Latest on AF Airbus crash

[Mike]

Some interesting new answers to the accident. Interesting point that supports those of us who always carried "enough" fuel, this flight had no extra fuel onboard, forcing them to fly the flight planned route as opposed to other aircraft that night that diverted around the weather. These pilots had full tanks so there was no choice, which makes for a very uncomfortable position to be in. We've probably all been there with marginal fuel, and it's a bit like starting off with one strike already against you. It certainly puts you in the mindframe where you are willing to make the decision to divert earlier than you normally would. It certainly did for me.
The other comment about experience (I wasn't aware they had evidence that the captain was not on duty at the time) re. the third pilot in the left seat adds to the sorry situation. The NW pilot that had experienced an almost exactly similar situation except in the daylight was able to fall back on experience by turning everything off and setting the throttles at a 'normal' cruise setting, then ignoring the pitot-static instruments and merely flying more or less level by looking out the window.
Like the discussion in the previous posts, this was/is a very tough scenario to face, one quite possibly without a realistic solution. Even with 20-20 hindsight, I would find it very difficult to fault the crew actions (said with no airbus qualifications).

Death in the Atlantic: The Last Four Minutes of Air France Flight 447 - SPIEGEL ONLINE - News - International

 

[Garry]

Mike,
Thanks for the update. That just proves that one of the biggest problems with completely computerized or electronic systems for flying is that these devices can go bad. A friend of mine's brother was killed in a civilian turboprop in a storm when unexpected ice conditions appeared. The last transmission to the tower was that his flight instruments (electronic monitors/screens) had failed. The irony is that he had a vaccum operated altimeter,rate of climb indicator, a compass, and a flight level and one other instrument that helps a pilot calculate airspeed( I am not a pilot, but some of you will know what I mean) but he was not trained on its use or was 'rusty' in the application. My father flew in WWII and he would have been very surprised to hear that a pilot cannot maintain level flight on a compass heading without the aid of a computer.
Garry

 

[David Morton]

I am really amazed that Air France used 'Refiling' -the habit of inserting a destination nearer than the final destination in the FMCS. I really thought that this habit
was stamped out in the early 90's and though I did it frequently in the 70's and 80's,
I eventually formed the opinion it should be outlawed. What a sorry state of affairs - though no accident is rarely attributable to one small thing but a whole catalogue of errors.

 

[Trevor Booth]

A free falling body under gravity falls at the rate of 9.81 m/s/s. From 11000 m and assuming the aircraft stalled at Zero knots say
The aircraft would hit the water with a velocity of approx 464 m/s in ~50 secs.
This does not allow for any wind resistance or the aircraft "gliding" which would lead to a terminal velocity after which no more acceleration would occur. I have no idea of the terminal velocity of a free falling aircraft, however if the wind resistance was ~ 25% then it would fall at ~7 m/s/s and hit the deck at close on 758 knots and still less than a minute. Any wonder it was shreded into small bits.

 

[Mike]

Not sure I understand the description of the stall, fall and impact. The report suggests it took 4 minutes to descend through 7000', and states (I think) the aircraft was 5 degrees nose up, suggesting something like a flat spin. It also talks about a descent speed of 90+ mph (about 130 ft/sec) and no forward velocity, a parachutist free fall rate (I believe that's arms out and 'flying' - I think you can get to 120+mph if you put your head down, arms out in a 'dive', but I've never stepped out of a jet on purpose). I don't see how this would "shred bone", or produce >35 longitudinal g's (no forward velocity, right?) enough to break the vertical fin/rudder.
We lost an F-15 a few years ago, when the nose section broke off just ahead of the intakes. The airplane minus the nose section floated down vertically and landed in one piece in a field. It still looked like an airplane, complete with both tail fins.
Can't make sense of it. Maybe I'm missing something in the reading.

 

[David Morton]

Trevor,
This aeroplane would have stalled long before 'zero' knots and I would hazard a guess his height and weight would have been a contributing factor. I would anticipate a 'clean' stall speed at that weight to be approx 140 knots. (KIAS)
My experience from free fall was I took one minute from 12000 feet to 2000 feet
which comes out around 120 (mph equating to 190 km) vertical speed. If I jumped from 30,000 feet (SAS do just that) then it would be about 2 mins 40secs to 2000 ft. (but they, the SAS, also pull a lot lower). 9.81 m/s/s is not a falling rate but an acceleration rate and has a few assumptions that don't really relate to this aeroplane which may or may not have still been under power. The speed at which it descended could not be calculated with any degree of accuracy so again a bit pointless.
Hitting water is akin to hitting a brick wall. The Nimrod that came to grief in Lake Ontario was in a thousand pieces and he only descended from only about 1500 feet with
approximately 20 degrees nose down and under power, trying desperately to unstall the aeroplane.
http://www.youtube.com/watch?v=m2BSfgnCU2Q

