A United Parcel Service ( UPS ) Boeing 747-400F, registration N571UP, and operating as flight UPS6, crashed while on approach to Dubai International Airport (DXB) on 3rd September 2010. Later investigations revealed that the crash occurred due to a fire, developed through the ignition of a cargo compartment containing Lithium batteries, which reduced visibility for flight crew.
The aircraft, a 2007 factory built freighter, and one of the last few 747-400Fs built had took off from Dubai at 1853L on a leg bound to Cologne, Germany.
At 1915L, the UAE ATC had received information from Bahrain ATC that the aircraft was returning to Dubai due to a smoke in the cockpit and inability to maintain altitude.
Pilots on Bahrain Control frequency had reported that the crew had requested frequent updates on their speed and altitude as they were unable to change frequency and to read the instruments.
The aircraft was cleared to land in Dubai but was approaching the runway too fast and too high and were offered to either divert to Sharjah or join a right hand downwind for another visual approach to runway 12L.
However, the aircraft passed Dubai high overhead, tracked southwest and lost altitude, when the radar contact was lost at 1942L.
he aircraft had crashed into a free area between highways E66 and E311 in Dubai.
Both flight crew members had perished in the accident.
Investigation and findings
Following the incident, the US FAA reported that the aircraft’s cargo contained a large quantity of lithium batteries. It further stated that the fire suppression agent Halon 1301 used in Class C cargo compartments was ineffective in suppressing fires caused by lithium batteries.
The final accident investigation report, by the UAE GCAA stated that the probable causes of the crash were:
– A large fire developed in palletized cargo on the main deck at or near pallet positions 4 or 5, in Fire Zone 3, consisting of consignments of mixed cargo including a significant number of lithium type batteries and other combustible materials. The fire escalated rapidly into a catastrophic uncontained fire.
– The large, uncontained cargo fire, that originated in the main cargo deck caused the cargo compartment liners to fail under combined thermal and mechanical loads.
– Heat from the fire resulted in the system/component failure or malfunction of the truss assemblies and control cables, directly affecting the control cable tension and elevator function required for the safe operation of the aircraft when in manual control.
– The uncontained cargo fire directly affected the independent critical systems necessary for crew survivability. Heat from the fire exposed the supplementary oxygen system to extreme thermal loading, sufficient to generate a failure. This resulted in the oxygen supply disruption leading to the abrupt failure of the Captain’s oxygen supply and the incapacitation of the captain.
– The progressive failure of the cargo compartment liner increased the area available for the smoke and fire penetration into the fuselage crown area.
– The rate and volume of the continuous toxic smoke, contiguous with the cockpit and supernumerary habitable area, resulted in inadequate visibility in the cockpit, obscuring the view of the primary flight displays, audio control panels and the view outside the cockpit which prevented all normal cockpit functioning.
– The shutdown of PACK 1 for unknown reasons resulted in loss of conditioned airflow to the upper deck causing the Electronic Equipment Cooling [EEC] system to reconfigure to “closed loop mode”. The absence of a positive pressure differential contributed to the hazardous quantities of smoke and fumes entering the cockpit and upper deck, simultaneously obscuring the crew’s view and creating a toxic environment.
– The fire detection methodology of detecting smoke sampling as an indicator of a fire is inadequate as pallet smoke masking can delay the time it takes for a smoke detection system to detect a fire originating within a cargo container or a pallet with a rain cover.
The aircraft had had an uneventful flight until it entered the Bahrain Flight Information Region, and 21 minutes since take off – at which point an alert for Main Deck Fire (FIRE MAIN DK FWD) was indicated by the aircraft. At this point the Captain assumed control as the Pilot Flying, and the First Officer began running the relevant checklist. The crew declares an emergency, informs the ATC of the intention to return to Dubai and requests to land as soon as possible.
While Doha airport was closer to the aircraft’s position at the time, the decision to return to Dubai is believed to have been led by the crew not being fully aware of the extent of the fire at that point (Ed- returning to an airport which is an operational base for the airline can be sometimes preferred by crew, provided there is no immediate danger, as that would enable an easier handling of the technical issue and minimise disruption). By the time the smoke in cockpit and fire damaged controls became apparent, diverting to Doha was no longer a feasible option.
