Central America

The commercial pilot and his wife departed New York in their turboprop airplane on a crosscountry flight to Florida. About 1 hour 40 minutes into the flight and while cruising at flight level (FL) 280, the pilot notified air traffic control (ATC) of an abnormal indication in the airplane and requested a descent to FL180. The responding controller instructed the pilot to descend to FL250 and turn left 30°, and the pilot acknowledged and complied with the instruction; he then again requested a lower altitude. Although the pilot declined emergency handling and did not specify the nature of the problem, the controller independently determined that the flight had encountered a pressurization issue and immediately coordinated with another ATC facility to clear nearby traffic. The controller then issued instructions to the pilot to descend to FL200 and change course; however, the pilot did not comply with the assignments despite acknowledging the instructions multiple times. The pilot's failure to comply with the controller's instructions, his long microphone pauses after concluding a statement over the radio, and his confusion were consistent with cognitive impairment due to hypoxia. Further, the pilot's transmissions to ATC indicated impairment within 2 minutes 30 seconds of reporting the abnormal indication, which is consistent with the Federal Aviation Administration's published time of useful consciousness/effective performance time ranges for the onset of hypoxia. Military airplanes were dispatched about 30 minutes after the pilot's final transmission to ATC to intercept and examine the airplane. The pilots of the military airplanes reported that the airplane appeared to be flying normally at FL250, that both occupants appeared to be asleep or unconscious, and that neither occupant was wearing an oxygen mask. Photographs taken from one of the military airplanes revealed that the airplane's emergency exit door was recessed into the fuselage frame, consistent with a depressurized cabin. The military airplanes escorted the airplane as it continued on a constant course and altitude until it approached Cuban airspace, at which point they discontinued their escort. Radar data indicated that the airplane continued on the same flight track until about 5 hours 48 minutes after takeoff, when it descended to impact in the Caribbean Sea north of Jamaica. The flight's duration was consistent with a departure with full fuel and normal cruise endurance. Some of the wreckage, including fuselage and engine components, was recovered from the ocean floor about 4 months after the accident. Data recovered from nonvolatile memory in the airplane's global air system controller (GASC) indicated that several fault codes associated with the cabin pressurization system were registered during the flight. These faults indicated that the overheat thermal switch (OTSW), which was associated with overheat protection, had activated, which resulted in a shutdown of the engine bleed air supply to the cabin pressurization system. Without a bleed air supply to maintain selected cabin pressure, the cabin altitude would have increased to the altitude of the outside environment over a period of about 4 minutes. The faults recorded by the GASC's nonvolatile memory and associated system alerts/warnings would have been displayed to the pilot, both as discrete system anomaly messages on the crew alerting system (CAS) and as master warning and/or master caution annunciations. A witness report indicated that the pilot was known to routinely monitor cabin altitude while flying in the airplane and in his previous pressurized airplanes. Based on his instrument scanning practices and the airplane's aural warning system, he likely would have observed any CAS message at or near its onset. Thus, the CAS messages and the associated alerts were likely the precipitating event for the pilot's call to ATC requesting a lower altitude. The pilot was likely not familiar with the physiological effects of hypoxia because he had not recently been in an altitude chamber for training, but he should have been familiar with the airplane's pressurization system emergency and oxygen mask donning procedures because he had recently attended a transition course for the accident airplane make and model that covered these procedures. However, the pressurization system training segment of the 5-day transition course comprised only about 90 minutes of about 36 total hours of training, and it is unknown if the pilot would have retained enough information to recognize the significance of the CAS messages as they appeared during the accident flight, much less recall the corresponding emergency procedures from memory. Coupled with the pilot's reported diligence in using checklists, this suggests that he would have attempted a physical review of the emergency procedures outlined in the Pilot's Operating Handbook (POH). A review of the 656-page POH for the airplane found that only one of the four emergency checklist procedures that corresponded to pressurization system-related CAS messages included a step to don an oxygen mask, and it was only a suggestion, not a mandatory step. The combined lack of emergency guidance to immediately don an oxygen mask and the rapid increase in the cabin altitude significantly increased the risk of hypoxia, a condition resistant to self-diagnosis, especially for a person who has not recently experienced its effects in a controlled environment such as an altitude chamber. Additionally, once the pilot reported the problem indication to ATC, he requested a descent to FL180 instead of 10,000 ft as prescribed by the POH. In a second transmission, he accepted FL250 and declined priority handling. These two separate errors were either early signs of cognitive dysfunction due to hypoxia or indications that the pilot did not interpret the CAS messages as a matter related to the pressurization system. Although the cabin bleed-down rate was 4 minutes, the pilot showed evidence of deteriorating cognitive abilities about 2 minutes 30 seconds after he initially reported the problem to ATC. Ultimately, the pilot had less than 4 minutes to detect the pressurization system failure CAS messages, report the problem to ATC, locate the proper procedures in a voluminous POH, and complete each procedure, all while suffering from an insidious and mentally impairing condition that decreased his cognitive performance over time. Following the accident, the airplane manufacturer revised the emergency procedures for newly manufactured airplanes to require flight crews to don their oxygen masks as the first checklist item in each of the relevant emergency checklists. Further, the manufacturer has stated that it plans to issue the same revisions for previous models in 2017. The airplane manufacturer previously documented numerous OTSW replacements that occurred between 2008 and after the date of the accident. Many of these units were removed after the GASC systems in their respective airplanes generated fault codes that showed an overheat of the bleed air system. Each of the OTSWs that were tested at the manufacturer's facility showed results that were consistent with normal operating units. Additionally, the OTSW from the accident airplane passed several of the manufacturer's functional tests despite the presence of internal corrosion from sea water. Further investigation determined that the pressurization system design forced the GASC to unnecessarily discontinue the flow of bleed air into the cabin if the bleed air temperature exceeded an initial threshold and did not subsequently fall below a secondary threshold within 30 seconds. According to the airplane manufacturer, the purpose of this design was to protect the structural integrity of the airplane, the system, and the passengers in case of overheat detection. As a result of this accident and the ensuing investigation, the manufacturer made changes to the programming of the GASC and to the airplane's wiring that are designed to reduce the potential for the GASC to shut off the flow of bleed air into the cabin and to maximize the bleed availability. Contrary to its normal position for flight, the cockpit oxygen switch was found in the "off" position, which prevents oxygen from flowing to the oxygen masks. A witness's description of the pilot's before starting engine procedure during a previous flight showed that he may not have precisely complied with the published procedure for turning on the oxygen switch and testing the oxygen masks. However, as the pilot reportedly was diligent in completing preflight inspections and checklists, the investigation could not determine why the cockpit oxygen switch was turned off. Further, because the oxygen masks were not observed on either occupant, the position of the oxygen switch would not have made a difference in this accident.

