Power troubles hinder Airbus production buildup plan

New hypersonic, unmanned and small-satellite launch projects are included in a DARPA budget request that seeks $3.44 billion for defense advanced research in fiscal 2019, an increase of 8.5% over the previous year.

The request also notes significant changes to the research agency’s existing hypersonics programs as the Pentagon ramps up interest in high-speed weapons.

With $50 million requested in 2019, up from an initial $6 million in 2018, Operational Fires (OpFires) will demonstrate “a ground-launched system enabling hypersonic boost-glide weapons to penetrate modern enemy air defenses and rapidly and precisely engage critical time-sensitive targets,” DARPA says.

The program aims to develop an advanced booster able to deliver different payloads to different ranges and mobile ground launch platforms that can be rapidly deployed and will integrate with existing ground forces. The program is planned to culminate in end-to-end flight tests.

OpFires will leverage the ongoing DARPA/U.S. Air Force Tactical Boost Glide (TBG) program to demonstrate an unpowered hypersonic weapon that can be air-launched from existing platforms.

Lockheed Martin is under contract to conduct the first TBG flight test in fiscal 2019, but the new budget increases funding to $139 million, from $37.6 million in 2018, adds a second contractor and begins development of a variant of the weapon for vertical launch from U.S. Navy warships.

The DARPA/Air Force Hypersonic Air-breathing Weapon Concept (HAWC) air-launched cruise missile also is scheduled to enter flight-testing in fiscal 2019, with both Lockheed and Raytheon under contract to develop demonstrator vehicles.

Funding requested for HAWC by DARPA decreases in 2019, to $14.3 million, but this reflects an increase in Air Force funding, budget documents note. The hydrocarbon-fueled, scramjet-powered missile is a successor to the X-51A hypersonic engine demonstrator flown in 2010-13.

Increased fiscal 2019 funding is sought for the Advanced Full Range Engine program to ground-test a turbine-based combined-cycle propulsion (TBCC) system that could power reusable hypersonic air vehicles from takeoff to beyond Mach 5 and back to a runway landing.

DARPA is seeking $53 million in 2019 as the program moves into ground demonstration of the mode transition between an off-the-shelf turbine engine and a dual-mode ramjet/scramjet. Both Aerojet Rocketdyne (with Lockheed) and Orbital ATK (with Boeing) are under contract to demo TBCC systems.

Aircraft and Vehicle Integrated Team (Aviate) is a new program for 2019 to demonstrate an advanced unmanned aircraft system (UAS) that is an organic extension of tactical ground vehicles, able to autonomously land, attach, stow, detach and take off from the vehicle without exposing the crew.

The agency is requesting $5.9 million in 2019 to begin Aviate, which closely echoes DARPA’s Organic Air Vehicle program of the early 2000s. That program sought to develop a vertical-takeoff-and-landing (VTOL) UAS that was to be an integral part of the Army’s abortive Future Combat Systems family of armored vehicles.

Several of DARPA’s larger unmanned systems programs are set to culminate in 2019. Flight-testing of the Aurora Flight Sciences XV-24A LightningStrike distributed hybrid-electric high-speed VTOL demonstrator is set to begin in fiscal 2019, and the funding sought drops to $4 million from $14.7 million in 2018.

Flight-testing of the Northrop Grumman-developed Tactically Exploited Reconnaissance Node (TERN) ship-based medium-altitude, long-endurance (MALE) VTOL UAS is planned for 2018. TERN is a joint effort with the Office of Naval Research, and the Navy requests funding in 2019 to establish a MALE (TERN) project unit “to further mature and assess the technology . . . in a ship-based environment.”

Responsive Access for Space Resilience (RASR) is a new program for 2019 targeting the launch of satellites weighing less than 660 lb. RASR, also called the DARPA Launch Challenge, will “reward competitors who can demonstrate the ability to launch a payload to orbit with minimal notification time and unknown preconditions regarding the payload configuration, required orbit and launch site.”

The fiscal 2019 budget request continues funding for DARPA’s major responsive space launch program, the Experimental Spaceplane One (XSP). This is an autonomous, reusable, aircraft-like first stage being developed by Boeing as the Phantom Express. The $62 million sought in 2019 is about the same as in 2018 and will begin the integration and test of the XSP flight and ground systems.

If Airbus CEO Tom Enders could have his way, the direction would be clear: Increase single-aisle production to 70 aircraft per month. That is a “no-brainer” to him from a demand point of view. “We could even go higher,” he says.

