Texas

The pilot and two medical crew members departed on an air ambulance flight in night instrument meteorological conditions to pick up a patient. After departure, the local air traffic controller observed the airplane's primary radar target with an incorrect transponder code in a right turn and climbing through 4,400 ft mean sea level (msl), which was 800 ft above ground level (agl). The controller instructed the pilot to reset the transponder to the correct code, and the airplane leveled off between 4,400 ft and 4,600 ft msl for about 30 seconds. The controller then confirmed that the airplane was being tracked on radar with the correct transponder code; the airplane resumed its climb at a rate of about 6,000 ft per minute (fpm) to 6,000 ft msl. The pilot changed frequencies as instructed, then contacted departure control and reported "with you at 6,000 [ft msl]" and the departure controller radar-identified the airplane. About 1 minute later, the departure controller advised the pilot that he was no longer receiving the airplane's transponder; the pilot did not respond, and there were no further recorded transmissions from the pilot. Radar data showed the airplane descending rapidly at a rate that reached 17,000 fpm. Surveillance video from a nearby truck stop recorded lights from the airplane descending at an angle of about 45° followed by an explosion. The airplane impacted a pasture about 1.5 nautical miles south of the airport, and a post impact fire ensued. All major components of the airplane were located within the debris field. Ground scars at the accident site and damage to the airplane indicated that the airplane was in a steep, nose-low and wings-level attitude at the time of impact. The airplane's steep descent and its impact attitude are consistent with a loss of control. An airplane performance study based on radar data and simulations determined that, during the climb to 6,000 ft and about 37 seconds before impact, the airplane achieved a peak pitch angle of about 23°, after which the pitch angle decreased steadily to an estimated -42° at impact. As the pitch angle decreased, the roll angle increased steadily to the left, reaching an estimated -76° at impact. The performance study revealed that the airplane could fly the accident flight trajectory without experiencing an aerodynamic stall. The apparent pitch and roll angles, which represent the attitude a pilot would "feel" the airplane to be in based on his vestibular and kinesthetic perception of the components of the load factor vector in his own body coordinate system, were calculated. The apparent pitch angle ranged from 0° to 15° as the real pitch angle steadily decreased to -42°, and the apparent roll angle ranged from 0° to -4° as the real roll angle increased to -78°. This suggests that even when the airplane was in a steeply banked descent, conditions were present that could have produced a somatogravic illusion of level flight and resulted in spatial disorientation of the pilot. Analysis of the performance study and the airplane's flight track revealed that the pilot executed several non-standard actions during the departure to include: excessive pitch and roll angles, rapid climb, unexpected level-offs, and non-standard ATC communications. In addition to the non-standard actions, the pilot's limited recent flight experience in night IFR conditions, and moderate turbulence would have been conducive to the onset of spatial disorientation. The pilot's failure to set the correct transponder code before departure, his non-standard departure maneuvering, and his apparent confusion regarding his altitude indicate a mental state not at peak acuity, further increasing the chances of spatial disorientation. A post accident examination of the flight control system did not reveal evidence of any preimpact anomalies that would have prevented normal operation. The engine exhibited rotational signatures indicative of engine operation during impact, and an examination did not reveal any preimpact anomalies that would have precluded normal engine operation. The damage to the propeller hub and blades indicated that the propeller was operating under high power in the normal range of operation at time of impact. Review of recorded data recovered from airplane's attitude and heading reference unit did not reveal any faults with the airplane's attitude and heading reference system (AHRS) during the accident flight, and there were no maintenance logbook entries indicating any previous electronic attitude director indicator (EADI) or AHRS malfunctions. Therefore, it is unlikely that erroneous attitude information was displayed on the EADI that could have misled the pilot concerning the actual attitude of the airplane. A light bulb filament analysis of the airplane's central advisory display unit (CADU) revealed that the "autopilot disengage" caution indicator was likely illuminated at impact, and the "autopilot trim" warning indicator was likely not illuminated. A filament analysis of the autopilot mode controller revealed that the "autopilot," "yaw damper," and "altitude hold" indicators were likely not illuminated at impact. The status of the "trim" warning indicator on the autopilot mode controller could not be determined because the filaments of the indicator's bulbs were missing. However, since the CADU's "autopilot trim" warning indicator was likely not illuminated, the mode controller's "trim" warning indicator