United States of America

The pilot/owner and a flight instructor had flown in to pick-up passengers. The owner was not multiengine rated and was receiving instruction from the instructor. The airplane was fueled and two adults and three children were boarded about 1 hour later. The owner was the flying pilot in the left seat. The owner stated that the 4,500 foot long runway was covered with 2 1/2 to 3 inches of snow and slush. He further stated that during the takeoff roll, 'The snow was so bad we could not get off the ground...' The pilot estimated that he aborted the takeoff at 100 mph, the braking action was zero, and the airplane went off the end of the runway. According to a witness, the five passengers arrived with 'lots of heavy bags.' After the accident, the baggage was removed before it could be weighed. An estimated airplane takeoff weight of 7,856 pounds was computed without baggage, based upon weights from the airplane weight and balance form, the police report, and FAA records. According to the Pilot's Operating Handbook, the maximum takeoff weight was published at 7,560 pounds.

The pilot was cleared for an ILS DME approach to runway 17L. During the final stage of the approach, the aircraft entered fog and disappeared from view of the control tower personnel. Radar and radio communications were lost also. After searching for 31 minutes, the aircraft was found by airport operations personnel over half way down the runway and 600 feet east of the runway. There was no evidence the aircraft touched down on the runway. The aircraft was configured with the landing gear up and the flaps deployed. Missed approach procedures require the flaps and landing gear to be retracted after initiating the procedure. The decision
height for the approach is 6,384 feet msl (200 feet above ground level) and the required RVR for a 14 CFR Part 135 flight to commence and approach is 2400 (1/2 mile). When on the glide slope, the decision height is 0.4 miles from the runway touchdown zone. Examination of the airplane did not disclose evidence of mechanical malfunction.

The pilot departed Front Range Airport (elevation 5512 feet) at approximately 2008, climbed to 7,000 feet msl, accelerated to 270 knots, and requested his IFR clearance. Weather at the time of N950TT's departure was 500 feet overcast; witnesses reported the tops of the thin cloud condition were 8,500 feet msl and it was very dark on top (no stars or moon). The pilot made several changes in airspeed and climb rate until radar indicated that he had entered an 8,500 fpm decent. The pilot reported to ATC that he had 'stalled' the airplane. Radar indicated that he then climbed at 7,500 fpm until his estimated airspeed was 10 knots, and then subsequently descended again at 8,400 fpm until he impacted the frozen ground. The pilot had flown 4 times for 7 hours in the previous 40 days. Five airline pilots, each of who had 3,000 to 5,000 hours in Swearingens, stated individually that even though the airplane is single pilot certified, they believed that 'its a two pilot airplane--because the work load is too high.'

The flight was operating into the Yakima airport at night during the period the airport operates as non-towered. Some witnesses reported the aircraft initially appeared lower than normal and that it descended and impacted the ground at a steep angle, and some witnesses reported an abrupt entry into the descent. The aircraft crashed 2.2 nautical miles east of the runway threshold, slightly right of the localizer course The pilot was 'cleared for approach' by air traffic control (ATC) and he subsequently initiated an instrument landing system (ILS) approach to runway 27. The last radar position showed the aircraft approximately on the localizer, at glide slope intercept altitude, 9 nautical miles east of the airport. Three minutes after the last radar position, the pilot reported to ATC he had broken out and had the airport in sight, and canceled instrument flight rules (IFR). ATC then terminated service and approved a frequency change.. Ceiling was 1,500 feet overcast with 6 miles visibility in mist, with no significant icing forecast. No evidence of mechanical problems was found; however, much of the aircraft was consumed by an intense post-crash fire.

Following a missed approach at the destination, the pilot requested weather information for two nearby airports. One airport was 53 miles northeast with a cloud ceiling of 900 feet, and visibility 6 miles. The pilot opted for the accident airport, 21 miles southwest, with an indefinite ceiling of zero, and visibility 1/4 mile. After completing the second missed approach, the flight proceeded to the accident airport. Radar vectors were provided to the ILS runway 36L. On the final approach, the flight veered to the right of the localizer and descended abruptly. Last recorded altitude for the flight was below the decision height. Investigation revealed no anomalies with the airport navigational aids for the approach, and the airplane's navigation receivers were found to be operational. Postmortem examinations of the pilot did not reveal any pre-existing diseases, and toxicological examinations were negative for alcohol and other drugs.

