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.
Jets
Pump Seal Damaged
Boeing 757-200. Minor damage. No injuries.
The incorrect installation of a seal in the coupling between a fuel tube and the high-pressure fuel pump on the 757’s right engine likely caused a significant fuel leak during a chartered flight from Helsinki, Finland, to Las Palmas in Spain’s Canary Islands the afternoon of Jan. 15, 2011. The flight crew diverted the flight toward Paris.
In a recently released English translation of the final report on the serious incident, the Safety Investigation Authority of Finland said that the crew did not shut down the engine, as prescribed by the quick reference handbook (QRH), during the diversion.
“The pilots’ deviation from QRH instructions caused the maximum allowable fuel imbalance to be exceeded as the fuel leak continued, which led to operations outside the approved performance envelope, and the incident developed into a serious incident according to ICAO [International Civil Aviation Organization] classification,” the report said.
Despite the excessive fuel imbalance, the crew was able to land the 757 without further incident in Paris. There were 210 passengers and eight crewmembers aboard the aircraft.
The pilots discovered the leak about two hours after departing from Helsinki. During an apparent routine hourly fuel check, they noticed that fuel consumption was significantly higher than calculated. “On closer examination, the pilots concluded that there was a fuel leak and traced it to the right fuel system or engine,” the report said. “The fuel leak was so large that the captain decided to land at the nearby Paris Charles de Gaulle airport.”
Investigators later calculated that, due to the leak, fuel consumption from the right fuel system was about 63 kg (139 lb) per minute higher than the left fuel system. The crew did not declare an emergency, but air traffic control (ATC) handled the flight as an emergency after the pilots explained the reason for the diversion.
Although the QRH required a shutdown, “the captain decided not to shut down the right engine until during the ground run since the right engine was running well and he considered it safer to fly with two live engines under these circumstances rather than with one engine,” the report said.
Other factors in the captain’s decision to leave the right engine running were the absence of any sign of a fire and the need to reduce the fuel load to lighten the 757’s landing weight. Moreover, the captain apparently did not trust the left engine. “According to the captain, there had been vibration in the left engine during the flight,” the report said. “Vibration had also occurred on previous flights [and was not corrected by maintenance performed before the aircraft departed from Helsinki].”
The aircraft was landed with a fuel imbalance of 1,700 kg (3,748 lb), or 815 kg (1,797 lb) above the prescribed maximum. “Reverse thrust was not used during the ground run, as the pilots estimated that it might suck any leaking fuel into the hot section of the engine,” the report said. “The captain shut down the right engine on the runway.”
Investigators found that the maintenance performed immediately before the flight included replacement of the right engine’s accessory gearbox, on which the high-pressure fuel pump is installed. Their post-flight examination of the engine revealed that the O-ring seal in the coupling was deformed and partially unseated.
“The most probable cause leading to the fuel leak … is that the fitting of the seal was originally too tight, for which reason the seal may have been pressed incorrectly against the edge of the groove when it was installed during maintenance before the incident flight,” the report said.
Corrosion Triggers Shaft Failure
McDonnell Douglas MD-10-30F. Substantial damage. No injuries.
The freighter was accelerating through 60 kt on takeoff from Portland (Oregon, U.S.) International Airport the afternoon of Feb. 13, 2012, when the flight crew heard sounds similar to a compressor stall, felt abnormal vibrations and saw the left engine’s exhaust gas temperature increase.
The crew rejected the takeoff and taxied the MD-10 back to the gate. The U.S. National Transportation Safety Board (NTSB) report said that disassembly of the left engine showed that the aft end of the midshaft that connects the fan with the low-pressure turbine had fractured.
Further examination revealed that synthetic oil had entered a cavity between the midshaft and the center vent tube. The oil deteriorated and caused corrosion pitting and the eventual failure of the shaft. “The exact source or mechanism by which the oil entered the dry cavity between the fan midshaft and the center vent tube is unknown,” the report said.
