Experience
 

As an old timer, It's refreshing to read Bubbers44 essentially practical comments on this topic rather than the airy fairy nonsense we hear so often.The remark that I feel so telling was that 'in the circling, perhaps they forgot.'
Now there speaks the voice of experience!

Experience not on the Airbus I'm afraid, forgetting final flap is possible but not likely due to the display.

Clandestino
 

Agreed !
Of course not, but that is about the minimum weight I could imagine, not willing to go into intricate calculations based on pax weights, estimated cargo or so. I didn't even consider the weight of the deadheading crew.
All the performance derive from that - estimated - baseline value.
The perf margins I took went further as I took the touch-down Vref = Vls and the Vref speed will only vary by 1 kt / ton.
I have to say here that there is absolutely no value judgement on the crew from me. I am just saying that the margins for mishandling were narrow. Very narrow.

As for the -very popular on Prune - theory of a desperate attempt at a late go-around, the maths don't bear it out :
Estimated landing speed : 148 kts
Estimated speed abeam the camera : 100 kt
Estimated speed at the crash site : less than 40 kt
All point to a continuous, albeit insufficient deceleration, and use of brakes (smoking hot as per one of the initial videos, did they start a fire ?).

Now the theory that they had not full flaps. It is very possible, in a HF sense as the procedures on a circling approach call for config 2 / Gear down at the straight-in approach break and final selection of full flaps on base / final turn. Some airlines, though, call for full flaps throughout the circling. Need to knowe TACA's SOPs on this.
Bubbers theory could well be possible here (I don't believe I would ever see the day I'd agree with him ).

[blockquote]Estimated speed abeam the camera : 100 kt[/blockquote]
To those who would suggest that the movement of the camera would exaggerate the speed, or that the perspective of the runway (going from abeam to moving away) would make it appear to be slowing down, here's how that figure is arrived at: in the 4 seconds it's on camera, the aircraft travels 5 plane lengths. Length of an A320 is 37 meters and change, so back-of-the-envelope gives 170 kph, or approximately 100 kt.

We strongly disagree with the assessment by Flight Global, that the airplane was travelling at 100 knots at that point. If that was true, the airplane would definitely have stopped before the runway end, given that the airplane had already slowed down from their touch down speed of around about 150 knots (tailwind 10 knots plus reduced IAS due to density altitude taken into account). If those 100 knots were true, the airplane would have slowed down at a rate of 2.4 meters/second/second at minimum (touch down at the threshold) up to 4.5 meters/second/second in maximum (touch down at the aiming markers, 4.5 m/s/s or 9 knots/s being quite some more than maximum autobrakes) since touch down, suggesting that the airplane would have stopped between 450 to 700 meters before the runway end with that (continued and constant) deceleration.

See the computations and considerations here:

http://avherald.com/h?article=4077cedf/0022

If speed was indeed a factor, the airplane must have been quite a lot faster than 100 knots at that point 650 meters past the threshold and 1000 meters before the runway end.

I would rather wait for the data off the FDR ...

Servus, Simon

Thanks. Can someone help me with this quotation for Eric Parkes' 'A320 Notes'?

http://www.chipsplace.com/helpful/Ai...FlightControls

My main problem is that, as an old-time, strictly amateur aviator, I haven't the faintest idea what an 'SEC' is. :)

But the implication of the passage is that there is some sort of possible systems failure that can result in only Spoiler 5 being extended? As appears to have happened in this case?

Our procedure was to be fully configured on speed downwind for rwy 02. We rarely did the VorDme 02 approach because we arrived from the north. Occasionally we had to do as they did and go around and fly the 02 approach to descend to 5700 ft instead of 6000 to get below the cloud bases. I don't have any B757 charts since retirement but we landed there at max landing weight a lot when runways were dry because of the high fuel charge there. The wet landing weights were the same on 02 with a 5 knot headwind as landing on 20 with a 5 knot tailwind. I always landed on 20 with any tailwind on 02 because the wind changed a lot at TGU. We routinely taxied to 02 for take off with a 15 knot tailwind and waited for it to drop to what we needed that day depending on weight and temperature. It always worked out fine and 5 or 10 minutes was all it took. I appreciate the transcript of ATC communications. It clears up a lot of unknowns.

