TAM A320 crash at Congonhas, Brazil

[theamrad]

JohnBr -
Well I think we can agree about the 1 reverser inop point – it can’t account for the high speed in the later half of roll, even with ‘wishful thinking’. As for mech failure, I’ve heard of a total brake failure on AB – but is going to be a real rarity for a TOTAL failure – coupled with (by implication) happening after touchdown with no prior warning (hydraulic/anti skid warning messages or the like) to the crew, etc. Seems (to me) that’s a non-starter at this point in time (pending FDR). So then it’s down to the difference between this and preceding aircraft landing?

Raggyman -

Or do aircraft tyres pretty much aquaplane anyhow no matter how fast you are going?

no they don't – but the main factors affecting whether it happens or not in a given situation are runway macrotexture, speed and depth of water. By most accounts, the macrotexture in this case was poor . Good macrotexture allows frictional contact between the tyre and runway surface by virtue of the ‘roughness’ being able to penetrate the liquid layer. With poor macrotexture – the liquid film can form a hydraulic wedge between the surface of runway and tyre – when the tyre is moving above a certain speed. As far as threads are concerned – it’s not possible to make a reasonable comparison between what’s needed for an aircraft or average road vehicle. They’re in totally different regimes of speed and load. For aircraft, braking efficiency on slippery surfaces at low speed can be quite effective relative to a road vehicle – there’s a much higher load to increase friction than on a car.

[Johnbr]

BOAC...
I did say "almost" no effect....The landing distance calculation table for the A330 states a correction of only -4% for a wet runway and of -7% on the required landing distance at conf full for a 1/2 inch of standing water...and that´s for both reversers operative....

[broadreach]

The flash at the end of the video

The Google Earth image below shows the APPROXIMATE positions of the airfield cameras and of the point at which the aircraft left the paved surface of the airport. Surrounding that part of the taxiway is a wall about 15” high which the aircraft (according to news reports) struck before hitting the TAM cargo depot, about 100m across the road. The camera’s field of vision is just a shade wider to the left of the yellow line; the white line indicates a trajectory consistent with the end result. Please note, entirely conjectural on my part, to possibly explain the “flash”. Others have pointed out that it might have been a tyre burst or a compressor stall.

I don’t think it’s been mentioned here yet that part of the aircraft did graze a car on the road below.

[Rainboe]

People who are not reading the full thread are introducing dead ends. The speculation about the little flash before the big one is counterproductive- a proper read will bring up the fact the undercarriage appears to have gone through a low wall on the boundary of the airfield. This will have had a serious affect on the structure and would produce some sort of small explosion at that speed. It is fits with the timescale before the big flash. I do not believe there is likely to be any connection with surges- this is a very stable engine. It is obvious the cause of the accident occurred long before the aircraft even entered the video coverage. The tyre tread question is also irrelevant. Airliner tyres do not have any form of 'tread' to assist with braking. Apart from longitudinal channels, there is no cross tread.

[lomapaseo]

Quote:
Quote:
Flash on the Video
--------------------------------------------------------------------------------
Has anyone commented on the flash visible from the left side of the aircraft on the video just before it disappears from view?

One hypothesis: Reverse thrust was selected on Eng 1 (eng 2 rev thrust was deactivated). Pilots realize they will not be able to stop the aircraft and, contrary to the recommendations of the FCOM (Flight Crew Operating Manual) to execute a full stop after reverse thrust is selected, initiate a go-around by pushing the trust levers to TOGA. An engine going from full rev to full forward thrust could possibly suffer a compressor stall while the reverser doors are closing, causing the flash we see in the video.

A much more likely cause is the engine ingesting fence material etc. on its way out of the airport perimeter.

[TopBunk]

theamrad

On the A320, is there not still a recall drill (not on ECAM) for 'Loss of Braking'?

There was in my day. It required switching the A/Skid & N/W Strg switch off and then manually braking with max 1000psi pressure.

If that was unsuccessful then you were to use short and successive applications of the park brake.

It was a published procedure, so I presume that it has happened to the extent that Airbus had to devise a procedure [I don't recall it on any Boeing I have flown], although I, fortunately, never suffered myself.

In the event of a slippery runway, determining the cause for the lack of braking may well be very difficult in the heat of the moment, no?

