Actual Airbus Procedure
Now, it's easy to generalize a procedure that is to be applied to all situations of unreliable airspeed that can happen at any time, for any reason (radome, pitots, etc). The 5° remark is only one small bit of the immediate memory items and only applicable IF the safe conduct of the flight is impacted.
Despite 5° not being the perfect pitch for cruise flight at M.82, if the pilots of AF447 had gone to 5° pitch (instead of 15+,or maintained their current pitch attitude), they would have climbed a bit initially, but it would have been an easy recovery back to level flight. Then only a minor pitch correction would be required if/when the stall warning sounded. It probably would not have degraded to the deep stall that it did.
The ACTUAL procedure says (emphasis mine, sorry if the dot leaders don't line up):
If the safe conduct of the flight is impacted:
MEMORY ITEMS:
AP/FD.......................................................... ................... OFF
A/THR......................................................... .................... OFF
PITCH/THRUST:
Below THRUST RED ALT...............................................15° / TOGA
Above THRUST RED ALT and Below FL 100......................................................... ....10° / CLB
Above THRUST RED ALT and Above FL 100......................................................... ......5° / CLB
FLAPS (if CONF 0(1)(2)(3))...................... MAINTAIN CURRENT CONF
FLAPS (if CONF FULL)....................... SELECT CONF 3 AND MAINTAIN
SPEEDBRAKES................................................. ..CHECK RETRACTED
L/G........................................................... ........... UP
When at, or above MSA or Circuit Altitude: Level off for troubleshooting.
** end of memory items **
GPS ALTITUDE.................................................... ......splay on MCDU
To level off for troubleshooting:
AP/FD.......................................................... .......OFF
A/THR......................................................... ........OFF
THEN.... the FCOM provides a chart of pitch and power settings to level off for troubleshooting, and then troubleshooting steps including identifying a bad ADR, and procedures, including pitch and power settings for a landing with unreliable airspeed.
I think what most pilots are surprised to learn is how the stall angle of attack is influenced by Mach number. For the A330, the stall warning coming on at only 4° aoa at M.82 and about 10° aoa at M0.3.
A recovery also has to consider that as speed (Mach) is recovered the stall margin narrows again, and gentle control inputs are required to prevent secondary stall.
So in this case, as they slowed due to the rapid climb, the stall angle of attack was actually increasing along with their actual angle of attack, until about the time that they got to FL380 and they ran out of energy. Then the actual AOA went rapidly through 10° up to 40+, and thing really became incomprehensible to them.