Embraer’s new Praetor business jets were unveiled at the NBAA convention in October, and both will enter service next year. Embraer Executive Jets redesigned the Legacy 450 and 500 fly-by-wire business jets, adding two new models—the Praetor 500 and 600—with new performance capabilities. The Praetor 500 and 600 will sit at the top of Embraer’s midsize and super-midsize offerings, but the company said it will still manufacture the Legacy 450 and 500 as long as there are buyers.
Embraer’s Praetor 600 is basically an upgraded version of the Legacy 500, but there are enough changes that make the new model significantly better.
From a handling perspective, the Legacy 500 and 600 fly exactly the same, and this is due to the similarity of the basic design but also a benefit of fly by-wire (FBW) flight controls. Engineers can tune the controls to optimize handling, so the key difference between the two models is performance, especially the Praetor 600’s longer range to 3,900 nm, made possible by added fuel capacity, new winglets, and more powerful engines.
In addition to the Praetor 600’s longer range, Embraer brings to business aviation the world’s first synthetic vision guidance system (SVGS) instrument approaches. Scheduled for FAA approval at entry into service in the second quarter of 2019, SVGS approach capability allows for autopilot-flown ILS approaches to 150 feet height above touchdown, with visibility as low as 1,300 feet RVR. This is an important benefit because the optional E2VS enhanced vision system and HGS-3500 compact head-up display (HUD) by Rockwell Collins isn’t required for SVGS approaches, and it is the first time regulators will grant lower landing minimums credit for a synthetic vision system-equipped airplane. SVGS approach capability will only be available in the U.S. where satellite-based augmentation system capability is available.
I was eager to try out the SVGS approach when I traveled to Brazil in early October for a flight in the then-secret Praetor 600. I have flown the Legacy 450 and 500 a few times and greatly enjoy their handling. The same was true of the Praetor 600.
Embraer’s FBW designs are of the flight path-stable variety, a trait they share with Falcon and Airbus jets. Compared to pitch- or trim-stable FBW designs (Boeing and Gulfstream), Embraer’s path-stable FBW allows the pilot to use the sidestick to select a flight path. The trim-stable FBW replicates traditional flight controls, and pilots fly the airplane exactly as they would with mechanical or hydraulic controls, continually manipulating the yoke or stick to achieve the desired performance, using trim to hold a particular attitude. In the Legacy FBW models, once the pilot sets the desired flight path, whether in pitch or bank (within certain limits), the pilot can release the sidestick and the FBW maintains that flight path with no further manipulation of the controls. There is no need for the pilot to trim.
The Embraer FBW has two flight envelopes, normal and limit. In the normal mode, the stick moves relatively easily (although it is spring-loaded to add some feel) 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 doing so requires some pressure on the sidestick. The FBW system also automatically trims and compensates for pitch and yaw during turns and for roll during sideslips.
There is a lot more to the FBW system to help make flying easier for the pilot. For example, at 65 knots on takeoff, the FBW switches to takeoff law. This gives the pilot pitch-rate control with pitch damping, which helps the pilot stop at the desired pitch attitude after rotation. 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.
When flying the Embraer FBW Legacys, I have found them easy to adapt to and quick to respond to my commands. Unfortunately for trying out the SVGS approach, the weather at Embraer’s headquarters airport in San José dos Campos was perfect, with clear skies and almost zero wind. The Praetor 600 I was flying, with test pilot Sydney Rodrigues in the right seat and chief test pilot Eduardo Camelier in the jumpseat, was still in experimental configuration with test equipment in the cabin, but the flight deck was the production configuration.
After starting the Praetor 600’s Honeywell HTF7500E turbofans, I taxied to Runway 15. The steer-by-wire nosewheel steering is controlled by the rudder pedals and allows up to 62 deg of turn below 10 knots, reducing as speed increases. The Praetor is easy to taxi smoothly without any steering jerkiness.
The takeoff weight was 17,355 kg (38,261 pounds; this airplane is set up with metric weights, probably because it is slated for a European customer). Onboard were four people, myself, Rodrigues, Camelier, and flight test engineer Leandro Souto. Maximum takeoff weight is 19,440 kg (42,858 pounds), roughly 5,000 pounds more than the Legacy 500. We carried about 14,530 pounds of fuel, nearly 1,500 pounds below the maximum 15,986 pounds. Both fuselage tanks were full and the wings nearly full.
With flaps 1 set, the Pro Line Fusion avionics calculated our V1 at 124 knots, rotation speed 128 knots, and V2 at 134 knots.
