Non-Destructive Evaluation for Corrosions/Defects of Naval Air Vehicles

Navy SBIR 24.1 - Topic N241-014
NAVAIR - Naval Air Systems Command
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET    [ View Q&A ]

N241-014 TITLE: Non-Destructive Evaluation for Corrosions/Defects of Naval Air Vehicles

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Sustainment; Trusted AI and Autonomy

OBJECTIVE: Develop an imaging system suitable for in-situ detection of hidden corrosions/defects in naval air vehicles.

DESCRIPTION: The deleterious consequences of fatigue and fracture in metallic structures arising from local microstructure, mechanical loading, thermal effects, and the corrosiveness of the maritime environment, usually lead to corrosions/defects of aircraft landing gears or other naval aerial platform surfaces. At the burgeoning of the corrosion/crack/fracture/damage, the damage areas are underneath some kind of protective coating or paints and therefore render conventional visible early inspection and evaluation ineffective. Early detection of the corrosion and related defects is critical, as it would reduce the remediation cost, improve the operational safety, and minimize mission downtime of fielded assets. Traditional methods for detecting corrosion defects are inefficient, and involve costly removal and replacement of the coatings and paints for visual inspection of the underlying surface. Removal and replacement of these polymer or painted sections involve costly operations in terms of labor and materials costs.

This SBIR topic seeks a solution of non-destructive evaluation (NDE) of hidden corrosion underneath paints or polymers. Corrosion of aluminum alloys generally develops as pitting or thinning, and in general changes a nominally smooth surface to an uneven and irregular surface, which can then result in cracking.

The detection of this type of corrosion is not within line of sight. The detection of corrosion on aluminum formers that are under composite skins without disassembly would be very beneficial. Inspection through top coats would be ideal. The proposed solution should be able to detect defects with sizes greater than 0.005 in. (0.0127 cm) on a curved surface with a radius of curvature 2 in. (5.08 cm) radius or less.

The proposed solution should be able to detect fastener corrosion. The proposed method should also detect corrosion on fastener threads without the need for disassembly.

This SBIR topic focuses on development of technologies that will image corrosion and defects through coatings and paints rapidly enough to support a sampled or completed NDE of an aircraft. The system should be portable that weighs no more than 12 lbs. (5.44 kg), be capable of expected constant system mobility without need for recalibration more than once annually, and sufficiently robust for operations under harsh maritime environmental conditions. The system needs to be in compliance with all FCC regulations. The preferred system prototype solution should yield detection results as close to real time as possible, and be equipped with a graphical user interface that is easy to use and understood by an operator with relevant training. It is also expected that any proposed system should have built-in wireless capability that can send imaging data to a remote user system for further detection analysis and evaluation.

PHASE I: Develop an imaging system with the capability to meet the operational, frequency, SNR, minimum corrosion/defect size, minimum paints/coatings thickness, and graphical user interface and wireless transceiver as stated in the Description. Detection of a defect is defined as the ability to accurately distinguish the defect from surrounding regions that do not contain the defect, and display the location and size of the defect in a graphic user interface. Demonstrate the feasibility of the concept to detect the aforementioned hidden defects via modeling and simulation. Concept feasibility will be supported by appropriate analyses and laboratory experiments. Provide a Phase II development plan that includes performance goals and key technical milestones. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a prototype suitable for evaluation. Evaluate the performance of the prototype with regard to the goals defined in Phase I on a Navy provided test panel that is equivalent to testing on an in-service Navy asset under similar field conditions. Based on the initial results of the evaluation, refine the prototype and demonstrate that the final prototype meets the performance specifications stated in the Description. Deliver the final prototype at the end of the Phase II that is ready for field testing by the Navy.

PHASE III DUAL USE APPLICATIONS: Transition the technology into a system that can be acquired by the Navy. The Phase III plan should include testing, validation, certification, and qualification for Navy use.

With the ability to inspect aluminum material/structure under polymer and paint, this will provide the private sector with new instrumentation for detecting degradation of aluminum material. This instrumentation will certainly improve the maintenance of commercial aviation assets.


  1. Anastasi, R. F., Madaras, E. I., Seebo, J. P., Smith, S. W., Lomness, J. K., Hintze, P. E., Kammerer, C. C., Winfree, W. P., & Russell, R. W. (2007, April). Terahertz NDE application for corrosion detection and evaluation under shuttle tiles. In Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2007 (Vol. 6531, pp. 261-266). SPIE.
  2. Wilson, A., Vincent, P., McMahon, P., Muscat, R., Hayes, J., Solomon, M., Barber, R., & McConnell, A. (2008, December). A small, low-power, networked corrosion sensor suite. In Proceedings of the 2nd Asia-Pacific Workshop on Structural Health Monitoring, Corrosion, Melbourne, Australia (pp. 2-4).
  3. Hoen-Velterop, L. (2017, August 7–10). Assessing the corrosion environment severity helicopters encounterusing environmental sensors [Paper No. 2017-400177]. 2017 Department of Defense – Allied Nations Technical Corrosion Conference, Birmingham, AL, United States.

KEYWORDS: Nondestructive Inspection; NDI; Corrosion detection; aluminum formers; fastener corrosion; imaging corrosion; Al corrosion


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 24.1 SBIR BAA. Please see the official DoD Topic website at for any updates.

