Airframe, engine and component OEMs are constantly trying to make their products last longer in service, be more reliable, require less-frequent maintenance and be easier to maintain. Much of the new best-practice maintenance processes are thus being invented by, or in collaboration with, OEM design and engineering teams. This is especially true for aircraft health-monitoring systems.
But innovation is also happening at major MROs, on the line at airlines and among engineers in the many small companies that supply or support aircraft maintenance around the world.
Some improvements derive just from shop-floor mechanics and line engineers taking a closer look at what they do every day and figuring out how to do it better. Some innovations are exploiting the rapidly expanding capabilities of autonomous equipment such as UAVs and robots. And some depend on massive collaborative efforts between major airlines, OEMs, statisticians and information technology specialists to fully exploit the data systems on aircraft.
Take some incremental improvements, for example, made by AFI KLM E&M. It now inspects for hail damage on fuselages using a 3-D scanner to go over 120 sq. meters (1,300 sq. ft.) on a Boeing 777. The scanner provides a 3-D image on the mechanic’s laptop and sends this image in a damage report to engineers. Best of all, it takes 30 min. per sq. meter, versus 4-5 hours for manual scanning, and it is much more accurate.
AFI KLM E&M’s Barfield subsidiary has developed new ground service equipment that performs altimeter and static system tests and inspections. The equipment can now be controlled wirelessly from an iPad, saving time and effort.
The MRO’s engine subsidiary CRMA figured out how to repair a damaged GE90-115 fan hub frame to avoid scrapping it, saving more than $1.5 million per incident. Engineers apply a local heat treatment to the damaged titanium using a technique that avoids oxidation, returning the expensive part to as-new condition in just 21 days. And for an 8-cm (3-in.) crack on a GE90 thrust reverser, AFI KLM E&M invented an on-wing repair that can be carried out during a C check, avoiding a much more expensive removal and repair in a composite workshop.
On a more mundane level, AFI KLM E&M developed a service cart that saves 60% of the time it takes to change a nose wheel on 737s and A320s. Since 40% of wheel changes on these narrowbodies are for nose wheels only, the total gains are substantial. And the MRO developed special tools to perform important CFM56 on-wing repairs at remote sites that lack hoisting equipment. This tooling uses a simple gantry crane and two chain hoists to remove low-pressure compressors and high-pressure turbines onsite.
None of these changes required technical revolutions. AFI KLM E&M looks for innovations that can be implemented quickly and soon. “It cannot be in 3-5 years,” stresses Director of Innovation James Kornberg. “By the time you are finished, the problem will have changed.” And he has another rule: While innovative technology is important, innovation must become part of the company’s culture. “If not, in 10 years nothing will really have changed.”
AFI KLM E&M works hard to embed innovation in its culture. For example, it is now taking both veteran and student mechanics preparing to work on the Boeing 787 into the hangar once a week and asking them how they want to work on the new jet.
The MRO also asks engineers who have designed innovations to present them to suppliers, customers and even journalists. This helps motivate them to make these new ideas work.
Kornberg says the MRO’s program for seeking suggestions from workers has been successful, but not because of volume, even though that is plentiful. “We get thousands of ideas,” he notes. “The most difficult challenge is to implement the good ones.” Management must choose the most promising ideas and commit money to them, knowing that some will be unsuccessful.
That effort continues. The MRO is now looking at automating final inspection of engines after overhaul. This has been done manually by inspectors, but robots may be able to do most of it, with some help from technicians. AFI KLM E&M is working with a university to automatically compare observations of known defects in a database.
Most innovation helps rather than replaces mechanics. iPads make mobile techs more efficient, and AFI KLM E&M will add apps to these devices. For example, augmented-reality apps could help spot defects.
Combining its experience in airline operations with sensor data, AFI KLM E&M is moving toward predicting component failures with its own algorithms. “Many people are talking about this, but not many are doing it,” Kornberg notes. The MRO will start with fuel systems and then move into other critical components, using sensor data downloaded at gates using Wi-Fi.