We used position 4 autobrakes on every landing there. It works the same as Airbus autobrakes and sets a desceleration rate. However that desceleration rate only applies if the runway conditions allow it to without activating the antiskid system. Reports of braking problems there since resurfacing the runway may play a part in the investigation. Thanks Lemurian. I always appreciated your input even when we didn't agree.

It's highly unlikely that only one spoiler was deployed during the landing, unless they were facing a significant defect which should have precluded a landing on such a short runway, particularly when it was wet. It's more likely that the one deployed spoiler as seen in the pictures has just not drifted out of the extended position as hydraulic pressure bled off. It's also possible that the accident caused damage which blocked the hydraulic lines to that spoiler, thus negating the possibility for the fluid pressure to bleed off.

As for the speculation that they did not have full flaps for landing, as was mentioned above, "Flap 3" and "Flap Full" are the normal landing configurations for the A320. Prior to doing a Flap 3 landing, we are required to select LDG FLAP 3 on the EGPWS panel. If one doesn't make that selection, the EGPWS will be screaming "TOO LOW FLAPS" rather loudly on final approach. The crew would have to be in a coma to miss this call.

Again I must say, that the exact translation of the word that the controler used to alert of runway condition is Damp, he said "pista humeda."
He didnt said wet. "Mojada." o "Contaminada."
I think that this is important because makes the diference between Required Landing Distance in Dry and Wet coditions, and it makes the diference between normal operation and pilot error in calculations of Required Landing Distance.

I dont know if he landed long or short, but the fact is that he pased the camera with three landing gears on the ground, and the reverses didnt were deployed. I´m anoyed about that.

I suppose that everybody affected by TGU closure and Airbus are going to blame the pilot for the accident based in his evaluation of landing runway conditions. Always is easier to blame the usual suspect to calm down the economical repercussions of an airplane crash.
Firsts declarations of the honduran Civil Aviation Authoroties said that the problable cause was a failure of the plane, when the notice about Toncontín closure was know they started to blame the pilot for landing in a wet runway with a lot of tail wind.

In this airport pilots usually prefer to land on the runway 02. For the runway 20 you need a very high rate of descent, and with a MDA of 2700 feet above the runway you dont have a good chance to go in if the day is cloudy. In Circling things are not much better, the turn is to the captains bad side, and you fly closer to the mountains. Another fact is that recomended rate of descents are not published in the VOR/DME App chart for runway 20. The exceed the margin for a stabilished approach.
Runway 02 is safer always, instead of tail wind.

RWA
 

Since no-one replied to your question, here goes:

SEC is the Spoiler Elevator Computer. Since these moving surfaces are not connected physically to the sidestick, it's the SEC which controls which surfaces will deflect, and by how much, depending on the conditions. So it's best to have lots of active SECs!

You probably worked out that yellow, green and blue are the three hydraulic sytems.

Thanks, I have put your remark in a comments in the translation. Was this already your second remark - didn't see your first!

That approach is seriously, seriously flawed!

Let's make this clear in an assumed picture: the camera looks in a right angle to the runway, is fixed and the lens system makes sure, that all angles in the pictures are depicted correct from corner to corner. The camera looks from 30 degrees right to 30 degrees left, the camera is say 150 meters off the runway.

As the airplane comes into the view at the right hand corner of the picture, it is therefore at a distance to the camera of 150/cos(30 degrees)=173 meters, and it has to travel a distance of 150*sin(30 degrees)=75 meters to reach the center of the picture. Because of the larger distance the airplane appears smaller than it would be in the center due to the perspective, and because of the angle the distance of 37 meters in reality appears on the picture as 37*sin(30 degrees)=18.5 meters. The same applies for the left hand corner of the picture. The total distance on the runway centerline from right to left corner would be 150 meters or 8.1 times the airplane length measured at the corner or roughly 4 times the airplane length measured in the center of the picture.