For the moment, any conjecture is futile and let's hope the ADR and CVR (recorders) are eventually recovered.
Also have a look at what is referred to 'Coffin Corner' http://en.wikipedia.org/wiki/Coffin_corner_(aviation)
as it does explain quite a lot as well. Most jets can easily be flown into this problem and in an area of sudden icing and high turbulence , any crew trying to get 'over' bad weather instead of routing around (sometimes up to a 120 mile detour when crossing the ITCZ)
Intertropical Convergence Zone - Wikipedia, the free encyclopedia
are almost instantly thrown into coffin corner territory. This can be especially so when flying on tight fuel limits and refiling destinations. If he started deviating like that he would probably have to refile again using Lisbon as the new destination and Toulouse or Bordeaux as the alternate though that might have been the best option.

 

[Trevor Booth]

David,
the zero knots I was referring to is not KIAS, I meant relative to ground vertically, the aircraft would still have some forward speed at stall , but I assumed zero vertical speed when it stalled.

The aircraft would accelerate vertically until it reached terminal velocity after which point it would descend at that velocity with no further acceleration. , the rate at which it falls until terminal velocity is governed by wind resistance. At 35000 ft (11000 m) there would be little wind resistance and it is likely that it commenced to fall at 9.81m/s/s and as the atmosphere got thicker it would in fact slow down in terms of acceleration until terminal velocity.

The human body in horizontal attitude has a terminal velocity of ~ 125 MPH , your free fall fits this.

The attitude of the aircraft as it fell would dictate the rate at which it accelerated until terminal velocity

It is all purely conjecture and it was not my intention to do otherwise, however, if the one minute free fall time from 35000 feet is correct it descended at a horrific rate of knots.
lets hope they find the recorders or in the least the ADR,

 

[Mike]

Trevor, where are you getting the one minute freefall time? I went back and reread "minute 3:freefall". It seems that Mr. Arnoux's model of the accident showed some 4 minutes to impact based on automatic error reports that were datalinked back, at a vertical velocity of 42m/sec., in a 5 degree nose up attitude. That 4 minute or so time frame is backed up by another published report of the datalink info with time ticks beside them. That report showed the time lines from the first transmitted problem (autopilot disconnect, I think?) to the last signal when the datalink quit or was no longer received.
I guess we'll never know for sure. Maybe they'll find the black boxes and get a little more info, but I doubt it (2000+' of water with no beacon signal?).

 

[Trevor Booth]

Mike,
the way I read it is that it started to free fall at minute 3. (minute 2 loss of control)

Arnoux maths dont work

If he said impact at 91m/s not 95mph it would make more sense.

What he proposes - that the aircraft fell from 11000 m and hit the deck at 95 MPH !!!

It must have had considerable forward motion to cause the human body to be ripped in half by the lap belt and at 95 MPH that is unlikley to happen , 91 m/s different story.

I would suggest that airbus has already done some CFD analysis and they are not reporting correctly.

 

[Ron Earp]

It is a shame in this day and age we were not able to recover those data recorders. Anyone know if the data recorders have inflatable devices on them? I would have thought that in addition to the signal generators they would have flotation devices that would bring them up to the surface.

 

[Jon Briggs]

It is a shame in this day and age we were not able to recover those data recorders. Anyone know if the data recorders have inflatable devices on them? I would have thought that in addition to the signal generators they would have flotation devices that would bring them up to the surface.

They don't have flotation devices attached to them, they are secured in the tail of the aircraft and are probably still there. Also the signal generators will have stopped working months ago, I not holding out much hope of them being found.

 

[Ron Earp]

They don't have flotation devices attached to them, they are secured in the tail of the aircraft and are probably still there. Also the signal generators will have stopped working months ago, I not holding out much hope of them being found.

Yeah, I knew the location generators ceased shortly after the crash. As I recall a few weeks was the max time they thought they would function. You'd think the designers would have thought that floatation devices of some type would be useful if they had extensive safeguards to not deploy except when immeresed in water.

 

[Price Walton]

I'm not sure the maths are that far off, but I'm not convinced that Rene Arnoux wasn't behind some of the conclusions....:laugh: