SAN DIEGO, CA, USA
N266MM
Piper PA 31-310
The aircraft concluded an aerial survey and landed at Brown Field to clear U.S. Customs. On restart, as the left engine began running, a witness noticed two short, yellow flame bursts exit the exhaust. During taxi, the witness heard a popping sound coming from the aircraft. As power was applied to cross runway 26L, the sound went away. The aircraft stopped for a few seconds prior to pulling onto the runway; the witness did not observe or hear a run-up. Witnesses reported hearing a series of popping sounds similar to automatic gunfire and observed the aircraft between 600 and 1,000 feet above the ground with wings level and the landing gear up. The aircraft was observed to make an abrupt, 45-degree banked, left turn as the nose dipped down. Witnesses reported the nose of the aircraft then raised up toward the horizon. This was followed by the aircraft turning to the left and becoming inverted in an estimated 30-degree nose low attitude. With the nose still low, the aircraft continued around to an upright position and appeared to be in a shallow right bank. Witnesses then lost sight of the aircraft due to buildings and terrain. A May 20, 1997, work order indicated the left manifold pressure fluctuated in flight. Both wastegates were lubricated and a test flight revealed the left engine manifold pressure lagged behind the right engine manifold pressure. On June 18, 1997, the left engine differential pressure controller was noted to have been removed and replaced. This was the corrective action for a discrepancy write up that the left engine manifold pressure fluctuated up and down 2 inHg and the rpm varied by 100 in cruise. A test flight that afternoon by the accident pilot indicated the discrepancy still occurred at cruise power settings, but the engine operated normally at high and low power settings. Postaccident functional checks were performed on various components. No discrepancies were noted for the left governor. The left engine differential pressure controller was damaged and results varied on each test. The left density controller was too damaged to test. The right engine density and differential pressure controllers tested satisfactory. The left and right fuel pumps operated within specifications. Both fuel servos were damaged. One injection nozzle on the left engine was partially plugged; all others flow tested within specifications.
HISTORY OF FLIGHT On June 20, 1997, at 1231 hours Pacific daylight time, a Piper PA 31-310 (Navajo), N266MM, was destroyed when it collided with terrain approximately 1 minute after takeoff from Brown Field, San Diego, California. The airplane was being operated as an other work use flight under the provisions of 14 CFR Part 91 by San-Lo Aerial Surveys, Inc. The airline transport pilot, a second pilot, and the camera operator were fatally injured. The flight was destined for Montgomery Field, also in San Diego. Visual meteorological conditions prevailed and no flight plan was filed. Company documents found in the aircraft indicated one aerial survey job had been completed. Notations on the document were 1130, 1220, Brown Field, and 1230. End time for the camera run was listed as 1212. A witness stated he observed the aircraft's three-man crew in the U. S. Customs office as he passed by. He stopped at a nearby fence to rest and noticed the three men exit the customs office and board a Piper Navajo that was white with red/ burgundy trim. Several minutes later he heard an engine starting. He turned and observed that the Navajo's right engine was running and the left engine was turning over. He stated that immediately after the left engine was running on its own he observed two short flame bursts exit the exhaust. It seemed odd to him since he had never observed that during daylight before. He described the flame as a very light yellow, almost white. At this time, the engine made no unusual sounds. Transcripts of Federal Aviation Administration (FAA) communications with the aircraft indicate N266MM was cleared by the ground controller to taxi to runway 26R at 1229:47. After the aircraft started to taxi and made several 90-degree turns, the witness noted he heard a "popping" sound coming from the plane. When power was added as it crossed the left runway, the popping sound went away and it sounded "normal." He observed the aircraft stop just short of runway 26R. After what seemed like a few seconds to him, the aircraft pulled onto the runway and takeoff power was applied. He did not observe or hear a run-up prior to the aircraft's departure. The air traffic control tower cleared N266MM for a downwind departure to the east on runway 26R at intersection bravo at 