Japan Airlines Flight 123



Japan Airlines Flight 123 was a flight from Tokyo's Haneda Airport to Osaka International Airport in Japan. On August 12, 1985, a Boeing 747SR operating this route suffered a sudden decompression twelve minutes into the flight and crashed in the area of Mount Takamagahara, Ueno, Gunma Prefecture, 100 kilometres (62 miles; 54 nautical miles) from Tokyo thirty-two minutes later. The crash site was on Osutaka Ridge, Mount Osutaka.

Background

 * Captain Masami Takahama (高浜 雅己, 'Takahama Masami') served as a training instructor for First Officer Yutaka Sasaki on the flight, supervising him while handling the radio communications, while also acting as the first officer. Takahama was a veteran pilot, having logged approximately 12,400 total flight hours, roughly 4,850 of which were accumulated flying 747s. Takahama was aged 49 at the time of the accident.
 * First Officer Yutaka Sasaki (佐々木 祐, 'Sasaki Yutaka') was undergoing training for promotion to the rank of captain and flew Flight 123 as one of his final training/evaluation flights, acting as captain on the flight. Sasaki, who was 39 years old at the time of the accident, had approximately 4,000 total flight hours to his credit and he had logged roughly 2,650 hours in the 747.
 * Flight Engineer Hiroshi Fukuda (福田 博, 'Fukuda Hiroshi'), a 46-year-old veteran flight engineer who had approximately 9,800 total flight hours, of which roughly 3,850 were accrued flying 747s. He was veteran and was flying with the Japan Air Self Defense Force, but died later after it crashed.

Accident
The aircraft took off from Runway 15L at Haneda Airport in Ōta, Tokyo, Japan, at 6:12 p.m., twelve minutes behind schedule. About 12 minutes after takeoff, at near cruising altitude over Sagami Bay, the aircraft underwent rapid decompression bringing down the ceiling around the rear lavatories, damaging the unpressurized fuselage aft of the plane, unseating the vertical stabilizer, and severing all four hydraulic lines. A photograph taken from the ground confirmed that the vertical stabilizer was missing.

The pilots set their transponder to broadcast a distress signal. Afterwards, Captain Takahama contacted Tokyo Area Control Center to declare an emergency, and to request to return to Haneda Airport, descending and following emergency landing vectors to Oshima. Tokyo Control approved a right-hand turn to a heading of 90° east back towards Oshima, and the aircraft entered an initial right-hand bank of 40°, several degrees greater than observed previously. Captain Takahama, alarmed, ordered First Officer Sasaki to bank the aircraft back ("Don't bank so much."). When the aircraft did not respond to the control wheel being turned left, he expressed confusion, after which the flight engineer reported that the hydraulic pressure was dropping. The Captain repeated the order to reduce the bank, as the autopilot had disengaged. He then ordered the copilot to bank it back, then ordered him to pull up. All of these maneuvers produced no response. It was at this point that the pilots realized that the aircraft had become uncontrollable, and Captain Takahama ordered the copilot to descend.

Due to the apparent loss of control, the aircraft did not follow Tokyo Control's directions and only turned right far enough to fly a north-westerly course. Seeing that the aircraft was still flying west away from Haneda, Tokyo Control contacted the aircraft again. After confirming that the pilots were declaring an emergency, the controller requested as to the nature of the emergency. At this point, hypoxia appears to have begun setting in, as the pilots did not respond. In addition, the Captain and Co-pilot asked the Flight Engineer repeatedly if hydraulic pressure was lost (Flight Engineer: "Hydro pressure all loss." Co-pilot: "All loss?" Captain: "No, look." Flight Engineer: "All loss." Co-pilot: "All loss?" Flight Engineer: "Yes."), seemingly unable to comprehend it. Tokyo Control then contacted the aircraft again and repeated the direction to descend and turn to a 90° heading to Oshima. Only then did the captain report that the aircraft had become uncontrollable. (Tokyo: "Japan Air 124 fly heading 090 radar vector to Oshima." JAL123: "But now uncontrol." Tokyo: "Uncontrol, roger understood.")

Heading over the Izu Peninsula at 6:26 p.m., the aircraft turned away from the Pacific Ocean, and back towards the shore; at 6:31:02 p.m., Tokyo Control asked the crew if they could descend, and Captain Takahama replied that they were now descending, and stated that the aircraft's altitude was 24,000 feet after Tokyo Control requested their altitude. Captain Takahama also declined Tokyo Control's suggestion to divert to Nagoya Airport 72 miles away, instead preferring to land at Haneda. However, the flight data recorder shows that the flight did not descend, but was instead rising and falling uncontrollably. Hydraulic fluid completely drained away through the rupture. With total loss of hydraulic control and non-functional control surfaces, the aircraft began up and down oscillations in phugoid cycles lasting about 90 seconds each. The loss of the vertical stabilizer and the rudder removed the only means to dampen yaw, and the aircraft lost virtually all meaningful yaw stability. Almost immediately after separation of the stabilizer, the aircraft began to exhibit Dutch roll, simultaneously yawing right and banking right, before yawing back left and banking left. At some points during the flight, the banking motion became very profound, with the banks in large arcs of approximately 50° back and forth in cycles of 12 seconds.

