Soldotna, AK, USA
N93PC
DEHAVILLAND DHC-3
Before picking up the nine passengers, the pilot loaded the accident airplane at the operator's base in Nikiski with cargo (food and supplies for the lodge). The operator of the lodge where the passengers were headed estimated the cargo weighed about 300 pounds (lbs) and that the passengers' baggage weighed about 80 lbs. Estimates of the passengers' weights were provided to the lodge operator in preparation for the trip, which totaled 1,350 lbs. The load manifest listed each of these weight estimates for a total weight of 1,730 lbs and did not contain any balance data. The cargo was not weighed, and the pilot did not document any weight and balance calculations nor was he required to do so. The airplane operator did not keep fueling records for each flight. A witness who was present during the fueling operations at the operator's base reported that he saw the pilot top off the front tank then begin fueling the center tank. The first leg of the trip from the operator's base to pick up the passengers was completed uneventfully. According to witnesses at Soldotna Airport, after loading the passengers and their baggage, the pilot taxied for departure. There were no witnesses to the accident. The airplane impacted the ground about 2,320 feet from the threshold of the departure runway and about 154 feet right of the runway centerline. An extensive postcrash fire consumed most of the airplane's cockpit and cabin area, including an unknown quantity of the baggage and cargo. Impact signatures were consistent with a nose- and right-wing-low attitude at impact. The entire airplane was accounted for at the wreckage site. Disassembly and examination of the engine and propeller revealed that both were operating during impact. Examination of the structure and flight control systems found no preimpact malfunctions or failures that would have precluded normal operation. The pilot was properly certificated and qualified in accordance with applicable federal regulations. Toxicological testing of specimens from the pilot was negative for any carbon monoxide, alcohol, or drugs. The airplane was not equipped, and was not required to be equipped, with any type of crash-resistant recorder. A video recovered from a passenger's smartphone showed the accident sequence looking out of the row 4 left seat window; the left wing and flaps are in view for most of the sequence and the flap position does not change. The investigation found that the flaps were set to the full-down (or landing) position during takeoff, contrary to recommended procedures in the airplane flight manual (AFM). The recovered video was used to estimate the airplane speed, altitude, and orientation for the portion of the flight where ground references were visible, about 22.5 seconds after the start of the takeoff roll. For the first 12 seconds, the airplane accelerated linearly from the beginning of the takeoff roll through liftoff. The pitch angle decreased slightly in the first 8 seconds as the tail lifted, remained essentially constant for about 4 seconds, and began to slightly increase as the airplane lifted off. Beginning about 14 seconds after the start of the takeoff roll, the speed began decreasing and the pitch angle began increasing. The pitch angle increased at a constant rate (about 2.8 degrees/second), reaching a maximum value of about 30 degrees, and the ground speed decreased from its maximum of about 68 mph to about 44 mph at the end of the analyzed time. The ground references disappeared from the video frame as the airplane experienced a sharp right roll before impacting the ground several seconds later. The low speed, rapid right roll, and pitch down of the airplane is consistent with an aerodynamic stall. The constant pitch rate before the stall is consistent with an aft center of gravity (CG) condition of sufficient magnitude that the elevator pitch down authority was insufficient to overcome the pitching moment generated by the aft CG. Additionally, the flaps setting at the full-down (or landing) position, contrary to procedures contained in the AFM, would have exacerbated the nose-up pitching moment due to the increased downwash on the tail and aft shift of the center of pressure; the additional aerodynamic drag from the fully extended flaps would have altered the airplane's acceleration. Using the data available, the airplane was within weight and balance limitations for the first leg of the trip. However, the cargo loaded was about 2.4 times the weight indicated on the load manifest. Further, the total weight of cargo and baggage in the cargo area, as estimated during the investigation, exceeded the installed cargo net's load limit of 750 lbs by more than 50 lbs. Although the loaded cargo actual weight was higher than indicated on the load manifest, the flight from Nikiski to Soldotna was completed without any concerns noted by the pilot, indicating that even with the higher cargo load, the airplane was within the normal CG range for that leg of the flight. Thus, based on the investigation's best estimate and