Air crash investigation alike: RA-85763 - miracle landing

Discussion in 'General Discussion Forum' started by Fins, Jan 18, 2018.

  1. Fins

    Fins It Wandered In From the Wastes

    Dec 31, 2017
    I'm sure many people here know about famous "Air Crash Investigation" series. Here's one more story of this kind - untold story of one pilot's amazing skills, one crew's amazing professionalism, and one ground service's untold stupidity.

    RA-85763 was one Tu-154 passenger liner, recently scrapped for its age (a shame, really, given this story). The story itself is the result of my translation of official black boxes investigation. The video is based on black box data and the audio is from the flight's voice recorder.

    January 12, 2000. Night time. Problems started when the plane was closing to its destination - Novosibirsk, Russia, when the plane started its descent from its cruise altitude of 10600 meters. Standard procedure involves reducing throttle to low when descending to land, so they did. By the time they reached ~10100 meters, however, the crew observed abnormal behaviour of engines' RPMs in engines #1 and #3, with were fluctuating much more than it should once throttle was reduced to low. There was also indication of engine 1's generator stopping dead. Pilots then increased throttle a bit, and that removed both problems - for the time being.

    They descended down to ~700 meters altitude, opened their flaps, released their gear, and made two of the last 4 turns before planned landing - all without an issue. Then, to slow down enough before the 3rd turn, they had to reduce the throttle low enough - but after doing that, plane's 2nd (middle) engine just stopped dead, by that time they had 640 meters of altitude. The crew notifies the tower about it, then proceeds to land using remaining two operating engines. The plane's perfectly able to land using only two engines, but it was only the start of their problems.

    Doing the last, 4th turn, the crew still did not see the runway - night time and weather did not allow it. So they were using their instruments. Yet at this time, instrument responsible for displaying heading started to behave strange: the dial was moving somewhat faster than the crew expected it to based on how quickly they were turning the plane. And indeed, whole system malfunctioned. The crew still did not have any visual contact and so it was decided to follow the instruments until visual contact with the runway could be established.

    They got visual contact at ~5500 meters from the start of the illuminated runway, flying at altitude of 270 meters. It is then they found they are flying to very wrong heading, aiming ~25° to the left of the runway. Seeing this, the captain decides to abort the approach and do another. The tower also established visual contact, and ordered another approach pretty much in the same time.

    Seconds later, the plane's engine #3 shuts down.

    They had no speed, no altitude, two dead engines out of three. Any experienced pilot knows that if you got two engines dying on you in short order, then it's likely the 3rd will stop as well, and very soon.

    On the other hand, the plane was not lined up with the runway, and very little distance remained to it. Doing low-altitude energetic turns while flying with assimetrical engine thrust is not exactly safe, either - when you're flying an airliner which can transport up to 180 passengers and weighs some ~70 tons, that is.

    In this situation, the captain (names Mikhail Dolgov) - decides that trying to go up and attempt another approach is one greater risk. So he cancels his own decision to do it, he violates tower's order to do it, and instead he proceeds to land the plane manually.

    And in doing so, he saves lives of everyone on board. Plane's #1 engine stopped when the plane was over the runway, 9 meters altitude. Still, the plane landed safely, touching down some 1200 meters into the runway - the captain was mindful about losing his last engine before the runway starts, so he maintained a bit of extra altitude before landing, to be safer; he crossed the start of he runway at some ~100 meters altitude.

    Having no engine power whatsoever, the plane was unable to apply reverse thrust. The crew used emergency braking procedure, and burned all 12 of the plane's brakes into dust, even drifting a little before stopping the plane. Still, the plane stopped some 600 meters before the end of the runway, taking no damage otherwise.

    Here's the video of this landing, with crew's voices from flight's voice recorder. Skip to 0:15.



