WPR13FA037

The pilot's failure to regain airplane control following a sudden rapid descent during cruise, which resulted in an in-flight breakup. Contributing to the accident was the pilot's decision to make the flight with a failed vacuum pump, particularly at high altitude in night conditions.

The private pilot departed about 90 minutes after sunset in the high-performance multiengine airplane on the cross-country flight. The climb and level off at cruise altitude were uneventful and, based on the radar data, appeared to have been accomplished with the use of the autopilot. The cruise altitude of 27,000 feet was the highest the airplane had been flown in recent history, and the highest altitude it had been operated at with the pilot flying. The pilot made a routine radio exchange with air traffic control personnel shortly after levelling for cruise. Five minutes later, the airplane, with no further radio transmissions, rolled to the right and rapidly descended 10,000 feet, where it subsequently broke apart. Both wings, along with the horizontal stabilizer and elevators, separated during the breakup sequence. Analysis of their fracture surfaces, along with the debris field distribution and radar data, revealed that the breakup sequence was most likely inadvertently induced by the pilot, as he attempted to recover control of the airplane during the dive. The airplane sustained extensive thermal damage after ground impact, and examination of the engine components, surviving primary airframe components, the cabin heater, and the autopilot system remnants did not reveal any mechanical malfunctions or failures that would have precluded normal operation. There was no evidence of bird strike, inflight fire, or that the engine fire extinguisher system had been activated. The airplane was flying toward an uninhabited mountain range and a largely unpopulated desert area at the time of the upset. The moon had set, and the pilot would have had limited reliable external visual cues should the airplane have experienced a failure of either the flight instruments or autopilot. The pilot was instrument rated, however the majority of his flight experience was garnered in aircraft equipped with modern "glass cockpit" avionics, as opposed to the traditional flight instruments installed in the accident airplane (which he had recently purchased). The airplane was equipped with a dual vacuum pump system, which drove the primary flight instruments and, in turn, the autopilot. One of the vacuum pumps had failed on the previous flight, and the pilot was unable to get it repaired in time for the accident flight. The dual nature of the vacuum system allowed for flight with a single failed pump, however failure of the remaining pump or associated vacuum system components would have left the pilot to hand fly the airplane, using backup flight instruments, at an altitude perilously close to the limit of the airplane's flight envelope (the maximum altitude was 30,200 feet). Examination revealed that the second pump was most likely operational; however, fire damage precluded an accurate assessment of the operability of the remaining vacuum system components. Although operation of the airplane did not require adherence to a minimum equipment list, the airplane's FAA Master Minimum Equipment List stated that one of the vacuum pumps can be inoperative, provided the airplane is operated under VFR and not operated at night. Given the pilot's overwhelming experience with "glass cockpit" instruments, as opposed to the traditional type in the accident airplane, along with the failure of one of the vacuum pumps, he should have reconsidered making the flight, particularly during night conditions. The airplane had experienced multiple anomalies with the autopilot and vacuum system prior to the accident flight. Maintenance records indicated that these discrepancies had been resolved; however, damage to the airplane precluded a substantive confirmation of their operation. Additionally, an oversight by an avionics repair facility 1 week before the accident resulted in the airplane's pitot/static system being inadvertently tested and certified to 20,000 feet, rather than the airplane's service ceiling of 30,200 feet. The relevance of this finding, if any, could not be determined. The airplane was equipped with a supplemental oxygen system; however, maintenance records indicated that the pilot's mask, while operational, had degraded. Additionally, the mask had been relocated to a position behind the pilot's seat, which would have been hard to reach in the event of a rapid decompression. Ultimately, the NTSB was unable to determine the cause of the rapid descent because of the postcrash damage to the airplane systems and components.

