JammedStab
30th May 2016, 05:20
From Aviation Week. Not sure if I am really allowed to post their articles but I will try to make them happy by saying that the subscription is worth it.
"Designing, building and ground testing the world’s largest turbofan may seem challenging enough, but how do you safely put such a behemoth through the rigors of flight testing on the wing of an aircraft for which it was not designed?
That is the key question General Electric and Boeing engineers face as they wrestle with the mechanics of flying the GE9X engine for the 777X on GE’s 747-400 flying testbed in 2017. Although rated at 105,000 lb. thrust, or around 10,000 lb. less than the GE90-115B, so far the world’s largest engine, the drive for efficiency and higher bypass ratios means the GE9X is physically much larger.
With a bypass ratio of 10:1 and fan diameter set at an unprecedented 134 in., the overall size of the GE9X nacelle has grown to 178 in. To put this in perspective, the installed GE9X will be just 8 in. narrower than the cabin cross-section of a Boeing 767 and 30 in. wider than the full fuselage cross-section of the 737. The GE90-115B, which has a fan diameter of 128 in., was the previous record-holder, with an external nacelle diameter of 134 in. at its widest point. GE had its hands full testing this very large engine in the 2000s before entry into service of the 777-200LR/-300ER but is now building on lessons learned to ready the GE9X.
“This will be the flagship engine for GE and the flagship aircraft for Boeing,” says Steven Crane, chief test pilot of GE’s Flight Test Operation. “The Boeing team is working hand in hand with GE Flight Test Ops to prepare for flight tests in 2017, and Boeing is designing the strut adaptor,” he adds. The adaptor, like everything else about the GE9X, is vast and will measure nearly 19 ft. in length. To provide adequate ground clearance, the engine will be cantilevered up and forward with a slightly larger tilt angle of 2 deg. more than previous test engines and 5 deg. more than the testbed’s three standard CF6-80C2s.
“We started working with Boeing at least a couple of years ago on this to make sure it will fit OK,” says Crane. “It will not fit under the 747-100 ‘Classic,’ it will only fit under the -400,” he adds. The main gear struts on the -400 are slightly larger than the -100’s while the tires are also bigger. “Having adequate ground clearance is a concern not so much for takeoff and landing as it is for ground operations.” Although the bottom of the nacelle will be only around 1.5 ft. above the ground, issues such as cross-wind landings are not expected to pose any greater challenge than they did when the GE90 was tested, largely because the wing itself bows upward.
The internal wing structure was strengthened with the GE9X in mind when the 747-400 was modified for the test role starting in 2014. The aircraft, a former Japan Airlines -400, was acquired by GE in 2010 and—following maintenance and interior modification in Xiamen, China, by Taikoo Aircraft Engineering—was delivered to Evergreen Aviation Technologies in Taiwan for installation of data racks and instrumentation.
Further modifications are also planned to reduce the chances of aeroelastic interaction between the extended wing of the 747-400 and the GE9X mounted on the inboard left strut. GE has already removed the standard winglets because these add unnecessary weight and a maintenance burden to the aircraft’s flight-test role. Later this year, the outer 6 ft. of each wingtip also will be removed, reducing the overall span to the 195-ft., 8-in. of the 747 Classic and effectively converting the aircraft into a -400D “domestic” variant. The -400D was a specially beefed-up variant of the -400 developed for the Japanese short-range market and did not feature the extended wingtips and winglets of the standard -400. Designers say the stiffer wing will reduce potential exposure to limit cycle oscillation and maintain an unrestricted test envelope.
To dissipate the excess electricity generated by the GE9X during flight testing, the 747-400 will also be fitted with the extra-large load bank developed for testing the GEnx-1B on the 747-100. The belly-mounted device, which will be transferred to the -400 when the -100 is retired later this year, absorbs the energy generated by the engine that would normally be used by systems on board the 777X, and converts it into heat, which is then vented to the atmosphere.
To help the flight crew precisely control the engine as well as place the aircraft in exactly the right condition for each test, the -400 flight deck is also modified with special displays and switches. Designed by former GE chief test pilot Tom Drechsler and Crane, a flip-down display for each pilot shows engine test parameters, live exterior camera images and other key data, and when not in use it stows away beneath the glareshield. “It has all the things we want as one source for test pilots such as N1K and N2K (corrected low- and high-pressure spool speed). It is a high-definition screen and a repeater of the data and video systems downstairs (on the main deck). It doesn’t interfere with flight controls, and it also allows us to see the navigation display for good situational awareness,” says Crane.