In spite of the complete loss of controls, the pilots continued to turn the control wheel, pull on the control column, and move the rudder pedals up until the moment of the crash. The pilots also began efforts to establish control using engine thrust, as the aircraft slowly wandered back towards Haneda. Their efforts were of limited success. The unpressurized aircraft rose and fell in an altitude range of 20,000–24,000 feet (6,100–7,300 m) for 18 minutes, from the moment of decompression up until approximately 6:40 p.m., with the pilots seemingly unable to figure out how to descend without flight controls. This is possibly due to the effects of hypoxia at such altitudes, as the pilots seemed to have difficulty comprehending their situation as the aircraft pitched and rolled uncontrollably. It is also possible that the pilots were focused on the cause of the explosion they heard, and the subsequent difficulty in controlling the jet. The flight engineer did say they should put on their oxygen masks when word reached the cockpit that the rear-most passenger masks had stopped working. However, none of the pilots did put on their oxygen masks, even though the Captain simply replied "yes" to both suggestions by the flight engineer to do so. The accident report indicates that the Captain's disregard of the suggestion is one of several features "regarded as hypoxia-related in [the] CVR record[ing]." Their voices can be heard relatively clearly on the cockpit area microphone for the entire duration up until the crash, indicating that they did not do so at any point in the flight.

Shortly before 6:34 p.m., Japan Air Tokyo attempted to call the flight via the selective-calling system multiple times. At 6:35, the flight responded, with the flight engineer handling communications to the company. The company stated that they have been monitoring the emergency, and the flight engineer, having been notified by a flight attendant that the R-5 masks had stopped working, replied back that they believed the R-5 door was broken and were making an emergency descent. Japan Air Tokyo asked if it was their intention to return to Haneda, to which the flight engineer responded that they were making an emergency descent, and to continue to monitor them.

Eventually, the pilots were able to achieve limited control of the aircraft by adjusting engine thrust, and in doing so, they were able to dampen the phugoid cycle and somewhat stabilize their altitude. Suppressing the Dutch roll was another matter, as the engines cannot respond fast enough to counter the Dutch roll. According to the accident report, "Suppressing of Dutch roll mode by use of the differential thrust between the right and left engines is estimated practically impossible for a pilot." Shortly after 6:40 p.m., the landing gear was lowered in an attempt to dampen the phugoid cycles and Dutch rolls further, and to attempt to decrease the aircraft's airspeed in order to descend. This was somewhat successful, as the phugoid cycles were dampened almost completely, and the Dutch roll was damped significantly, but lowering the gear also decreased the directional control the pilots were getting by applying power to one side of the aircraft, and the aircrew's ability to control the aircraft deteriorated.

Shortly after lowering the gear, the flight engineer asked if the speed brakes should be lowered, (“Shall I lower the speed brakes?”) but the pilots didn’t acknowledge the request. Then the aircraft began a right-hand descending 420° turn from a heading of 040° at 6:40 p.m. to a heading of 100° at 6:45 p.m. over Otsuki, due to a thrust imbalance created from having the power setting on Engine 1 (the left-most engine) higher than the other three engines. The aircraft also began descending from 22,400 feet (6,800 m) to 17,000 feet (5,200 m), as the pilots had reduced engine thrust to near idle from 6:43 p.m. to 6:48 p.m. Upon descending to 13,500 feet (4,100 m) at 6:45:46 p.m., the pilots again reported an uncontrollable aircraft. At this time, the aircraft began to turn slowly to the left, while continuing to descend. The thicker air allowed the pilots more oxygen, and their hypoxia appeared to have somewhat subsided, as they were communicating more frequently. The pilots also appeared to be understanding how grave their situation had become, with Captain Takahama exclaiming "This may be hopeless." at 6:46:33. At 6:47 p.m., the pilots recognized that they were beginning to turn towards the mountains, and despite efforts by the crew to get the aircraft to continue to turn right, it instead turned left, flying directly towards the mountainous terrain on a westerly heading.

