The following information provides an awareness of problems that might be avoided in the future. The information is based on final reports by official investigative authorities on aircraft accidents and incidents.
Autothrottles Remained Engaged
Boeing 737-700. No damage. No injuries.
The captain had received no appreciable sleep the night before he reported for duty at Calgary, Alberta, Canada, the morning of Jan. 9, 2012, for an unscheduled flight to pick up passengers in Edmonton, Alberta, and in Fort St. John, British Columbia, and to transport them to Fort Nelson, British Columbia, said the report by the Transportation Safety Board of Canada.
There were 112 passengers and six crewmembers aboard when the aircraft departed from Fort St. John for the last leg to Fort Nelson, which was reporting visual meteorological conditions with calm winds. The flight crew planned to conduct a visual approach, backed up by the instrument landing system (ILS), to Runway 03 with a reference landing speed (VREF) of 128 kt.
The 737 was nearing the airport when a flight service specialist advised the crew that winds were from 240 degrees at 5 kt and that there were some patches of ice and frost on the 6,402-ft (1,951-m) runway.
The autopilot captured the localizer course about 5 nm (9 km) from the runway, with the glideslope mode engaged, but the captain then selected the vertical speed mode and a descent rate of 500 fpm. The enhanced ground proximity warning system (EGPWS) generated two warnings that the aircraft was below the glideslope. “The captain advised the first officer that he was correcting and then queried the first officer as to his comfort level with this warning,” the report said. “The first officer acknowledged that it would be okay to continue.”
The captain was hand flying the aircraft, with the autothrottles engaged, when it briefly intercepted the glideslope about 420 ft above the ground. The 737 then drifted above the glideslope. “In response, the captain pitched the nose down, and the aircraft’s speed increased to 142 kt,” the report said.
The captain did not disengage the autothrottles at 50 ft, as required by standard operating procedures. As a result, when he attempted to deploy the thrust reversers after the aircraft touched down 1,800 ft (549 m) from the approach threshold, the autothrottles commanded increased thrust to maintain the previously selected airspeed of 133 kt. This also prevented speed brake extension.
The captain brought the thrust levers to idle and disengaged the autothrottles. “Deceleration began about 5 seconds after touchdown, with approximately 2,500 feet [762 m] of runway remaining,” the report said.
The crew was applying full manual braking and reverse thrust when the 737 ran off the end of the runway at 10-15 kt and came to a stop on frozen soil and in deep snow 230 ft (70 m) from the threshold.
The report said that “fatigue-induced reduction in forward planning and a focus of attention towards salvaging the flight” were factors in the accident. The captain had been off duty for 14 days but had received “little to no sleep” in his “noisy and warm” apartment during the 24 hours prior to the flight.
“The captain [had] considered calling in sick but, due to the time off, felt it would not be viewed in a favorable light,” the report said. It noted, however, that “there were no indications that the culture [at the company] was punitive towards crew calling in sick for fatigue.”
Worn Seal Causes Windshield Cracks
Airbus A320-211. Minor damage. No injuries.
The A320 was cruising at Flight Level 340 (approximately 34,000 ft), en route from Toronto to Los Angeles the morning of Sept. 17, 2011, when the first officer’s windshield cracked. “The crack subsequently progressed into multiple multidirectional cracks that obscured the first officer’s view through the window,” said the report by the U.S. National Transportation Safety Board (NTSB).
Unable to determine the severity of the cracks or how many windshield plies were affected, the flight crew declared an emergency and landed the airplane without further incident at Chicago O’Hare International Airport.
Investigators found that the crack began at the center of the windshield and was initiated by electrical arcing in the interlayer at a bus bar near the lower edge of the windshield. “This location coincided with the area in which the power and sensing element wires were routed around the structural glass plies,” the report said. “The area of arcing was surrounded by a cloudy and degraded interlayer, which was consistent with the presence of moisture. A section of the moisture seal was worn and appeared to have been repaired.”
The report noted that the manufacturer, PPG Industries, subsequently modified the windshield to “reduce the potential for moisture ingress and its subsequent effects on the electrical system.”
