Radiography: X Rays for Engine Innards

Every month, Eastern Air Lines had been stripping down, inspecting, and putting back together some 90 of the jet engines that power its planes—a five-day, $500 procedure for each engine. Now the price of that safety precaution is being reduced rapidly; Eastern has turned to atomic energy to check its engines’ hidden parts. Like doctors examining a patient’s bones and internal organs with X rays, mechanics are using radioisotopes to make internal engine pictures without taking the engines apart.

The technique was first used for examining welds and joints in everything from bridges to nuclear submarines. Then Technical Operations, Inc. of Burlington, Mass, helped Eastern solve the problem of getting radiographic equipment into the hollow rotor shaft of jet engines by using a 100-curie capsule of iridium 192 that is as small as a pencil eraser but emits gamma radiation powerful enough to pierce the engine’s metal innards.

The tiny radiation source is cranked 6 ft. into the shaft. A strip of industrial X-ray film wound around the engine is bombarded by the gamma rays streaming out from the isotope. The result is a detailed X-ray photograph of the hundreds of tough-to-get-at rotor blades that suck air into the engine, compress it and feed it to the combustion chambers.

What isotopic inspection does best is provide a clear picture of the rotor blades deepest inside the engine. These blades are the first to loosen and break free, and when this happens it may mean a complete engine overhaul at a price of $25,000 or more. “Using the isotopic inspection method,” says Eastern’s System Director of Quality Control Jason Koesy, “we’ve already caught 14 rotor blades that had begun to work their way loose.” Isotopic inspection, which costs as little as five hours and $20 per engine, has already saved Eastern more than $70,000 in maintenance costs. Other airlines are beginning to follow suit.