Rodrigues plugged in a flight plan to a point south of San José dos Campos over the ocean, with a climb to 30,000 feet.
During takeoff, I had to remind myself to put my right hand on my right knee after reaching V1. The Rockwell Collins autothrottles smoothly brought the power up and the more powerful HTF7500Es accelerated rapidly and gave the Praetor a firm push. At rotation speed, just a small movement aft on the sidestick produced the right amount of nose-up attitude, and quickly the FBW system reverted to normal mode. I set the desired flight path, then rested my fingertips on the sidestick.
We headed south over Ihlabela (“beautiful island”) and climbed quickly to FL300, in Embraer’s Bandeirante and Bandeirante Uno flight test areas.
AVIONICS AND HANDLING
We wanted to test the Rockwell Collins MultiScan radar and view its vertical weather profile and predictive windshear capabilities, but there was no weather within hundreds of miles.
Rodrigues dialed up the Praetor’s new ADS-B In cockpit display of traffic information (CDTI) on the MFD. CDTI displays traffic somewhat like what is available with an ADS-B In receiver, and it does use ADS-B In technology along with TCAS. We could see traffic on the MFD and click on individual targets to view a data block with identity, altitude, and velocity information.
Pro Line Fusion, although not the touchscreen variety, is relatively simple for pilots used to mousing around with a cursor control device and modern graphical flight planning. Four 15-inch displays provide plenty of glass real estate that pilots can customize with systems synoptics, charts, checklists, and more. The FMSs are WAAS/LPV units with optional RNP AR 0.3 accuracy and FANS 1/A datalink.
While descending to FL250, I lowered the nose and advanced the power levers to pick up speed and watched the automatic envelope protection system pull up the nose to keep the Praetor 600 from overspeeding. At the other end of the spectrum, I pulled the power back and deployed the spoilers to slow down and allowed the airspeed to drop. As the speed slowed below 160 kias, the spoilers automatically retracted. Then, while holding the stick aft into the limit envelope, at 1.08 of stall speed the protection kicked in and lowered the nose to keep the Praetor from stalling.
I brought the power up to the takeoff setting, then pulled one engine back to idle and kept my feet flat on the floor, watching as the asymmetric thrust compensation helped keep the Praetor tracking straight. It’s important to stay in the loop in a one-engine-out situation, and to help with this, the pilot must apply a small amount of rudder to fully compensate for the failed engine. I also did an engine swap, moving one throttle rapidly from idle to full power, and then the other throttle to idle, and the FBW easily maintained heading with no wing rocking.
With power back to normal, I flew some turns to evaluate flying qualities.
In turns up to 33 degrees of bank, the FBW automatically compensates for the loss of lift, and there is no need to pitch up to keep the nose from dropping. Once the bank angle is set, the jet will simply circle happily by itself, with no need to touch the sidestick.
But when I steepened the bank beyond 33 degrees, I could feel pressure on the sidestick, encouraging me to return to a lower bank angle, and I also had to pull back to compensate for the loss of lift. When I let go of the stick, the bank angle returned to 33.
Our next demonstration was the effect of different attitudes on how fuel flows between the fuselage ventral and forward tanks and the wings. The Praetors use bleed air to pressurize the tanks and meet new fuel tank flammability regulations. At angles of attack of fewer than 6 degrees, bleed air pressure forces fuel from the forward tank to the wings. Once the forward tank is empty, the ventral tank is tapped, again moving fuel to the wings. This scheme biases the in-flight weight-and-balance towards aft CG, which is more efficient for cruise flight (because it lowers the load on the horizontal stabilizer).
If bleed air fails, then auxiliary fuel pumps switch on automatically to effect the fuel transfer. Above six degrees and below minus-two degrees angle-of-attack, the transfer from the fuselage tanks stops, then resumes when the angle falls within those parameters. The aux pumps can be switched on manually if for some reason they don’t do so automatically.
We pulled up the fuel system synoptic on the MFD and watched the fuel system automatically switching to the wing tanks as I moved the sidestick aft to increase the angle-of-attack above the trigger point of 6 degrees.
It was time to return to San José dos Campos for the SVGS approach.
We dialed up the ILS Runway 15 approach with SVGS in the Pro Line Fusion avionics and set the radar altimeter minimums to 150 feet while flying toward the UGTEV waypoint then the LONES initial approach fix.
The SVGS procedures call for flying on autopilot until reaching the 150-foot decision height, and I wanted to experience the entire procedure, so I kept the autopilot engaged. The flight mode annunciator indicated that we selected and were flying the SVGS approach.