Full reports for all of the following examinations are contained within the public docket. Engines Both engines were examined by the IIC and representatives from CMI and RAM Aircraft shortly following recovery, and then disassembled and examined at the facilities of CMI in Mobile, Alabama. No anomalies were noted that would have precluded normal operation. Right Engine The right engine remained within its bay. The upper cowling was crushed from impact with the ground from the propeller through to the locker area, and had become formed around the upper surfaces of the engine, turbocharger, and air conditioning system. The locker cover remained attached to the nacelle, and sustained charring damage. All ancillary components including the air inlet manifolds, fuel injection lines, both magnetos, aftercooler, and oil filler neck and dipstick, had become crushed against the upper engine surfaces. The turbocharger assembly remained attached to the airframe within its bay, sustaining crush damage to the induction inlet plenum and exhaust outlet stack. The exhaust outlet tailpipe had sustained crush damage, and had become separated from the turbo exhaust outlet; the ring clamp appeared undamaged, with both its clamping nut and bolt, and braided wire intact. The inlet and exhaust impellors remained interconnected, and could be rotated by hand. All remaining fuel, oil and hydraulic lines within the turbocharger bay were secure at their fittings. Removal of the lower sparkplugs revealed that the plugs for cylinder number one, three, and five were wet with oil, with two, four, and six exhibiting grey and tan deposits. When compared to the Champion Aviation Check-A-Plug chart (AV-27), plugs one, two, five, and six exhibited worn out–normal signatures, with the remaining plugs exhibiting normal signatures. Left Engine The left engine remained within its bay. The upper engine cowling sustained thermal damage in the area above the turbocharger bay, and was crushed along its full length, forming around the upper surfaces of the engine. The lower surface of the engine was covered in black soot. The turbocharger bay sustained extensive thermal damage, which consumed most of the vacuum, fuel, oil, and hydraulic lines. All remaining lines within the turbocharger bay exhibited charring, and fragmented when handled. All unconsumed fittings were finger tight, and no ruptures were noted to any hose braiding. The exhaust pipe had become separated from the turbocharger exhaust outlet; the pipe clamping bolt was not located, and the safety lanyard remained attached but was torn. Examination of the clamping ring revealed that both clamping tabs were bent about 30 degrees relative to their normal plane, with their bolt holes exhibiting cupping and elongation. The lower blades of the turbocharger exhibited inward bending damage, and as such the turbine and assembly impeller could not be rotated. The fuel cap was in place at the locker tank filler neck. The tank had sustained thermal damage, which consumed the majority of its assembly. All ancillary engine components, including the air inlet manifolds, fuel injection lines, both magnetos, aftercooler, and oil filler neck and dipstick, had become crushed against the upper engine surfaces. Removal of the lower sparkplugs revealed that the plugs for cylinders number two and four were wet with oil, with one, three, five, and six exhibiting grey and tan deposits. When compared to the Champion Aviation Check-A-Plug chart (AV-27), plugs one, two, four, and six exhibited worn out–normal signatures, with the remaining plugs exhibiting normal signatures. Airframe An airworthiness group consisting of engineers from both Cessna Aircraft Company and the NTSB Office of Aviation Engineering convened to examine the wreckage at a storage facility, 1 month following the accident. All of the separated components exhibited fracture features consistent with overstress separation, and no evidence of fatigue was noted. There was no evidence of bird-strike, soot patterns, or inflight fire. There was no evidence consistent with flutter. The main wreckage of the airplane consisted of the fuselage, vertical stabilizer, center wing section from outboard of the left nacelle to outboard of the right nacelle, the outboard left and right wing sections, a portion of the right horizontal stabilizer rear spar, and the outboard tip section of the left elevator. Notable items not recovered included the left horizontal stabilizer, most of the left elevator, most of the right horizontal stabilizer, the right elevator, and the majority of the rudder. Outboard Left Wing The outboard left wing was intact from the engine nacelle to the tip; the flap, speed brake, and most of the aileron were separated. The left wing forward and aft spar upper caps were fractured at the root, and had deformed downward. The forward spar lower cap was fractured and deformed with compression buckling. The aft spar web was deformed to the extent that the lower spar cap had been displaced upward to within several inches of the upper spar cap. The wing tip exhibited a slight upwards deformation with upper skin buckling. There was an overall slight upward deformation of the wing beginning about 3 feet from the tip. The aileron was not recovered with the exception of the inboard hinge attach bracket, attached to about 25 inches of forward aileron spar. The outboard aileron hinge fitting was intact, and had deformation on the lower wing skin corner with tree debris embedded between the hinge fitting and the lower wing skin. The aileron trim actuator and connecting rod remained attached to the rear spar of wing. Both aileron cables were broken with a splayed appearance consistent with tension overload about 12 inches inboard of the aileron bell crank. Outboard Right Wing The outboard right wing was intact from the engine nacelle to the tip. The right wing forward spar upper and lower caps, as well as the aft upper cap were fractured at the root and deformed downwards. The aft spar lower cap was fractured and deformed with compression buckling. The wing tip was deformed upward approximately 35 degrees with buckling on both the upper and lower skins. There was a tear in the lower wing tip skin approximately 10 inches in length, about 14 inches aft of leading edge and a blue paint transfer on the upper skin about 2-feet from the nacelle with minor surface scratches. The aileron was still attached, and remained stuck in the trailing edge up position. The upper aileron skin had the appearance of pillowing, and being formed over the ribs and stringers of the aileron. The speedbrake was still attached with no visible damage to the actuator and linkage. The flap was attached; the upper wing skin was damaged above the flap, and about the inboard 14 inches was missing. Horizontal Stabilizer About 75 inches of the right rear horizontal stabilizer spar was recovered. The aft upper and lower spar caps were compressed and deformed towards each other outboard of the center elevator hinge. The upper cap inboard fracture was deformed upward and aft. The lower spar cap inboard fracture was deformed downward and aft. Both forward spar attach bolts and bushings remained attached to the bulkhead, with both exhibiting features consistent with being pulled aft with deformation to the web localized to the areas surrounding the bolts. Vertical Stabilizer and Rudder The vertical stabilizer structure remained attached to the airframe, and was crushed aft and downward. The rudder trim actuator remained attached to the rear spar, and was fractured and damaged. The lower rudder hinge was intact with the rudder attach structure pulled from the rudder. The hinge bolt was found intact. The lower portion of the rudder including a section of the torque tube remained partially attached to the fuselage by the rudder cables. The rudder hinge bolt was found intact and