All of this is just speculation, but with basis in fact on the A320 family

[TwoOneFour]

Just a thought but this was an interesting read:

http://www.ntsb.gov/ntsb/brief.asp?e...13X01603&key=1

[broadreach]

Just to remind people that there is no perimeter fence, these pics show the BRA 734 that nearly met a similar fate last year. Note that cars only appear on the upper road, immediately adjacent to the airport; the traffic on the main road is below the frame. That pic, looking up at the BRA aircraft, was taken from a point around 150m up the road toward the main terminal where the cameras are.

[NigelOnDraft]

TB That drill is still there. On a limiting, wet / slippery runway, if you had to carry out that drill I really reckon you'd be off the end i.e. it might help stop the aircraft, but you'll be way over any Ldg Dist calcs...

NoD

[320capt.]

-Yes, That is still one of the memory items on the 320.
-If i am not wrong switching off the Anti Skid /Nose Wheel steering procedure was introduced after the Overrun ai Ibiza in the late 90's
-If autobrakes are selected it may take a little longer in establishing a complete braking failure, particularly since the warning is inhibited in the LDG,T/O phase.

[theamrad]

The thrust asymmetry created by the left engine at TOGA power with the right engine in full reverse greatly increased the right yaw forces, and they were not adequately compensated for by the crew's application of rudder and brake inputs.

VMCG???? Maintaining control with one engine out by use of rudder and/or brake is one thing - but full thrust in the opposite direction?

[dss3000]

Hydroplanning

Hi Hetfield

Its been awhile since flying school! but here is the physics on hydroplanning, Its is mainly a factor of tire pressure. I dont fly Airbus products but I would imagine the Main wheel pressure would be around 130-150 psi, follwing this formula we could expect the hydroplanning speed to begin around 95 kts, that is wheel speed. Its very plausible that this AC never had any effective braking on the landing roll and that the crew was faced with no other option to try and execute a GA. With all the other factors involved ie TR locked out, newly paved ungrooved runway, the top coat still slippery, perhaps higher touch down speed ect... they may have been doomed from the beginning!! again this is all speculation at this point, but a realistic possibility which I am sure will be investigated by the authorities.

Quote from the FAA Flight Safety team
"When the runway is wet, you may be confronted with dynamic hydroplaning. Dynamic hydroplaning is a condition in which the airplane rides on a sheet of water rather than on the runway's surface. Because hydroplaning wheels are not touching the runway, braking and directional control are almost nil.

Three Types of Hydroplaning

There are actually three types of hydroplaning:

Dynamic - where the airplane rides on standing water;
Viscous - where a film of moisture covers the painted or rubber-coated portion of the runway; and,
Reverted, or melted rubber - where locked tires on a wet runway can cause heat so intense that the aircraft is actually riding on a mixture of steam and melted rubber.

For now, we'll concentrate only on dynamic hydroplaning.
To help minimize dynamic hydoplaning, some runways are grooved to help drain off water. However, most runways are not.
Tire pressure is a factor in dynamic hydroplaning. By this simple formula you can calculate the minimum speed, in knots, at which hydroplaning will begin. In plain language, the minimum hydroplaning speed is determined by multiplying the square root of the main gear tire pressure, in PSI, by nine.

For example, if your main gear tire pressure is at 36 pounds per square inch, you would begin hydroplaning at 54 knots.

Landing at higher than recommended touchdown speeds will expose you to a greater potential for hydroplaning. And once hydroplaning starts, it can continue well below the minimum, initial hydroplaning speed. "

[TwoOneFour]

Interesting that the BRA 737 also opted to veer left at the end of the runway - is that an attempt to reach the taxiway, or to avoid the ILS gantry off the end of the deck?

Since the next stop is the main road and the buildings opposite, wouldn't a turn to the right - where there's far fewer obstructions - be a better idea?

[theamrad]

In the event of a slippery runway, determining the cause for the lack of braking may well be very difficult in the heat of the moment, no?

ABSOLUTELY! And if we imagine that coupled with hydroplaning!!!!

If autobrakes are selected it may take a little longer in establishing a complete braking failure, particularly since the warning is inhibited in the LDG,T/O phase.

Ok – so the logic of inhibited warnings for landing and T/O is pretty well thought out – but could this particular case be deserving of reconsideration – esp for approach to a short field? – Any warning relating to impaired braking performance kind of ceases to be an unwanted distraction when landing with premium brake performance being an absolute requirement?

