Acceleration in this context is physics / engineering speak for the forces on impact.

In layman's terms: It hit the water going pretty much straight down in normal flight attitude.

That does not preclude horizontal or rotational components on impact, but the deformation pattern led BEA to say: If significant distortions in other planes were apparent, I expect BEA would have noted that in the preliminary.

Jeff, EMIT,

Without intending to do so, I may have hyperfocused my disagreement with BEA terminology. In and of itself, the phrase en ligne de vol is reasonably benign. To take issue with it involves a very strict 'raison d'etre'. It may be a non charged description of horizontal for whomever wrote the piece. The writer isn't responsible, the group who approved the text is. As Surplus1 so eloquently points out, this report is composed by parties who have well defined and difficult to disguise interests in the ultimate understanding of the piece by all who read it. As such, it is a rehash of all the information already known, exclusion of information that would lay responsibility on an interested party, and is essentially useless.

Without substantiating a conclusion of hull integrity, they claim it by 'visual inspection'. No supporting engineering, no metallurgy, no independent or reviewed analysis. They rely solely on their authority to conclude to do so. This report is opportunistically political.

To those who would rely on ACARS as if it was some stand in device for FDR, the reality is far from relational. It is the poor passengers who have the most important evidence for a sincere path to the truth and consequent aeronautical progress.


Some here have already concluded ice was the procuring cause of upset.
Possible. So is a pneumatic anomaly vis a vis statics due to turbulence, or even within-the-envelope control excursions. Not to mention an upset already in progress.

The temptation for any lay theory is to base it perhaps solely on what you know best. Currents, Wx, AB systems, AF, etc. etc. I have no specific field other than 40 years of flying. Weather is my worst fear, followed by IMC vs. visual, followed a long way behind by airframe and powerplant issues.

It is worth noting that this thread is backwards. Starting with fussy even arcane and overly technical "evaluation" of what amounts to almost no evidence, I'm stuck where I was on day 1. A modern, well built, and state of the art wide body disappeared suddenly when all indications were that she was just fine. The best place to start is with what is known. A history of unreliable a/s followed by less than dependable computer track, followed by a thus far successful (albeit problematic) incident recovery. With the weather in the area of travel, and some mx tx, one would assume at the outset an upset or similar incident followed by this time an unsuccessful recovery.

"Wait for the Report".......... Why ?

Will

ligne de vol, acceleration verticale
 

Like you, I was puzzled by the fact that, in contrast with the rest of the report, that last bullet of the Findings is so poorly worded. Was it hastily re-edited at the last minute? I guess it was probably meant to say something like:

- based on that fact, and on visual examination of various elements, it would appear that the airplane was not destroyed in flight, that it was essentially aligned with its flight path at impact, and that impact forces resulted in high values of acceleration along the airplane’s vertical axis.


I researched Wikipedia for "en ligne de vol" and got 4 rsults, including the BEA Interim Report. The best I can make of those results is "flight attitude" or "aligned with flight path"



HN39

Because no evidence of fire was found?

Is it at all possible that the aircraft in question could have had a catastrophic encounter with hail at altitude- possibly taking out the pitots, angle of attack indicators and maybe even compromising the windshields and causing a rapid decompression, thus incapacitating the cockpit crew?

Engine icing
 

@ PJ2, Hi,

Is it possible to ask you if you could compute how far could have glided F-GZCP following a double engine failure due to icing @ FL350 or close (~260 kts /210t), as you already suggested a long time ago (I took this very good point from you :)), including a near 180 deg turn with max energy conservation? (I guess, at this point, the turn radius would have been much less important than the amount of altitude/speed wasted).

- Would it be possible for her to dump fuel if necessary after EMER ELEC? (keeping enough to restart engines and reach F. Noronha or Brazilian coast?)
- What would have been the odds for the RAT to supply power and to restart engines, considering the heavy rain possible at lower alt?
- What would be the risk of loss of control when restarting engines?
- In the paper about engine icing, they mentioned that engines would not restart above 10,000 ft, have you got an explanation for that?

