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

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  • #31
    Originally posted by Gabriel View Post
    Or he uses TIT instead. TIT is more important that EGT. EGT is a "byproduct" of TIT. Imagine the EGT in an F-14 with afterburner. But the TIT remains under control.
    No TIT on that family of aircraft either. In fact, I'm not aware of any jets that display TIT.

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    • #32
      Originally posted by ATLcrew View Post
      No TIT on that family of aircraft either. In fact, I'm not aware of any jets that display TIT.
      Amazing, given how we used to make such a big deal about them in the more humourous days.
      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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      • #33
        Originally posted by ATLcrew View Post
        No TIT on that family of aircraft either. In fact, I'm not aware of any jets that display TIT.
        II suppose it's like medical science, where a handful of vital signs are used to check for more serious conditions throughout the body. If your four primary engine vital signs are good, there's no need for more specific ones like TIT. If there is rise in TIT, that is going to show as a (albeit lower) rise in EGT, Correct me if I'm wrong, but the two cockpit indicators of a continuous engine surge are EPR and EGT. We were taliking about reducing complexity; well that seems like a pretty simple way to recognize the situation (unless, as I believe is the case for the plane you are currently flying, ECAM does that for you).

        But again, my question is, if you get a continuous (60-90 sec) surge on climb-out with a corresponding EGT redline, and then the surge self-corrects and the indicators return to normal, do you always return or is there a threshold below which it is considered permissible to continue to your destination? I'm asking because a hot start seems to have a shut-down/teardown requirement.

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        • #34
          Originally posted by Evan View Post
          because a hot start seems to have a shut-down/teardown requirement.
          Very interesting, but not correct! This is why you can't always depend on the internet for answers.

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          • #35
            Originally posted by BoeingBobby View Post
            Very interesting, but not correct! This is why you can't always depend on the internet for answers.
            Isn't this the internet?

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            • #36
              Originally posted by Evan View Post
              Isn't this the internet?
              I really should have known better!

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              • #37
                Originally posted by BoeingBobby View Post
                I really should have known better!
                The internet really has no idea as to where the limit lies with turbofans, which is why I'm asking the question here on the expertnet, but on turboshaft engines like the PT-6, the internet tells me a hot start often results in a costly hot section inspection before the engine is considered safe to return to service. So, I'm extrapolating: if the danger of compressor damage is that significant after a hot start on a turboshaft, isn't it also present on a large turbofan?

                Now, I realize with pneumatic starters and FADEC and no prop-feather drag, hot starts on turbofans are probably extremely rare, so I'm not surprised if you've never encountered one on a jet aircraft. I also realize that large turbofans are probably designed to be more robust than your typical turboshaft. But there has to be some EGT limit where even a turbofan will require an internal inspection before returning to service. I imagine that limit might also be reached during a full minute or more of recurring engine surge.

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                • #38
                  Originally posted by Evan View Post
                  ... the danger of compressor damage is that significant after a hot start ...
                  Compressor damage? EGT is in the opposite end.

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

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                  • #39
                    Originally posted by Gabriel View Post
                    Compressor damage? EGT is in the opposite end.
                    Sorry, combustor damage, turbine damage, damage.

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                    • #40
                      Originally posted by Evan View Post
                      Sorry, combustor damage, turbine damage, damage.
                      I'll tell you what's damaged...

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                      • #41
                        Originally posted by Evan View Post
                        ...PT-6...hot start...
                        What is a hot start and have you ever ridden a Jetstream-31?
                        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                        • #42
                          Originally posted by BoeingBobby View Post
                          I'll tell you what's damaged...
                          This thread. It started as a simple question but I guess nobody has an answer for me.

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                          • #43
                            Originally posted by Evan View Post
                            The internet really has no idea as to where the limit lies with turbofans, which is why I'm asking the question here on the expertnet, but on turboshaft engines like the PT-6, the internet tells me a hot start often results in a costly hot section inspection before the engine is considered safe to return to service. So, I'm extrapolating: if the danger of compressor damage is that significant after a hot start on a turboshaft, isn't it also present on a large turbofan?
                            The reason you haven't found a definitive answer on the internet is probably because there are too many variables. To wit, for us and our V2500-series engines, the red "tickmark" on the EGT display is OAT-dependent and is not automatically indicative of a hot start. It indicates only that MOC should be contacted. They have a whole set of parameters and limits that they will check against to determine whether a hot start has occurred (or even just an overtemp has occurred).

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                            • #44
                              Originally posted by 3WE View Post
                              What is a hot start and have you ever ridden a Jetstream-31?
                              I parked next to one a couple times.

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                              • #45
                                Originally posted by ATLcrew View Post
                                The reason you haven't found a definitive answer on the internet is probably because there are too many variables. To wit, for us and our V2500-series engines, the red "tickmark" on the EGT display is OAT-dependent and is not automatically indicative of a hot start. It indicates only that MOC should be contacted. They have a whole set of parameters and limits that they will check against to determine whether a hot start has occurred (or even just an overtemp has occurred).
                                But you have a digital temp readout as well, so you have an absolute value, right? (BTW, I'm NOT asking about hot start, that was just the precedent I based this on. I'm asking about an in-flight continuous surge) I was expecting some max exceedance value, after which the engine should be suspected damaged, left at idle and you should land asap. But I take it from your response that this value doesn't exist in any manual and it's simply left to pilot discretion. That surprises me. I wouldn't want to be sitting in 18F, watching a tail of flame for a minute and a half, followed by a resumed climb and a hot section blade to the skull five minutes later. I also wonder if FADEC will limit engine N1 after a serious overtemp event.

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