Now, let's put the camera at an angle to the runway, say 30 degrees to the left. The center line of the runway at the middle of the picture would now be 173 meters away (the camera still 150 meters off the runway in the same position, just rotated). The airplane appears in the picture at its closest position to the camera, 150 meters distance and departs the picture at an angle of 60 degrees (as we have another right angle in the triangle, this time not in the center but at the right hand corner of the picture, we can use Pythagoras without any doubt), the airplane travels therefore 86.5 (173*sin(30)) meters until it hits the center of the picture. The distance of the runway center line at the left hand corner of the picture would appear at 300 meters (150/cos(60)), the total distance travelled from right to left hand corner of the picture would therefore be 260 meters (compare 86.5 meters from right corner to center point!). You can not apply any linear measurement in this view at all.

One can not simply say therefore, the airplane could be put 5 times into the picture from appearance to disappearance, 4 seconds, the airplane is 37 meters long and thus we see at a speed of 5*37/4 meters/second or 166 kph. The perspective of the picture and the angles of even a still camera (not to mention a panning one!) introduce gross errors to that approach.

Now, we aren't even able to determine the angles between the camera and the runway centerline with any degree of certainty in this scenario, but we would need to do so for every single frame of the video to be able to use those frames for the measurements. So the panning introduces a lot of additional difficulty into that determination.

All of this with an optimal camera, which a surveillance camera usually isn't (that aims to view a broader angle than would appear on the pic). You'll note, that the exact distance to the airplane is needed and the exact angles to be able to compute the actual distances covered. And we need to know the exact time stamps of the pictures to be able to really compute the time - that video doesn't provide times at all. We don't know, whether frames have been inserted or removed for a "smooth video", what time intervals were between the various pictures of the camera (maybe it was indeed 1 picture per second as it may look like).

There is a reason, why photogrammetry is a science!

Servus, Simon

To land straight in on 20 it was necessary to descend as soon and as rapidly as conditions allowed. At 15 DME descend to 7,000 ft and call the airport in sight or before 15 DME if able to get visual contact. Then get established so at 3miles, about 8 DME you are at 4300 ft. Sometimes S turning to a right base entry helped if you were a bit high. Otherwise you had to overfly the airport and make right traffic to 20 which was difficult from the left seat if you weren't familiar with the valley. 20 is an upslope runway so it is easy to get low if you just judge your descent by runway appearance alone. On really hot days you were weight restricted landing on 20 because of go around climb gradient restrictions because of terrain. Landing on 20 is like landing at any other airport if you start your visual approach early. Check airmen didn't count landing on 20 as meeting the requirements of a TGU check out so either they had to land on 02 with a legal tailwind or do another qualification flight.

Post #144, Tree, Bubbers 44;
It is a nice safety feature but there are also accidents which have resulted from manual selections of both systems on the 732 (reverse) and the DC8, (spoilers - more than one accident). It can be assumed that Airbus' intentions were to deal with the possibility of inadvertent deployment while ensuring their availability once the a/c was solidly on the ground and they used the technology around which the design concept was created to do so rather than defaulting to cable & pulley systems with associated mechanical interlocks.

I'm not trying to compare the two as such a discussion is profoundly pointless and a waste of time given the success of both models/types but merely trying to clarify why the design might be as it is on the Airbus.

I discussed the work-around here during the TAM accident discussion last year. The technique was discussed in terms of bringing the flap lever up one step after touchdown, (ie, Conf Full to Conf 3) to enable spoilers/brakes then reverse. Those that disagreed I don't think were aware or had not flown the 727 in which a one-step-up flap re-configuration was done routinely after touchdown. I agree it ought not to be a work-around but a manufacturer-sanctioned and available technique for crews faced with short, contaminated runways. I agree that there may be more politics and operational or technical risk involved and that the design was a point raised in the Lufthansa Warsaw overrun accident, (Conf 3 vs Conf Full on contaminated runways). I believe that Lufthansa (and others) went to Conf 3 as a standard flap configuration for landing shortly after. Config 3 is the "recommended" flap setting but we rarely see it in the data.

Many thanks, Dysag.

No chance, mate. :) Thanks to getting married early in life, I could only afford gliding for most of my flying 'career.'

So most often I didn't even have a bloody ENGINE to work with, leave alone hydraulics! Spoilers, yes - vital, landing a glider..........

