Oklahoma

The pilot, sole on board, departed Tulsa-Richard Lloyd Jones Jr. (Riverside) Airport in the morning on an on-demand special mission. After a pass over Sand Springs, west of Tulsa, the airplane continued to the south then the pilot completed three circuits over McAlester before continuing to the southwest. In unclear circumstances, the airplane caught fire in flight and the pilot diverted to Durant-Eaker Field. After landing on runway 17, the pilot stopped the airplane and was able to evacuate without injuries. The airplane was totally destroyed by fire.

The two commercial pilots were conducting a personal, cross-country flight. A video surveillance camera at the airport captured their airplane’s approach. Review of the video revealed that, as the airplane approached the approach end of the landing runway, it began to climb, rolled left, became inverted, and then impacted terrain. The left thrust reverser (T/R) was found open and unlatched at the accident site. An asymmetric deployment of the left T/R would have resulted in a left roll/yaw. The lack of an airworthy and operable cockpit voice recorder, which was required for the flight, precluded identifying which pilot was performing pilot flying duties, as well as other crew actions and background noises, that would have facilitated the investigation. Postaccident examination of the airplane revealed that it was not equipped, nor was required to be equipped, with a nose landing gear (NLG) ground contact switch intended to preclude inflight operation of the thrust reverser (T/R). The left T/R door was found unlatched and open, and the right T/R door was found closed and latched. Further, electrical testing of the T/R left and right stow microswitches within the cockpit throttle quadrant revealed that the left stow microswitch did not operate within design specifications. Disassembly of the left and right stow microswitches revealed evidence of arc wear due to aging. Based on this information, it is likely that the airplane’s lack of an NLG ground contact switch and the age-related failure of the stow microswitches resulted in an asymmetric T/R deployment while on approach and a subsequent loss of airplane control. Also, there were additional T/R system components that were found to unairworthy that would have affected the control of the T/R system. Operational testing of the T/R system could not be performed due to the damage the airplane incurred during the accident. Toxicology testing results of the pilot’s specimens indicated that the pilot had taken diazepam, which is considered impairing at certain levels. However, the detected amounts of both diazepam and its metabolite nordiazepam were at subtherapeutic levels, and given the long half-life of these compounds, it appears that the medication was taken several days before the accident; therefore, it is unlikely that the pilot was impaired at the time of the accident and thus that his use of diazepam was a not factor in the accident.

The pilot was conducting a personal flight with four passengers. A witness observed the airplane take off and climb slowly from the airport. A pilot flying in the vicinity observed the airplane maneuver erratically before the airplane impacted terrain in a near-vertical attitude. The airplane was destroyed by impact forces and a postimpact fire. The wreckage was contained to a confined area in the field and the remains of the major airplane components were all accounted for. Extensive thermal damage to the airframe and engine limited the scope of the postaccident examination. The impact energy needed to drive the engine into the ground suggested that the engine was producing power at the time of the accident. A postaccident examination of the remaining airframe and engine components did not reveal any anomalies which would have precluded normal operation of the airplane. Depending on the amount of fuel, baggage and equipment on board, and the location of the adult passenger, the center of gravity (CG) could have been within or aft of the recommended CG. Since fuel load and location of the passengers could not be determined or may have shifted during flight, it is not known if loading contributed to the accident. The pilot was not operating with valid medical certification. His second-class medical certificate had expired several years prior to the accident and Federal Aviation Administration records did not indicate that he had obtained BasicMed medical certification. A pilot-rated passenger was seated in the rightfront seat. Investigators were unable to determine who was manipulating the flight controls of the airplane at the time of the accident. The circumstances of the accident are consistent with the pilot’s loss of control. However, the reason for the loss of control could not be determined with the available evidence.