Thanks in advance (and nothing urgent to answer, just some thought)
S~
Olivier

Focus people
 

Why do people make a habit of starting with "I'm not trying to be contentious" or "I don't know anything but..." and then go on to lay out meaningless theories and hypotheses which they then reverse in later posts? If you don't know, don't guess - just try asking instead.

24V

The VS L.E. paint condition rules out a mayor hail event.

Although this exercise has been enlightening.....
 

we are no closer to an answer than we were in early June. :(

Evidence retrieved is inconclusive, searches have been terminated for the most part, and the pingers are likely dead or too weak to be heard. Barring a miracle, no further physical evidence will be found (and this crash will remain a mystery).

what is the missing link ?
 

the aircraft entered into a mesoscale Cb, it may have encountered moderate turbulences (AMDAR), ~02:10Z at the time when it may have experienced very low temperatures (from known last pos./traj. and satellite IR imagery), sudden cascade of fault reports, corrupted airspeeds, loss of flight assistances/ALTN 2, possible multiple stall alerts resulting from largely underestimated airspeeds due to Pitot freezing (from past cases like Air Caraïbe, not an established fact), QRH/procedures implementation, crew intructed to react to stall alerts (because based on the AoA not airspeed), pich & thrust and manual flight, possible reset attempt of PRIM/SEC (crew still struggling with their avionics around 02:13Z ? not an established fact, one of the 2 possibilities).
believing in an imminent stall as requested by the procedure (taking the opposite choise than the one made by the Air Caraibe Cpt), what would be the appropriate action then ?
pich down or/and augment thrust, trade altitude for speed ? Would the most probable outcome of such an action be an overspeed ?
If yes, between a high altitude overspeed and an aircraft falling nearly like a stone on the surface with a slightly positive pich (damages on the VS) or on its belly (as described by the BEA, but still "in line of flight", suggesting with the suitable attitude to fly), what could be the missing link/event ?
-could a high speed mach buffet resulting from the overspeed (wrong reaction to a stall alert) explain a stall initiation ? (with a rear CG at >35 % of RC). Are there such things like a stall with a positive pich ? (nose up/tail down). Could the reversed air stream have flamed out the engine or tore the spoilers/ailerons away from the wings ? could it result in a near vertical fall with very little residual lift ?
-or could an attempt to stabilize the altitude (ressource) in overspeed have generated excessive load factors (positive Gs) or aerodynamical stresses, in particular on the control surfaces like the ailerons ? could the loss of control/stall have originated from their failure ?
-or could a severe ice ingestion have flamed out the engines, making the AF 447 at best a glider without airspeeds and visibility in a tropical Cb. wouldn't this suppose a significant horizontal speed at the impact with the surface (compatible with BEA findings on debris, on the Galley G2 ?)
-or could a severe updraft or windsheer have driven the plane out of its flight enveloppe like the Russian plane ? (worsenned by the FMGEC/windsheer prot. impaired ?) doesn't this option render the Pitot freezing event as incidental ?
Jeff

For clarification, Astramike's description of a flat spin is lifted word for word from;

DC-8 Mishap on 12 Dec 1996 N827AX -Stall Recovery in Mountainous Terrain

Flat spins start from normal spins as the spin develops. For a flat spin to develop from a normal spin you need a propellor blown elevator, (which we don't have on 447), and/or aft cg, (which we do). If the cg is aft enough the aircraft is perfectly content to stay in the flat spin all the way down. Inertia keeps the airplane in the spin. The tail section is not sized, nor configured, (rudder area below the HS), to recover A330's from flat spins. Engine departure will move the cg further aft, which is good for flat spins.

Note; Excuse my somewhat, what can be construed as, contrite responses, but I'm not one for words - try to say much in as few words as possible so as not to take up my, and my audience's, time. No intention of being condescending, respect the ones that deserve it, especially the pilots. Y'all are tops at what you do. Just trying to fill-in in places.

Comms...
 

Hi,
Very good point, added to:
1. After landing in Brazil, May 31st, F-GZCP had radio issues: RMP1 had failed. The mech switched the panels with RMP3 which was left INOP for her return leg.
2. In case of double-engine failure, followed by EMER ELEC, only VHF1-HF1 would be available... via RMP1, if working?
3. The fairly bad weather around her in all directions, considering she would have to fly lower, may by itself account for a major issue when using comms.

