Air India Express 737 skids off runway and breaks in two after landing at CCJ

[flashcrash]

The aircraft, en route from Dubai, skidded off the runway and broke in two at Calicut airport upon landing, India's aviation authority said.

Rescue operations are under way, with emergency services at the scene.

At least two people, including the pilot, have died, the BBC has been told.

[Evan]

This was reportedly an attempt to RWY 10 after an initial go-around from RWY 28. METAR says winds 260 at 12kts.

First million-dollar question is: Why the tailwind approach to 10? Both ends have ILS and avherald reports that there were no NOTAM's regarding 28 being unserviceable.

Also wondering if the ground-spoilers were somehow disarmed between landing attempts. But so far it appears to be simply a late touchdown on a fast tailwind landing with a plane that likes to float flown by a crew that wants to get there.

[FL400]

https://www.indiatoday.in/india/stor...996-2020-08-07
"An Air India Express flight with over 190 passengers and crew members onboard skidded off the runway at the Kozhikode International airport in Kerala on Friday evening. DGCA officials told news agency ANI that the Dubai-Kozhikode aircraft was at "full speed" while landing at the Karipur Airport and overshot the runway."
I wondering how they got the 'full speed info" so early, doubt that if its from the FDR.

[flashcrash]

The phrase "full speed while landing" seems rather meaningless. If it means they landed at the recommended landing speed for the conditions, weight and aircraft configuration, then good. I would hope the majority of aircraft do that. It's possible the reporter may be trying to tell us that max auto braking didn't kick in after landing, although I doubt that could be known with any certainty at this stage. The runway is 9400 feet. Minimum landing distance for a B738 at MLW is 5800 feet (sea level, zero gradient). Add a factor of 1.4 for a wet runway (more if there's standing water) and you have a minimum landing distance of at least 8100 feet. Then add in the factors Evan mentioned, the 12 kts tailwind and a late touchdown, and it starts to get pretty dicey.

[FL400]

I watched a video on Youtube by a pilot couple, here they were doing playback of fligtradar 24, the first approach was supposedly on RWY28, west to east direction (against the wind), it was stable approached but performed a go around probably due to weather and did like an eight pattern and then made the second approach from the other end of the RWY (10) along the wind direction/tailwind, this time the approach speed was above the norms and did the landing not sure of touch down point and skidded off the runway. https://www.flightradar24.com/data/f...x1344#2525ad3d

[Gabriel]

The phrase "full speed while landing" seems rather meaningless. If it means they landed at the recommended landing speed for the conditions, weight and aircraft configuration, then good. I would hope the majority of aircraft do that. It's possible the reporter may be trying to tell us that max auto braking didn't kick in after landing, although I doubt that could be known with any certainty at this stage. The runway is 9400 feet. Minimum landing distance for a B738 at MLW is 5800 feet (sea level, zero gradient). Add a factor of 1.4 for a wet runway (more if there's standing water) and you have a minimum landing distance of at least 8100 feet. Then add in the factors Evan mentioned, the 12 kts tailwind and a late touchdown, and it starts to get pretty dicey.

Not really. The landing distance required (that you say is 5800ft) already includes provision for crossing the threshold at 50ft in a 3-degrees slope and at not less than Vref, flare, touchdown (without any tendency to a hard landing, porpoising or bounce), and stop without causing excessive wear and tear to brakes and tires... PLUS a margin of 67% of that distance. That means that the actual distance necessary to stop the plane, counting from a point 50ft over the runway, would be 3500 ft (2300 ft of margin vs the 5800), approx 1500 of which is the distance necessary to descend from 50ft and flare, so the actual rolling/stopping distance is some 2000 ft. When you add the +40% factor for wet runway, you are not only adding it to the actual landing run (2000ft of stopping distance) which is what gets actually affected by the wet runway, but also to the 1500 ft of distance to descend from 50 ft and flare and to the original 66% (2300 ft) margin. That adds another 0.4*(1500+2300)=1520 ft that theoretically are not needed even with a wet runway.

In other words, if the required landing distance for wet conditions is 8100 ft and the available landing distance is 8100 ft, you are tight from the legal point of view but the runway is not tight at all, those 8100 ft include A LOT of margin. That margin is precisely for things like floating a bit (like extra 500ft) approaching at slightly more than Vref, braking not as strongly as demonstrated by Boeing, etc.

On top of that, they had not 8100 ft but 9400 plus some 500ft of stopway + overrun safety zone, so a total of 1800 ft of additional margin.

On top of that, I bet my sandwich that they were at less than MLW so the actual required landing distance would have been less than 8100 ft. Say 200 ft less? You clearly would easily have 2000 ft of margin ON TOP of the original 2300 ft of original margin and ON TOP of the 1520 ft of additional (inflated) flare and margin-over-margin distance. That's a total of 5800 ft more than absolutely needed to descend from 50 ft, flare, touchdown and stop on a wet runway. If the plane used 5800 ft more than absolutely needed, it would have still overshot the runway threshold but it would have stopped in the overrun safety area just short of falling into the valley.

