Continental 737 Off Runway at DEN
pif;
Interesting info.
Probably mis-heard that, because that is an incorrect and, if you think about it for half a second, an entirely illogical statement. The crash recorder (DFDR) is typically designed to withstand instantaneous 'g' forces in the neighbourhood of 3000g's, for obvious reasons.
The only time the recorder shuts off is when there's no more electricity on the AC (#1 on the 320, not sure on the 73') and possibly DC busses. The recorder likely quit when one or both of the engines quit either through cockpit actions, (fuel levers off -possible but not likely) or more likely, destruction of the engine upon hitting the berm, or separation of the left engine from the aircraft.
For me, unless it was a left brake that possibly seized, the brake theory alone doesn't explain the excursion. Neither does a failed engine - on it's own. These guys were almost certainly highly experienced, and the practising of engine failures in all kinds of conditions in the simulator is routine training. I know that a seized brake alone is controllable - (if I recall from some time ago, on takeoff I think) an A320 in LAS had a complete brake seizure and stayed right on the centerline, although I don't think there was a 24kt crosswind.
Interesting info.
takes a 3g shock to shut off the recorders.
The only time the recorder shuts off is when there's no more electricity on the AC (#1 on the 320, not sure on the 73') and possibly DC busses. The recorder likely quit when one or both of the engines quit either through cockpit actions, (fuel levers off -possible but not likely) or more likely, destruction of the engine upon hitting the berm, or separation of the left engine from the aircraft.
For me, unless it was a left brake that possibly seized, the brake theory alone doesn't explain the excursion. Neither does a failed engine - on it's own. These guys were almost certainly highly experienced, and the practising of engine failures in all kinds of conditions in the simulator is routine training. I know that a seized brake alone is controllable - (if I recall from some time ago, on takeoff I think) an A320 in LAS had a complete brake seizure and stayed right on the centerline, although I don't think there was a 24kt crosswind.
PJ2 - well I wondered about that too, but the NTSB guy speaking was very clear (if wrong) in saying that there was a G-load switch that would shut down the recorders (disk-drive protection?)... anyway...
EDIT: Actually - take a look at this hot-off-the-press AAIB report on a different crash which specifically refers to 3g switches on recorders (designed to stop them in the event of heavy shock to prevent data overwrites, but highly disapproved of by the AAIB...) on the bottom of pg 27 (pg 7 of the pdf document) and following:
http://www.aaib.dft.gov.uk/cms_resou...RC%2012-08.pdf
EDIT: Actually - take a look at this hot-off-the-press AAIB report on a different crash which specifically refers to 3g switches on recorders (designed to stop them in the event of heavy shock to prevent data overwrites, but highly disapproved of by the AAIB...) on the bottom of pg 27 (pg 7 of the pdf document) and following:
http://www.aaib.dft.gov.uk/cms_resou...RC%2012-08.pdf
Last edited by pattern_is_full; 23rd Dec 2008 at 06:25.
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Landing gear looks okay
The NTSB is saying the landing gear, brakes and tyres are okay:
NTSB: Wheels, brakes didn't cause Continental accident - CNN.com
NTSB: Wheels, brakes didn't cause Continental accident - CNN.com
Good photo on airliners.net showing the vertical displacement from runway/taxiway level. It pretty much explains the fuselage and other damage.
Photos: Boeing 737-524 Aircraft Pictures | Airliners.net
Photos: Boeing 737-524 Aircraft Pictures | Airliners.net
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Investigators Confirm Crew TOR
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If you wish to keep your blood pressure down do NOT read Crash Probe Focuses on Risky Maneuver - WSJ.com
Where do they find them?
Where do they find them?
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PJ2,
Yes it does take a vertical impact as little as 3G's to shut down both the recorders.The key word here being "shut down".
Having said that, yes,both recorders can withstand G's as high as 3,900g's.Keep in mind these high g's are tested for a maximum of 1/1000th of a second.That is to say for the moment of impact.Therefore it would be incorrect that these recorders can "withstand upto say 3,900g's".That statment would definitely not be true.
