Viscount724
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UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 5:27 pm

Noted following from December 23 in Transport Canada daily occurrence reports, re a UA (ex-CO) flight IAH-YYC that made 3 missed approaches at YYC before landing successfully on the 4th attempt. The passengers must have been getting nervous by that point. Wonder what the problem was?

UAL 1288, a United Airlines B737-800, was on approach to Runway 28 at Calgary when the crew overshot at 1935z due to an unspecified flight control problem. They then declared an emergency when 15 miles southeast of the airport. They went missed approach on the 2nd attempt from 4 miles final at 1955z due to instability. At 2009z, they overshot a 3rd time from 3 miles final to Runway 28. The aircraft landed safely on Runway 28 at 2026z and taxied to the gate. Several aircraft were delayed on departure as well as on arrival. TSB report to follow.
 
tdscanuck
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 6:17 pm

Quoting Viscount724 (Thread starter):
Wonder what the problem was?

The combination of repeat overshoots with a declared flight controls emergency makes me think failure of the flap/slat drive systems (or a skew or jam)...that will send approach speed way up. Since most crews don't get to practice that maneuver much, and probably never in the actual aircraft, the sight picture looks all wrong (the pitch attitude on a approach is different) and the flare handling is all messed up due to the changed attitude and higher speed. I can easily see several overshoots followed by go-around until the crew got the hang of how the plane was handling and what they ought to be seeing out the window.

Autoland wouldn't be an option in that configuration, I think, so they wouldn't have gotten any help there.

Tom.
 
YYZatcboy
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 7:48 pm

If that was true though why would they keep trying for 28? Wouldn't trying for 16/34 be a better option, unless the cross wind was above limits...
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tdscanuck
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 8:37 pm

Quoting YYZatcboy (Reply 2):
If that was true though why would they keep trying for 28? Wouldn't trying for 16/34 be a better option, unless the cross wind was above limits...

From noon until after 6pm on Dec 23rd, the wind at YYC was over 20 mph sustained, gusting over 45 mph and it held a steady heading of 270...in other words, they had a screaming gusty headwind on runway 28. The crosswind component on 16/34 was going over 37 knots at times.

http://www.wunderground.com/history/...req_state=AB&req_statename=Alberta

Tom.
 
YYZatcboy
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 10:17 pm

That answers that then. Thanks Tom.
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wn700driver
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 10:29 pm

Quoting tdscanuck (Reply 1):

Autoland wouldn't be an option in that configuration, I think, so they wouldn't have gotten any help there.

Hmmm... Meaning the autoland simply isn't available out of configuration, or that it somehow has the authority to activate/manipulate secondary &/or auxiliary control surfaces?
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CODCAIAH
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 11:06 pm

Could one of you explain: What is autoland? How does it work?
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tdscanuck
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sat Dec 31, 2011 11:07 pm

Quoting wn700driver (Reply 5):
Meaning the autoland simply isn't available out of configuration, or that it somehow has the authority to activate/manipulate secondary &/or auxiliary control surfaces?

The former, I think. The autoflight system has no control of slats/flaps in a 737NG (autoslats exist but that's not an autoflight function). I looked at the QRH and didn't find anything that would explicitly prohibit an autoland with a flap/slat failure but you are limited to bank angles no more than 15 degrees for a flaps up landing...I have my doubts about the ability of the autopilot to stick a landing in those wind conditions at those approach speeds without exceeding the bank angles.

This is all supposition on what the flight controls problem actually was, of course...I had no idea what was actually wrong with the plane. It also would depend on what United's Ops Spec says about use of autoland in these wind conditions and configuration.

Tom.
 
Braniff747SP
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 1:50 am

Quoting CODCAIAH (Reply 6):
What is autoland? How does it work?

Autopilot for landing, basically. Plane will land itself; one of the more experianced members can give a more thorugh answer.
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zalemam
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 3:57 am

Quoting CODCAIAH (Reply 6):
Could one of you explain: What is autoland? How does it work?

