La Alianza, PR, USA
N831BC
FAIRCHILD SA227-AC
The captain and first officer were conducting an international cargo flight in the twin-engine turboprop airplane. After about 40 minutes of flight during night visual meteorological conditions, an air traffic controller cleared the airplane for a descent to 7,000 ft and then another controller further cleared the airplane for a descent to 3,000 ft and told the flight crew to expect an ILS (instrument landing system) approach. During the descent, about 7,300 ft and about 290 kts, the airplane entered a shallow left turn, followed by a 45-degree right turn and a rapid, uncontrolled descent, during which the airplane broke up about 1,500 ft over uneven terrain. The moderately loaded cargo airplane was not equipped with a flight data recorder or cockpit voice recorder (CVR) (although it previously had a CVR in its passenger configuration) nor was it required by Federal Aviation Administration (FAA) regulations. There were also no avionics on board with downloadable or nonvolatile memory. As a result, there was limited information available to determine what led to the uncontrolled descent or what occurred as the flight crew attempted to regain control of the airplane. Also, although the first officer was identified in FAA-recorded radio transmissions several minutes before the loss of control and it was company policy that the pilot not flying make those transmissions, it could not be determined who was at the controls when either the loss of control occurred or when the airplane broke up. There was no evidence of any in-flight mechanical failures that would have resulted in the loss of control, and the airplane was loaded within limits. Evidence of all flight control surfaces was confirmed, and, to the extent possible, flight control continuity was also confirmed. Evidence also indicated that both engines were operating at the time of the accident, and, although one of the four propeller blades from the right propeller was not located after separating from the fractured hub, there was no evidence of any preexisting propeller anomalies. The electrically controlled pitch trim actuator did not exhibit any evidence of runaway pitch, and measurements of the actuator rods indicated that the airplane was trimmed slightly nose low, consistent for the phase of flight. Due to the separation of the wings and tail, the in-flight positions of the manually operated aileron and rudder trim wheels could not be determined. Other similarly documented accidents and incidents generally involved unequal fuel burns, which resulted in wing drops or airplane rolls. In one case, the flight crew intentionally induced an excessive slide slip to balance fuel between the wings, which resulted in an uncontrolled roll. However, in the current investigation, the fuel cross feed valve was found in the closed position, indicating that a fuel imbalance was likely not a concern of the flight crew. In at least two other events, unequal fuel loads also involved autopilots that reached their maximum hold limits, snapped off, and rolled the airplane. Although the airplane in this accident did not have an autopilot, historical examples indicate that a sudden yawing or rolling motion, regardless of the source, could result in a roll, nose tuck, and loss of control. The roll may have been recoverable, and in one documented case, a pilot was able to recover the airplane, but after it lost almost 11,000 ft of altitude. During this accident flight, it was likely that, during the descent, the flight crew did regain control of the airplane to the extent that the flight control surfaces were effective. With darkness and the rapid descent at a relatively low altitude, one or both crewmembers likely pulled hard on the yoke to arrest the downward trajectory, and, in doing so, placed the wings broadside against the force of the relative wind, which resulted in both wings failing upward. As the wings failed, the propellers simultaneously chopped through the fuselage behind the cockpit. At the same time, the horizontal stabilizers were also positioned broadside against the relative wind, and they also failed upward. Evidence also revealed that, at some point, the flight crew lowered the landing gear. Although it could not be determined when they lowered the gear, it could have been in an attempt to slow or regain control of the airplane during the descent. Although reasons for the loss of control could not be definitively determined, the lack of any preexisting mechanical anomalies indicates a likelihood of flight crew involvement. Then, during the recovery attempt, the flight crew's actions, while operating under the difficult circumstances of darkness and rapidly decreasing altitude, resulted in the overstress of the airplane.