As the aircraft continued west, it descended below 7,000 feet (2,100 m), and was getting dangerously close to the mountains. The lower altitude and thicker air allowed the Cabin Altitude alert to turn itself off at a couple of points at this time, before resuming for the rest of the flight. The captain briefly ordered maximum engine power to attempt to get the aircraft to climb to avoid the mountains, and engine power was added abruptly at 6:48 p.m. before being reduced back to near idle, then at 6:49 p.m. it was ordered raised again. This greatly excited the phugoid motion, and the aircraft pitched up, before pitching back down after power was reduced. When power was added again, the aircraft rapidly pitched up to 40° at 6:49:30 p.m., briefly stalling at 8,000 feet (2,400 m). The captain immediately ordered maximum power at 6:49:40 p.m. as the stick shaker sounded ("Ah, no good... Stall. Max power. Max power. Max power."). The aircraft's airspeed increased as it was brought into an unsteady climb. Possibly as a measure to prevent a recurrence of stalling, due to the lowered air speed caused by the drag of the landing gear, the crew quickly discussed lowering the flaps. Without hydraulics, the captain expressed that this wouldn't work, but the flight engineer pointed out this could be done via an alternate electrical system. At 6:51 p.m., the Captain lowered the flaps 5 units as an additional attempt to exert control over the stricken jet. During the period from 6:49:03 - 6:52:11, Japan Air Tokyo attempted to call the aircraft via the selective-calling radio system. During the entire three-minute period, the SELCAL alarm continued to ring according to the CVR recordings, the pilots most likely ignoring it due to the difficulty they were experiencing at the time.

The aircraft reached 13,000 feet (4,000 m) at 6:53 p.m., at which point the captain reported an uncontrollable aircraft for the third time. Shortly afterwards, the controller asked the crew to switch the radio frequency to 119.7 to talk to the Tokyo Approach (“Japan Air 123, switch the frequency to 119.7 please!”), and while the pilots did not acknowledge the request over the radio, they did as instructed (Captain: “Yes, Yes, 119.7” Co-pilot: “Ah, Yes, number 2” Captain: “119.7” Co-pilot: “Yes” Flight Engineer: “Shall we try?” Co-pilot: “Yes”). Tokyo Approach then contacted the flight via the SELCAL system, briefly activating the SELCAL alarm again until the flight engineer responded to Tokyo’s request. At this point, the captain asked the flight engineer to request their position (Captain: “Request position” Flight Engineer: “Request position”). At 6:54 p.m., this was reported to the flight as 45 miles northwest of Haneda, and 25 miles west of Kumagaya. At 6:55 p.m. the captain requested flap extension, and the co-pilot called out a flap extension to 10 units, while the flaps were already being extended from 5 units at 6:54:30. This began to cause the aircraft to begin to bank to the right, possibly due to an imbalance in lift between the left and right flaps. Power was increased at the same time. However, a differential thrust setting caused engine power on the left side to be slightly higher than the right-side. This contributed to further increasing the bank angle to the right.

One minute later, the flaps were extended to 25 units, which caused the aircraft to bank dramatically to the right beyond 60°, and the nose began to drop.Captain Takahama immediately ordered the flaps to be retracted ("Hey, halt the flap"), and power was added abruptly but still with engine power higher on the left vs. the right engines. The captain was heard on the cockpit voice recorder desperately requesting for the flaps to be retracted and for more power to be applied in a last-ditch effort to raise the nose (Captain: “Power! Flap stop crowding together.” Co-pilot: “Flap up, flap up, flap up, flap up!” Captain: “Flap up?” Co-pilot: “Yes.” Captain: “Power. Power! Flap!” Flight engineer: “It is up!” Captain: "Raise the nose. Raise the nose! Power!"). The aircraft continued to enter an unrecoverable right-hand descent into the mountains as the engines were pushed to full power, during which the Ground Proximity Warning System sounded, and the captain knew it was too late to recover (Captain: “We can not do anything now!”). In the final moments, as the airspeed exceeded 340 knots (390 mph), the pitch attitude leveled out and the aircraft ceased descending, with the aircraft and passengers/crew being subjected to 3Gs of upward vertical acceleration.

However, the aircraft was still in a 40° right-hand bank when the right-most #4 engine impacted into the trees on top of a ridge located 1.4 kilometres (0.87 mi) NNW of Mount Mikuni at an elevation of 1,530 metres (5,020 ft), which can be heard on the CVR recording. The backward shock of the impact, measuring 0.14G, in addition to losing the thrust of the 4th engine, caused the aircraft to bank sharply back to the right, and the nose to drop again. The aircraft continued on its trajectory for three seconds, upon which the right wing clipped another ridge containing a "U-shaped ditch" 520 metres (1,710 ft) WNW of the previous ridge at an elevation of 1,610 metres (5,280 ft). This impact is speculated to have separated the remainder of the weakened tail from the airframe, as well as the remaining three engines, which were "dispersed 500-700 meters ahead"; after which the aircraft flipped on its back, impacted upon, and exploded on another ridge 570 metres (1,870 ft) NW from the second ridge, near Mount Takamagahara, at 6:56 p.m. The impact registered on a seismometer located in the Shin-etsu Earthquake Observatory at Tokyo University from 6:56:27 as a small shock, to 6:56:32 as a larger shock, estimated to have been caused by the final crash. It is estimated that the shockwaves took approximately 2.0-2.3 seconds to reach the seismometer, making the estimated time of the final crash to be at 6:56:30 pm.