Advances in automation

Dec 01, 2015

Despite huge leaps in airframe, avionic and engine technology, maintenance remains a labour-intensive business. Outsourcing to cheaper countries can keep costs down, but this trend is slowing as labour rates in places like China catch up with those in the West. To stay competitive one solution may be automation, at least for some types of MRO work, as Alex Derber reports.

Lightning strikes on aircraft were once believed an impossibility, but are now an accepted and relatively well-understood aspect of flight. It is generally thought that commercial aircraft will be hit roughly once per year, though French research suggesting an average of once per 1,000 flight hours would imply up to three annual strikes for aircraft operating at the high utilisation rates of low-cost carriers.

Since the hollow tube of a metal fuselage acts as a Faraday cage, passengers are completely protected from the charge of lightning strike. And while the fuselage and wings do not always escape so lightly, damage is rarely serious on modern aircraft, on which critical electrical fuel and safety systems are well shielded. Nonetheless, some burning or melting can occur at the bolt’s strike points – which move along the aircraft as it cuts through the air – and these need to be found and patched up. Minor damage is thought to result from up to half of lightning strikes.

A bright flash sometimes accompanied by a loud bang will usually alert pilots to a strike. If one is detected then aircraft maintenance manuals require a full exterior inspection to locate and fix any damage, which can range from fist-sized gashes in the most extreme cases to pinprick scorch holes. Inspections usually require a visit to the hangar, where engineers on cherry-pickers, gantries or scaffolds can visually check every inch of the exterior fuselage, wings and tailplanes. Incidents that might also necessitate such checks are bird strikes, hail and collisions with ground equipment.

It can take around eight hours for a few engineers to visually inspect an entire aircraft – precious time out of service to assess what is often minor or non-existent damage. Some crews might accomplish the task quicker, but hangars of the future could dispense with humans completely – at least for the process of the physical inspection itself.

Drones

UK-based Blue Bear Systems Research is trialling a technology that it reckons can accomplish almost all of an exterior survey in around 30 minutes. Developed in partnership with Createc, its RISER drone uses a laser scanning system for autonomous navigation inside the hangar. Lasers paint a picture of interior environments, building up a so-called ‘point cloud’ that allows RISER – originally developed to operate inside nuclear reactors – to avoid obstacles without the use of cameras or GPS.

As a result the drone is able to maintain a three-foot stand-off as it flies around a parked aircraft. A high-definition camera mounted on-board can then record any damage with still and video imagery. A fixed camera is able to survey the majority of narrowbody airframes, though a gimballed device will probably be required to properly inspect widebodies.

RISER is currently being trialled with easyJet, Europe’s second-largest low-cost carrier, which wants to roll out the technology across 10 bases within the next year. Talks have also been held with Thomas Cook, which currently uses mobile platforms for inspections.

"We're always looking for creative solutions to improve our customers' experience, including how quickly we can turn around planes. We've had an initial discussion and short demonstration with a provider of drones but not a formal trial incorporating time and motion cost savings,” says a Thomas Cook spokesperson.

Blue Bear says 10 other airlines are interested in RISER, which it wants to deliver to initial customers by April next year, though “we want to make sure it’s deployable and easy to use before we release it to everybody”, says Gavin Goudie, Blue Bear’s operations director. The drone specialist hasn’t yet decided whether sales will encompass service provision or some form of licensing deal.

Damage recognition

Although RISER can slash the time of a physical inspection, it then loses some of this advantage because an engineer in front of a screen must review the image data. Blue Bear estimates that the entire procedure will still halve the duration of an eyeball inspection (where the physical process occurs concurrently with ‘image review’) but new technologies could accelerate the process further.

Automated damage recognition could, for instance, flag up any damaged surfaces for instant review by an engineer, doing away with the need to cycle through reams of footage of intact areas. Unfortunately technology hasn’t quite caught up with this ambition, though Blue Bear predicts that automated systems capable of working from drone platforms will be available within 18 to 24 months.

“We want the next iteration of the scanning technology to get actual surface defect damage sizes using optical images, but we need a step change in the sensor packages that we can use,” says Goudie.

Confidence in the imminent arrival of automatic damage recognition stems partly from the fact that it has already been trialled successfully in other MRO areas, of which Lufthansa Technik’s ‘AutoInspect’ and ‘AutoRep’ research projects are two of the most impressive.

Adapting a process previously used to image microchips, AutoInspect employed white-light interferometry (WLI) to scan engine combustors for cracks, a task normally performed manually using dye penetrants and UV light. Instead of this, WLI uses interference effects of light waves for a high-resolution capture of a component’s surface that includes automatic damage recognition.

