Knowing when to purchase or replace life limited parts to minimize under-utilization or expiration may seem like a small thing, but there are several installed on any one aircraft and just one that is missing or expired can ground or delay that multi-million dollar working asset. Items like passenger oxygen generators (that supply oxygen to the masks that lie above passengers’ heads), life vests, first aid kits, protective breathing equipment, specialized emergency equipment batteries, portable oxygen bottles and emergency defibrillator devices are all considered life limited parts.

It may not be difficult to keep track of life limited parts on one aircraft, but for Delta’s fleet of more than 700 aircraft, that equates to about 140,000 life vests, over 40,000 oxygen generators and more when you add in the items mentioned above. The dynamics of aircraft flying all over the world add further to the challenge of tracking life limited parts.

To be safe and remain in compliance, life limited parts are checked regularly to ensure that no items remain in service beyond their expiration date. Depending on the type of maintenance program, items like oxygen generators are checked while the aircraft is in for the equivalent of a C-Check, or about every 18-24 months. The overhead passenger service units (PSUs) are opened so dates on the oxygen generators can be visually checked. At that time, mechanics read the date of manufacture, which may involve loosening a bracket, rotating the generator so the data placard is visible, reading the date and then reinstalling the bracket. Life vests are managed in a similar manner, with lots of time spent crawling around the floor looking under a seat cushion to check a date. A calculation to determine the remaining service life is done to make sure the item will not expire before the next check, allowing for an appropriate safety margin. If it is determined that the part will still be serviceable until the next scheduled visit date, the mechanic tightens everything up and moves on to the next location. For comparison, there can be approximately 60 oxygen generators on a typical B737 to 200 or more on a B777 – depending on the configuration and there can be hundreds of life vests that require inspection. It can be very time-consuming to check each part, taking from a few hours to a whole shift or more.

Not only is the inspection process tedious, but the chance of collateral damage to other parts is significant – standing on seats to be able to read the small text on data placards, pinching wires or tubes when latching the PSUs, accidentally activating the generator (which heats to about 350F), etc.  Multiply that by a fleet of 40,000 generators or 140,000 life vests and you have a significant workload. Without the data being captured in a record keeping system, this same cycle of work will be repeated each time the inspection is due – visually checking each part, no matter how new, to ensure serviceability until the next visit.

Cost and timing for replacement inventory adds to the challenge. Buy too many and parts sit on the shelf unused with the calendar running: order too few and AOG (aircraft on ground) shipping expenses pile up for overnight shipping from all over the world.

The target
A few years ago, Delta Air Lines started evaluating a new paradigm to address these business challenges. We needed something that would improve the process not by a few percentage points, but by orders of magnitude. We also wanted to minimize any business process changes. We wanted to be able to use data to replace inventory – data is better, faster and much cheaper than inventory. Our past approach was ‘we don’t know we need it until we look’ but with data (knowledge) the future process will be ‘we don’t have to look until we know we need it’. This saves in three significant ways:

1) Avoids purchasing life limited parts before they are needed (reducing shelf-loss);
2) Minimizes AOG shipping expenses related to these items;
3) Avoids repeated date checks on items that are still serviceable.

Delta was also committed to getting results quickly, no airline can afford a multi-year return on investment (ROI); we are also committed to a learn-as-you-go scenario. We knew we couldn’t figure out all the benefits or all the costs, ahead of time but we were pleasantly surprised at what we found.

A fast, accurate way to collect and store data for selected life limited parts was needed, and Delta settled on using RFID (Radio Frequency ID) technology. RFID technology is truly amazing – it’s like bar code technology that doesn’t need line of sight. The radio waves from a handheld reader can go through, over, under and around obstacles to provide the RFID tag with RF energy. This allows the tag to answer back to the reader. If the portable reader sends out one watt of power to query any RFID tags in the vicinity, each RFID tag answers back at about one millionth of that power to say ‘I’m over here and here’s who I am.’

The reader can find hundreds of tags per second which is pretty amazing considering that the RFID tags have no power of their own (passive RFID) and the RFID chip itself is no bigger than a grain of pepper.

Delta started pursuing this technology solution in 2009, at about the same time the partnership of Aerospace Software Developments (ASD, Dublin, Ireland) and Technology Solutions (Oakland, CA) began making RFID commercial off-the-shelf solutions available for airlines. They are leaders in aviation RFID, having helped develop the ATA Spec2000 RFID standards and demonstrated the first industry solution in 2007. They also have solutions for OEM suppliers. Their software solutions are the only ones in the industry that have been certified by the GS1/EPCGlobal organization.

The initial goal for Delta is to make parts visible to those who manage and replace them. With this visibility comes an element of predictability for inventory, scheduling and workflow – helping, as discussed earlier, to avoid costly surprises and expensive AOG shipping expenses.

