Luna Sensor Suite for Aircraft Corrosion Monitoring (LS2A)

Luna Innovations Incorporated Revision A, 03/01/2017

Support phone: 1.434.972.9950 sensinst@lunainc.com

1 Significance of the Technology

The Luna Sensor Suite for Aircraft Corrosion Monitoring (LS2A) is being used for evaluating the

effectiveness of corrosion control practices and tracking corrosion of individual aircraft.

The system has

been valuable in identifying the causes of airframe corrosion and is an enabling technology for condition

based maintenance (CBM) for corrosion. The LS2A system continuously records environmental

conditions and atmospheric corrosivity to estimate corrosive damage within an aircraft. Without

individual aircraft corrosion severity measurements, airframes may either be maintained more

frequently than necessary or corrosive conditions may not be detected before significant corrosion

damage occurs. In either case, maintenance costs will be lower and aircraft availability will be higher

when using CBM and LS2A monitoring. The LS2A system meets the need for improved maintenance

practices using individual aircraft tracking to address the escalating costs of corrosion.

The LS2A system is a corrosion monitoring platform that measures both environmental and corrosion

related parameters to continuously quantify the severity of the environment within an airframe. By

measuring specific parameters including relative humidity, surface

temperature, air temperature, contaminants, and aluminum corrosion

rate, the LS2A is capable of tracking the severity of conditions that cause

corrosion. While the system is designed specifically for aerospace

applications where corrosion increases maintenance costs and labor, the

LS2A platform can be used to monitor and survey corrosion severity for

industrial facilities, ground equipment, storage, and distributed assets

such as power transmission or pipelines and ground vehicles. The LS2A

helps owners and operators to preserve high value assets that must

function in harsh environments.

2 Case Studies

The LS2A technology has been used to meet a number of military aircraft needs. Three such use cases

include 1) structural monitoring for more efficient H-53K maintenance and sustainment, 2) evaluation of

the impact of operational tempo and corrosion control strategies on a B-52 deployed in the South

Pacific, and 3) assessing the efficacy of aircraft covers on Navy F-18s and dehumidification of Air Force

HH-60s.

2.1 CH-53K Use Case

NAVAIR and Sikorsky are developing integrated health

monitoring systems for the new CH-53K King Stallion

helicopter. The CH-53K will be the largest and heaviest

helicopter in the US military. The US Navy is implementing

structural health monitoring for this aircraft to enable

condition based maintenance. Datasets are collected from a

number of on aircraft monitoring systems including the Luna

LS2A and this information is consolidated in a fleet

management system. By obtaining corrosion and structural

health information using aircraft monitoring integrated with

network based data management, the Navy can more

effectively allocate limited maintenance resources to achieve availability and service life objectives on

F. Friedersdorf, C. Andrews, J. Demo, and M. Putic, “Sensing Systems and Methods for Determining and Classifying

Corrosivity,” US Patent 9,518,915, 2016.

Figure 2. The Navy’s CH-53K heavy lift

rotorcraft.

Figure 1. Luna’s LS2A Corrosion

Monitoring Sensor Node.

Luna Sensor Suite for Aircraft Corrosion Monitoring (LS2A)

Luna Innovations Incorporated Revision A, 03/01/2017

Support phone: 1.434.972.9950 sensinst@lunainc.com

this new platform. By moving from schedule based corrosion management to condition based

processes, maintenance man-hours (MMH) for inspection and corrosion prevention can be applied

based on individual aircraft need. Through corrosion monitoring and individual aircraft tracking, the

Navy can make informed decisions to prioritize or defer non-destructive inspections and maintenance to

achieve reduced costs and increased aircraft availability.

Similarly, corrosion monitoring with the LS2A system has been shown to enable reduced maintenance

costs and improved aircraft availability. The Navy has performed a benefit analysis for the CH-53K. If a

CH-53K has six sensors and enters depot every 6 years (both Navy estimates), that equates to one

sensor per year, or ~$5,000 per year per aircraft in sensor costs. The cost of a MMH was assessed using

the average hourly wage of an E-5, estimated in 2016 at $47.99.

2,3

According to Navy estimates, a fleet

of 200 helicopters would save 250,000 MMH per year by using corrosion sensing. That’s 1,250 MMH

per year per aircraft, meaning that the LS2A enables offsetting a single MMH for $4; a 12x return on

investment.

2.2 B-52 Deployment

In February 2014, Boeing installed four LS2A sensor nodes on a B-52 aircraft. While the initial intent of

the effort was to evaluate the efficacy of lightening hole patches, the value of monitoring corrosive

conditions relative to operational tempo quickly became apparent. The sensor nodes were installed in

four locations on the lower longeron within the aft wheel well, with two nodes each on the left and

right-hand sides of the aircraft. Sealing patches were used to cover lightening holes on the lower right

side longeron, while the left side longeron lightening holes were left exposed. The aircraft was deployed

to the Pacific for a period of approximately 9 months to evaluate the effects of operations and the value

of the lightening hole patches.

Figure 3. Percentage of total cumulative corrosion that occurs 12 hours following a landing and corrosion that occurs during

all other times (left). Percentage of total time for post-flight events (right).

A key result obtained from the deployment testing indicated that corrosion was accelerated

immediately after flight activities. Corrosion did not occur at low the temperatures and humidities

present during flight. However, immediately following flight, the cold soaked structure on the ground in

the humid tropical marine environment resulted in very high corrosion rates. In fact, it was observed

that 25% of the total corrosion that occurred during deployment was associated with these post-flight

conditions (within 12 hours after landing), even though the time of these post-flight events only

“A model for analyzing aircraft maintenance man-hour costs and the impact of expert systems”, Schanz, Keith E. Monterey,

California. Naval Postgraduate School, 1995

http://comptroller.defense.gov/Portals/45/documents/rates/fy2016/2016_k.pdf