MRO companies are using a variety of robotic solutions to speed up the inspection and repair of aircraft. BILL READ FRAeS reports
One of the more time-consuming tasks faced by aircraft maintenance, repair and overhaul (MRO) companies is inspecting the exterior of an aircraft to assess its required maintenance needs. In addition to scheduled maintenance and lease checks, such inspections may be required (if the aircraft receives accidental damage or is suspected of being damaged). This could occur while the aircraft is in the air (lightning, ice, bird strikes), during take-off and landing (FOD on the runway and possibly now also from rogue drones at airports) and while stationary (collision with service vehicles or accidental collisions with other aircraft).
If any of these incidents should happen or are suspected as having happened, then the aircraft must be taken out of service and inspected for damage. To conduct an inspection, engineers have to set up gantries or utilise lifting equipment, such as a cherry picker, to get themselves up to the level of the fuselage and wings and then move about the aircraft to inspect each part. This is often a complicated and lengthy process and one that has health and safety considerations to avoid the risk of injury through falling.
To speed up inspections, MRO providers have been looking at alternative ways of looking at the outside of an aircraft that does not involve having to get a person up off the ground. One particular area of interest is in robotic systems which can inspect aircraft much quicker and more easily than a human could. Using automated inspections can greatly reduce inspection times from hours down to minutes, enabling skilled aircraft engineers to manage more complex tasks and reducing the cost of the overall maintenance process.
From flying drones ...
MRO Drone (a collaboration between technology and unmanned systems company Blue Bear Systems Research and Irish aircraft engineering software specialists Output 42) has developed RAPID (Remote Automated Plane Inspection & Dissemination) aircraft inspection system. The concept was derived from an earlier Blue Bear project RISER (Remote Intelligent Survey Equipment for Radiation) which used drones to create 3D pictures of damaged or contaminated sites, such as the Fukushima nuclear power station. Designed to be operated by personnel with minimal operator training and no previous drone experience, RAPID can quickly acquire inspection data which can be analysed and the information passed on using an airline’s reporting systems. A high definition imaging system can record features as small as 1mm2. MRO Drone says that its system can reduce aircraft inspection times by up to 90%.
Blue Bear drones are currently being used by EasyJet to conduct aircraft inspections. The airline reports that checks that used to take days can now be completed in a couple of hours. (See Inspector Gadget 22 May 2018) https://www.aerosociety.com/news/inspector-gadget/
Blue Bear hopes that its UAV inspection system will be able to be used outdoors as well as within hangars – although this will require approval from other airport users. Looking to the future, the company anticipates that an inspection drone could be carried onboard an aircraft in case it is needed at a remote location.
At the MRO Americas show in 2018, Airbus unveiled its own MRO inspection drone, the Airbus’ Advanced Inspection Drone. Designed for use inside a hangar, the drone is fitted with an integral visual camera, a laser-based obstacle detection sensor, flight planner software and an Airbus’ aircraft inspection software analysis tool. Developed in co-operation with Airbus’ subsidiary Testia which specialises in non-destructive testing, the system is optimised for inspecting the upper parts of the aircraft fuselage.
Transported inside a large suitcase, the Advanced Inspection Drone is designed as an alternative means to conduct an automatic general visual inspection of an aircraft – except that it can be operated by someone with no drone flying qualifications and can inspect an entire A320 family aircraft in 30 minutes. The automated drone follows a predefined inspection path during which it takes all the required images using the on-board camera. It is equipped with a laser-based sensor capable of detecting obstacles and can halt the inspection if necessary. The pictures are then transferred to a PC database for detailed analysis using a software system. MRO engineers can localise and measure visual damage on the aircraft’s surface by comparing it with the aircraft’s digital mock-up. The software also automatically generates an inspection report.
In 2015 SITA OnAir is reported to have conducted tests at Geneva airport using UAVs fitted with cameras and ultrasound sensors to inspect aircraft. The tests used a tethered Fotokite drone outside hangars and an untethered eXom Quadcopter inside hangars.
… to crawling robots
Not all MRO inspection robots fly. New Zealand-based Invert Robotics has developed a robot which employs a patented suction mechanism enabling it to cling to the outside of an aircraft at any angle, including being upside down. In this case, the original application for the design did not come from inspecting hazardous areas but inspecting the curved surfaces of stainless steel tanks used in the dairy, food and drink industry. The MRO versions of the robots can operate on both dry and wet surfaces, enabling them to be used both inside hangars and at outside locations. In December Invert Robotics announced that it had further advanced the technology with advanced suction systems which could cling to rough or uneven surfaces
Each robot is fitted with an inspection camera which can record and transmit video images to engineers on the ground, who can use the images both to detect where repairs are needed and to record the condition of the aircraft over time. The high definition cameras can assess surfaces for flaws such as pits and cracks which may be undetectable to the human eye. The robots can also be fitted with additional sensors for ultra-sound and thermographic testing – particularly useful for detecting damage in aircraft built with composite components which can appear undamaged in a visual inspection but may be damaged internally. A full repair assessment report can then be provided within 72 hours.
In 2016 Invert Robotics trialled its robotic aircraft inspection system with Air New Zealand and, according to the manufacturer, a number of airline operators and other companies are now considering adopting the technology. Last year international MRO service provider SR Technics, announced a partnership with Invert Robotics to implement a robotics solution to use the robots to carry out inspections on aircraft fuselage, wings, control surfaces and stabilisers. However, SR Technics decided not to continue robot testing for the time being.
