San Antonio

The pilot reported that, before the flight, the airplane was fueled with 140 gallons of Jet A fuel. Shortly after takeoff, both engines lost total power. Because the airplane had insufficient altitude to return to the airport, the pilot executed a forced landing to a field and the left wing sustained substantial damage. A postcrash fire ensued. The investigation determined that the airplane was inadvertently fueled with Jet A fuel rather than AVGAS, which was required for the airplane’s reciprocating engines. The line service worker who fueled the airplane reported that there were no decals at the airplane fuel ports; however, postaccident examination of the airplane found that a decal specifying AVGAS was present at the right-wing fuel port. The investigation could not determine whether the same or a similar decal was present at the left-wing fuel port because the left wing was partially consumed during the postimpact fire.

The commercial pilot was distracted by the nose cargo door popping open during takeoff; the airplane stalled and collided with trees off the end of the runway. The pilot said there were no mechanical problems with the airplane or engines and that he was fixated on the cargo door and lost control of the airplane. He also said that due to stress, he was not mentally prepared to handle the emergency situation.

The pilot attempted to intercept an instrument landing system localizer three times without success. The pilot told Air Traffic Approach Control that he was having trouble performing a "coupled" approach and that he was trying to "get control" of the airplane. The airplane disappeared from radar, subsequently impacting a field and then a barn. The airplane came to rest in an upright position and a post crash fire ensued. A review of radar and voice data for the flight revealed that during the three approach attempts the pilot was able to turn to headings and climb to altitudes when assigned by air traffic control. Postmortem toxicology results were consistent with the regular use of a prescription antidepressant, and the recent use of a larger-than-maximal dose of an over-the-counter antihistamine known to cause impairment. There were no preimpact anomalies observed during the airframe and engine examinations that would have prevented normal operation.

The twin-engine airplane collided with a residential structure and terrain following a loss of control after the pilot experienced difficulties maintaining course during an Instrument Landing System (ILS) approach while on instrument meteorological conditions. The impact occurred approximately 3.7 miles short of the approach end of the runway. Radar data depicted that after the 8,700-hour commercial pilot was vectored to the ILS Runway 3 approach, the airplane remained left throughout the approach before turning right of the localizer approximately 2 miles before the final approach fix (FAF). Radar then showed the aircraft turn to the left of course line. When the aircraft was abeam the FAF, it was approximately 1 mile left of the course line. As the aircraft closed to approximately 1.5 miles from the runway threshold, the aircraft had veered about 1.3 miles left of the course line (at which time air traffic control instructed the pilot to turn left to a heading of 270 degrees). The aircraft continued to turn left through the assigned heading and appeared to be heading back to the ILS course line. According to the radar, another aircraft was inbound on the ILS course line and Air Traffic Control Tower (ATCT) instructed the pilot to turn left immediately. Thereafter, the aircraft went below radar coverage. A witness, located approximately 1.25 miles northwest of the accident site, reported that he heard a very loud noise, and then observed an airplane flying toward a building, approximately 60 feet in height. The airplane was observed to have pitched-up approximately 45 - 90 degrees just before the building and disappeared into the clouds. A second witness located approximately 1 mile northwest of the accident site reported that he heard a low flying aircraft, and then observed a white twin engine airplane banking left out of the clouds. The airplane leveled out, and flew into the clouds again a few seconds later. The witness stated that the airplane was at an altitude of 100- 200 feet above the ground. A third witness located adjacent to the accident site reported that they heard the sound of a low flying airplane in the distance. As the sound became louder and louder, they looked up and observed the airplane in a near vertical attitude as it impacted trees and the side of an apartment complex. Examination of the airplane did not reveal any preimpact mechanical anomalies. A weather observation taken approximately 15 minutes after the accident included a visibility 4 status miles, light drizzle and mist, and an overcast ceiling at 400 feet.

