Mid-air collision over Brasil

[Rippa]

Originally Posted by jondc9

J.O.
you make a good point, or could cable to uplocks been pulled by slicing action of winglet
this will be a case of a bullet hitting a bullet.
has Brazil released any ATC radar data yet? didn't someone say that the radar showed 1000' seperation?
is it possible the pilots forgot to set 29.92 inches and were 1000' off, then switched off transponder to correct everything and just got banged?
harkens back to that film I mentioned, "the crowded sky".
somehow I have to think the legacy was on top to survive.
j

Jondc9,
Brazilian airspace is very different from the rest of the world (or at least very different from USA airspace). Usually, we set QNE (29.93 or 1013.2 hpa) a few minutes after takeoff, around 6000 feet (varies from one place to another) when climbing and QNH, when descending, around FL 040. The airspace in question is RVSM, but has very few traffic on daytime...gets a little busyer at night, due to international flights from South america (Chile Argentina, Brasil,etc...) to USA and north america, but even then, it could not be classified as a busy ACC. Very often CB's on route...big Cb'...

Regards

PS: The investigation is beeing conducted by the Military authoraties....do not expect any real info before 90 days.......

[Blues&twos]

Just had a thought which I don't think has been added to the pot yet. Is it possible that the B737 had a problem prior to and at the time unrelated the MAC? In attempting to deal with this problem departed from its assigned level?


I appreciate that this would be incredibly incredibly unlucky....but then at the end of the summer I have to clean swatted flies off my car aerial....

Added later: Mind you this doesn't explain why the Legacy couldn't take avoiding action in response to TCAS, does it?

[Carnage Matey!]

AFAIK mode C transponders all give their altitude readouts referenced to 1013.2/29.92 so even if they had forgotten to set standard on the primary altimeters the TCAS should still have functioned in the correct sense.

[satpak77]

speculating, but any chance that the cockpit windows were impacted by the Legacy? At closure of Mach 1.4+, it would be all over, forget running checklists and donning O-2 mask.

Also, anyone have an online link for ICAO rules on squawking XXX when IFR but non-radar, in South America. In Peru it was 2000 code.

thanks

[Sunfish]

I would like to draw your attention to Danny's post regarding Kinetic Energy. There needs to be zero speculation about exactly where the two jets touched. You can safely assume that at the closing velocities involved, it simply doesn't matter. It's purely academic and discussion is of no possible value.

For the record, winglets and wingtips are deliberately designed to fail at much lower loads than the rest of the wing - to protect the integrity of the wing structure.

[jondc9]

carnage

of course that is how mode c works, but could this have been the reason the legacy pilots are alleged to have shutoff the transponder?

as to lowering gear on a 737 emergency descent, it is an option, but one must reduce to gear speed first.


and I posted earlier slicing into the windshield/canopy/cockpit might have been part of the equation.

I have heard that new planes may have altimeters improperly set and the pilots didn't catch it on checklist.



AS to kinetic energy and all that JAZZ, please remember that a C172 brought down a PSA B727 near San Diego about 34 years ago, someone even got a pulitzer prize winning picture of it in flames. A c172 has much less mass and speed behind it than a legacy so it can happen.

[jondc9]

hobie

thanks for that picture...hit the engines with winglet and stab hits cockpit

ouch

but wait for the paint marks I suppose

thanks again!

jon

[jondc9]

stuff on PSA mid air near San Diego, almost 28 years ago to the day.


http://en.wikipedia.org/wiki/PSA_Flight_182

amazing picture

[PJ2]

Originally Posted by satpak77

speculating, but any chance that the cockpit windows were impacted by the Legacy?

Satpak77;

I don't think so. Damage to the Legacy is on the left tips of two extremities...the winglet perhaps a foot+ and horizontal stabilizer, mere inches. If the diagram of the 737 and Legacy relative sizes posted earlier is referred to, it can be seen that the horizontal stabilizer could not impact the cockpit area without substantial damage to the Legacy and that evidence is not there. The winglet could not impact the cockpit area of the 737 at least in any substantial way on a straight-on heading as there would simply be far more damage to the Legacy than is apparent.

Considering a collision with the vertical stabilizer with the Legacy at a steep (evasive) bank angle, the Legacy's winglet and horizontal stabilizer are too far apart to have sustained damage by such a strike unless the winglet struck the 737's vertical stab and was in turn struck (instantaneously, much like the shuttle foam strike) by the horizontal stabilizer.

Given the distribution pattern of the main wreckage (close, with large wing sections intact so no high-speed impact-, no engines - either close by hidden by jungle or separated in flight due possibly due to high lateral loads-, gear down in a possible attempt to stabilize the aircraft), a collision with the vertical stabilizer is one possible scenario. All the fuel inspection panels are off perhaps due to very high pressures generated in the wing section on impact. In-flight break-up cannot be ruled out of course, as the photographs do not yet show all the wreckage.

A tragic day for aviation and a very sad for all families of the victims.