The airplane lands itself, not like a coupled ILS approach where the airplane descends on its own and then the pilots do the flair maneuver and reduce throttle to idle, autoland is the airplane doing everything by itself. Pilots do not look out of the windows, they focus on instruments. Usually auto lands are done in very low visibility landings like this one.

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tdscanuck
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 4:34 am

Quoting zalemam (Reply 9):
The airplane lands itself, not like a coupled ILS approach where the airplane descends on its own and then the pilots do the flair maneuver and reduce throttle to idle, autoland is the airplane doing everything by itself.

An autoland is still usually a coupled ILS approach, you just don't disconnect the autopilot before touchdown. You can also do it with GLS (from a technical standpoint...most airports and airlines aren't equipped for it). One something like a 737NG the autoflight system will go through system checks and self-diagnostics at 1500' radio altitude and confirm to the crew that everything is ready to go, adequate redundancy is in place, etc.

The pilots still have to set flaps, gear, idle the throttles at touchdown, and deploy reversers. Autobrake may or may not be used (if not, the crew must do the braking). The autopilot will follow the ILS beam down, flare, touchdown, set the nose down, and track runway centerline until disconnected or the aircraft comes to a full stop.

Quoting zalemam (Reply 9):
Pilots do not look out of the windows, they focus on instruments.

At least one of them still needs to look out the windows; you still have to respect the relevant autoland minimums and somebody needs to be looking out the window to confirm that you can actually see the runway (and that the autoland is actually tracking) when you reach the minimums. Nobody is currently doing Cat IIIC 0/0 autolands in revenue service that I know of, so someone needs to be watching.

Tom.
 
IAHFLYR
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 7:11 am

Quoting tdscanuck (Reply 10):
You can also do it with GLS (from a technical standpoint...most airports and airlines aren't equipped for it).



PMCO has a few aircraft which are GLS equipped (recently delivered B738/B739 and soon B788) and EWR has some GLS procedures in place. IAH will be coming online soon with a few GLS procedures as well.
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Thenoflyzone
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 8:05 am

Quick sidebar, since we are talking about YYC and GLS approaches.

Westjet has some RNP approaches (with curved segments as well ) at YYC, which enables them, at least in a continuous descent environment, to fly at idle thrust most of the way down, thus saving fuel.

Thenoflyzone
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tcasalert
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 9:28 am

Interesting that they chose to press on with repeated missed approaches. I know many airlines have SOPs restricting the number of missed approaches before diverting to the alternate.

Continuing with 4 approaches could be very dangerous, the wind was clearly too high and not improving, the crew would be getting more and more fatigued with each approach.

Sounds like this was a case of "Get there-itis", fortunately it ended well but we only need to look back to the ORK disaster last year for a reminder of what could have been 
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zanl188
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 1:58 pm

Quoting TCASAlert (Reply 13):
Interesting that they chose to press on with repeated missed approaches. I know many airlines have SOPs restricting the number of missed approaches before diverting to the alternate.

That's assuming that the reason for the missed approach is weather and that weather will be better at the alternate.

In this case it appears that an aircraft fault is the reason for the missed approaches and the fault would go with the aircraft to the alternate. Thus no cause to divert.

We need more info to be sure.
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larshjort
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 2:37 pm

Quoting TCASAlert (Reply 13):
Interesting that they chose to press on with repeated missed approaches. I know many airlines have SOPs restricting the number of missed approaches before diverting to the alternate.

Continuing with 4 approaches could be very dangerous, the wind was clearly too high and not improving, the crew would be getting more and more fatigued with each approach.

Sounds like this was a case of "Get there-itis", fortunately it ended well but we only need to look back to the ORK disaster last year for a reminder of what could have been

On the other hand it could be because they couldn't configure the plane for landing andwanted to know how it responded.

The wind was well within limits coming almost strait on.

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FlyHossD
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 5:48 pm

Quoting TCASAlert (Reply 13):
Interesting that they chose to press on with repeated missed approaches. I know many airlines have SOPs restricting the number of missed approaches before diverting to the alternate.

