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TAM A320 crash at Congonhas, Brazil

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TAM A320 crash at Congonhas, Brazil

Old 3rd Aug 2007, 16:40
  #1041 (permalink)  
 
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Does that make the B777 the best Airbus made by Boeing?

*cough* Anyway, back on topic.
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Old 3rd Aug 2007, 16:42
  #1042 (permalink)  
 
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threemiles - there is no point if it is done early since as Tyro has said you merely flatten the approach angle making an accurate touchdown more difficult. If you look back, however, you will see that the same a/c the previous day had been landed 500' short of the normal touchdown zone (and only just stopped). This can only be done safely and accurately by a LATE adjustment to steepen the approach, ideally in the last 200' or so, which would then of course generate a 'low on glideslope' indication although probably not a warning (737). This was a standard technique in my day when I flew highly-swept fighters to put the beast 'on the numbers' from an instrument approach.
BOAC;
I disagree. If it is done early and continuously throughout the approach the approach angle does not change. You are merely paralleling the "on glideslope" angle. Fly the last 1000ft. exactly one dot low or one dot high and the approach angle is the same as "on" the glideslope. The only parameter that changes is the trajectory point of intersection with the runway (APPROXIMATELY the 500ft mark one dot low and 1500ft one dot high). A LATE adjustment is dangerous. It was called a "duck under" and was forbidden at my previous employers (we did short and slippery operations many times daily for decades). Fortunately most of those runways have now been extended.

Last edited by Tree; 7th Aug 2007 at 23:59.
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Old 3rd Aug 2007, 17:01
  #1043 (permalink)  
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I do not agree, Tree, and the ones I have seen always finish up with a flatter landing path. I am referring to Cat I approaches here, and I was under the impression that 'ducking under' was related to diving below GP early to try and get visual which is 'verboten' as you say, but is it not effectively what flying '1 dot' low' does? What I am describing is adjusting the visual aiming point once visual, if that is the intent. Flying below GS in IMC is fraught with more danger.

Edit following a moments thought and ChristiaanJ's post
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Old 3rd Aug 2007, 17:09
  #1044 (permalink)  
 
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Re Christiaan

não da is an idiomatic expression in PT, but you certainly can't translate it as 'ça ne donne rien' in F, which would be a litteral translation. 'ça ne va pas' would come closer to it. (as a reply to the demand to decelerate)
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Old 3rd Aug 2007, 17:10
  #1045 (permalink)  
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A-320 Accident in Taipei

www.asc.gov.tw/acd_files/164-c1contupload.pdf
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Old 3rd Aug 2007, 17:13
  #1046 (permalink)  
 
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Originally Posted by Tree
I disagree. If it is done early and continuously throughout the approach the approach angle does not change. You are merely paralleling the "on glideslope" angle. Fly the last 1000ft. exactly one dot low or one dot high and the approach angle is the same as "on" the glideslope. The only parameter that changes is the trajectory point of intersection with the runway (aproximately the 500ft mark one dot low and 1500ft one dot high).
So glad I'm not flying with you.
The G/S info is pure angle, not vertical distance from the glide path, which is what you imply.
Your ignorance of the system and belief in urban legends stupefies me.
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Old 3rd Aug 2007, 17:18
  #1047 (permalink)  
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speedbrake is inhibited in config FULL by Mad (Flt) Scientist
Mad, speedbrake in Airbus speak is a deceleration tool while in flight (spoilers 2,3 and 4), A320 gives you 50% of speed brakes while on autopilot, full speed brakes with A/P disconnected, when config full is selected, speed brakes are inhibited, slightly different system on A321.
.
Ground Spoilers:
(spoilers 1 through 5) ARMED - With both thrust levers at idle, and two main gears compressed.
.
(1 through 5) NOT ARMED - 1 REV, 1 idle or two REV (any flaps, 2 main gears compressed).
.
Manually Extended- CONFIG FULL: spoilers 1, CONFIG 0-3: spoilers 1-4
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Old 3rd Aug 2007, 17:28
  #1048 (permalink)  
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Originally Posted by ChristiaanJ
The G/S info is pure angle,
- glad you said that. I realise I got suckered in there. I have edited my earlier reply.
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Old 3rd Aug 2007, 17:57
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whether going one dot low or not should not be the question...it is not what caused the crash...and unless someone posts an exact touchdown point, not in the touchdown zone, I think we can dismiss this line of thought.

by the way, what was the exact point of touchdown in terms of feet from threshold?
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Old 3rd Aug 2007, 18:00
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BOAC,
I said: The G/S info is pure angle,
You said: Glad you said that. I realise I got suckered in there. I have edited my earlier reply.
Your earlier reply still says: You are mathematically correct, Tree ....
Sorry for the "I said, you said" bit, but it was the easiest way to copy it....