For the short-term, that is wishful thinking, though. Airbus just halted deliveries of A320neo-family aircraft powered by Pratt & Whitney PW1100G engines after a recent spate of in-service problems. And the alternative supplier, CFM International, is so behind on deliveries that Enders personally brought the matter to the attention of leadership of CFM International joint-venture partners General Electric (GE) and Safran.

However, relief may be at hand, if the promised fixes materialize as planned. Pratt has assured Airbus that it can deliver a modified PW1100G in April, which would likely enable Airbus to resume deliveries of the variant to customers in the subsequent weeks.

The root cause of the problem has been identified, Pratt has told Airbus, and the engine maker is due to present a mitigation plan to airworthiness authorities by Feb. 16.

The European Aviation Safety Agency (EASA), and subsequently the FAA, issued emergency airworthiness directives grounding all aircraft that have two engines installed with a modified knife-edge seal on the high-pressure compressor aft hub. Aircraft with one of the so-modified engines can no longer operate extended-range twin-engine operations (ETOPS) flights.

The measures follow two recent in-flight shutdowns (IFSD) and two rejected takeoffs tied to the new problems. In each incident, an engine experienced high rotor vibration and a stall. All four engines showed similar damage: fractured high-pressure compressor rear hub knife-edge seals.

“We are issuing this [airworthiness directive] to address a high-pressure compressor (HPC) rear hub knife-edge seal fracture, which could lead to a sudden increase in high rotor vibration and stall in certain PW1100G engines, and consequent IFSDs or rejected takeoffs,” the FAA writes. The EASA directive stated the risk of dual inflight engine failure.

Pratt says an engineering change was made in mid-2017 to improve durability and introduced into revenue service on customer aircraft in December. But in late January and early February, “four of these modified engines did not perform as anticipated,” Pratt concedes. According to Pratt, 43 of the modified engines are on in-service aircraft, while a further 55 have been delivered to the Airbus final assembly lines.

The company is “working to assess an overall industrial and delivery plan to minimize customer disruption,” Pratt says. However, the plan depends on regulatory authorities’ approval of the proposed solution. The 43 engines are installed on 32 aircraft, 11 of which have to be grounded after three more sectors, according to EASA. Twenty-one have only one of the affected engines installed.

Airbus says it has stopped taking more PW1100G engines from the manufacturer, pending a technical fix. It can also no longer deliver new Pratt-powered A320neo-family aircraft to customers until the fix has been implemented. Indian low-cost carrier IndiGo grounded three of its A320neos following the EASA order. With 32 aircraft in its fleet, IndiGo is the biggest A320neo airline customer, followed by Air Asia with 23. Lessor AerCap has taken 35 aircraft so far. Airbus has delivered a total of 233 A320neos and 21 A321neos.

Enders emphasizes that the latest issue means “more work, stress and strain and more disruptions for our customers.” However, he cautions that the impact on 2018 Airbus deliveries is not clear yet and may be less significant than many expect. “Look at what our teams have done in the past year,” he says, referring to earlier changes to the engine and the following recovery effort. “Of course, we need engines, but I am confident our partners will not let us down.”

The Airbus CEO also makes clear that Pratt is “not alone” in causing delays: “CFM is behind in [engine] deliveries to us, and that is something that needs to be corrected.” But he adds that he has “commitment from the top leadership at GE and Safran that they will do everything they can to fix this.”

Airbus expects to deliver around 600 single-aisle aircraft in 2018, 400 of which are planned to be A320neos and A321neos. The 400 aircraft are split roughly evenly between the CFM- and the Pratt-powered variants.

For Pratt & Whitney, the knife-seal issue emerges just as it is resolving the longer-term reliability problems with the No. 3 bearing seal and combustor that have dogged the engine program since 2015. Revealing details of what it believes will provide the final fix to these long-running issues, Pratt says all new engines are now being delivered with the revised configuration, and the changes are being implemented in both PW1100G A320neo engines and PW1500G powerplants on Bombardier’s C Series aircraft as they come back in for overhaul and modification.

The chief change to the bearing housing is a switch from the liftoff seal used in the original design to a dry-runningface seal that becomes the standard configuration. The dry-running face seal consists of a rotating mating ring made from a carbide material and a carbon-graphite stationary ring. The faces are flat and held tightly together using magnets or springs to prevent oil leaking through, despite the high revolutions. The liftoff seal, on the other hand, incorporates grooves and wedges to channel a thin film of air between the sliding sealing faces, which creates aerodynamic lift.

