xcitation;
No, I wouldn't pick any of those, not because they may or may not apply but because there is no single "cause" and we can't stop at answer a, b, or c yet.
In these discussions about climbing, there is something that has been missed in
airtren's and others' here of "climbing out of warm air", etc etc.
An aircraft on a routing which has been flight planned is not just climbed out of one altitude for another. One needs an ATC clearance to do so, as one needs an ATC clearance to deviate off course. It is not mentioned in the BEA Update that the crew obtained a clearance either to deviate from course or later, to climb out of FL350. You simply don't deviate from your flight planned routing and altitude without an ATC clearance unless it is a dire emergency, which, given all available information including the loss of airspeed information,
this was not an emergency.
This relates to my earlier point about SOPs. While we do not have all the information, the BEA Update does not indicate any standard communications with ATC took place (for the climb), nor does the Update indicate that the crew followed SOPs for an Abnormal or Emergency event. The PF just started the climb, essentially on his own without coordination with the PNF, and the PNF appeared to just follow along. Now this may not be the case at all but it is what the BEA Update either says or leaves out from which we must draw interim notions.
One simply never, ever "launches" into an abnormal or emergency drill on one's own, period. I have discussed this at length elsewhere.
The discussion between the two/three crew members about altitudes and temperatures is pretty ordinary stuff for flight crews and, if I may, I think
airtren and others may be reading far too much into the communication/discussion...they're parsing it far too finely and perhaps looking for justifications of the pitch-up and climb where there are none. I've had such discussions many times and while an operational decision (to climb or not), it isn't unusual, ominous or even significant that they decided not to climb at that moment.
True, the ICAO Flight Plan (available in the Appendices of the First BEA Interim Report and reproduced below), indicates that after NTL the routing was UN873 INTOL/M0.82 @ FL350, then SALPU at which a climb to FL370 was flight planned, with the Mach remaining at M0.82, (see the ICAO Flt Pln below).
Standard procedure is to cross the waypoint at which the higher altitude is planned, AT the higher altitude (vice beginning the climb at the waypoint).
They were relatively heavy (not "too" heavy...the discussion was a recognition that it was a bit too warm to climb even though I suspect they could have...I've done it sometimes, when it's close but still operationally doable because if one doesn't take the higher altitude one may not get it for the balance of the trip - it's as much a judgement call as it is an operational one).
Their clearance at that moment was to maintain FL350 and they would not climb to/maintain FL370 without ATC clearance to do so even if the Flight Plan indicated such - one simply doesn't climb without a clearance unless it is a dire emergency when communication with ATC is not possible in the time available. Again, this was not the case at this point in the flight, (prior to SALPU). That climbing to FL370 was on their minds was obvious but there was nothing unusual in that - it was on the flight plan and they were assessing the need for the climb and, at that point, were content to stay at FL350, with a possible request to climb to FL370 a bit later than flight planned.
My sense of their discussion is, therefore, that it was about managing the flight, not about any concern about altitude and weather or temperature. I think things were "ordinary" in the sense that there was weather around and they were doing what everyone else was likely doing - discussing it, and deviating where necessary and monitoring temperature for their climbs.
PJ2
ICAO Flight Plan from the 1rst BEA Report:
LFPGYEYX SBGLYOYX SBGLAFRK
(FPL-AFR447-IS
-A332/H-SPRIJWYG/SD
-SBGL2200
-N0481F350 DCT AWAKE UZ10 FLIRT/M082F350 UZ10 NTL UN873
INTOL/M082F350 UN873 SALPU/M082F370 UN873 ORARO/M082F370
UN873 ISOKA/N0471F370 UN873 LIMAL/N0466F390 UN873 SAMAR/N0468F380 UN873 BAROK/N0465F400 DCT PORTA UN873 MOKOR UN741 NTS/N0484F280 UN741 KEPER UT182 ROMLO/N0483F270 DCT
-LFPG1034 LFPO
-EET/SBBS0028 SBRE0050 SBAO0302 GOOO0349 GVSC0512 GCCC0606
LIMAL0643 GMMM0731 LPPC0816 LECM0851 LFRR0930 LFFF1004 RIF/ZMR UN976 DGO UL176 SSN UP181 ENSAC SOLSO DIRAX LFBD REG/FGZCP SEL/CPHQ DAT/SV DOF/090531)