Originally posted by 3WE
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Emirates 777 crash-landed in Dubai
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You're talking about a different scenario.
During takeoff or landing, you can generally feel when the wheels depart or return to the ground. But in this case the aircraft was airborne and presumably they expected it to stay that way so the gear contacting or leaving the ground would not be in consideration.Be alert! America needs more lerts.
Eric Law
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Originally posted by elaw View PostYou're talking about a different scenario.
During takeoff or landing, you can generally feel when the wheels depart or return to the ground. But in this case the aircraft was airborne and presumably they expected it to stay that way so the gear contacting or leaving the ground would not be in consideration.
However, why be in a hurry to get the gear up? There is more drag from a gear in transit then gear down. The doors opening and closing are way more drag than just the gear hanging down and locked. Also, the positive rate call SHOULD be made when not only the VSI is showing a climb, but also the altimeter is showing one as well.
Can you say density altitude?
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Originally posted by BoeingBobby View PostHowever, why be in a hurry to get the gear up?
Then some folks say that go-arounds are critical maneuvers and that altitude is your friend, so you should not doddle getting the plane cleaned up.
And other's say it's so important to train for these checklists over and over and over.
Throw in the classic startle factor and I can see a good intentioned FO zooming through checklist items wanting to promptly establish a 'high-performance' climb.
Indeed, this contrasts with lighting up a cigarette and pondering the situation before touching anything.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by 3WE View PostI am generally impressed at how quickly airline guys run checklists. Extremely fast, efficient and accurate.
Then some folks say that go-arounds are critical maneuvers and that altitude is your friend, so you should not doddle getting the plane cleaned up.
And other's say it's so important to train for these checklists over and over and over.
Throw in the classic startle factor and I can see a good intentioned FO zooming through checklist items wanting to promptly establish a 'high-performance' climb.
Indeed, this contrasts with lighting up a cigarette and pondering the situation before touching anything.If it 'ain't broken........ Don't try to mend it !
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Originally posted by brianw999 View PostIn just about every takeoff video that I have seen the trigger for raising the gear has been a positive rate of climb being noted.
It's a well-documented, human factors kind of error...not unlike shutting down the wrong engine...there's a really really good double check procedures to prevent that, but really really good is not absolute 100% perfection, either.
AND, there's a very special talent to genuinely sit there for a second and say, "ok what's REALLY going on and what do I REALLY need to do, as opposed to blindly regurgitating the QRH Memory Checklist for go-around with a 777-336A with noooooo consideration to fundamentals.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by 3WE View PostAND, there's a very special talent to genuinely sit there for a second and say, "ok what's REALLY going on and what do I REALLY need to do, as opposed to blindly regurgitating the QRH Memory Checklist for go-around with a 777-336A with noooooo consideration to fundamentals.
The entire purpose of memory procedures is to allow the pilots to stabilize the aircraft without having to "genuinely sit there for a second and say, "ok what's REALLY going on and what do I REALLY need to do".
The initial procedure is very simple: TO/GA, flaps 20, PM verifies pitch and thrust for go-around, PM verifies positive rate, PF calls for gear. Where are we not considering fundamentals there?
If the rate isn't positive for whatever reason, raising the gear early is not going to solve that. The problem is not parasitic drag, it's a lack of thrust, airspeed and lift and as BB pointed out, cycling the gear is going to INCREASE drag anyway.
In that situation, the only thing raising the gear will accomplish is a lot more drag on the ground as you drag along the runway without wheels and then the total drag of explaining yourself to mgmt.
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What's the spool up time for these huge engines?
Could it be that they selected toga and felt that they had enough altitude to retract gear but the high drag config and delay to full thrust just made the m sink in?
I always remember the A320 at the airshow that just ploughed into the trees because the alpha protection wouldn't allow the pilots to get the nose up.
I know Boeing doesn't use that type of alpha protection but slow spool up/sink/tail strike seems possible to me.
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Originally posted by Evan, sort of...Well, The initial procedure is very simple and generally very effective...
The context for my comments goes back to Boeing Bobby asking "Why?"...well, maybe because the pilots promptly ran their checklists without the 'magic pause' to truly double confirm a positive rate of climb...just like you 'always' want to double confirm you are shutting down the correct engine.
Bobby and 5Nav and ATLCrew will probably never pull the wheels up without establishing a climb, nor will they probably ever shut down a good engine...but they're special.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Originally posted by Dispatch Dog View PostWhat's the spool up time for these huge engines?
But the question is: from which idle?
The 777 has two idle settings, determined by FADEC (or EEC).
1) Minimum idle: this is the normal flight idle. It is also the one used in ground mode.
2) Approach Idle: this is an elevated idle setting used in approach (whenever the flaps are set to landing position). Approach idle is elevated to provide a quicker spool-up response during go-around.
AFAIK, the spool-up idle to GA is 6-7 secs. But which idle was that based upon to certify the 8 seconds requirement? Maybe approach idle?
It depends upon the mode. AFAIK the idle mode goes from approach idle to minumum idle a few seconds after gear tilt confirms ground roll.
I'm still wondering if they got into ground mode before initiated the go-around. It would introduce two key problems, reduced idle/longer spool-up times and inoperative (ground-inhibited) TO/GA buttons requiring the crew to advance the levers manually. I can envision enough delay involved in those two things to mess up a go-around attempt. But maybe the programmed delay before switching to ground mode is too long to cause these things to happen in the short time they may have been rolling on the runway. Boeing provides this delay in the event an aircraft might touch down and need to go-around. They did think of that.
So, essentially, what mode were they in when they initiated the go-around? Flight or ground?
Could it be that they selected toga and felt that they had enough altitude to retract gear but the high drag config and delay to full thrust just made the m sink in?
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Originally posted by Evan View PostIn that situation, the only thing raising the gear will accomplish is a lot more drag on the ground as you drag along the runway without wheels and then the total drag of explaining yourself to mgmt.
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Originally posted by BoeingBobby View PostCan you say density altitude?
--- 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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Originally posted by Gabriel View PostDensity altitude. I can say it, but I would not know why I am saying it.First of all, Dubai is basically at sea level, so even with high temperatures the density altitude should not be anything extraordinary.Elev 100ft Temp 105F QNH 29.80 ==> Density altitude = 3500ftSecond, the approach Vref is in IAS/EAS/CAS, not TAS. So a given Vref should provide for the same margin over stall, same lift reserve (how many Gs you can pull), and hence initial ability to arrest the descent. Yes, in a high density altitude situation the engines would provide less thrust and that would reduce the climb rate, but not to the point to make it negative in a 777 at or below MLW.Third, what happened with the "positive climb (both in the ASI and ALT)" that you just mentioned should be checked before the "gear up" part?(as a side note, I was always of the idea that, before setting gear up in a go-around / windshear escape, one should check positive climb but also positive ASI rate before calling for gear up, since a positive climb can be easily obtained trading airspeed, but it will not last)
Even at sea level, at those temps, more like 115 when I was in Bahrain last week, it comes into play. WINDSHEAR, NO configuration changes until you are up, away, and have stable airspeed.
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