How ONE NUT Saved 25 People | Danish Air Transport Flight 54

This is the story of Danish air transport flight 54. On the 31st of january 2005 a crew started their day. On that day their day was packed they had to fly multiple hops. By about 11 am had already flown between floro and bergen. Now they were getting ready to fly another trip to floro from bergen. On the ground the pilots tested out the rudder and the ailerons just to make sure that everything was working, the first officer put the elevator through its full range of motion. It was a bit stiffer than usual. He associated that to the wind that day and didn't think too much of it. When youre on the ground the wind can push up against the elevator giving it a bit of stiffness its nothing to be concerned about and so they taxied to the runway. The ATR 42 lined up with runway 35 and flight 54 started the takeoff roll at 11:28 am. The plane accelerated and within minutes the pilots were ready to takeoff. But as the captain pulled back on the stick he noted that he needed more force than usual to takeoff. His mind raced and he thought that he had set the trim incorrectly for takeoff. But as the plane climbed away from floro they both knew that that wasn't the case. Something was wrong with their plane. In the cockpit the pilots were struggling to keep their plane under control. Both pilots wrestled with the controls just to keep the plane stable. The elevator was now moving in an uneven fashion, completely different from what they had observed on the ground. The captain didnt even bother turning the autopilot on as he knew that it would disengage. At 11:29 am flight 54 was 3 nm north of the airport and they were at 2000 feet. They needed to land as soon as possible and so the pilots put out a mayday.The approach controller at flesland put the plane on a westerly course guiding it back to runway 35 and asked them to climb to 3000 feet. They needed to climb as there was some terrain in the area that they had to clear before they turned south. As they turned the captain could see the runway. The controller cleared the plane for a left downwind approach to runway 35. The pilots told the controller about their control issues and asked the airport to have emergency vehicles on stand by. Within minutes the airport had fire trucks near the runway. By now the controllability issues had eased up a bit but the pilots lined the atr with the runway. I wonder what the pilots must have been thinking at that point. They were so close to their destination. 7 minutes after takeoff flight 54 landed back at floro. When the plane was back on the ground the captain asked the cabin crew member how the cabin was throughout the incident. Apparently in the cabin things were fine. No one in the cabin knew how serious the incident was. After they had landed the pilots decided to inspect the plane. This is what they saw, the source of their troubles. The right hand elevator had mostly separated from the stabilizer. Three bolts and hinges were supposed to hold the elevator to the stabilizer and of that only one hinge was intact. I guess you could say that their success hinged on that one intact bolt. See what i did there? You know what, never mind. Considering what had happened the airport sent a car down the runway to see just to inspect the runway and there on the runway right on the centerline they found a bolt and washer on the centerline. They ran the serial number of the bolt, it had come from flight 54. First lets look at what the elevator actually does. The elevator is attached to the horizontal stabilizer and controls the pitch of the plane. Basically the captain controls the left elevator and the first officer controls the right one. Basically three hinges connect the elevator to the stabilzer. This picture shows the top down view of one of these hinges. You basically line the holes in the elevator and the stabilizer up and you put a bolt right through the middle. Inside this contraption there are a few ball bearings that can move. When those bearings move in on the bolt the hinge is tightened. They constrict the bolt in a way keeping it in place. When technicians looked at the plane, they found that two of the three bolts had been compromised. This plane was able to land back safely only because that one bolt had not failed. Had it cracked, this story would have ended very differently. But why had the bolts fallen off? Why had the hinge failed? The investigators dug through the history of the plane to see if this elevator had been worked on in the recent past. They kept going back and they saw that in 1999 this plane had some serious maintenance done on it. It was repainted and the elevator was refitted. It appeared that the technicians who put this plane back together had not tightened the bolts all the way through.These bolts are not put under enough stresses for them to become loose. Basically you need a rotational force to loosen this bolt and they just were not subjected to any force of that sort during their operational lifetime. The only explanation was that they hadnt tightened the bolts properly 6 years ago. Looking at the bolts closely they found more evidence to the fact that they had not been properly tightened when they were put back in all those years ago. There was wear on the surface of both bolts that indicated that they were rattling around in there for years and years. The bolt that didn't fail did not show wear of this nature as it was tightened properly. In addition to that the holes of the bolts that failed was corroded which meant that water was getting into the gap between the bolt and the bolt hole, this would not have happened if the bolt had been properly installed. What's more interesting is that the bolt in the center had fallen out a long time ago. In fact this area had been lubricated after the center bolt had fallen out because they found grease inside the bolt hole. This would not have happened if the bolt was in place. So at that point the center one was the only bolt that had fallen out. Then on the 31st of january 2005 the right most bolt failed causing the elevator to separate. Why this happened is hard to investigate as the company that did the modifications no longer existed remember this flaw was 6 years old. But the Norwegian investigators were still able to find a few issues with how maintenance was done. In the case of flight 54 when the maintenance was done it was probably seen as a very simple repair no one really considered it to be a very critical repair you take something off put it back on easy peasy and that exactly is the problem there's no central authority deciding what constitutes a critical repair and what doesn't. If a repair is classified as a critical repair then someone else will inspect the work done and that gives them the opportunity to catch mistakes. This would have saved a lot of planes to be honest. Think of dart 21, the plane that caught on fire because someone wired the plane up incorrectly. If someone else went through the modification then they might have caught the error. But the thing is maintenance is done by different companies. Some companies will see this as a critical repair and some won't so the Norwegian investigators think that maintenance inspections could be standardized to an extent if the manufacturer could say which repair is critical and which isn't. That way the same practices will be followed no matter where you decide to get your plane maintained and mistakes like this will be caught. Now before we wrap up we need to talk about one more thing. On that morning as they were about to take off , a bolt was about to fall off as they took off but that wasnt known to them . these guys did an elevator check before they took off the problem was that this check had become so routine that their minds ignored information that didn't fit the usual narrative. This is called conformation bias. Out minds look for patterns or data points to validate our preexisting notions. In this case they felt that the elevator was fine because it always was. They've done this check 100s of times and it's never given them any trouble. So when they felt something out of the ordinary, that is the stiffer elevators. they explained it away using the winds. So no one really went out to check. But then again they had no reason to suspect a flaw as this plane had been flying perfectly that day. In addition to that this crew showed excellent judgement when they declared the emergency when they did. They didn't wait for the situation to deteriorate to the point where they couldn't recover from it and that's probably why they were able to keep the plane under control. Its truly amazing how little it takes to precipitate an emergency, just two tiny bolts that's all it took and what's even more interesting is how long this flaw remained undetected. This near accident drives home the role maintenance plays in aviation. The responsibility of a successful maintenance job is shared between the maintenance company and the operator, the operator should be able to define what work should be carried out and to what standard and the maintenance company should be the one that executes that in the safest way possible as the slightest mistake can bring down a jet. Maybe not today, maybe not tomorrow but someday years from now. But i want to hear from you tho, How do you think this would have ended if that one final bolt had failed? No matter what these guys had a very close call and I wonder if the passengers ever got to know how close they came to disaster.

Channel: Mini Air Crash Investigation

Views: 156,711

Keywords: air crash investigation, air crash confidential, mentour pilot, atr, atr crash, atr 42 crash, why planes crash, how one nut saved this plane from crashing, aviation safety, theflightchannel, air crash, mayday, air crash norway, air crash denmark, denmark, norway, emergency landings, runway, tail failure, plane failure, danish air transport, danish air transport flight 54, plane safety, flight simulator, documentary, educational

Id: 9NUl46y2OJ4

Length: 11min 18sec (678 seconds)

Published: Wed Dec 15 2021