Comunque è già molto interessante capire le cause di questo incidente e vi iscrivo qui sotto le cause principali, per chi volesse leggersi poi l'intero rapporto molto interessante e pieno di fotografie, fate riferimento al link precedente.
Come ogni volta le cause che portano a questo genere di fatalità sono la poco coordinazione tra l'equipaggio e la mancanta attenzione nel riconoscere situazioni di pericolo prima che queste diventino incontrollabili e portino l'aereo in un situazione tale dove non si è in grado di fare nulla.
Negli ultimi giorni è uscito anche un'altro rapporto a riguardo di un incidente aereo in Spagna dove era coinvolto un B737/8 della Air Europe nel 2008, se vi andate a leggere il report vedrete che le situazioni, pur se differenti , hanno dei punti in comune.
3.1 Cause Related Findings
- The flight crew did not recognize the increasing sink rate on short final.
- The First officer delayed the flare prior to the initial touchdown, thus resulting in a bounce.
- The flight crew did not recognize the bounce.
- The Captain attempted to take control of the aircraft without alerting the First Officer resulting in both flight crews acting simultaneously on the control column.
- During the first bounce, the Captain made an inappropriate, large nose-down column input that resulted in the second bounce and a hard landing in a flat pitch attitude.
- The flight crew responded to the bounces by using exaggerated control inputs.
- The company bounced-landing procedure was not applied by the flight crew.
3.2 Other Findings
- The flight crew was properly licensed and was qualified on the type of aircraft.
- The meteorological conditions did not contribute to the accident.
- The aircraft was properly certificated and had been maintained in accordance with approved procedures.
- The aircraft had no oral or visual indicator, such as a HUD, to inform the flight crew of a bounced landing.
- The flight recorders were located just aft of the lower center cargo door.
- The FRS response was rapid and efficient.
- During the FRS operation, some FRS personnel were not wearing their PPE.
- Time synchronization at the KKIA airport was deficient.
- KKIA Airport Operations recordings were not available.
- Some KKIA Airport vehicles did not have rotating beacons.
- KKIA Airport Security did not maintain proper control of the accident site during the initial response to the accident.
- KKIA Airport security cameras provided information that was useful to the investigation.
GACA reported the captain (ATPL, 8,270 hours total, 4,466 hours on type) was pilot monitoring, the first officer (ATPL, 3,444 hours total, 219 hours on type) was pilot flying, the two were rostered together for the first time, the first officer had joined Lufthansa Cargo 7 months prior to the accident.
The aircraft departed Frankfurt with a cargo consisting of a combination of pallets and rigid cargo containers as well as 44 shipments of dangerous goods that had been loaded into the forward lower cargo compartment, and 12 shipments containing corrosive materials, toxic materials, magnetized materials and flammable liquids.
The aircraft was vectored for an ILS approach to runway 33L, flaps were set to 35 degrees and Vref was determined at 158 KIAS according to an estimated landing weight of 207 tons. The first officer disengaged autothrottle and autopilot for the final approach. The aircraft descended fully established on localizer and glideslope until about 25 seconds prior to touchdown, when the aircraft descended about half a dot below the glideslope, the airspeed oscillated between 160 and 170 KIAS.
The speed above ground was 164 knots until about 20 seconds prior to touchdown, then increased and reached 176 knots at touchdown.
About 1.7-2.0 seconds before touchdown, about 23-31 feet AGL, the first officer initiated the flare, the main gear touched down 945 feet past the runway threshold at a descent rate of 780 fpm resulting in a vertical acceleration of +2.1G. The aircraft bounced off the runway, the main gear reached 4 feet above runway surface with the spoilers fully extended due to main wheel spin up.
During the bounce the captain, pilot monitoring, pushed the control column resulting in a second touchdown in a flat pitch attitude with both main gear and nose gear contacting the runway surface at a descent rate of 660 fpm resulting in a vertical acceleration of +3.0G.
Prior to second touchdown both pilots pulled the control column which combined with the nose gear bouncing off the runway resulted in the pitch attitude reaching 14 degrees nose up, the spoilers extended to 60 degrees while the nose gear was compressed. Following the second bounce the main wheels reached a height of 12 feet above runway surface.
Early in this second bounce the captain pushed the control column fully forward, the elevators responded, shortly before third touchdown both pilots pulled the control column with the elevators responding accordingly and reducing the pitch down rate, the aircraft however still was pitching down at touch down, which occurred at a descent rate of 1020 fpm and a vertical acceleration of +4.4G. At this point the fuselage ruptured behind the wing trailing edge, a fuel line to the number 2 APU and a fuel transfer line to the tail fuel tank were severed and fuel spilled with the left hand wheel well. A fire ignited and expanded into the upper cargo area.
The captain attempted to keep the aircraft within runway boundaries, not knowing the fuselage had severed he deployed thrust reversers, only engines #1 (left) and #3 (right) responded. The captain instructed the first officer to declare Mayday.
Fire fighters located at their station 2 near taxiways A and P saw the MD-11 sliding and exiting the runway with smoke coming from the top of the aircraft and immediately responded.
The aircraft subsequently went left off the runway, upon departing the runway edge the nose gear collapsed. Following the first officer's Mayday call tower issued an Alert 3. Personnel of fire station 2 were already on their way when the Alert was issued.
