Holy fatigue crack!! NTSB images of the failed 777 Pratt & Whitney engine

Discussion in 'General Discussion' started by Ivo, Feb 23, 2021.

  1. 23 Feb 2021 at 4:01 PM #21
    Chrisyboi

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    yeh when there’s a tear the blade would Have ripped off and disintegrated I’d imagine. The bits going down the bypass wouldn’t cause much of and issue but it doesn’t take much going down the core to destroy it.

    Has anyone else seen the footage where they were testing the effects of bird strikes to engines. They were lobbing raw chickens down the engine when it was running only the time on the video they forgot to defrost the chicken and it completely destroys the engine.
     
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  2. 23 Feb 2021 at 4:06 PM #22
    Chrisyboi

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    Here is a video of a bird strike test. As you can see the engines don’t react very well.

     
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  3. 23 Feb 2021 at 4:26 PM #23
    Rocketeer

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    I think this was a test of broken blade confinement test. The engine exploded but the casing kept everything confined within the unit itself. It’s more impressive in SLO MO! They’ve actually painted the blade with the explosive charge attached. Great video.
     
  4. 23 Feb 2021 at 4:28 PM #24
    Toffeeman

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    It makes me laugh to think that back in the day, the Royal Navy used to clean gas turbines by injecting walnut shells into the air flow at a very slow speed. I think some industries today still do for some applications.

    Now, the RN uses Compressor Cleaning Inhibitor Fluid or CCIF as it’s known in the industry.
     
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  5. 23 Feb 2021 at 4:31 PM #25
    Ivo

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    At the very least they have to run with a fair bit of rudder to stop the single engine from turning the plane in a wide arc. That will generate additional drag so the single engine would have additional load.
    Someone else mentioned having to drop to lower altitude to make it home on one engine. I'm not sure about that. Once you're up high you need less thrust due to the lower air density. As long as you can maintain air-speed and lift it may be better to stay up there.
    I've totally forgotten my brief aero lectures from uni though and happy to learn more.
     
    Last edited: Feb 23, 2021
  6. 23 Feb 2021 at 4:49 PM #26
    Rocketeer

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    The opposition of rudder only counteracts yaw. It doesn’t really turn the plane but helps more with balance. In fact, when coming in to land on finals, I only use rudder control to keep the plane straight & level which yaws the plane enough to keep on its correct flight path. Sometimes I have to drag it in with a touch of throttle! Great fun but hair raising. Ask any pilot!!
     
  7. 23 Feb 2021 at 5:08 PM #27
    Biggles

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    Rudder will be required but the drag created is a drop in the ocean compared to dragging a large diameter engine around.

    Re descending yes you will need to. You can’t maintain altitude on one engine, and airspeed will actually technically increase as you descend (presuming you’re flying at a Mach number). Aircraft have a OEI (one engine inoperative) service ceiling which will always be lower.

    The fact that density is so much less at high altitudes means that less thrust is produced, and less lift is produced too. You need to descend into thicker air, the procedure is called “driftdown”. The reason for flying high in the first place isn’t to produce more thrust but to burn less fuel.
     
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  8. 23 Feb 2021 at 5:13 PM #28
    Flapps

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    Maybe going back to basic training would help??!!......

     
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  9. 23 Feb 2021 at 5:17 PM #29
    Snowdog

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    Just to refer to https://forums.m3cutters.co.uk/threads/when-engines-go-pop.237281/ post 14 from yesterday. I don't think there's been wide coverage of this, but check that gash in the fuselage!
    I'm not sure how close that is to the centre tanks, but looks pretty close to me!
     
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  10. 23 Feb 2021 at 5:23 PM #30
    Ivo

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    That all makes sense! Deferring to your better knowledge!
     
  11. 23 Feb 2021 at 5:24 PM #31
    Rocketeer

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    Thank the flying instructor for asymmetric training he said you won’t ever need!!
     