The solution
The first demonstration of the RFIDAeroCheck solution to Delta management occurred over two years ago with Directors and Managers in the First Class section of a Boeing 757 and more people standing in the back aisle. The Oxygen Generators in the PSUs had been previously tagged with RFID tags. A brief explanation of the system was provided by Dave Browne from ASD in the front of the First Class section, then the trigger was pulled on the handheld reader and a series of beeps – too quick to count – was heard from the reader. It had read the entire First Class section without taking a step.

Dave then demonstrated how easy it was to induct the individual oxygen generators into the software. The reader was handed to each person to enter the necessary data just like a mechanic would at each generator location. There was initial hesitation, followed by an, ‘Is that all there is to it?’ response.

After a brief discussion of the potential uses for RFID on our aircraft, we got the thumbs-up approval to proceed with the project, and we were off and running.

Delta did not wait for OEMs to begin tagging their oxygen generators to be able to leverage the technology. It didn’t make business sense to wait for existing O₂ generators to age out of the system, nor to replace all the generators with new ones – that would lose a significant amount of useful life on those assets and would take us in the wrong direction. A solution was developed for tagging these legacy parts according to the ATA Spec2000 standard, giving each legacy part a unique number to identify it. In the future, OEMs will be delivering RFID tagged parts containing the actual manufacturer’s CAGE Code, Serial Number, Part Number, and Date of Manufacture. At that time, the transition will be transparent and the mix of both new and legacy parts will coexist seamlessly.

The oxygen generator RFID tags designed for this particular use work extremely well, providing 15’ foot read ranges and quick read times using a portable RFID reader. Tags are also available for application to life vests, life vest boxes/pouches, passenger oxygen masks, medical kits and many other emergency equipment items.  All are available from William Frick & Company and are AS5678 certified, as required by the FAA.

The software chosen, RFIDAeroCheck, presents a small footprint, is server based and web accessible. It provides many user assignable switches to allow configuration for a variety of terminologies, date formats and expiration schemas (i.e. first of month, last of month). The portable RFID scanners connect via Wi-Fi at hangar and line station locations. Mechanic training for the wireless handheld scanner application was easy and only took about 30 minutes on the aircraft.

Training for the server side application is slightly more involved. That’s where the LOPA (LayOut of Passenger Accommodations – essentially the floor plan of the airplane) is created for each fleet configuration and populated with the desired emergency equipment. The process is assisted by a GUI (Graphic User Interface) design tool and some basic configuration menu selections – such as, Economy is 3×3 seating starting at row number 11 and continuing for 28 rows; and immediately you’ve generated a picture of the Economy section seating. Adding lavatories, galleys, closets, exit rows, extra aisles, etc. is easy. The locations are click-and-drag positioned and can be named according to the appropriate nomenclature. The layout is easily created and looks like the actual aircraft so all equipment will be located where it is expected on each aircraft. The design tool accommodates single aisle, double aisle and double decker, also allowing for custom named classes and extra sections. The server software also holds the software configuration options, reference part data and reporting functions.

Once the LOPA is configured in the software, each location (seat, PSU, closet, etc.) is populated with a life vest, oxygen generator, etc. until there is a complete map (and database) of every piece of equipment for each aircraft.

The process
When the aircraft arrives for a visit, each item is inducted into the software, assigning each uniquely identified part to its specific location. Drop down menus or 2D barcodes are used to harvest the part number and date information. This initial induction can be done on a B757 in about 40 minutes by two technicians and about two hours on a B777. After the induction is complete, the part information exists on the server and can also be checked with a 45 second walk down the aisle with the handheld scanner, quickly confirming the presence and expiration status of any tagged items – to the specific location. Any items that appear on the Exception Report, generated on the handheld software following the RFID scan, are visually checked for serviceability and replaced, tagged and inducted back into the software if required.

This RFIDAeroCheck solution is a complete, standalone solution from data collection to automated reporting. It can even automatically email data for notification of items that are approaching an expiration date. The database reporting function also allows maintenance to plan what their life limited part workload will be on any given tail number, and allows inventory analysts to better predict both short and longer-term inventory requirements. OEMs also benefit, minimizing last minute AOG orders and scrambling to accommodate customers. It’s a win-win for everyone and, when appropriate, this solution can be integrated with existing enterprise systems for inventory planning and scheduling of aircraft maintenance, to generate even greater ROI opportunities. Delta has not integrated the RFIDAeroCheck software with the enterprise systems yet. Our approach is ‘learn first, and then grow’.

The ROI to Delta can be measured in terms of months, not years. Implementation is not at all complete and we are still exploring the scope of equipment that should be tagged. We are also investigating ways of performing item level security checks using RFID solutions. We are also working with select vendors to include RFID tags on new purchase inventory. This will begin the process of switching to OEM tagged inventory. Until then, we have a solution to best manage our legacy tagged, already paid for, flying inventory.