“We originally went with a liftoff seal because we thought it would be more durable over time. It turns out the problem we discovered was that the software was misreading the altitude, so the bellows were not putting enough pressure on the carbon seal to create that air bubble. Sometimes it was putting too much pressure, which was causing the carbon flakes to go into the oil side,” a Pratt spokeswoman says. The resulting gap between the carbon air seal and associated seal plate allowed traces of metal particles to enter the oil system and trigger chip-detector warnings.

Pratt paved the way to the final fix by introducing an interim upgrade package in May 2017 that included the addition of a venturi tube to reduce the air pressure directed at the bearing compartment as well as associated modifications to the electronic engine control software to restrict the airflow. The tube was external to the compartment itself but integral to the carbon seal package.

“The improvement package performed better than we had hoped, except for engines that had higher time on them, which had to be reprioritized for overhaul,” Pratt says. The liftoff seal and the improvement package “bought us time to work out whether we needed to develop a permanent fix to the liftoff seal or go to a standard brush seal or dry-face design,” Pratt adds. “We decided to go with a dry-face design, and that’s now part of the standard bill of material.”

The revised combustor configuration is designed to address the durability problems that led to a rash of premature engine removals by two Indian-based A320neo operators, GoAir and IndiGo. “We have roughly doubled the number of air cooling holes and configured the density of the holes to the lower left of intake/outtake valve. We essentially had the density in the wrong place originally,” the engine maker says.

The revised design is expected to increase durability by a factor of five over the baseline. Although the interim fix fielded in 2017 appears to be adequate for non-harsh environments, the revised combustor design will now be standard to cope with operations in areas such as China, India and the Middle East. All the upgrades have been introduced to production engines and will be woven into engines coming through for overhaul.

Pratt meanwhile says it remains on track to almost double production in 2018 compared to the 374 engines made last year. “Our facilities are ramping up for new production as well as overhaul capability, which last year we matured faster than we had expected,” the company says, noting it expects to be under significant pressure throughout the year. “There is still a population of engines that will have to go through overhaul again because they are operating with the improvement package on the No.3 bearing and/or the combustor,” Pratt notes.

The first results from crucial tests of two key elements of Rolls-Royce’s future large civil engine strategy—a new core and a high-power gear system—are positive and on track, says the powerplant manufacturer.

Providing details of results from the first test runs of the Advance3 high-pressure core at the heart of the company’s UltraFan concept, Phil Curnock, chief engineer for Civil Aerospace Future Programs, says “we have done a significant amount of testing and all technologies are performing well.”

The core is the common element of the company’s plan to succeed the long-running Trent family with a new gear-driven engine architecture from the 2020s. The new core, which began tests in November in a hybrid demonstrator, will run initially in the Advance, a direct-drive turbofan with a fuel-burn level at least 20% better than the current Trent 700. However, the Advance is a steppingstone to the UltraFan, a very-high-bypass design that marries the same core to a large gear-driven fan to improve fuel burn by at least another 5% over the Advance.

“The UltraFan, which we hope will enter service in the 2025-27 time frame, will be sold to airlines for 15-20 years and remain in service for probably 40 years,” says Rolls-Royce Chief Technology Officer Paul Stein. “So the second generation of aviation is not going to come to an end for 60-70 years. The UltraFan at present is a demonstrator of all the new technologies, and we plan on launching it as a product in a few years’ time.”

Stein notes that aircraft manufacturers continue to be briefed about the Advance and its UltraFan follow-on engine. “Each of them may or may not modify their airframe plans as a result of having this technology available,” he adds. “It is such a step change in fuel burn that it is starting to make them sit up and take notice of what sort of efficient aircraft could come about if a modern aircraft design was coupled with the UltraFan engine itself. In our view it is going to drive change in the market.”

Stein further says wing configurations will have to be modified for the very-high-bypass architectures under development for the UltraFan. A gear-driven fan sized to produce about 70,000-75,000 lb. of thrust, for example, will likely have a diameter of 140 in., compared to the 112-in.-dia. fan of the similarly rated Trent 1000 of today. “One option [the airframe-makers] could consider is to go for gullwing configurations and short nacelles mounted close to the wing,” he adds.

In the Advance3 demonstrator the core is sandwiched between the conventional fan system of a Trent XWB-84 Airbus A350 engine and the low-pressure turbine of a Trent 1000 Boeing 787 engine. “We are in Phase 1 of testing and it is progressing extremely well,” says Curnock. Tests have quickly reached the point where the P30 pressure (at the rear of the high-pressure compressor) has “got to 450 psi,” he says. “That means we have got to about 90% of core power.”