The aircraft came to a stop about 8800 feet past the runway threshold and about 300 feet off the runway center line. All engines were shut off using the fuel cut off levers, both crew evacuated through the L1 door via the slide, the mid portion of the aircraft was on fire. Emergency services responded and arrived within a very short time.
Both pilots were taken to a hospital.
The aircraft was destroyed.
Security cameras videotaped the landing, the recordings complemented the later testimonies by the crew, witnesses on the ground and flight data recordings. Their recordings showed no smoke or fire until a short time after the fuselage ruptured, subsequently smoke rose out of the fuselage rupture, no fire was apparent when the aircraft veered off the runway and disappeared in a cloud of smoke and dust. After the dust settled fire station 2 became visible again at the camera located at the left side of the runway 33L and close to the aircraft's final position. About 55 seconds after the aircraft had crossed this camera's view, the first fire fighting vehicle left fire station 2, the second vehicle departed the station 20 seconds later, the vehicles crossed runway 33L 100 and 115 seconds after leaving the station. Emergency services of the airport's main unit and station 1 responded as well following the general alert, emergency services from outside the airport were called in.
Emergency services reported that upon their arrival the fire was limited to the center main wheel well (editorial note: while the fuel spill occurred in the left main gear well). By the time they arrived at the aircraft both pilots had already evacuated, the captain had received some cuts and the first officer was complaining about back pain.
The fire spread and later became visible at the crown of the fuselage. The fire was extinguished 20 hours after the accident, but re-ignited on two occasions over the next days due to still smouldering cargo. As a manned fire fighting vehicle remained present at the wreckage those fires were quickly extinguished.
In post flight interviews the first officer reported he sensed a sinking or increased sinking while descending through 80 feet AGL. He either increased engine power or delayed retarding engine power and initiated flare at about 30-40 feet AGL. During the flare he lowered the nose slightly. He had no clear recollection of his actions following first touchdown, he did recall when the captain instructed him to declare Mayday. The Mayday call however was delayed until after the aircraft had exited the runway as the first officer needed to recover his headset and microphone from the floor.
The airport needed to be completely closed as result of the accident as runway 33R was closed and needed an inspection before re-opening 16 minutes after the accident.
Two aircraft already holding at the holding point of runway 33L were cleared to taxi onto runway 33L and vacate the runway via taxiway A3, no debris was observed by the crews of these aircraft.
The GACA reported that security guards were located about 50 meters from the position where the aircraft came to a stop, however, did not control access to the accident site permitting emergency services as well as other, unauthorized people to access the accident site. Unauthoritzed people were present until the end of the fire fighting operation, that ended 20 hours after the accident.
Both flight data recorders were recovered however showed extensive fire damage. The memory cards showed they had been exposed to heat but not critically, the memory cards showed no defect and were successfully read out.
The 44 shipments of dangerous cargo in the forward lower cargo had not been damaged by the fire and were recovered. The 12 shipments of dangerous goods in the aft portion of the aircraft were heavily damaged or destroyed by fire.
None of the Halon fire suppression systems in the cabin and cargo compartments had been activated.
The GACA reported that due to the heavy damage the source of the ignition of the fire could not be identified, however, the spray of the fuel in the left hand wheel well likely fed the fire.
The GACA reported that between 1992 and 2010 twentynine bounced and severe hard landing events had been recorded with MD-11s that resulted in substantial aircraft damage. The investigation found, that the recognition of a bounced landing on the MD-11 appears to be difficult, mainly because of the lack of sensing the bounce and the absence of a visual or oral indication of a bounce. Instructors believed the only was to detect a bounced landing would be via the radar altimeter, however, flight crews rarely, if not ever, monitor the instruments following the flare and touch down. Another carrier using Head Up Guidance Systems including Enhanced Flight Visibility System. This Head Up Display would also provide indication of a bounced landing.
GACA analysed that "the aircraft and in particular the elevators responded to the flight crew inputs on the control column. The LSAS commands remained within its authority limits and as such, there was no evidence to indicate that the LSAS may have contributed to this accident."
The control inputs of the crew however can not be as clearly analyzed. The crew would make control inputs based on their perceiption of the aircraft's motion, the parameters leading to that perceiption being height of the cockpit above the runway, the rate of change of height of the cockpit above the runway, pitch angle and pitch rate, load factors, force feedback on the controls and cockpit and engine sounds.
The GACA thus analysed with regards to the large nose down control input during the first bounce: "The reason for this large nose-down input by the Captain is unclear. One possibility is that the Captain did not realize the aircraft had bounced and was attempting to de-rotate the aircraft while assuming the main gear were still on the ground. Of note, from t = 1.0 to 1.7 sec. during the first bounce, the cockpit descended, while the C of G and gear climbed. This effect resulted from the decreasing pith angle ( and the consequent vertical translation of the cockpit as the aircraft rotated about the C of G, which was about 89 ft behind the cockpit. The decreasing cockpit height during this time may have made it more difficult for the pilots to determine that the aircraft had bounced and that the main gear were no longer on the runway."
The GACA continued that the captain should have said "I have control" as soon as he applied the first control input during the first bounce. The omission of that call led both pilots to provide control inputs, not always in unison, which aggravated the serious situation.