Raggyman - someone-else asked about tyres a while back - bit more info/links if you want - http://www.pprune.org/forums/showthread.php?t=283517

broadreach - just my 2 cents on the flash thing - given where we think it was, and to me the flash appears to be above the wing and to the height of the fuselage - i can only explain it with gear or other structure damage from hitting the wall, puncturing the wing and ignition of some fuel spray.

[broadreach]

TwoOneFour
The option may not have been available to the TAM crew. And if the BRA crew had in fact been able to choose and gone right they would have toppled over another embankment at the threshold of 17L.

Theamrad
Yes, plausible. Not certain but I believe all the undercarriage assemblies were found at the crash site, i.e. not torn off at the wall.

[PK-KAR]

TwoOneFour,
The LLZ gantry is mounted on a pylon 80-90m or so from the end of the runway... if you go off the end of the runway, you might still be airborne before you hit those pylons...

PK-KAR

[The_Baron]

Gentlemen - a question. When do you feel that you are committed to the landing? When PNF calls 'decide' (at least one aircraft has been landed at the wrong airfield because the crew felt they were committed to land, even though they realised their error before touchdown), nosewheel on ground, spoilers out, reversers selected, turning off the runway, or what? This critical decision cannot be made 'on the hoof', and I believe that the criteria ought to be discussed and thought out during initial and refresher training and briefed prior to the approach. Each landing will need a different answer depending on conditions and runway length. In general if your RLW tables say you will stop on the runway you will so long as you land at the correct position at the right speed, and have used the appropriate table for the actual runway conditions. Max braking may be required as soon as the wheels are down - remember: brake for effect not for comfort. In most instances a single failure should be contained within the 1.67 safety factor. What do you all think? Four overruns in such a short space of time is too many.

[TopBunk]

When do you feel that you are committed to the landing?

Only when the reverser's are selected in my company. Think about it .... you touch down at what 125-150kts .... you would normally be at about 80 kts at that point on the runway if taking off; so no problem going around from a speed/runway remaining POV. Deploying reverse thrust is a different kettle of fish however, in that re-establishing forward thrust is a variable and undefined feast.

That does lead however, to a grey area / captain's authority to override SOP's which may have featured here. A very tough call, should that be the case. Potentially hero or dead, and if it goes wrong, castigated by the 'book' and the legal profession who/which are here to defend corporate interests rather than yours.

The job of an airline pilot is,and esp Captain, [imho] not paid well-enough for the responsibility, in this day and age. I commend everyone to obtain legal insurance , pref through their IFALPA associate company. The way the system works is to try to shift corporate liability onto the individual.

I want to retire just asa I have enough money to live on ... lawyers with time and time on their side rule the world, and any decision you take can be questioned by people who can taek hours/days/weeks to review your decisions which affected real lives that you had to take in a minute or so.

[theamrad]

The Baron – I’m not sure how this relates to this accident – there’s no suggestion that the crew did anything wrong up to the point of touchdown that we know of yet – whether that changes or not – we’ll see with the FDR data etc.
Straight off the cuff, I can think of one situation where the safety factor could go straight out the window – runway condition being nowhere near that reported – whether it’s general weather phenomenon (vis, wind, shear) being different, or the real and reported braking performance/runway condition being radically different. It’s been a big feature in several notable accidents – including, if I remember correctly, the overrun at Midway.

[PEI_3721]

Some points for clarification/confirmation please – non A320 driver. Following-on from the accident reported in #284 – asymmetric reverse.
I assume that reverse is selected by reward movement of the thrust levers; reverse activates in combination with the lever position and suitable ‘on ground’ / engine speed interlocks.
Does the spoiler deployment use the same ‘on ground’ interlock; is this interlock a function of weight on wheels, or wheel spin up, or both?
What are the crew procedures for selecting reverse with one reverser inoperative; what prevents inadvertent deployment of the inoperative system if the crew pull both levers rearwards (by habit)? Do they only move one lever by crew drill, or is the rev system isolated (locked out) elect/mech?

Re hydroplaning speed, inserting pressures of 130-150psi into the chart given in the ref at post #205, there could be a wide range of possible speeds depending on tyre type, e.g. 95-110kt at 150psi or 90-105 kt at 130psi.