Aircraft Maintenance Technician Gut Check

The night all Hell broke loose. How one man’s hunch saved the lives of hundreds.

Learning to trust your senses.

By Michael Spinks

Have you ever had the funny feeling that something wasn’t just quite right? That certain something you just couldn’t put your finger on? A nagging thought at the back of your mind that you couldn’t quite reach or understand? You say, “Don’t ask me how. I just know something isn’t right about this situation”. Call it intuition, psychic, a sixth sense, a gut feeling, a hunch, whatever. The fact is, no matter what you call it, something is wrong and has raised a red flag warning to you. Wherever the feeling comes from, I say it’s mostly from experience, training and/or awareness of a particular situation or surroundings.

Let me tell you a true story about a near tragic accident that happened several years ago at a major passenger airline where I once worked.

Here’s the stage: A chilly autumn graveyard shift, line maintenance, the aircraft is a Boeing 767 and scheduled out the next morning. The flight is completely sold out and will be making a trip across the Atlantic to Paris. That evening, after the last flight of the day for the twin engine aircraft, an inbound pilot discrepancy reports an in-flight loss of oil from the number one, or left side engine. In a scene that is played out every night in aviation maintenance, mechanics or as they are called today, Aircraft Maintenance Technicians (AMT) crawl out of their beds to go to work while the rest of the world sleeps. This night would be no different or so they thought. The AMTs receive their assignments, grab their toolboxes and go to work on their airplanes.

The AMTs had replaced a seal on the number one engine’s integral drive generator, but the engine requires a high power run to confirm the repairs and check for leaks. Three AMTs taxi the aircraft to the run-up area and perform the checks. The engine passes all required checks and everything is within the parameters. Looking good so far for the aircraft to make the gate for an on-time departure. Time’s a tickin’. Except there’s one little nagging feeling one of the AMTs has.

Now this is where things get a bit more interesting. First of all, the engine passed the checks. There were no reportable anomalies. Second, there’s the fact that the aircraft has to make schedule, so add in the time pressure. It’s an international flight booked full of passengers so this adds to the anxiety. You get the picture. The pressure is on.

One AMT senses an unusual bit of vibration in the engine. He insists that additional high power engine runs should be accomplished. On the fourth engine run-up all hell breaks loose. At around 93% N1 RPM, an uncontained failure of the high pressure turbine stage one disk occurs. The engine violently explodes, sending shrapnel everywhere. Pieces puncture the left wing fuel tank. A fire erupts. A quick thinking AMT shuts down the engines and pulls the engine fire handle in an attempt to extinguish the fire. Another deploys the escape slide. They escape unharmed although extremely shaken. An emergency crew arrives and extinguishes the fire but not before the wing is virtually burned off the aircraft. The damage is beyond repair and the aircraft is a total loss.

Now imagine this. Had this AMT not paid attention to his “gut feeling” and let the circumstance and pressure issues drive his decision making process, think of the consequences. In Human Factors (HF) this is called ignoring a suspected hazard. The next time that particular engine on that particular aircraft was scheduled to be throttled to full power would have been that very morning, on take off, heading to Paris full of passengers!! The result would have been tragic.

Another aspect to note. The ensuing investigation into this incident certainly would have revealed the maintenance performed on the engine, the engine high power runs and the fact that it had initially passed the required checks. The aircraft technicians would have immediately been drug and alcohol tested, questioned, asked for a written statement regarding the way they performed the task and more than likely treated with suspicion. Everything would have been examined under the microscope of the investigative parties, as it should be. Things such as:

  • Were the correct maintenance manual and/or job procedure cards used,
  • Were the AMTs trained and qualified,
  • Were the cockpit protocols during taxi and run-up followed,
  • What was the wind speed and its direction during the engine run-up, and
  • What was the ambient temperature during engine run-up?

Everything leading up to and during the incident would have been reviewed. The flight data and cockpit voice recorders would have been analyzed. The slightest error or deviation from procedures would have been noted. The AMTs lives would have been no doubt turned upside-down. These are the responsibilities of the AMT. The consequences to AMTs for making errors could be quite serious including legal prosecution and jail time. It’s happened in the past. A good analogy would be if a doctor makes a mistake he or she has the potential to kill only one person at a time, whereas if an AMT makes a mistake they have the potential to kill hundreds at a time. As is usually the case, these AMTs had acted professionally, responsibly and appropriately. They had not made any mistakes.