On 18 August, 2014 at 10:02am local time (1402Z) UTC a fixed wing, twin-engine, Cessna 3 4 0 A aircraft, United States registration N340MM, serial number 340A0635, crashed into waters while on a left base to runway 06 at Grand Bahama International Airport (MYGF) Freeport, Grand Bahama, Bahamas. The aircraft departed Ormond Beach Municipal Airport (KOMN) at 8:51am local time (1251Z) for Grand Bahama International Airport (MYGF) on an Instrument Flight Rules (IFR) flight plan with the pilot and three passengers aboard. Sometime after 9:00am (1300Z) an IFR inbound flight plan on N340MM was received by Freeport Approach Control from Miami Center. Upon initial contact with Freeport Approach Control the pilot was given weather advisory, re-cleared to Freeport VOR and told to maintain four thousand feet and report at JAKEL intersection. He was also advised to expect an RNAV runway six approach. After the pilot’s acknowledgement of the information he later acknowledged his position crossing JAKEL. Freeport Approach then instructed the aircraft to descend to two thousand feet and cleared him direct to JENIB intersection for the RNAV runway six (6) approach. After descending to two thousand feet the pilot indicated to Freeport Approach that he had the field in sight and was able to make a visual approach. Freeport Approach re-cleared the aircraft for a visual approach and instructed the pilot to contact Freeport Control Tower on frequency 118.5. At 9:57am (1357Z) N340MM established contact with Freeport Tower and was cleared for the visual approach to runway six; he was told to join the left base and report at five (5) DME. At 10:01am (1401Z) the pilot reported being out of fuel and his intention was to dead stick the aircraft into the airport from seven miles out at an altitude of one thousand five hundred feet. A minute later the pilot radioed ATC to indicate they “were going down and expected to be in the water about five miles north of the airport.” Freeport Tower tried to get confirmation of the last transmission but was unable to. Several more calls went out from Freeport Tower to N340MM but communication was never reestablished. Freeport Control Tower then made request of aircrafts departing and arriving to assist in locating the lost aircraft by over flying the vicinity of the last reported position to see if visual contact could be made. An inbound aircraft reported seeing an aircraft down five miles from the airport on the 300 degree radial of the ZFP VOR. Calls were made to all the relevant agencies and search and rescue initiated. The aircraft was located at GPS coordinates 26˚ 35.708’N and 078˚ 47. 431 W. The aircraft received substantial damage as a result of the impact and crash sequence. There were no survivors.