As the fire spread further, crew had donned their oxygen masks and reported inability to see their controls. The Captain had selected Auto Pilot following pitch control problems.
Effective elevator and rudder control was only available with the autopilots. The aircraft was controllable with the AP as the servos are electrically controlled and hydraulically actuated, which for pitch control is in the tail section aft of the rear pressure bulkhead, and the fire had not compromised the electrical cabling to the actuators.
Further excerpt from the final report:
53. The PF was not fully aware of the extent of the control limitations, could not see the EICAS messages and was not aware of all of the systems failures.
54. The Captain called for the smoke evacuation handle to be pulled as the smoke accumulated in the cockpit. The smoke evacuation handle when pulled opens a port in the cockpit roof, which if the smoke is sustained and continuous, will draw smoke through the cockpit as the pressure is reduced by the open port venturi effect compounding the problem. The smoke evacuation handle remained open for the remainder of the flight.
55. There are several instances of checklist interruption at critical times at the beginning of the emergency. The speed and quick succession of the cascading failures task saturated the crew. The smoke in the cockpit, combined with the communications problems further compounded the difficult CRM environment. With the incapacitation of the captain, the situation in the cockpit became extremely difficult to manage.
56. One factor when dealing with the QRH and running checklists is that the B747 does not have a hot microphone function. This caused increasing difficulty managing cascading failures and high workload.
57. The crew was unable to complete the Fire Main Deck checklist. The aircraft was not leveled off at 25,000 ft. Directly descending to the 10,000 ft may have exacerbated fire and smoke problem due to the extra available oxygen.
58. The Captain instructed the F.O. to input DXB RWY12L into the FMC. This action was completed with difficulty due to the smoke. There was no verbal confirmation of the task completion, however, the the aircraft receivers detected the DXB Runway 12L glide slope beam when approaching Dubai.
59. Captain made a comment mentioning the high cockpit temperature, almost immediately the Captains oxygen supply abruptly stopped without warning, this occurred seven minutes six seconds after the first Main Deck Fire Warning.
60. The Captain’s inability to get oxygen through his mask was possibly the result of the oxygen hose failure near the connector. The high thermal loading was conducted through the supplementary oxygen stainless steel supply lines heating the supplementary oxygen directly affecting the flexible hose connector causing the oxygen supply line to fail.
61. Systems analysis indicates that the oxygen supply is pressure fed, therefore venting oxygen could be released by a failed oxygen hose which could then discharge until the oxygen line fails or the oxygen supply is depleted.
62. The Captain requests oxygen from the F.O. several times over approximately one minute. The First Officer due to possible task saturation was not able to assist the Captain.
63. The oxygen requirement of the Captain became critical, the Captain removes the oxygen mask and separate smoke goggles and leaves the seat to look for the supplementary oxygen. The Captain did not return. The Captain was in distress locating the supplementary oxygen bottle and could not locate it before being overcome by the fumes.
64. The Captain was incapacitated for the remainder of the flight. A post-mortem examination of the Captain indicates that the cause of death was due to carbon monoxide inhalation.
65. A full face emergency oxygen supply is available in the cockpit. Oronasal masks are available in the lavatory, jump seat area and crew bunk area.
66. Due to the Captain’s incapacitation the F.O became P.F. for the remainder of the flight, operating in a single pilot environment. Exposure to this type of environment in a controlled training environment could have been advantageous to the remaining crew member.
67. The FO had breathing difficulties as the aircraft descended as the normal mode function of the mask supplies oxygen at a ratio to atmospheric, ambient air. The amount of oxygen supplied was proportional to the cabin altitude.
68. The cockpit environment remained full of smoke in the cockpit, from a continuous source near and contiguous with the cockpit area for the duration of the flight.
69. As the flight returned towards DXB, the crew were out of VHF range with BAE-C and should have changed VHF frequencies to the UAE FIR frequency 132.15 for the Emirates Area Control Center [EACC]. Due to the smoke in the cockpit the PF could not view the audio control panels to change the frequency selection for the duration of the flight.
70. The flight remained on the Bahrain frequency 132.12 MHz on the left hand VHF ACP for the duration of the flight. To solve the direct line of communication problem, BAE-C requested traffic in the vicinity to relay communication between crew and BAE-C.