Dear Simon,

I was merely giving the methodology for "how" those numbers were arrived at, not making any statement about their veracity; indeed I did note the problems with moving cameras and angular speed.
For the record, the "plane-lenth" measurement involved counting those lengths traveled with reference to the ground, in each frame, not taking a general measurement.
I also agree that as the aircraft moves away from the camera, it will look slower than what it suggests.
I do not find your initial arguments conclusive, namely that if it were going at 100 kts at that point, it would not have overrun. That's putting the horse in front of the carriage, or using analysis to drive the facts.
You did, however, inspire me to go back and take a close look at the data.

First, you are factually wrong. The tape is time-stamped to the thousandth of a second. Second, the camera's perspective is good enough that, even with the panning, you can overlay two images without noticeable problems from distortion, which I've done. Third, you are intuitively correct: at the point it comes on the screen, it is going notably faster than 100 kts.

I took the first and third frames where the aircraft appears. The time-stamp of the first frame ends with 18.928; the third frame is stamped 20.421, so the interval is .593 seconds. Matching the vertical section of the first image that contains the aircraft with the scene in the second image, it is clear that the aircraft has traveled on the runway over a plane-length.
Assuming conservatively that's forty meters, that would come out 243 kph or 131 kts. I'm sure greater precision (and perhaps an even higher ground speed) can be had.
If you'd like to play with the image, and make the necessary angular motion calculations, or just see for yourself or post for others, drop me a line and I'll mail it to you.

So: 1) camera motion can be compensated for, 2) The image gives us precise time measurements, and 3) you'd still need to calculate angular effects, but back-of-the-envelope shows it's at least 130 kts.

As for the -very popular on Prune - theory of a desperate attempt at a late go-around, the maths don't bear it out :
Estimated landing speed : 148 kts
Estimated speed abeam the camera : 100 kt
Estimated speed at the crash site : less than 40 kt
All point to a continuous, albeit insufficient deceleration, and use of brakes (smoking hot as per one of the initial videos, did they start a fire ?).

Only one board deployed and engine 1 nowhere near full reverse.

Alright, taken note of, and we are in agreement here.

Not quite ;-)

If the airplane had slowed down to 100 knots already, from an approximate 148 knots or so, it would have exercised quite some braking already. If that braking action continued for some time, it would not have overrun. In fact, even on an ungrooved wet runway a deceleration of 1.5 meters/second/second (3 knots/s) is well normal, and I used that deceleration rate.

Yep, absolutely - we are in agreement of the speed being higher than 100 knots.

And you are right, that there are timestamps overlaid by the copyright notice of the TV station that obviously broadcast it. I hadn't seen those until your remarks.

Can you recheck your time stamps, especially as you write 18.928 and then compute 0.593 seconds to 20.421, please?

The timestamps are hard to decipher, but the airplane is not visible at ...19.421, is fully visible at ...20.028, is last visible at ...22.031 and is entirely out of the picture at ... 22.431, so that makes it maximum 3 seconds visible.

Now add the angle between runway and camera to that scenario ...

If I however use 130 knots as a speed at that point 650 meters past the runway threshold with 1000 meters to go, a deceleration rate of 1.5 m/s/s would be insufficient to stop, stopping distance would be 1500 meters (departing the runway end at a speed of 38 meters/second=74 knots). A deceleration rate of 2.2 meters/second/second (~4.4 knots/s) would be necessary to stop at the runway end (which may not be available on a wet runway).

Photogrammetry can certainly clear that up. That was my main point.

No doubt about that.

Agreed.

Servus, Simon

What deceleration rates do Autobrake "low" and "medium" give on an A320 just out of interest (assuming dry runway; typical landing weight) and what sort of ground run distances do these translate to?

In calculating the speed, I initially read the stamp as 19.928. In working it up, I looked at it closer, and I saw 19.828. Sorry, that's the source of the problem. I think we can put it at "at least" 130 kts.

Thanks for pointing that out, I'll need to check with the Spanish source, as it is clear from the later discussion, that they were going for "dos cero", e.g.

15:26:02Z......
[TA390] TONCONTIN TORRE. TACA TRES NUEVE CERO. SOBREVOLANDO EL CAMPO.
PARA CINCO MIL QUINIENTOS.
[TGU TOWER] TACA TRES NUEVE CERO. CONTINUE APROXIMACION PISTA DOS CERO.
VIENTO DOS CERO CERO GRADOS. SEIS NUDOS. NOTIFIQUE EN FINAL.
[TA390] NOTIFICAREMOS EN FINAL PARA LA DOS CERO. TACA TRES NUEVE CERO.
GRACIAS.

and only switched to "cero dos" for their second approach after the missed approach procedure.

