Missed Opportunities

COVERSTORY BY MARK LACAGNINA missed opportunities The pilots did not notice a misset pressurization mode selector and misidentified a warning about cabin altitude. After hypoxia struck, autoflight systems kept the 737 flying until the fuel ran out. 18 | FLIGHT SAFETY FOUNDATION | AEROSAFETYWORLD | JANUARY 2007 COVERSTORY BY MARK LACAGNINA missed opportunities he Helios Airways Boeing 737- flight management computer and A green “ALTN” light indicates that 300 was climbing through 16,000 the autopilot, depletion of the the system is in the alternate mode. A ft after departing from Larnaca, fuel and engine flameout, and the green “MANUAL” light indicates that Cyprus, on Aug. 14, 2005, when impact of the aircraft with the the system is in the manual mode. Tthe captain reported a takeoff configu- ground.” ration warning to operations person- The 737-300 pressurization system was Unscheduled Leak Check nel. The warning horn that the captain designed to maintain a cabin altitude The mode selector had been set to heard was actually for a problem with of 8,000 ft at the aircraft’s maximum manual for a pressurization-system the cabin-pressurization system, ac- certified ceiling, 37,000 ft. The mode check the morning before the accident. cording to the Hellenic Air Accident selector, which is in an overhead The unscheduled maintenance was per- Investigation and Aviation Safety Board panel above the first officer’s seat, has formed in response to a technical log in Greece. Unaware of the problem, the three positions: “AUTO” (automatic), entry by the flight crew that had landed pilots were incapacitated by hypoxia, “ALTN” (alternate) and “MAN” (photo, the aircraft in Larnaca at 0425 after a and the aircraft, on automatic control, page 21). With the system in automatic flight from London. The technical log continued toward Athens, entered a mode, which normally is selected for entry stated that an inspection of the holding pattern and plunged to the flight, the crew selects the planned aft galley service door was required ground after the engines flamed out. cruise altitude and destination altitude because the door seal “freezes, and hard None of the 121 occupants survived. in the appropriate windows on the bangs are heard during flight.” In its final report, the board said that mode selector, and a cabin pressure After conducting a visual inspec- the direct causes of the accident were: controller positions the outflow valve tion of the door and the pressurization to maintain a programmed cabin- check, a ground engineer (maintenance • “Nonrecognition that the cabin pressure schedule. The alternate mode technician) wrote in the technical log pressurization mode selector was is selected to change from one cabin that no defects were found and that no in the ‘MAN’ (manual) position pressure controller to the other. With leaks or abnormal noises occurred. The during the performance of the the system in manual mode, the flight report said that although the airplane ‘Preflight’ [checklist] procedure, crew has “direct” control of pressuriza- maintenance manual included no spe- the ‘Before Start’ checklist and the tion, using a toggle switch to position cific requirement to return the mode ‘After Takeoff’ checklist; the outflow valve. “Manual control is selector to “AUTO” after the check, primarily used as a backup to automatic it would have been prudent for the • “Nonidentification of the warn- control,” the report said. ground engineer to have done so. ings and the reasons for the There are four annunciator lights The report also noted that a activation of the warnings (cabin above the pressurization control panel. rapid decompression of the accident altitude warning horn, passenger An amber “AUTO FAIL” light indicates aircraft’s cabin had occurred during a oxygen masks deployment indica- a failure of the automatic mode. An flight from Warsaw, Poland, to Larnaca tion, master caution); [and,] amber “OFF SCHED DESCENT” light on Dec. 16, 2004. The decompres- • “Incapacitation of the flight crew illuminates if the aircraft descends sion occurred when the aircraft was at due to hypoxia, resulting in the before reaching the planned cruise Flight Level (FL) 350 (approximately © Kostas Iatrou/aviation-images.com continuation of the flight via the altitude set in the “FLT ALT” window. 