MRO specialist Lufthansa Technik (LHT) has developed a Mobile Robot for Fuselage Inspection (MORFI) which uses thermographic crack detection to inspect metal fuselages. Fitted with vacuum pads to enable the robot’s feet to cling to vertical and overhanging sections of the fuselage, Morfi is designed to inspect a number of preprogrammed points on fuselages. The robot is fitted with two coils to heat the points with electric pulses and, using infrared cameras, detect cracks as narrow as 1mm. Future versions may also be able to inspect CFRP and glass-fibre reinforced aluminum.
Engine inspections
Robotic solutions are also being used to facilitate engine inspections and repairs. In 2018 Rolls-Royce announced details of a series of research projects, at various stages of development, designed to use robots to inspect and service difficult-to-reach part of engines while they are still attached to aircraft. These included a remote-controlled boreblending machine, fibre network ‘periscope’ cameras permanently embedded within the engine, snake robots which could be inserted into an engine to conduct patch repairs and micro walking camera ‘beetles’ which could work collaboratively to conduct a visual inspection of the interior of a combustion chamber (See Send in the robots 17 August 2018) https://www.aerosociety.com/news/send-in-the-robots/
US engine manufacturer GE Aviation has also become interested in the potential of robotic solutions for engine maintenance. In 2017, GE took over UK manufacturer of snake-arm robots OC Robotics. Meanwhile, AFI KLM E&M is reported to be looking at using robots to help conduct final inspections of engines after overhaul to automatically compare observations with a database of known defects.
Non-destructive testing
Another advantage of using robots for MRO inspections is that they can access confirmed spaces within aerostructures without the need to dismantle them - non-destructive inspection (NDI). OC Robotics is working with the US Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base in Dayton, Ohio to develop a NDI snake-arm robot system to look for damage in confined and difficult-to-access areas inside US Air Force aircraft.
Other scanning equipment
Not all fuselage inspection equipment has to fly or crawl. Airbus has developed the Air-Cobot robot for inspecting aircraft from the ground which can combine information with a flying drone inspecting the top of an aircraft. AFI KLM E&M uses a handheld 3D scanner which can be used to inspect fuselages for hail damage and detect and record damage images. By using the scanner, engineers can reduce inspection times per square metre by 80% from 4-5 hours down to 30min. AFI KLM E&M’s Barfield subsidiary has also developed ground service equipment to perform altimeter and static system tests and inspections which can be controlled wirelessly from an iPad.
Paint stripping
The use of robotic equipment is not limited to inspections. Several MRO providers are now looking to robotic solutions to conduct procedures which are hazardous or time-consuming for human operators. One such job is removing old paint from aircraft prior to repainting. When conducted manually, this involves multiple spraying of chemical strippers, followed by scraping or sanding. The job is both time-consuming and subject to environmental and safety regulations. In the 1990s the US Air Force introduced the Large Aircraft Robotic Paint Stripping (LARPS) system which uses a robotic arm to direct a high-pressure jet of water or frozen carbon dioxide to remove paint. The system was developed by a predecessor of Pratt & Whitney Automation (PWA) which also produces the Automated Robotic Maintenance System (ARMS) which can remove a wide variety of coatings from jet engine components. Cleaning a jet engine involves disassembling it and then using a combination of chemicals and grit blaster to clean individual components – again a labour-intensive job that is both lengthy and potentially hazardous when conducted by human operators. The ARMS system involves automatically cleaning the component inside an enclosed workcell and can reduce the time taken to clean a component, such as a compressor front assembly case, from 16 hours for manual cleaning down to 90min.
Lufthansa Technik (LHT) has developed CAIRE (Composite Adaptable Inspection and Repair), an automated milling robot which can repair carbon-fibre reinforced polymers on aircraft wings and fuselages. Using suction cups CAIRE can be attached at different angles to CFRP components which it can scan and record any damage. The robot can remove any damaged material and produce customised repair layers, which are manually inserted, glued and cured.
Big data
MRO providers and airlines are not introducing robots in isolation but in conjunction with the current revolution in big data and the Internet of Things (IoT). Aircraft are now fitted with a multitude of sensors monitoring the health of a wide variety of different systems On-board systems are able both detect and predict faults while aircraft are in flight and send messages to their destination airports to have engineers and parts ready as soon as it lands (see https://www.aerosociety.com/news/digital-takeover/). AFI KLM E&M is developing systems which can predict component failures using sensor data downloaded at gates.
EasyJet can monitor the health of CFM56 engines via the aircraft’s Aircraft Communications Addressing and Reporting System (ACARS). The low-cost carrier is also working with Airbus to uses its Aircraft Maintenance Analysis (Airman) system to predict defects before they occur.
Airbus is currently working on the ‘Hangar of the Future’ which combines the use of innovative technologies and IoT-connected equipment, such as drones, scanners, cameras and sensors, with aircraft technical documentation and aircraft in-service data on its Skywise open data platform.
In 2018 MRO Drone announced that it was partnering with asset tracking specialists Ubisense to create Smart Hangar which uses sensors fitted to various assets within a hangar – including inspection drones – to provide real time location information. Using this system, operators can check that tools and equipment are ready for use, in the right place and the engineers are fitting the correct parts and subassemblies, all without the need for paper records.
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