HISTORY OF FLIGHTOn December 2, 2013, at 2010 Atlantic standard time, a Fairchild SA227-AC, N831BC, operating as IBC Airways flight 405 ("Chasqui 405"), was destroyed during a rapid descent and subsequent inflight breakup near La Alianza, Puerto Rico. The captain and the first officer were fatally injured. Night visual meteorological conditions prevailed. The international cargo flight was operating on an instrument flight rules flight plan between Las Americas International Airport (MDSD), Santo Domingo, Dominican Republic, and San Juan International Airport (TJSJ), San Juan, Puerto Rico, under the provisions of 14 Code of Federal Regulations Part 135. According to operator records, the accident flight occurred during the return leg of a round trip between TJSJ and MDSD. Prior to the outbound flight, "normal dispatch requirements were met," and the airplane took on fuel at TJSJ for both legs. The airplane departed MDSD on the accident flight at 1936. A review of radio transmission transcripts indicated that the crew first contacted the San Juan Combined En route Approach Control (CERAP) facility at 1948, 13 nautical miles west of "MELLA" intersection at 11,000 feet. At 2001, the crew was told to descend to 7,000 feet at "pilot's discretion," and at 2007, the crew was advised to change frequency to the next CERAP sector controller. The crew subsequently contacted the next controller, "leaving one one thousand, descending to seven thousand." The controller then advised the crew to maintain 3,000 feet, expect the ILS (instrument landing system) approach, proceed direct to the "TNNER" fix, and that information "Tango" was in effect. After a crewmember read back the information at 2007:46, there were no further transmissions from the airplane. At 2011:52, the controller advised that radar contact was lost. According to a Federal Aviation Administration (FAA) inspector interview (the inspector conducted the interview in Spanish and translated it into English), a witness stated that he heard some engine noise, and when he looked outside, he saw the airplane with the right wing down, "turning in a spiral form." He also noticed a red light "spinning." After that, he heard an "impact noise" and 5 seconds later, "another solid impact noise." Radar data revealed that after crossing MELLA, the airplane proceeded toward TJSJ along a heading of about 085 degrees true, crossing the west coast of Puerto Rico just south of the town of Stella. The airplane maintained 11,000 feet until 2007, and had descended to 8,300 feet by 2010:08. The radar track then indicated a 20-degree turn to the left, and a descent to 7,300 feet by 2010:13. The radar track subsequently indicated about a 45-degree turn to the right, and a descent to 5,500 feet by 2010:18. There were no additional verifiable altitude positions. Descent calculations between 2010:08 and 2010:13 indicated a rate of descent of about 12,000 feet per minute (fpm), and between 2010:13 and 2010:18, over 21,000 fpm. Groundspeed calculations indicated a fairly constant average of about 260 knots (provided in 10-knot increments) until the airplane initiated a descent. The last two calculations, 1 minute apart and just prior to the rapid descent, were 280 and 290 knots. PERSONNEL INFORMATIONThe captain, age 35, held a commercial certificate with airplane single-engine land and sea, multiengine land and sea, and instrument-airplane ratings. He also held an airplane single engine flight instructor certificate. His latest FAA first class medical certificate was dated April 16, 2013. According to company records, the captain was assigned a captain's position on June 5, 2013, after completing his FAA proficiency checkride on June 3, 2013, and his line checkride on June 5, 2013. Company records also indicated that as of November 30, 2013, the captain had 1,740 total flight hours, 686 hours in type, 239 hours as pilot-in-command, and 121 hours in the previous 90 days. Night flight hours could not be ascertained. The first officer, age 28, held a commercial pilot certificate, with airplane single- engine land, multiengine land, and instrument-airplane ratings. His latest FAA first class medical certificate was dated September 9, 2013. At the time, he indicated 1,850 hours of flight time. The first officer was a relatively recent hire; according to company records, he was assigned a first officer position on October 3, 2013 after completing his FAA proficiency checkride on October 2, 2013. Company records also indicated that as of November 30, 2013, the first officer had 1,954 total flight hours, 92 hours in type, and 92 hours in the previous 90 days. Night flight hours could not be ascertained. According the company Director of Operations (DO), after arrival in Santo Domingo, the crew would typically have been transported to a local hotel where they would have spent the next 10 hours at rest, typically arriving at the hotel at 0800 and then being picked up at 1800 for transport back to the airport for the flight back to San Juan. "The day was typically spent, resting, eating, lounging by the pool and/or taking a nap; each pilot had their own agenda." The DO also noted that the company's standard operating procedure was for the non-flying pilot to be responsible for all radio communications. However, it would not necessarily always be the case. The DO, who had flown with both pilots previously, listened to the radio transmissions recorded by the FAA and recognized the first officer's voice. AIRCRAFT INFORMATIONDescription Airframe An