a calculation of the airplane's weight and balance using the recovered passenger weights, weights and location of the luggage recovered on scene, weight of the cargo recovered on scene, and weights accounting for the liquid cargo destroyed in the postimpact fire, once the passengers were loaded, the airplane weight would have exceeded the maximum gross weight of 8,000 lbs by about 21 lbs and the CG would have been at least 5.5 inches aft of the 152.2-inch limit (a more definitive calculation could not be performed because the exact location of the cargo was not known). Additionally, the kinematics study of the accident airplane's weight and motion during initial climb and up to the point of stall found that with the pilot applying full pitch-down control input, the CG required to produce the motion observed in the video was likely just past 161 inches. Thus, the only way for the airplane motion to match the motion observed in the video was for the CG to be considerably aft of the 152.2-inch limit, which provides additional support to the results from the weight and balance study. Based on the video study, the weight and balance study constructed from available weight and balance information, and the kinematics study, the airplane exceeded the aft CG limit at takeoff, which resulted in an uncontrollable nose-up pitch leading to an aerodynamic stall. The CG was so far aft of the limit that the airplane likely would have stalled even with the flaps in the correct position. Neither 14 CFR Part 135 nor the operator's operations specifications (OpSpec) require that the aircraft weight and balance be physically documented for any flights. However, according to Section A096 of the OpSpec, when determining aircraft weight and balance, the operator should use either the actual measured weights for all passengers, baggage, and cargo or the solicited weights for passengers plus 10 lbs and actual measured weights for baggage and cargo. The operator did not comply with federal regulations that require adherence to the weighing requirements or the takeoff weight limitations in the AFM. Additionally, although the inaccurate estimate of 300 lbs for the cargo resulted in a calculated CG that was within limits for both legs of the flight, the actual weight of the cargo was significantly higher. Once loaded in Soldotna, the combination of the passengers, their baggage, and the actual cargo weight and its location resulted in the CG for the accident flight being significantly aft of the limit. With the CG so far aft, even with full nose-down input from the pilot, the nose continued to pitch up until the airplane stalled. For each flight in multiengine operations, 14 CFR 135.63(c) requires the preparation of a load manifest that includes, among other items the number of passengers, total weight of the loaded aircraft, the maximum allowable takeoff weight, and the CG location of the loaded aircraft; one copy of the load manifest should be carried in the airplane and the operator is required to keep the records for at least 30 days. Single-engine operations are excluded from this requirement. The NTSB attempted to address this exclusion with the issuance of Safety Recommendations A-89-135 and A-99-61, which asked the Federal Aviation Administration (FAA) to amend the record-keeping requirements of 14 [CFR] 135.63(c) to apply to single-engine as well as multiengine aircraft. The FAA did not take the recommended action in either instance, and the NTSB classified Safety Recommendations A-89-135 and A-99-61 "Closed—Unacceptable Action" in 1990 and 2014, respectively.
HISTORY OF FLIGHTOn July 7, 2013, about 1120 Alaska daylight time, a deHavilland DHC-3 Otter airplane, N93PC, collided with terrain shortly after takeoff from Soldotna Airport, Soldotna, Alaska. The commercial pilot and nine passengers died, and the airplane was destroyed. The airplane was registered to Rediske Family Limited Partnership, Nikiski, Alaska, and was operated by Rediske Air, Nikiski, Alaska, under the provisions of 14 Code of Federal Regulations (CFR) Part 135 as an on-demand charter flight. Visual meteorological conditions prevailed, and no flight plan was filed for the flight, which was destined to Bear Mountain Lodge, about 90 miles southwest of Soldotna. On the day of the accident, the pilot was in Nikiski and was scheduled to fly a different trip with the accident airplane, but shortly before the planned departure time, the trip was canceled. The group of nine passengers on board the accident flight had been scheduled to go to the lodge in two of the operator's smaller airplanes; however, the pilot decided to use the Otter after his previous flight was canceled so that the group could fly together on one plane. The lodge operator, who was in Nikiski before the departure, requested that a load of groceries and lodge supplies be flown with the group and brought the supplies to Rediske Air's base of operations. The lodge operator estimated the cargo weighed about 300 lbs. After the pilot unloaded the cargo from the canceled flight, he and the lodge owner loaded the