Servus, Simon

Particularly unpleasant to see U Tube plummeting to the lowest depths.....

I confirm that, I have listened to the tape myself, with the transcript before me I was able to follow the words and understand them. They are talking about zero two indeed at 23:50 and two zero later at 26:02.

I am just about to correct the translation accordingly.

Servus, Simon

Mea culpa Simon: the Flight Global article was written to reflect the emergence of the security video rather than to analyse the accident. The low-end 100kt figure, derived in a few minutes, was based on very basic assumptions, and only intended to give a sense of proportion. Having since had the time for a more thorough assessment - from which we've also come up with a speed of 120-130kt - I'll be updating the figure in the story.

Ultimately the question isn't whether the A320 was travelling too fast - the overrun itself settles that - but rather why. Either it was decelerating normally but late, or it couldn't decelerate, or it was deliberately not decelerating.

David,

I think, that question is best answered by the facts derived from flight data recorders and other evidence available, correctly interpreted by the accident investigation team.

Right now we are making an assumption again, namely that the video is not manipulated and the timestamps are correct. I'd certainly concede, that this may be a reasonable assumption, but it remains an assumption nonetheless and is not established fact.

Thanks for jumping in - my respect for your statement!

Servus, Simon

Video Speed
 

The speed of the A/C can easily be computed once the frame count per second of the camera is known. The fact that the camera is panning right while the 320 is speeding left in the frames is irrelevant.

If one wanted to give the illusion of increased speed, the frames would have to be free of any stationary objects. Find a stationary object and use it as a reference.

Normal NTSC video runs at 30 frames or 60 fields per second. Surveillance video can run at any frame rate set by the operator.

So, talk to the guy who set the system up first. Then do the math.

The first approach was to 20, the second to 02. They decided it was easier to land on 02 with cloud conditions. Either way it is a visual approach over the runway if you go to MAP. You can then land either way if you can stay VMC. Clouds were marginal around 2,000 feet that day so they probably were trying to make it work and found 02 easier to land on. Unfortunately that put them landing downhill on a wet 5400 ft runway with a 10 knot tailwind with a 70 ft cliff at the end. We had strict rules on landing weights and tailwinds so would not have landed. Over 5 knots on a dry runway of tailwind prohibited us from landing.

Bubbers,
 

Sounds fair and safe to me.
A few questions, though :

1/- Were your minima 2700 ft / 3 sm (= 4800 m) ?
If yes, would you have attempted a circling approach on RWY 02 with this METAR :MHTG 301500Z 19004KT 2000S -DZ FEW008 BKN020 OCV080 21/19 Q1016 2KM S SW WSW D/C 8KM PCPN CL HZ ? ( reading it, I have the feeling that all quadrants leading to the final 02 (w, SW, S ) were below vis min and the broken ceiling 700 ft below minimum.

2/- On RWY 02, there is a 5.3° PAPI restricted to A and B cat aircraft. Is that descent path angle a reflection of the actual trajectory you'd find yourself at on short final ?
3/-Corollary : How were speed control and respect of a landing trajectory ?

5 km was controlling for initiating the approach. We never could get an answer from FAA or anybody how they report multiple visibilities in different directions and what was controlling. In the US it is prevailing visibility controlling approach legality which means over half of the directions visibility is 5 km. We would have and have in the past initiated the approach with 2,000 broken conditions as long as we had 5 km reported in at least one direction. TGU had certain landmarks they used to determine visibility but they did not have anything to do with prevailing visibility. The cloud bases were not controlling. You just couldn't continue to a landing unless you had the airport visually in sight reaching MDA.

The only time I couldn't land there and ended up at San Pedro Sula the ceiling was 2300 overcast and never saw the ground. Noone landed that day because of the weather. That day they would not allow any 02 approaches to get below 2700 ft AGL. I complained so the next day they notamed all 02 approaches OTS. My complaint was if they publish an approach they should let you perform it.