[SM4 Pirate]

Originally Posted by SeniorDispatcher

Looks like they're confirming it was a MAC...
http://noticias.terra.com.br/brasil/...EI7792,00.html

Rough translation:

The Anac (National Agency of Civil Aviation) confirmed in this Sunday that the fall of Boeing 737-800 of GOL that crashed on Friday in the north of the Mato Grosso was provoked by the collision with an airplane Legacy model, Embrear.

According to Denise Abreu, director of the Anac, there is little possibility of finding survivors. "It will take a miracle to find survivors".

In accordance with process, they have successfully removed the black boxes of the Legacy. "The boxes of voice and data are in perfect condition".

From this Sunday, the Anac created a contact list for passengers that will be co-ordinated by Laura Perdigão. It promised information to the families at least two times a day.

The director also informed that North American authorities are in contact with Brazil to help in the inquiries of the accident. According to it, this type of intervention is absolutely normal in cases involving aircraft of two nationalities. The Legacy manufactured in Brazil, had been bought by a company of the United States, and therefore, it is not under the Brazilian authority.

[RobertS975]

One of the pax on the biz-jet was allegedly a New York Times reporter... has he filed any stories yet? It is obviously rare when you have a reporter so involved in the story.

[punkalouver]

Originally Posted by DH121

Maybe the 737 was overstressed in trying to avoid the collission?

It is possible to lose control during an evasive manouver like this 727.

http://aviation-safety.net/database/...1107-0&lang=en

[SeniorDispatcher]

Originally Posted by RobertS975

One of the pax on the biz-jet was allegedly a New York Times reporter... has he filed any stories yet? It is obviously rare when you have a reporter so involved in the story.

His most recent was 9/26, and nothing since then.

http://topics.nytimes.com/top/refere...key/index.html

I'm looking forward to hearing his account, assuming that he writes one...

[RatherBeFlying]

My recollection of the San Diego accident was that the C-172 was first impacted by the B-727 nosewheel from where it contacted the leading edge and severed the hydraulic lines for all three systems.

Where the hydraulic lines are located in new B-737s I do not know.

[discountinvestigator]

First ideas

I have a little bit of experience in the area of mid-air collision investigation.

Firstly, this is not the first, or the last mid-air. Remember that we had a loss of control following a near mid-air in Nigeria with the B727 about 10 years ago. So, if the Boeing crew did detect the Legacy and pulled/pushed/whatever, loss of control is not unknown. We have also had a relatively recent collision with a B737 and a Cessna twin where both survived in Namibia. Small aircraft do hit big aircraft and survive.

I have the T-shirt for the German mid-air collision.

Second, remember that there are slight nose up attitudes to take into account.

Third, the pilot statement is entirely compatible with those I have talked to/read and the theory for detection. You don't see the one you are going to hit. Get a hold of a copy of the old Bureau of Air Safety Investigation report (now Australian TSB) into See and Avoid. A brilliant piece of research.

Fourth, remember the cross wing factor. If you are going to try to avoid, then most pilots bank to turn rather than pull/push for head on encounters, this makes it worse! Draw it out on a piece of paper and you will see that the wings form an X shape and are thus more likely to hit one another.

Fifth, I would make a first guess at the Legacy being slightly lower than the Boeing. This could give you a tail hit on the underside of the wing and the winglet in the engine. However, please remember, this is just an alternative way of getting that damage. The tail of the Legacy just impacts one of the flap drive pontoon aerodynamic fairings, leading to not much damage.

The Boeing looks in pretty good shape, albeit the wrong way up. The engines have gone which is not unusual but would imply more of a loss of vertical stabiliser and then massive yawing, or loss through impact. However, with both engines gone, it may well be more the descent phase. Certainly the 757 in Germany lost the engines for that reason.

The vertical speed of the Boeing does not look great and it was certainly not a nosedive into the ground in one piece. 737 old generation could suffer in flight break up if power dived towards the ground. It just does not look bent enough for that. However, trees can do a lot of deceleration!

Anybody got any idea why the fairings to the front of the main gear are missing? Are they actually there and have just rotated in the accident to leave the area exposed?

The port wing has lost all of the inspection panels but the right wing has not. The port wing appears to carry significant damage, probably in the ground impact and may well have twisted off at that point, whereas the starboard wing in still attached.

The broken link on the left main gear may support the inverted left wing down stop as the gear might be weaker in this direction, when compared with the reverse fitting on the other side.

Ah well, time will tell.

[Ranger One]

Originally Posted by Danny

This thread is about to get shut down. Far too many indications of enthusiasts debating the scenarios whilst showing a severe lack of even basic physics understanding.
If you don't understand the concept of kinetic energy then please leave this debate alone. Those that fail to grasp even the rudimentary idea that a collision, whether it was just a winglet striking another part of a bigger aircraft or whatever, involves tremendous forces. It's not Hollywood fantasy.