The pilot stated that the engine start and airplane power-up were normal for the air medical flight with two medical crewmembers. The engine ice vanes were lowered (as required for ground operations) and then were subsequently raised before takeoff. Takeoff and climbout were routine, and the pilot leveled off the airplane at the assigned cruise altitude. The air traffic controller informed the pilot of heavy showers near the destination airport, and the pilot "put the ice vanes down." The pilot indicated that, shortly afterward, the airplane experienced two "quick" electrical power fluctuations in which "everything went away and then came back," and "[s]econds later the entire [electrical] system failed." Due to the associated loss of navigation capability while operating in instrument meteorological conditions (IMC), the pilot set a general course for better weather conditions based on information from his preflight weather briefing. While the pilot attempted to find a suitable hole in the clouds to descend through under visual conditions, the left engine lost power. The pilot ultimately located a field through the cloud cover and executed a single-engine off-airport landing, which resulted in substantial damage to the right engine mount and firewall. A postaccident examination of the airplane and systems did not reveal any anomalies consistent with an in-flight electrical system malfunction. The three-position ignition and engine start/starter-only switches were in the ON position, and the engine anti-ice switches were in the ON position. When the airplane battery was initially checked during the examination, the voltmeter indicated 10.7 volts (normal voltage is 12 volts); the battery was charged and appeared to function normally thereafter. The loss of electrical power was likely initiated by the pilot inadvertently selecting the engine start switches instead of the engine anti-ice (ice vane) switches. This resulted in the starter/generators changing to starter operation and taking the generator function offline. Airplane electrical power was then being supplied solely by the battery, which caused it to deplete and led to a subsequent loss of electrical power to the airplane. A postaccident examination revealed that neither wing fuel tank contained any visible fuel. The left nacelle fuel tank did not contain any visible fuel, and the right nacelle fuel tank appeared to contain about 1 quart of fuel. The lack of fuel onboard at the time of the accident is consistent with a loss of engine power due to fuel exhaustion. This was a result of the extended flight time as the pilot attempted to exit instrument conditions after the loss of electrical power to locate a suitable airport. Further, the operator reported that 253 gallons (1,720 lbs) of fuel were on board at takeoff, and the accident flight duration was 3.65 hours. At maximum range power, the expected fuel consumption was about 406 lbs/hour, resulting in an endurance of about 4.2 hours. Thus, the pilot did not have the adequate fuel reserves required for flying in IMC. Both the pilot and medical crewmembers described a lack of communication and coordination among crewmembers as the emergency transpired. This resulted in multiple course adjustments that hindered the pilot's ability to locate visual meteorological conditions before the left engine fuel supply was exhausted.

The pilot reported that, during the postmaintenance test flight, the turboprop engine lost power. The airplane was unable to maintain altitude, and the pilot conducted a forced landing, during which the airplane was substantially damaged. The engine had about 9 total flight hours at the time of the accident. A teardown of the fuel pump revealed that the high-pressure drive gear teeth exhibited wear and that material was missing from them, whereas the driven gear exhibited little to no visible wear. A metallurgical examination of the gears revealed that the damaged drive gear was made of a material similar to 300-series stainless steel instead of the harder specified M50 steel, whereas the driven gear was made of a material similar to the specified M50 steel. Subsequent to these findings, the airplane manufacturer determined that the gear manufacturer allowed three set-up gears made from 300-series stainless steel to become part of the production inventory during the manufacturing process. One of those gears was installed in the fuel pump on the accident airplane, and the location of the two other gears could not be determined. Based on the evidence, it is likely that the nonconforming gear installed in the fuel pump failed because it was manufactured from a softer material than specified, which resulted in a loss of fuel flow to the engine and the subsequent loss of engine power. The manufacturer subsequently inspected its stock of gears and issued notices to customers that had engines with fuel pumps installed with the same part number gear set as the one installed on the accident airplane. The manufacturer also issued a service information letter and service bulletins regarding the fuel pump gear set for engines used in civilian and military applications. As of the date of this report, the two remaining gears have not been located.

The airline transport pilot was conducting a business flight with six passengers on board. Radar data showed that, after crossing the final approach fix for an instrument approach at the destination airport, the airplane descended below the minimum descent altitude (MDA) of 2,480 ft mean sea level (msl); dark night, instrument meteorological conditions existed at that time. Subsequently, when the airplane was about 2 miles from the airport and about 2,070 ft msl, the airplane impacted a utility pole, which was 10 ft above ground level (agl). After impacting the pole, the pilot executed a missed approach, and about 40 minutes later, he landed the airplane without further incident at another airport. On-scene examination showed that the impact had scattered debris from the separated utility pole for about 200 ft into a snow-covered field. Examination of the airplane revealed that the impact resulted in substantial damage to the nose structure, lower and upper fuselage, and horizontal stabilizer. Further examinations of the airplane, including its static system, both altimeters, both vertical speed indicators, and the radar altimeter system revealed no evidence of preaccident mechanical malfunctions or failures that would have precluded normal operation. The pilot reported that he thought he had leveled the airplane at an altitude above the MDA and that at no time during the descent and approach did the airplane's radar altimeter sound an alert indicating that the airplane was below 400 ft agl radar altitude. He also reported that he never saw the terrain, any obstructions, nor the runway lights or airport environment. Despite the pilot's statement, given the radar data and the impact evidence, it is apparent that he descended the airplane below the MDA, which resulted in the subsequent impact with the utility pole. It could not be determined why the radar altimeter did not alert the pilot that the airplane was only 10 ft above the ground. The pilot's second-class medical certificate, which had been issued more than 20 months before the accident, had expired. The medical certificate limitation section in the expired certificate stated, "Not valid for night flying or by color signal control." There is no evidence that these restrictions contributed to the accident.