1230:52. Witnesses reported hearing a series of popping sounds similar to automatic gunfire and observed the Navajo at what they estimated to be between 600 and 1,000 feet above ground level. One witness noted the wings were level and the landing gear were up. The aircraft was observed to make an abrupt left turn. The right wing was up about 45 degrees, and the nose dipped down. Witnesses reported the nose of the aircraft raised up toward the horizon. Then the aircraft was observed to turn to the left and become inverted in an estimated 30-degree nose low attitude. With the nose still low, the aircraft continued around to an upright position and appeared to be in a shallow right bank. Witnesses then lost sight of the aircraft behind buildings and terrain. A handheld global positioning system (GPS) unit indicated the aircraft wreckage was at 32 degrees 34.25 minutes north latitude and 117 degrees 00.24 minutes west longitude. The GPS altitude indicated 524 feet. PERSONNEL INFORMATION Review of FAA Airman Records indicate the first pilot held an airline transport pilot certificate with a airplane multiengine land rating and commercial privileges for single engine land airplanes. The pilot also held a type rating for the CE-500. Information supplied by the pilot to the insurance carrier indicated that he had accumulated over 10,000 flight hours. Four thousand were in U.S. Marine Corps fighter attack aircraft. He had over 4,600 hours in multiengine aircraft; over 1,500 hours were in the PA-31 model. The form indicated he had flown more than 340 hours in the previous 12 months; 70 of those hours were in the last 90 days. These records also indicate a biennial flight review occurred March 5, 1997, during 14 CFR Part 135 recurrent training. A second class medical was issued on May 29, 1997, with the limitation that the pilot must have glasses available for near vision. The second pilot was occupying the left seat. FAA airman records files disclosed that he held a commercial pilot certificate with ratings for single and multiengine land airplanes, and instrument privileges in single engine airplanes. The pilot's multiengine class rating was endorsed with the limitation "multiengine limited to VFR only". The most recent issuance of the certificate was dated June 9, 1997. The pilot's second class medical certificate was dated February 21, 1997, and contained the limitation that corrective lenses must be worn. Information supplied to the insurance carrier indicated he had over 7,400 flight hours. Forty-four hours were in multiengine aircraft, with 15 hours accrued in the PA-31 model. AIRCRAFT INFORMATION FAA records indicate N266MM was a 1968 Piper PA-31-310 Navajo, serial number 31-140. A registration was issued to San-Lo Aerial Surveys, San Diego, on May 20, 1997. The standard airworthiness certificate was issued on September 15, 1995. Examination of the aircraft's logbooks indicated the left engine was a Textron Lycoming, model TIO-540-A2A (converted from an A1A), serial number L-4468-61. Total time on the engine was 3,829.8 hours and time since overhaul was 827.6 hours. The right engine was a Textron Lycoming, model TIO-540-A2B, serial number L-8244-61A. It was overhauled by Textron Lycoming in October 1993. Total engine time was 5,612.7, and time since major overhaul was 270.7 hours. Aircraft total time was 8,473 hours. Eighty hours had been flown since the last annual inspection performed on September 27, 1996. An aerial camera kit hole was installed in N266MM on April 22, 1997. An entry in the aircraft logbooks on December 6, 1996 indicates the left differential pressure controller was removed and replaced at a Hobbs time of 6,028.2. A maintenance work order dated May 30, 1997 noted a Hobbs meter reading of 6,045.5 was replaced by a unit reading 0.0. This work order also indicated the left manifold pressure fluctuated in flight. Both wastegates were lubricated and the accident pilot flew a test flight on May 30, 1997. Maintenance write-ups after the flight indicated the throttles would stick in the closed position, the right tachometer was erratic, and the left manifold pressure lagged behind the right manifold pressure above 4,000 feet. The pilot requested an inspection of the throttle control system. The maintenance manager stated the right engine throttle arm was repositioned and the throttle cable rod end was adjusted for full travel. Additionally, the left propeller dome pressure was measured at 30 psi and serviced to the prescribed 41, plus and minus 1 psi. Maintenance records dated June 18, 1997 indicate the left engine differential pressure controller was removed and replaced with an overhauled unit at Hobbs time 16.9. This was the corrective action