The pilot made four missed ILS approaches at the airport. He stated that he did not see the approach lights during any of the approaches and did not feel comfortable making a landing. The reported visibility during these approaches was 1/2-statute mile. On the fifth approach the pilot said he had '...mistaken closely inline cars and a road for the MALSR and runway.' He pilot stated the airplane continued to descend after initiating a go-around. He said he saw oncoming traffic in front of him, and turned the airplane to the right. He said he lost altitude and the right wing struck the ground. The pilot's employers operations specification require a 1/4- mile increase in visibility for an ILS approach that does not have an operating approach lighting system. The approach lights were checked by the airport manager and were confirmed to be in working order. An on-scene investigation revealed no pre-accident airframe or engine anomalies that would have prevented normal flight.

The Short Brothers SD3-60 cargo flight was being vectored for the VOR/DME RWY 28R approach to the Billings Logan International airport during instrument meteorological conditions. Weather conditions one minute before the accident were winds 020 at 13 knots, light snow and mist, and visibility was deteriorating rapidly. The co-pilot (occupying the right seat) was flying the aircraft, and the PIC (occupying the left seat) was handling radio communications. At 0812:25, having crossed the final approach fix, the aircraft descended through 100 feet above the MDA (3,940 feet or 426 feet above the runway threshold), and immediately thereafter the crew visually acquired the runway. At 0813:01 the aircraft's GPWS alert of 'SINK RATE' was heard, followed 2 seconds later by the PIC calling for 'POWER,' and a 2 second delay to ground impact. The co-pilot had logged a total of 103 hours in the SD3-60 (all within the previous 90 days,) while the PIC had just begun flying the aircraft in Montana's late fall weather after a 6 year assignment flying in the Hawaiian islands. The left main landing gear collapsed in overload during the ground impact.

The pilots reported they experienced an engine fire during a missed approach in night, IMC conditions, and feathered the propeller and shut down the engine. On an approach to another airport, the airplane touched down short of the runway, traveled onto the runway, and then departed the left side of the runway. The pilot reported he could not maintain altitude due to ice accumulations, and the lack of power with one engine shut down. Examination of the wreckage revealed rotational damage to both engines and propellers consistent with operating engines. Neither propeller was in the feathered position. The pilot had been briefed about known moderate icing conditions, and isolated severe icing. The AFM recommended a minimum speed in icing conditions of 140 knots, and at less than 140 knots, ice could accumulate on the wings in unprotected areas. The pilot reported he flew the approach at 114 knots.

During an IFR arrival, vectors were provided for an ILS runway 16L approach. While on assigned heading and altitude of 270 degrees and 3,000 feet, about 8 miles north of the final approach fix, the pilot was told to turn left to 185 degrees and maintain 2,200 feet until established on the localizer, then he was cleared for the approach. The pilot acknowledged the instructions. About 1 minute later, communication and radar contact with the airplane were lost. Eye witnesses near the accident site observed the airplane as it descended below the cloud layer. The airplane was described as being in a steep left bank with the nose down. Witnesses also stated that the engines were revving. Within seconds of the visual sighting, the airplane crashed. Examination of the airframe failed to disclose a mechanical problem. No fire or smoke was seen coming from the airplane before it crashed. The pilot did not report experiencing a problem with the airplane to the tower controller. Toxicology tests of the pilot indicated O.323 mcg/ml chlorpheniramine (a sedating antihistamine) in liver fluid and 0.073 mcg/ml chlorpheniramine in kidney fluid. Also, unspecified levels of dextromethorphan (a cough suppressant), pseudoephedrine (a decibgestabt), and phenylpropanolamine (a decongestant) were reported in kidney and liver fluids. All medications are available in over-the-counter cold remedies.

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).