In the weeks prior to this incident, these AMTs had attended an HF training course. In HF Theory accidents are caused by a series or chain of events. One of the elements or broad factors leading to human error is inappropriate responses. These have the potential to add a link to the chain of events in an incident or accident. Ignoring a suspected hazard falls under the category of inappropriate responses. One of the topics covered in the HF Training attended by these AMTs was “Situational Awareness”, i.e., learning to recognize one’s situation then acting on any “red flags” that arise. This is a safety net that can break the link in the chain of events. If appropriate action is taken by projecting what can potentially happen and having the strength of character to stand up under pressure, situations such as the one previously discussed can be avoided.  In other words, trust your gut and act accordingly. I would say the company’s return on investment for this training paid off handsomely.

In our business of aviation, especially maintenance and more specifically when we’re working on or around “live” aircraft, we cannot afford to ignore these “gut feelings”. If we do, we do it at our own risk or at the risk of others and the aircraft. Let’s face it, we’re not baking cookies. We are in a high risk venture where things can go wrong in a very bad way very quickly. When you sense something is wrong, stop what you’re doing, get a handle on your situation, your surroundings and what job you’re performing. In other words pay attention. Raise your situational awareness.

I am certain that most passengers who were scheduled to fly on the aircraft that morning were not happy their flight was canceled, disrupting their Paris vacations and inconveniencing them. Some may have become angry demanding compensation. Some probably stated they would never fly this airline again unaware that the airline’s fine and highly trained mechanics most certainly saved their lives. I would venture to say that even the flight crew was not pleased. What isn’t appreciated by most of the flying public and yes even some flight crews is these types of situations and decisions are routinely faced by AMTs throughout the airline industry all over the world. It’s just another day at the office. Such is the life of the unsung heroes of aviation maintenance. As they say in Paris, C’est la vie!

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Michael, well done! An article every engineer should read. As engineer one is often faced with the "boss" screaming and threatening on one side, and that nagging gut feel on the other. Whether being a Cessna 150 with solo pilot or an A380 packed to capacity, if it aint right it dont fly!

Posted by Bart Smit via LinkedIn

A very good story that puts a human face on a very important topic in the aviation industry, Human Factors. I wish I had learned of this during my Graduate school days. I couldn't think of a better way of illustrating the importance of HFACS in aviation maintenance. Thank you for sharing the story.

Reminds me of a cargo flight I had many years ago when I was still trying to scratch a living flying light aircraft. I was hauling freight in an old C-310. One night the airplane was bugging me. It took me most of the four and a half hours of my route to finally decide it was an unusual vibration. There were no engine anomalies that I could detect. I did a post-flight inspection of the aircraft, and did not find anything. There was nothing to squawk, but I did warn the pilot who had the next route and would be flying the aircraft in an hour or so of my suspicions that there was a weird and abnormal vibration.

I got a call from him an hour and a half later, asking me to grab the back up plane and come and get him. Half an hour into his flight, the cam drive gear fell off the cam. Fortunately, he was an excellent pilot and was able to make a SE ILS to near mins and land at an airport.

Moral of these stories, pay attention to your gut.


Posted by Kristin Winter via LinkedIn

An excellent article with several critical points to ponder in regards to both human factors and the responsibilities and stress that an aircraft mechanic faces. Well done Mike!

Posted by David Vandenbroeck via LinkedIn

A well-told story that puts a human face on a very important aviation industry topic, Human Factors. I wish I had learned of stories like these during my Graduate school days when doing presentations on Human Factors and HFACS was the norm. I couldn't think of a better way of illustrating the importance of HFACS in aviation maintenance operations. Thank you for sharing the story.

Posted by Kayode Fajingbesi via LinkedIn

This is an Outstanding article that every Tech should read. It emphasizes the point of always go with your gut feeling, even if it takes one more check. Great job.!

Excellent story! As a footnote, the NTSB recognized the outstanding actions by these three AMTs. I was privileged enough to participate in a ceremony lauding these inviduals for a job well done!

I would just like to add that the Airplane can be fixed and flown again, you can't do that with people.

Excellant article that brings each of us into the real world of aircraft mechanics. Your at the Top of Your Game, keep up the good work.

On Site QA Airworthiness Liaison, Taiwan.

One of the Best posts ever......