35,000 ft) and near the point at which www.FLIGHTSAFETY.ORG | AEROSAFETYWORLD | JANUARY 2007 | 19 COVERSTORY the flight crew had planned to begin descent. found during a cabin pressure leak check and The crew conducted an emergency descent outflow valve test. and landed the aircraft at the destination. The Cyprus Air Accident and Incident Investigation A Mode Overlooked Board, which investigated the incident, con- The accident occurred during a scheduled flight cluded that the decompression likely occurred to Prague, Czech Republic, with an en route either because the outflow valve opened due stop in Athens. The captain, 59, was a native of to an electrical malfunction or the aft galley Germany. He had 16,900 flight hours, including service door opened due to an improperly po- 5,500 flight hours as a 737 captain. He had been sitioned handle. Maintenance actions included employed by Helios Airways from May 2004 adjustment and rigging of the door and re- to October 2004 and had flown for two other placement of the no. 2 cabin pressure controller aircraft operators before returning to Helios and the chemical oxygen-generator cylinders Airways in May 2005. “According to interviews in the passenger service units. Technical log of his peers at [Helios Airways], during the first entries indicated that no abnormalities were period [of employment], he presented a typical ‘command’ attitude, and his orders to the first officers were in command tone,” the report said. Boeing 737-300 “During the second period, his attitude had im- proved as far as his communication skills were concerned.” The first officer, 51, was a native of Cyprus. He had 7,549 flight hours, including 3,991 flight hours in type. “He had expressed his views several times [to family, colleagues and friends] about the captain’s attitude,” the report said. “He had also complained about the organizational structure of the operator [and its] flight sched- uling, and he was seeking another job.” The report said that a review of his training records “disclosed numerous remarks and recommenda- tions made by training and check pilots refer- ring to checklist discipline and procedural (SOP © Alan Lebeda/aviation-images.com [standard operating procedure]) difficulties.” The flight crew did not reset the pressuriza- he Boeing 737 was designed to use many components and as- tion mode selector to automatic before departure. semblies from the 727. Deliveries of the first production model, “The fact that the mode selector position was Tthe 737-200, which has Pratt & Whitney JT8D engines, began in not rectified by the flight crew during the aircraft 1967. The larger 737-300 was introduced in 1984 with quieter and preflight preparations was crucial in the sequence more fuel-efficient CFM International CFM56 engines, rated at 20,000 of events that led to the accident,” the report said. lb (9,072 kg) thrust. The 737-300 can accommodate 128 to 149 passengers and 1,068 The challenge for the pertinent item on cubic ft (30 cubic m) of cargo. Maximum standard takeoff weight is the “Preflight” checklist refers to both the air- 124,500 lb (56,473 kg). Maximum landing weight is 114,000 lb (51,710 conditioning and pressurization systems. The kg). Maximum operating speed is Mach 0.82. Cruising speed is Mach response is: “Pack(s), bleeds on, set.” The report 0.75. said that the pressurization mode selector rarely Production ceased in 2000 after 1,113 737-300s were built. is positioned to a setting other than automatic, Source: Jane’s All the World’s Aircraft and many pilots interviewed during the investigation said that they typically respond “set” 20 | FLIGHT SAFETY FOUNDATION | AEROSAFETYWORLD | JANUARY 2007 COVERSTORY after checking only that the cruise altitude and The pressurization landing altitude are set correctly. system mode selector The aircraft departed from Larnaca at 0907. was in the manual, The first item on the “After Takeoff” checklist “MAN,” position is to check the pressurization system. “This was during the accident the second missed opportunity to note and cor- flight and was moved rect an earlier error,” the report said. beyond that position About 0910, the flight crew was cleared to by impact forces. climb to FL 340 and to fly directly to the Rhodos (Rhodes) VOR (VHF omnidirectional radio). The captain’s acknowledgement of the clearance was the last recorded communication between Hellenic Air Accident Investigation and Aviation Safety Board the flight crew and air traffic control (ATC). made in the two months preceding the acci- Warning Horn dent. “The crew became preoccupied with the The aircraft was climbing through 12,040 ft, and equipment-cooling-system situation and did cabin altitude was slightly below 10,000 ft, at not detect the problem with the pressurization 0912, when the warning horn sounded. Activa- system,” the report said. tion of the warning horn in flight indicates a The equipment-cooling system includes fans problem with cabin pressurization, the report and ducts that direct cool air to and warm air said. On the ground, the warning horn sounds away from electronic equipment on the flight when the throttles are advanced and the aircraft deck and in the electrical and electronic bay. is not in the correct takeoff configuration “Loss of airflow (mass flow) due to failure of — that is, with trim, flaps and/or speed brakes an equipment cooling fan or low air density set incorrectly. associated with excessive cabin altitude results According to the quick reference handbook, in illumination of the related equipment cooling among the actions that the flight crew should ‘OFF’ light,” the report said.

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