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  • #16
    deleted - just following the trend ...

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    • #17
      Originally posted by WILCO737 View Post
      Yes, there was such an accident with a DC10. But the problem was, that a hydraulic line was cut off as well during that engine separation and the slats retraced. And the slats are huge and effective on the DC10s. That's why it flipped over.
      What I know of the background of this is that in Georgia, mechanics were using forklifts to raise precariously balanced DC-10 engines for replacement on the wing. Apparently a forklift hit this plane and cracked something vital. I'm guessing that when this kind of maintenance is done with a hint of professionalism, the wing maintains its integrity and is built for the load with which it operates.

      Beyond that, I'm thinking some of those hydraulics were rerouted to put them out of harm's way.

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      • #18
        Well - the mechanics used one of two approved methods for removing and installing the wing engines in those DC-10-10s. American and Continental were using it (while United used a different method). There was nothing unproffesional about it. At that time, it was simply not known, that the method using the forklift - which supported the engine from below - caused hairline cracks in the engine pylon which eventually led to a pylon failing on an American DC-10-10 in 1977. After the accident, there were of course changes in the maintenance procedures.
        Unfortunately, that's how many accidents still happen - something unknown or unforeseeable occurs - and how accident investigation and prevention works - find out what caused it and eliminate that cause.

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        • #19
          Boeing built the 777-300ER with the capabilities for 330-minute ETOPS! That's over 5 hours from a suitable airstrip. I believe that would allow it to fly any route in the world as a twin. What is the limit now...240?

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          • #20
            Well - when it comes to ETOPS it is actually not a matter of capability but of regulations. Theoretically, any twin engined aircraft could fly on one engine, until the fuel on board is exhausted. I believe in the 777-300ER that is much more than 330 minutes

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            • #21
              delted, reposted, then deleted again.

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              • #22
                Originally posted by Peter Kesternich View Post
                Well - the mechanics used one of two approved methods for removing and installing the wing engines in those DC-10-10s. American and Continental were using it (while United used a different method). There was nothing unproffesional about it. At that time, it was simply not known, that the method using the forklift - which supported the engine from below - caused hairline cracks in the engine pylon which eventually led to a pylon failing on an American DC-10-10 in 1977. After the accident, there were of course changes in the maintenance procedures.
                Unfortunately, that's how many accidents still happen - something unknown or unforeseeable occurs - and how accident investigation and prevention works - find out what caused it and eliminate that cause.
                Not quite correct. American Airlines suffered quite a mauling over this one. This extract from the NTSB report....

                The pylon was damaged due to an incorrectly executed engine removal procedure. The correct procedure called for removal of the engine prior to the removal of the engine pylon. To save time and costs, American Airlines instructed its mechanics to remove the engine together with the pylon all at one time. A large forklift was used to hold the engine up while it was detached from the wing. During the procedure a crew shift change occurred, leaving the forklift unmonitored for a period of time. A problem in the fork lift's hydraulic system caused it to tilt the engine while still under the wing. This exerted enough pressure on the engine pylon to create a large indentation and a serious fracture in its body. The fracture went unnoticed for several flights, getting worse with each flight that the plane had taken. During flight 191's takeoff, enough force was generated to finally cause the pylon to fail. With the failure the left engine detached from under the wing and tore away. With the loss of the engine and the position of the slats, the plane was destined for disaster. The NTSB concluded that given the circumstances of the situation, the pilots were not in any way to blame for the resulting accident. The lead mechanic, who had performed the overhaul techniques, killed himself just hours before he was to give a deposition to the investigation.[3]

                This method of engine-pylon removal saved
                man hours and was encouraged despite the manufacturer issuing bulletins that specified how the procedure should have taken place. These were not binding. The accident investigation also concluded that the design of the pylon and adjacent surfaces made the parts difficult to service and prone to damage by maintenance crews.
                If it 'ain't broken........ Don't try to mend it !

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                • #23
                  Well - Brian - you are right and I read the report myself of course. But the problem was not the forklift, but removing and fitting the engine and pylon in one piece.
                  The post futher up implied (at least to me) that a couple of rogue mechanics simply slammed the engines on a forklift rather than doing a thorough job. I wanted to point out that they were following their company's procedures. Nothing more and nothing less. And if the maintenance bulletins MDD issued over this procedure was not binding then I believe the manufacturer didn't think of the procedure as very dangerous.
                  After all many airlines devise maintenance techniques that are safe and still more efficient than what the manufacturer says.

