Inyokern, CA, USA
N46KA
Jones RV-6A
The amateur-built, airplane impacted mountainous terrain in dark night conditions after experiencing a loss of engine power while in cruise flight at 13,000 feet. The airline transport pilot obtained a weather briefing prior to departing on a visual flight rules (VFR) flight. During the briefing, the pilot was advised that VFR flight was not recommended and that flight precautions existed for icing conditions above 7,000 feet, the potential for mountain obscurement, cloud layers predominant through the route of flight and the chance of widespread rain. The pilot reported experiencing weather during his flight and the air traffic controller asked him if they wanted to continue in instrument flight conditions (IMC). The pilot stated he would like to continue in IMC and indicated if he encountered icing conditions he would "ask for a 180" and divert to another airport. Later during the flight, the pilot told the air traffic controller he was encountering snow. He called the controller again and reported he was experiencing a rough running engine and that he wanted to divert to a nearby airport and declare an emergency. The controller then issued radar vectors to the airport. The pilot continued to ask for and received terrain information as he descended past 5,000 feet. Radar data and communications were then lost. The airplane was found on the side of a mountain ridge at 4,700 feet.
HISTORY OF FLIGHT On March 6, 2001, at 2200 Pacific standard time, an experimental amateur-built RV-6A single engine airplane, N46KA, was substantially damaged when it impacted rising terrain west of Inyokern, California. The airline transport pilot and pilot-rated passenger both received fatal injuries. The pilot, who was also the builder/owner of the airplane, was operating the airplane as a personal flight under the provisions of 14 CFR Part 91 when the accident occurred. The flight had originated from the Zamperini Field in Torrance, California, about 2100, and was reportedly en route to Bishop, California. Instrument meteorological conditions prevailed in the area and an instrument flight rules (IFR) flight plan had been filed and activated en route. According to the Federal Aviation Administration (FAA), air traffic controllers at High Desert Terminal Radar Approach Control (TRACON) were contacted by the pilot at 2115:39. The pilot indicated he was flying at 9,500 feet and was en route to Bishop. At 2118:13, the pilot reported he was going to climb to 10,500 feet. At 2139:04, the air traffic controller asked the pilot what the flight conditions were, to which the pilot replied, "we're VFR [visual flight rules]." At 2139:49, the pilot told the controller they were getting into rain and they were going to try to get under it. The pilot asked the controller if they were depicting the weather on the radar. The controller informed the pilot that a band of precipitation was depicted 5 miles north of the aircraft's position and it stretched to the east approximately 50 miles, to the west approximately 20 miles, and to the north it stretched to 20 miles north of Inyokern. At 2141:16, the pilot told the air traffic controller he had reversed the aircraft's direction and was going to see if he could get below a cloud layer then proceed on course. The controller asked the pilot if he was IFR qualified and equipped, to which the pilot reported he was. The controller offered to give the pilot a vector to Bishop in IFR conditions, and then could attempt to put the aircraft in VFR conditions once the airplane was farther north. The pilot asked how far the precipitation band extended to the north, to which the controller reported 43 miles from the aircraft's current location. The pilot then elected to establish the flight on an IFR flight plan to Bishop, and requested the current weather for their destination. The air traffic controller then issued a clearance to Bishop via vectors, initiating with a vector heading of 340 degrees, and an altitude of 13,000 feet. The controller then told the pilot that the weather data he had on Bishop was 50 minutes old. The Bishop weather was reported as wind from 290 degrees at 6 knots; visibility 10 statute miles; scattered clouds at 8,000 feet; temperature and dew point 3 degrees Celsius; and an altimeter setting of 30.12 inches of mercury. At 2146:30, the air traffic controller told the pilot he could assign him a higher altitude if he wanted it. The pilot indicated he would remain at 13,000 feet, but wanted to know if there were any reports of icing. The controller said that there were no pilot reports and that his weather data reported that "the tops [were] around 15,000 feet." The pilot stated that they would stay at 13,000 feet and "should we encounter icing, we'll just ask for a one eighty back to Mojave and go there." At 2153:56, the controller told the pilot they had passed through the worst of the depicted precipitation and the pilot had another 20 miles to get past the remaining precipitation. The pilot responded at 2154:09, by stating, "at our altitude, it looks like snow out there." At 2155:28, the pilot told the controller he was experiencing a rough running engine and they wanted to divert to Inyokern. He requested the weather information for Inyokern. The air traffic controller stated that he did not have weather information for Inyokern; however, he had the weather data for China Lake (China Lake Naval Air Weapons Station (NAWS) Armitage Field, which is located approximately 7 miles east of Inyokern). The pilot requested a vector to China Lake. The controller told him to fly a heading of 090 degrees and gave the pilot the China Lake weather, which was wind from 180 degrees at 5 knots; visibility 6 statute miles with rain and mist; few clouds at 2,500 feet; broken ceiling at 2,900 feet; and an overcast ceiling at 4,300 feet. The controller added, "[it] doesn't look very good, I suggest Mohave." At 2156:21, the pilot then indicated