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Thread: Air Zimbabwe 767 Engine Surge, Tailpipe Flames, Mayday... Continues to Destination

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  1. #1
    Senior Member Evan's Avatar
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    Default Air Zimbabwe 767 Engine Surge, Tailpipe Flames, Mayday... Continues to Destination

    No harm, no foul?

    http://avherald.com/h?article=4c7467ca&opt=0


    So... question: is there an EGT threshold after which you must land asap?

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    I'd say the answer is a qualified "yes" but you missed a step.

    There's probably an EGT threshold above which the engine must be shut down. In that case you'd of course (in this aircraft) be flying single-engine which probably would mandate landing.

    There's a gray area I can picture: if the engine is damaged such that at a normal power setting the EGT is too high, but the EGT can be brought within limits by reducing the power. I'm not sure whether there's any specific guidance on whether to continue or terminate a flight in those circumstances. It seems like termination would be the safe choice, as if the engine is damaged, there may be things going on that that could cause it to fail completely later on.a
    Be alert! America needs more lerts.

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    Senior Member Evan's Avatar
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    Quote Originally Posted by elaw View Post
    I'd say the answer is a qualified "yes" but you missed a step.

    There's probably an EGT threshold above which the engine must be shut down. In that case you'd of course (in this aircraft) be flying single-engine which probably would mandate landing.

    There's a gray area I can picture: if the engine is damaged such that at a normal power setting the EGT is too high, but the EGT can be brought within limits by reducing the power. I'm not sure whether there's any specific guidance on whether to continue or terminate a flight in those circumstances. It seems like termination would be the safe choice, as if the engine is damaged, there may be things going on that that could cause it to fail completely later on.a
    I would think it would be as serious as a hot start on a turbine helicopter. That is generally understood to require a shut down and a subsequent teardown inspection before the engine can be considered airworthy again. So, if a twin-engine airliner experiences a very high EGT due to a prolonged engine surge (in this case 60-90 seconds of flame exiting the engine), even if it recovers it would be considered unsafe and, with only one engine considered safe, a return would be required.

    I just wonder if there is some written (or unwritten) rule, recommendation or policy about that.

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    Senior Member Gabriel's Avatar
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    ANy indication that the EGT was too high? The tailpipe fire can be unburned fuel burning when it gets out of the engine.

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    Senior Member Evan's Avatar
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    No, not directly, but the reports suggest this was a continuous surge of 1-2 minutes where axial flow would be disrupted but combustion wasn't and was thus flaming out the tailpipe and you would expect a high EGT indication as a result. There are AFM limits for EGT during a hot start so I would expect similar limits for a continuous surge in flight. AFAIK, EGT can rise about 5C per second during a minor surge to about 15C per second for an unrecoverable one. We're talking about 60-90 seconds here, and they recovered (or it self-recovered) and continued another 90 mins to destination despite being about 10mins from departure.

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    Senior Member Gabriel's Avatar
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    Quote Originally Posted by Evan View Post
    No, not directly, but the reports suggest this was a continuous surge of 1-2 minutes where axial flow would be disrupted but combustion wasn't and was thus flaming out the tailpipe and you would expect a high EGT indication as a result.
    I would expect high TIT.

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
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    Member ATLcrew's Avatar
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    Quote Originally Posted by Evan View Post
    AFAIK, EGT can rise about 5C per second during a minor surge to about 15C per second for an unrecoverable one.
    Source, please. I'm genuinely curious, never seen definitive numbers like that before.

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