Skid Off a Wet Taxiway
Boeing 737-300. Substantial damage. No injuries.
Surface winds were from 010 degrees at 6 kt, and Runway 33 was in use at Birmingham (England) International Airport the afternoon of Sept. 21, 2012. The flight crew planned to exit the runway on Taxiway Bravo, which was about three-quarters of the way down the 2,599-m (8,527-ft) runway.
After the 737 touched down at the planned airspeed and in the touchdown zone of the wet runway, the commander (the pilot flying) found that deceleration was insufficient to exit on Taxiway Bravo without excessive braking. “He then cancelled thrust reverse, released the brakes and let the aircraft roll to the end of the runway to vacate at Taxiway Alpha,” said the report by the U.K. Air Accidents Investigation Branch (AAIB).
During the roll-out, the commander heard the airport tower controller tell the crew of a following aircraft to “expect late landing clearance; previous lander had gone all the way to the end.”
Investigators found that the 737’s groundspeed was about 20 kt when the commander began the turn onto Taxiway Alpha, which is not a high-speed taxiway. “The commander was attempting to vacate the runway expeditiously to avoid causing the following aircraft to go around” when the 737 skidded off the side of the taxiway and came to a stop in the grass, damaging the nose landing gear, the report said. The pilots shut down the engines, and the 143 occupants exited the aircraft.
Regarding the estimated 20-kt runway-exit speed, the report said, “The operator’s operations manual stated that a groundspeed of approximately 10 kt should be used for making a turn from a runway onto a non-high-speed taxiway in the dry. As the runway and taxiway were wet, a lower speed would have been appropriate.”
AP Disconnect Triggers Upset
Bombardier Challenger 300. Minor damage. One serious injury, three minor injuries.
The Challenger, based in Finland, departed with three passengers and three crewmembers from Moscow’s Sheremetyevo Airport for a business flight to St. Petersburg the evening of Dec. 23, 2010. The flight also was to serve as part of the copilot’s familiarization training, said the English translation of the report by the Safety Investigation Authority of Finland.
The copilot was the pilot flying on takeoff, but the captain assumed control when the engine indicating and crew alerting system displayed a warning of an autopilot stabilizer trim failure immediately after the autopilot was engaged during initial climb. “During the climb, they also received several cautions regarding the fact that the autopilot had to keep commanding nose-down elevator inputs,” the report said.
The Challenger was climbing through 12,700 ft at 281 kt when the captain, in accordance with the checklist procedure, took a firm grip on the control column and disengaged the autopilot. “As a result of the forces in the flight control system, the control column moved backwards, to which the captain reacted by pushing the nose down,” the report said. “This led to an approximately 7-second-long porpoising oscillation, which the captain managed to bring under control.”
The passengers did not have their seat belts fastened and were thrown upward during the upset, which involved vertical accelerations from +3.6 g to –1.7 g. Two of the passengers sustained minor injuries when they fell back onto their seats and armrests. The other passenger struck the cabin ceiling and sustained broken ribs upon falling back onto the seat. “The service hostess, standing at the doorway of the flight deck, fell and suffered bruises on her shoulders and arms,” the report said. “The flight crew did not sustain any injuries.”
After the upset, the flight crew turned back to Sheremetyevo Airport and requested that an ambulance meet the aircraft at the apron. The aircraft was landed without further incident.
The report said that the Challenger’s relatively high airspeed had contributed to the substantial acceleration forces during the upset. “Whereas the aircraft’s checklists advise the pilots to firmly grip the control column prior to AP [autopilot] disengagement, they do not instruct the flight crew to consider adjusting the airspeed to correspond to the horizontal stabilizer angle,” the report said. “Neither did the checklists include any mention of turning on the ‘Fasten Seat Belt’ sign.”
Loading Cited in Control Loss
Cessna 208B. Destroyed. Two fatalities.
The Caravan departed from Wamena, Papua, Indonesia, for an unscheduled cargo flight under visual flight rules to Kenyam the afternoon of Sept. 9, 2011. “On board the aircraft were two pilots, a manifested load of diesel drums and grocery items, and a non-manifested load of 25 bags of rice weighing 827 lb (375 kg),” said the report by the Indonesian National Transportation Safety Committee (NTSC).