As we neared LONES, Rodrigues started adding flaps while I slowed to 160 kias. The autopilot lined us up with the localizer, then Rodrigues lowered the landing gear as we smoothly intercepted the 3-degree glideslope over the final approach fix. I kept my view looking at the PFD inside the flight deck to simulate flying the approach in poor weather. For a real SVGS approach, it must be displayed on both PFDs, otherwise the approach must be abandoned. SVGS approaches will also be eligible to be flown using the head-up display.
The autothrottles and autopilot nailed the approach much more accurately than I would have flying manually, and when I clicked off the autopilot at 150 feet above the ground, I looked outside.
While it seems like 150 feet is fairly close to the ground to be transitioning from autopilot to hand flying, I found the move natural and smooth. The airplane is, after all, perfectly set up on speed with the correct attitude, and all I had to do was continue pointing the nose at the touchdown point, make sure the power levers were at idle, then flare a tiny bit. While looking at the PFD, I was already seeing a view of the outside world on the synthetic vision display, so the transition to the outside world isn’t a big leap.
As the main wheels touched, I held the sidestick neutral and the FBW automatically lowered the nose at a smooth minus-two-degree pitch rate.
Rodrigues reset the flaps for takeoff, then I pushed the power levers forward until the autothrottles engaged, then accelerated and lifted off. We climbed in a left traffic pattern, and this time we set the autobrakes on the high setting so I could experience a maximum performance braking procedure.
Hand-flying the FBW Embraers is a delight, and it was easy to maneuver the Praetor 600 around at low altitude. I pulled the power back quickly after takeoff to keep from blasting through the pattern altitude.
I had to extend the downwind to allow for another airplane to land, then turned base and final, letting the autothrottles help manage power and keep me on speed. Lined up with the runway, I aimed the flight path vector on the PFD at the touchdown point and now in pitch-rate control law (the FBW system’s default configuration during takeoff and landing), reset the trim point with the TCS button on the sidestick.
Again I added just a tiny bit of nose up with the sidestick as the Praetor 600 neared the runway while the throttles moved to idle. As soon as the main landing gear rolled onto the runway, I pushed the sidestick full forward—the FBW commands the maximum nose-down pitch rate without damaging the nose gear—and the nose wheel dropped quickly onto the runway. The autobrakes activate one second after the main wheels touch, even if the nose wheel is still in the air. But at the high setting, the autobrakes allow only low brake pressure until the nosewheel is on the ground, then kick in full pressure.
This all happened much faster than describing how it works, and the Praetor 600 came to an incredibly quick stop. I disengaged the autobrakes by stepping on the brake pedals, then taxied back to the Embraer ramp.
WHAT IS A PRAETOR?
Praetor, from the title for Roman magistrates in the government hierarchy or from the word Praetorian, derives from the verb praeire, which means “to go before, to precede, to lead the way.”
“Praetor was no-brainer,” said Embraer design chief Jay Beever, “[being] the ultimate magistrate, the butler, the servant to the emperor, and capable to fulfill the needs of the emperor.”
The Praetor 600 steps up the capabilities of the Legacy 500 with new winglets, additional fuel capacity, a new software load for the Rockwell Collins Pro Line Fusion avionics as well as a new MultiScan radar, and more powerful Honeywell HTF7500E engines. The Praetor 500 is the newer version of the Legacy 450, with the new winglets and the fuel capacity of the Legacy 500 along with the new avionics capabilities.
Fuel capacity of the Praetor 500 is 13,058 pounds, up from 12,108 in the original Legacy. Both the Legacy 450 and 500 share the same wing design, so this wasn’t a huge change.
The only way to tell the Legacy 450 and Praetor 500 apart visually is by comparing winglets, which are canted out further on the new designs, adding 50 inches in wingspan and 22 inches in wingtip height. The winglets bolt on now, which makes replacement in case of damage much easier.
Embraer engineers were able to avoid structural changes in the wings for the new winglets because they were able to accommodate changes in loads on the wing by modifying the fly-by-wire software to alleviate loads in all configurations and conditions.
The Praetor 500 and 600 models are upgraded versions of the Legacy 450 and 500 (both of which remain in production), and the main difference is the new models’ greater range. The Praetor 500 now offers coast-to-coast range at 3,250 nm (long-range cruise, four passengers, two crew, NBAA IFR reserves), up from the Legacy 450’s 2,900 nm. Takeoff distance is longer, however, at 4,263 feet. Maximum payload is 2,921 pounds, and payload with maximum fuel 1,600 pounds.
