Gilroy, CA, USA
N144PG
Beech D95A
During a multi-engine instructional flight, the airplane entered a spin and descended into a wastewater treatment facility. Flight school personnel indicated that the intended flight plan was for the instructor to teach Vmc demonstrations to the private pilot undergoing instruction (PUI) and the passenger. During a Vmc demonstration, power is reduced on the critical engine (left) and the airplane is recovered prior to loss of directional control or stall. Radar data indicated that the flight departed and flew in a south-southeasterly direction. The airplane climbed to an altitude of approximately 4,400 feet mean sea level and showed a decrease in true airspeed, prior to disappearing from radar. Post accident examination revealed that the left engine was producing no to low power at the time of impact and the right engine was producing mid to high power, consistent with a Vmc demonstration. Examination of the engines and propellers revealed no evidence of a mechanical malfunction or failure, and control continuity was obtained. The PUI had accrued 2.7 hours in multi-engine airplanes at the time of the accident and the passenger had accrued 8.3 hours in multi-engine airplanes. Performance calculations using the airplane's presumed radar track showed that during the last portion of the flight, the calibrated airspeed decreased to 110 knots and the rate of descent was 400 feet per minute, and the track showed a turn to the left, prior to dropping off of radar. The calibrated airspeed of 110 knots is greater than the Vmc speed of 69.5 knots.
1.1 History of the Flight On December 18, 2006, at 1554 Pacific standard time, a Beech D95A (Travel Air), N144PG, descended uncontrolled into an open wastewater treatment tank at the South County Regional Wastewater Authority treatment facility in Gilroy, California. The airplane was destroyed. The certified flight instructor (CFI), the private pilot undergoing instruction (PUI), and private certificated passenger sustained fatal injuries. The airplane was owned and operated by California In Nice Inc., doing business as Nice Air, as a local instructional flight under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed Reid-Hillview Airport of Santa Clara County, San Jose, California at 1330. The local authorities received a call of a downed airplane at 1555. The wreckage was located by plant personnel at 1707 and reported to the local police. According to the operator, the purpose of the flight was for the CFI to teach the students multi-engine operations. At some point during the flight, the instructor would have landed at a local airport for the students to switch positions (one in front left seat and one in back seat). The airplane was scheduled to return to Reid-Hillview by 1700. 1.1.1 Witness Information A witness was flying in his airplane at an altitude of 3,500 feet on a heading of 320 degrees when he observed a multi-engine airplane in a spin and descending to the ground. He estimated the airplane was at an altitude of 2,500 to 3,000 feet and approximately 1 mile from his position when he first observed it. The airplane continued its vertical descent into an open sewage tank. He did not observe any other aircraft in the area at the time and he did not see any smoke emitting from the airplane. After the airplane disappeared into the open tank, he reported the incident to air traffic control. The controller requested that the pilot fly lower and report his observations to ATC. He descended to 1,000 feet and could not detect any wreckage or damage to the facility. He continued to circle the site for approximately 30 minutes, and then he notified air traffic control that he was going to depart the area. An additional witness, who was a CFI at Nice Air, reported that she and her flight student were in a Cessna 152. They were flying over Gilroy at an altitude of approximately 4,000 feet on a north heading when she saw the multi-engine airplane spinning. The witness believed that the airplane was spinning to the left but was not certain. After 5 seconds, the airplane descended into what appeared to be a factory. The witness further stated that on December 16, the accident CFI had flown with the same students on a similar mission. They departed Reid-Hillview about 1330 and the first student performed takeoffs and landings. Then, they flew to Hollister Municipal Airport, Hollister, California, where the students switched positions. The CFI and student then practiced maneuvers in the practice area, prior to returning to Reid-Hillview. The witness overheard the CFI speaking with his students the day prior to the accident and they indicated that the flight itinerary for December 18 would be the same as December 16. The witness also indicated that she spoke with the PUI and he stated that he would be practicing Vmc demonstrations as well as takeoffs and landings. 1.1.2 Radar Information A Safety Board air traffic control specialist reviewed the radar data pertinent for the flight. Radar data was obtained from the FAA's Northern California Terminal Radar Approach Control (NCT) located in Sacramento, California. The radar data used for this report came from an ASR-9 radar site located near Moffett Field, California. NCT supplied a video file containing a replay of the accident airplane's flight, beginning shortly after departure from San Jose. The airplane was initially radar identified, but subsequently terminated radar service, changing to transponder code 1200. Review of the data showed that the identified track was isolated from all but one unidentified aircraft near the point where radar contact was lost. The second aircraft passed within approximately 1/2-mile of the presumed accident airplane's track, in the opposite direction and at the same altitude. The track showed the presumed accident airplane's departure from San Jose, in a general south-southeast direction. The track proceeded into one turn to the right, and then continued in a south-southeast direction. At the last radar target, the airplane was established at 4,400 feet mean sea level. 