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cumulushumilis
Posts: 232
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Re: Westjet Near Water Impact in Sint Maarten

Fri Mar 17, 2017 4:43 pm

sixtyseven wrote:
Not sure of that aircraft, but would guess there WOULD still be vertical guidance past the MAP. The approach would need to be coded in such a way to create that constant descent. A runway threshold fix +50 feet, to the MAP to the FAF is what I would expect. What there company policy demands with auto flight past the MAP with a runway visual I don't pretend to know but if they left it all hooked up it would arrive at the threshold at 50 feet (not taking any adverse weather into it).


The Boeing FCTM states that their are two scenarios where the MAP can be located at threshold crossing height or located back from the runway like in SXM. If VNAV is not disconnected prior to the MAP, VNAV guidance is level flight. If they followed the same stabilized decent profile from the FAF to the MAP (I think the published is 3 degrees) that would place them at a runway threshold crossing height of approximately 50 feet ( not sure where that point is in SXM-could be somewhere on the beach).

From a crew management perspective that is one of the reasons that it can be a challenging approach even on clear weather days.
 
sixtyseven
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Re: Westjet Near Water Impact in Sint Maarten

Fri Mar 17, 2017 5:31 pm

Ok thanks for that. I guess the question here is how they got so low after the MAP. The MDA is 700 feet at lowest if they were flying the RNAV. They obviously saw the runway to continue but got themselves way too low visually. There was gusty winds but it wasn't anything severe so I think they just lost SA and got way out of position vertically. Like I said though they overshot which was what was called for but it probably could have come a bit earlier. Hey would have been looking at a sea of red on the PAPI.

A Mismanaged break out followed by the smart decision.
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JoeCanuck
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Re: Westjet Near Water Impact in Sint Maarten

Fri Mar 17, 2017 6:34 pm

sixtyseven wrote:

A Mismanaged break out followed by the smart decision.


I think that's an excellent summary.

When they did find themselves in a bind, they didn't try to fart around fixing it and attempt to save the landing. They overshot, got their poop in a pile and greased it, on their second try.
What the...?
 
airnorth
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Re: Westjet Near Water Impact in Sint Maarten

Sat Mar 18, 2017 11:39 pm

I see that Simon now has a report on his website.
http://avherald.com/h?article=4a65586e&opt=6144
 
1900Driver
Posts: 137
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Re: Westjet Near Water Impact in Sint Maarten

Sun Mar 19, 2017 6:19 am

jimbo737 wrote:
Here's what happened at CYHZ when Air Canada, the 4th safest airline in the world, came in a little low in March 2015.

http://cnews.canoe.com/CNEWS/Canada/201 ... 55916.html


What kind of nonsense is that! You don't have to get so defensive. You may be high off the teal cool aid, but don't degrade the discussion to those levels. The conditions & scenarios were completely different (624 perhaps being worse).

I'm sure their will be an internal investigation & the company will make procedural changes as necessary if needed. I personally think the crew did a job by electing to do a go around given the situation they were in.
 
76er
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Re: Westjet Near Water Impact in Sint Maarten

Tue Mar 28, 2017 6:16 pm

Another video popped up:

https://m.youtube.com/watch?v=uN3Fd0x0FoQ


Incredible to see how much time it took before the go around was initiated
 
Passedv1
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Re: Westjet Near Water Impact in Sint Maarten

Tue Mar 28, 2017 6:26 pm

76er wrote:
Another video popped up:

https://m.youtube.com/watch?v=uN3Fd0x0FoQ


Incredible to see how much time it took before the go around was initiated



...before you can see/hear the results of the go-around being initiated.
 
KLDC10
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Re: Westjet Near Water Impact in Sint Maarten

Tue Mar 28, 2017 7:02 pm

airnorth wrote:
I see that Simon now has a report on his website.
http://avherald.com/h?article=4a65586e&opt=6144


That states that the Canadian TSB classed this as a "non-reportable incident", but nevertheless opened an investigation because of "public expectation". I'm a little concerned that a safety body should open an investigation because of the misinformed opinions of the general public.
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trnswrld
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Re: Westjet Near Water Impact in Sint Maarten

Tue Mar 28, 2017 7:13 pm

76er wrote:
Another video popped up:

https://m.youtube.com/watch?v=uN3Fd0x0FoQ


Incredible to see how much time it took before the go around was initiated


Wow, they were skimming that water for a little bit there. Good thing there were no swells lol.
 
