Idaho Falls

The pilot and passengers flew in the day before the accident and the airplane remained parked outside on the airport ramp overnight. Light to moderate snow and freezing drizzle persisted during the 12 to 24-hour period preceding the accident. In addition, low instrument meteorological conditions existed at the time of the accident takeoff. Before the flight, the pilot removed snow and ice from the airplane wings. However, the horizontal stabilizer was not accessible to the pilot and was not cleared of accumulated snow. In addition, the airplane was loaded over the maximum certificated gross weight and beyond the aft center-of-gravity limit. A total of 12 occupants were on board the airplane, though only 10 seats were available. None of the occupants qualified as lap children under regulations. The takeoff rotation was initiated about 88 kts which was about 4 kts slower than specified with the airplane configured for icing conditions. After takeoff, the airplane entered a left turn. Airspeed varied between 89 and 97 kts during the initial climb; however, it decayed to about 80 kts as the airplane altitude and bank angle peaked. The airplane ultimately reached a left bank angle of 64° at the peak altitude of about 380 ft above ground level. The airplane then entered a descent that continued until impact. The stall warning and stick shaker activated about 1 second after liftoff. The stick pusher became active about 15 seconds after liftoff. All three continued intermittently for the duration of the flight. A witness located about 1/2-mile northwest of the airport reported hearing the airplane takeoff. It was cloudy and snowing at the time. He was not able to see the airplane but noted that it entered a left turn based on the sound. He heard the airplane for about 4 or 5 seconds and the engine seemed to be “running good” until the sound stopped. The airplane impacted a dormant corn field about 3/4-mile west of the airport. A postaccident airframe examination did not reveal any anomalies consistent with a preimpact failure or malfunction. On board recorder data indicated that the engine was operating normally at the time of the accident. An airplane performance analysis indicated that the accumulated snow and ice on the empennage did not significantly degrade the airplane performance after takeoff. However, the effect of the snow and ice on the airplane center-of-gravity and the pitch (elevator) control forces could not be determined. Simulations indicated that the pitch oscillations recorded on the flight could be duplicated with control inputs, and that the flight control authority available to the pilot would have been sufficient to maintain control until the airplane entered an aerodynamic stall about 22 seconds after lifting off (the maximum bank angle of 64° occurred after the critical angle-of-attack was exceeded). In addition, similar but less extreme pitch oscillations recorded on the previous flight (during which the airplane was not contaminated with snow but was loaded to a similar center-of-gravity position) suggest that the pitch oscillations on both flights were the result of the improper loading and not the effects of accumulated snow and ice. Flight recorder data revealed that the accident pilot tended to rotate more rapidly and to a higher pitch angle during takeoff than a second pilot who flew the airplane regularly. Piloted simulations suggested that the accident pilot’s rotation technique, which involved a relatively abrupt and heavy pull on the control column, when combined with the extreme aft CG, heavy weight, and early rotation on the accident takeoff, contributed to the airplane’s high angle-of attack immediately after rotation, the triggering of the stick shaker and stick pusher, and the pilot’s pitch control difficulties after liftoff. The resulting pitch oscillations eventually resulted in a deep penetration into the aerodynamic stall region and subsequent loss of control. Although conditions were conducive to the development of spatial disorientation, the circumstances of this accident are more consistent with the pilot’s efforts to respond to the activation of the airplane stall protection system upon takeoff. These efforts were hindered by the heightened airplane pitch sensitivity resulting from the aft-CG condition. As a result, spatial disorientation is not considered to be a factor in this accident.

