XL Airways Germany Flight 888T

XL Airways Germany Flight 888T was an acceptance flight for an Airbus A320 on 27 November 2008. The aircraft crashed into the Mediterranean Sea, 7 km off Canet-en-Roussillon on the French coast, close to the Spanish border, killing all seven people on board. The subsequent investigation attributed the accident to incorrect maintenance procedures that allowed water to enter and freeze in the angle-of-attack sensors during flight, rendering them inoperative, combined with the crew's attempt to perform a test at a dangerously low altitude.

Flight test purpose

The aircraft was on a flight test (or "acceptance flight") that had taken off from Perpignan–Rivesaltes Airport, made an overflight of Bay of Biscay, before flying back to Perpignan Airport. At the time of the crash, it was due to commence a touch-and-go landing at Perpignan Airport before flying to and landing in Frankfurt Airport, from where it would have taken a ferry flight to Auckland, New Zealand. The flight took place following light maintenance and repainting to Air New Zealand livery in preparation for its transfer from XL Airways Germany, which had been leasing the aircraft from Air New Zealand, the owner.

Accident

Shortly after take-off from Perpignan–Rivesaltes Airport at 14:44 UTC, the crew flight requested the airspace and headed to begin their test manoeuvres. However, their request was firmly denied by air traffic control, telling the flight "I'm afraid we cannot do test flights in general air traffic, you have to be operational air traffic sir for that". Flight 888T, instead of completing an operational air traffic flight plan (which would have allowed their tests with the assistance of a dedicated controller), had filed a general aviation flight plan, which didn't accommodate test flights. After further pleas to the controller were rejected, the crew decided to turn around and head back to Perpignan. Regardless, they would improvise on the way and do as many of the tests as they could.

At 15:33 UTC on the flight back to Perpignan, the crew requested clearance to 39,000 feet to test the auxiliary power unit (APU). The controller replied, "I understand sir but you know you are on general aviation and many sectors above so it's a bit more difficult for us than different controllers". However, despite the controller's reluctance to approve it, the request was granted. The crew of Flight 888T proceeded to test the auxiliary power unit, bank angle protections and the overspeed warning among other things at 39,000 feet. Continuing their descent to Perpignan, the crew of Flight 888 signed off with the Bordeaux air traffic controller who gave them a sharp send-off "Yes for the next time sir it'll be better not to do your… your flight in general aviation".

From there, they continued with the remaining checks. Captain Horrell raised the question of the low-speed check. The procedure was supposed to be performed at approximately 14,000 feet, but Flight 888T was already descending toward Perpignan. Horrell described the actions required as the aircraft descended through approximately 8,000 to 6,000 feet.

The crew was then cleared for the ILS approach to runway 33 and instructed to descend toward 5,000 feet. While the aircraft was passing through cloud, Captain Käppel said, “I think we will have to do the slow flight probably later.” Horrell replied, “Okay, yeah.” Käppel continued, “Or we do it on the way to Frankfurt or I even skip it.” This suggestion went unanswered. However, after descending below the clouds at a little over 4,000 feet, Captain Käppel asked Horrell what he wanted him to do. Horrell then described the actions required for the low-speed test. With barely 3,000 feet between them and the ocean, following instructions of the New Zealand pilot sitting in the jump seat, Captain Norbert Käppel moved the throttles to idle and raised the nose of the aircraft by pulling back on his side-stick, dramatically slowing the speed of the aircraft. The pilots were fully expecting the A320's alpha floor (α-Floor) protections to come into effect (which pushes the engines to full power during a stall).

As the speed of the aircraft dropped to a critical point in which it could no longer maintain flight, the angle of attack increased, and a stall alarm sounded in the cockpit. The plane shook and made a hard bank to the left. After manually applying full power, initially, the crew were able to regain control again and come out of the stall. However, the aircraft began a rapid and uncontrolled climb. What the pilots hadn't noticed, in the chaos, the aircraft had switched from the A320's normal law (with automations and protections) to direct law, meaning, normally automated controls were now left to the pilots. Although the captain was pushing forward on his side-stick in an attempt to lower the nose again, the plane kept climbing. In normal law, moving the side-stick prompts the computer to adjust the horizontal stabiliser to control the pitch. Now, in direct law, with no such assistance from the computer, the pilots needed to use both the side-stick and the manual trim wheel to lower the nose of the aircraft. A warning on their display advised them of this, but they likely didn't notice, potentially in part because the aural stall warning covered the warning indicating a change of flight control laws. Reaching 57 degrees nose up, while in a hard bank to the left, their altitude peaked at just below 4,000 feet and the airspeed dropped to just 40 knots, far too slow to fly. Shuddering violently, the aircraft crashed into the Mediterranean Sea, 7 km off the coast of Étang de Canet-Saint-Nazaire near Canet-en-Roussillon. All seven people on board were killed.