Eight years ago, then-executive vice president of Embraer Executive Jets Luis Carlos Affonso surprised NBAA show attendees by unveiling concepts for two completely new jets, dubbed mid-light and mid-size; a year later these became the Legacy 450 and 500. The new jets not only signaled the company’s efforts to build a larger presence in the business jet market but also a commitment to fly-by-wire flight control technology that is not available in jets in that class.
At the time, it was unlikely that anyone at Embraer knew that Cessna designers would soon begin sketching the design for a flat-floor cabin jet–the Latitude–that would prove to be a direct competitor to the Legacy 450. And the Embraer prognosticators would not learn until years later that one of the competing midsize jets–the Learjet 85–would eventually suffer a program pause that many in the industry believe will never be un-paused.
What Embraer leaders did see was an opportunity to carve out new niches in the market with two business jets that share 95 percent commonality, differing only in cabin length and range, and that have fly-by-wire (FBW) flight controls, the latest Pro Line Fusion avionics from Rockwell Collins, Honeywell Ovation Select cabin management system and Honeywell HTF7500E engines.
The Legacy 500 (officially EMB-550) received Brazilian ANAC certification last August and was certified by the FAA last October and by the EASA in December. The Legacy 450 is slated to enter service by year-end.
At first glance, the Legacy 500 looks large, and in many ways it is. The flat floor, for example, adds a spacious feel to the 826-cu-ft cabin, which is larger than that of the Citation Sovereign+ at 620 cu ft but smaller than the Challenger 300/350 at 860 cu ft and the Gulfstream G280, the largest at 935 cu ft. Of the three competitors, only the Challenger has a flat-floor cabin, and this feature seems to be gaining traction as a popular differentiator. The Challenger and G280 are the only jets with a taller cabin height than the 72 inches of the Legacy 450/500, with the Challenger offering one more inch and the G280 three more inches.
The Legacy 500’s Pro Line Fusion-equipped flight deck is not only roomy but also uncluttered and logically laid out to address sound human-factors principles. Sidestick controls help maximize cockpit space, too: removing the bulky yokes saves space, weight and mechanical complexity and gives free rein to seat designers who no longer have to cut a channel in the front of the seat to accommodate a yoke’s aft movement. The sidesticks also open room for stowable tables in front of each pilot.
Embraer designers elected to eliminate a steering tiller to save space and not interfere with the sidesticks. The nosewheel steering mechanism is electro-hydraulic, but also steer-by-wire, and can swivel 62 degrees either side at slow speeds, narrowing to just 4 degrees at high speeds. Cockpit windows are extra large and provide excellent visibility. The windshields are replaceable from outside the cockpit, so no interior panels need to be removed for windshield replacement, which should save hours of labor.
The 110-cu-ft external baggage compartment is quite high off the ground, but accessible via an optional (but free) ladder that fits neatly into the door. Optional heating is available for the unpressurized baggage compartment. An additional 45 cu ft of baggage space is available inside the cabin, just aft of the lavatory, and this is plenty of space to handle carry-on luggage that passengers might need to access during flight.
Small touches reveal the intent of Embraer designers to lavish attention on the interior and exterior. For example, no lightning diversion strips are visible on the smooth unblemished radome; engineers figured out a way to provide the lightning protection even with the strips embedded in the radome’s composite skin. Inside the cabin, attention to detail is even more pronounced, with F.List granite-veneer flooring in the forward galley area and lavatory, power outlets and tablet or magazine pockets at each seat and a carefully fitted milled end piece where the bulkheads meet the cabin shell and valence, designed to look good no matter how interior components shift around slightly as the fuselage stretches and shrinks during normal operations.
As it is in many modern business jets, the emergency exit is in the lavatory. The interior baggage area aft of the lavatory is flanked by electronics bays that free up space in the forward cabin for more room for the galley and cabinets. Large windows are fitted with mechanical shades, but Embraer plans to offer electronic dimming shades as an option. To prevent freezing of lavatory and galley reservoirs when the aircraft is to be parked in cold climates, the pilot can push a button in the cockpit in flight to pump clean reservoir water overboard.
As it did with the Legacy 650 and Lineage 1000, Embraer selected Honeywell’s Ovation cabin management system for the new Legacys, and it is controllable from passenger control units or iOS and Android devices. Auxiliary panels allow connection of a variety of devices using interfaces such as HDMI, USB, RCA, VGA and 3.5-mm audio. Ovation offers full-HD video and surround-sound audio. Connectivity options include Gogo Business Aviation's air-to-ground broadband Internet system and Cobham SwiftBroadband or ICG Iridium satcom.