groceries and lodge supplies on the accident airplane. Rediske Air did not keep fueling records for each flight. A witness who was present during the fueling operations at Nikiski reported that he saw the pilot top off the forward tank then begin fueling the center tank. The witness later returned to the fuel supply tank to fuel his helicopter and thought he noticed 56 gallons on the fuel reader. He said that he and the accident pilot would have been the only people to use the fuel tank. The first leg of the trip was a positioning flight from Nikiski to Soldotna, where the passengers were to be picked up. The flight was completed uneventfully. According to witnesses at Soldotna Airport, after loading the passengers and their baggage, the pilot taxied to runway 25 for departure. There were no witnesses to the accident sequence. The airplane impacted the ground about 2,320 ft from the threshold of runway 25 and about 154 feet right of the runway centerline. Impact signatures were consistent with a nose-low, right-wing-low attitude at impact. PERSONNEL INFORMATIONThe pilot, age 42, held a commercial pilot certificate with an airplane single-engine land, multiengine land, and instrument ratings. His most recent second-class airman medical certificate was issued July 11, 2012, and contained no limitations. On April 24, 2012, the pilot was approved as a check airman in single-engine land airplanes flown by Rediske Air. A review of Rediske Air's training records showed that the pilot's initial ground training in the Otter was completed on June 28, 2011. The pilot's most recent 14 CFR Part 135 competency check in the Otter was accomplished on June 15, 2012, and his most recent recurrent ground training in the airplane was completed on the same date. The pilot received Part 135 competency and line checks in a Cessna 206 airplane on May 15, 2013. Personal flight logbooks for the pilot were not located, but his most recent insurance application, dated April 23, 2013, showed a total flight time of 7,765 hours with a total time in DHC-3 airplanes of 105 hours. The insurance form for the previous year indicated a total time in DHC-3 airplanes of 155 hours. His total flying time in the last 12 months was listed as 350 hours. A review of company flight and duty time records for the pilot found no entries after June 23, 2013. Company personnel attempted to recreate a record of the pilot's flights between that date and the day of the accident but were unable to create a complete log because company flight records did not indicate pilots' names for each flight. According to the records that could be recreated, the pilot flew 1.9 hours the day before the accident and 6.1 hours in the 72 hours before the accident. The pilot's spouse reported that, 2 days before the accident, the pilot went to work about 0600. She recalled that they took their children to a movie that started at 1920 and that they returned home between 2100 and 2130. She stated that the day before the accident was a normal workday for the pilot and that he left for work by 0830. She stated that he returned home and had dinner about 1830 to 1900. She reported that the pilot fell asleep between 2100 and 2130. On the day of the accident, she did not talk to the pilot before he left for work and did not know the time that he left but recalled that it was light outside. AIRCRAFT INFORMATIONThe accident airplane, serial number 280, was manufactured in 1958 by the deHavilland Aircraft Company of Canada and was a single-engine, propeller-driven, single-pilot, high-wing short takeoff and landing (STOL) airplane. It was modified with a Honeywell TPE 331-10R-511C turboprop engine per a Texas Turbine Conversions, Inc. supplemental type certificate (STC). It was equipped with a Hartzell model HC-B4TN-5NL four-blade propeller. The airplane was also modified with a Baron STOL kit per an STC to improve its performance. The airplane was configured to carry 10 passengers and cargo and had a maximum gross weight of 8,000 lbs. Airplane maintenance records indicated that STCs for cargo net installation and for installation of shoulder harnesses had been installed. The cargo compartment on the original airplane had a load limit of 650 pounds. The cargo net STC stated that the aft cargo area had a load limit of 750 pounds. Information from the STC holder substantiated the increased load limit in the cargo area due to the increased size of the compartment. In July 2010, the previous owner sent the airplane to Recon Air Corporation in Geraldton, Ontario, Canada, for a major overhaul and the conversion to a turbine-powered airplane at an airplane total time of 22,536.5 hours. In addition to the Baron STOL kit STC, a pulse light control system STC and an extended range fuel system STC were installed. The STC approval pages for these STCs were contained in the permanent maintenance records and were dated July 12, 2010. Recon also performed all required inspections and complied with all applicable airworthiness directives (AD) during the overhaul. On July 9, 2010, the airplane was removed from the