“Enabling the robot to differentiate between surface scratches and micro-cracks has been a challenge solved by intelligent software that enables automatic categorisation of signs of damage, and determination of whether or not these are defects that require repair. During manual inspections, that assessment depends on the inspectors’ individual experience,” says Thiemo Ullrich, head of product engineering for engine part repairs at Lufthansa Technik.

The transition from microchips to the larger and more complex geometries of combustors was a significant achievement, but the damage being scanned for was still in the micrometre range. Systems for RISER will need to resolve at larger scales and be robust enough to function accurately from a hovering platform, rather than AutoInspect’s fixed setting on the ground.

“Some of the companies we have been working with have been using surface-scanning technologies but they are very short range and only cover a small area at a time. So there is technology out there that is capable of finding small damage, but it has to be used in a very controlled manner,” comments Goudie.

Outside the hangar

Given the huge amount of negative publicity generated by several near-misses of low-flying commercial aircraft and unmanned aerial vehicles (UAVs), it is perhaps surprising that Blue Bear’s grand ambition for its aviation-focused drones lies on the ramp.

“Ultimately what we, the airlines and the MROs want to achieve is to deploy this sort of system at the gate on turnarounds. Every time an aircraft lands we can do a scan to get a continual through-life analysis of the aircraft so maintenance can be scheduled appropriately,” says Goudie.

Many aviation authorities are still crafting a regulatory response to the sudden explosion in recreational and commercial drone use. Proposed rules from the FAA stipulate that qualified unmanned aircraft operators may fly drones at and around airports if they receive permission from air traffic control, a position also taken by the UK’s CAA. Therefore there is no great regulatory impediment to deploying UAVs at the gate.

“The key is producing a certifiable system – something that can be proven to operate in a safe manner inside bounded conditions so it does not stray from a dedicated test area,” says Goudie.

Ensuring safe operation near the runway shouldn’t be too big a technical challenge. ‘Geo-fencing’ uses GPS to designate no fly zones – such as over government buildings – and some drone manufacturers are already incorporating these limiters into their products. The main hurdle for a company like Blue Bear would be to prove a geo-fencing system the worked reliably within smaller and more precise confines.

Linking up

Airlines and lessors are becoming ever-more sophisticated in the analysis of performance and maintenance data, which allows them to better manage aircraft lifecycle costs. Deploying drones for external health monitoring, not just damage detection, taps them into this trend. Data from a quick turnaround scan could be fed into an aircraft’s electronic technical log and provide the necessary inputs to improve maintenance scheduling efficiency.

Air France Industries KLM Engineering & Maintenance has used Creaform’s Handyscan 3D device to inspect airframes for hail damage. The scanner uses lasers to build a three-dimensional picture of a surface that can reveal pits, dents and dings far quicker than normal methods. Although the device is currently deployed by hand, it’s easy to envisage a smaller version one day mounted on a drone.

It should be noted, though, that digital scans generate huge volumes of data, which requires extremely capable hardware and software to process if they are not to overwhelm engineers on the other side of the screen. During AutoInspect, for example, every component measurement process involved more than 100,000 WLI measurements and more than 140 gigabytes of raw data.

All that information was processed online and then fed into the next stage of Lufthansa’s research – AutoRep – which generated its own repair programs to repair any cracks using robotic milling and laser powder deposition welding systems.

A threat to jobs?

Since the introduction of the Spinning Jenny in the 18th century, workers have fretted about being replaced by machines, so it’s conceivable that encroaching automation of aircraft support could provoke a backlash from unions. Much of the technology is designed to replace mundane, repetitive tasks that presently consume thousands of man hours. And in the case of AutoInspect and AutoRep, Lufthansa Technik has created an end-to-end process that largely cuts humans out of the inspection and repair loop.

Michael Ernst, Lufthansa Technik’s manager for AutoInspect and AutoRep, counters that automation won’t eliminate jobs, but rather shift them into different areas.

“The partial automation of maintenance processes frees employees from monotonous, routine tasks and allows them to use their manual skills in areas that require a high degree of creativity and flexibility,” he says.

Blue Bear offers a slightly different response, since RISER still requires an engineer to validate damage detection.

“As with all new technology, some reticence is expected over the introduction of the inspection systems. However, Riser's prime use will be as a tool to assist engineers in providing more accurate inspections. The engineer’s skill and expertise is still a key requirement which is currently mandated by regulators and manufacturers,” says Goudie.

In some cases, even tooling threatened with obsolescence by new machines may retain its uses. After all, any damage detected by a drone will still require a full complement of engineers and low-tech access platforms to repair. 

Rather than turn maintenance on its head, then, automations appears more likely to enhance and streamline current practices.