More importantly is another fact i'm making.The boxes cant make an impact of upto 3900g's AND KEEP RUNNING! They would've shut off on the first impact exceeding 3g's.BUT the design of the boxes is such that the data within would be completely retrievable even after 'momentary' g forces as high as 3,900 g's.Therefore making them "indestructible".
I would'nt want to live so long as to be able to see the day when a harddrive continues to function even after a 3,000+ G-shock....!! Cause I never will!!
Then there is the 'switch off logic'.Which requires the boxes to stop recording when the power cord is pulled or a 3g+ impact.In both cases the logic assumes that a crash has taken place and therefore there would be nothing more to record! This in my personal opinion is a design fault and needs to be rectified.As has been proven time and again when critical data was'nt available due recorders shutdown.For example dual engine failure on older airplanes.Or complete electrical loss on the same.OR,for that matter,a runway excursion such as this one,followed by a low G impact.Of course modern jets have worked around the problem by having an alternate sourceof power(such as RAT) to power critical systems,but I for one would much rather have a recorder which continues to run at least for a minute or so,on its own power,after the shut down logic has taken over.
Unless of course........(we could go on here).
What was the braking coefficient reported(if any).Because,a port engine failure at takeoff,coupled with a gusty wind from the port(weathercock effect) along with a marginally slippery runway and maybe less than perfect handling of it all, could well result in a runway excursion such as this one.
My two cents worth......
Now onto the real facts......
Yes it does take a vertical impact as little as 3G's to shut down both the recorders.The key word here being "shut down".
Having said that, yes,both recorders can withstand G's as high as 3,900g's.Keep in mind these high g's are tested for a maximum of 1/1000th of a second.That is to say for the moment of impact.Therefore it would be incorrect that these recorders can "withstand upto say 3,900g's".That statment would definitely not be true.
More importantly is another fact i'm making.The boxes cant make an impact of upto 3900g's AND KEEP RUNNING! They would've shut off on the first impact exceeding 3g's.BUT the design of the boxes is such that the data within would be completely retrievable even after 'momentary' g forces as high as 3,900 g's.Therefore making them "indestructible".
I would'nt want to live so long as to be able to see the day when a harddrive continues to function even after a 3,000+ G-shock....!! Cause I never will!!
Then there is the 'switch off logic'.Which requires the boxes to stop recording when the power cord is pulled or a 3g+ impact.In both cases the logic assumes that a crash has taken place and therefore there would be nothing more to record! This in my personal opinion is a design fault and needs to be rectified.As has been proven time and again when critical data was'nt available due recorders shutdown.For example dual engine failure on older airplanes.Or complete electrical loss on the same.OR,for that matter,a runway excursion such as this one,followed by a low G impact.Of course modern jets have worked around the problem by having an alternate sourceof power(such as RAT) to power critical systems,but I for one would much rather have a recorder which continues to run at least for a minute or so,on its own power,after the shut down logic has taken over.
Unless of course........(we could go on here).
What was the braking coefficient reported(if any).Because,a port engine failure at takeoff,coupled with a gusty wind from the port(weathercock effect) along with a marginally slippery runway and maybe less than perfect handling of it all, could well result in a runway excursion such as this one.
My two cents worth......
Now onto the real facts......
Last edited by Flaperon777; 23rd Dec 2008 at 15:31.
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"Unusual Sound"
= rolling with one main-mount tire on the port bogey deflated/underinflated/deflating - yet undetected and causing detectable vibration only latterly (once at high-speed), as it flailed, broke up and provoked a subsequent directional control issue - causing the abort (GETS MY VOTE FOR LIKELIHOOD).
This would also explain the ensuing divergence and departure from the runway.
.
This would also explain the ensuing divergence and departure from the runway.
.
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Originally Posted by Flaperon
Because,a port engine failure at takeoff,coupled with a gusty wind from the starboard along with a marginally slippery runway and maybe less than perfect handling of it all, could well result in a runway excursion such as this one.
Met reports ('real facts'?) indicate wind from the left
For TheShadow -from the papers, quote from NSTB man:
"The brakes showed no leaks, no locked brakes," Sumwalt told reporters late Monday, adding that the brake pads "looked good."
He said tire marks indicate that all four main landing gear were inflated."
Next?!
