Emirates Boeing 777 crash lands at Dubai... - Page 4





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  1. #61
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    Default Re: Emirates Boeing 777 crash lands at Dubai...

    I have now read almost everything on here.

    My point of view is that 12 seconds was a long time to realise you don't have power.
    Captain was very recently upgraded into the left seat. Not saying it's his fault as PF should have noticed no power and PM should have doubled checked.

    I agree with Hugo on wheels up asap but it is standard to not reconfigure during windshear. It's SOPS almost everywhere.

    Possibility of pilots having a long day could also have had a big influence on human performance. Emirates pilots are over worked. I have had friends recently resign because of it. Emirates is currently short crewed by 400 pilots. They are parking A380's in France from the factory because they can't crew them. A good friend on mine flying for Ethiopian (resigned from Emirates 6 months ago) said they are close to a major incident due to crew fatigue.
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  2. #62
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    Default Re: Emirates Boeing 777 crash lands at Dubai...

    Quote Originally Posted by Barend D View Post
    ...but it is standard to not reconfigure during windshear. It's SOPS almost everywhere.
    In this case it would have been a good thing to do so, however strictly speaking SOPs based on the manufacturer's recommendations of similar aircraft types only require the pilots to NOT change configuration in case of a windshear WARNING. The EGPWS (enhanced ground proximity warning system) would under certain circumstances activate a warning, e.g. a synthetic voice call out "WINDSHEAR, WINDSHEAR!" in combination with red master warning lights, a red EICAS message and a red WINDSHEAR message on the PFD. For this, certain factors have to be present, e.g. a certain rate of change in wind speed has to be exceeded and, importantly, to my knowledge, the WARNING only gets triggered once a NEGATIVE windshear as in a change from headwind to tailwind or a rapidly increasing tailwind component is detected. But according to the script the wind change was a positive one, changing from a tailwind to a headwind. In addition, the rate of change was not enough to have the EGPWS trigger even a windshear caution. A windshear CAUTION gets triggered once a positive windshear is detected (like in this case, a change from tail- to headwind or a rapidly increasing headwind component), which could result in a voice message "CAUTION, WINDSHEAR", a master caution light and an amber windshear message on PFD and EICAS. I would have to dive into the books in order to be able to say whether these Windshear warnings and cautions would be suppressed after touchdown, but I think that is the case.
    In general, a windshear warning would be cause for either a mandatory go-around, leaving the configuration of flaps & landing gear unchanged while still airborne or a rejected take-off before reaching the decision speed V1.
    A windshear caution leaves it pretty much up to the pilots, as to what actions to take. Depending on the situation, a go around might be a good idea, since a micro burst would often manifest itself first by a positive windshear (rapid increase in headwind component), which is then very suddenly followed by a massive downdraft and a negative windshear (rapidly increasing tailwind). However, according to the books, a windshear caution does NOT require the crew to leave the aircraft configuration unchanged. E.G. approaching Cape Town from the south with a north westerly wind one might encounter a positive windshear on short final approach, caused by the table mountain. This would not necessarily be followed by a negative windshear. It is then up to the crew to use their split second judgement and local knowledge to decide to either abort the landing or continue to land.

    In this specific case, there is no mention of any windshear caution nor warning and I would like to believe the Captain's decision to perform a go around might have been based on the aural message "LONG LANDING" and the fact that the aircraft had floated for some distance and the nose landing gear hadn't settled yet, rather than thinking about the root cause, what might have been a mild windshear.

    As to 12 seconds being a long time for the crew not to realize that the engines where still at idle: yes, I fully agree, BUT these Rolls Royce Trent engines are notorious for being very slow to spool up. They are massive engines and they are of a unique triple spool design. While most high bypass turbofan engines have a low- and a high pressure spool, the RR Trent have a low-, medium- and high pressure spool. By regulation, any jet engine must be able to spool up from (flight-) idle to max thrust within 8 seconds, if I am not mistaking. In order to achieve that jet engines have an increased idle state, called flight idle. While airborne, idle thrust is higher, in other words closer to max thrust, in order to reduce the spool up time and comply with regulations.
    In this specific case however, the aircraft had already touched down and the autothrottle had reduced the thrust to idle. Depending on the B777 specific systems, this short time on ground, or "weight on wheels" might have been enough to trigger ground idle on the engines, a significantly lower idle power used for the landing roll out and taxiing. If this was the case, it would be natural for the engines to take a lot more time to spool up again to take-off / go around thrust and the crew sort of anticipated the thrust to come in "any second now". To give you an idea, on the A330 it takes the (slightly smaller version) RR Trent engines about 20 seconds to spool up from ground idle to take off thrust, by which time the aircraft has already reached 60 knots.
    Last edited by HugoNotte; 2016/09/08 at 05:10 PM.
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