flight display in full-screen mode I really appreciated the full-span horizon, as well as large altitude and airspeed tape displays. As on my prior flight, I liked the flexibility inherent in the multi-pane capability of the displays. Typical divisions used were 60/40 and 20/40/40. With so much screen space available, display configurations can be fine-tuned to meet the needs of even the most demanding aviators. The VFD comes standard with Garmin’s synthetic vision system. Presented on the PFD it helps enhance situational awareness, but on radar vectors over the flatlands of Kansas it was hard to fully appreciate its potential. Once in the traffic pattern at Wichita several visual circuits were flown prior to our full-stop landing. During these approaches I found the 75 a joy to fly, capping what had been a thoroughly enjoyable preview flight. In October Learjet celebrates its 50th year. While slightly more expensive than the $13.1 million Citation XLS+, the 75 offers comparable cabin space in a more comfortable double-club seating configuration. Once off the runway, where the XLS+ has the clear advantage, the Learjet 75 can go over 200km further (LRC speed, four passengers, NBAA IFR reserves). Not only can the Learjet 75 out-distance the XLS+, it does so while cruising over 80kt faster. On arrival, the Learjet 75’s powerful carbonfibre brakes allow it to get into shorter runways than the slower XLS+. Both Cessna and Learjet build world-class aircraft with loyal customer bases, but for those with a need for speed, the new Learjet 75 may well be the super-light business jet of choice. (c) 2013 Reed Business Information - UK. All Rights Reserved. [ Back To TMCnet.com's Homepage ]