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Old 14th June 2012 | 08:47
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HazelNuts39
 
Joined: Jul 2009
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From: France - mostly
Originally Posted by OK465
You are correct that the CAS (which BTW is referred to in the report as "calculated airspeed' not calibrated nor IAS, the term you use) is actually recovered at 2:10:34 at 223 knots.
If you allow me to 'split hairs' on terminology: The airspeed indicated on the display (corrected for instrument error, if any) is commonly referred to as IAS. If the ADIRU applies appropriate corrections for errors in pitot and static pressures, IAS is equal to CAS. If the pitots are blocked or at large AoA the indicated airspeed is not equal to CAS. The report refers to the captain's IAS as 'Vitesse conventionelle' or 'calculated airspeed' or 'CAS' when it means IAS.

Regarding the ACARS messages FLAG ON CAPT(F/O) PFD SPD LIM, BEA#1 says: "This message indicates the unavailability of the FMGEC's characteristic speed calculation function." There is no reference for Takata's assertion that it would be latched. IMO it could well be a temporary condition similar to the unavailability of the FD's - the SPD flag that occurs later is not latched (see IR#3 page 44). When the FD's return at 02:10:47, the F/O's airpeed (ISIS) is still 121 kt. The stall warning speed of 207 kt would have been off-scale on the F/O's PFD.

Last edited by HazelNuts39; 14th June 2012 at 09:41.
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