Both 17.5- or 19-inch monitors are available for the forward and aft bulkheads, and each seat has a receptacle mount for a nine-inch monitor as well as passenger control units. The forward-facing VIP seat in the first club section has a master control unit that can also adjust cabin temperature and a handset for the ICG Iridium satcom. Seats have footrests and headwings and two seats fold together to make a lie-flat bed.
Embraer put an enormous amount of effort into quieting the new Legacys, both inside and outside the cabin. The Honeywell 36-150 APU is mounted with high-performance isolators to block noise, and the HTF7500E turbofans are also mounted on soft engine mounts for the same purpose. The cockpit profile is aerodynamically smoothed to minimize wind noise and the main landing gear is fully covered, a first for Embraer. External antennas are mounted fore and aft and away from the occupied part of the cabin, also to minimize noise. Mufflers in the environmental control system vent lines help, too, as does an inflatable main door seal. The single air-cycle machine is mounted well away from the cabin, and the pressurization outflow valve is mounted with a noise barrier for maximum quietness. Interior insulation includes skin-damping material, a sound-barrier layer and panel isolators on interior panels and low-noise carpet pad. The hydraulic systems have attenuators and are also soft-mounted. The location of electrical equipment in the bays next to the interior aft baggage area also cuts noise.
The result of all these efforts “sets a new benchmark for cabin noise levels,” according to Alvadi Serpa, who is in charge of product strategy for Embraer Executive Jets. “It’s three to four decibels lower than the Challenger 300,” he said. During the flight in the Legacy 500, I moved to the rear-most seat of the cabin’s aft divan and was able to speak with and hear clearly flight-test engineer Gustavo Paixão, who was sitting in the forward-most, aft-facing club seat.
Standard seating is eight in two double-clubs, with one optional belted lavatory seat. The aft club can be replaced by one or two three-place divans that are approved for takeoff and landing. The forward cabinet across from the galley can be replaced by either a single passenger seat or a fold-up jumpseat, which brings the maximum to 12 seats.
Flying the FBW
Before we flew the Legacy 500, Camelier ran me through the planned flight profile in the flight-test simulator. This proved to be a great introduction to the airplane and the FBW controls and made the following day’s flight much more productive. The simulator uses the same aerodynamic modeling as the airplane and the device is still used for certification and testing, most recently for steep-approach failure modes and failure hazard analysis.
In the simulator I found that it took a little practice to get used to the flight path stable FBW system. With this design, when flying in the normal flight envelope the pilot simply sets the desired flight path with the sidestick then lets the stick return to its spring-loaded neutral position. The flight path will then stick, and subsequent movements of the sidestick simply nudge the Legacy into a different flight path. For a pilot accustomed to maintaining the desired attitude by constantly making tiny yoke movements, adjusting to the Legacy FBW took a little time. Once I got used to it, however, I found that the handling made flying much easier. In any bank in the normal envelope up to 33 degrees, for example, the Legacy motors along without losing altitude and with no need to crank back on the stick to stay level.
We spent some more time in the simulator performing maneuvers that highlighted the Legacy 500’s capabilities, including steep turns, speed brake modulation, overspeed and bank angle protection, steady heading sideslip with full rudder, accelerated high-incidence handling with full aft pitch, simulated engine failure on climb-out and go-around and practice with Embraer’s patented tactile control steering (TCS) trim system, which in landing configuration automatically trims the airplane to match the selected speed, and finally a high-performance landing with maximum braking.
The Real Airplane
When it came time to fly the Legacy 500, Camelier and I were joined by flight-test engineer Paixão and demonstration/instructor pilot Rafael Ricardo. With 7,780 pounds of fuel (about half tanks), two pilots and two crew, the Legacy 500 weighed just over 32,000 pounds at takeoff, well below the 37,919-pound maximum takeoff weight.
The weather at São José dos Campos Airport was VFR with scattered clouds and 21 degrees C, about 10 degrees warmer than ISA. With flaps 1 set, we planned an initial climb directly to FL450. V1 was 112 knots, rotation speed 117 knots and V2 124 knots, as automatically calculated by the Pro Line Fusion avionics once we inserted the weight-and-balance data. The calculated takeoff and landing performance data is not just for advisory purposes, and the Fusion system sends the speeds directly to the PFD. During flight, the weight-and-balance page shows a constantly updated center of gravity as fuel burns off and it will generate an alert if there is an out-of-balance condition. If planning another leg, during flight the crew can plug in what-if numbers to see the cg and any runway limitations.