Airworthiness Group Chairman's Factual Report is located in the public docket for this accident, including airplane structural diagrams in Attachment 1. From the report, the following airframe description is provided: The airplane was an all metal, twin engine, propeller driven, low wing, pressurized airplane originally equipped to carry 19 passengers. It had a cruciform tail and retractable tricycle landing gear. The airplane was powered by two turboprop engines and was configured to only carry cargo at the time of the accident. The fuselage was a semi-monocoque structure composed primarily of aluminum alloy frames, skins, stringers, and bulkheads. The fuselage had three major sections that joined together at production splices. The forebody structure included the cockpit, the mid-section structure included the entry door, emergency exits, passenger windows, cargo door and wing attach points. The aftbody structure included the attach points for the vertical stabilizer. The fuselage could be pressurized between the forward pressure bulkhead and the aft pressure bulkhead. The wing was attached to the lower portion of the fuselage at four points, two on the main spar and two on the rear spar. The wing was a one-piece design with continuous main and rear spars, integral fuel tanks and removable flaps and ailerons. The spars were built-up I-beam structures constructed of aluminum alloy with titanium alloy and steel alloy reinforcements on the upper and lower spar caps. The height of both the main and rear spars decreased where they passed under the fuselage. The main spar transitioned from about 13 inches tall to about 9 inches tall and the rear spar transitioned from about 10 inches tall to about 9 inches tall. Five-foot wing extensions were attached to the outboard end of each wing to increase the span to 57 feet. The airplane also included conventional horizontal and vertical stabilizers composed primarily of aluminum alloy components. The vertical stabilizer was a cantilever design with two spars attached to bulkheads in the aft fuselage. A cable-driven rudder and trim tab were attached to the aft spar of the vertical stabilizer. The horizontal stabilizers were of cantilever design fastened together at the fuselage centerline and attached to the vertical stabilizer with a trunnion bolt. The stabilizer could pivot around the trunnion bolt, changing the angle of incidence of the stabilizer and providing pitch trim for the airplane. All-aluminum cable-driven elevators were attached to the horizontal stabilizers and fastened together at the center splice plate hinge point. The pitch trim was controlled electrically by switches on the control yokes that actuated two motor-operated jackscrews mounted to the top of the fuselage. The ailerons, elevators, and rudder were manually controlled from either the pilot or copilot station in the cockpit by a conventional yoke and rudder pedals. Aileron control cables, 1/8 inch in diameter, interconnected the yokes and ran through several pulleys aft under the floor to an aileron drum in the center wing area. The aileron drum was connected to a series of push-pull tubes that ran along the aft side of the rear spar on each wing to bellcranks mounted near the aileron inboard hinges. Push-pull tubes connected the ailerons to the bellcranks for aileron control. Elevator control cables, 1/8 inch in diameter, ran from the elevator walking beam immediately aft of the columns through several pulleys aft under the floor to the elevator quadrant in the vertical stabilizer. Push-pull tubes connected the elevators to the quadrant for elevator control. Rudder cables, 1/8 inch in diameter, ran through several pulleys aft under the floor to the rudder bellcrank in the aft fuselage. A rudder bellcrank drove the rudder torque tube for rudder control. Aileron and rudder trim were manually set via control wheels on the center pedestal in the cockpit. The aileron and rudder trim cables, 1/16 inch in diameter, ran through several pulleys to their respective tabs. The flaps were electrically controlled and hydraulically actuated. Fuel System According to the SA227 Maintenance Manuel, the fuel system had a usable capacity of 648 U.S. gallons. Fuel was contained in integral left and right wing fuel tanks. Each engine was supplied fuel by an independent system that included the tanks, boost pumps and check valves. An interconnecting cross flow line was installed for balancing the fuel quantity between the left and right wing tanks, and for supplying either engine with all available fuel. A 2-inch cross flow line was located in the center wing section, aft of the main spar. Fuel cross flow was via gravity, controlled by a shut off valve in the 2-inch cross flow line. When the valve was opened, a center light on the fluid annunciator panel should have illuminated. According to the manufacturer's pilot checklist, the cross flow valve should have been closed on engine start, taxi, and descent. A representative of the manufacturer indicated that upon removal of electrical power, the cross flow valve would be in the last position selected. Fuel cross flow procedures included: In flight, "Check aircraft is in coordinated flight. Open the cross flow valve and observe proper annunciation. In level, unaccelerated flight, fuel will flow in the desired direction (heavy to light) due to gravity. To expedite process, use aileron control and place the wing with less fuel to a lower position (no more than 5 degrees is needed) than the wing with more fuel. Use rudder to