was also likely not illuminated at impact. Exemplar airplane testing revealed that the "autopilot disengage" caution indicator would only illuminate if the autopilot had been engaged and then disconnected. It would not illuminate if the autopilot was off without being previously engaged nor would it illuminate if the pilot attempted and failed to engage the autopilot by pressing the "autopilot" push button on the mode controller. Since the "autopilot disengage" caution indicator would remain illuminated for 30 seconds after the autopilot was disengaged and was likely illuminated at impact, it is likely that the autopilot had been engaged at some point during the flight and disengaged within 30 seconds of the impact; the pilot was reporting to ATC at 6,000 ft about 30 seconds before impact and then the rapid descent began. The airplane was not equipped with a recording device that would have recorded the operational status of the autopilot, and the investigation could not determine the precise times at which autopilot engagement and disengagement occurred. However, these times can be estimated as follows:
- The pilot likely engaged the autopilot after the airplane climbed through 1,000 ft agl about 46 seconds after takeoff, because this was the recommended minimum autopilot engagement altitude that he was taught.
- According to the airplane performance study, the airplane's acceleration exceeded the autopilot's limit load factor of +1.6 g about 9 seconds before impact. If it was engaged at this time, the autopilot would have automatically disengaged.
- The roll angle data from the performance study were consistent with engagement of the autopilot between two points:
1) about 31 seconds before impact, during climb, when the bank angle, which had stabilized for a few seconds, started to increase again and
2) about 9 seconds before impact, during descent, at which time the autopilot would have automatically disengaged. Since the autopilot would have reduced the bank angle as soon as it was engaged and there is no evidence of the bank angle reducing significantly between these two points, it is likely that the autopilot was engaged closer to the latter point than the former. Engagement of the autopilot shortly before the latter point would have left little time for the autopilot to reduce the bank angle before it would have disengaged automatically due to exceedance of the normal load factor limit. Therefore, it is likely that the pilot engaged the autopilot a few seconds before it automatically disconnected about 9 seconds before impact. The operator reported that the airplane had experienced repeated, unexpected, in-flight autopilot disconnects, and, two days before the accident, the chief pilot recorded a video of the autopilot disconnecting during a flight. Exemplar airplane testing and maintenance information revealed that, during the flight in which the video was recorded, the autopilot's pitch trim adapter likely experienced a momentary loss of power for undetermined reasons, which resulted in the sequence of events observed in the video. It is possible that the autopilot disconnected during the accident flight due to the pitch trim adapter experiencing a loss of power, which would have to have occurred between 30 and 9 seconds before impact. A post accident weather analysis revealed that the airplane was operating in an environment requiring instruments to navigate, but it could not be determined if the airplane was in cloud when the loss of control occurred. The sustained surface wind was from the north at 21 knots with gusts up to 28 knots, and moderate turbulence existed. The presence of the moderate turbulence could have contributed to the controllability of the airplane and the pilot's inability to recognize the airplane's attitude and the autopilot's operational status.

While conducting a post maintenance test flight in visual flight rules conditions, the private pilot of the multi-engine airplane reported an oil leak to air traffic control. The controller provided vectors for the pilot to enter a right base leg for a landing to the south at the nearest airport, about 7 miles away. The pilot turned toward the airport but indicated that he did not have the airport in sight. Further, while maneuvering toward the airport, the pilot reported that the engine was "dead," and he still did not see the airport. The final radar data point recorded the airplane's position about 3.5 miles west-northwest of the approach end of the runway; the wreckage site was located about 4 miles northeast of the runway, indicating that the pilot flew past the airport rather than turning onto a final approach for landing. The reason that the pilot did not see the runway during the approach to the alternate airport, given that the airplane was operating in visual conditions and the controller was issuing guidance information, could not be determined. Regardless, the pilot did not execute a precautionary landing in a timely manner and lost control of the airplane. Examination of the airplane's left engine revealed that the No. 2 connecting rod was broken. The connecting rod bearings exhibited signs of heat distress and discoloration consistent with a lack of lubrication. The engine's oil pump was intact, and the gears were wet with oil. Based on the available evidence, the engine failure was the result of oil starvation; however, examination could not identify the reason for the starvation.

