Cessna 208B Grand Caravan

The single engine aircraft departed Managua-Augusto C. Sandino Airport in the morning on a flight to Bluefields, carrying two pilots and 14 passengers, most of them members of a development aid organization. While approaching the destination, the crew initiated a VFR descent to Bluefields in marginal weather conditions. At an altitude of 2,000 feet, the aircraft struck the slope of Mt Silva located in the Zelaya Central Mountain Range. The wreckage was found about 50 km west of Bluefields and all 16 occupants were killed, among them a Swiss citizen.

Regency Express Air Operations Flight 434, a Cessna 208 Caravan (serial number 208B0061), was en route from Vancouver International Airport to Victoria International Airport, British Columbia, on a night visual flight rules (VFR) flight when it collided with trees on Saltspring Island, about five nautical miles (nm) north of the Victoria International Airport. The aircraft broke apart on impact and a post-crash fire occurred. The two pilots, who were the sole occupants of the aircraft, sustained fatal injuries, and the aircraft was destroyed. The accident occurred at 0030 Pacific standard time (PST).

The airplane was making an instrument landing system approach in instrument meteorological icing conditions when control was lost. The airplane impacted the terrain 1.6 miles from the approach end on the runway. The airplane contacted the terrain with the left wing first prior to cartwheeling and coming to rest approximately 120 feet from the point of first impact. The pilot had 19 hours total flight time in Cessna 208's of which 1.9 hours were in actual instrument meteorological conditions.

The flight was in radio contact with air traffic controllers at the FAA Memphis Air Route Traffic Control Center (ARTCC), and was level at 9,000 feet, when the pilot checked in on frequency. The last radio contact with the flight was at 0447. At 0520, radar contact was lost. The airplane impacted in rough terrain, at a steep angle of impact. Two other company pilots flying in trail of the accident aircraft said, they had radio contact with the pilot of N840FE about 5 minutes before the accident. They said he sounded fine and did not say anything about any problems. Radar data showing the flight's ground speed indicated that at 0512, the ground speed was 158 knots (182 mph). The ground speed then decreased to 153 (176 mph), 143 (165 mph), 138 (159 mph), and 132 (152 mph), until at 0519:40, when the ground speed of the flight was 125 knots (144 mph). After the radar read out at 0519:40, the next radar hit was coast (no information), and then the flight disappeared from the radar scope. The airplane's heading and altitude did not change during the decrease in ground speed. According to the NTSB Radar Data Study, calculated flight parameters indicated the airplane "...experienced a slow reduction of airspeed in the final 8 minutes of flight at altitude, and then abruptly exhibited a sharp nose down pitch attitude with a rapid increase in airspeed." About the time of the reduction in airspeed, pitch angle began to slowly increase also. When radar contact was lost, the calculated airspeed had reduced to less then 102 knots [118 mph], and calculated body angle of attack [AOA] had increased to 8.8 degrees. A large reduction in pitch angle, angle of attack, and flight path angle as the airspeed increases after peak AOA was reached. Examination of the engine Power Analyzer and Recorder (PAR) revealed that no exceedences were in progress at the time power was removed from the PAR. It was determined that no caution timing events were in progress. The PAR computer appeared to be operating correctly until power was removed at impact. Examination of the airplane's autopilot were not conclusive due to impact damage. Determination of whether the autopilot was engaged or not engaged at the time of the accident could not be determined. The NTSB Meteorological Factual Report revealed that at 0515, about 7 minutes before the flight was lost on radar, the radiative temperature in an area centered at Clarksville (4 kilometer resolution data), showed that the Mean Radiative Temperature was -6.26 degrees C (21F). The Minimum Radiative Temperature was -6.66 degrees C (19F). The Maximum Radiative Temperature was -6.06 degrees C (21F). According to the Archive Level II Doppler weather radar tape for a beginning sweep time of 0508:10, showed that N840FE had tracked into a weather echo from 0510:34, to 0516:28. The Doppler Weather Radar data, revealed that N840FE, had entered a weak weather echo about the same time that the airspeed of the airplane started to decrease, at an altitude of about 9,000 feet, and the airplane was in the weak weather echo for a few minutes. Based on the weather data, it was determined that in-flight airplane icing conditions were encountered by N840FE. Cessna Aircraft Company Airworthiness Directive (AD) 96-09-15; Amendment 39-9591; Docket No. 96-CE-05-AD, applicable to this airplane and complied with by the company, on December 12, 1996, stated: "...to minimize the potential hazards associated with operating the airplane in severe icing conditions by providing more clearly defined procedures and limitations associated with such conditions... operators must initiate action to notify and ensure that flight crewmembers are apprised of this change...revise the FAA-approved Airplane Flight Manual (AFM) by incorporating the following into the Limitation Section of the AFM. This may be accomplished by inserting a copy of this AD in the AFM...." The airplane was equipped with leading edge deicing boots on the wings, elevators, struts, and had a cargo pod deicing capability. Lights were installed to illuminate the leading edge of the wings, to aid the pilot in detecting ice on the leading edges of the wings during night operations. The airplane was not equipped with an ice detection device.