maintain assigned heading. Maintain a safe margin of airspeed during this 'slip' condition. When fuel balance approaches desired indications, close the cross flow valve, check for proper annunciation, and return aircraft to trimmed condition." According to the flight manual, maximum allowable fuel imbalance was 500 pounds. The IBC Airways weight and balance sheet found at the accident site stated, from "SDQ" to "SJU," that there were 1,800 pounds of fuel onboard. Engines The airplane was powered by two Honeywell (Garrett) TPE331-11U single shaft engines, each producing 1,100 horsepower and driving a four-bladed metal McCauley propeller. The engines did not have a full auto-feathering capability. Instead, each had a negative torque sensing (NTS) system which, if a negative torque was sensed (such as during an engine failure) it would automatically drive the propeller to a coarser pitch. Full feathering would then be accomplished via manual activation. Loading The airplane was loaded mostly with letters and small boxes. Weight and Balance calculations indicated that the airplane was about 2,800 pounds under maximum gross takeoff weight, and would have been about 3,100 pounds under maximum landing weight. Additional Equipment The airplane was not equipped with an autopilot or yaw damper. There were no cockpit or flight data recorders onboard the airplane, nor were any required by the FAA with the airplane in a cargo configuration. The airplane had been equipped with a cockpit voice recorder previously, when it was in a passenger configuration. There was no non-volatile memory available for download. Maintenance Records According to the Maintenance Records Review located in the public docket for this accident, the airplane was originally manufactured in 1985. IBC Airways, Inc. acquired the airplane on March 29, 1999. The airplane had 33,883.4 total hours with 35,698 total cycles as of November 29, 2013. The airplane was maintained per a Continuous Airworthiness Maintenance Program (CAMP). All the required regulatory requirements and recurring inspections were incorporated into the CAMP. The CAMP utilized a phased inspection interval by zones as well as an 85-hour repetitive service check. The phased inspection check intervals were every 150 hours and numbered one through six. In addition to the phased inspections, there were supplemental inspections that were tracked individually. As part of the maintenance records review, attention was focused on the airplane's pitch control. The CAMP included a light inspection of the tail (zone 8) at the phase two interval and a heavy inspection at phase 5. A review of all daily flight logs from January 2012 through November 29, 2013, was completed. Particular attention was also given to flight controls, engines, and flight instruments, unusual flight characteristics such as airframe vibration, pitch, roll, and yaw attitude. Additional areas of review included the environmental control system and any systemic issues. No significant or unusual findings were noted with the flight logs. All major alterations and repairs were reviewed. There were 14 major alterations and 21 major repairs on the airplane. Of note, one of the major repairs was accomplished in June 2008 due to right wing damage. Repairs were made to the wing skins, ribs and main spar. In addition, 18 of the 21 major repairs were accomplished on the wings, elevators, fuselage and doors in June of 1991. The maintenance records also included an item for the pitch trim warning box being overhauled on September 4, 2008, and subsequently installed on the airplane on December 22, 2009. There was also an item for the left elevator outboard attach hinge being replaced due to corrosion on October 18, 2011. More detailed information can be found in the Maintenance Records Review contained in the public docket for this investigation. Previous Flights According to the captain who had flown the airplane with the accident first officer on December 1, 2013, the day before the accident flight, they flew four legs, "with no indications of any mechanical irregularities. The aircraft performed well and showed no problems." Another captain, who had flown the airplane on November 25, 26, and 28, 2013, the last two flights being with the accident first officer, stated, "there were no discrepancies noted during the [time the] aircraft was assigned to me." METEOROLOGICAL INFORMATIONWeather, recorded at TJSJ, 33 nm to the east, at 1956, included wind from 170 degrees true at 5 knots, visibility 10 miles, a few clouds at 7,000 feet, and scattered clouds at 10,000 feet. A review of weather radar images at the time of the accident revealed no precipitation in the area. U.S. Naval Observatory data indicated that sunset occurred at 1749 and that the end of civil twilight occurred at 1813. The accident occurred near the Arecibo Radio Telescope. According to a staff astronomer, a passive project (receive data and observations) was ongoing at the time with no radars transmitting. AIRPORT INFORMATIONDescription Airframe An Airworthines
The flight crew's excessive elevator input during a rapid descent under night lighting conditions, which resulted in the overstress and breakup of the airplane. Contributing to the accident was an initial loss of airplane control for reasons that could not be determined because postaccident examination revealed no mechanical anomalies that would have precluded normal operation.
Source: NTSB Aviation Accident Database
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