Smoke Traced to Cooling Fan
Boeing 777-200. Minor damage. No injuries.
The 777 was 38,000 ft over the North Atlantic and about four hours into a flight from Philadelphia to London with 174 passengers and 13 crewmembers the night of Dec. 1, 2012, when the pilots detected smoke on the flight deck. The commander said that the smoke became “quite bad,” so he declared an emergency, initiated a descent to 15,000 ft and diverted the flight to Shannon (Ireland) Airport.
“During the descent, the flight crew carried out the smoke checklist in accordance with the QRH, and the smoke cleared,” said the report by the Air Accident Investigation Unit of Ireland. “They reported that they received a status message to the effect that the right-hand equipment cooling fan had failed.”
The crew changed their flight condition from an emergency to an urgency but, because of the increased fuel consumption at 15,000 ft, continued to Shannon, where the aircraft was landed without further incident.
Examination of the cooling fan revealed that a bearing race had collapsed, resulting in contact and overheating of internal rotating and stationary parts. The report said that this is a common failure mode for rotary fans and that the operator of the 777 was experiencing about one equipment cooling fan failure per year. “However, the subject event was the second such failure in two months and the second related diversion since 2008.”
Excursion on Snowy Runway
Learjet 35. Substantial damage. No injuries.
As the pilots taxied the Learjet for a departure with eight passengers from Pueblo (Colorado, U.S.) Memorial Airport the evening of Feb. 2, 2012, the automatic terminal information system reported winds from 360 degrees at 15 kt and 3/4 mi (1 1/4 km) visibility in snow.
The NTSB report said that the captain chose to take off with a crosswind from Runway 08R because, at 10,498 ft (3,200 m), it was longer than Runway 35 (8,310 ft [2,533 m]).
While taxiing to Runway 08R, the captain estimated the snow depth on the taxiways was about 1/8 in (3/8 cm). “The control tower reported that they had no current runway-condition reports since there were no recent landings or departures,” the report said. “The captain said the snow on the runway seemed to be no heavier than what he observed on the taxiway, and he could see the end stripes on the runway.”
The captain recalled that the takeoff initially was normal. However, as the airplane neared V1, or about 120 kt, he felt it “lurch” right. “He immediately applied full left rudder [and] full left aileron and reduced power, but the airplane continued off the right side of the runway,” the report said. “The airplane traveled across several taxiways before coming to rest upright south of the runway on the grass.”
Both main landing gear separated, and the nose gear and the right wing were substantially damaged, but there was no fire.
NTSB concluded that the probable cause of the accident was “the captain’s failure to maintain airplane control during an attempted crosswind takeoff on a contaminated runway.”
Fall From a Service Door
Embraer 145LR. No damage. One serious injury.
Surface winds were at 25 kt, gusting to 35 kt, as the airplane was being prepared for departure from Cincinnati, Ohio, U.S., the afternoon of Feb. 19, 2013. A flight attendant was opening the galley door for a service crew when a gust dislodged papers inside the galley.
“As she attempted to retrieve them, the wind blew her out the door,” the NTSB report said. “The safety strap had not been attached at the time of the event. The flight attendant experienced a serious injury to her vertebrae.”
Turboprops
Inexplicable Engine Shutdown
Cessna 425. Substantial damage. No injuries.
The flight crew said that the left engine’s interstage turbine temperature rapidly increased and torque decreased to zero during a medevac positioning flight from Hanover, Germany, to Munich the night of Feb. 2, 2010. The crew requested and received clearance from ATC to descend from 23,000 ft to 15,000 ft.
“The crew could not state which actions they had carried out after the descent clearance and during shut-off and securing of the left engine,” said the report by the German Federal Bureau of Aircraft Accident Investigation. The investigation revealed that they had not feathered the propeller.