The Legacy 500 fly-by-wire is a fully closed-loop system and provides envelope-protection features that prevent the pilot from exceeding certain limits. In an open-loop system, a movement of the flight control yoke or stick or rudder pedals always produces the same movement of the flight control surfaces, Camelier explained. In a closed-loop system, the pilot is commanding “a performance that the airplane will give the pilot.” For example, if the pilot pulls the sidestick aft in the Legacy 500, he may be commanding, say, a 1.2-g pullup. The flight control computer looks at the resulting pullup and if it isn’t 1.2 g, the system constantly makes adjustments to the elevators to achieve the commanded 1.2 g. In an open-loop system, the pilot would have to make these corrections constantly. The same is true for banking. “If the pilot gives a half command to the left with flaps up,” he said, “it’s like 15 degrees per second of roll rate. If during that roll for whatever reason the rate starts to increase or decrease, with this constant loop of feedback, the ailerons and roll spoilers will be constantly moving to adjust to 15 degrees per second of roll rate.”
There are two flight envelopes designed into the FBW system, normal and limit. In the normal mode, the stick moves relatively easily until the limits are reached (33 degrees bank, plus 30 and minus 15 degrees pitch), Vmo and 1.13 Vs (stall speed). The pilot can steer outside the normal envelope into the limit envelope, but would need to hold pressure on the sidestick to do so.
The sticks are spring-loaded to provide some control feel, and they always return to the centered position when released. What is key about flying the Legacy 500 is that the FBW system maintains a stable flight path. Whenever the pilot allows the stick to return to neutral, the airplane will remain on whatever flight path was selected. The FBW system also automatically trims and compensates for pitch and yaw during turns and for roll during sideslips.
At 65 knots on takeoff, the FBW switches to takeoff law. According to Camelier, “This is basically a pitch-rate control with pitch damping to help the pilot stop at whatever pitch he wants. For each sidestick movement in the longitudinal axis duration rotation, that pilot is commanding a pitch rate to the airplane. We found this to be the best control law for rotation and for capturing a steady pitch attitude.” About three to five seconds after takeoff, the FBW switches to the normal flight mode (Nz control law) and remains that way until configured for landing. In Nz control law, trimming is always automatic.
After a smooth takeoff aided by the Rockwell Collins autothrottles, we rocketed up to FL450 in just 20 minutes, thanks to our light weight and the powerful 7,036-pound-thrust Honeywell turbofans. I tried some turns and got used to controlling the flight path with the sidestick. We stabilized at Mach .80, burning 350 pounds of fuel per side.
Since I had already flown the simulator, the Legacy 500 felt comfortable almost immediately and I didn’t find that the flight path stable philosophy detracted in any way from the jet’s pleasant handling characteristics. I quickly adapted to a feather-light touch on the sidestick, and that’s all that is needed for most maneuvers.
We descended to a block altitude below 25,000 feet to try some maneuvers and I was able to experience a variety of the Legacy 500’s unique FBW characteristics, including pushing the stick into the limit envelope during steep turns, an approach to stall and recovery, wind-up turns, overspeed protection and flying in direct mode as opposed to normal.
What I found most interesting during this part of the flight was that I was able to rack the Legacy 500’s controls around in a way that would be impossible in a jet with conventional flight controls. Camelier had me set up a 30-degree bank then snap the sidestick fully aft to the stop. The Legacy settled at its maximum angle-of-attack of 4 percent above the stall speed. At higher speeds, around 250 kias, the FBW will allow only a 2.5-g pullup with flaps zero. With any amount of flaps deployed, the load limit is 2.0 g, thus protecting the airframe from excessive loads.
With full flaps and gear down and throttles at idle, I pulled the sidestick all the way back. The Legacy just sat there contentedly showing about 90 knots on the airspeed tape, in low-speed protection mode just 4 percent above stall, and I was still able to make banked turns.
On the other end of the envelope, Camelier put the pedal to the metal to demonstrate the overspeed protection. The airspeed climbed to about 330 kias, just above the 320-knot, Mach 0.83 Vmo/Mmo, and then the overspeed protection kicked in and pulled the nose up to keep the speed from building. I had to push the sidestick forward to stay in that regime, but the FBW wouldn’t let the airplane go faster. Camelier had me bank the airplane while experiencing the overspeed protection, and the Legacy 500 handled that perfectly. In both the stall and overspeed protection modes, the Legacy remains fully maneuverable, and that was one of the design goals.
There are only two modes to the FBW, normal or direct. All flying is done in normal mode, which provides all the protections such as workload reduction with autotrim, path maintenance, engine failure transient reduction, angle-of-attack limiter, overspeed protection and load factor protection. Direct mode gives the pilot full control of the airplane without any envelope protection and should be used only in an emergency.
The Legacy 500 will default to direct mode if both flight-control computers fail or if for some reason the flight-control computers decide that direct mode is necessary. Normally the flight-control computers drive eight remote electronic units, and if both of the flight-control computers fail, the remote electronic units run the direct-mode flight laws themselves and thus take over the switch to direct mode.
