Atlas Air 767 down/Texas
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Actually the CAB accident report said that the negative acceleration increased to a mean value of about - 2.8 g so the peak before the aircraft broke up may have been even higher.
https://en.wikisource.org/w/index.ph...705.pdf&page=4
Here are FDR plots from NW705 as published in the CAB report:
Looking at the plots, maybe the -2.8 g number came from the average of the last two data points on the coarse foil technology FDR record.
https://en.wikisource.org/w/index.ph...705.pdf&page=4
Here are FDR plots from NW705 as published in the CAB report:
Looking at the plots, maybe the -2.8 g number came from the average of the last two data points on the coarse foil technology FDR record.
Their indicated airspeed to reach those negative G values were in excess of 400 knots. Not possible to get anywhere near those numbers at 210 to 230 knots. The first generation jets were also stronger and had higher VNE limits. We regularly cruised the 727 at 380 knots IAS at 16,000 feet on shuttle flights. VNE was 405. The A330 has a VNE around 330 knots and the 767 about 355.
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From the NTSB Investigative Update on March 12, 2019:
FDR, radar, and ADS-B data indicated that the airplane entered a rapid descent on a heading of 270°, reaching an airspeed of about 430 knots.
https://www.ntsb.gov/investigations/Pages/DCA19MA086.aspx
From the NTSB Investigative Update on March 12, 2019:
https://www.ntsb.gov/investigations/Pages/DCA19MA086.aspx
https://www.ntsb.gov/investigations/Pages/DCA19MA086.aspx
In the trace of the 720 accident you can see that at 220kts it produced ~ -2g, increasing to -2.8g @ ~280kts. The 720 had a ~20 - 25% lower wing loading than the 767, so should be able to produce ~25 - 30% more g at the same speed (especially in negative direction where no flaps/slats and tricked- out profiles will help).
When we extrapolate this data from the 720 accident we still end up with something around -2 to -2.5g maximum. We'll see the exact figures once the traces are published.
But I would expect something around -2g and +4 - 4.5g as maximum values.
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It looks to me like the Atlas 767 must have been very light to climb to FL400 immediately over the Gulf of Mexico.
Freighters continue to crash at a significantly higher rate than passenger planes at U.S. carriers as we have often observed here over the years.
There are a lot of B-763's still flying, I would think that if there was an early indication of a mechanical failure in this Atlas mishap, the NTSB would say something by now.
Last edited by Airbubba; 27th Mar 2019 at 00:47.
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Most references show "flaps out of up" (although I do have one reference which says flaps >1).
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One of you may be right, I'm not so sure that wing loading at max gross weight is what determines the negative g capability of an airliner. The -4 g claim may indeed be from a typo in a forum posting.
It looks to me like the Atlas 767 must have been very light to climb to FL400 immediately over the Gulf of Mexico.
Freighters continue to crash at a significantly higher rate than passenger planes at U.S. carriers as we have often observed here over the years.
There are a lot of B-763's still flying, I would think that if there was an early indication of a mechanical failure in this Atlas mishap, the NTSB would say something by now.
It looks to me like the Atlas 767 must have been very light to climb to FL400 immediately over the Gulf of Mexico.
Freighters continue to crash at a significantly higher rate than passenger planes at U.S. carriers as we have often observed here over the years.
There are a lot of B-763's still flying, I would think that if there was an early indication of a mechanical failure in this Atlas mishap, the NTSB would say something by now.
Yep, cargo drivers are forced to work longer and harder than the pax ones cause the FAA had the guts to treat cargo pilots as less "precious" . Absolutely astounding that they were allowed to differentiate....
And Amazon trying to push its shipping cost down by "operating" cargo ac from cheap labor holdings will just raise the chance for another crash with a loaded cargo plane full with dangerous goods, into a densely populated area.......corporate American greed has taken air safety hostage, Boeing, FAA, cheap cargo operators etc
Sometimes wondered when rolling down rwy 09 MIA, on our B747-4 cargo fully loaded with dangerous goods, and downtown MIA just beyond the rwy.....
Granted, this is a 767.
Is there a possible link to FLCH (or similar feature in 767), or, was this flight not close enough to IAH for that feature to be a contributing factor?
Reference article and discussion
There are two FSCU - Left and Right. Not sure about other systems, but the engines use left to left and right to right - so an FSCU failure only effects one engine.
IMHO the inadvertent TOGA selection is feasible, but this all remains conjecture until the NTSB releases something official.
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The Flap/Slat Control Units on the 767 are relatively crude by current standards (not surprising - the basic design being nearly 40 years old). They put out analog discretes for 'flaps not stowed' - true anytime the flaps are not fully 'up', and 'flaps in landing' - true when flaps are ~23 degrees or greater (there may well be others - those are the ones that get used by the propulsion systems) - as well as digital outputs for use by systems such as EICAS.
Regarding your comment...
If anyone cares, on the engine side 'flaps not stowed' turns on continuous ignition.
There are also some lesser-known microswitches on the flap lever itself (at 1 unit) which input into the Thrust Management Computer and Flight Control Computers.
These switches are actuated in the flaps 1 detent position.
When actuated, the thrust management computer estimates the slats
moving to the flaps 1 position linearly in 5 seconds.
When actuated, the thrust management computer estimates the slats
moving to the flaps 1 position linearly in 5 seconds.
The thrust limit mode transitions to GA when:
1) TO/GA is pressed on the TMSP (i.e. MCP) in the air
2) In air and the thrust limit mode is not in TO and the FCC signals GS Capture.
3) In the air and the thrust limit mode is not in T/O and flaps transition from zero to one.
The thrust limit mode will be locked in GA for flaps greater than 23.
1) TO/GA is pressed on the TMSP (i.e. MCP) in the air
2) In air and the thrust limit mode is not in TO and the FCC signals GS Capture.
3) In the air and the thrust limit mode is not in T/O and flaps transition from zero to one.
The thrust limit mode will be locked in GA for flaps greater than 23.
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I would imagine the conflagration from a fully fuelled B747 would overwhelm most dangerous goods being carried.
Last edited by Lord Farringdon; 29th Mar 2019 at 08:54. Reason: Correct quote attribution
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My sincere apologies tdtracer. I have re-edited my post to correct the attribution. I was a bit tired at the time and obviously screwed that up deluxe!
Last edited by Lord Farringdon; 29th Mar 2019 at 08:57. Reason: spelling