After the crew reported that they were passing through 7,300 ft on a climb to 9,500 ft, there were no further radio communications with air traffic control (ATC). The report noted that because of high terrain along the route, the operator had specified a minimum altitude of 11,500 ft between Wamena and Kenyam.
The wreckage of the Caravan was found two days later on the side of a mountain near Yahukimo. Investigators found that several EGPWS warnings had been generated as the aircraft descended from 9,840 ft in a left turn, with descent rates reaching 4,400 fpm. The aircraft struck terrain at 9,194 ft.
Based on the findings of the investigation, the NTSC concluded that the pilot flying had lost control of the aircraft while maneuvering to avoid terrain or during an inadvertent encounter with instrument meteorological conditions (IMC).
The report said that a contributing factor in the accident was the adverse effect on the aircraft’s performance by its loading, which was 619 lb (281 kg) above the maximum takeoff weight and with a center of gravity aft of the aft limit.
Distraction Leads to Altitude Bust
Beech King Air B200. No damage. No injuries.
The medevac flight crew was transporting a pregnant woman, a paramedic and a medical escort from Glasgow, Scotland, to Wick the night of Sept. 15, 2012. The copilot, a new-hire who was making his first flight in the aircraft, was the pilot flying. The commander also was somewhat unfamiliar with the aircraft, which had different instrumentation than the other B200s he was used to flying, according to the AAIB report.
Nearing Wick Airport in IMC, the crew received radar vectors from ATC for the ILS approach to Runway 23 and was instructed to descend to 3,500 ft. When the copilot reduced power to slow the King Air for the descent, the landing gear warning horn activated.
“The copilot attempted to cancel the warning horn with the ‘GEAR HORN SILENCE’ button, which he thought was located on the left power lever, but accidentally pressed the ‘GO-AROUND’ button instead,” the report said. This resulted in disengagement of the autopilot and deselection of the existing flight director modes.
“The distraction of this, coupled with [the crew’s] lack of experience on this type of B200, caused a short breakdown in crew situational awareness, and the aircraft descended below the cleared altitude,” the report said.
The commander was silencing the gear-warning horn and re-engaging the flight director and autopilot when he noticed that the King Air was descending rapidly below 3,000 ft. He told the copilot to initiate a climb. “The copilot applied full power, rotated the aircraft into a climb attitude and manually flew the aircraft back to 3,500 ft,” the report said.
During the recovery, the EGPWS generated a “TERRAIN, PULL UP” warning. An ATC minimum safe altitude warning (MSAW) also was generated, and the controller alerted the crew about the altitude deviation. After climbing back to 3,500 ft, the pilots completed the ILS approach and landed the King Air without further incident.
Tree Struck During Go-Around
De Havilland DHC-3T. Substantial damage. One fatality, one serious injury, one minor injury.
The Otter, which was equipped with amphibious floats and had been modified with a turboprop engine, was on an air taxi flight from Old Harbor, Alaska, U.S., to Kodiak the evening of Sept. 23, 2011, when the pilot decided to make an unscheduled landing on a lake near Kodiak.
The airplane was near touchdown when the pilot initiated a go-around and flew low over the lake toward a creek flanked by steep hills, the NTSB report said. A passenger recalled that the left wing struck a tree, and the pilot initiated a steep climbing right turn. The Otter began to shake, and the stall-warning horn sounded before the airplane entered a steep descent and struck terrain in a nose-down attitude.
The pilot was killed in the crash. “Toxicological tests detected the pilot’s recent use of over-the-counter medications for relief of cold and flu symptoms,” the report said, noting that one of the medications was Doxylamine, a sedating antihistamine. “This medication carries the warning that it may impair mental and/or physical ability required for the performance of potentially hazardous tasks.”
Pilot Attributes LOC to Stress
Cessna 421B. Substantial damage. Two serious injuries.
The pilot, who had logged about 900 of his 3,800 flight hours in 421s, said that he conducted a “reduced power” takeoff, with power set at about 80 percent, which resulted in a longer-than-normal takeoff roll at Spinks Airport in Fort Worth, Texas, U.S., the morning of Sept. 5, 2012.