Big innovations once came from major, full-service airlines and then spread throughout the industry. But low-cost carriers (LCC) are expanding rapidly, and may now be strong enough to lead MRO innovation as well.
For example, EasyJet is testing 3-D printing of cabin parts to speed replacements and reduce storage of spares. Mark Bunting, fleet asset transition manager of engineering, notes the airline would like to use 3-D printing on more safety-critical parts.
The airline is in discussions with 3-D printing companies such as Airline Services Ltd. and Snecma. “We are exploring the concept and getting more partners involved as we look to improve our supply chain,” Bunting says. EasyJet is looking at printing a number of cabin parts such as arm rests, tray tables and window blinds. “Where we have regular defects across the fleet, we would work with suppliers to license printing machines and systems to print a part to their specification and replace the part quickly and efficiently.” The technique would cut both airline and OEMs’ inventories.
Aircraft health monitoring is another area in which the British airline will be playing a much larger role.
EasyJet monitors the health of its CFM56s with two reports for each flight, one for takeoff and one for cruise, both transmitted through the Aircraft Communications Addressing and Reporting System (ACARS) to GE. “Parameters are normalized to standard conditions and plotted against data from previous flights,” explains Aidan Kearney, head of maintenance. “If software spots a parameter shift, it automatically alerts by email EasyJet engineers, who review the alert and take needed actions.”
Now the LCC is working with Airbus, which wants to make its Aircraft Maintenance Analysis (Airman) system for both predicting defects before they occur and troubleshooting them when they do occur much more effective. Airbus’s early-fault prognostics should give EasyJet operations and engineering staff advance indications of faults for all aircraft.
The system’s web-based software receives real-time aircraft-system parameters via ACARS, and transforms them into animated schematics for troubleshooting faults before landing, while also predicting potential issues. This will enable EasyJet to plan component replacements ahead of time, increasing reliability and efficiency.
The joint effort combines the design expertise of Airbus and the operating experience of EasyJet, a major operator of the A320 family; “the perfect combination,” Kearney notes. The effort is still in its early stages but will likely include prognostics for electrical, hydraulic, pneumatic and flight-control systems.
Engine monitoring is also headed for its own transformation. Current engine monitoring processes mainly identify failures after they occur. “The next-generation LEAP on the A320neo will have prognostic capabilities similar to what Airbus is developing for the rest of the aircraft,” Kearney says. He expects the new tools to transform maintenance, at first minimizing and later eradicating technical delays.
UAVs and Robots
EasyJet is also experimenting with unmanned aircraft to inspect fuselages after known or suspected damage.
Inspection frequency depends on events—such as lightning or hail—that come in bunches. The LCC has had up to five aircraft in one base requiring lightning-strike inspections on the same day. Now aircraft are moved from gates to hangars or parking spots, and mechanical stands or access platforms are used for manual inspection.
UAVs can complete detailed aircraft checks, quickly reporting any damage requiring repairs. Checks that now take more than a day will be performed in a couple of hours, says Bunting.
The UAVs will fly around airliners, providing images of aircraft skin with the same detail as visual inspections. An operator always controls the UAV, either guiding the inspection or setting a predetermined pattern. Engineers assess damage in consultation with Airbus. EasyJet is developing a system to present images to engineers intuitively, helping them identify areas of interest or confirm that no action is required.
The aim is first to reduce and ultimately to eliminate technical delays, except for unforeseen events due, for example, to lightning or bird strikes. By the end of 2016, the carrier expects to use UAVs at up to 10 engineering hangars, including those at London Luton, London Gatwick, Geneva, Basel, Berlin, Paris Charles de Gaulle and Milan. Bunting believes unmanned aircraft may eventually serve other functions such as delivery of spare parts.
EasyJet worked with Blue Bear Systems Research on the inspection UAVs. Blue Bear Operations Director Gavin Goudie says his company developed the entire system, including its Riser UAV and onboard sensors, and manages the database so engineers can quickly survey inspection results.