The reason visibility to the s sw was 2 km was that was about as far as you could see with the hills there on a clear day with any clouds hanging around the distant hills. We had no glide angle info for landing. We had reference altitudes crossing some tanks then just maintained about a 1200 fpm descent to flair turning final below 100 ft. Yes we got yelled at sink rate, sink rate a lot from the gpws. Unless you had about a 15 knot headwind to reduce below 1200 fpm descent it usually was going off below 100 ft. We would get fired for doing an approach like that anywhere else but to land in that 700 ft touchdown zone that was required.

Bubbers44,
 

Thanks for all these informations.
I had a feeling that those visibility and ceilings values would somehow have been based on aspect of the local terrain.
Thanks for clearing that out.
The part that is still bothering me is : I presume that all operators there would have the same criteria.
Do they ?

The 5 knot tailwind was our ops. I don't think Taca had that restriction. We also had a 10 knot max tailwind for all airports we landed at except San Jose, Costa Rica, which was in the valley at 3,000 feet so one day I landed with a 15 knot tailwind there because the clouds were too low to circle but when I got back to Miami with weather coming in with a 13,000 foot runway at sea level the 15 knot tailwind exceeded our ops. We were the only operation limited so sometimes to try to make things safer it just gets more complicated. Of course the reason they changed to 15 knots at Costa Rica was too many flights couldn't circle because of those typical low clouds so flight were diverting.

What deceleration rates do Autobrake "low" and "medium" give on an A320 just out of interest (assuming dry runway; typical landing weight) and what sort of ground run distances do these translate to?
You select Max at take-off (if rejected) and it becomes active when ground spoilers are deployed. You use low and medium for landing:
LO waits 4 seconds (!!!) after ground spoilers are deployed and gives 1,7 m/s/s deceleration (5,6 feet/s/s)
MED waits 2 seconds only and gives 3 m/s/s (or 9,8 feet/s/s)
If the antiskid is active (slippery surface) you will not get those deceleration rates.
From experience and without saying it is what should be done, if I felt that even although the computed landing distance for very wet runway was available, the braking might be a serious concern, I would not use the autobrake, but slam both brake pedals "to the floor" as soon as on the ground and let the antiskid do its best with that.You can even brake as hard as you can before touching the ground.You will not block the wheels.

Photogrammetry is quite limited with only a single camera, so I attempted to analyze the Security Camera images frame by frame, measuring the distance the fuselage (and only the fuselage) traveled from frame to frame. Since the aircraft is basically traversing a straight line (down the runway), I used fixed points in both the foreground and background as references. My technique was to draw 2 straight lines (through foreground and background reference points) on the images, one marking the position of the nose of the aircraft on each image, and one marking the position of the nose from the previous image. I could then determine how far the fuselage had moved forward from the previous image.

This technique seemed to work for the first few frames, but then seemed to fail in the later frames as the aircraft's speed begin to skew towards 160 knots in the later frames (161 being the highest I measured). I assumed this might be due to greater pixilation, greater view angles or some other artifacting in the images, as the aircraft got further away from the camera. I also assume there's no way this aircraft could have been accelerating towards 160 knots after touchdown.

The results also seem to indicate that the time stamps on the images are quite accurate.

Some portion of the aircraft is recorded in 9 images. I'm only posting the results for the first 3 measured frames because they are consistent and the following frames start the skewing towards 160 knots.

I used the following formula in Excel to calculate speed. I'm an American so I like to measure in feet :)

ESN = 1/TD*DTF*3600/FNM

Where:

Assumed Aircraft Length = 123ft 3in
ESN = Estimated speed in knots/hour
TD = Time Difference from previous frame to current frame
DTF = Distance Traveled in Feet
FNM = Feet per Nautical Mile = 6076.1155

Frame 19.828 - First reference frame, marked nose position only
Frame 20.031 - TD = .203 sec, DTF=53.4ft, ESN = 155.9 knots
Frame 20.421 - TD = .390 sec, DTF=102.7ft, ESN = 156.0 knots
Frame 20.828 - TD = .407 sec, DTF = 106.8ft, ESN = 155.5 knots

Again the speeds begin to skew towards 160 knots after this, which can't possibly be right.

Now if someone else knows where the camera is, has access to an accurate scale drawing of the airport (and immediate surroundings), and can reference structures in the background, they should be able to determine where the aircraft was located on the runway in each frame. But I leave this task to someone else. :O

Hello, Flight Safety,

thanks a lot for your effort indeed! Great post!