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blackbox67
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Re: Westjet Near Water Impact in Sint Maarten

Tue Mar 28, 2017 7:38 pm

trnswrld wrote:
76er wrote:
Another video popped up:

https://m.youtube.com/watch?v=uN3Fd0x0FoQ

Incredible to see how much time it took before the go around was initiated


Wow, they were skimming that water for a little bit there. Good thing there were no swells lol.


Let alone what a yacht or the regular ferryboat would have done.
 
LightningZ71
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 4:35 am

Passedv1 wrote:
76er wrote:
Another video popped up:

https://m.youtube.com/watch?v=uN3Fd0x0FoQ


Incredible to see how much time it took before the go around was initiated



...before you can see/hear the results of the go-around being initiated.


Even on this board, there are still a lot of people that don't realize that you can't just press a button and shove the throttle controls all the way forward and get instant power. It takes time to get a turbofan from near idle to full power.
 
76er
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 3:27 pm

I know that (15.000 hrs heavy jet), but for jet engines to spool up from idle to go-around thrust takes max 5 seconds. These guys spent close to 20 seconds at an extremely low altitude relative to their distance from the runway. To me that suggests they could both be heads down trying to figure out what the heck their LNAV-VNAV was doing. "What's it doing now?!?" is still heared quite often on the modern day flight deck. Not saying this is what happened, just one of the possible scenarios.
 
rbaadsvik
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 4:10 pm

T
 
Yakflyer
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 4:29 pm


Even on this board, there are still a lot of people that don't realize that you can't just press a button and shove the throttle controls all the way forward and get instant power. It takes time to get a turbofan from near idle to full power.


Actually the 737 configured for landing and descending at a rate that would not trigger the GPS, will have the engines spooled up and making enough power that when the TOGA button is pushed or the thrust levers are manually pushed forward the engines will respond essentially immediately.
 
sixtyseven
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 6:34 pm

76er wrote:
I know that (15.000 hrs heavy jet), but for jet engines to spool up from idle to go-around thrust takes max 5 seconds. These guys spent close to 20 seconds at an extremely low altitude relative to their distance from the runway. To me that suggests they could both be heads down trying to figure out what the heck their LNAV-VNAV was doing. "What's it doing now?!?" is still heared quite often on the modern day flight deck. Not saying this is what happened, just one of the possible scenarios.



Couple of things.

You are incorrect in saying it's max five seconds to go from idle to g/a thrust. Way off.

The time a high by pass jet engine takes to reach full commanded TOGA thrust from established idle is much, much longer. I won't bother you with the minutiae but it begs the question as to why you would even bring it up.

In your 15,000 hours of heavy jet time, when were you pulling the power off? I would imagine since you are still alive it was somewhat closer to the runway. Like over it, when the landing was assured. Not a quarter mile back like these guys were at their lowest. Had these guys had the power at idle we would be reading about a crash.

Boeing has stated anytime the thrust is at idle, in landing configuration, decelerating, in descent, if a go around is commanded ground contact can not be assured, thus our training in Low Energy Go-Arounds. These guys never entered the low energy state.

There was an accident in Canada some time ago involving a CRJ. Sure not a heavy jet but a high by pass engine to be sure. The aircraft was in the low energy state and from the time the thrust levers were FIREWALLED to the time the engine was producing commanded thrust was something in the area of 11-13 seconds. It was between 7-8 seconds before the engines were producing any sort of thrust that could be described as "helpful". A long time when you're out of altitude, and speed.

I would say the 5 seconds you're talking about would be accurate if the engines were on spool. But not from idle.
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76er
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Re: Westjet Near Water Impact in Sint Maarten

Wed Mar 29, 2017 9:04 pm

Allright, I should have been more clear, my apologies. Typing replies on an ipad does not really invite to writing elaborate stories.