  12. 23 Feb 2021 at 5:29 PM #32
    Biggles

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    Yeah it’s a decent gash, and not too far from centre tanks. My comment was really in relation to the statement about an uncontained failure on a twin engined aircraft. A fuel tank ruptured is no less ideal on a twin jet than a 4 engined aircraft.
     
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  13. 23 Feb 2021 at 5:41 PM #33
    Snowdog

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    Yeah I get you, no worries. I just thought a quick x-post might be interesting so folks reading this thread could see what a flying blade is capable of where the fuselage is concerned.

    I like your understated use of "no less ideal" haha!

    All in all this latest pair of incidents could be seen as quite fortuitous, and may have saved lives. It does raise the question as to how they will deal with the related 777s and possibly the 747s too, that have PW4000 kit.

    I don't know enough to assume that the FAA etc may just demand new blades being fitted, or if it may be a better option to stick another engine model on them. I know any of them cost millions apiece, and presume a transplant of non like for like isn't easy either, considering mounts, ancillaries and control systems. I guess the middle ground could be an intense regime of blade x-rays etc, but it's not come at an ideal time for Boeing at all.
     
  14. 23 Feb 2021 at 5:58 PM #34
    ChristianF

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    The Rolls Royce engines are designed to not fly apart like this even at full throttle.

    I remember seeing this video where RR deliberately blew a blade off at full throttle, it cost them nine million quid for one test.

    Video below.


     
  15. 23 Feb 2021 at 6:03 PM #35
    Biggles

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    All engines are designed with that aim, unfortunately it doesn’t always work out that way in reality, RR have failures like everyone else.

    Have a google of Qantas 32, that’s what an uncontained failure (that was an RR motor) can do to the systems on an aircraft. It was totally unprecedented having that many indications of failed systems at one time, no checklist could possibly cater for that, those boys did good!
     
  16. 23 Feb 2021 at 6:14 PM #36
    Snowdog

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    That's a very interesting video, not seen that before. I've wondered about the involved energy levels, just to try and quantify things - so hearing that description of a single blade carrying the force of a locomotive puts it into perspective!
    I recall the Quantas 32 incident too now, yeah that was some feat by that crew.

    If I ever fly again, I'll probably still relish the thought of an engine view seat though!
     
  17. 23 Feb 2021 at 6:34 PM #37
    gavinsan

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    Just got it :oops: :muttley:
     
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  18. 24 Feb 2021 at 12:07 AM #38
    holmefield

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    I work for an Aero engine maker in fan blade manufacture.

    All large blades are sort of hallow.

    They actually have a sort of plastic printed sheet inside the middle ( the vane) which after baking twisting and heating to a temp I'm not allowed to discuss, creates a hallow space with vanes created in the hallow for strength.

    All current Jet engines are Titanium, Carbon composition blades are in test/trial phases but all still have a leading edge made of Titanium to combat Bird / debris strikes and roots made of Titanium ( the bit that connects to the rotation shaft.

    Those 2 blades will have most probably had metal fetige cracks, tiny cracks that build up over time. Checks usually pick them up but nothing is 100%, we always try to achieve 100% but 99.999% is expected.

    The engine actually did its job of containing the other blades in the engine, complete engine set blade off are incredibly rare, the blades that snap tend to get sucked through the engine causing complete engine fail BUT the housing retain the blades from exiting the cowlings.

    The bits that flew off were cowling parts and debris that got sucked through the engine.
     
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  19. 24 Feb 2021 at 12:14 AM #39
    holmefield

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    Those tests have to be done to get type certification approval to fly. All test blades are made to 100% specs and then sensors attached to each blade prior to destination..

    I know the forces involved on detonation and its huge but incredibly rare these days due to the huge amount of work put into the production of each engine

    That's why each engine costs millions and millions
     
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  20. 24 Feb 2021 at 12:15 AM #40
    stuartk

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    I still wish that all aeroplanes had RR engines.

    It just reassures me when the same country that cannot produce a reliable car manufacture an engine that keeps 400+ people alive at 40000ft.
     
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