The airplane was equipped with two main fuel tanks (132 usable gallons each) and two nacelle fuel tanks (60 usable gallons each). In normal operation, fuel from each nacelle tank is supplied to its respective engine, and fuel is automatically transferred from each main tank to its respective nacelle tank. While at the airplane's home airport, the pilot noted that the cockpit fuel quantity gauges indicated that the nacelle tanks were full, and he believed that the main tanks had fuel sufficient for 30 minutes of flight. The pilot did not verify by any other means the actual fuel quantity in any of the tanks. Thirty gallons of fuel were added to each main tank; they were not topped off. The airplane, with two passengers, then flew to an interim stop about 45 miles away, where a third passenger boarded. The airplane then flew to its destination, another 165 miles away. The pilot reported that, at the destination airport, he noted that the cockpit fuel quantity gauges indicated that the nacelle tanks were full; he surmised that the main fuel tanks were not empty but did not note the actual quantity of fuel. Forty gallons of fuel were added to each main tank. Again, the main tanks were not topped off, and the pilot did not verify by any other means the actual fuel quantity in any of the tanks. The return flight to the interim stop was uneventful. The third passenger deplaned there, and the airplane departed for its home airport. While on final approach to the home airport, both engines stopped developing power, and the pilot conducted a forced landing to a field about 1.2 miles short of the runway. The pilot later reported that, at the time of the power loss, the fuel quantity gauges indicated that there was still fuel remaining in the airplane. Postaccident examination of the airplane revealed that all four fuel tanks were devoid of fuel. The examination did not reveal any preimpact mechanical anomalies, including fuel leaks, that would have precluded continued flight. The airplane manufacturer conducted fuel-consumption calculations for each of the two city pairs. Because the pilot did not provide any information regarding flight routes, altitudes, speeds, or times for any of the flight segments, the manufacturer's calculations were based on direct routing in zero-wind conditions, nominal airplane and engine performance, and assumed cruise altitudes and speeds. Although the results are valid for these input parameters, variations in any of the input parameters can significantly affect the calculated fuel requirements. As a result, although the manufacturer's calculations indicated that the round trip would have burned less fuel than the total available fuel quantity that was derived from the pilot-provided information, the lack of any definitive information regarding the actual flight parameters limited the utility of the calculated value and the comparison. The manufacturer's calculations indicated that the accident flight leg (from the interim airport to the home airport) would have consumed about 28.5 gallons total. Given that the airplane was devoid of fuel at the accident site, the pilot likely departed the interim airport with significantly less than the manufacturer's minimum allowable departure fuel quantity of about 39.5 gallons per side. The lack of any observed preimpact mechanical problems with the airplane, combined with the lack of objective or independently substantiated fuel quantity information, indicates that the airplane's fuel exhaustion was due to the pilot's inadequate and improper pre- and inflight fuel planning and procedures.

The aircraft was cleared direct and to climb to 14,000 feet. During the climb out, the controller inquired several times as to the flights altitude. The pilot's response to the controllers queries were exactly 10,000 feet lower than what the controller was indicating on radar. Eventually the controller instructed the pilot to stop altitude squawk, which he did. During the last communication with the pilot, he reported that he was level at 14,000 feet. During the next approximately 45 minutes, the aircraft was observed proceeding generally in the direction of its destination. When the controller observed the flight track turn approximately 45 degrees to the right and headed generally northwest, he attempted to contact the pilot without a response. The tracking then turned about 90 degrees to the left for a few minutes, then turned 180 degrees to the right. The aircraft dropped from radar coverage shortly thereafter. On site investigation revealed that the aircraft broke-up in flight as the wreckage was scattered generally east-to-west over the mountainous terrain for approximately .3 nautical miles. Further investigation revealed that the right wing separated at the wing root in an upward direction. Separation points indicated features typical of overload. The right side horizontal stabilizer separated upward and aft. The left side horizontal stabilizer remained attached however, it was twisted down and aft. The aft fuselage was twisted to the left. Both engines separated in flight from the wings. Post-crash examinations of the airframe and engines did not reveal evidence of a mechanical failure or malfunction. Both altimeters were too badly damaged to test. Autopsy and toxicology results indicated that the pilot had severe coronary artery disease with greater than 95% narrowing of the left anterior descending coronary artery by atherosclerotic plaque. The coroner also reported that superimposed upon this severe narrowing was complete occlusion of the lumen by brown thrombus. Toxicology results indicated a moderate level of diabetes. The pilot's actions leading up to the accident were consistent with an incapacitation due to hypoxia. The role of a possible heart attack was unclear, since it is possible that it occurred as a result of the hypoxia.

The accident aircraft had recently had maintenance work performed on its autofeather system pressure sensing switches, due to reports of the left engine not autofeathering properly in flight. The purpose of the accident flight was to verify proper inflight operation of the autofeather system following the maintenance work on the autofeather pressure sensing switches and a successful ground check of the autofeather system. Air traffic control (ATC) communications recordings disclosed that the pilot called ready for takeoff from runway 2 approximately 1207, and requested to orbit above the airport at 8,000 feet (note: the airport elevation is 4,740 feet.) The pilot subsequently reported established in a hold above the airport at 8,000 feet approximately 1213, and was instructed by ATC to report leaving the hold. Approximately 1215, an abbreviated radio transmission, "zero five four," was recorded. The Idaho Falls tower controller responded to this call but never got a response in return from the accident aircraft, despite repeated efforts to contact the aircraft. Witnesses reported that the aircraft banked to the left, or to the west, and that it entered a spiral from this bank and crashed (one witness reported the aircraft was flying at 200 to 300 feet above ground level when it entered this bank, and that it performed a "skidding" or "sliding" motion part way through the bank, about 1 second before entering the spiral.) The aircraft crashed about 2 miles north of the airport. On-site examination disclosed wreckage and impact signatures consistent with an uncontrolled, relatively low-speed, moderate to steep (i.e. greater than 22 degrees) angle, left-wing-low impact on an easterly flight path. No evidence of flight control system malfunction was found, and a large quantity of jet fuel was noted to be aboard the aircraft. Post-accident examination of the aircraft's engines indicated that the left engine was most likely operating in a low power range and the right engine was most likely operating in a mid to high power range at impact, but no indications of any anomalies or distress that would have precluded normal operation of the engines prior to impact was found. Post-accident examination of the aircraft's propellers disclosed indications that 1) both propellers were rotating at impact, 2) neither propeller was at or near the feather position at impact, 3) both propellers were being operated with power at impact (exact amount unknown), 4) both propellers were operating at approximately 14º to 20º blade angle at impact, and 5) there were no propeller failures prior to impact. Post-accident examination of the autofeather pressure sensing switches disclosed evidence of alterations, tampering, or modifications made in the field on all but one switch (a replacement switch, which had been installed just before the accident flight during maintenance) installed on the aircraft at the time of the accident. All switches except for the replacement switch operated outside their design pressure specifications; the replacement switch operated within design pressure specifications. Examination of the switches indicated that all switches were installed in the correct positions relative to high- or low-pressure switch installations. Engineering analyses of expected autofeather system performance with the switches operating at their "as-found" pressure settings (vice at design pressure specifications) did not indicate a likelihood of any anomalous or abnormal autofeather system operation with the autofeather switches at their "as-found" pressure settings. Also, cockpit light and switch evidence indicated that the autofeather system was not activated at the time of impact. The combination of probable engine power and propeller pitch on the left engine (as per the post-accident engine and propeller teardown results) was noted to be generally consistent with the "zero-thrust" engine torque and propeller RPM settings specified for simulated single-engine practice in the aircraft Information Manual.

N2336X was on a business flight to Cody, WY. The pilot executed a missed approach on the first attempt of the VOR-A approach. A pilot who landed at Cody minutes before the accident said the visibility had decreased to 3/4 of a mile when N2336X made the first approach and approx 1/2 mile when N2336X crashed. Examination of the wreckage revealed no evidence of a mechanical malfunction or failure of the aircraft prior to accident. The sas servo arm was found in the full up position. The aircraft struck the terrain in a steep nose low attitude on a heading that was opposite to the direction of flight. Approach minimums at Cody are 5,800 feet and 1 mile visibility. All three occupants were killed.

Before takeoff, the pilot received a weather briefing and filed an IFR flight plan to Idaho Falls, ID at 13,000 feet. He took off at 1804 pst. At 1814 pst, just prior to calling level at 13,000 feet, he reported he was encountering light turbulence and light rime ice. Approximately four min later, the pilot reported experiencing heavy vibrations. He requested and received a clearance to return to Portland and descend to 7,000 feet. Shortly after that, the aircraft entered a tight descending turn which the pilot reported he was having difficulty arresting. He reported regaining directional control at 6,000 feet and said the aircraft had a heavy load of ice. Shortly thereafter, the aircraft crashed in mountains at the 3,130 feet level. Due to damage from impact and wreckage retrieval, the preimpact condition of all deicing components was not verified. The aircraft was not certified for flight in known icing conditions. Moderate mixed icing condition and moderate turbulence were forecast. The pilot was briefed there had been reports of moderate icing thru-out the area. All five occupants were killed.

The crew was engaged in a night training flight in the region of Idaho Falls and Pocatello. En route, pilot lost control of the aircraft that crashed in a desert area located some 50 km west of Idaho Falls. All seven crewmen were killed.
Crew:
Richard A. Hedges,
Lonnie L. Keepers,
Robert W. Madsen,
Richard R. Pitzner,
Louis H. Rinke,
Charles W. Eddy,
George H. Pearce Jr.

Crashed landed at Idaho Falls Airport. No casualties.