The Legacy 500’s yaw damper is always on. Camelier explained: “Even in direct mode we always have yaw damping. We know that business jets normally have Dutch roll issues, and in this airplane we designed the flight control system so that even in the worst case you always have yaw damping.”
Without the normal mode protections, in direct mode the only aid is a stall warning because the pilot can stall the airplane in that mode. In direct mode, Paixão explained, essentially “you have a gain schedule of surface deflection as a function of airspeed.”
Pilots can select direct mode by pushing a button on the console between the seats, and in that case will need to trim the pitch with a rocker switch on the console. This would be the only time that the pitch trim would be used. When pilots activate direct mode–which they should never do, Camelier pointed out–a CAS message stays on and can be removed only as a maintenance action on the ground.
When we tried direct mode, it felt strange to fly the Legacy 500 by commanding the flight control surfaces instead of using the FBW’s normal mode. The Legacy seemed light on the controls in direct mode, but certainly it wouldn’t take long to get comfortable with it. I did some turns, then an approach to stall, and recovered with pitch and power, then returned to normal mode with a push of the button on the console.
We also tested simultaneous movement of the sidesticks, which are not interconnected mechanically or electronically, at least not in such a way that they move together. While the sidesticks operate independently, there are protections for when both pilots actuate the controls at the same time. If both pilots move the stick in the same axis at the same time, the command is summed. But whenever there is a dual input, an aural warning sounds, a CAS message illuminates and both sticks vibrate. One pilot can take over priority by pushing a button on the top right of the stick, and a CAS message shows which stick has priority.
To demonstrate this further, Camelier counted to three and I moved my sidestick full left and he moved his full right. They canceled each other out, and the airplane stayed on its flight path. We also saw the CAS message, heard the audio alert and felt the stick vibration. Then I turned left with a 30-degree bank and he moved his sidestick to the right, so the summation returned the bank to 15 degrees.
The sidesticks have a priority button for locking out the other sidestick. While we were both providing inputs, I pushed my priority button and Camelier flopped his stick around and it did nothing. I held my priority button for 20 seconds, let go, and my sidestick remained the priority. Then hitting either button on the left or right sidestick stops the priority operation.
Approach and Landing
Returning to São José dos Campos, we shot an Rnav approach to Runway 15, landed and then did a touch-and-go. This gave me a good feel for the TCS trim system, which is available in landing configuration. By pressing the TCS trim button on the sidestick, the Legacy 500 automatically retrims for whatever speed is showing on the airspeed tape. A green arrow on the tape shows the newly trimmed speed. What I liked about TCS trim is that I didn’t have to push or pull the sidestick then trim off the pressure; rather, I just pitched to get the desired speed, then pushed the TCS button and all is stable. Camelier pointed out that it’s OK to keep pushing the TCS button as the speed approaches the desired target, and I tried this and liked it.
During the second approach, at 200 feet above the ground we simulated an engine failure, and I was able to experience the FBW system’s ability to apply most of the rudder needed to handle the asymmetric thrust, leaving a bit of rudder for the pilot to keep him in the loop. The idea here is that while Embraer could have designed the FBW to handle the entire asymmetric thrust compensation with no pilot input required, proper human-factors design meant that stepping on the rudder, even just a tiny bit, helps keep the pilot well in the loop on the engine failure.
To help the pilot, the lateral force indicator (triangular sideslip indicator on top of the PFD) turns blue after landing gear retraction with one engine inop. Stepping on the applicable rudder centers the indicator to provide optimum sideslip for a single-engine climb. “Sometimes in a [conventional] airplane you don’t know exactly how much pedal to put in,” he explained, “and you have to leave the sideslip indicator just slightly off. Here we tell the pilot, ‘OK, for the optimum condition, all you have to do is align the triangle.’”
On the final landing, we switched on the autobraking system to medium and landed with full flaps. After touching down on the mainwheels, I pushed the stick forward fairly quickly, and the FBW system automatically–and gently–put the nosewheel on the ground, and the autobrakes kicked in and brought us to a rapid and short stop, aided by the powerful anti-skid carbon brakes.
This is the first real FBW aircraft that I have flown (not a simulator), and I was surprised not only at how easy it flies but how well it handles. I wasn’t sure what to expect, but the Legacy 500 does exactly what the pilot asks for and does so smoothly and effectively. I never felt out of the loop or that the FBW was doing something I didn’t expect. I don’t think it will take pilots long to learn the Legacy 500, and if this flight was any indication they are going to enjoy the process immensely. When transitioning to the Legacy 450, there will be no extra training required as they are both considered the same for type certification training purposes.
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AIN Pilot Report Embraer Legacy 500 (20K)
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July 1, 2015 - 10:17pm
Good information, thank you sir . interesting.