The screens, which can also be controlled by hand-held tablets used by the test crew, are a valuable test aid in an aircraft that is already a big step ahead of the venerable -100 it is succeeding, says Crane. “All is now within [the pilot’s] field of view, as opposed to the Classic, where everything was spread out around the cockpit. The aircraft is so much nicer to fly, and the autopilot on the -400 is light years ahead of the Classic. So that’s much better for performance and operability testing. We can also see what channel of the full authority digital engine control we are operating on, A or B,” he adds.
“We also integrated the switches on the overhead panel with the test engine so we can communicate with and control the engine auxiliary systems through the 747 controls,” says Crane. “The only thing we added was a high-pressure shut-off valve that allows us to shut down the engine if there is a problem and [enables] some kinds of tests. There is also a fuel panel that repeats the functionality of the standard fuel panel. This enables me to control fuel from any tank I want on the aircraft.” Fuel control is important, says Crane, because “burn rates may not be the same, and with a large engine like the GE9X we may want to carry fuel as ballast. This allows us to interrupt the automatic fuel transfer functions, and, although that functionality always existed, we are just miniaturizing it so it can be on the center console.”
The display shows imagery from a suite of surveillance video cameras. “We can pull up video to see when we are being pushed and make sure no one is in harm’s way, or we can look at the engine itself either from over the wing or from an ‘R2D2’ unit under the belly. We can steer it and zoom in if we want to look at something on the engine,” Crane says.
As preparations for flight testing get underway, ground runs of the initial engine have already begun. Fired up into life for the first time three days ahead of schedule on March 25 at the company’s Peebles, Ohio, facility, the engine has powered up to its full 105,000-lb. rated thrust level and is “running beautifully,” says GE90/GE9X general manager Bill Millhaem.
With lessons of past programs in mind, such as the troublesome original GE90 development effort, GE is trying something new by running the first GE9X much earlier in the program than normal for a new centerline engine. “We pulled the engine way forward in the test plan and, in fact, we ran six months after Toll Gate 6 [freezing design and launch of detailed design phase]. The second engine is scheduled to run about a year later, so any lessons learned from the first engine will be incorporated into the second in time for the certification program,” Millhaem says.
The first engine is “near the final standard,” he adds, and it paves the way for a stable configuration heading into certification. As the physical hardware is not expected to change, the focus for any adjustments that might emerge from the testing is on fine-tuning aerodynamic performance of blades and vanes, secondary flows, temperatures and pressures. Results from the ground-test phase, which will run through the summer, will inform the next Toll Gate 7 milestone, which covers finalizing the detailed design; this is expected around September.
GE is focusing early on the operating conditions of the many new design features incorporated into the GE9X, in particular the engine’s 27:1 pressure ratio high-pressure (HP) compressor and its downstream turbine section. “We are interested in the temperature in the back of the HP turbine and compressor and the underlying second-stage cooling circuits,” Millhaem says.
“We also want to understand performance in the harsh environments of the world,” says Millhaem, who adds that future work includes deliberate ingestion of dust as part of endurance and demonstration tests of the parts made from ceramic matrix composites (CMC). The lightweight material is used in the combustor liners as well as the stage 1 shrouds of the HP turbine and stage 1 and 2 nozzles. A dust rig in front of the engine will help simulate desert operations and “validate how the CMC hardware behaves,” he adds. Barrels of different types of dust have been collected from all parts of the world. “We have discovered that not all dust is created equal and that ingesting it into the engine is an art. It’s hard to believe, but getting the right size and concentration is something we are working hard on.”
The flight-test engine, one of eight GE9X units planned for the certification program, also will be ground tested prior to flight to validate the control logic. Engine certification is planned for the fourth quarter of 2018."
https://www.google.com.tw/search?biw=1366&bih=628&tbm=isch&sa=1&q=747+ge+90+testbed+flight+test&oq=747+ge+90+testbed+flight+test&gs_l=img.3...88708.91033.0.91419.12.12.0.0.0.0.65.529.12.12. 0....0...1c.1.64.img..0.0.0.14aByaDQAEg#imgrc=8qo4vwvYjUFNjM %3A
"Designing, building and ground testing the world’s largest turbofan may seem challenging enough, but how do you safely put such a behemoth through the rigors of flight testing on the wing of an aircraft for which it was not designed?