Radar data indicated that groundspeed varied from 210 kt to 80 kt as the pilots conducted the instrument landing system (ILS) approach to Munich’s Runway 26L in instrument meteorological conditions that included 1,800 m (1 1/8 mi) visibility in snow. Airspeed was below the prescribed minimum single-engine approach speed when the 425 descended below the glideslope about 3 nm (6 km) from the runway.
The crew increased power from the right engine, and the aircraft veered left and struck snow-covered terrain about 100 m (328 ft) from the runway threshold and 60 m (197 ft) left of the extended centerline.
Examination of the left engine revealed no anomalies. Noting that the crew could not recall any other power plant parameters, the report said that their reason for shutting down the left engine could not be clarified. “Since the investigation did not reveal any mechanical engine damage, it is highly likely that the engine was generally capable of producing power.”
‘I’ve Got It. Don’t Worry’
ATR 42-300. No damage. No injuries.
The pilots had been on duty about 9 1/2 hours and were conducting the last of three cargo flights the morning of Feb. 22, 2012, when the stall-warning horn sounded and the stick shaker activated during an ILS approach to Glasgow, Scotland.
“Simultaneously, the autopilot disconnected,” said the report by the U.K. Air Accidents Investigation Branch (AAIB). “The copilot called, ‘Fly the aircraft [expletive].’” The commander almost immediately pitched the aircraft nose-down to –10 degrees and advanced the power levers [from about 20 percent torque] almost to full power, saying as he did so, “I’ve got it. I’ve got it. Don’t worry.”
As airspeed increased to 125 kt, the commander leveled the aircraft but did not reduce the torque setting of 98 percent. The overspeed warning activated as the approach flaps limit of 170 kt was exceeded. The commander then reduced power to slightly above flight idle. The copilot suggested that the autopilot be re-engaged, and the commander replied, “Shhh, just steady on.”
The ATR was descending through 1,500 ft on the glideslope when angle-of-attack reached 10.5 degrees, just below the stick-shaker threshold. “The flight crew attempted to re-engage the autopilot, but it disconnected immediately,” the report said. “Simultaneously, engine torque was increased to 45 percent, airspeed increased and the angle-of-attack reduced.”
The crew had not established radio communication with the tower controller, as previously instructed. When queried by the approach controller, the copilot replied, “Stand by. We’ve just got … a few problems.” The copilot then advised that the problem had been resolved and that they would switch to the tower frequency.
The remainder of the approach was uneventful until a nacelle-overheat warning activated on touchdown. “The flight crew did not action the associated procedure,” the report said. They taxied the ATR to the gate and shut it down. The copilot later reported the incident to the company.
The AAIB concluded that the crew’s performance during the approach “may have been affected by tiredness or fatigue” and demonstrated a lack of adherence with standard operating procedures, ineffective monitoring and diminished cooperation.
Nosewheel Steering Malfunctions
Fairchild SA227. Substantial damage. No injuries.
The Metroliner veered right after touching down about halfway down the 5,800-ft (1,768-m) runway at Somerset, Kentucky, U.S., the afternoon of Jan. 2, 2010. “The pilot applied full left rudder and full reverse on the left power lever but was unsuccessful in correcting the alignment of the airplane,” the NTSB report said.
“He then engaged the nosewheel steering button on the left power lever, and the airplane began a more aggressive turn to the right. It departed the runway, traveled down an embankment and came to rest against the airport boundary fence.” The right wing and both propellers were damaged by rocks, but the pilots and their passenger were not hurt.
The Metroliner was repaired and returned to service, but an intermittent loss of steering subsequently was encountered. The problem was traced to damaged wires in the nosewheel steering harness.
“Although an electrical anomaly contributed to the [Jan. 2] loss of control, the fact that the pilots landed long and potentially with excess speed resulted in less runway and time available to recover from the anomaly,” the report said.
Piston Airplanes
Stall on Missed Approach
Cessna 414A. Substantial damage. Two fatalities, four serious injuries.