The pilot executed an instrument approach and landing in heavy rain. The airplane touched down about 21 knots above the applicable landing reference speed, which was consistent with an unstabilized approach. The airplane touched down near the displaced runway threshold about 128 kts, and both wing ground spoilers automatically deployed. The pilot reported that the airplane touched down “solidly,” and he started braking promptly, but the airplane did not slow down. The main wheels initially spun up; however, both wheel speeds subsequently decayed consistent with hydroplaning in the heavy rain conditions. When the wheel speeds did not recover, the brake control unit advised the flight crew of an anti-skid failure; the pilot recalled an anti-skid CAS message displayed at some point during the landing. The pilot subsequently activated the emergency brake system and the wheel speeds decayed. The airplane ultimately overran the departure end of the runway about 60 kts, crossed an airport perimeter road, and encountered a small creek before coming to rest. The wings had separated from, and were located immediately adjacent to, the fuselage. The pilot reported light to moderate rain began on final approach. Weather data and surveillance images indicated that heavy rain and limited visibility prevailed at the airport during the landing. Thunderstorms were active in the vicinity and the rainfall rate at the time of the accident landing was between 4.2 and 6.0 inches per hour. About 4 minutes before the accident, a surface observation recorded the visibility as 3 miles. However, 3 minutes later, the observed visibility had decreased to 3/8 mile. A review of the available information indicated that the tower controller advised the pilot of changing wind conditions and of better weather west of the airport but did not update the pilot regarding visibility along the final approach course or precipitation at the airport. The pilot stated that the rain started 2 to 3 minutes before he landed and commented that it was not the heaviest rain that he had ever landed in. The pilot was using the multifunction display and a tablet for weather radar, which showed green and yellow returns indicating light to moderate rain during the approach. He chose not to turn on the airplane’s onboard weather radar because the other two sources were not indicating severe weather. The runway exhibited skid marks beginning about 1,500 ft from the departure end and each main tire had one patch of reverted rubber wear consistent with reverted rubber hydroplaning. The main landing gear remained extended and both tires remained pressurized. The tire pressures corresponded to a minimum dynamic hydroplaning speed of about 115 kts. The airplane flight manual noted that, in the case of an antiskid failure, the main brakes are to be applied progressively and brake pressure is to be modulated as required. The emergency brake is to be used in the event of a brake failure; however, the pilot activated the emergency brake when the main brakes still functioned; although, without anti-skid protection.

The pilot reported that he was landing in gusty crosswind conditions following a parachute jump flight, and that the gusty conditions had persisted for the previous 10 skydiving flights that day. The pilot further reported that during the landing roll, when the nose wheel touched down, the airplane became "unstable" and veered to the left. He reported that he applied right rudder and added power to abort the landing, but the airplane departed the runway to the left and the left wing impacted a tree. The airplane spun 180 degrees to the left and came to rest after the impact with the tree. The left wing was substantially damaged. The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation.

