Podcast: Why Delta Is Testing Airplane Structural Monitoring Sensors

Delta Air Lines installed sensors on the WiFi antenna area of an aircraft to test structural health monitoring. Could this be a step toward moving airframe MRO to a more predictive maintenance model, similar to that used by engines? David Piotrowski, Delta TechOps’ senior principal engineer, talks with Aviation Week’s Lee Ann Shay about how aircraft maintenance could shift to data diven, tail-specific maintenance.

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Rush transcript:

Lee Ann Shay:            Welcome to Aviation Week's MRO Podcasts. I'm Lee Ann Shay, executive editor, MRO and business aviation for Aviation Week. The sound quality might be a little bit different, but I am wearing a mask as is my guest. I'm in Atlanta, at Delta TechOps headquarters, with David Piotrowski, Delta senior principal engineer. David, thank you so much for being with me.

David Piotrowski:        Thank you for having me.

Lee Ann Shay:            Today we're going to be discussing airplane structural health monitoring projects that Delta is doing. To start off with, I understand that Delta installed Structural Monitoring Systems sensors on a Boeing 737-800 in January. Can you tell me about that project and what was involved?

David Piotrowski:        Yes. We installed sensors on the WiFi antenna area. There are structural inspections that kick in after a certain amount of time after you install the antenna, and those require intensive maintenance access to get to--removing air conditioning ducks and so forth. The installation prototype was necessary for the approval. The approval process is done via supplemental type certificate, and we are having the supplemental type certificate holder amend the instructions for continued airworthiness to allow this.

Lee Ann Shay:            That sounds good. Why is Delta doing this? What do you hope to gain?

David Piotrowski:        It comes down to cost savings and intensive maintenance access. So, those inspections that require you to take a plane out of service and do hundreds of hours of open up an aircraft to do a 10-minute inspection. Those types of things become really cost saving measures for the airlines. Not only can you keep the airplane in service, but you are going to have more revenue by more flying, and it actually helps with hangar planning and managing your resources overall as a carrier. This is one stepping stone into further applications. We have a variety of applications in with both Boeing and Airbus, to basically do the same thing for a specific task, use structural health monitoring as an alternate inspection, and with that is going to be a huge savings for our operation.

Lee Ann Shay:            Okay, so this is not just about one application for one, the 737-800 fleet. So this is really more than a prototype for one project--it's a bigger exercise.

David Piotrowski:        We literally have dozens of applications across all fleet types. This literally is a stepping stone to wider applications and accelerating the implementation of more efficient maintenance practices.

Lee Ann Shay:            That all sounds really good. So two follow up questions. What's the timing for the 737-800 and can you talk about some of those other applications?

David Piotrowski:        Sure. The 737 application on the WiFi antenna is currently in the approval process at the FAA and we anticipate that being issued in the first half of this year. There are other applications, the 737 aft pressure bulkhead is probably the most likely and we have actually installed sensors on 20 different aircraft and have worked with Boeing on applying for an AMOC (alternative method of compliance to do those inspections. Literally the aft galley is in the way of the inspections. And so when you need to do that inspection, it's a significant burden, it takes three to five days of maintenance and being out of service.  Using the structural health monitoring option, we can route the monitoring lines to a convenient location and literally can do it in probably 30 minutes to an hour.

Lee Ann Shay:            So, 30 minutes to an hour instead of three to five days?

David Piotrowski:        That's right. It literally is that type of game changing philosophy. So we can fly the aircraft more in revenue operation. We could do the inspection at the gates overnight if we chose.

Lee Ann Shay:            Delta has been a big proponent and user of predictive maintenance, for several years. How does this fit into that?

David Piotrowski:        This fits very perfectly into that, primarily because it's all about using data from the aircraft, the system, the engine, and so forth to actually manage our fleet better. And a lot of that gets into predictive and that can mean early warning symptoms, and we can remove a part before it ends up failing and move toward on-condition maintenance. It's all about moving in that direction of having a data-driven tail specific maintenance program. Now, structure is different than an air filter going bad. So the criticality of your system and the way you deal with that data is different, but still it's all about getting that data and then managing that, to be more efficient on your fleet.

Lee Ann Shay:            That makes a lot of sense. Engines have used sensors and predictive maintenance for years. So, why haven't the airframe, the actual aircraft structures, used sensors like this before?

David Piotrowski:        That's a good question. Engines for years have been allowed to fly with cracks and be monitored by repetitive borescopes and by monitoring certain parameters, such as gas, temperature, and vibrations, to get a lot of clues into health. This has driven a lot of proactive maintenance in terms of that. The difference between the engines and the airframe comes down to a design philosophy. The design philosophy for the airframe is the certified under damage tolerance regulations. And with that, there's a different philosophy with the regulators. That's some of the difficulties that we as an industry have to examine, is even though we have the data, just like engine data. What we do with that data and what we do to maintain our fleet is two totally different topics.

Lee Ann Shay:            This could be driving a new philosophy for airframe maintenance?

David Piotrowski:        It could, and I think it will, just maybe not in my career, getting the regulators to move fast is not there. We're currently under Maintenance Steering Group-3. The MSG-3 document is the Bible for aviation maintenance. I've beginning to ask the question--with these new technologies and new sensors, and all this data coming in, is it time for MSG-4? It could be a shift, but it all comes down to using data to manage your fleet and having a data-driven tail specific maintenance program.

Lee Ann Shay:            Thank you for all that information and insight, really appreciate it.

David Piotrowski:        Thank you very much.

Lee Ann Shay:            You're welcome. So listeners, if you have any comments, feel free to contact me at [email protected]. You can subscribe and download Aviation Week's MRO podcast on iTunes. Thanks for listening and thanks for joining us.

Lee Ann Shay

As executive editor of MRO and business aviation, Lee Ann Shay directs Aviation Week's coverage of maintenance, repair and overhaul (MRO), including Inside MRO, and business aviation, including BCA.