Canadian Civil Aircraft Register and placed on the US registry as N93PC. At this time, the airplane received an FAA standard airworthiness certificate in the Normal category. Following the Recon conversion, in August 2010, three additional STCs were incorporated by Peninsula Aero Technology in Kenai, Alaska, to install updated avionics in the airplane at an airplane total time of 22,566.2 hours. The Rediske Family Limited Partnership purchased the airplane in October 2010. The airplane was maintained under an Approved Airplane Inspection Program (AAIP) dated February 11, 2011, that was approved by the FAA on March 9, 2011. The AAIP was used for maintaining the accident airplane in lieu of conventional 100-hour and annual inspections. The AAIP divided the maintenance of the airplane into four consecutive phase inspections to be performed every 50 hours of flight time. There was a special note in the AAIP that required accomplishment of all four phase inspections within each 12 months even if the airplane hour requirements were not met. The AAIP had provisions for a 10-hour grace period on all of the phase inspections. All special inspection items, calendar time inspections, ADs, and service bulletins (SB) outside the scope of the phase inspections were to be tracked and complied with under the AAIP. Rediske Air, Inc. documented all of the requirements of the AAIP in the aircraft inspection record maintained at the company headquarters. On June 17, 2011, an inspection of the airplane in accordance with annual, 800-hour, phases 1-4, and all calendar and special inspection items was completed at an airframe total time of 22,611.8 hours, and the airplane was placed on the AAIP. At this time, the engine and propeller had accumulated 75.3 hours and 26 cycles since the conversion. The records indicated that all applicable ADs were complied with at this time. The most recent inspection of the airplane incorporated phases 2, 3, and 4 on June 13, 2013, at an airplane total time of 22,831.8 hours and engine and propeller times of 295.3 hours since overhaul and installation on the airplane. Ten discrepancies were recorded during the most recent inspections and all were rectified. None of the discrepancies were notable in terms of major repairs to the airplane. Weight and Balance The weight and balance information for the airplane was contained in the aircraft inspection record. As part of the Recon overhaul, the airplane was physically weighed on July 7, 2010, with the cargo net, ELT, turbine engine conversion, STOL kit, extended range fuel system, and pulse light system listed as installed equipment. The empty weight, as weighed, was 4,259.00 lbs with a center of gravity (CG) at 132.66 in. The notes stated that the airplane had residual fuel, full oil, and full hydraulic fluid for this weighing. In August 2010, the weight and balance was recalculated after the installation of the updated avionics. The new empty weight, as calculated, was 4,283.09 lbs with a CG at 132.66 in. The NTSB calculated the airplane's weight and balance based on the data from the August 2010 paperwork. The total moment of removed equipment was calculated to be 138 lb-in greater than that in the paperwork. The data for the total installed equipment was also calculated to be different than that in the paperwork. The total installed weight was calculated to be 1.5 lbs greater, the total moment was calculated to be 103.50 lb-in greater, and the arm (CG) was calculated to be 2.11 in less. The resultant total weight was calculated to be 4,284.59 lbs with a CG at 132.60 in. Subsequent to this calculation, the airplane weight and balance was recalculated on September 22, 2010, by Rediske Air to add two flashlights with a total weight of 3.4 lbs at an arm location of 111.0 in. With this equipment added, the airplane empty weight was calculated to be 4,287.99 lbs with a CG at 132.59 in. See the Weight and Balance Study for details of the empty weight recalculations. Operations Specifications for Weight and Balance Section A096 of the operator's operations specifications (OpSpecs) only allowed the operator to use actual weights for determining weight and balance. The current section was approved in March 2009. The operator was allowed two options for determining the actual weights: either use measured weights for all passengers and bags or use solicited passenger weights plus 10 lbs and measured weights for all bags. The procedure for cargo weight was not explicitly stated in the OpSpecs. The specifications listed loading schedules for five specific airplanes (a Britten-Norman Islander and four Cessna 206 or 207s), but the DHC-3 airplane was not included; however, it was included in the Aircraft Authorizations section of the OpSpecs. Determining the airplane's actual weight and balance before flight should be accomplished using the procedures contained in the original DHC-3 Otter Airplane Flight Manual (AFM) published by de Havilland Canada along with the information in the various flight manual supplements for the STCs installed on the airplane. The entire flight