Mid-air collision over Brasil
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mercenary pilot is right to a degree, the 737 does have manual control reversion in a limited sense...NO RUDDER control with loss of hydraulics, elevator and ailerons would remain unless the cables were sliced too.
mercenary brings up a good point about the 747 that lost chunks of tail due to failure of aft bulkhead (pressure bulkhead, not properly repaired). however it should be noted that the 747 flew for a bit of time after this happened.
I think the more we talk about it, the more we see that this was quite an accident, with so many possible answers.
sometimes the simplest is the answer, which is why I keep coming back to the boeing pilots being killed by a piece of the legacy, followed by decompression, autopilot disengagement and loss of control.
I have a feeling we will know the answer sooner than later on this one.
mercenary brings up a good point about the 747 that lost chunks of tail due to failure of aft bulkhead (pressure bulkhead, not properly repaired). however it should be noted that the 747 flew for a bit of time after this happened.
I think the more we talk about it, the more we see that this was quite an accident, with so many possible answers.
sometimes the simplest is the answer, which is why I keep coming back to the boeing pilots being killed by a piece of the legacy, followed by decompression, autopilot disengagement and loss of control.
I have a feeling we will know the answer sooner than later on this one.
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I generally hate to speculate on these things, but having said that, heres my tuppenceworth.
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. Neither would have seen each other, apart from the emb would have seen the 737 flash over his head for a few milliseconds. The winglet could concievably remove the entire stabalizer, but even if not at that altitude and speed a sudden trim change, and / or aileron damage could cause a major upset which would be difficult if not impossible to recover with a damaged stab
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. Neither would have seen each other, apart from the emb would have seen the 737 flash over his head for a few milliseconds. The winglet could concievably remove the entire stabalizer, but even if not at that altitude and speed a sudden trim change, and / or aileron damage could cause a major upset which would be difficult if not impossible to recover with a damaged stab
mercenary pilot is right to a degree, the 737 does have manual control reversion in a limited sense...NO RUDDER control with loss of hydraulics, elevator and ailerons would remain unless the cables were sliced too.
mercenary brings up a good point about the 747 that lost chunks of tail due to failure of aft bulkhead (pressure bulkhead, not properly repaired). however it should be noted that the 747 flew for a bit of time after this happened.
I think the more we talk about it, the more we see that this was quite an accident, with so many possible answers.
sometimes the simplest is the answer, which is why I keep coming back to the boeing pilots being killed by a piece of the legacy, followed by decompression, autopilot disengagement and loss of control.
I have a feeling we will know the answer sooner than later on this one.
mercenary brings up a good point about the 747 that lost chunks of tail due to failure of aft bulkhead (pressure bulkhead, not properly repaired). however it should be noted that the 747 flew for a bit of time after this happened.
I think the more we talk about it, the more we see that this was quite an accident, with so many possible answers.
sometimes the simplest is the answer, which is why I keep coming back to the boeing pilots being killed by a piece of the legacy, followed by decompression, autopilot disengagement and loss of control.
I have a feeling we will know the answer sooner than later on this one.
The gear can be lowered without hydraulic power. once again, the 737 can be brought to a safe stop without a drop of hydraulic fluid on board.
Evidently, the 737 was unable to stay aloft. What's more interesting is the reason why the two planes met each other. That is the primary cause of the accident, not the fact the landing gear was up/down, of whether they had loss of system A and/or B. Neither is it relevant to know exactly HOW the two planes collided. That is all secondary....
- Who didn't follow the RA, and why?
- Who caused the planes to be up there in the first place?
- Did ATC clear them? Did one of them climb / change level without informing ATC?
- Did one of them indeed turn off their transponder?
- Was ATC aware of an impending collision?
If these questions are answered in due time, will we all know the cause of the accident...
FN
Evidently, the 737 was unable to stay aloft. What's more interesting is the reason why the two planes met each other. That is the primary cause of the accident, not the fact the landing gear was up/down, of whether they had loss of system A and/or B. Neither is it relevant to know exactly HOW the two planes collided. That is all secondary....