Flaperon777;
Well, that's a new one on me and I've been doing this for a long time now! ;-) - I have seen landings greater than 3g's in the data and the recorders (DFDR/FDIU and QAR) kept running so there must be more to this than a simple shutdown. Your clarifications are appreciated - now my curiosity's up!
Fully concur with your views on keeping recorders running. The Swissair 111 accident was a case in point. Once the main AC busses quit, the recordings stop - I should have thought it entirely logical to have a back up to keep both going for, say, between 15 and 30 minutes but even today, nothing has been done to advance this obvious need.
On the braking, the runway was reported as bare-and-dry. The crosswind component was around 24kts (using the METARS provided earlier in the thread) and gusty conditions (in this case, from port), aren't normally a problem to control. A port engine failure and a strong port wind would tend to swing the airplane to port but again, we practise this kind of scenario in the simulator all the time - it isn't a problem providing you get on it immediately.
That said, the A320 WILL, without fail, take a dirty dart for the weeds with an engine failure below about 72kts and one has to be very fast and very aggressive to keep the airplane on the runway...in zero wind at that.
pattern-is-full;
Thanks for the link to the Global Express pdf file - again very interesting. I certainly agree with the AAIB's remarks! That said, detecting when a crash has occurred such that the recorders need to be shut down. As the report states, there aren't many (if any) circumstances where the recorders have been able to function after the accident...
Well, that's a new one on me and I've been doing this for a long time now! ;-) - I have seen landings greater than 3g's in the data and the recorders (DFDR/FDIU and QAR) kept running so there must be more to this than a simple shutdown. Your clarifications are appreciated - now my curiosity's up!
Fully concur with your views on keeping recorders running. The Swissair 111 accident was a case in point. Once the main AC busses quit, the recordings stop - I should have thought it entirely logical to have a back up to keep both going for, say, between 15 and 30 minutes but even today, nothing has been done to advance this obvious need.
On the braking, the runway was reported as bare-and-dry. The crosswind component was around 24kts (using the METARS provided earlier in the thread) and gusty conditions (in this case, from port), aren't normally a problem to control. A port engine failure and a strong port wind would tend to swing the airplane to port but again, we practise this kind of scenario in the simulator all the time - it isn't a problem providing you get on it immediately.
That said, the A320 WILL, without fail, take a dirty dart for the weeds with an engine failure below about 72kts and one has to be very fast and very aggressive to keep the airplane on the runway...in zero wind at that.
pattern-is-full;
Thanks for the link to the Global Express pdf file - again very interesting. I certainly agree with the AAIB's remarks! That said, detecting when a crash has occurred such that the recorders need to be shut down. As the report states, there aren't many (if any) circumstances where the recorders have been able to function after the accident...
Last edited by PJ2; 23rd Dec 2008 at 12:52. Reason: respond to pif
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From pattern_is_full link.
The system included an ‘impact’ or ‘g’ switch interlock, designed to cut the power to the CVR in the event of a significant crash impact. The switch operates by sensing acceleration and removing the power supply to the CVR in the event of the acceleration exceeding 3G. The switch was mounted in the rear section of the aircraft, at a 45 degree incline to the longitudinal axis. The 3G threshold was therefore a combination of the aircraft’s normal and longitudinal accelerations.
The system included an ‘impact’ or ‘g’ switch interlock, designed to cut the power to the CVR in the event of a significant crash impact. The switch operates by sensing acceleration and removing the power supply to the CVR in the event of the acceleration exceeding 3G. The switch was mounted in the rear section of the aircraft, at a 45 degree incline to the longitudinal axis. The 3G threshold was therefore a combination of the aircraft’s normal and longitudinal accelerations.
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Did they ever have a solid reason why the B-737 would roll over and head straight down?
I was thinking, though, that a rudder event, either hardover or manual reversion in a 24 knot crosswind at or about rotation might be cause for one of those "aircraft incapable of flight" decisions after V1 to keep it on the ground.
Not implying anything of the sort happened in Denver, I'm a wait for the facts type, but the scenario would make sense as a possibility.
forget;
Also from the link, the following recommendation (of a few):
As I say, the presence of a 'g' switch was a surprise to me, although I can see the reason (but perhaps not the need) for same. This is, as your quote from the report states, not a 'g' force normal to one plane either - it is 45deg to the vertical/longitudinal axiis and is the sum of 'g' forces in these two axiis. I can see the reason for the AAIB's concern.