manual and all supplements were carried in the airplane during the accident flight. Portions of some of the manuals were recovered in the wreckage with fire and water damage. Copies of the flight manual and all supplements were obtained from the various manufacturers for use by the investigation. Estimated scenarios of the accident airplane's weight and balance based on the factual information available are presented in the Additional Information section of this report. METEOROLOGICAL INFORMATIONAn automated weather observing system (AWOS) at Soldotna Airport reported at 1116 wind from 190° at 6 knots, 10 miles visibility, temperature of 12° C, dew point temperature of 8°C, and an altimeter setting of 29.58 in of mercury. Visual flight rules conditions prevailed around the accident time. AIRPORT INFORMATIONThe accident airplane, serial number 280, was manufactured in 1958 by the deHavilland Aircraft Company of Canada and was a single-engine, propeller-driven, single-pilot, high-wing short takeoff and landing (STOL) airplane. It was modified with a Honeywell TPE 331-10R-511C turboprop engine per a Texas Turbine Conversions, Inc. supplemental type certificate (STC). It was equipped with a Hartzell model HC-B4TN-5NL four-blade propeller. The airplane was also modified with a Baron STOL kit per an STC to improve its performance. The airplane was configured to carry 10 passengers and cargo and had a maximum gross weight of 8,000 lbs. Airplane maintenance records indicated that STCs for cargo net installation and for installation of shoulder harnesses had been installed. The cargo compartment on the original airplane had a load limit of 650 pounds. The cargo net STC stated that the aft cargo area had a load limit of 750 pounds. Information from the STC holder substantiated the increased load limit in the cargo area due to the increased size of the compartment. In July 2010, the previous owner sent the airplane to Recon Air Corporation in Geraldton, Ontario, Canada, for a major overhaul and the conversion to a turbine-powered airplane at an airplane total time of 22,536.5 hours. In addition to the Baron STOL kit STC, a pulse light control system STC and an extended range fuel system STC were installed. The STC approval pages for these STCs were contained in the permanent maintenance records and were dated July 12, 2010. Recon also performed all required inspections and complied with all applicable airworthiness directives (AD) during the overhaul. On July 9, 2010, the airplane was removed from the Canadian Civil Aircraft Register and placed on the US registry as N93PC. At this time, the airplane received an FAA standard airworthiness certificate in the Normal category. Following the Recon conversion, in August 2010, three additional STCs were incorporated by Peninsula Aero Technology in Kenai, Alaska, to install updated avionics in the airplane at an airplane total time of 22,566.2 hours. The Rediske Family Limited Partnership purchased the airplane in October 2010. The airplane was maintained under an Approved Airplane Inspection Program (AAIP) dated February 11, 2011, that was approved by the FAA on March 9, 2011. The AAIP was used for maintaining the accident airplane in lieu of conventional 100-hour and annual inspections. The AAIP divided the maintenance of the airplane into four consecutive phase inspections to be performed every 50 hours of flight time. There was a special note in the AAIP that required accomplishment of all four phase inspections within each 12 months even if the airplane hour requirements were not met. The AAIP had provisions for a 10-hour grace period on all of the phase inspections. All special inspection items, calendar time inspections, ADs, and service bulletins (SB) outside the scope of the phase inspections were to be tracked and complied with under the AAIP. Rediske Air, Inc. documented all of the requirements of the AAIP in the aircraft inspection record maintained at the company headquarters. On June 17, 2011, an inspection of the airplane in accordance with annual, 800-hour, phases 1-4, and all calendar and special inspection items was completed at an airframe total time of 22,611.8 hours, and the airplane was placed on the AAIP. At this time, the engine and propeller had accumulated 75.3 hours and 26 cycles since the conversion. The records indicated that all applicable ADs were complied with at this time. The most recent inspection of the airplane incorporated phases 2, 3, and 4 on June 13, 2013, at an airplane total time of 22,831.8 hours and en
The operator's failure to determine the actual cargo weight, leading to the loading and operation of the airplane outside of the weight and center of gravity limits contained in the airplane flight manual, which resulted in an aerodynamic stall. Contributing to the accident was the Federal Aviation Administration's failure to require weight and balance documentation for each flight in 14 Code of Federal Regulations Part 135 single-engine operations.
Source: NTSB Aviation Accident Database
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