Following an uneventful flight from Cozumel, the crew initiated an ILS/DME2 approach to Saltillo-Plan de Guadalupe Airport Runway 17. On final, the crew encountered poor visibility due to foggy conditions. Despite he was unable to establish a visual contact with the runway, the crew continued the approach and descended below the MDA when the aircraft collided with power cables and crashed on a building located in an industrial park, 1,448 metres short of runway. The aircraft was destroyed by impact forces and a post crash fire and all eight occupants were killed. The building was also destroyed by fire. At the time of the accident, the horizontal visibility was estimated to be 800 metres with a vertical visibility of 200 feet.

The aircraft belly landed at Stella Maris-Estate Airport, Bahamas. No one was hurt but the aircraft was damaged beyond repair. Apparently, the approach checklist was interrupted by the crew for unknown reason and the landing procedure was performed with the landing gear still retracted. The aircraft was owned by the private Canadian company Kelly Panteluk Construction and the airplane was inbound from Fort Lauderdale-Executive.

The aircraft departed Managua on a cargo flight to Saltillo with an intermediate stop in Tapachula, carrying two passengers and two pilots on behalf of DHL. During a night approach to Saltillo Airport, the crew was cleared to land on runway 17. One minute later, he initiated a go-around and decided to divert to Monterrey Airport which was the alternate. Due to a poor flight preparation, the crew was unaware that Monterrey Airport was closed to traffic that night. So few minutes later, the crew returned to Saltillo and was again cleared to land on runway 17. At that time, weather conditions were marginal with a limited visibility due to fog. Following an ILS CAT I approach, the pilot-in-command descended below the MDA and continued the approach despite he did not establish any visual contact with the runway and its equipment. The aircraft landed hard to the right of the runway and on the last third of the runway. After landing, the aircraft rolled for few dozen metres, lost its nose gear and came to rest against an embankment. All four occupants were injured and the aircraft was damaged beyond repair.

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.

The twin engine aircraft departed Monterrey-Del Norte Airport at 0820LT on a flight to Xalapa-El Lencero Airport, Veracruz. While cruising in marginal weather conditions, the airplane crashed in the Sierra Madre Oriental, near the summit of Mirador. The aircraft was destroyed by a post crash fire and both occupants were killed.