The private pilot, who was the owner of the airplane, and a flight instructor were performing a recurrent training flight. Radar data showed that the airplane departed and climbed to an altitude about 5,000 ft above ground level. About 5 minutes after takeoff, the airplane conducted a left 360° turn followed by a right 360° turn, then continued in level flight for about 2 minutes as it slowed to a groundspeed of about 90 knots, which may have been indicative of airwork leading to slow flight or stall maneuvers. The airplane then entered a steep bank and impacted the ground in a nose-low attitude. Both engines and propellers displayed evidence of operation at the time of impact, and postaccident examination revealed no mechanical anomalies that would have precluded normal operation of the airframe or engines. The instructor had a history of obstructive sleep apnea. The investigation was unable to determine how well the condition was controlled, if he had symptoms from the condition, or if it contributed to the accident. Toxicology testing revealed low levels of ethanol in specimens from both pilots; however, it is likely that some or all of the ethanol detected was a result of postmortem production, and it is unlikely that alcohol impairment contributed to the accident. Toxicology testing also detected the primary psychoactive compound of marijuana, tetrahydrocannabinol (THC), and its metabolite, tetrahydrocannabinol carboxylic acid (THCCOOH), in specimens obtained from comingled remains; the investigation was unable to reliably determine which pilot had used the impairing illicit drug. Additionally, it is not possible to determine impairment from tissue specimens; therefore, the investigation was unable to determine whether THC impaired either of the pilots or if it may have contributed to the accident.

The instrument-rated commercial pilot was approaching the destination airport after a cross country flight in night instrument meteorological conditions. According to radar track data and air traffic control communications, while receiving radar vectors to the final approach course, the pilot did not always immediately comply with assigned headings and, on several occasions, allowed the airplane to descend below assigned altitudes. According to airplane performance calculations based on radar track and GPS data, the pilot made an engine power reduction about 2.5 minutes before the accident as he maneuvered toward the final approach fix. Following the engine power reduction, the airplane's airspeed decreased from 162 to 75 knots calibrated airspeed, and the angle of attack increased from 2.7° to 14°. About 4 miles from the final approach fix, the airplane descended below the specified minimum altitude for that segment of the instrument approach. The tower controller subsequently alerted the pilot of the airplane's low altitude, and the pilot replied that he would climb. At the time of the altitude alert, the airplane was 500 ft below the specified minimum altitude of 2,000 ft mean sea level. According to airplane performance calculations, 5 seconds after the tower controller told the pilot to check his altitude, the pilot made an abrupt elevator-up input that further decreased airspeed, and the airplane entered an aerodynamic stall. A witness saw the airplane abruptly transition from a straight-and-level flight attitude to a nose-down, steep left bank, vertical descent toward the ground, consistent with the stall. Additionally, a review of security camera footage established that the airplane had transitioned from a wings-level descent to a near vertical spiraling descent. A post accident examination of the airplane did not reveal any anomalies that would have precluded normal operation during the accident flight. Although the pilot had monocular vision following a childhood injury that resulted in very limited vision in his left eye, he had passed a medical flight test and received a Statement of Demonstrated Ability. The pilot had flown for several decades with monocular vision and, as such, his lack of binocular depth perception likely did not impede his ability to monitor the cockpit instrumentation during the accident flight. The pilot had recently purchased the airplane, and records indicated that he had obtained make and model specific training about 1 month before the accident and had flown the airplane about 10 hours before the accident flight. The pilot's instrument proficiency and night currency could not be determined from the available records; therefore, it could not be determined whether a lack of recent instrument or night experience contributed to the pilot's difficulty in maintaining control of the airplane.