Servus, Simon

I calculated a B757 at mglw landing under those conditions and came up with a 155 knot ground speed at touchdown. The camera view is about 2500 ft down the runway so your calculations would show no desceleration.

Caulfield

Try LPHR :)

frightening!

For planning purpose, I could imagine TACA dispatch had also computed the figures for RWY02 DRY 5kt TAILWIND 62 tonnes giving a Required Landing Distance of 1600 meters (factored distance)
The same figures but for a WET surface would have limited the weight at 58 tonnes.

Crew and ATC look both aware of that 5kt ''limitation'' (?)
Once airborne, the crew can eventually discard the factored distance.
RWY02 WET 10kt TAILWIND 62 tonnes giving an Actual Landing Distance of 1400 meters (unfactored distance)
To obey this figure, the crew knows he has, in this especially challenging environment, to proceed to a text book landing and deceleration. It provides only 250 "extra" meters …

But thanks to Simon Dinger and FS effort, I would say that the text book was a lot to put in practice. I could not have used their scientific methods but kept it simple and fully agree with that estimated 130 knots and something. It’s an average speed which means the 320 would probably still be around 140 kt or more when it appears on tape, which could mean a VERY late touchdown … (?)

If it is confirmed that the flaps on the crash site were at a different setting than FULL, I would also opt for PJ2 explanation, even if it’s not an Airbus procedure.
I just hope the guy, in the rush, does not mix the handles … and retract the speed brakes in the same time !?

A final word for Dream Land, I won’t bother you any longer with this stuff in this specific thread after that. There is a multitude of incident reports available dealing directly or not so directly to the Airbus sidestick philosophy, maybe I pay too much attention to them, but maybe you ignore them too much (?)
My personal message and do whatever you like with it: Don’t be surprised one day … to be surprised
Have a safe flight !

Of course the reason they changed to 15 knots at Costa Rica was too many flights couldn't circle because of those typical low clouds so flight were diverting.

The maximum tailwind acceptable for the A320 is, to my knowledge, 10 knots. That comes from the Airbus FCOM, and it has been demonstrated and approved. One must remember that it can be with normal flight controls or with the so-called "direct law". The flare on this type of aircraft is a very computed matter with electric flight controls, aside from the increased landing distance due to tailwinds. If a company choses to exceed those limitations with that type of aircraft I do not think Airbus would approve, if asked...After that of course, the captain may decide to do what he thinks best in a difficult situation, but it crtainly should not be allowed on a day to day basis. The A320 is not a 737...

Narval,
 

You don't know what you're talking about, either about the 'Bus flight controls or on the wind limitations.
15 kt is indeed an Airbus-com-DGAC approved tailwind limit used by Air France for airplanes serving the Corsican airports. Enough said on that.
As you wrote, the 737 is no A320.

CONF iture Re “To obey this figure, the crew knows he has, in this especially challenging environment, to proceed to a text book landing and deceleration. It provides only 250 "extra" meters …”
If you mean that there is some other approved landing technique which can improve the landing performance then you are mistaken.
A ‘text book’ landing is what should always be aimed for on every landing and it would not require any special tricks; it provides an average ‘performance’ landing. Attempting to land from a low threshold crossing height, landing ‘short’ or at low speed will inevitable break the rules and increase risk.

Re “Once airborne, the crew can eventually discard the factored distance.”
No, why should they. Factored distances are a requirement for good purpose – to maintain the required level of safety – the additions are safety factors not multiples of distance to be traded or ignored.
A wet landing distance (factored or unfactored) is based on ‘standard’ data. There are assumptions about runway friction, which in this instance appear to be much less due to recent heavy rain and/or a ‘slippery’ surface from newly laid asphalt. In addition, landing data takes account of the wind; in a tailwind this is factored by 150%. If wind measurement or assessment is incorrect, or there are sudden wind changes then the data is in error – 150% error; thus tailwind operations have greater risk.

Don’t forget that the speed estimates from the video relate to ground speed; so far there is no public information on either airspeed or wind speed, thus an apparent ‘fast’ landing could be due to either aircraft handling or wind speed.