US investigators have determined that an American Airlines Airbus A321 landed short of the runway and suffered a tail-strike after encountering a microburst on approach to Charlotte-Douglas airport.
But the National Transportation Safety Board points out that the crew had not adopted the airline’s guidance on approach speed and aircraft configuration when faced with windshear risk.
The A321 (N564UW) had been conducting an ILS approach to runway 36L after arriving from Atlanta on 15 August 2015.
Investigators state that the crew acknowledged a low-level windshear advisory for the approach and the pilots had discussed rain showers visible over the airport.
As the aircraft descended through 2,500ft the captain – who was flying – disengaged the autopilot and, some 30s later, asked for the flaps to be set in the full configuration.
The inquiry says the crew was advised of a windshear alert with a 20kt loss of airspeed at 1nm final, and that other aircraft had reported 8-15kt airspeed gains at 300ft.
But it states that the captain “did not reference” the quick-reference handbook which, under these windshear conditions, identifies precautions including selection of the longest suitable runway, increasing the approach speed by 15kt above reference, and using a ‘flap 3’ configuration, one stage below full.
The crew did not increase the approach speed, maintaining 140-145kt in the minute before the accident. About 7s before the touchdown, the airspeed started to fall and it dropped below groundspeed while groundspeed began to rise.
Wind information showed a 10kt headwind that increased to 15kt, before switching by 180° to a 15kt tailwind just as the airspeed began to fall. This tailwind persisted for about 7s before turning back to a headwind.
As a result, the aircraft lost lift. The first officer told the inquiry that the aircraft “fell like a brick”.
Just before the touchdown, the crew received an aural windshear warning and the captain immediately called for a go-around, but the aircraft struck the ground about 3s after the alarm.
It landed short of the runway, although in the paved displaced threshold area, with a 2.6g impact, hitting several runway lights and suffering a tail-strike which damaged a 20ft section of the aft fuselage. The aircraft became airborne during the go-around and was subsequently vectored for a landing on runway 36C.
None of the 159 occupants was injured.
NTSB investigators, who released their findings on 8 June, state that the decision by the captain to continue the approach without applying the configuration and airspeed precautions in the quick-reference handbook contributed to the accident. The first officer told the inquiry that the crew did not refer to the handbook “because there were no thunderstorms or convective activity in the area”.