Goudie estimates the average manual inspection after a lightning strike takes 4-6 hr., while Riser can do it in 30 min. He notes inspection frequency depends on local weather, and thunderstorms tend to be more common over mainland Europe than over the U.K.
Riser’s high-resolution cameras and laser scanners create a 3-D map of the fuselage for engineers’ review. Technicians guide Riser, but eventually the UAV could be programmed to autonomously survey specific aircraft types. The untethered Riser is used in hangars, storing images until the survey is finished. “There is no reason we cannot do it outside, but on very busy airfields you need discussions with stakeholders,” Goudie observes.
The Blue Bear executive believes that a Riser might ultimately be carried on each aircraft. Initially, he expects the drones to be a managed service provided by line maintenance organizations at each airport, depending on frequency of inspection requirements.
Blue Bear also wants to use UAVs for scheduled maintenance, to scan fuselages and plan repairs, for regular fuselage checks between heavy maintenance, and before lease checks to ensure fuselages are in the required condition.
SITA OnAir is also testing UAV-enabled inspections with Delta Air Lines, Emirates Airlines and Geneva Airport. High season for thunderstorms in Atlanta is summer, notes Aircom Portfolio Director Toby Tucker, and lightning strikes can be frequent then. In Europe, each aircraft is struck by lightning on average once a year. Widebodies can take 30-40 hr. to inspect manually, including relocation and set-up time.
SITA is testing two types of unmanned aircraft. The tethered Fotokite is used outside hangars, and the untethered eXom Quadcopter is used inside hangars. Untethered UAVs are best suited for inspections inside structures owned by airlines, while Tucker says tethered drones should be used outside on airport tarmacs.
Tethered or not, sensors and algorithms must keep UAVs a minimum distance from the fuselage—say 1 meter (3.3 ft.)—to avoid damage. The SITA unmanned vehicles carry 38-megapixel color cameras and five ultrasound sensors that work at up to 6 meters.
Tests have proven the unmanned vehicles can capture video images; the next step is automating detection of defects. SITA is asking airlines for libraries of digital images of defects for comparison with results collected by UAVs. These geo-located images can be taken and stored in the cloud for video recognition, and to pinpoint areas for an engineer’s later visual inspection.
Like Blue Bear and EasyJet, SITA wants to make UAV movements autonomous, and this is difficult. Movement must be controlled down to 50 cm in precision, which is beyond the accuracy of GPS. That refinement may take a while, but SITA expects to be operating UAVs manually by the end of 2015.
Tucker believes untethered aerial vehicles have other possibilities. For example, surveying a 100-meter-sq. area on the airfield from 10 meters in height, ensuring no debris is left in aircraft parking spaces. These mandatory debris inspections are now done at Geneva by a worker on a bicycle, and not always very thoroughly.
On land, automated maintenance tasks can be done by robots. Lufthansa Technik (LHT) has developed a stationary milling robot for rapid, automated repair of carbon-fiber reinforced polymers (CFRP) on wings and fuselages. LHT’s Composite Adaptable Inspection and Repair (Caire) project is now making this robot mobile. It will be attached to CFRP components with suction cups and scan and model the surface. Software calculates the best path for removing surface defects and milling. The robot then grinds out damaged material and produces a pre-cut fitting of repair layers, which is manually inserted, glued and cured. All this could be done on-site, without expensive and time-consuming trips to repair centers.
LHT’s Mobile Robot for Fuselage Inspection (Morfi) is automating inspection of metal fuselages. For thermographic crack detection, Morfi moves over preprogrammed points on fuselages rapidly. Two coils heat the points with electric pulses and changes are recorded on infrared cameras, revealing cracks as shallow as 1 millimeter. Vacuum pads on the robot’s feet allow it to reach vertical and overhanging sections of the fuselage. Up to four areas can be inspected and results saved in less than 30 sec. LHT is now working to reduce Morfi’s 75-kg (165‑lb.) weight. It may eventually be used on CFRPs and glass-fiber reinforced aluminum.
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