- Who didn't follow the RA, and why?
- Who caused the planes to be up there in the first place?
- Did ATC clear them? Did one of them climb / change level without informing ATC?
- Did one of them indeed turn off their transponder?
- Was ATC aware of an impending collision?
If these questions are answered in due time, will we all know the cause of the accident...
FN
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.
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.
Last edited by PJ2; 2nd Oct 2006 at 21:22. Reason: Formatting
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I read it that he was saying, basically, that if the pilots met their end at the instant the Legacy hit, as per JonDC9's suggestion, then (notwithstanding the hydraulic situation), the gear would not have been in the down position in the photograph we've all seen.
I have to say I think Blues&Twos has a pretty sound point, tbh.
Poor souls.
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FYI: Here's an excerpt, not from the (copyrighted) Jepps, but rather, the freely available US Government H4...
As noted earlier, we're talking about the neighborhood of TAROP intersection. Just as an aside, I'd be interested to know if SBR620/the Cachimbo test site might have been doing anything that might have spilled out of their airspace and been some sort of factor in this accident...
I've also uploaded the entire H4 here: http://www.atcmuseum.org/images/H4.pdf. Note that it is about 4.25 megs.
Dave
As noted earlier, we're talking about the neighborhood of TAROP intersection. Just as an aside, I'd be interested to know if SBR620/the Cachimbo test site might have been doing anything that might have spilled out of their airspace and been some sort of factor in this accident...
I've also uploaded the entire H4 here: http://www.atcmuseum.org/images/H4.pdf. Note that it is about 4.25 megs.
Dave
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For what it is worth and I doubt it should be taken seriously.
Clarin, one of the the national Argentine newspapers is reporting as follows.(rough translation)
One of the aeroplanes was authorised by the tower at Brasilia to fly at 37000 feet,the other was authorised by Manaos to climb from 35000 feet to 39000 feet and that the collision was caused by a lack of communication between the "towers"
Make of it what you will, I just thought you may want to see what's being reported down that way.
Clarin, one of the the national Argentine newspapers is reporting as follows.(rough translation)
One of the aeroplanes was authorised by the tower at Brasilia to fly at 37000 feet,the other was authorised by Manaos to climb from 35000 feet to 39000 feet and that the collision was caused by a lack of communication between the "towers"
Make of it what you will, I just thought you may want to see what's being reported down that way.
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who would have lowered the gear?
if all the hydraulics ran out and the cable to the uplocks had been yanked by the impact, the gear could have free falled.
there may be other answers too
and, was the NOSE gear found down?
I believe one of our forum members suggested that something went wrong with the 737 prior to any collision. this should not be discounted yet/
why?
if a rapid decompression had happened and a descent started and that descent took the 737 into the legacy, we may have a clue
again, this is just to sort of cleanse the pallet of the mind...I admit that when I first heard this story, my first thought was that that LEGACY had hit the 737...the story seems to be falling to the 737 hit the LEGACY...we shall see in time.
jon
if all the hydraulics ran out and the cable to the uplocks had been yanked by the impact, the gear could have free falled.
there may be other answers too
and, was the NOSE gear found down?
I believe one of our forum members suggested that something went wrong with the 737 prior to any collision. this should not be discounted yet/
why?
if a rapid decompression had happened and a descent started and that descent took the 737 into the legacy, we may have a clue
again, this is just to sort of cleanse the pallet of the mind...I admit that when I first heard this story, my first thought was that that LEGACY had hit the 737...the story seems to be falling to the 737 hit the LEGACY...we shall see in time.
jon
jondc9;
Re, "the cable to the uplocks "
Help me out here...this is the second or third reference to "cable" uplocks...is the 737 not equipped with hydraulic uplocks like all other conventional transport category aircraft?
Cheers,
PJ2
Re, "the cable to the uplocks "
Help me out here...this is the second or third reference to "cable" uplocks...is the 737 not equipped with hydraulic uplocks like all other conventional transport category aircraft?