Will
 

Do you believe weather brought this jet down, of that you fear that it might have?

Thus far, there has been no reported evidence of a fire on the aircraft... no residue on the wreckage or the victims. Nothing should be off the table as yet, but so far, nothing has been found to indicate a fire.

takata;
I believe I had earlier posited that the engines would have flamed out in a deep stall due to extreme angles of attack, not as a result of ice (as per the paper you kindly referenced), but as possibilities are being explored I can provide the following:

With the assumed loss of airspeed reference and assuming the "glide" scenario, the crew would be faced with selecting a speed at which to descend. This selection would be based upon whether an engine re-light was the strategy or if such an option were precluded, a glide and ditching. The speed and descent strategies are substantially different but the zero-wind distance covered is about the same.

For an engine relight, the optimum speed is 300kts, the pitch attitude for 210k kg 0.5ND; the QRH indicates that using this strategy, the aircraft would take about 15 minutes to descend from FL400 to ground and travel approximately 100nm

If the strategy is to glide with the intention of ditching, the optimum speed would be "green dot", which would roughly be, (for 210T) at 350, 238kts.

For this strategy, an average descent rate of about 1300fpm is indicated. Assuming a steady descent rate from, say, FL300 (5000ft lost in sorting things out), the time to touchdown would be 23 minutes and distance covered at about 4nm/minute would be just under 100nm.

In any turn, it obviously requires more lift to both glide and to provide energy for the turn, (slightly higher 'g'), so some loss of forward distance even without an increase in rate of descent, would occur. A reasonable estimate would be 5, possibly 10nm - it wouldn't be zero, and it wouldnt' be 20nm.

All these calculations are obviously based upon timely, correct assessment and handling with regard to the QRH numbers, and as such are "best cases"; any compromises or less than optimal performance obviously reduces distance covered and time to contact.
The A330 does not have a fuel dump system. The A340 does.The RAT does not "supply power" to start engines at any time. It is a hydraulic pump of minimal capacity with a two-bladed propeller mounted in the #4 flap-track canoe on the right wing. It will only supply hydraulic power to the emergency electrical generator, which may be what you're referencing? :) Engine start is possible using bleed air from the APU but, as seen below, the APU is not started until reaching FL250 in the descent.

I know of some comments that indicated that the APU will start well above this altitude but there are only so many attempts in the batteries...

I wouldn't expect "heavy rain" to play a role in any starting difficulty (due to certification tests and absence of cautions for same in either the Engine Relight QRH checklist or the All Engine Flameout - Fuel Remaining QRH drill)

For the awareness of all, here is part of an example of an "All Engine Flameout - Fuel Remaining" QRH checklist:

Quote:

---

RAT ......................................................MAN ON

– ENG START SEL.....................................IGN
– THRUST LEVERS................................... IDLE
– OPTIMUM RELIGHT SPD ......................... 300/.82

Increase speed during descent toward 300 knots. Do not exceed MMO
At 300 knots/.82 with all engines stopped it takes about 15 minutes to descend from FL400 to the ground. The distance is about 100 NM.

In case of a speed indication failure (volcanic ash): Pitch attitude for optimum relight speed is (list of optimal pitch attitudes)

– LANDING STRATEGY................................DETERMINE
Determine whether a runway can be reached or the most appropriate place for a forced landing/ditching.
– EMER ELEC PWR (If not automatically coupled) ..............MAN ON
– VHF1 ............................................................ .........USE
– ATC ............................................................ ...........NOTIFY
IF NO RELIGHT AFTER 30 SEC :
– ENG MASTERS..................................................... .... OFF 30S/ON
Unassisted start attempts can be repeated until successful, or until APU BLEED is available.
IF UNSUCCESSFUL :
– CREW OXY MASKS (above FL 100)................................ON
WHEN BELOW FL 250 :
– APU (if operative).................................................. ... START
WHEN BELOW FL 200 :
– WING ANTI ICE .........................................................OFF
– APU BLEED....................................................... .........ON
IN SEQUENCE
– ENG MASTERS (one at a time)..................................... OFF 30S/ON
When APU bleed is available or if engine restart is definitively considered impossible :