Of course the engines on this 737 were not at idle while skimming the water, considering they appeared to be more or less in level flight with the gear down and flaps extended. Unless they were still bleeding off lots of excess speed, which is rather unlikely here. So spool up time to go around thrust will indeed be shorter. How short I don't know, I'm not familiar with the CFM engine, just the PW4000 and CF6. Pretty sure those two power up in less than 5 seconds. Tell you what, I'll time it on my next trip and wil eat some humble pie if proven wrong.

Sorry for the topic drift.
 
sixtyseven
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Re: Westjet Near Water Impact in Sint Maarten

Thu Mar 30, 2017 12:45 am

Haha no sweat. Do it on takeoff. Ram em up right from idle..... and hope they come up together lol or you might wind up in the tulips.
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glen
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Re: Westjet Near Water Impact in Sint Maarten

Thu Mar 30, 2017 9:32 am

76er wrote:
but for jet engines to spool up from idle to go-around thrust takes max 5 seconds.

5 seconds is quite close. If I remember correct it is a 6 seconds certification limit.

sixtyseven wrote:
You are incorrect in saying it's max five seconds to go from idle to g/a thrust. Way off.

The time a high by pass jet engine takes to reach full commanded TOGA thrust from established idle is much, much longer.

sixtyseven wrote:
Haha no sweat. Do it on takeoff. Ram em up right from idle..... and hope they come up together lol or you might wind up in the tulips.

The 6 seconds limit is why there is a difference between ground idle and flight idle/approach idle. So taking the time on take-off gives you a wrong figure anyway.
"The horizon of many people is a circle with zero radius which they call their point of view." - Albert Einstein
 
sixtyseven
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Re: Westjet Near Water Impact in Sint Maarten

Thu Mar 30, 2017 3:22 pm

True. I will concede that and apologize to 76er, he's obviously a fine man based on his handle.

That said what my point is is the time requirement from IDLE to Full Thrust. The five second spool up time in a go around is from an approach thrust setting to full G/A thrust. Not from idle. I harp on this because after ACA 646 great changes were made in low energy go around training. There were no certification requirements to manufacturers or airlines in the US or Canada to prove aircraft performance in the low energy regime. Rejected Landing with power at Idle Became the new buzz word.

It took five seconds for the engines to spool up from flight idle before they reached a nominal approach thrust setting. The report is below. A lot of things changed in the ways airlines train pilots after that accident. It opened a lot of eyes as to what to expect from your airplane once you close those throttles. plus the myriad of other things it was quite a case study.

http://www.bst-tsb.gc.ca/eng/rapports-r ... 7h0011.asp
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longhauler
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Re: Westjet Near Water Impact in Sint Maarten

Thu Mar 30, 2017 4:22 pm

I remember being very aware of how long it takes high bypass ratio engines to spool up after reading the report of the Air France A320 crash at Habsheim in 1988. (If you recall, engine performance was one of the areas of interest).

http://reports.aviation-safety.net/1988 ... F-GFKC.pdf

It states that certification requirements dictate that go-around thrust be within 3% of commanded thrust no longer than 8 seconds after selecting TOGA thrust from flight idle. In this crash, thrust was at ~84% 5.5 seconds (the point of first impact) after commanding TOGA thrust. In this case, TOGA was estimated to be around 91%, so it appears that the engines were operating within standard.

As noted above, low energy go-arounds are a common simulator exercise. But in all honesty, I'd rather see it above a runway at 50' and not water. And remember, one of the parameters of "low energy" is that the thrust has been brought below flight idle, and thus TOGA would be achieved longer than 8 seconds.
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
sixtyseven
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Re: Westjet Near Water Impact in Sint Maarten

Thu Mar 30, 2017 5:11 pm

Below flight idle? How does one do that in flight?

A/c in landing config (gear and flaps), in descent, thrust stable in idle range, airspeed decreasing, below 50 feet is my understanding of the regime.
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airnorth
Posts: 467
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Re: Westjet Near Water Impact in Sint Maarten

Fri Oct 06, 2017 5:33 am

A slight change in the type of incident as reported by Simon at The Aviation Herald
http://avherald.com/h?article=4a65586e&opt=0
 
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AirlineCritic
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Re: Westjet Near Water Impact in Sint Maarten

Fri Oct 06, 2017 10:21 am

Interesting. What do we think has caused them to change the classification to "incident reportable"?

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