The instrument-rated private pilot was conducting a personal cross-country flight in the airplane. A review of the air traffic control transcripts and radar data revealed that the pilot was executing the RNAV GPS Y instrument approach to the runway. The air traffic controller then canceled the pilot's approach clearance and issued a heading change off of the approach course to provide spacing between a preceding aircraft. The pilot acknowledged the heading assignment. Radar data indicated that, after the controller cancelled the approach, the airplane began a left climbing turn from 5,600 to 5,800 ft, continued the left turn through the assigned 270 heading, and then descended rapidly. At that point, the airplane was no longer visible on the controller's radar display, and contact with the pilot was lost. The final recorded radar return showed the airplane at 5,100 ft. The airplane impacted a television tower guy wire, several power lines, and terrain, and then came to rest in an open field about 800 ft from the tower. A postaccident examination of the airplane and engine revealed no anomalies that would have precluded normal operation. A postaccident examination of the engine revealed rotational signatures on the first stage compressor blades and light rotational signatures in the compressor and power turbines, and debris was found in the engine's gas path, all of which are consistent with engine rotation at impact. A witness in the parking lot next to the television tower stated that he heard the accident airplane overhead, saw a large flash of light that filled his field of view, and then observed the television tower collapse on top of itself. Surveillance videos located 1.5 miles north-northeast and 0.3 mile north-northwest of the accident site showed the airplane in a left descending turn near the television tower. After it passed the television tower, multiple bright flashes of light were observed, which were consistent with the airplane impacting the television tower guy wire and then the power lines. Further, the radar track and accident wreckage were consistent with a rapid, descending left turn to impact. Weather conditions were conducive to the accumulation of ice at the destination airport about the time that the pilot initiated the left turn. It is likely that the airplane accumulated at least light structural icing during the descent and that this affected the airplane's controllability. Also, the airplane likely encountered wind gusting up to 31 knots as it was turning; this also could have affected the airplane's controllability. The night, instrument meteorological conditions at the time of the accident were conducive to the development of spatial disorientation, and the airplane's rapid, descending left turn to impact is consistent with the pilot's loss of airplane control due to spatial disorientation. Therefore, based on the available evidence, it is likely that, while initiating the climbing left turn, the pilot became spatially disoriented, which resulted in his loss of airplane control and his failure to see and avoid the tower guy wire, and that light ice accumulation on the airplane and the gusting wind negatively affected the airplane's controllability.

The airline transport pilot was conducting a cross-country repositioning flight. While en route to the destination airport, the pilot contacted air traffic control and stated that he was beginning to descend. No further radio transmissions were made by the pilot. Radar and GPS information showed, about the same time as the pilot's last transmission, the airplane's flightpath began descending in a westerly direction. The last recorded GPS point showed the airplane about 200 ft southwest of the initial impact point, 90 ft above ground level, and at a groundspeed of 66 knots. The airplane wreckage was located in an open field and impact signatures were consistent with a stall/spin, which had resulted in a near-vertical impact at a slow airspeed. The right propeller blades were found in the feathered position. Examination of the right engine found that the oil gauge housing extension was improperly secured to the oil gauge housing, which resulted in a loss of engine oil. Additionally, the examination revealed a hole in the right engine's crankcase, metal material in the oil sump, and signatures consistent with the lack of lubrication. Cockpit switches were positioned in accordance with the in-flight shutdown of the right engine. No anomalies were found with the left engine or airframe that would have precluded normal operation. Another pilot who had flown with the accident pilot reported that the pilot typically used the autopilot, and the autopilot system was found with the roll, heading, and pitch modes active. During the descent, no significant changes of heading were recorded, and the direction of travel before the stall was not optimal for the airplane to land before a fence line. It is likely that the autopilot was controlling the airplane's flightpath before the stall. Despite one operating engine, the pilot did not maintain adequate airspeed and exceeded the airplane's critical angle-of-attack (AOA), which resulted in an aerodynamic stall/spin. Correcting the last GPS recorded airspeed for prevailing wind, the airplane's indicated airspeed would have been about 72 knots, which is above the airplane's 0-bank stall speed, but an undetermined mount of bank would have been applied to maintain heading, which would have accelerated the stall speed. It could not be determined why the pilot did not maintain adequate airspeed or notify air traffic controller of an engine problem. Although a review of the pilot's medical records revealed that he had several historical medical conditions and the toxicology tests detected several sedating allergy medications in his system, it was inconclusive whether the medical conditions or medications impaired the pilot's ability to fly the airplane or if the pilot was incapacitated. It is also possible that the pilot was distracted by the loss of oil from the right engine and that this resulted in his failure to maintain adequate airspeed, his exceedance of the airplane's critical AOA, and a subsequent stall/spin; however, based on the available evidence, the investigation could not determine the reason for the pilot's lack of corrective actions.