The corporate jet was in a descent to attain a Mach 0.884 target speed during an airplane type certification flutter test. The airplane (a unique test bed) had a known speed-dependent tendency to roll right which was attributed to wing and aileron twist deviations. As the speed increased during the accident flight, the pilot had to apply full left aileron to be able to maintain airplane control. The airplane completed the test point about 30-degrees right-winglow, and subsequently began to roll to the right, "like a barrel roll...not real fast," that the pilot reported he could not stop. Although the manufacturer’s engineering analysis (which did not include any high-speed wind tunnel testing) predicted positive lateral stability up to Mach 0.90, lateral control was lost during the accident flight, and the airplane rolled about 7 times during a 49-second timeframe, from about 30,500 feet until a near-vertical ground impact. A review of telemetry data revealed that, just before the rolls began, the airplane's elevator moved to the 3.5 degrees trailing-edge-up (TEU) position, and the airplane's heading deviated right. Less than 1 second later, the rudder moved from 2 degrees trailing-edge-left (TEL), to 6.5 degrees TEL, and the combination of the TEU elevator and the left rudder input coincided with a marked increase in airplane's right deviation. Elevator-up deflection and rudder-left defection were maintained, with some variation in magnitude, to nearly the end of the data. Because the known speed-dependent tendency to roll right had created significant control problems on a previous flight, the ailerons were removed, modified and replaced, and a Gurney flap was added to the right wing. After the addition of the Gurney flap, the lateral trim margin improved to about 40 percent required (where 50 percent was neutral) up to 305 KCAS. It was then determined that flutter testing could continue to higher airspeeds if the pilot needed to apply a "small" wheel force to augment the trim. The pilot had been instructed to reduce airspeed if there was a problem during the flutter testing, and had done so during an uncommanded roll to the left on the previous flight. Telemetry data from the accident flight revealed that at initiation of the upset, the pilot attempted to level the wings and raise the nose, but the airplane continued to diverge from stable flight, and it continued to accelerate beyond the airplane’s demonstrated flight diving speed. It is undetermined if the pilot could have reduced the speed of the airplane in time, during the initiation of the upset, so that the airplane would not diverge. After the accident, the company conducted high-speed wind tunnel tests, and found that lateral stability decreased with increasing Mach and angle of attack (AOA). Lateral stability became negative (unstable) above Mach 0.83, and rudder input intended to augment lateral trim above a certain Mach could aggravate the situation. In addition, a TEU elevator input would increase AOA, and also result in deteriorated lateral stability. High speed wind tunnel data also revealed that roll authority deteriorated above Mach 0.86, and by Mach 0.88, the aileron upper and lower surfaces were both in separated flow regions. The follow-on flutter test airplane, which successfully completed the certification requirements, was equipped with vortex generators and thicker trailing-edge ailerons. It also did not require the external trim device needed on the accident airplane due to improvements in manufacturing.

Upon arrival at the destination airport, the commercial pilot of the Part 135 cargo flight reported to the tower that he was 7 miles to the east, intending to land on runway 13. Subsequently, the pilot reported that he would circle the airport a few times "because he was having trouble with his autopilot." After circling, the pilot positioned the airplane on final approach to runway 13. The pilot of another airplane in the traffic pattern observed the accident airplane on a "one to two mile final, in a normal flight attitude but possibly a little low." After looking at her instruments for several seconds, she made visual contact again and observed the airplane impact the ground with the "tail of the aircraft falling forward on top of a fence." She further stated that all of the radio transmissions from the accident airplane were "calm and completely un-alarmed prior to the accident." Another witness, who was located at a fixed base operator at the airport, observed the airplane turn onto final. He stated that the airplane "suddenly stalled and slammed into the ground from about two hundred feet." The 1,140 hour pilot had accumulated a total of 70 hours in the Cessna 402. The airplane was found to be within its prescribed weight and balance limitations at the time of the accident. Ground impressions and airframe deformations indicated that the impact angle was approximately 25 degrees nose down on a magnetic heading of 155 degrees with the landing gear extended and the flaps partially extended. A post-impact fire destroyed the airplane. Flight control continuity was established from the aft section of the cockpit to the rudder and elevator flight control surfaces. The elevator trim tab (located on the right elevator) was measured with a protractor and found to be in the 28 degrees tab-up position (aircraft nose down). According to the airplane manufacturer's specifications, the maximum tab-up travel limit (when connected) is 5 degrees. The trim tab would not move freely by hand forces and appeared to be jammed. The elevator skin was cut open (top side) to observe the trim tab connecting hardware. It was observed that the clevis end of the trim tab actuator rod was wedged against the front spar of the elevator's internal structure. Additionally, the bolt which connected the clevis end of the tab actuator rod to the actuator screw, was missing. After further inspection, neither the bolt nor the nut were found in the cavity of the elevator structure or the surrounding area. The clevis end of the actuator rod and the actuator screw were not damaged, and no impact damage was apparent on the trim tab. The operator's maintenance records showed that the right elevator had been replaced 10 flight hours prior to the accident.