Radar and air traffic control communications indicated that the Mitsubishi MU-2B-25 was operating normally and flew a nominal flightpath from takeoff through the beginning of the approach until the airplane overshot the extended centerline of the landing runway, tracking to the east and left of course by about 0.2 nautical mile then briefly tracking back toward the centerline. The airplane then entered a 360-degree turn to the left, east of the centerline and at an altitude far below what would be expected for a nominal flightpath and intentional maneuvering flight given the airplane's distance from the airport, which was about 5 miles. As the airplane was in its sustained left turn tracking away from the airport, the controller queried the pilot, who stated that he had a "control problem" and subsequently stated he had a "left engine shutdown." This was the last communication received from the pilot. Witnesses saw the airplane spiral toward the ground and disappear from view. Examination of the wreckage revealed that the landing gear was in the extended position, the flaps were extended 20 degrees, and the left engine propeller blades were in the feathered position. Examination of the left engine showed the fuel shutoff valve was in the closed position, consistent with the engine being in an inoperative condition. As examined, the airplane was not configured in accordance with the airplane flight manual engine shutdown and single-engine landing procedures, which state that the airplane should remain in a clean configuration with flaps set to 5 degrees at the beginning of the final approach descent and the landing gear retracted until landing is assured. Thermal damage to the cockpit instrumentation precluded determining the preimpact position of fuel control and engine switches. The investigation found that the airplane was properly certified, equipped, and maintained in accordance with federal regulations and that the recovered airplane components showed no evidence of any preimpact structural, engine, or system failures. The investigation also determined that the pilot was properly certificated and qualified in accordance with applicable federal regulations, including Special Federal Aviation Regulation (SFAR) No. 108, which is required for MU-2B pilots and adequate for the operation of MU-2B series airplanes. The pilot had recently completed the SFAR No. 108 training in Kansas and was returning to Tulsa. At the time of the accident, he had about 12 hours total time in the airplane make and model, and the flight was the first time he operated the airplane as a solo pilot. The investigation found no evidence indicating any preexisting medical or behavioral conditions that might have adversely affected the pilot's performance on the day of the accident. Based on aircraft performance calculations, the airplane should have been flyable in a one engine-inoperative condition; the day visual meteorological conditions at the time of the accident do not support a loss of control due to spatial disorientation. Therefore, the available evidence indicates that the pilot did not appropriately manage a one-engine-inoperative condition, leading to a loss of control from which he did not recover. The airplane was not equipped, and was not required to be equipped, with any type of crash resistant recorder. Although radar data and air traffic control voice communications were available during the investigation to determine the airplane's altitude and flight path and estimate its motions (pitch, bank, yaw attitudes), the exact movements and trim state of the airplane are unknown, and other details of the airplane's performance (such as power settings) can only be estimated. In addition, because the airplane was not equipped with any type of recording device, the pilot's control and system inputs and other actions are unknown. The lack of available data significantly increased the difficulty of determining the specific causes that led to this accident, and it was not possible to determine the reasons for the left engine shutdown or evaluate the pilot's recognition of and response to an engine problem. Recorded video images from the accident flight would possibly have shown where the pilot's attention was directed during the reported problems, his interaction with the airplane controls and systems, and the status of many cockpit switches and instruments. Recorded flight data would have provided information about the engines' operating parameters and the airplane's motions. Previous NTSB recommendations have addressed the need for recording information on airplane types such as the one involved in this accident. Recorders can help investigators identify safety issues that might otherwise be undetectable, which is critical to the prevention of future accidents.