Cheers,
PJ2
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dear P2J
you ask a fine question, and just to be sure I got out my 737 manual (200 series, but I doubt much has changed, please corect me if I am wrong).
from the manual:
Manual extension is provided by three emergency landing gear extension handles located under an access door in the cockpit floor. Pulling a handle to is full extension will unlock the uplock on the associated landing gear.
To assure that free fall of the gear is unimpeded by trapped hydraulic pressure, the landing gear handle should be in the OFF position.
I hope this helps. Tongue twister there: unlock the uplock...should be used to find out if pilot is drunk! (kidding to all of you drunk pilots).
you ask a fine question, and just to be sure I got out my 737 manual (200 series, but I doubt much has changed, please corect me if I am wrong).
from the manual:
Manual extension is provided by three emergency landing gear extension handles located under an access door in the cockpit floor. Pulling a handle to is full extension will unlock the uplock on the associated landing gear.
To assure that free fall of the gear is unimpeded by trapped hydraulic pressure, the landing gear handle should be in the OFF position.
I hope this helps. Tongue twister there: unlock the uplock...should be used to find out if pilot is drunk! (kidding to all of you drunk pilots).
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Someone previously asked if Joe Sharkey, the NYT reporter onboard the Legacy, had written anything post-accident, and this link just got forwarded to me. He doesn't say much that's new, but some folks might find something useful within it...
http://www.joesharkey.com/
http://www.joesharkey.com/
jondc9;
Ok thanks. To be clear then, the normal uplocks are hydraulically-driven (vice mechanical and spring action), but the emergency gear extension is achieved by cable?
The cable routing is almost certainly well inboard (fuselage, then outboard to the gear). Whether the collision and/or the subsequent accident sequence had anything to do with inadvertent gear extension or whether the crew extended the gear then, remains to be determined. Thanks for the info.
Ok thanks. To be clear then, the normal uplocks are hydraulically-driven (vice mechanical and spring action), but the emergency gear extension is achieved by cable?
The cable routing is almost certainly well inboard (fuselage, then outboard to the gear). Whether the collision and/or the subsequent accident sequence had anything to do with inadvertent gear extension or whether the crew extended the gear then, remains to be determined. Thanks for the info.
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Looks like they have found the CVR and DFDR of the 737..
http://g1.globo.com/Noticias/Brasil/...4-5598,00.html
http://g1.globo.com/Noticias/Brasil/...4-5598,00.html
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Looks like they have found the CVR and DFDR of the 737..
http://g1.globo.com/Noticias/Brasil/...4-5598,00.html
http://g1.globo.com/Noticias/Brasil/...4-5598,00.html
Pegase Driver
For Portuguese readers:
http://oglobo.globo.com/pais/mat/200.../285929322.asp
The article indicates the Legacy was at FL370, still under Brasilia ATC, while the 738 had requested and been cleared by Manaus ATC to climb from FL350 to 390.
.
http://oglobo.globo.com/pais/mat/200.../285929322.asp
The article indicates the Legacy was at FL370, still under Brasilia ATC, while the 738 had requested and been cleared by Manaus ATC to climb from FL350 to 390.
.
Speculations :Lack of estimate ( therefore knowledge )of the Legacy to Manaus ACC , or no coordination of the 738 climb to Brasilia ,or too slow rate of climb undetected, or intentional/unitentional level off during the climb, etc, I have seen all of those many , many times in my carreer.
As to TCAS, only the both FDR/CVRs will tell us why the system ( i.e humans , procedures or technics ) malfunctionned.
TCAS has never claimed it will be error free and will cover for every case.
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Some hi-res photos now up on the military's site...
http://www.fab.mil.br/imprensa/Notic...os_resgate.htm
http://www.fab.mil.br/imprensa/Notic...os_resgate.htm
With the greatest of respect to those wondering why the main gears were down, it is possible that they were not lowered intentionally at all. If in fact, there was an explosive decompression, the floor may fail and the various control cables are right underneath.
