Mid-air collision over Brasil

[PJ2]

ekw;

Re, "If the 738 pilot pulled back with full throttle couldn't his tail sink into the bizjet? (power lag)."

and,

AlexL;

Re, "If its true that the 737 was climbing throught the embraer flight path with a significant pitch attitude, and the emb was straight and level, then a scenario which fits its that the emb winglet clipped the horizontal stabaliser of the 737, not the wing. "

That's not possible at these speeds and with these aircraft.

We must remain aware of the environment and the numbers here..ie, the speed involved and the viscosity of the air at these speeds...in short, the physics of this as has been strongly emphasized earlier in the thread.

The pitch attitude of almost all transport aircraft in level flight is typically 2 to 4 degrees NU (nose-up) depending upon type, (the L1011 is slightly higher as it uses the fuselage for lift as well; most other transports would tend towards the 2deg pitch attitude). Keep in mind physics as was emphasized earlier in this thread: - The air at these speeds is extremely "thick"...very "hard", as sensed by an airframe travelling at these speeds. (That's what "ram effect" is about, as well as temperature rise resulting from ram effect etc) This pitch attitude does not change markedly when climbing or descending...in descent we might see 1 deg to perhaps 0 (level pitch attitude) for a 2500fpm descent. Minute changes in pitch attitude have a large effect on rates of climb and descent.

There is no physical possibility therefore, that the horizontal stabilizer was struck due to "pitch attitude" of the 737 during a climb keeping in mind the Legacy's damage pattern. Neither could the other scenario, a "sudden pull-up" as was mentioned just above, possibly present an attitude at which the horizontal stab would be momentarily "exposed" to the oncoming aircraft. It's physically impossible for that to occur.

Assuming both aircraft were cruising at about 450kts TAS, the closing speed of the two aircraft would have been approximately 1519fps, (900kts x 1.69 approx). At that speed, the time to travel the length of the 737-800 (the effective time of available contact with each other) is approximately .09 seconds (138ft / 1519fps). It can be seen that even if it were possible to pull up to an attitude which would expose the tailfeathers, the time "available" for such a change in attitude to occur with a subsequent collision as described is simply not there.

The thread has also covered the airway/head-on issue, although it seems to keep coming up. As described earlier, the aircraft were on UZ6 near the TAROP intersection (Jepp SA (HI) 4), the 737 heading south, the Legacy heading north. The altitude issue is still unresolved however, and is additionally clouded by the transponder/TCAS issue which should be cleared up with the testimony of the surviving crew, the CVRs and the DFDRs.

Scurvy.D.Dog,

Re, ".. the centre section photo does not reveal anything meaningful."

I disagree. The evidence that the center section provides for us is enormous.

First, it is relatively intact. That means the descent was not "high speed", but instead had relatively little forward speed. That means that there was no vertical "dive" but some other scenario, likely inverted (as per the evidence) and possibly stalled (conjecture at this point) though the DFDR will tell us for sure, (this of course assumes that the electrics remained operational). This also means that the horizontal stabilizers were likely intact and also that both wings were likely intact, (no spiral or otherwise uncontrolled high-speed dive).

Both engines are off the wing and therefore are either near the wreckage having been thrown off on impact (and hidden by the jungle in the photo), or somewhere along the path of flight having been thrown off by lateral 'g' forces at some point during the descent. If the engines are found (very difficult in the jungle as we know) a long distance from the main wreckage, I suspect the vertical stabilizer will be found that way as well, (the photos seen so far don't reveal the relative positions of the vert stab and the center section). In other words, we may have a similar scenario as AA587 in New York (Oct or Nov 2001 if I recall).

I did observe earlier in the thread that the fuel tank inspection panels were all off on the left wing and surmised that that may have occurred on ground impact with the enormous instantaneous pressures thereby derived. I doubt if this is the result of any winglet-to-wing collision as again the geometry of such contact doesn't support the theory...the panels are inboard of the engine and any internal pressures generated by the winglet impact would also have compromised the left wing to such an extent that a spiral high-speed dive would have resulted.

Another possibility is complete mid-air disintegration in which case all conjecture above about collision paths etc becomes academic.

As to TCAS/Transponder issues, they will have to wait for the formal investigation or at least reading of the DFDRs and CVRs. I am unfamiliar with South American flying and am reading the contributions in the thread with great interest.

Fox Niner...just read your comments and agree fully, with the minor qualifier that knowing how the aircraft hit may lead us to the immediate antecedents. Whether such discoveries would provide "learning" in order to prevent future such accidents is likely doubtful in this case. I think that the answers to your questions will be where the real learning, and hopefully subsequent change, lies.