71. The PF made a blind Mayday call on 121.5 MHz at 15:21 UTC.
72. The PF had to relay all VHF communication through other aircraft. The radio communication relay between the PF, the relay aircraft and the ANS stations resulted in confusion communicating the nature and intent of the PF’s request for information with the required level of urgency.
73. The PF requested from the relay aircraft immediate vectors to the nearest airport, radar guidance, speed, height and other positional or spatial information on numerous occasions to gauge the aircraft’s position relative to the aerodrome and the ground due to the persistent and continuous smoke in the cockpit.
74. The relay aircraft did not fully comprehend or communicate to the BAE-C controller the specific nature of the emergency and assistance required, particularly towards the end of the event sequence.
75. There was a multi-stage process to complete a standard request for information between the accident flight and the destination aerodrome via the relay aircraft and the ATCU.
76. The flight crew did not or could not enter the transponder emergency code 7700, however all ATCUs were aware that the airplane was in an emergency status.
77. DXB controllers were aware that the flight was in an emergency status, however were not aware of the specific nature of the emergency or assistance required, due to the complex nature of the relayed communications.
78. There was no radar data sharing from the UAE to Bahrain ATC facilities. Bahrain had a direct feed that goes to the UAE but there was no reciprocal arrangement. This lack of data resulted in the BAE-C ATCO not having radar access the SSR track of the accident flight.
79. The ATC facilities are not equipped with tunable transceivers.
80. The accident aircraft transmitted on the Guard frequency 121.5 Mhz. The transmissions were not heard by the EACC or DXB ATC planners due to the volume of the 121.5 Mhz frequency being in a low volume condition.
81. The PF did not respond to any of the calls from the ACC or the relay aircraft on 121.5 MHz, which were audible on the CVR, after the Mayday transmission.
82. During the periods when direct radio communications between the pilot flying and the controllers was established, there was no negative effect. Therefore it is likely that if direct 121.5 contact had been established the communications task could have been simplified.
83. The relay aircraft hand off between successive aircraft caused increasing levels of frustration and confusion to the PF.
84. All Dubai aerodrome approach aids and lighting facilities were operating normally at the time of the accident.
85. There is no requirement for full immersion smoke, fire, fumes cockpit training for flight crews.
86. The PF selected the landing gear handle down. The landing gear did not extend, likely due to loss of cable tension.
87. The flaps extended to 20°. This limited the auto throttle power demand based on the max flap extension placard speed at 20° Flaps.
88. The PF was in radio contact with a relay aircraft, who advised the PF through BAE-C that Sharjah airport was available, and a left hand turn onto a heading of 095° was required.
89. The PF made an input of 195° into the MCP for an undetermined reason when 095° was provided. The aircraft overbanked to the right, generating a series of audible alerts. It is probable that the PF, in the absence of peripheral visual clues, likely became spatially disorientated by this abrupt maneuver.
90. The aircraft acquired 195°, the AP was selected off. The throttle was retarded and the aircraft began a rapid descent.
91. The PF was unaware of the large urban area directly in the airplane’s path. The aircraft began a descent without a defined landing area ahead.
92. Spatial disorientation, vestibular/somatogyral illusion due to unreliable or unavailable instruments or external visual references are a possibility. The PF was unaware of the aircraft location spatially. The PF may have been attempting an off airfield landing, evidenced by numerous control column inputs.
93. The control column inputs to the elevators had a limited effect on the descent profile. The pilot made a series of rapid column inputs, in response to GPWS warnings concerning the sink rate and terrain. The inputs resulted in pitch oscillations where the elevator response decreased rapidly at the end of the flight
94. The available manual control of pitch attitude was minimal, the control column was fully aft when the data ends, there was insufficient trailing edge up [nose up] elevator to arrest the nose down pitch. Control of the aircraft was lost in flight followed by an uncontrolled descent into terrain.
The investigation further discovered that the aircraft had been loaded a compartment of lithium batteries as cargo in Hong Kong, however that the shipper had not properly declared these and did not provide a Test Report in compliance with the UN Recommendations with regard to transportation of dangerous goods.
The aircraft was airworthy (with some Minimum Equipment List items logged – which had no impact on accident) and the crew was licensed and no identified fatigue issues.