The pilots of the very light jet were conducting a positioning flight in instrument meteorological conditions. The flight was cleared by air traffic control for the instrument landing system (ILS) approach; upon being cleared for landing, the tower controller reported to the crew that there was no standing water on the runway. Review of the airplane's flight data recorder (FDR) data revealed that the airplane reached 50 ft above touchdown zone elevation (TDZE) at an indicated airspeed of 118 knots (KIAS). The airplane crossed the runway displaced threshold about 112 KIAS, and it touched down on the runway at 104 KIAS with about a 7-knot tailwind. FDR data revealed that, about 1.6 seconds after touchdown of the main landing gear, the nose landing gear touched down and the pilot's brake pedal input increased, with intermediate oscillations, over a period of 7.5 seconds before reaching full pedal deflection. During this time, the airplane achieved its maximum wheel braking friction coefficient and deceleration. The cockpit voice recorder recorded both pilots express concern the that the airplane was not slowing. About 4 seconds after the airplane reached maximum deceleration, the pilot applied the emergency parking brake (EPB). Upon application of the EPB, the wheel speed dropped to zero and the airplane began to skid, which resulted in reverted-rubber hydroplaning, further decreasing the airplane's stopping performance. The airplane continued past the end of the runway, crossed a service road, and came to rest in a drainage ditch. Postaccident examination of the brake system and data downloaded from the brake control unit indicated that it functioned as commanded during the landing. The airplane was not equipped with thrust reversers or spoilers to aid in deceleration. The operator's standard operating procedures required pilots to conduct a go-around if the airspeed at 50 ft above TDZE exceeded 111 kts. Further, the landing distances published in the airplane flight manual (AFM) are based on the airplane slowing to its reference speed (Vref) of 101 KIAS at 50 ft over the runway threshold. The airplane's speed at that time exceeded Vref, which resulted in an increased runway distance required to stop; however, landing distance calculations performed in accordance with the AFM showed that the airplane should still have been able to stop on the available runway. An airplane performance study also showed that the airplane had adequate distance available on which to stop had the pilot continued to apply maximum braking rather than engage the EPB. The application of the EPB resulted in skidding, which increased the stopping distance. Although the runway was not contaminated with standing water at the time of the accident, the performance study revealed that the maximum wheel braking friction coefficient was significantly less than the values derived from the unfactored wet runway landing distances published in the AFM, and was more consistent with the AFM-provided landing distances for runways contaminated with standing water. Federal Aviation Administration Safety Alert for Operators (SAFO) 15009 warns operators that, "the advisory data for wet runway landings may not provide a safe stopping margin under all conditions" and advised them to assume "a braking action of medium or fair when computing time-of-arrival landing performance or [increase] the factor applied to the wet runway time-of-arrival landing performance data." It is likely that, based on the landing data in the AFM, the crew expected a faster rate of deceleration upon application of maximum braking; when that rate of deceleration was not achieved, the pilot chose to engage the EPB, which only further degraded the airplane's braking performance.

Witnesses reported observing the airplane flying slowly toward the airport at a low altitude. The left engine was at a low rpm; "sputtering," "knocking," or making a "banging" noise; and trailing black smoke. One witness said that, as the airplane passed over his location, he saw the tail "kick" horizontally to the right and the airplane bank slightly left. The airplane subsequently collided with trees and impacted a field 1/2 mile north of the airport. Disassembly of the right engine revealed no anomalies, and signatures on the right propeller blades were consistent with power and rotation on impact. The left propeller was found feathered. Disassembly of the left engine revealed that the spark plugs were black and heavily carbonized, consistent with a rich fuel-air mixture; the exhaust tubing also exhibited dark sooting. The rubber boot that connected the intercooler to the fuel injector servo was found dislodged and partially sucked in toward the servo. The clamp used to secure the hose was loose but remained around the servo, the safety wire on the clamp was in place, and the clamp was not impact damaged or bent. The condition of the boot and the clamp were consistent with improper installation. The time since the last overhaul of the left engine was about 1,050 hours. The last 100-hour inspection occurred 3 months before the accident, and the airplane had been flown only 0.8 hour since then. It could not be determined when the rubber boot was improperly installed. Although the left engine had failed, the pilot should have been able to fly the airplane and maintain altitude on the operable right engine, particularly since he had appropriately feathered the left engine.