takata;
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).
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.
- 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?)
The A330 does not have a fuel dump system. The A340 does.
- What would have been the odds for the RAT to supply power and to restart engines, considering the heavy rain possible at lower alt?
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:
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
- What would be the risk of loss of control when restarting engines?
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.
- In the paper about engine icing, they mentioned that engines would not restart above 10,000 ft, have you got an explanation for that?
Would the referenced quote from the paper (pg.2) be:
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.