Spot on Danny. Let's throw a few rough assumptive numbers in here so people can get a clue.
Assumption: Legacy winglet weighs 20kg.
Assumption: MAC was something relatively close to head-on, with a closing velocity of 400m/s (assuming both aircraft were cruising at something like 450kts).
Now, the equation for kinetic energy is:

Note that Ek is proportional to the *square* of the velocity. Plug the above numbers in, and we get an energy in the winglet of 1,600,000 joules.
For comparison, take a 2 ton (2000kg) car travelling at 45mph - say 20m/s. That has an energy of only 400,000 joules - which would be the same number as the winglet energy if the Boeing was stationary WRT the Legacy, i.e. they were on headings 90 degrees apart rather than reciprocal.
How would YOU like four cars at 45mph hitting your office? That's the kind of energy we're talking about, folks. The only reason the Legacy got away so lightly is that the winglet *was* frangible, and the structure failed, as designed, before much of the energy was transferred to the Legacy. It mostly ended up in the Boeing...
(I've had a couple of beers so if I've made any horrific errors of sign or magnitude someone please correct me)
R1

[broadreach]

Following up on my earlier post (#77 in this thread) re a report quoting the Legacy captain saying he'd turned the transponder off and climbed without advising ATC, a subsequent news report covering the crew's deposition to police at Cuiabá, has the crew stating they were in stable cruise at FL 370, the level to which they had been cleared by ATC. The same article mentions the crew's stating their TCAS gave no warning.

Another news article quotes a farm labourer who saw the 738 coming down saying it was "tumbling" or "spinning" (in Portuguese, "rodopiando").

Other articles indicate the wreckage was concentrated in a 1km2 area or "spread over 10km2".

Re geometry and, for what it's worth, someone has posted a theoretical simulation of winglet contacts on youtube: http://www.youtube.com/watch?v=wRKtG3qoUcU&eurl=

Someone in an earlier post mentioned trees in the forest where the 738 crashed being over 20' tall. More like 40m tall, ie the forest canopy at a height equivalent to a 13 storey building. Reports from the first airforce rescue team helilifted in indicate there was fire. But that height of forest canopy would have muffled any explosion.

Just a note re ANAC, Brazil's new civil aviation agency. Very recently created, mostly political nominees and probably somewhat over their heads in this, likely to be playing catch-up with the military people directly involved in the investigation. Don't expect much real information to be forthcoming from that quarter. On the other hand I would certainly expect a rapid stream of hard information coming through directly or otherwise from other sources including airforce over the next few days.

[discountinvestigator]

Birdstrike

Can somebody remind me what the birdstrike criteria are for the engine of a 737 diameter. One kg and 200 kts strikes me from memory. I will repost the right answer when my bird specialist is awake.

20kg of winglet down the engine may well cause total detachment, in the designed failure manner shown on the photos.

OK, looking at the simulation, I could go with that, as opposed to my blind thought on the underside/engine strike on the 737. Sometimes you forget how big the 145 is. It just feels very small when you get to sit in one for a while at my height!

The impact of the frangible winglet with the wing will easily lead to the winglet of the Legacy being smashed off, no problem. The outer element of the T tail being lost as well, fine. However, when the winglet has smashed its way through the slats, it comes across the main wing box. These are very very strong. Something just feels funny about the winglet doing sufficient damage to destroy enough of the wing to make a difference at this point. Certainly when compared to the fin of the 757 (two tonnes of Seattle's finest) hitting the front of the 154 wing root, it did not do that much damage to the wing box, from memory. Maybe the ironworks from Tupolev win out over the NG wing here.

Now, the loss of the winglet on the NG wing is an interesting proposition. I would have assumed that the change in lift at the wing extremity should be counteractable by normal roll control systems. No doubt Mr Blended Winglets will be busy for the next few days.

At least these aircraft should not have the Gillham code and the FL 350/370 problem.

Also remember that when you see an aircraft 1000 feet below you, it looks as if it is on the same level, such is the deception of the false horizon and the nose up attitudes. At least in some cases.

Does anybody know what the factory acceptance tests are for TCAS. Just wondering if the Legacy had a failed unit of some form or other, and they had never seen another aircraft on the display, because they were not expecting to. So, plug in the bench tests stuff and it looks ok, but is there a practical air test of it? Not necessarily in terms of resolution, but just being aware of other traffic?

[ExSimGuy]

Danny, I hope you won't lock or delete the thread. I know it's all speculation at this point in time, but the "Hollywood ideas" get shot down by more informed posters (and the originators educated, along with others of us) and it keeps a centralised source of info as it comes in (like the post above about the light jet being "straight and level with (implied) the transponder on")

Certainly a good point comparing that "light piece of composite" with it hitting an aircraft (or my car!) at around 1,000 mph

ESG

[willfly380]

a close call just a few days back

just like to share this. a few days back a b737-400 came to about 200ft within to a su35 fighter plane . it was so close i believe that the boeing capt had to firewall the engines in order to avoid hitting the fighter. the fighter had some tech problems[i have no clue]so had his tranponder on , hence they got a TA immediately followed by an RA. now we all know about RAs issued being in the normal operating capability of the airplanes, but this was really really necessary to go to the forward stop [ thrust lever position]to avoid as the fighter was zooming. the fighter pilot i believe also did a stellar job and infact turned around to check if the boeing was ok . on finding him still flying he resumed his flight.I am here not trying to fix blame or comment on actions taken, just sharing to educate the fellow pilot, the 734 was grounded for a boroscopic inspection on landing.