Darn poor day when you don't learn something...
Also from the link, the following recommendation (of a few):
Safety Recommendation 2008-074
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency review the certification requirements for automatically stopping flight recorders within 10 minutes after a crash impact, with a view to including a specific reference prohibiting the use of ‘g’ switches as a means of compliance as recommended in ED112 issued by EUROCAE Working Group 50.
It is recommended that the Federal Aviation Administration and the European Aviation Safety Agency review the certification requirements for automatically stopping flight recorders within 10 minutes after a crash impact, with a view to including a specific reference prohibiting the use of ‘g’ switches as a means of compliance as recommended in ED112 issued by EUROCAE Working Group 50.
Darn poor day when you don't learn something...
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Bumping and rattling
Perhaps add to the previous conjecture that a section of loose (but not yet detached) tread on any tire can cause the sort of bumping and rattling (i.e. rotational asymmetry) that was noted during the take-off [and caused them to abort from 119kts].
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What Sumwalt actually said was (more completely):
.
"Mr. Sumwalt said the bumping and rattling sound was first heard 41 seconds after the plane started down the runway, according to the Associated Press. Four seconds later, one of the crew members called for the takeoff to be aborted. Mr. Sumwalt said investigators have found no problems with the plane's engines, tires or brakes, but aren't ruling anything out. Investigators found that the plane's flight control surfaces -- including flaps, slats and speed brakes -- were in proper position. And there was no indication of locked brakes."
.
What Sumwalt actually said was (more completely):
.
"Mr. Sumwalt said the bumping and rattling sound was first heard 41 seconds after the plane started down the runway, according to the Associated Press. Four seconds later, one of the crew members called for the takeoff to be aborted. Mr. Sumwalt said investigators have found no problems with the plane's engines, tires or brakes, but aren't ruling anything out. Investigators found that the plane's flight control surfaces -- including flaps, slats and speed brakes -- were in proper position. And there was no indication of locked brakes."
If I remember it right, the FAA has been demanding enhanced flight recorders since 2005, and GE has a new model out for the 787. One of the demands the FAA made in the new regulations was an independent power source for at least 10 minutes for the boxes.
GE Aviation to commence delivery of flight recorders for Boeing 787. | Transportation > Transportation Navigation & Tracking Systems from AllBusiness.com
GE Aviation to commence delivery of flight recorders for Boeing 787. | Transportation > Transportation Navigation & Tracking Systems from AllBusiness.com
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I know there are a lot of photos, but this one is a little clearer and sharper.
http://extras.mnginteractive.com/liv...RASH_GRAPH.pdf
http://extras.mnginteractive.com/liv...RASH_GRAPH.pdf
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USA Today: Denver crash baffles aviation experts
Denver crash baffles aviation experts - USATODAY.com
Not much in this article that hasn't already been stated. However this comment in particular jumped out at me:
"Interviews by the NTSB shed new light on actions by Continental employees in the hectic moments after the impact. One off-duty pilot who was flying on the jet went inside the burning wreckage three times to help passengers escape, [Robert] Sumwalt [a member of the National Transportation Safety Board (NTSB)] said."
Truly outstanding!
Not much in this article that hasn't already been stated. However this comment in particular jumped out at me:
"Interviews by the NTSB shed new light on actions by Continental employees in the hectic moments after the impact. One off-duty pilot who was flying on the jet went inside the burning wreckage three times to help passengers escape, [Robert] Sumwalt [a member of the National Transportation Safety Board (NTSB)] said."
Truly outstanding!
Regarding this incident and the AF A330 crash
Thank God for the work done by NASA et al. in order to keep the fire away from the interior, also for the evacuation criteria it has already saved many lives---I can't wait until the final report on this!
YouTube - boeing 720 crash test
PA
Thank God for the work done by NASA et al. in order to keep the fire away from the interior, also for the evacuation criteria it has already saved many lives---I can't wait until the final report on this!
YouTube - boeing 720 crash test
PA