Bustamante: Borescoping is like having an eye at the end of a cable. NDT is being able to inspect something without changing the actual structure of what you’re inspecting. You have something that’s small enough to get inside small access areas like a screw hole that brings you inside of a frame. We have technology like articulation so you can navigate a cable through some pretty difficult small areas. With every type of instrument there is for NDT, nothing beats actually being able to see it. Whether it’s a video with a camera, or going more old school with a fiberscope, you see what you need to see. You can get a lot of tools to get you different readings, but in the end nothing beats having somebody looking at it.
AMT: What parts of the airframe and engine are best suited for RVI work?
O’Connor: Different airframes will have different requirements, but a sampling of items that are inspected using RVI include bell cranks, cable attachments, hose and wiring connections and condition, the inside of wing spars, and, with composite airframes, delamination inside composite panels. RVI is also helpful in reading component ID plates and serial numbers, checking for loose nuts or bolts, inspecting the compass compartment on larger aircraft, and for locating the source of fuel or other fluid leaks.
For piston-powered aircraft, a technician will inspect the inside of the cylinder to look for scorched pistons, cross-hatching on the combustion chamber walls, and valve condition.
With turbine-powered aircraft, RVI is used to inspect the turbine blades, nozzle guide vanes, and to look for any foreign object damage.
Kindred: The basic two most common things are inspecting turbine and compressor blades in engines and combustion chamber. When using RVI on the blades you’re looking for cracks from wear or impact. When inspecting a combustions chamber you’re looking for cracks, faulty fuel injectors, or anything that looks like it could be wrong. You use RVI so you don’t have to take the whole thing apart.
AMT: What are the “tricks of the trade” for using RVI tools effectively?
O’Connor: Keep in mind that modern RVI instruments are packed with electronics. A videoscope will not only have circuit boards and a power pack, but also a micro-camera, lens, articulation controls, and LEDs or fiberoptics for illumination. Accidents will happen, but dropping a videoscope from the horizontal stabilizer of a 757 has different implications than dropping a screwdriver from the same height. Treat the instruments kindly and they will provide years of trouble-free service.
When in doubt, take a picture. Videoscopes (and fiberscopes and borescopes if they have a camera attachment) allow you to capture images and video during an inspection. If there is any question as to whether or not there is a problem with the item you are inspecting, take a picture and get a second opinion. It is a lot easier to delete an image later than it is to go back and find the questionable area a second time.
When using guide tubes, if possible, place the instrument’s insertion tube through the guide tube before putting the guide tube into the inspection area.
During use, RVI instruments will often come into contact with fluids or debris. This is not a problem, but be sure to follow the manufacturer’s instructions when cleaning the instrument, especially the lens, prisms, or eyepiece.
Kindred: The key is to use the right product. Some guys will use whatever old scope they have laying around. Sometimes a rigid or flexible scope or a videoscope is the best tool. It’s best to have a full arsenal of good quality borescopes so you can use the right one for the application.
Bustamente: First of all is training, training, training — knowing your tool and having the experience of how to use it effectively. One person to the next might not use it the same. It’s kind of like a camera — like if you and Annie Liebowitz both took pictures, you aren’t going to take the same picture that she does. Learning the actual tool helps reduce cost and time.
Getting the best tool is also important. There are so many alternatives, especially with lots of lower end products, but just because they’re less expensive ... do you want to risk your inspection? A difference in quality equals a difference in confidence in your inspection, and especially on aircraft engines — those are the type of things where you need to see what you need to see to see if engine can still go. People’s lives depend on it.
So much RVI equipment is coming in from the low end has bare bones image quality. When we design we design for best image quality for the most confident inspection and decisions. Where do you really want to sacrifice?