they would not make it to Mohave, told the controller they had to divert to China Lake, and declared an emergency. The controller issued a vector heading of 075 degrees to the China Lake Airport, and told the pilot that the airplane was 16 miles west of the airport. At 2157:52, the air traffic controller informed the pilot the minimum vectoring altitude (MVA) for the aircraft's location was 10,500 feet, and the MVA would be lower in approximately 7 miles. At 2158:24, the pilot indicated he needed a "vector away from terrain." The controller told the pilot to maintain his present heading and that would take them to the lowest terrain in the area. The pilot asked for the current weather information at China Lake, to which the air traffic controller replied, "weather is 6 miles and rain and . . . low ceilings, 2,900 broken, 4,300 overcast." At 2159:02, the pilot asked the controller, "what's the terrain in this area where I am now?" The controller told the pilot they were clearing the higher terrain, and should be approaching a highway. The controller added they were approximately 3 miles west of the Inyokern Airport. At 2159:39, the pilot asked what the terrain was like at their current position and informed the controller they were descending through 5,000 feet. The controller informed the pilot his present heading would take him to the best terrain conditions. At 2200:07, the controller lost radar contact with the accident airplane. The last radar return indicated that the airplane was located about 3 miles west of Inyokern with a mode C altitude report of 4,700 feet msl. The airplane's last known position was 35 degrees 38.16 minutes north latitude and 117 degrees 54.31 minutes west longitude. PERSONNEL INFORMATION The pilot was employed as a commercial airline pilot. He held an airline transport pilot certificate for single and multiengine land airplanes, and was issued a first-class medical certificate on October 4, 2000, with a limitation to have glasses available for near vision. According to his employer, he completed his last airmen flight check on September 19, 2000. They also reported he had accumulated approximately 6,644 total flight hours. Using aircraft records, NTSB investigators estimated that the pilot had accumulated at least 216 hours in the accident airplane. AIRCRAFT INFORMATION The pilot was the owner and builder of the experimental amateur-built airplane. Review of the aircraft records revealed the pilot began building the airplane on November 1, 1997, and completed its construction on November 26, 1998. On December 26, 1998, the aircraft was issued a Special Airworthiness Certificate. The airplane underwent a pitot/static and transponder systems check on February 28, 1999. On February 6, 2001, the airplane underwent its last condition inspection and was found to be "in a condition for safe operation." The pilot/owner was the person who endorsed the last condition inspection. The aircraft was equipped with an Apollo GX65 Global Positioning System (GPS). The aircraft was equipped with a Lycoming O-360-A1A carbureted engine. Van's Aircraft, Inc., the aircraft kit manufacturer, provides a Filtered Air Box Kit (FAB-360). According to Van's Aircraft, the induction air box was designed to provide a uniform, low restriction air induction. It incorporates a small, low external drag, high inlet velocity opening with an efficient pressure recovery plenum area around a circular air filter. The air plenum and circular air filter provide a uniform airflow into the carburetor venturi, and thus a uniform, balanced flow distribution through the induction manifold to the respective cylinders of the engine. The air box design includes a pilot-actuated alternate air door for simultaneously blocking off outside inlet air and opening an alternate heated air source. The alternate air source can be either heated air directly from the warm air plenum of the lower engine compartment, or from an exhaust manifold heat muff, at the discretion of the aircraft manufacturer (builder). This design permits the pilot to supply either outside ram/pressure recovery air to the carburetor, or to completely block the outside ram air and instead supply heated air from inside the engine cowling, or from an exhaust stack heat muff, to the carburetor. The heated air is ducted to the front side (upstream) of the air filter. Review of photographs taken at the accident site revealed that the accident aircraft had a carburetor air box similar to the kit sold by Van's Aircraft installed. However, it is not known as to what method of heated alternate air source and routing was utilized by the builder. METEOROLOGICAL INFORMATION The pilot obtained a standard weather briefing at 1929, from the Hawthorne Flight Service Station (FSS). According to the printed transcripts of that briefing, the pilot requested a standard weather briefing from Torrance to Bishop. The weather briefer asked if the pilot was planning to fly IFR, to which the pilot replied in the affirmative. The pilot indicated he was planning on flying at 7,500 feet, and the flight would take approximately 1 hour 30 minutes. He reported he would depart around 2030. The weather briefer informed the pilot there were flight precautions in effect for the entire route of flight, which carried the potential for occasional moderate rime or mixed icing in the clouds and precipitation. The freezing level was reported as 7,000 feet up to 20,000 feet for the entire route. The briefer also reported that moderate turbulence was possible below 15,000 feet, especially in the vicinity of rough terrain. He added that there was the potential for mountain obscurement by clouds, occasional precipitation, and isolated thunderstorms. VFR flight was not recommended. The pilot was informed of a low pressure system off the coast of California that was resulting in "bands of moisture and instability" and "some significant convection over . . . California low and high deserts . . ." The current weather for Torrance was given as wind from 140 degrees at 8 knots; visibility 25 statute miles; scattered clouds at 1,500 feet agl; broken clouds at 20,000 feet; temperature 13 degrees Celsius; dew point 10 degrees; and an altimeter setting of 29.90 inches of mercury. The weather briefer then informed the pilot the basin area was drying out and there were scattered clouds around 2,000 - 4,000 feet. He added as the flight approached the mountains, the pilot could expect higher broken layers that were occasionally overcast with bases between 5,000 and 7,000 feet, and higher layers at 10,000 feet. The briefer reported the "layers are occasionally merging and extending up above 20,000 feet." The weather briefer reported the visibilities along the route were 7 statute miles or better with isolated thunderstorm activity up over the Palmdale, Edwards area, and northward into the Owens Valley area. The briefer stated the weather radar over the intended route of flight depicted wide spread and widely scattered light rain and scattered imbedded moderate cell tops to flight level 300. He added the "active weather is drifting towards the Palmdale, Lancaster area then back out towards the coast, so it's going to continue to impact that area probably at least overnight." The weather briefer then issued the current weather at Bishop, which was reported as wind from 300 degrees at 6 knots; visibility 10 statute miles; few clouds at 3,400 feet; scattered clouds at 7,000 feet, and an overcast cloud layer at 10,000 feet; temperature 4 degrees Celsius; dew point 3 degrees Celsius; and an altimeter setting 30.10 inches of mercury. He added that a thunderstorm was reported at 17 miles north of Edwards, and it was moving north-northwest. The pilot was informed that the forecast for the route held little significant change until daybreak the following morning. The route forecast predicated scattered clouds between 3,000 and 4,000 feet, broken clouds between 6,000 and 7,000 feet, and scattered and broken layers to 20,000 feet. The weather briefer told the pilot the forecast visibilities held the potential for 5 statute miles in light rain, showers, and mist. Isolated thunderstorms and light rain showers were forecast through the mountains with the mountains becoming occasionally obscured. The briefer also reported the forecast, until 2200, included visibilities more than 6 statute miles with light rain and broken ceilings at 5,000 feet and areas of broken ceilings at 2,000 feet. The weather briefer also informed the pilot that local visibilities (for the Palmdale, Inyokern, and Bishop area) were forecast as 1/2 statute mile in snow with overcast ceilings at 500 feet, isolated surface wind gusts to 30 knots, with occasional visibilities of 3 statute miles in thunderstorms, moderate rain, small hail, and mountain obscurement. The pilot was informed conditions were forecast to improve somewhat to locally IFR and marginal VFR conditions after 2200; however, the weather was still forecast until 0200, to be scattered to broken clouds at 9,000 feet with occasional scattered light rain showers, ceilings broken at 4,000 feet and possibly 1,000 feet, with visibilities of 1 statute mile in light snow showers. The terminal forecast for Bishop until 2300, was reported as wind from 010 degrees at 9 knots; visibility more than 6 statute miles in light rain; scattered clouds at 1,500 feet; overcast clouds at 4,000 feet; and occasional visibilities of 5 statute miles in light rain and mist with an overcast ceiling of 1,500 feet. The pilot was issued the winds aloft information and was informed again that the freezing level was at the 7,000- to 7,500-foot level. The weather briefer provided the notices to airmen and requested a pilot report if the pilot had time. The pilot asked the weather briefer if his radar data was depicting any precipitation, to which the briefer replied, "no, right now north." The pilot asked if there was any in the valley, to which the briefer replied, "looks like some creeping in from the southeast maybe 20 to 30 miles north of Edwards." The controller added that the precipitation was heavier west of Edwards, where it met the southern Sierras. The pilot indicated that they would "talk it over and see what we're going to do," and ended the briefing. The Safety Board conducted a meteorology study. The following are details extracted from that study: The closest weather observation facility was located at the Kern County Airport (IYK), Inyokern, which was 5.5 miles east of the accident site at an elevation of 2,455 feet msl. At 2047, which was the last observation of the day, the weather was reported as winds from 360 degrees at 15 knots; visibility 20 statute miles in light rain; few clouds at 4,000 feet; overcast ceiling at 8,000 feet; temperature of 10 degrees Celsius; and an altimeter setting of 30.02 inches of mercury. At 2138, the weather observation facility at China Lake NAF reported the following special weather report: wind from 180 degrees at 5 knots; visibility 6 statute miles in moderate rain and mist; few clouds at 2,500 feet; ceiling broken at 2,900 feet; overcast clouds at 4,300 feet; temperature and dew point missing; and altimeter setting of 30.06 inches of mercury. Review of the closest upper air soundings (108 miles northeast of the accident site) depicted a freezing level of 7,841 feet. The local weather radar data could not be retrieved, therefore, the National Radar Mosaic was utilized to determine if there were any significant radar echoes over the region surrounding the time of the
the in-flight collision with mountainous terrain during a forced landing following a loss of engine power resulting from the pilot's inadequate weather evaluation, continued flight into icing weather conditions, his delay in carburetor heat use, and his delay in diverting to an alternate airport.
Source: NTSB Aviation Accident Database
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