Weather conditions deteriorated rapidly as the 414 neared the uncontrolled airport in Hayden, Colorado, U.S., the afternoon of Feb. 19, 2012. Visibility decreased to 1/4 mi (400 m), the ceiling was overcast at 400 ft, and surface winds were from 290 degrees at 10 kt, gusting to 14 kt. The NTSB report said that the precipitation type was not reported but that heavy snow was likely.
The pilot conducted the ILS approach to Runway 10. “A review of on-board global positioning system data indicated that the airplane flew through the approach course several times during the approach and was consistently below the glideslope,” the report said.
The airplane was below the published decision height and right of the extended runway centerline when the pilot initiated a missed approach. Groundspeed decreased during the climb, and the 414 stalled and struck terrain. The pilot and one passenger were killed; the other four passengers were seriously injured.
“The airplane’s anti-ice and propeller anti-ice switches were found in the ‘off’ position,” the report said. “It is likely that the airframe collected ice during the descent and approach, which affected the airplane’s performance and led to an aerodynamic stall during the climb.”
Control Lost in Crosswind
Piper Chieftain. Substantial damage. No injuries.
The Chieftain was on a visual flight rules air-taxi flight the evening of Feb. 16, 2013, to Dutch Harbor, Alaska, U.S., which was reporting winds from 339 degrees at 26 kt, gusting to 35 kt, a 1,200-ft overcast and 5 mi (8 km) visibility in blowing snow.
The NTSB report said that the pilot chose to land with a quartering tailwind on Runway 12 and lost control of the Chieftain after touchdown. “During the landing roll, a wind gust pushed the nose of the airplane to the right, and the airplane began to slide momentarily on an icy patch on the runway,” the report said. “While sliding sideways, the left main landing gear contacted bare pavement, which resulted in the collapse of the left main landing gear.”
Damage to the landing gear and wing was substantial, but the pilot and his two passengers escaped injury.
Helicopters
‘Threshold of Control’
Bell 206B3. Substantial damage. Two minor injuries.
The JetRanger was dispatched to film a truck accident on a road in hilly terrain near Perth, Western Australia, the morning of Jan. 19, 2013. Day visual meteorological conditions with northeasterly winds of 10 to 15 kt prevailed at the accident site.
After hovering and maneuvering about 500 ft above the ground for three minutes, the pilot initiated a right turn to complete the filming and depart from the area. “The helicopter was exposed to a crosswind from the left while at an airspeed around the 30-kt threshold value for susceptibility to loss of tail rotor effectiveness,” said the report by the Australian Transport Safety Bureau.
As the right turn began, the nose moved left and then rapidly to the right, and the helicopter began to rotate. “The pilot responded with control inputs and regained sufficient control to carry out a forced landing, but [he] did not apply full left pedal as recommended for loss of tail rotor effectiveness, resulting in a likely delay in recovery,” the report said.
The JetRanger rolled over after touching down in a clear area on sloping terrain. The pilot and the photographer sustained minor injuries and were attended by emergency services personnel at the site.
Engine Fails in Icing Conditions
Hughes 500. Substantial damage. No injuries.
The pilot told investigators that the auto-ignition system was armed when the engine lost power after the helicopter flew through an area of moderate to heavy snow during a flight from Canton, Ohio, U.S., to Dayton the morning of Jan. 29, 2013.
“The pilot entered an autorotation and applied excessive aft cyclic during the touchdown in a field [in London, Ohio], which caused the main rotor blades to flex down and sever the tail boom,” the NTSB report said. The pilot and his passenger escaped injury.
Examination of the engine revealed no mechanical anomalies. The report said that the Hughes 500 rotorcraft flight manual prohibits flight into known icing conditions and requires the fuel to meet the anti-icing capability of JP-4 when operating in temperatures below 41 degrees F (5 degrees C).
Weather conditions in the area included snow and freezing fog, an 800-ft overcast and a surface temperature of 16 degrees F (minus 9 degrees C). “A review of fueling records revealed that no anti-icing additive was added to the fuel,” the report said. “The pilot was aware of the icing conditions, but he continued the flight.