for a discrepancy, which indicated the left engine manifold pressure fluctuated up and down 2 inHg, and the rpm varied by 100 rpm in cruise. It was noted that the rpm and manifold pressure operated normally at high and low power settings. The maintenance manager stated the aircraft was flown in the afternoon on the 18th by the accident pilot; the erratic readings persisted. He stated that on June 20, 1997, the propeller dome pressures were checked and were 40 psi on both sides. A fuel truck operator stated that he serviced N266MM with 92.1 gallons of fuel at 1100 on June 20, 1997. He stated the fuel was distributed evenly between the left and right wings and all four tanks were fueled. He stated the daily checklist had been followed when the truck was put in service. All checklist items were normal and the fuel was observed to be clear and bright. The aircraft manufacturer's representative computed the weight and balance for the aircraft based on the aircraft's weight and balance sheet and published camera weight. His estimate of the fuel load took into account the fuel truck operator's statement, the document found in the aircraft indicating an earlier flight, and an assumption of 0.8 hours of flight time at 75 percent power. His computed total weight was 6,106.96 pounds and the center of gravity computed to be 130.8645 inches. The type certificate data sheet for the aircraft indicated a maximum certified gross weight of 6,500 pounds. Type certificate data indicated the forward enter of gravity limit was along a straight line from 128.5 inches at 6,000 pounds to 134 inches at 6,500 pounds. The aft center of gravity limit was listed as 138 inches for all weights. METEOROLOGICAL INFORMATION A METAR (aviation routine weather report) for Brown Field at 1230 indicated that the skies were clear; visibility was 10 statute miles with haze. Winds were from 250 degrees at 11 knots; the barometric pressure was 29.93 inHg. Temperature and dew point were 73 and 59 degrees Fahrenheit respectively. COMMUNICATIONS Transcripts of recorded FAA air-to-ground communications revealed that Brown ground control was contacted on frequency 124.4 at 1229:47. Taxi clearance was issued to runway 26R, charlie intersection, 6,000 feet remaining. At 1230:07, N266MM requested departure from intersection bravo and it was approved. The aircraft contacted Brown tower on frequency 126.5 at 1230:38 for takeoff with a downwind departure. At 1230:45, the local controller asked for verification of a right downwind departure to the east and received an unidentified "affirm" at 1230:50. At 1230:52, the controller cleared the Navajo for departure. No further communications were received from the aircraft. The controller stated he cleared N266MM for departure, observed the takeoff roll, and watched it become airborne. He scanned out his window to the north and then scanned his radar screen for any potential traffic. When he looked back, he observed the Navajo left of where he expected it to be in a left downward spiral. At 1233:27, the local fire department was notified. AERODROME INFORMATION Information in the airport/facility directory, southwest U. S., indicates Brown Field Municipal Airport has a field elevation of 524 feet and two parallel runways. Runway 08R-26L was a 3,032 by 70-foot asphalt runway; 26L terminated at taxiway bravo. Runway 08L-26R was a 7,999 by 200-foot asphalt and concrete runway. As measured from the airport diagram, approximately 3,000 feet remained available for takeoff from intersection bravo on runway 26R. The airport diagram indicated an effective gradient of 0.24 percent upslope for 26R. WRECKAGE AND IMPACT INFORMATION A ground scar, beginning about 50 feet downslope on the side of a gorge, continued downhill nearly 50 feet, ending at the wreckage site. The ground scar was along a bearing of 218 degrees. The fuselage was aligned on a heading of 276 degrees. A handheld GPS indicated the site was 1.5 statute miles from Brown Field on a bearing of 259 degrees at an elevation of 524 feet. The aircraft came to rest canted on its left side and propped up by the left horizontal stabilizer. The empennage exhibited twisting and buckling in the section immediately below the leading edge of the horizontal stabilizer. Both elevators and the rudder remained attached to their respective surfaces. The right horizontal stabilizer and elevator were crushed upward diagonally from a point midspan on the leading edge to a point about 2 feet from the tip of the trailing edge. The section of horizontal stabilizer in front of the right counterweight horn was bent up an additional 45 degrees. Three threads were showing on the trim actuator and the manufacturer's representative