The Praetor 600’s range is 3,900 nm with four passengers, two crew, and NBAA IFR reserves. Maximum payload is now 4,001 pounds and payload with maximum fuel 2,533 pounds. Making the improved performance possible are the more powerful engines and a fuel capacity increase to 15,986 pounds. This includes 13,058 in the wing and 2,928 pounds split between two fuselage underbelly tanks; a forward tank and what Embraer labels its “ventral” tank farther aft.
Another difference between the Legacy 500 and Praetor 600, in addition to the winglets, is a longer belly fairing that covers more of the underside of the fuselage, toward the nose of the airplane. A new belly skid is fairly prominent, mounted on the lower aft fuselage to protect the underbelly tanks in case of a gear-up landing.
Both the Praetor 500 and 600 fuel systems are pressurized with engine bleed air to meet FAA fuel tank flammability requirements.
The Praetor 500’s Honeywell HTF7500E turbofans are unchanged, but a software update to the Praetor 600’s engines (same model number) boosts maximum thrust to 7,528 pounds, flat-rated to ISA +18 deg C, up from 7,036 pounds in the Legacy 500.
BOSSA NOVA STYLE
Jay Beever and his design team focused on a complete restyling of the Praetor 500 and 600 interior, called “Bossa Nova” and incorporating not only new designs but also the philosophy of technology disappearing when it isn’t needed. “Bossa Nova,” Beever said, “is a sound with a fingerprint of the people of Brazil, a purpose, a desire, a passion. It also means a new trend, a new wave.”
In application, this translates, he said, into a “stylish, sophisticated, well-crafted interior that treats the owner to a love of details.” The idea is to mirror styles such as the complications that adorn high-end watches or the intricate design features on expensive automobiles, but not to leave the underlying technology exposed.
The Praetor cabin’s upper tech panel is adapted from the Phenom 300, with passive electronic switches that appear when needed and disappear, leaving a clean-looking surface.
Other Bossa Nova features include a reinvented diamond stitching on the seats, which mimics the design of the walkways on the beachfront promenade in Rio de Janeiro.
A carbon-fiber finish on tables wraps around corners without showing the structure of the material. The dark, thin, three-ply material looks homogenous, with the weave perfectly aligned. “The beauty of the carbon-fiber is that its strength comes from the shape change,” he said. “It’s more than an application, it’s structural.” Jet-black metal plating complements the carbon-fiber finish in areas where the materials meet.
The optional three-seat divan features what Beever said “is a perfect 105-degree seating angle. Most divans are like a park bench, with straight-up backs. Nobody wants to sit in it. You need to machine the arc of the tracks so it can go flat, but not when upright.” Tuxedo stitching in a racetrack pattern on the divan reveals the intricate detail employed by the Embraer craftspeople.
To add to the attention to fit and finish, the interior is maintenance-friendly and designed for quick removal and installation without putting components at risk of damage.
CMS AND AVIONICS
The cabin-management system in the Praetors is Honeywell’s Ovation select. Gogo Vision will be an option when the Gogo Avance L5 air-to-ground connectivity system is installed. All of the models offer a new global airborne connectivity option with the Viasat Ka-band satcom and IPTV. The satcom will cost $395,000 and will be available in second-quarter 2019. Retrofits will be available for existing Legacy 450s and 500s.
The Praetors come with a new software load for the Rockwell Collins Pro Line Fusion avionics. A new RTA-4218 MultiScan radar adds vertical weather, predictive windshear, and ground-clutter suppression.
Future capabilities are enabled by the new cockpit display of traffic information (CDTI), which displays TCAS and ADS-B In traffic. Eventually this will allow for reduced separation in busy traffic areas.
The most significant avionics addition is the synthetic vision guidance system (SVGS), which will be approved for a 50-foot reduction in Cat I ILS minimums to 150 feet and lower visibility minimums without requiring a head-up display or special training. Embraer’s Rockwell Collins-based E2VS enhanced vision system and HGS-3500 head-up display, which can display both EVS and synthetic vision system imagery, is an option for the Praetor 500 and 600, as it was for the Legacy 450 and 500. In an effort to encourage adoption of E2VS, the SVGS option will be included free for buyers who select the enhanced vision system and HGS-3500.
An optional Honeywell Laseref VI inertial reference system is available, providing improvements in navigation in remote areas and other benefits for GPS and other nav source outages.
The Praetor 500 baseline price is $16.995 million and it will enter service in the third quarter of 2019.
The $20.995 million Praetor 600 will enter service in the second quarter of 2019.
Fonte: AINonline by editor-in-chief Matt Thurber