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Neutron Radioscopy Inspection of Composite Flight Control Surfaces

L.G.I. Bennett, W.S. Lewis, T.R. Chalovich, O. Fransescone
Department of Chemistry and Chemical Engineering
Royal Military College of Canada
Kingston, Ontario, Canada.






Although clearer in the actual images, what are visible are the aluminium main spar, shown horizontally at the bottom with the hinge support and steel anchor nuts underneath. Above is excess adhesive, water in the honeycomb and the imaged adhesive in a honeycomb pattern.

(a) no enhancements (b) basic enhancements (c) advanced enhancements
Fig 5: Sequence of Images of a CF188 Rudder.

Although not visible in the first image (a) in the Figure, there are some white spots indicating gamma contamination or system noise. Figure 5(b) has very little definition, as some of the individual components are not clearly distinguishable, but water is indicated, as is the hinge assembly. Water ingress and its location were previously known from neutron radiography. In Figure 5 (b) and (c), water ingress is visible and the pattern of water is identical to known images of this area. Figure 5 (c) also indicates clearer details such as the main spar, porous adhesive and the anchor nuts.

The histogram associated with the original image, Figure 5 (a) is shown in Figure 6. Thresholding was applied to the image to identify the features related to the curve and are indicated.

Fig 6: Histogram of the Original Exposure of Figure 5 (a).

The intensity values of the graph in Figure 6 are in the low thousands and therefore the original image is totally black as previously seen in Figure 5 (a). The intensity values have a small range, from 1536 to approximately 3500, which is only 3% of the total number of intensity values available. This small intensity range produced an image with a small dynamic range, which reduced image contrast between components as shown in Figure 5 (b). However, all of the expected features are present in the histogram. Thus, since the different items, such as water, have a characteristic location, a histogram may be considered as another means of identifying the presence of water.



  1. American Society for Testing and Materials (1996) Standard Practices for Thermal Radiography of Materials ASTM E748-95
  2. United States Air Force Sacramento Air Logistics Center (1995) Non-destructive Inspection Report Canadian Forces CF-18A McClellan Air Force Base, California
  3. DCIEM Report No 98-TM-44 (1998) Progress in the Non-destructive Evaluation of CF-18 Composite Flight Controls for Water Ingress and Related Damage DCIEM Air Vehicle Research Detachment, Ottawa, Ontario
  4. Bickerton, M. (1998) Development of Improved Techniques for the Neutron Radiography of CF188 Flight Control Surfaces M.Eng. thesis, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston Ontario
  5. Chalovich, T.R. (2000) Development of Neutron Radioscopy at the SLOWPOKE-2 Facility at RMC for the Inspection of CF188 Flight Control Surfaces M.Eng. thesis, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, Ontario

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