Accident Sequence
On July 23, 2016, about 1900 Pacific daylight time, a Beech 65-A90, registration N256TA, sustained substantial damage following a loss of control while climbing out near Byron Airport (C83) in Byron, California. The commercial pilot and the 14 passengers were not injured. The airplane was registered to N80896 LLC and operated by Bay Area Skydiving under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the skydiving flight. The local flight departed C83 about 1851.
According to the pilot, as the airplane neared the planned jump area and altitude, about 12,500 ft mean sea level, he initiated a left turn to line up for the drop zone. He stated the airplane's airspeed was a little slow and then "suddenly the airplane abruptly stalled, rolled off to the left, and began rotating nose-down." He reported that the airplane "did a couple of downward barrel rolls." One jumper seated in the copilot's seat heard a "loud bang" during the recovery sequence and stated that "the pilot did not retard the throttles during the recovery, causing the airplane to develop too much speed." The jumper further stated that during recovery he felt the g-force on his stomach. The pilot said he temporarily recovered the airplane to a wings-level attitude for a few seconds and observed that the airplane was about 90° off the planned heading and slow in airspeed.
Subsequently, the pilot stated there was a "shock" to the controls and "simultaneously the airplane suddenly broke hard to the left," stalled a second time, and began to rotate downward. The pilot told the skydivers to jump out of the airplane. The parachutists complied, and all of them successfully exited the airplane during this second spin event. The pilot then initiated spin recovery procedures to no apparent effect through about 9 rotations and stated that the roll rate was much more rapid than the first spin event. He then pulled both propeller control levers to the feather position and was able to exit the spin. He recovered the airplane to a wings- and pitch-level attitude, but shortly thereafter the airplane "broke left" and stalled for a third time. The pilot recovered again by lowering the pitch attitude and increasing airspeed.
The pilot turned back toward the airport, and since the airplane was handling abnormally, he adjusted the elevator trim to its full nose-up position to help maintain straight and level flight. He stated that this trim setting was used on the approach, and he flew the approach 15 knots faster than required to compensate for a marked decrease in elevator performance.
The pilot described the landing as being nose-low relative to normal. After landing at C83, a witness observed that the airplane's right horizontal stabilizer, with the attached elevator, was missing. The separated parts were later located in a field a few miles south of the airport.
The pilot reported no abnormalities with the airplane on previous flights that day or during his preflight inspection. He stated that weather was clear with light chop and that no engine issues occurred during the flight.
Postaccident Examination
Postaccident examination revealed that the wing's top and bottom skins were unremarkable. The engine mounts and left horizontal stabilizer attachment points were examined for overstress, but none was observed. No signs of flutter were found on the left horizontal stabilizer.
The separated right horizontal stabilizer, with elevator attached, was examined. The right elevator and elevator trim tab remained attached to their respective attachment points. Fractures were observed on the main and trailing edge horizontal spars on the right horizontal stabilizer, along with some skin wrinkling. The attachment bracket connecting the right stabilizer to the airplane and to the other stabilizer exhibited fracture surfaces on the right side where the stabilizer attached.
Portions of the right horizontal stabilizer, elevator, and attachment bracket were sent to the National Transportation Safety Board Materials Laboratory. Magnified optical examination of fracture surfaces revealed features consistent with overstress separations. No indication of fatigue or corrosion was observed. Deformation and fracture patterns in the right stabilizer spars indicated that the stabilizer tip bent upward, with the lower spar also showing upward tearing of the webs.
The airplane's flight manual spin recovery states: "immediately move the control column full forward, apply full rudder opposite to the direction of the spin, and reduce power on both engines to idle. These three actions should be done as near simultaneously as possible, then continue to hold this control position until rotation stops and then neutralize all controls and execute a smooth pullout. Ailerons should be neutral during recovery."
Weight and Balance
The airplane's weight and balance was calculated for the accident flight. The center of gravity (CG) was estimated to be about 6–7 units aft of the limit. Due to the CG being aft of the limit, the maximum allowable gross weight could not be determined. According to the FAA Pilot Handbook of Aeronautical Knowledge, "as the CG moves aft, a less stable condition occurs, which decreases the ability of the aircraft to right itself after maneuvering or turbulence."