The pilot was reported to be in a hurry as he positioned two aircraft and picked up the accident aircraft for his final positioning leg. He told company personnel he had a birthday party to go to and his family confirmed this. The pilot reported to company personnel that he was departing on runway 3 and that he would report in on his arrival at the destination. No further contacts with the flight were made and the wreckage of the aircraft was discovered off the end of the departure runway about 40 minutes after his reported takeoff. Examination showed the aircraft had run off the left side of the runway about 800 feet from the end and then crossed over the runway and entered into the woods at the departure end of the runway. Post crash examination showed no evidence of pre crash failure or malfunction of the aircraft structure, flight controls, or engine. The onboard engine computer showed the engine was producing normal engine power and the aircraft was traveling at 98 knots when electrical power was lost as it collided with trees. The aircraft's control lock was found tangled in the instrument panel near the left control yoke where it is normally installed and the lock had multiple abnormal bends, including a 90 degree bend in the last 1/2 inch of the lock where it engages the control column. Removal of the control lock and checking the flight controls for freedom is on the normal pilots checklist. The pilot was also found to not be wearing his shoulder harness.

The pilot, who was also the station manager, arrived at the airport earlier than other company employees to prepare for a scheduled commuter flight, transporting seven passengers and cargo to another village during hours of arctic, predawn darkness. Heavy frost was described on vehicles and airplanes the morning of the accident, and the lineman who serviced the airplane described a thin glaze of ice on the upper surface of the left wing. The pilot was not observed deicing the airplane prior to flight, and was described by the other employees as in a hurry to depart on time. The pilot directed the lineman to place fuel in the left wing only, which resulted in a fuel imbalance between 450 and 991 pounds (left wing heavy). The first turn after takeoff was into the heavy left wing. The airplane was observed climbing past the end of the runway, and descending vertically into the water. No preimpact mechanical anomalies were found with the airplane or powerplant. The aileron trim indicator was found in the full right wing down position. Postaccident flight tests with left wing heavy lateral fuel imbalances, disclosed that approximately one-half of right wing down aileron control deflection was used to maintain level flight, thus leaving only one-half right wing down aileron control efficacy. Research has shown that frost on airfoils can result in reduced stall angles of attack (often below that required to activate stall warning devices), increases in stall speeds between 20% and 40%, asymmetric stalls resulting in large rolling moments, and differing stall angles of attack for wings with upward and downward deflected ailerons (as when recovering from turns).

The airplane departed under visual flight rules (VFR) for a flight over mountainous terrain. It was tracked by radar from the departure area to the accident site. While climbing at the normal rate of climb to 15,400 feet, the airplane abruptly disappeared from radar. The wreckage was located among pine trees and exhibited evidence of a steep flight path angle and damage consistent with a stall/spin event. Investigation revealed no indication of airframe or flight control anomalies, and the powerplant and propeller damage was consistent with engine operation at moderate to high power. Evidence indicated that the airplane was free of airframe ice at impact. Postaccident calculations indicate that the airplane was near the maximum certificated gross weight and aft center of gravity limit. The pilot did not maintain instrument flying currency and reportedly avoided instrument meteorological conditions (IMC). Evidence indicated that the pilot did not use oxygen, as required (when flying above 12,000 feet). Ground observations and satellite and Doppler radar imagery indicated widespread cloudiness over the mountains west of Montrose on the day of the accident. Satellite data showed variable cloud tops higher than the airplane's flight altitude in the vicinity of the accident. The radar plot of the aircraft during the climb above 10,000 feet indicated course changes from the southwest to the northwest, back to the southwest and then a sharp turn to the right just prior to the rapid descent.

The pilot had contacted the FSS 11 times on the day of the accident to obtain weather briefings. The conditions were below VFR minimums, which were required to conduct the passenger carrying commercial flight in a single-engine airplane. The conditions later improved and the pilot departed under a special VFR clearance. The pilot performed two approaches at the destination airport in IMC that were consistent with the two GPS approaches that were available there. Weather data and witnesses indicate that daylight conditions, low clouds and poor visibility prevailed, with cloud tops at 1,000 feet. After the second approach, the pilot radioed that he was heading back to the departure airport because he could not see the airport. No distress calls or unusual engine noises were heard. The airplane subsequently flew north of the airport and away from the departure airport at an altitude beneath the minimum radar coverage of 2,200 feet. It impacted the frozen Arctic Ocean in a right bank and at a 60-degree nose-down attitude about three miles away from the location of the pilot's last radio transmission. An examination of the airplane (before it sank through cracking ice) revealed no pre-impact mechanical malfunctions. An examination of the propeller revealed that it was under a power setting consistent with a maneuvering airspeed at the time of impact. An examination of the autopilot annunciator filament revealed that the autopilot was not engaged at impact. The airplane was nearly full of fuel and over its published maximum gross weight at impact. Small pieces of clear ice, about 1/4-inch thick, were found on portions of the tail surfaces. Interviews with operator employees and the pilot's wife revealed that the pilot may have felt pressure from himself and passengers to complete the flight.