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                  • #24
                    Interesting commentary that the crack they caused managed to escape detection through multiple inspections. Those inspections weren't probably the best either. Sure, the maintenance crew shouldn't have CAUSED the crack, but what good is an inspection that misses a crack like this?

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                    • #25
                      Originally posted by Peter Kesternich View Post
                      Well - when it comes to ETOPS it is actually not a matter of capability but of regulations. Theoretically, any twin engined aircraft could fly on one engine, until the fuel on board is exhausted. I believe in the 777-300ER that is much more than 330 minutes
                      As I understand it, an extended ETOPS certificate is given on the basis of proven aircraft performance and operator performance history.

                      I think they mean capability in other design respects, including but not limited to engine reliability. To be rated ETOPS 330, you would have to provide for all emergencies that might require a five hour diversion—redundant systems failures, fire, medical emergency, decompression etc. It would mean you have to have complete capability to control and extinguish fire in flight, and deal with everything from major injuries to cardiac arrest to the degree that a victim can be stabilized to survive an additional five hours. I think that is what is in debate on extending beyond ETOPS 180.

                      I wonder if the push for higher ratings may be an attempt to cut costs by shutting down provisional facilities subsidized by Boeing and others in the industry.

                      But then, these things have nothing to do with the number of engines.

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                      • #26
                        A little hair-splitting AND I will not claim to be 100% accurate.

                        But, it used to be that 3 engines were required for extended, over-water passenger flight.

                        ETOPS operations require routing changes so that you are closer to emergency landing options.

                        So (and arguably), our rules and regulations consider two engines to have a very slight and ever-so-unacceptable risk that three engines do not.
                        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                        • #27
                          3WE,

                          The regulations that 3/4 engined aircraft were unlimited has gone. EDTO is replacing ETOPS, and so all aircraft are subject to the same considerations.

                          There is still, of course, consideration of engine failure, where the 3/4 eng will always win... but as has been identified... engines are no longer the limiting feature for extended range flights... hence the regulations require all aircraft to be assessed.

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                          • #28
                            Well, Evan - ETOPS stands for Extended-range Twin-engine Operational Performance Standards, so the question here is just how reliable is the remaining engine after one engine fails. All the other stuff (medical emergency, decompression, inflight fire, etc. etc.) has nothing to do with ETOPS. Those are things that could occur on any aircraft with any number of engines, and they don't factor into ETOPS certification

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                            • #29
                              Well, Evan - ETOPS stands for Extended-range Twin-engine Operational Performance Standards, so the question here is just how reliable is the remaining engine after one engine fails. All the other stuff (medical emergency, decompression, inflight fire, etc. etc.) has nothing to do with ETOPS. Those are things that could occur on any aircraft with any number of engines, and they don't factor into ETOPS certification
                              Where did you get that information? ETOPS greater than 180 minutes has always required those elements to be considered.

                              This is from the FAA Advisory Circular on ETOPS (120-42B).

                              "The distance between adequate alternate airports on the route in converted into time (minutes) computer for all engine cruise speed, as well as engine inoperative speed. The number of minutes cannot exceed the time-limited system certified capability (cargo fire supression and the other most limiting system) that is identified ... in the Aircraft Flight Manual..."

                              You might be also interested to know that within a year or two those elements will be required for ALL flights greater than 180 minutes, regardless of number of engines under the EDTO regulations.

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                              • #30
                                Well, MCM - would be nice to read the whole 74 pages of FAA AC 120-42B together and see what the details are As we might find out from the title of Chapter 2, Section 205, Sub-Section 2 "ETOPS Beyond 180 Minutes (Two-Engine Airplanes and All Passenger-Carrying Airplanes With More Than 2 Engines).", the requirements you just quoted apply to ALL passenger aircraft

                                What I wanted to say is that ANY aircraft can have a problem with a cargo hold fire and of course an A340 doesn't get a less strict certification when it comes to that just because it has 2 more engines than a A330. But when the A330 loses TWO engines in flight there are none left, while the A340 losing two engines in flight sill has to left to go. That's the point of limiting a twin jet from straying too far from a suitable airport. Authorities want to cut down the chances of the other engine quitting as well once the first one is gone

                                But rather than bombarding each other with bureaucratic texts, which anybody who is interested can read for themselves at faa.gov, I'd say we get back to what is really the point in this post: twin engines save the airlines money because they reduce operating costs, especially maintenance.
                                Last edited by Peter Kesternich; 2010-01-09, 10:55.

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