1.2 Other Damage The South County Regional Wastewater Authority plant sustained damage to the hand railing that surrounded the tank impact area. In addition, several cosmetic scratch marks were noted on the inner concrete walls and tank partition. 1.3 Personnel Information 1.3.1 Certified Flight Instructor The CFI held a certified flight instructor certificate and was authorized to conduct single-engine, multi-engine, and instrument instruction. He held a first class medical that was issued in July of 2006. It contained no limitations or waivers. The operator reported that the CFI's total time was about 2,000 hours, with approximately 200 hours of multi-engine time. Of the 2,000 hours, about 1,800 hours were accrued while giving instruction, and 150 hours of the 200 hours of multi-engine time were accrued while giving multi-engine instruction. 1.3.2 Pilot Undergoing Instruction The PUI held a private pilot certificated and with an instrument rating. He held a second class medical that was issued in March of 2006. It contained the limitation that he must wear corrective lenses. The PUI obtained his private pilot certificate on June 14, 2006, and his instrument rating on December 7, 2006. The pilot was undergoing instruction to obtain a multi-engine rating and had accrued 2.7 hours of total multi-engine flight hours, all within the accident airplane make and model and with the accident CFI. 1.3.3 Passenger The passenger was also obtaining instruction for a multi-engine rating. He held a private pilot certificate. His first class medical certificate was issued in September of 2006 and contained no limitations or waivers. Records obtained from the operator showed that the passenger had accrued approximately 8.3 hours in multi-engine training in the accident airplane make and model, all with the accident CFI. 1.4 Airplane Information The airplane was a Beech D95A (Travelair). Two Textron Lycoming IO-360-B1B engines powered the airplane and were equipped with Hartzell HC-C2YK-2CUF propellers. The last annual inspection was completed on June 10, 2006, at an airframe total time of 5,834.9 hours and a tachometer time of 209 hours. On November 30, 2006, the airplane underwent a 100-hour inspection at a tachometer time of 309 hours. The date of the accident, the airplane was dispatched with a tachometer time of 324.3 hours and a Hobbs meter time of 484.9 hours. No airframe total time was noted on the dispatch log. According to the Beech Model D95A Owner's Manual, the best single-engine rate-of-climb speed with the landing gear and flaps retracted is 108 miles per hour (mph) (94 knots). The minimum control speed is 80 mph (69.5 knots). The power on stall speed with the landing gear and flaps retracted in level flight is 61 mph (53 knots). The power off stall speed in the same configuration is 85 mph (73.5 knots). Information obtained from the operator and the airplane manufacturer indicated that the airplane weight (estimated) at the time of the accident was 3,692 pounds, with a center of gravity (CG) of 81.5 inches. The CG range of the airplane at 3,600 pounds is between 75 and 86 inches aft of the datum. The maximum weight of the airplane is 4,200 pounds. 1.5 Meteorological Information An aviation automated routine weather report (METAR) was issued for Watsonville Municipal Airport, Watsonville, California, at 1554. The airport is located about 11 nautical miles west-southwest from the accident site. The following conditions were reported: sky condition, clear; visibility, 10 statute miles; altimeter, 30.23 inches of Mercury; temperature, 50 degrees Fahrenheit; dew point, 27 degrees Fahrenheit; wind from 240 degrees at 3 knots. 1.6 Wreckage and Impact Information The National Transportation Safety Board investigator and inspectors from the San Jose Flight Standards District Office responded to the accident site. The site was at 36 degrees 58.991 minutes North latitude by 121 degrees 31.870 minutes West longitude. The elevation was approximately 150 feet mean sea level. The plant consisted of varying levels of above-grade (raised) treatment tanks, which were surrounded by walkways lined with handrails. According to the plant project manager, the wreckage came to rest in a post anoxic tank located in the middle tank of a series of tanks. The footing foundation thickness was 20 inches and the perimeter wall thickness was 16 inches. The nitrification of toxic ammonia-nitrogen occurred in the oxidation ditch, which was directly north and south of the post-anoxic tank. Denitrification followed in the subject post-anoxic basin, where nitrates were biologically converted to nitrogen gas and released freely to the atmosphere. A reareation basin located directly next to the post anoxic tank, diffused oxygen into the wastewater, which was oxygen deficient following the nitrogen removal process. Wastewater was then directed to the secondary clarifiers, located approximately 100 feet from the post anoxic tank. The center treatment tanks and walkways (which included the reaeration basin) were a total of about 260 feet in length and 37 feet wide. The post anoxic tank was 160 feet in length and 40 feet wide, with an overall basin depth of 18 feet (water depth of 13.2 feet). However, within the tank, concrete partitions separated the main area into smaller sections, connected through a common channel that ran through the center floor. The damage to the plant was confined to the immediate impact area and surrounding handrails. The tank area that confined the main wreckage was about 18 feet long by 19 feet wide. The empennage section was broken from the main structure and lying next to the wreckage. The 5-foot section of handrail immediately aft of the main wreckage and to the right of where the empennage came to