He didn't read the airspeed "just fine." He misread it by more than 15-19 kts ("safely above Vls" vs 15-19 kts below Vls) and didn't process that his speed was barely above the red band which is an image we never see in normal approaches. That is what extreme stress will do to you and is understandable. The NTSB reports covers the stress impact on human performance.
Without the AOA protection AB built into the FBW we can only speculate what would have happened without AOA protection. At a high AOA, reached at 150', he then attempted to raise the nose at 100'. That attempt, with only a couple of knots above stall speed, might have lead to a situation where the vertical descent rate would have been even higher at water entry. That's if he realized it and didn't stall the a/c. If he had stalled a non FBW protected a/c the outcome would have been worse.
From the NTSB report - 2.3.3 -
Despite not reaching this portion of the Engine Dual Failure checklist, the captain stated during postaccident interviews that he thought that he had obtained green dot speed immediately after the bird strike, maintained that speed until the airplane was configured for landing, and, after deploying the flaps, maintained a speed “safely above VLS,” which is the lowest selectable
airspeed providing an appropriate margin to the stall speed. However, FDR data indicated that the airplane was below green dot speed and at VLS or slightly less for most of the descent, and
about 15 to 19 knots below VLS during the last 200 feet.
The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage. (See additional discussion in section 2.7.1.)
During emergency situations, such as the accident event, pilots experience high levels of stress resulting from high workload, time pressure, and noise. Stress can distract pilots from cockpit duties and result in pilot errors or performance degradation.133 For example, stress can lead to a phenomenon known as “tunnel vision,” or the narrowing of attention in which simple things can be overlooked (for example, airspeed and descent rate (snip)
The airplane’s airspeed in the last 150 feet of the descent was low enough to activate the alpha-protection mode of the airplane’s fly-by-wire envelope protection features. The captain progressively pulled aft on the sidestick as the airplane descended below 100 feet, and he pulled the sidestick to its aft stop in the last 50 feet, indicating that he was attempting to raise the airplane nose to flare and soften the touchdown on the water. The A320 alpha-protection mode incorporates features that can attenuate pilot sidestick pitch inputs. Because of these features, the
airplane could not reach the maximum AOA attainable in pitch normal law for the airplane weight and configuration; however, the airplane did provide maximum performance for the weight and configuration at that time.
The Airbus simulation indicated that the captain’s aft sidestick inputs in the last 50 feet of the flight were attenuated, limiting the ANU response of the airplane even though about 3.5° of margin existed between the airplane’s AOA at touchdown (between 13° and 14°) and the maximum AOA for this airplane weight and configuration (17.5°). Airbus’ training curricula does not contain information on the effects of alpha-protection mode features that might affect the airplane’s response to pilot sidestick pitch inputs. The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.
The NTSB concludes that training pilots that sidestick inputs may be attenuated when the airplane is in the alpha-protection mode would provide them with a better understanding of how entering the alpha-protection mode may affect the pitch response of the airplane. The NTSB recommends that the FAA require Airbus operators to expand the AOA-protection envelope limitations ground-school training to inform pilots about alpha-protection mode features while in normal law that can affect the pitch response of the airplane
Last edited by misd-agin; 19th May 2017 at 13:29.
Reason: Word change