Shortly after liftoff, the unlatched nose baggage door opened. “The pilot said he then turned around and told the passenger that the cargo door had popped up and they had to return and land,” the NTSB report said. The pilot then advised ATC of his intentions.
The 421 was about 200 ft above the ground when it stalled, descended into trees, struck the ground hard, flipped over and caught fire. The pilot and passenger sustained serious injuries but were able to exit the airplane through the main door.
“The pilot said there were no mechanical problems with the airplane and that he was fixated on the unlatched nose cargo door and lost control of the airplane,” the report said. “He said he was dealing with a lot of stress in his personal life and was not prepared to handle the emergency situation.”
Spalled Tappets Destroy Engine
Gippsland GA-8 Airvan. Substantial damage. No injuries.
The pilot was conducting a scenic charter flight with six passengers near Marree, South Australia, the afternoon of Sept. 29, 2011. The single-engine aircraft was about 500 ft above the ground, nearing Lake Eyre, when the pilot felt the airframe shudder and heard a loud pop. The propeller then stopped rotating, and the pilot landed the Airvan on a dirt road.
“The pilot and passengers were not injured, and the aircraft sustained no damage as a result of the forced landing,” the Australian Transport Safety Bureau report said. Initial examination of the Textron Lycoming IO-540K engine revealed large cracks in the crankcase and a pool of oil in the lower cowling.
Further examination disclosed substantial internal mechanical damage in the vicinity of the no. 5 and no. 6 cylinders. “The no. 5 piston had separated from its connecting rod and was fractured in several places around the piston skirt and the piston pin bore,” the report said. The damage was traced to metal contamination from two spalled valve tappets.
The report noted that the engine manufacturer had introduced improved tappets for installation during scheduled overhauls at 2,000 hours. The accident aircraft’s engine had accumulated about 1,720 hours and had not been modified.
Oil consumption had been higher than the manufacturer’s specification but had been attributed by maintenance personnel as a normal symptom of engine wear. “Had further investigation been carried out prior to the [accident] flight, it was likely that metal contamination from the spalling tappets would have been evident in the oil filter,” the report said.
Flight Control CBs Tripped
Sikorsky S-76C. Minor damage. No injuries.
The S-76C was en route from Humberside, England, to transport eight passengers to an offshore platform the morning of Sept. 26, 2012, when it pitched nose-up and rolled right. The commander disengaged the autopilot, but the helicopter continued yawing in a “fishtailing” motion, the AAIB report said.
The pilots also detected a strong odor of smoke. They declared an urgency and landed without further incident at a nearby private airfield. After landing, the crew found that the circuit breakers for the no. 2 cyclic control system and collective control system had tripped.
“An engineering investigation established that the electrical shorting had occurred in a wiring loom situated above the forward left cabin area,” the report said. Sikorsky Aircraft determined that the wiring loom likely had been “disturbed” during installation of optional equipment.
“However, the manufacturer also recognizes that [the wiring in] the area is potentially susceptible to chafing and is currently studying several methods [to] reduce this susceptibility,” the report said.
Simulated Engine Failure Gets Real
Hughes 269A. Substantial damage. No injuries.
A flight instructor and a student pilot departed from Lincoln, Nebraska, U.S., for an instructional flight the afternoon of Sept. 19, 2012. The purpose of the flight was to prepare the student for an upcoming check ride.
The 269 was about 400 ft above the ground with an airspeed of 50 kt when the instructor reduced power to idle to simulate an engine failure. When the student lowered the collective to initiate autorotation, an actual loss of power occurred. The helicopter descended rapidly and landed hard. The rotor blades severed the tail boom, and the helicopter rolled over on its side.
Investigators found that debris in the engine air filter was obstructing airflow through the filter by about 80 percent. A ground run of the engine showed an excessively rich mixture due to the reduced airflow. “It is likely that the student lowered the collective too quickly, which, combined with the obstructed air filter, created a rich fuel mixture and loss of engine power,” the NTSB report said.