rest was torn away and located in the tank. A 10-inch wide by 14-foot high wing wall that ran perpendicular to the concrete partition, extended outward from the partition wall about 3 feet, in an area just aft of the fuselage. The top surface of this wall contained scratch marks and the concrete outboard edge was damaged. On the left horizontal stabilizer, a 10-inch wide rectangular-shaped impact was noted on the leading edge and the skin was pulled aft to the rivet line. A left wingtip and outboard 4 feet was lodged in a damaged handrail; the remainder of the left wing, stayed connected to the fuselage. The left engine had separated from the firewall and was twisted inboard. The right wing and right engine were found in an adjoining tank, separated by a concrete partition from the tank with the main wreckage. The wing separated at the fuselage structure. The propellers remained attached to their respective engines. 1.7 Medical and Pathological Information The Santa Clara County Medical Examiner-Coroner completed autopsies on the occupants of the airplane. The FAA Civil Bioaeronautical Research Laboratory completed toxicological testing on specimens of the CFI and PUI. The tests were negative for carbon monoxide, cyanide, and tested drugs. The CFI's test was negative for volatiles. The PUI's volatiles test was positive for 12 (mg/dL, mg/hg) ethanol, which was detected in muscle, but not in his liver. Putrefaction was noted on the toxicology report. 1.8 Tests and Research On December 21 and 22, 2006, the National Transportation Safety Board investigator, two inspectors from the San Jose Flight Standards District Office (FSDO) and technical investigators from Raytheon Aircraft Company, Hartzell Propeller Incorporated, and Textron Lycoming examined the wreckage at Plain Parts, Pleasant Grove, California. 1.8.1 Airframe Impact forces destroyed the airframe. The main fuselage structure was vertically collapsed downward and to the left. During the collision sequence, the right wing separated from the fuselage structure at the root. The empennage section also separated and was found within several feet of the main wreckage. All control surfaces and balance weights were accounted for. The left wing remained attached to the main fuselage structure and was separated 20 inches outboard of the wing root. The flap and aileron separated. The left main gear remained attached to the wing and was stowed. The auxiliary fuel cap remained attached to the fuel tank and the o-ring was pliable. The left engine was displaced 90 degrees inboard to the fuselage. Impact forces destroyed the engine cowling. The left flap actuator measured 1.5 inches, which according to the airframe representative, was consistent with the flaps in the retracted position. The right wing was separated from the fuselage. The flap had separated and the aileron remained attached by its outboard hinge. The aileron separated from the bellcrank pushrod, but the aileron flight control cable remained attached to the bellcrank. The wing tip was attached. The flap actuator measured 1.5 inches. The fuel selector handles were in the aux position at the cockpit fuel selector, as well as the fuel selector valves. All fuel tanks were breached. The empennage control surfaces remained attached, excluding the left outboard elevator and right elevator counterweight. The missing portions of elevator were later identified within the recovered wreckage from the tank. The left stabilizer sustained leading edge impact damage 28 inches from the stabilizer root. A 10-inch wide section was torn up and aft to the main spar. The stabilizer was bent forward 28 inches from the stabilizer root. Approximately 43 inches of the left elevator remained attached. The outer portion was separated at the middle elevator hinge. The elevator control horn was displaced 3 inches aft into the tail cone. The elevator trim tab remained attached to the elevator. The actuator measured 1 3/8 inches or 5 degrees tab down. The elevator push rod separated from the actuator. The right elevator remained attached by the middle and outboard hinge and the trim tab pushrod. The elevator counterweight separated. The trim actuator measured 1 7/8 inches or 25 degrees tab down. The rudder was attached to the vertical stabilizer at the hinge points and moved freely at both hinge points. The rudder moved freely to both stops. The rudder flight control cables were manipulated 3 feet forward of the separated empennage. The rudder control surface responded appropriately. The rudder trim actuator measured 1.6 inches or 4 degrees tab left. According to the airframe manufacturer, all of the trim cable separations exhibited stress overload. The left and right fuel selector valves were unobstructed and attached to the wing. The strainer screens were unobstructed. The fuselage was turned onto its back and further visual documentation of the control cables was obtained, as well as access to the rudder control system. The rudder pedals were both separated on the left side. The right rudder pedal on the right side was missing; the left pedal was fractured. The rudder pedal bellcrank was intact, as well as the pushrods and cables that connected to it. The front seats were removed and the seat tracks were documented. According to the airplane manufacturer, there was no evidence of hole elongation or seat slippage. 1.8.2 Left Engine The left engine, serial number L8846-51A, was examined. The accessories were removed which included the fuel pump, magnetos, propeller governor, fuel injection servo, vacuum pump, and thermostatic bypass valve. The left engine crankshaft was rotated via the propeller. Thumb compression was obtained
The certified flight instructor's failure to maintain directional control of the airplane and inadequate supervision of the flight, which resulted in a stall/spin.
Source: NTSB Aviation Accident Database
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