Now, that is with no tailwind. Tailwind is a big detractor. If you land with 12 extra knots of groundspeed you will spend a couple of extra seconds to slow down to what would have been the "no wind" ground speed, but those 2 seconds are going to be the "fastest speed and longer run" 2 seconds in this landing (and on a wet runway it could be more than 2 seconds). But even that is not so much compared with the margin available. As an example, touching down at 152 knots instead of 140 kts would easily consume extra 500 ft of dry runway or 700 ft of wet runway. You still have ~5000 ft of margin over the absolute minimum. Flare another 1000 ft longer than the test flight, still have 4000 ft of margin. Come with 10 knots more airspeed than Vref, that's another 1000 ft of wet runway, still have 3000 ft of margin.

When you have these kind of landing overruns, you typically have one of the following (ordered as what it looks to me to be from most frequent to less frequent, but I don;t have statistical data to back it up):
1- A waaaaaay too high/fast approach, touching down when still waaaaay too fast and waaaay too long down the runway (a case where the pilots should have clearly gone around).
2- Runway condition much worse than expected (like iced or standing water + aquaplaning).
3- Problems with the stopping means (be it technical problems or human problems like forgetting them, using them too late, or using them too mildly).
4- Significant forward thrust left on one or more engines.

Now let's wait (for the official report) and see.
My bet is on 1.

[Evan]

Looking at the wreckage today, it's a miracle that the wings and fuel tanks seem to have remained intact. This could have been a much greater loss of life. Cabin crew all survived.

[flashcrash]

I don;t have statistical data to back it up.

Boeing has some statistical data on the relative frequency of the causes of landing overruns which may be helpful. Data covers the period 2003-2010.



Source: https://www.boeing.com/commercial/ae...les/2012_q3/3/

[Evan]

Oh, hallelujah!! About effing time... Ban all airplanes without this new technology!

https://www.boeing.com/commercial/ae...les/2012_q3/3/

[Schwartz]

AVHerald posted an update. The plane touched down abeam of taxiway C (3300 feet past the threshold) and the controller knew it was trouble right away and ordered emergency vehicles to follow the aircraft down the runway. He activated the crash button immediately when he saw no plane at the end of the runway. Fast response. Now the question is whether they tried a go-around or not.

[Gabriel]

The plane touched down abeam of taxiway C (3300 feet past the threshold)

And there you have the first piece of the puzzle.
I would not be surprised that the next pieces (when the FDR is analyzed) will be that they touched down too fast too, and that there was a delay to use the stopping means to their full capabilities.

[Evan]

And there you have the first piece of the puzzle.
I would not be surprised that the next pieces (when the FDR is analyzed) will be that they touched down too fast too, and that there was a delay to use the stopping means to their full capabilities.

Yes, but why RWY 10 instead of RWY 28? I think that is the place to start.

[Gabriel]

Yes, but why RWY 10 instead of RWY 28? I think that is the place to start.

It looks like the weather was too bad on the approach area for RWY 28. They did approach RWY 28 first and went around and came back for RWY 10. There is nothing intrinsically wrong with that, even if there is a tailwind, if the tailwind is within the airplane's and company's limitations, and if the landing performance calculations yield that LADA (Landing Distance Available) > LAD (Landing Distance), considering not only the wind but also the runway conditions.

Now, there IS a lot wrong with being 3000+ ft past the threshold and still in the air and not go around. (Or with having excessive airspeed in final approach (i.e. unstable approach) and not going around. Or in being too high on final and not going around, if those happened too).

[Gabriel]

http://avherald.com/h?article=4daf960f&opt=0

Utterly confused by this:

a passenger seated in the aft cabin reported that following the go around the aircraft positioned for another approach and touched down, however, did not appear to slow down but to accelerate again.

And this (note: the bottom of the picture is forward, the top is back):

[Gabriel]

Based on the testimony from the controller, I checked in Google Maps the distance from the approach threshold to the touchdown point and fro the touchdown point to the edge of the cliff.

The touchdown point is clearly way too long down the runway (the thicker white rectangles are the touchdown aim point) and clearly, seeing that they were so much down the runway before touching down, the pilots should have gone around.

That said, from the touchdown point to the edge of the cliff they still had 6400 ft. That is a very respectable distance to stop a 737 (after it already touched down) even in a quite contaminated runway. Adding the typical 1500 ft to descend from 50 ft and flare, that would be equivalent to a 7900 ft runway.

As a reference, Aeroparque Jorge Newbery (Buenos Aires City downtown airport) is 6890 ft long, and Chicago Midway's longest runway is 6500 ft, and dozens of 737 flights operate there every day in a variety of weather conditions including of course wet runways but also snowed or iced runways in the case of Midway.

Something very wrong must have gone there, in addition to touching down 3400 ft past the threshold and with a 12kts tailwind.