– OPTIMUM SPEED..............................................REFER TO TABLE BELOW

---

It is not possible to determine the capabilities and level of discipline brought to bear by any one crew upon such circumstances. There is no inherent potential for "loss of control" in the drill nor in the relight of the engines, but flight conditions, further aircraft degradation, many possible sources of distraction would all have to be considered.
Would the referenced quote from the paper (pg.2) be:

Quote:

---

The engine speed decay was also associated with an increase of Turbine Gas Temperature (TGT) and a failure of the engine to respond to the pilot commanded thrust level, thereby, receiving the name “rollback”. Engines that were shut down from the sub-idle operating condition could be restarted at an altitude of about 10,000 feet Those engines not shut down recovered to normal operation at about the same altitude.

---

The reference here is to smaller high-bypass engines in Commuter aircraft. The A330 QRH specifies the altitudes and speeds under which both air-start and assisted starts may be expected to succeed given all other factors being equal. I am familiar with the phenomenon of icing accretion on the backs of compressor blades, notably the N1 in large, high-bypass engines such as are on the A330 and in fact we were using a procedure to address "roll-back" at one point, possibly for other (bleed) issues.

In short, I have no explanation at all for the paper's statements partly because it references commuter aircraft but also because there is no mention of this in the QRH which would advise the crew to act or execute the drills differently, (by not expecting an engine start above 10,000ft, etc).

Hope this helps, takata. While I disagree for a number of reasons with the "glide" thesis we cannot discount it.

It has been pointed out earlier that engineers using this phrase in this way means 'deceleration' i.e. force (=ma)

due to impact at high speed.

It does not mean the acceleration was 'accelerating' :=

PJ2
 

I am not saying that all do, but our one's have. I have had the privilege of watching the system used in anger!

Ref post 3193 {surplus 1}, this uses a similar ‘backwards’ deduction path as AstraMike {post 3179}, and then invokes some structural failure to maintain the spin. I haven’t seen any reference or evidence of structural failure, so how is this line of thought justified?

Returning to previous posts on the rudder limiter (maximum rudder deflection). The limit angle is a function of CAS and is computed by the SECs (A330 controls description). With a double SEC failure, the system freezes at the limit value. This condition may have been induced by the ADC faults / shutdown, but in the process of ‘failing’ due to parameter comparison, the ADC may have registered quite a low value of CAS. IIRC the comparator trips with a discrepancy greater than 60kts IAS. Thus, if the IAS value was low, then the rudder limiter may have frozen at quite a large angle; … perhaps a point for future reference.

Litebulbs;
You know, somewhere I recall someone saying that before, so thank you for reminding me. Ours didn't and I thought it was the design itself.

takata;

If the AF447 A330 had a fuel dump system, given the kinds of equipment powered (necessary for safe flight only), on the emergency electrical generator or the batteries, I would expect that no fuel dump capability would remain. Fuel dump is simply to reduce landing weight, but these aircraft are usually certified to land at MTOWs so fuel dump would not be an "emergency" item required for safe flight.

Sorry for misleading you and thanks to litebulbs.

takata #3209, re engine icing / relighting. It’s not clear which engine type or ‘report’ you are referring too.
The initial section (Mason, Strapp, & Chow) reports on a medium sized regional aircraft suffering ‘rollback’. For this aircraft / engine combination, some engines did not relight easily as the severe ice accumulation took some time to clear; also, the relight envelope was below FL200. In some instances the subsequent stages of the compressor were damaged and engine did not relight at all, or ran sub-standard.
For the large commercial transport engines, the report indicates that initial ice accumulation did not generate engine problems, but the relatively smaller amount of ice passing through the compressor as the ice melted did, i.e. a problem when exiting the conditions. In general, the effects were mild and although the report describes the instances of shutdowns as ‘failure’, it qualifies this in that all engines were restarted, even when damaged.
Thus, the ice and engine failure scenario is unlikely.