The single engine aircraft departed Loreto Airport at 0901LT on a flight to Ciudad Constitución, carrying 13 passengers and one pilot. Weather conditions were poor with limited visibility and heavy rain falls due to the presence of the tropical storm 'Octave'. Six minutes after takeoff, while cruising at an altitude of 3,900 feet, the airplane impacted the slope of a rocky mountain located in the Sierra de La Giganta. The wreckage was found two days later some 26 km west of Loreto. The aircraft disintegrated on impact and all 14 occupants were killed.

The commercial, instrument-rated pilot of the multiengine airplane was conducting a newspaper delivery flight in night visual meteorological conditions. After two uneventful legs, the pilot departed on the third leg without incident. Radar data indicated that, after takeoff, the airplane flew over open water at an altitude of about 100 to 200 ft toward the destination airport and then climbed to 2,400 ft. Shortly thereafter, the pilot performed a 360-degree left turn, followed by a 360-degree right turn while the airplane maintained an altitude of about 2,400 ft, before continuing toward the destination airport. Less than 2 minutes later, the airplane began a rapid descending left turn and then collided with water. The wreckage was subsequently located on the sea floor near the airplane's last radar target. Both wings, the cabin, cockpit, and nose section were destroyed by impact forces. The wreckage was not recovered, which precluded its examination for preimpact malfunctions. The airplane had been operated for about 25 hours since its most recent inspection, which was performed about 3 weeks before the accident. The pilot had accumulated about 1,650 hours of total flight experience, which included about 1,100 hours in the accident airplane make and model. Although the pilot conducted most of his flights during the day, he regularly operated flights in night conditions. The pilot's autopsy did not identify any findings of natural disease significant enough to have contributed to the accident. In addition, although toxicological testing detected ethanol in the pilot's cavity blood, it likely resulted from postmortem production.

According to the pilot, he applied full power, set the flaps at 10 degrees, released the brakes, and, after reaching 80 knots, he rotated the airplane. The pilot further reported that the engine subsequently lost total power when the airplane was about 150 ft above ground level. The airplane then impacted water in a nose-down, right-wing-low attitude about 300 ft from the end of the runway. The pilot reported that he thought that the runway was 1,900 ft long; however, it was only 1,300 ft long. Review of the takeoff ground roll distance charts contained in the Pilot’s Operating Handbook (POH) revealed that, with flap settings of 0 and 20 degrees, the ground roll would have been 1,700 and 1,150 ft, respectively. Takeoff ground roll distances were not provided for use of 10 degrees of flaps; however, the POH stated that 10 degrees of flaps could be used. Although the distance was not specified, it is likely that the airplane would have required more than 1,300 ft for takeoff with 10 degrees of flaps. Examination of the engine revealed saltwater corrosion throughout it; however, this was likely due to the airplane’s submersion in water after the accident. No other mechanical malfunctions or abnormalities were noted. Examination of data extracted from the multifunction display (MFD) and primary flight display (PFD) revealed that the engine parameters were performing in the normal operating range until the end of the recordings. The data also indicated that, 7 seconds before the end of the recordings, the airplane pitched up from 0 to about 17 degrees and then rolled 17 degrees left wing down while continuing to pitch up to 20 degrees. The airplane then rolled 77 degrees right wing down and pitched down about 50 degrees. The highest airspeed recorded by the MFD and PFD was about 70 knots, which occurred about 1 second before the end of the recordings. The POH stated that, depending on the landing gear position, flap setting, and bank angle, the stall speed for the airplane would be between 65 and 71 knots. Based on the evidence, it is likely that the engine did not lose power as reported by the pilot. As the airplane approached the end of the runway and the pilot realized that it was not long enough for his planned takeoff, he attempted to lift off at an insufficient airspeed and at too high of a pitch angle, which resulted in an aerodynamic stall at a low altitude. If the pilot had known the actual runway length, he might have used a flap setting of 20 degrees, which would have provided sufficient distance for the takeoff.