Key tests include measurements of the bearing loads to assess the impact of Rolls’ design choice, to place more work on the high-pressure spool and reduce the load on the intermediate compressor. “When you change the work split between the compressors it gives different axial forces to the bearings, so we need to manage and monitor that,” says Curnock. Other tests on the new core include water ingestion, a noise survey and an X-ray examination.

Tests of the core’s lean-burn combustor, which is also a new design to reduce emissions and boost efficiency, have also been positive, with no signs of an aero-acoustic effect known as a “rumble” that can sometimes occur with these designs. “We haven’t seen any rumble at all, which is quite satisfying,” says Curnock, who adds that tests for other typical lean-burn-related concerns such as starting issues and fuel scheduling have “gone really well.”

Rolls-Royce has also begun tests of the third power gearbox (PGB) at its Dahlewitz facility in Germany. Evaluation of the 1-m-dia. (3.2-ft.-dia.) unit, which is a planetary style gearbox with a ring gear on the outside and five planet gears inside rotating around a central sun gear, follows the news in September 2017 that the first PGB had been tested at its maximum rating of 70,000 hp. This rating is designed to enable the gear to be mated with the Advance3 demonstrator, which is aimed at the 70,000-80,000-lb.-thrust bracket.

Further components of the future engine family are also being tested in a parallel series of focused demonstrators. These include the advanced low-emissions combustion system (ALECSys), which is dedicated to testing the lean-burn combustor design at a full-scale engine level in a modified Trent 1000. The engine, which made its initial run in the weeks running up to the Singapore Airshow, will shortly be shipped to the company’s test site in Thompson, Manitoba, for cold day and cold soak starting as well as ice shedding and ingestion testing. Curnock says the engine will later go to Rolls’ site at NASA Stennis in Mississippi for noise testing and “in the next couple of years” will be flown on the company’s Boeing 747-200 flying testbed.

Rolls-Royce is also poised to begin runs of the Advanced Low-Pressure System (ALPS) engine which, for the first time on one of the company’s powerplants, combines tests of a composite fan with a composite fan case. “We have just got to pop the fan blades in the front, and we will be putting that on test later this year. That’s a good step forward because that is all about understanding not just the composite blade but also the performance of the composite case with the fan,” says Curnock. Testing is expected to be complete by year-end.

As the U.S.’s adversaries field more complex and deceptive missiles, high-flying UAVs armed with advanced sensors and laser weapons could hold the key to defeating them.

Instead of using Boeing 747 airliners to shoot down missiles with chemical lasers, the U.S. Missile Defense Agency (MDA) proposes employing high-altitude, long-endurance UAVs carrying modern diode-pumped alkali or beam-combining fiber lasers.

The agency has also proposed an upgrade kit for the General Atomics Aeronautical Systems MQ-9 Reaper that would allow the remotely piloted aircraft to detect and track missile threats as an airborne complement to ground-based missile defense radars.

The U.S. has spent hundreds of billions of dollars over decades developing exquisite radars, interceptors and exoatmospheric kill vehicles to take out traditional ballistic missiles. But North Korea and Iran’s pursuit of decoys, penetration aids and defensive countermeasures for their missile forces, as well as Russia and China’s introduction of more advanced hypersonic airbreathing and boost-glide vehicles, is undermining America’s investments.

To counter these evolving threats, over the next five years, MDA proposes spending about $780 million to ramp up experimentation with droneborne sensors and laser weapons technologies. This level of funding pales in comparison to investments in next-generation radars, interceptors and kill vehicles, but it will validate new operational concepts for UAVs that could be rapidly fielded through partnerships with the military services, particularly the U.S. Air Force.

Today, the U.S. has very few options for taking out missiles in the boost phase, when they are moving slowest, hottest, and have not yet deployed defensive aids. But the YAL-1 Airborne Laser program in 2010 proved without a doubt that directed energy can efficiently and effectively shoot them down. Using a massive megawatt-class chemical laser, the 747 successfully intercepted multiple Scuds.

Although the flying laser testbed was canceled in 2011, MDA’s interest in lasers for missile defense never really went away, it just transitioned to new types of lasers based on high-altitude unmanned platforms.

“The 747 Airborne Laser wasn’t a waste of money at all; it advanced some optics and beam-control capabilities that make the current program possible today,” says Thomas Karako of the Center for Strategic and International Studies. “We’d be further along today if that program had been prudently adjusted rather than canceled. We lost years.”

Karako says the 747 had obvious operational limitations, but he encourages MDA to “stay the course” with its transition to unmanned platforms and solid-state laser weapons, and not get distracted by “every shiny object.” He says putting new types of sensors on UAVs and space-based platforms will also help fill the U.S. government’s “midcourse gap” in the birth-to-death tracking of missile threats.

