Aircraft Accidents and Gremlins

For Bugs Bunny’s many fans, the 1943 episode: Falling Hare, had the Gremlin, a fun character in that he is one of the few Warner Brothers characters to actually outwit the Brooklyn-ese speaking Bunny.  Designed to resemble a red-nosed, eyelid-drooping imp with wing-shaped ears and an aircraft tail … for his tail, the gremlin wreaked mechanical chaos with the Army-Air Force aircraft, as well as driving crazy said Bunny.

Gremlins were mischievous trouble-makers, discovered during World War II; they purposely sabotaged aircraft for non-political reasons, except, perhaps, for the fun of it.  They were the banes of aircraft mechanics everywhere, making first-age technology malfunction for confusing reasons.  If you don’t believe they exist, ask William Shatner’s character, Bob Wilson, from The Twilight Zone episode: Nightmare at 20,000 feet; Bob Wilson said, in reference to his airplane’s wing, “There’s a man out there.”

I’ve been reading up on what amount to ‘good’ gremlins: little robots that can be used inside the moving parts of a turbine engine, without the benefit of cracking open the engine case.  These little guys don’t resemble Bugs Bunny’s foil, yet they are designed to be small enough to fit into the incredibly small clearances of modern-day turbine engines.

To succumb to the inevitability of technical servants assuming all the skills of their human masters; it’s disturbing.  Making the aviation industry sit down and become aware of technical complacency is like trying to herd cats.  As I’ve written before, it concerns me that we continually trust the technology to solve all our problems and eliminate so much earned experience, e.g. driving our cars or piloting our aircraft, while we engage in texting or conversations about retirement.

I see Labor concerns with this technology.  Again, just like that mythical second officer that supposedly sat behind the Captain and First Officer in the airliner’s cockpit, jobs can and will be taken by, of all things … Robots.  How many man-hours or jobs will no longer be available because of our race to technological dependency?  But, I’m not trying to talk about Commerce.

It would be naiveté to dismiss all new technologies as a threat, in this age of micro-robots.  In its day, technological advances, e.g. the borescope (a flexible lighted wand), that can photograph or provide visual non-destructive inspection (NDI), was the advanced technology for inspecting the inside of a turbine engine; indeed, even the modern jet engine itself, is light years ahead of its older siblings.  But even as one studies the difference between the jet engines used on the B707 as compared to evolved versions used on the later B737 and lastly the B757, the advancements are off-the-charts revolutionary.  But, they also represent that surrender of control.

Chief Scientist Dr. Don Lipkin of GE Global Research, along with his associates Todd Danko and Kori MacDonald, have developed these micro-robots with the intention of utilizing them on jet engines.  This is an incredibly beneficial technology, make no mistake.  The usage is limited now to visual inspection, but there are plans to evolve the robots to conduct repairs.  One must understand, that to effectively inspect a jet engine ‘on-the-wing’ requires access to internal components with clearances of micrometers instead of meters.  Once inside, the robot must maneuver its camera to record images in an area too small for a borescope.

Riding a plastic track, the robots are inserted into the aircraft turbine engine.  They lock onto a set of rotating blades and are spun past the static blades – stator blades – taking pictures; this gives the inspector with a laptop a front row view of the compressor blades.  Other robot versions use magnetic wheels to crawl into the engine and place themselves into an optimum position to get the best inspection view.

In contrast, when employing a borescope, several plugs are removed from the engine casing.  A borescope’s telescoping wand is inserted through the holes and the compressor section is rotated past the scope.  The scope is only limited by its inflexibility; the wand cannot make 180 degree turns in so small a space.  If the inspection cannot be done adequately, the engine must be removed and the casing opened for a more complete visual.  This costs airlines money and time; replacement engines must be provided, man-hours performed and money spent.

Delta Airlines flight 1288 in Pensacola, Florida, July 6, 1996; United Airlines flight 232, Sioux City airport, Iowa, July 19, 1989; and American Airlines flight 383, in Chicago airport, Illinois, October 28, 2016; if a better means of visual inspection were available, these accidents may have been prevented.

This inspection method is considered NDI; the time to conduct the inspection is reduced considerably by using the robots.  As a result, less man-hours are utilized; less personnel to conduct the inspection; and more time the engine is spent ‘on-the-wing’.

It is planned to equip the robots to effect repairs in these tight places, meaning the robots can be utilized during an aircraft’s ground time on the gate.  The ability to make repairs in the confined space of a Compressor section may be, to me, pushing the safety limit beyond its technology.  And this is where someone must delay the technology, or in Bugs Bunny speak, “Apply the air brakes.”  For example, let’s look at one straightforward engine repair job: Blade Blending – a means of filing down damage to a blade.  Blade blending is an allowable procedure, in some instances, depending on where the blade is damaged, e.g. at the tip, or the base and how much material can be blended.  Blending is a minor repair I’ve made countless times; limits are intentionally made for safety.  Although not labor-intensive, the repair can be done wrong or the pre-repair damage can be too extensive, resulting in, and including, blade replacement.

Without the ability to closely inspect the repair, one could induce a hairline crack or burr that could propagate into a complete blade failure, which probably doesn’t sound as bad as it really is.  Imagine, however, a compressor blade breaking free from inside the compressor section as the engine is spinning at 3600 rotations per minute; the engine could suffer further catastrophic damage, including an out-of-balance condition; all this could occur before the pilots could react to the emergency.  With International flights being what they are, this could take place over the ocean, three-plus hours away from a suitable airport.

This is all conjecture; this type of damage may never occur.  However, with parts rotating at such incredible speeds and operating in extreme temperatures that would themselves contribute to failure, perhaps the purposes of the micro-robots should never exceed inspection.  It is my feeling – and experience – that if damage is discovered, then the engine should be split, the parts repaired or replaced under controlled conditions.  It is a useful technology, if only used to its proper degree – no more.

So, when does good technology turn into a gremlin, a force that can destroy instead of help?  When we exceed the design of the technology, hold it to a higher standard than it should be held to.  Kind of like the countless technologies we have become too reliant on.  And, unfortunately, unlike with Bugs Bunny, air brakes don’t work.

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