San Diego, CA, USA
N7093F
CESSNA 150F
The pilot was performing banner tow operations over water, about 500 feet above ground level, in the modified two-seat airplane. The pilot-rated passenger was handling the airplane controls, and 1 hour after takeoff, having performed a series of uneventful laps, the pilot and passenger decided to return for landing. The passenger applied full forward throttle control to initiate a climb, but the engine lost all power. The airplane immediately began to descend, and the pilot took over the flight controls, released the banner, and performed a forced landing into the water. The airplane sustained substantial damage to the fuselage as it struck the water, separating the right main landing gear from the airframe. The separation of the right main landing gear meant that the airplane most likely came to rest right-wing-low on the sea bed. Due to the design of the fuel tanks’ interconnecting vent lines and the inclusion of a vent port on the left tank only, fuel most likely either un-ported from the left tank while in the water, or transferred between tanks after recovery. As a result, an accurate determination of the fuel tank quantities could not be determined. The pilot and passenger reported that the fuel selector valve was in the “BOTH” position throughout the flight, however it was found in the “RIGHT” tank position after the accident. The location of the valve was such that it was most likely inadvertently kicked to this position as the passenger egressed from the airplane as it was sinking. Postaccident examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation. The pilot did not use carburetor heat before the accident. While the temperature and dew point were conducive to carburetor icing at the engine’s operating power level, the investigation could not conclusively determine that carburetor ice caused the loss of engine power.
HISTORY OF FLIGHT On May 26, 2012, about 1530 Pacific daylight time, a Cessna 150F, N7093F, landed in the waters of San Diego Bay, San Diego, California, after experiencing a loss of engine power. Aerial Advertising LLC was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91, as a banner tow flight. The commercial pilot and private pilot rated passenger were not injured. The airplane sustained substantial damage during the accident sequence. The local flight departed Gillespie Field Airport, San Diego/El Cajon about 1430. Visual meteorological conditions prevailed, and no flight plan had been filed. With the pilot rated passenger positioned in the right seat, and taking photographs, the commercial pilot performed a series of laps in the airplane at an altitude of 500 feet agl, over the central bay area adjacent to the Coronado Bridge. The pilot then allowed the passenger to manipulate the flight controls, and they repositioned the airplane to the northeast for four more laps over the bay. Once complete, the commercial pilot verified that all engine instruments were indicating normal operation, and made contact with air traffic control personnel, requesting a clearance through the San Diego International Airport class B airspace. The passenger began to initiate a climbing right turn towards the northwest, while simultaneously applying full forward throttle. The passenger reported that the instrument panel then began to vibrate, the engine did not respond, and subsequently lost all power. The airplane immediately began to descend, and the commercial pilot took over the flight controls. He released the banner, and prepared for a forced landing into the water. Both occupants reported that they did not have time to troubleshoot, due to the low altitude. The airplane struck the water, separating the right main landing gear, and causing substantial damage to the forward fuselage and firewall. The airplane then began to sink as they egressed. AIRCRAFT INFORMATION The high wing, single engine, two seat airplane was manufactured in 1966, and had undergone a series of modifications equipping it for banner tow operations. FAA airworthiness major repair and alteration records revealed that in December 1990, the airplane was modified with the installation of a Lycoming O-360-A4A engine, installed under supplemental type certificate (STC) SA4795SW. Additional equipment included a short take off and land kit (STC SA944CE), long-range fuel tanks (STC SA5733SW), and a modification to the fuel supply system, which included the replacement of the fuel selector valve with a Cessna 172 valve, located on the seat support bulkhead under the passenger seat lip. A “Gassor Tow Hitch” assembly was installed in May 1990. The fuel tank modification included the replacement of the standard fuel tanks with two long-range tanks, the total capacity of which was 42 gallons. Fuel venting was accomplished through a ventilation hose interconnecting both tanks at their inboard walls, and a ventilation tube on the left tank outboard wall. Maintenance records indicated that the airplane had undergone an annual inspection on June 23, 2011, at a total airframe time of 6,844.38 hours. At that time, the engine (serial number RL-15969-36A) had accrued a total of 892.7 flight hours since overhaul in July 2001. Based on the tachometer time recorded on the morning of the accident flight, the engine and airframe had accumulated about 28 flight hours since annual. METEOROLOGICAL INFORMATION An automated surface weather observation at San Diego International Airport, (located about 1.5 miles northwest of the accident site) was issued at 1551. It indicated wind from 280 degrees at 10 knots, 10 miles visibility, with few clouds at 3,200 feet, temperature of 18 degrees C, dew point 07 degrees C, and an altimeter setting at 30.06 inches of mercury. TESTS AND RESEARCH The airplane was recovered from the sea bed on the day following the accident, and placed on the dock subsequent to transportation. Recovery personnel reported that the right tank contained fuel and water, with about 10 gallons of fuel recovered. The left tank did not contain any fuel. Examination of the fuel selector valve revealed that it was set to the right tank position. The throttle, fuel mixture, and carburetor heat controls were all in the forward position, and the flaps appeared set to about 5-degrees of extension. The pilot recounted that the standard operating procedure was to always leave the fuel selector valve in the both position during the run-up, and at all times during banner tow flights. He confirmed that the selector valve was in the both position during preflight checks, and both he and the passenger stated that it had not been changed at any time during the flight. The pilot further reported that carburetor heat was not used when the engine lost power, because it had been operating at between 2,100 and 2,300 rpm, and producing power during that period. He stated that both fuel tanks were full at the time of departure. Engine Examination The engine and airframe were examined subsequent to recovery. The engine sustained minimal damage during the accident sequence. All engine controls were continuous from their respective control arms through to the cabin controls. A blue-colored liquid consistent in color and odor to aviation gasoline was present in the gascolator and associated supply lines through to the auxiliary and engine driven fuel pumps. Residual quantities of blue fluid mixed with water were present in the hose between the engine driven fuel pump and carburetor. The inlet air filter and associated induction air lines were free of obstruction. The top spark plugs were removed, and examined. Their electrodes remained mechanically undamaged, coated in light and dark grey deposits, and displayed wear varying wear signatures between normal, and worn-out normal when compared with the Champion Spark Plugs AV-27 Check-A-Plug chart. The crankshaft turned freely when rotated by hand utilizing the propeller, and cylinder compression was noted on all cylinders. Mechanical continuity was established throughout the rotating group, valve train, and accessory section. And an audible click was heard from the magnetos consistent with impulse coupling operation. Salt water submersion and subsequent corrosion prevented an accurate determination of the magnetos’ operation. Visual inspection of the combustion chambers was accomplished through the spark plug bores utilizing a borescope; there was no evidence of foreign object damage and all combustion and exhaust surfaces exhibited light grey deposits consistent with normal operation. Examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation. The carburetor icing probability chart from Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB): CE-09-35 Carburetor Icing Prevention, June 30, 2009, shows a probability of serious icing at glide power at the temperature and dew point reported at the time of the accident. Carburetor and Fuel Pump Examination The carburetor and engine driven fuel pump were removed, and examined in the presence of the NTSB investigator-in-charge, at the facilities of Corona Aircraft Engines Inc. No anomalies were noted. A full examination report is contained within the docket for this accident.
A total loss of engine power while maneuvering for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have precluded normal operation.
Source: NTSB Aviation Accident Database
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