determined this indicated a 1-degree down position. The left horizontal stabilizer and elevator sustained some crush damage and the counterweight horn was crushed upward. The rudder trim tab assembly was bent with the trailing edge to the left, but the actuator linkage remained attached. Nine threads were showing on the trim actuator and the manufacturer's representative determined this represented a neutral position. At the juncture of the dorsal fin to the fuselage was a circumferential separation of the aircraft skin. Forward of this separation the cabin was twisted so that the aft belly section with the camera hole was perpendicular to the ground. The cabin area was split open and extensively fragmented. All levers on the throttle quadrant assembly were in the forward position except the right throttle lever. The left throttle was bent inboard so that the top of its lever was forward of the right propeller control; its black handle was missing. The right throttle was bent outboard and was behind the left throttle. The left control wheel outboard handle separated; both grips were separated from the right control wheel assembly. In the autopsy reports it was noted the pilot in the right seat had fractures of both elbows and left wrist. The left seat occupant had a fractured right forearm, deep lacerations of the right hand, and less traumatized left arm. The fuel selector sustained impact damage. The left selector lever was out of a detent near the center (off) position. Witness marks were observed in the detent for the inboard tank position. The right selector lever was in the inboard tank position. The crossfeed valve lever was destroyed. After examination it was determined by the manufacturer's representative that both inboard tanks were selected, the crossfeed valve was closed, and both fuel shutoff valves were in the fuel "on" position. Both fuel gascolator bowls were disassembled and examined. The left bowl and filter element were clean and uncontaminated. The right quick drain was broken off and missing. Some rust pitting was observed in the bowl. Dirt was observed in the bowl and filter, but no evidence of preimpact contamination was found. Both wings separated from the aircraft at the wing root. The left wing swung forward so that its tip was almost aligned with the fuselage. Its engine and propeller were bent and twisted back on top of it with the spinner toward the wing tip and the engine on its left side. The left wing leading edge exhibited crush damage and the recognition light unit was separated from the wing tip. The flap was attached and flush with the wing. The left aileron separated at both attach points and was held to the wing by its linkage. The aileron counterweight separated and was located in the debris. The manufacturer's representative determined the landing gear assembly was in the retracted position. The right wing was in its relative alignment to the fuselage, but fragmented into two pieces. The separation occurred from the leading edge, outboard of the nacelle, to the trailing edge outboard of the remainder of the flap. The outboard piece was displaced about 235 degrees, clockwise, from the wing root. The right engine and propeller separated from the wing. This wing exhibited leading edge crush damage and bucking outboard of the nacelle on both sections. The flap was in two pieces but remained partially attached to the wing. The manufacturer's representative determined the flap actuator assembly was in the retracted position. The aileron and trim tab remained attached to their wing sections. Two threads were showing on the trim actuator and the manufacturer's representative determined this was consistent with a neutral position. Four seats were in the aircraft at the time of the accident; no seats were installed in the center left or right rear positions. Seat belts for the forward two seats and the right center seat were fastened, but the webbing had been cut by rescue personnel. All three blades remained attached to the right propeller. One blade was slightly bent. A 2-inch section of the tip separated and the remaining portion was twisted. The second blade was bent and a 12-inch tip section separated. The separated piece was recovered; its leading edge was dented and gouged. The cambered side had scratches in a chordwise direction. The third blade was bent and twisted. Abou
The loss of power in the left engine for undetermined reasons and the pilot's subsequent failure to maintain minimum single-engine control airspeed. A contributing factor was the pilot's decision to fly with known deficiencies in the equipment.
Source: NTSB Aviation Accident Database
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