    One little detail. Shortly before the plane stops completely, the captain already radios in one completely calm voice to the tower: "Send us a tug, please. Tug, please". Obviously you can't taxi anywhere without any engine power, you see. The tower answers, rather shocked: "I don't get it, repeat". The captain: "A tug, a tug". Only then the tower radios they copy, and tells the crew to wait for the tug. Point is - what an amazing captain! Even after such a difficult landing, he still thinks about his duty to bring everyone to the ground safely - and that includes removing the plane from the runway, ASAP, to prevent any risk of other plane colliding with his. So the 1st thing he does once he's 100% sure the plane is not going outta the runway? Request a tug. Not telling the tower he got dead engines; not getting emotional; just request the dam tug, calmly and clearly. I wish every pilot would be that solid!

    So, how could it happen? A plane with decades of quite reliable record having all 3 engines fail - is one very unusual occasion.

    Full-scale official investigation was launched. They found the cause, not right away, but they did. Long story short, turns out, two landings prior to this one, the plane was fueled by contaminated fuel. ~15 tons of fuel came into its tanks during its stop in Krasnodar, which is pretty much on the other side of the country. In particular, some of that fuel amount - came in from one fuel transporter which had insides of its cistern covered by approved anti-corrosion compound, except the guy who did the job of applying it - violated proper technology. It was routine repair procedure of an old fuel transporter, and still it almost downed an airliner.

    His error was that he didn't apply one required by the technology extra "grounding" compound layer, which must be applied directly to the steel of the cistern before applying anti-corrosion layer itself. It is required to ensure firm adhesion and proper crystallization of anti-corrosion layer. It was simply absent, as investigators eventually found by finding and inspecting that particular fuel transporter.

    This resulted in slow dissolution of anti-corrosion compound. Chemicals from that compound got progessively dissolved into the fuel. The RA-85763 flight then got fueled by that contaminated fuel, which later on gradually clogged the plane's fuel filters and valves. When technicians were disassembling the plane's engines after this incident - they had to use hammers to strike fuel valves out, as they were completely stuck and fixed with solidified chemicals from that anti-corrosion compound. Plane's fuel filters were all covered with same solidified mess. Said fuel transporter had lots of its anti-corrosion protection inside its cistern completely dissolved, upon followed inspection. Some of that compound slowly reacted with fuel components, ended up shutting the plane's engines down. When investigators got to see the remaining fuel of the flight, - they were shocked to see it was not liquid, but more like some sort of gel.

    It was determined, also, that another amount of fuel with excessive (but not dangerous in itself) levels of certain fuel additive was added to the plane's fuel tanks during its next stop (directly before this landing). Combination of the two is deemed responsible for what happened in this flight.

    It's still not clear what caused malfunction of heading indicator and plane's avionics in general, but personally, i suspect this is related to abnormal RPM fluctuations in engines and following malfunctions of engine #1's generator. After all, electrical systems get their voltage from engines, and when engines work abnormally for significant time, it's quite possible eletrics will also glitch, too.

    Based on the results of the official investigation, certain steps were taken to prevent similar cases in the future: new procedures to control corresponding ground maintenance practices, new aviation fuel quality control procedures at the planes' fuel tanks' entrance point, removal of this particular anti-corrosion compound from the list of allowed ones to be used for fuel transporters, and other safety measures.

    The crew of four - all got government decorations for performing above and beyond normal duty during this flight, awarded to them by the country's president's Order #706, in 2002. In particular, flight's captain Mikhail Dolgov was awarded one very high decoration - the Order of Courage, which few if any civilian pilots were ever awarded.

    ~&~

    It's quite the miracle the plane's engines did not fail, say, some 30 minutes earlier - in which case, given extreme scarcity of fitting air fields in that part of the country, the flight had every chance to end up crashing into forests which cover most of lands in that part of the globe, killing most or all people on board. It feels like not only heroic crew, but also the plane itself "decided" that nobody's going to die that day, and managed to stay "alive" exactly as much as was needed to allow it - if barely.

    I hope one day we'll see official Air Crash Investigation on this one. But for now, this is pretty much as much cover of the incident as there can be found in english, i think.
     
    Last edited: Jan 18, 2018