Approximately 8 months prior to the accident, during a cross country flight, the owner shutdown the left engine due to low oil pressure and diverted from his intended destination to a nearby airport. During descent, the right alternator failed, and the owner performed the emergency gear extension procedure. Following an emergency gear extension, the landing gear of this model airplane cannot be retracted until the system has been ground serviced. A mechanic reported that about 7 months prior to the accident, with the owner present, he removed the oil filter from the left engine, found it packed with metal shavings and told the owner that the engine needed overhaul. Two other mechanics reported that approximately three weeks before the accident, they installed an oil filter on the left engine, changed the oil, and cleaned the oil pressure regulator. They ground ran both engines with no discrepancies noted. One of the mechanics reported that following the engine run, the left engine oil filter was removed, examined, and no metal was found. The landing gear was not serviced. According to the owner, the pilot was "hired" by one of the two mechanics to ferry the airplane with the gear extended to a location where the gear could be serviced. While en route, the pilot reported a loss of power on the left engine, that he was having trouble feathering the engine, that the airplane would not maintain altitude and he was looking for a place to land. Witnesses observed the airplane flying low, wheels down and losing altitude. They further observed it roll into a steep left bank, hit trees and a fence, catch fire, come to rest inverted on a road and burn. Post accident examination of the left engine revealed a hole in the right crankcase half over the #3 cylinder attach point. Disassembly of the left engine revealed that the #3 connecting rod was separated from the crankshaft, and the rod bolts, rod cap, and top of the rod were deformed. The #5 piston pin had one cap missing. Scoring was noted on the crankshaft journals, and the main bearings exhibited discoloration and deformation consistent with oil starvation. The cylinders exhibited deformation, scoring in the barrels, and deposits on the domes. The camshaft exhibited discoloration and scoring on the camshaft lobes. Disassembly of the left propeller revealed that it was in the vicinity of low pitch/latch position and not rotating at impact. The disassembly of the right engine and propeller did not reveal any discrepancies that would have precluded operation prior to impact. Estimates of the airplane's climb performance indicated that with the landing gear down and the left propeller stopped, it was not capable of sustained flight.

Witnesses reported that during the airplane's takeoff roll they heard a heard a series of repeated sounds, which they described as similar to a "backfire" or "compressor stall." Several witnesses reported seeing the airplane's right propeller "stopped." One witness reported that as the airplane lifted off the ground, he heard "a loud cracking sound followed by an immediate prop wind down into feather." He continued to watch the airplane, as the gear was retracted and the airplane entered a climb and right turn. Subsequently, the airplane pitched up, entered a "Vmc roll-over," followed by a 360-degree turn, and then impacted the ground. Radar data indicated the airplane took off and climbed on runway heading to a maximum altitude of about 200 feet agl. The airplane than entered a right turn and began to lose altitude. A radar study revealed that the airplane's calibrated airspeed was 97 knots when the last radar return was recorded. According to the flight manual, minimum controllable airspeed (Vmc) was 93 knots. Examination of the accident site revealed that the airplane impacted the ground in a near vertical attitude. A post-crash fire erupted, which destroyed all cockpit instruments and switches. Examination of the propellers revealed that neither of the
propellers were in the feathered position at the time of impact. Examination of the left engine revealed signatures consistent with operation at the time of impact. Examination of the right engine revealed that the second stage impeller shroud exhibited static witness marks indicating that the engine was not operating at the time of impact. However, rotational scoring was also observed through the entire circumference of the impeller shroud. The static witness marks were on top of the rotational marks. Examination of the right engine revealed no anomalies that would have precluded normal operation. The left seat pilot had accumulated a total flight time of about 950 hours of which 16.9 hours were in an MU-2 flight simulator and 4.5 hours were in the accident airplane. Although he had started an MU-2 Pilot-Initial training course, he did not complete the course. The right seat pilot had accumulated a total flight time of about 2,000 hours of which 20.0 hours were in an MU-2 flight simulator and 20.6 hours were in the accident airplane. He had successfully completed an MU-2 Pilot-Initial training course one month prior to the accident.

Following an uneventful flight from San Antonio, the pilot started a night approach to Monterrey-Del Norte. On final in good weather conditions, the twin engine aircraft crashed in unknown circumstances few km from the airfield. Both occupants were killed.