Continuing with 4 approaches could be very dangerous, the wind was clearly too high and not improving, the crew would be getting more and more fatigued with each approach.

Sounds like this was a case of "Get there-itis", fortunately it ended well but we only need to look back to the ORK disaster last year for a reminder of what could have been 

Do we know that the conditions for landing were any better at the alternate?

It's quite common on this forum to second guess the actions of a flight crew, but what should be focused on here is that the crew did the right thing - they landed safely and didn't accept or continue approaches that may have placed the outcome in doubt.

Flying the line, there are days where you're flat out underpaid, I bet this crew felt that way after landing.

Frankly, I find your comments to be out of line and sensationalist.
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DualQual
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 5:52 pm

Quoting tdscanuck (Reply 10):
idle the throttles at touchdown

The autothrottles will idle at touchdown. However, they need to be disconnected, along with the autopilot, at touchdown and the rollout is performed manually.
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tdscanuck
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Sun Jan 01, 2012 6:06 pm

Quoting DualQual (Reply 17):
Quoting tdscanuck (Reply 10):
idle the throttles at touchdown

The autothrottles will idle at touchdown. However, they need to be disconnected, along with the autopilot, at touchdown and the rollout is performed manually.

You're absolutely right the autothrottles will idle on their own. Depending on the model, you do not necessarily need to disconnect the autothrottles or autopilot during rollout.

Tom.
 
oneworld77
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Mon Jan 02, 2012 11:39 am

Quoting TCASAlert (Reply 13):

Interesting that they chose to press on with repeated missed approaches. I know many airlines have SOPs restricting the number of missed approaches before diverting to the alternate.

Continuing with 4 approaches could be very dangerous, the wind was clearly too high and not improving, the crew would be getting more and more fatigued with each approach.

Sounds like this was a case of "Get there-itis", fortunately it ended well but we only need to look back to the ORK disaster last year for a reminder of what could have been 

Interesting point this, are there rules (CAA?) governing the amount of approaches that can be made? I had a case where we landed on the 3rd attempt in 2009 and last Wednesday the same situation. (same route, same aircraft, same airline etc). In 2009 we were told that the chaps up front were giving it another and final go and if not successful we would return to point of departure or divert. Last Wednesday we were told the same thing as we successfully attempted our second approach. What would dictate the differences?

Weather was the same in both cases (gusts of 100km+) although I don't know what the precise gusts were at each attempt.

Does the airline stipulate the amount of approaches? P.I.C? CAA?
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tcasalert
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Mon Jan 02, 2012 1:47 pm

Quoting Reply 19):
Interesting point this, are there rules (CAA?) governing the amount of approaches that can be made? I had a case where we landed on the 3rd attempt in 2009 and last Wednesday the same situation. (same route, same aircraft, same airline etc). In 2009 we were told that the chaps up front were giving it another and final go and if not successful we would return to point of departure or divert. Last Wednesday we were told the same thing as we successfully attempted our second approach. What would dictate the differences?

Weather was the same in both cases (gusts of 100km+) although I don't know what the precise gusts were at each attempt.

Does the airline stipulate the amount of approaches? P.I.C? CAA?

The restriction is usually down to the carrier's procedure. They generally limit it at 2 before diverting as far as I can work out (airline crew may be able to confirm),

Although I believe the authorities require an aircraft to only commence an approach if the weather is above minima and they are likely to be able to complete it. If its not they have to divert.

Someone may be able to confirm this though.
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IAHERJ
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RE: UA IAH-YYC - 3 Missed Approaches Before Landing

Mon Jan 02, 2012 7:07 pm

Quoting tdscanuck (Reply 18):

You're absolutely right the autothrottles will idle on their own. Depending on the model, you do not necessarily need to disconnect the autothrottles or autopilot during rollout.



Not on the 757/767/777 but indeed, on the 737 you do have to disconnect the autothrottles and autopilot during the rollout as it that aircraft does not track the centerline on the runway. That is why the 737 is only certified to cat III/a and still requires some sort of visual by the pilot flying to continue the approach to touchdown.
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