That is the key question General Electric and Boeing engineers face as they wrestle with the mechanics of flying the GE9X engine for the 777X on GE’s 747-400 flying testbed in 2017. Although rated at 105,000 lb. thrust, or around 10,000 lb. less than the GE90-115B, so far the world’s largest engine, the drive for efficiency and higher bypass ratios means the GE9X is physically much larger.
With a bypass ratio of 10:1 and fan diameter set at an unprecedented 134 in., the overall size of the GE9X nacelle has grown to 178 in. To put this in perspective, the installed GE9X will be just 8 in. narrower than the cabin cross-section of a Boeing 767 and 30 in. wider than the full fuselage cross-section of the 737. The GE90-115B, which has a fan diameter of 128 in., was the previous record-holder, with an external nacelle diameter of 134 in. at its widest point. GE had its hands full testing this very large engine in the 2000s before entry into service of the 777-200LR/-300ER but is now building on lessons learned to ready the GE9X.
“This will be the flagship engine for GE and the flagship aircraft for Boeing,” says Steven Crane, chief test pilot of GE’s Flight Test Operation. “The Boeing team is working hand in hand with GE Flight Test Ops to prepare for flight tests in 2017, and Boeing is designing the strut adaptor,” he adds. The adaptor, like everything else about the GE9X, is vast and will measure nearly 19 ft. in length. To provide adequate ground clearance, the engine will be cantilevered up and forward with a slightly larger tilt angle of 2 deg. more than previous test engines and 5 deg. more than the testbed’s three standard CF6-80C2s.
“We started working with Boeing at least a couple of years ago on this to make sure it will fit OK,” says Crane. “It will not fit under the 747-100 ‘Classic,’ it will only fit under the -400,” he adds. The main gear struts on the -400 are slightly larger than the -100’s while the tires are also bigger. “Having adequate ground clearance is a concern not so much for takeoff and landing as it is for ground operations.” Although the bottom of the nacelle will be only around 1.5 ft. above the ground, issues such as cross-wind landings are not expected to pose any greater challenge than they did when the GE90 was tested, largely because the wing itself bows upward.
The internal wing structure was strengthened with the GE9X in mind when the 747-400 was modified for the test role starting in 2014. The aircraft, a former Japan Airlines -400, was acquired by GE in 2010 and—following maintenance and interior modification in Xiamen, China, by Taikoo Aircraft Engineering—was delivered to Evergreen Aviation Technologies in Taiwan for installation of data racks and instrumentation.
Further modifications are also planned to reduce the chances of aeroelastic interaction between the extended wing of the 747-400 and the GE9X mounted on the inboard left strut. GE has already removed the standard winglets because these add unnecessary weight and a maintenance burden to the aircraft’s flight-test role. Later this year, the outer 6 ft. of each wingtip also will be removed, reducing the overall span to the 195-ft., 8-in. of the 747 Classic and effectively converting the aircraft into a -400D “domestic” variant. The -400D was a specially beefed-up variant of the -400 developed for the Japanese short-range market and did not feature the extended wingtips and winglets of the standard -400. Designers say the stiffer wing will reduce potential exposure to limit cycle oscillation and maintain an unrestricted test envelope.
To dissipate the excess electricity generated by the GE9X during flight testing, the 747-400 will also be fitted with the extra-large load bank developed for testing the GEnx-1B on the 747-100. The belly-mounted device, which will be transferred to the -400 when the -100 is retired later this year, absorbs the energy generated by the engine that would normally be used by systems on board the 777X, and converts it into heat, which is then vented to the atmosphere.
To help the flight crew precisely control the engine as well as place the aircraft in exactly the right condition for each test, the -400 flight deck is also modified with special displays and switches. Designed by former GE chief test pilot Tom Drechsler and Crane, a flip-down display for each pilot shows engine test parameters, live exterior camera images and other key data, and when not in use it stows away beneath the glareshield. “It has all the things we want as one source for test pilots such as N1K and N2K (corrected low- and high-pressure spool speed). It is a high-definition screen and a repeater of the data and video systems downstairs (on the main deck). It doesn’t interfere with flight controls, and it also allows us to see the navigation display for good situational awareness,” says Crane.
