A320 severe touchdown went unnoted
Inquiry proposes opting for ACARS after pilots were not alerted to excessive landing load as printer ran out of paper
Kosovan investigators determined that a Greek-registered Airbus A320 continued flying for eight sectors despite exceeding load limits during a severe hard landing at Pristina.
Pilots of the Orange2fly aircraft (SX-ORG) did not believe the landing was abnormal but had not received a printed load report from the data-management unit, because it had not been loaded with paper.
The crew had agreed to conduct a "positive" landing - a deliberate firm touchdown - during the service from Basel on 1 December 2017, in order to reduce the risk of hydroplaning on the wet runway.
Although the aircraft contacted the runway with an impact of 3.04g, above the limits set out in the aircraft maintenance manual, the crew's firm-landing decision meant that, initially, the pilots did not suspect any problem.
"There were no actions taken by the [captain] regarding the landing," says the Kosovan government's Aeronautical Accidents and Incidents Investigation Commission, which released findings at the end of December 2018.
"There was a post-landing discussion between the flightcrew and the cabin crew about the landing and the [captain] stated that the landing was a little bit hard but within the limits."
No records were made in the aircraft technical logbook and the A320 flew another eight sectors between Pristina and Basel over the next two days.
But the first officer had been "doubtful" over the landing and, following a private talk with the carrier's training manager, the data-management unit was refilled with paper on 5 December - after which it generated a load report showing the touchdown impact had been excessive.
The aircraft was then grounded for inspection before being flown, under special permission, to a Romanian maintenance station in Craiova. All four main wheels were replaced - although Airbus viewed this as unnecessary - along with a shock-absorber assembly which was listed as unserviceable. The aircraft returned to service on 28 December.
The inquiry says the A320 conducted a non-precision VOR-DME approach to Pristina's runway 35, with the crew disengaging the autopilot at 2,000ft.
Visual contact with the runway was confirmed at 3nm (5.5km) and the first officer declared the approach stable at 1,000ft. The aircraft commenced a right turn at 500ft to align with the runway.
But the flight-data recorder information shows that, shortly after passing through 500ft, the aircraft was subjected to "unusual" nose-up and nose-down commands, the investigators state.
Its pitch increased to 6°, slowing the rate of descent to 200ft/min (1m/s), but three "significant" forward-stick inputs from the captain lowered the pitch to 2° and increased the descent rate to 880ft/min. While the captain attempted to arrest this descent at 20ft, with full aft-stick input, this was unsuccessful.
"This pitch-control input was applied at very low altitude and the vertical speed did not decrease sufficiently," says the inquiry, adding that the hard landing was consequently "unavoidable".
While the absence of paper in the A320's data-management unit was formally noted in late November 2017, the 120-day allowance on the minimum equipment list meant the defect did not need to be fixed until late March 2018.
Investigators point out that Orange2fly did not have ACARS capability at its headquarters which would have provided automatic notification of the hard landing without having to rely on the paper printout or pilot report. The inquiry has recommended that the carrier implement ACARS, and provide additional training to pilots regarding reporting of hard or overweight landings.