Portuguese investigators have detailed a hard landing incident two months ago in which a SATA Airbus A320 touched down heavily in the Azores, bounced, and then hit the runway with even greater force.
Despite the aircraft's suffering damage in the 4 August incident, it flew another six sectors before a more detailed examination was conducted.
SATA had only just taken delivery of the brand-new A320, CS-TKO, owned by US lessor International Lease Finance (ILFC).
The aircraft, arriving from Lisbon, had conducted a stable approach to runway 30 at the Azores' Ponta Delgada Airport but the initial impact, which registered 2.13g, caused the jet to lift again to a height of 12ft (3.65m).
At this point the aircraft's throttle levers had been in the 'climb' position but, during the bounce, the throttle was retarded to 'idle'. The A320's spoilers started to deploy, interrupting the lift and the aircraft descended again, hitting the runway with an impact of 4.86g.
Portugal's air accident investigation agency, GPIAA, points out that the aircraft's configuration at the first touchdown left the spoilers retracted - enabling it to become airborne more easily - and that the subsequent thrust reduction allowed the "inappropriate" secondary deployment of spoilers.
The GPIAA states that spoiler deployment can aid stability in the event of a small bounce, but that Airbus procedures for a heavy bounce require the crew to initiate a go-around rather than attempt to rescue the landing.
While the captain brought the incident to the attention of technicians in the Azores, a visual inspection of the landing-gear "did not detect any abnormality", says the GPIAA. It adds that load data retrieved from the aircraft were difficult to interpret.
Although a suspected hard landing was recorded in technical logs, the aircraft was cleared to operate back to Lisbon, where the captain again sought assistance to interpret the load data.
Six flights were carried out before the aircraft underwent a closer inspection, which revealed damage to main landing-gear structures and the aircraft's tyres.
None of the 166 passengers and seven crew members was injured during the incident. The GPIAA says the inquiry is continuing.