The screens, which can also be controlled by hand-held tablets used by the test crew, are a valuable test aid in an aircraft that is already a big step ahead of the venerable -100 it is succeeding, says Crane. “All is now within [the pilot’s] field of view, as opposed to the Classic, where everything was spread out around the cockpit. The aircraft is so much nicer to fly, and the autopilot on the -400 is light years ahead of the Classic. So that’s much better for performance and operability testing. We can also see what channel of the full authority digital engine control we are operating on, A or B,” he adds.
“We also integrated the switches on the overhead panel with the test engine so we can communicate with and control the engine auxiliary systems through the 747 controls,” says Crane. “The only thing we added was a high-pressure shut-off valve that allows us to shut down the engine if there is a problem and [enables] some kinds of tests. There is also a fuel panel that repeats the functionality of the standard fuel panel. This enables me to control fuel from any tank I want on the aircraft.” Fuel control is important, says Crane, because “burn rates may not be the same, and with a large engine like the GE9X we may want to carry fuel as ballast. This allows us to interrupt the automatic fuel transfer functions, and, although that functionality always existed, we are just miniaturizing it so it can be on the center console.”
The display shows imagery from a suite of surveillance video cameras. “We can pull up video to see when we are being pushed and make sure no one is in harm’s way, or we can look at the engine itself either from over the wing or from an ‘R2D2’ unit under the belly. We can steer it and zoom in if we want to look at something on the engine,” Crane says.
As preparations for flight testing get underway, ground runs of the initial engine have already begun. Fired up into life for the first time three days ahead of schedule on March 25 at the company’s Peebles, Ohio, facility, the engine has powered up to its full 105,000-lb. rated thrust level and is “running beautifully,” says GE90/GE9X general manager Bill Millhaem.
With lessons of past programs in mind, such as the troublesome original GE90 development effort, GE is trying something new by running the first GE9X much earlier in the program than normal for a new centerline engine. “We pulled the engine way forward in the test plan and, in fact, we ran six months after Toll Gate 6 [freezing design and launch of detailed design phase]. The second engine is scheduled to run about a year later, so any lessons learned from the first engine will be incorporated into the second in time for the certification program,” Millhaem says.
The first engine is “near the final standard,” he adds, and it paves the way for a stable configuration heading into certification. As the physical hardware is not expected to change, the focus for any adjustments that might emerge from the testing is on fine-tuning aerodynamic performance of blades and vanes, secondary flows, temperatures and pressures. Results from the ground-test phase, which will run through the summer, will inform the next Toll Gate 7 milestone, which covers finalizing the detailed design; this is expected around September.
GE is focusing early on the operating conditions of the many new design features incorporated into the GE9X, in particular the engine’s 27:1 pressure ratio high-pressure (HP) compressor and its downstream turbine section. “We are interested in the temperature in the back of the HP turbine and compressor and the underlying second-stage cooling circuits,” Millhaem says.
“We also want to understand performance in the harsh environments of the world,” says Millhaem, who adds that future work includes deliberate ingestion of dust as part of endurance and demonstration tests of the parts made from ceramic matrix composites (CMC). The lightweight material is used in the combustor liners as well as the stage 1 shrouds of the HP turbine and stage 1 and 2 nozzles. A dust rig in front of the engine will help simulate desert operations and “validate how the CMC hardware behaves,” he adds. Barrels of different types of dust have been collected from all parts of the world. “We have discovered that not all dust is created equal and that ingesting it into the engine is an art. It’s hard to believe, but getting the right size and concentration is something we are working hard on.”
The flight-test engine, one of eight GE9X units planned for the certification program, also will be ground tested prior to flight to validate the control logic. Engine certification is planned for the fourth quarter of 2018."
https://www.google.com.tw/search?biw=1366&bih=628&tbm=isch&sa=1&q=747+ge+90+testbed+flight+test&oq=747+ge+90+testbed+flight+test&gs_l=img.3...88708.91033.0.91419.12.12.0.0.0.0.65.529.12.12. 0....0...1c.1.64.img..0.0.0.14aByaDQAEg#imgrc=8qo4vwvYjUFNjM %3A