The DoD issued its Navy 24.1 SBIR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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Topic Q & A

1/16/24  Q. 1. Have you considered worked with or evaluated millimeter wave scanning as a modality for the applications described in the topic description? Does this approach have appeal, or known shortcomings for your desired application?
2. Where do you see the biggest failings in state-of-the-art NDE today for your application? The Navy seems to have invested in NDE for decades, yet we continue to see similar topics come up regularly.
3. Do you expect that a multi-modal inspection technology approach will likely lead to the optimal solution?
4. Is the same method of inspection expected to apply to both the aircraft landing gear and the aerial platform surfaces?
5. Should we infer that “robust operations under harsh maritime environmental conditions” means that inspections may be on-deck during rain in rough seas?
6. Can you offer a more specific example of a “fastener” in context (and what it might be fastening)? Is it merely a bolt or something more complicated? What direction does it go in relation to a background surface? What are the most common materials? Where would they be located on a maritime asset? Would a link to a picture be possible?
7. The topic mentions specifically aircraft landing gears. Is this the primary focus of the program? What other surfaces and inspection needs bear consideration?
8. Is access to the inspection site relatively open, or are we trying to peer into tight corners and spaces?
9. What is the nature of the coatings through which we would need to inspect? Are the surfaces exposed, painted, or coated? In some extreme cases we have worked a solution of looking through submarine hull treatments of substantial thickness.
10. Is aluminum the only metallic surface for which we need to be concerned with for corrosion, cracking, fracture, and damage? Is it even the highest priority relative to other metals on a maritime aircraft?
   A. (1) This SBIR is open to all types of detector technology. I cannot comment on the validity of your solution to this task. Please refer to the SBIR for more information.
(2) Please see (1)
(3) Please see (1)
(4) The emphasis on this data call is look at the structural elements of the airframe underneath the composite and paints.
(5) It is envision that this will be done at a depot.
(6) Use the Boeing 747 as an example of an air asset that you will be working with.
(7) Please see (4)
(8) No. This is meant to probe the structural elements without dissembling the aircraft.
(9) Please see (6)
(10) As mention we are interested in structural elements.
1/12/24  Q. In this sentense "The proposed method should also detect corrosion on fastener threads without the need for disassembly", Is the corrosion on the screw rod, and below the screw nut?
   A. All the above. We are looking for degradation of strength so whenever there is any non-idealized defect you should be able to detect it.
1/11/24  Q. Could you please clarify whether the emphasis in demonstrating the feasibility of the concept to detect hidden defects lies more on modeling the underlying physics of the technology approach or on the broader aspects related to the deployment of the technology into a NAVAIR maintenance environment?
   A. This is not a modeling exercise. We are looking for a hardware solution.
1/8/24  Q. Is it correct to interpret "in situ detection" to mean "while parked at an airfield," or does it mean "while inside a depot?"
   A. Insitu in this particular case means that it done at a depot. Depending upon the form factor the NDI can take place at a hangar or at an airfield .
1/7/24  Q. Will a primer coating that generates fluorescence upon corrosion to detect early stages of corrosion be of interest? The primer can be applied directly on the metal surface, and under the paint/polymer. Upon corrosion, a fluorescent signal will be emitted that can detected using a hand held tool
   A. The proposed solution maybe a good one for new aircraft or aircraft that is in remediation, but this solution needs to address the existing asset in the fleet.
17/24  Q. Will a primer coating that generates fluorescence upon corrosion to detect early stages of corrosion be of interest? The primer can potentially be applied under the paint/polymer.
   A. There is interest to develop new methods to detect and inhibit corrosion, but this data call is not asking for that right now.
1/5/24  Q. 1. In this sentence "The proposed solution should be able to detect fastener corrosion", what is the fastener diameter, how the fastener is installed or how far away is the corrosion from the surface where the sensor can access the fastener? Will you provide the geometry of the fastener structure?

2. Who will be the end user for this sensor, the Navy research lab or the Naval Aviation Maintenance team?
   A. (1) This tool is meant to be used on different aviation assets, so there is no one answer will satisfy the question. I have suggested to other inquiries to the use the Boeing 747 as the test case to derive their proposed solution. Since it would be difficult to get the PMA to release that information, it is better for the respondents to go directly to the source for the P8 platform.

(2)It is meant to help the maintainer to quickly assess the structural health of an air asset.
1/3/24  Q. Does the 12-lb limit include any mechanical guide systems or is it sufficient that the imaging system and its associated electronics be less than 12-lbs?
   A. In the initial phase 1, more emphasis should be placed on the detection technology. Keep in mind that this is a general purpose technology that examine most NAVAL air Asset.
12/29/23  Q. 1. Is it necessary to address both (a) early corrosion detection through paint/polymers, including 1st and 2nd layer corrosion at fasteners, and (b) corrosion on fastener threads without disassembly?
2. For detection of corrosion on fastener threads, what is the aluminum layer thickness range required and what is the fastener diameter range that must be addressed? Is it correct to assume this inspection must be done with the fasteners installed and under paint/polymer coating?
   A. (1) Yes.
(2)Yes. Vendors should use the Boeing 747 as the article they are designing an inspection tool toward. It is easier for the vendor to get a quicker response from Boeing as oppose to the PMA.

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