NTSB Identification: WPR11FA059
14 CFR Part 91: General Aviation
Accident occurred Thursday, November 25, 2010 in Hollister, CA
Probable Cause Approval Date: 05/03/2012
Aircraft: MOONEY M20R, registration: VH-PPA
Injuries: 1 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The pilot departed from the airport for an 11-hour transpacific ferry flight. Recovered GPS data revealed that, during the initial departure, the airplane was climbing on the departure runway heading at a rate of about 500 feet per minute and an airspeed that was high enough to provide for an adequate margin above the stall speed.
About 84 seconds after takeoff, the pilot initiated a left turn toward the first waypoint. During the next 47 seconds, the left turn was completed, and the airplane continued to climb to its maximum altitude of about 1,500 feet above ground level (agl). The airplane began to descend, and about 24 seconds later, it reached a groundspeed of 144 mph and entered a second left turn. Over the remaining 79 seconds of GPS data, the left turn continued with an accompanying series of three diverging groundspeed and altitude oscillations, ending at a groundspeed of 69 mph and an altitude of about 300 feet agl. Witnesses observed the oscillations, which were followed by a spin to the ground.
Ground scars and damage to the airplane were consistent with terrain collision while the airplane was experiencing a flat spin. Postaccident examination revealed no evidence of any airframe or engine failures or malfunctions that would have precluded normal operation. The throttle control was found in the idle position, and the lack of witness marks on the propeller indicated that the engine was operating at low power at the time of impact. These findings are consistent with the spin recovery procedure listed in the Pilot’s Operating Handbook that requires the engine throttle be set to the idle position.
The airplane was equipped with a ferry fuel system consisting of a 238-gallon collapsible bladder tank located in the cabin behind the pilot's seat, above the rear seat pans. At the time of the accident, the bladder tank contained about 121 gallons of additional fuel, which supplemented the 89 gallons carried in the two wing tanks. The ferry system design required that the bladder tank be attached to the fuselage utilizing ratcheting straps. The pilot installed the system 2 days before the accident, and a mechanic inspected the installation. The mechanic reported that he observed yellow tie down straps installed over the bladder tank; however, no straps were found at the accident site, and the tank appeared to be unrestrained.
The ferry system operating instructions required that the fuel selector valve be set to the right tank during takeoff. During the postaccident examination, the valve was found in the left tank position. However, fuel was noted in the engine driven fuel pump, flow divider, and fuel lines forward of the firewall, indicating that the incorrect position of the valve did not result in an interruption to the engine’s fuel supply.
In addition to the extra weight of the fuel in the bladder tank, 187 pounds of unsecured baggage was located behind the tank in the aft baggage area, which had a weight limit of 120 pounds. Although the ferry system design allowed for a one-time, 15 percent increase in Maximum Takeoff Weight (MTOW), the weight of the airplane at the time of the accident was estimated to be about 23 percent beyond the standard MTOW. Additionally, an estimate of the airplane’s center of gravity position at the time of the accident revealed that it was about 0.8 inches beyond the aft center-of-gravity limit. No weight and balance sheet referring to the airplane in the ferry flight configuration was located.
It is likely that the aft loading resulted in the airplane encountering longitudinal instability during the initial left turn and entering a series of altitude and pitch oscillations, which would have been extremely difficult for the pilot to control. Also, the unsecured fuel tank and baggage could have moved during takeoff or after the oscillations began, shifting the center-of-gravity farther aft and exacerbating the longitudinal instability.
The previous owner of the airplane reported that he had experienced autopilot anomalies, with symptoms similar to those observed during the airplane's divergence from controlled flight. However, the autopilot had been repaired about 8 months before the accident, and postaccident examination of the autopilot components revealed no evidence of any anomalies that would have precluded normal operation. Additionally, it is unlikely, given the overweight condition of the airplane, that the pilot would have been utilizing it during takeoff.
The stabilizer pitch trim control system was found near the full nose-up position, a position that, given the airplane’s aft center-of-gravity, would have made pitch control more difficult to maintain. This position could indicate that the pilot may have been utilizing pitch trim in an effort to assist with regaining flight control after the oscillations began.
The autopilot trim failure warning light was illuminated at the time of ground impact, indicating that one of the following conditions existed: the electric trim master switch was not on, the autopilot system had not been preflight tested, an autotrim failure had occurred, or an electric trim fault was detected. If the electric trim master switch was not on, the manual trim system would still have been functional. If the autopilot system had not been preflight tested, the electric and manual trim systems would still have been functional. An autotrim failure would only be significant if the autopilot was engaged, and, as previously discussed, it is unlikely that the pilot was utilizing the autopilot. If the illumination was due to an electric trim fault, the pilot could have opposed any uncommanded movement of the trim with elevator or manual trim input. Additionally, it is unlikely that a runaway trim condition existed, because the trim was not found at either of its end stops. Although the specific condition that resulted in illumination of the warning light could not be determined, none of the possible conditions would have precluded the pilot from maintaining pitch control.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot did not ensure the airplane was loaded within its weight and balance envelope, which resulted in longitudinal instability and a loss of aircraft control during the initial climb. Full narrative available
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