While on the right downwind leg, the flight crew advised the air traffic control tower controller that they would make a full stop landing. The tower controller acknowledged, told them to extend their downwind, and stated that he would call their base turn. The controller then called out the landing traffic on final, which was an Airbus A300-600 heavy airplane. The flight crew replied that they had the traffic in sight, and the controller cleared the flight to land behind the Airbus, and to be cautious of wake turbulence. The flight crew observed the Airbus abeam their current position and estimated that they made their base turn about 3 miles from the runway. Before turning onto final approach, the flight crew discussed wake turbulence avoidance procedures and planned to make a steeper approach and land beyond the Airbus's touchdown point. They also added 10 to 15 knots to the Vref speed as an additional precaution against a wake turbulence encounter. The reported wind provided by the tower controller was 180 degrees at 4 knots. The flight crew observed tire smoke from the Airbus as it touched down and discussed touching down beyond that touchdown point. The tower controller advised the flight crew to be prepared for a go-around if the Airbus did not clear the runway in time, which the flight crew acknowledged. The flight crew estimated that the Airbus had turned off the runway when their airplane was about 1,000 feet from the threshold and about 200 feet above ground level (agl). The flight crew reported having a stabilized approach to their planned landing point. When the airplane was about 150 feet agl and established on the runway centerline, the airplane experienced an uncommanded left roll. The heading swung to the left and the nose dropped. The crew reported that the airplane was buffeting heavily. Immediately, they set full power, and the flying pilot used both hands on the control wheel in an attempt to roll the airplane level and recover the pitch. He managed to get the airplane nearly back to level when the right main gear struck the ground short of the threshold and left of the runway. The airplane collided with a small drainage ditch and a dirt service road, causing the right main gear and the nose gear to collapse. Videos from cameras at the airport recorded the accident sequence, and the accident airplane was about 51 seconds behind the Airbus. A wake vortex study indicated that the accident airplane encountered the Airbus's right vortex, and the airplane's direction of left roll was consistent with the counter-clockwise rotation of the right vortex.

The pilot was en route on a positioning flight when the airplane’s right engine surged and experienced a partial loss of power. He adjusted the power and fuel mixture controls; however, a few seconds later, the engine surged again. The pilot noted that the fuel flow gauge was below 90 pounds, so he turned the right fuel pump on. The pilot then felt a surge on the left engine, so he performed the same actions he as did for the right engine. He believed that he had some sort of fuel starvation problem. The pilot then turned to an alternate airport, at which time both engines lost total power. The airplane impacted trees and terrain about 1.5 miles from the airport. The left side fuel tank was breached during the accident; however, there was no indication of a fuel leak, and about a gallon of fuel was recovered from the airplane during the wreckage retrieval. The company’s route coordinator reported that prior to the accident flight, the pilot checked the fuel gauge and said the airplane had 120 gallons of fuel. A review of the airplane’s flight history revealed that, following the flight immediately before the accident flight, the airplane was left with approximately 50 gallons of fuel on board; there was no record of the airplane having been refueled after that flight. Another company pilot reported the airplane fuel gauge had a unique trait in that, after the airplane’s electrical power has been turned off, the gauge will rise 40 to 60 gallons before returning to zero. When the master switch was turned to the battery position during an examination of another airplane belonging to the operator, the fuel gauge indicated approximately 100 gallons of fuel; however, when the master switch was turned to the off position, the fuel quantity on the gauge rose to 120 gallons, before dropping off scale, past empty. Additionally, the fuel cap was removed and fuel could be seen in the tank, but there was no way to visually verify the quantity of fuel in the tank.

During the 3.5-hour flight preceding the accident flight, the airplane used about 156 gallons of the 196 gallons of usable fuel. After landing, the airplane was topped off with 156 gallons of fuel for the return flight. During the preflight inspection, a line serviceman at the fixed based operator observed the right main fuel tank sump become stuck in the open position. He estimated 5 to 6 gallons of fuel were lost before the sump seal was regained, but the exact amount of fuel lost could not be determined. The lost fuel was not replaced before the airplane departed. Data from an on board GPS unit indicate that the airplane flew the return leg at an altitude of about 4,500 feet mean sea level for about 4 hours. About 4 minutes after beginning the descent to the destination airport, the pilot requested to divert to a closer airport. The pilot was cleared for an approach to runway 18R at the new destination. While on approach to land, the pilot reported to the air traffic control tower controller, “we exhausted fuel.” The airplane descended and crashed into a forested area about 1/2 mile from the airport. Post accident examination of the right and left propellers noted no leading edge impact damage or signatures indicative of rotation at the time of impact. Examination of the airplane wreckage and engines found no malfunctions or failures that would have precluded normal operation. The pilot did not report any problems with the airplane or its fuel state before announcing the fuel was exhausted. His acceptance of the approach to runway 18R resulted in the airplane flying at least 1 mile further than if he had requested to land on runway 18L instead. If the pilot had declared an emergency and made an immediate approach to the closest runway when he realized the exhausted fuel state, he likely would have reached the airport. Toxicological testing revealed cyclobenzaprine and diphenhydramine in the pilot’s system at or above therapeutic levels. Both medications carry warnings that use may impair mental and/or physical abilities required for activities such as driving or operating heavy machinery. The airplane would have used about 186 gallons of fuel on the 4-hour return flight if the engines burned fuel at the same rate as the previous flight. The fuel lost during the preflight inspection and the additional 30 minutes of flight time on the return leg reduced the airplane’s usable fuel available to complete the planned flight, and the pilot likely did not recognize the low fuel state before the fuel was exhausted due to impairment by the medications he was taking.