On Feb. 12, MDA Operations Director Gary Pennett confirmed during the agency’s fiscal 2019 budget rollout that interest in high-altitude UAVs for finding, fixing and defeating missiles remains high, and funding has been earmarked for continued experimentation.

He says MDA is moving forward with preparations for a droneborne laser experiment, with flight-testing expected to get underway in the 2022-23 time frame.

The agency’s budget line for “technology maturation initiatives” supports two main UAV-based efforts, one for scaling up lasers and another for discriminating sensors.

Pennett says $149 million has been requested for these efforts in 2019, of which $61 million advances the agency’s Low-Power Laser Demonstrator (LPLD) program and $79 million funds Discrimination Sensor Demonstrator Development.

LPLD carries forward the work pioneered by the YAL-1 program, except on a high-altitude unmanned aircraft, although the government has not ruled out using a manned surrogate. If fielded, the platform would certainly be remotely operated to increase loiter time and reduce the cost of maintaining 24/7 orbits.

Last year, MDA awarded contracts to Boeing, Lockheed Martin and General Atomics to develop competing proposals. Later this year, the agency will select one of those proposals to carry forward into initial design. By next year, MDA expects to have a system-level blueprint ready for construction.

MDA has been working with two federally funded research laboratories on high-power laser architectures that could be scaled up to defeat missiles. Lawrence Livermore National Laboratory has been developing a next-generation diode-pumped alkali laser, while MIT Lincoln Laboratory works on a beam-combining fiber laser.

According to the agency’s budget documents, flight-testing of the preferred high-altitude drone is set to begin in 2022. Flight experiments would take place in 2023, starting with target-acquisition and tracking-discrimination trials, followed by beam-control-and-stability and eventually high-power laser testing. MDA has earmarked $331 million for these laser experiments through 2023.

We have some idea about the performance specifications of the high-altitude test platform, thanks to a request for information issued last June. The testbed aircraft must fly above 63,000 ft. with an endurance of at least 36 hr. at cruise speeds of about Mach 0.45. It must have a payload capacity of between 5,000 lb. to 12,500 lb., produce 140-280 kW of power, and support an optical sensor measuring 3.3-6.6 ft. (1-2 m).

Pennett says MDA would not buy its own fleet of laser drones, but instead partner with the military services because its drones are test assets.

For sensor development, the agency has budgeted $407 million through fiscal 2023, which funds ground, airborne and space-based testing of “tracking lasers, advanced detectors, infrared sensors, and precision tracking and discrimination algorithms.”

For these experiments, the agency has access to three General Atomics aircraft: Two Block 1 MQ-9s and one extended-range Block 5 MQ-9 “Big Wing” UAVs. The aircraft are contractor-owned and operated, with the most noticeable modifications being forward-looking Raytheon Multispectral Targeting Systems (MTS). While past experiments have used two MQ-9s to stereoscopically detect targets, the agency is upgrading the latest MTS-C sensor turret, which incorporates a tracking laser for single aircraft missions.

These medium-altitude aircraft, when linked into the wider ballistic missile defense architecture, would be valuable airborne sensors that could track conventional as well as maneuvering hypersonic threats, according to MDA.

“MDA is partnering with the services to develop concepts for the cost-effective integration of the sensor technology into limited-fielding upgrade kits,” the budget documents state. “These kits could be installed on MQ-9 aircraft deployed in-theater to add missile defense capabilities on short notice.”

A contracting notice issued in September say MDA has been discussing with the U.S. Pacific Air Forces the possibility of deploying these MQ-9s to Japan’s Kadena Air Base “or an alternate remote deployment location.” However, probably due to regional sensitivities, Pennett says the budget does not support a deployment to Japan. Agency documents show significant flight-testing with the MQ-9s taking place in the fiscal 2021 and 2022 time frame, including a “launch-on-remote” test where an interceptor will be fired at a target based on targeting information from the drone’s new sensors.

Riki Ellison, chairman and founder of the Missile Defense Advocacy Alliance, says the fiscal 2029 budget submission does not hugely ramp up investment in these airborne sensor and laser programs, but he expects greater investment to come in the 2020 budget plan.

“They need to put their best people on this technology and advocate for more investment to fully develop and test it,” Ellison says. “It is the most challenging of all of the missile defenses we are developing. It needs to be on the scale of their Redesigned Kill Vehicle and Multi-Object Kill Vehicle investment.”

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