I agree this is almost a TechLog subject, but...

Tree is mathematically wrong.
If he flies systematically one dot low:
1) He will systematically be following a shallower flight path.
2) His glide slope aerial will still hit exactly the same point of the runway if he doesn't flare.

Since he's not landing on his glide slope aerial, but on his landing gear, which is a bit lower, basic geometric maths dictate his wheels will touch a bit earlier if he's below the glide slope.

Whether "greasing it on" with a shallower approach and touching down a bit earlier is a good idea is another matter.
The 3° glideslope was not invented for nothing.
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Old 3rd Aug 2007, 18:02
  #1051 (permalink)  
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Bomarc - I'm not sure anyone will ever know. I'm not aware of any data on the FDR that will tell.

CJ - post was corrected, I think your server has cached. Thanks anyway
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Old 3rd Aug 2007, 18:02
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by the way, what was the exact point of touchdown in terms of feet from threshold?
Not been released but the information I have is that touchdown was within the TZ.
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Old 3rd Aug 2007, 18:11
  #1053 (permalink)  
 
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so much talking about the glideslope.

let us go back to flying 101 (basic flying) spot landings...you pick a spot on the runway ( or abeam a light) and go to it and plant your mains on it. the pilots were visual and that is what I would have done on a short runway...I would also have advised the non flying pilot that I was departing the ILS glide slope for a visual aim point...this is allowed from the middle marker on in 121 ops here as long as you are visual.

I really doubt if the pilot in question was actually watching the glideslope so much as watching his spot/target...perhaps he was just using the expression one dot low to explain the GS inhibit request.

The 3 degree glide slope is a wonderful thing, it truly is a miracle of aviation. the ILS is a wonderful thing. Jimmy Doolittle made the first blind landing almost 80 years ago using vibrating reeds instead of our needles or CRT equivilent.

But a good pilot, looking at a spot on the runway, in decent wx will be able to get a more precise landing than an ils will give you...provided that you are clear of obstacles, and stable.
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Old 3rd Aug 2007, 18:16
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@Dream Land
So how does one manually extend the GS on an A320? The same lever as used to arm them?
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Old 3rd Aug 2007, 18:22
  #1055 (permalink)  
 
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all please remember that inhibiting the glide slope is different than manually extending a glide slope.
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Old 3rd Aug 2007, 18:26
  #1056 (permalink)  

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Glide Slope

ChristiaanJ.....a little strong verbiage on the comeback, but you are absolutely correct about the angular and not lateral displacement.
The actual..precise...displacement (vertical)value of "one dot" depends on several factors relating to the specific implementation of each ILS. Suffice it to say that a one dot deviation at Threshold Crossing is typically equal to approximately 3 feet off the GS axis. This leads to the old saw that if the GS deviation indicator ("needle") is "on scale" at TC( within the max dots and not pegged) you will land in the paint. I doubt very much that a TCH error of 3 feet (one dot) will translate into a +/-500ft variation in TD point but there are several variables involved here.

Last edited by A310driver; 3rd Aug 2007 at 19:08. Reason: correct poster's name
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Old 3rd Aug 2007, 18:42
  #1057 (permalink)  
 
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@Max Tow

Absolutely right and post now edited.

Regarding the MEL amendment, I did not realise that this came from a TAM operator I recall somewhere on this thread a 'possible' question mark.

In any case an amendment of this importance should at least require a notice to aircrew and a reason for its implementation. IMHO of course.
Jim
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Old 3rd Aug 2007, 19:02
  #1058 (permalink)  
 
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Concerning the crew words, when trying to descelerate.

From someone who had access to the recorded dialog: the original phrase is "não dá!", which can be translated into English as "it is not possible!".

AJ
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Old 3rd Aug 2007, 19:16
  #1059 (permalink)  
 
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A310driver,
I think we're already on the same wavelength... or frequency if you like.
Since several posts already seem to say the landing was in the touchdown zone at a "normal" speed, G/S does not seem to be an issue here. Might be worth discussing elsewhere, but here it would just "pollute" the real discussion.
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Old 3rd Aug 2007, 19:33
  #1060 (permalink)  

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ChristiaanJ

Agreed....
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