LAX02FA031

The airplane collided with mountainous terrain during cruise after encountering turbulence and downdrafts associated with mountain wave conditions. According to Federal Aviation Administration (FAA) records, the pilot called the Reno Automated Flight Service Station at 0941 and filed an IFR flight plan, then asked for the winds aloft forecast, which was provided. The pilot did not request any additional weather briefing information for the flight. No other record was found that the pilot obtained additional weather forecast information from any official source associated with the FAA or the National Weather Service. At the time of the pilot's call to the Reno AFSS, several AIRMET weather advisories had been issued hours prior detailing warnings for turbulence and clear icing along the route of flight. The advisories warned of occasional moderate turbulence below 18,000 feet in moderately strong westerly winds especially in the vicinity of mountainous terrain. Clear Air Turbulence (CAT) between 18,000 and 40,000 feet was forecast over the area of the accident site due to jet stream wind shear and mountain wave activity. The pilot departed under visual flight rules (VFR) and picked up his instrument flight rules (IFR) clearance en route and climbed to 14,000 feet. The pilot later asked if he could maintain 12,500 feet. The controller advised him that the minimum IFR altitude on this segment of his route was 14,000 feet, and the pilot cancelled his IFR flight plan. The controller advised the pilot that he had lost radar contact, and instructed the pilot to squawk VFR and the pilot acknowledged the transmission. The last radar target was about 1/2 mile east of Eagle Peak (elevation 9,920 feet) in the Warner Mountains. Rescuers discovered the wreckage near the crest of Eagle Peak on November 23. Investigators found no anomalies with the airframe, engines, or propellers that would have precluded normal operation. The NWS had a full series of AIRMETs current over the proposed route of flight, which included mountain obscuration, turbulence, and icing. Analysis of the weather conditions disclosed a layer between 9,500 and 11,000 feet over the accident site area as having a high likelihood of severe or greater turbulence. A pilot on the same route of flight reported at 1127 that he was in instrument conditions at 11,000 feet, and experiencing light turbulence and light clear icing conditions. He also reported encountering updrafts of 2,000 feet per minute, which was indicative of mountain wave activity. A company pilot was in a second Aero Commander trailing the accident airplane and he reported that at 1147, at a position near the accident site, he encountered a severe downdraft. He applied full climb power, but as the airplane passed over the accident site position, the airplane continued to lose altitude even at maximum power. At 1159, he was able to gain altitude, and return to his assigned cruising altitude of 14,000 feet. The second Aero Commander was turbocharged, the accident airplane was not. Analysis showed that the topography of the area was critical in this case, given that the accident site was at an elevation of 9,240 feet on the eastern slope of Eagle Peak. The accident airplane's flight track was normal along the airway until immediately downwind of the higher terrain. As the flight approached the lee side of the mountain, it came under the influence of the mountain wave and first encountered an updraft and then a downdraft, which increased in amplitude as the flight progressed towards Eagle Peak. Eagle Peak was the tallest point along the Warner Mountain range and the steep slope of this terrain was significant when the mountain wave action was encountered. Such terrain features have been known to enhance the vertical downdrafts and updrafts associated with the most intense mountain wave turbulence.

History of flight

On November 21, 2001, at 1126 Pacific standard time (PST), an Aero Commander 500S, N900RA, collided with terrain near Eagleville, California. Commander Northwest Limited was operating the airplane under the provisions of 14 CFR Part 91. The airline transport pilot licensed pilot, a commercial rated pilot passenger, and three passengers sustained fatal injuries; the airplane was destroyed. The personal cross-country flight departed Reno, Nevada, at 1037, en route to Wenatchee, Washington. Visual meteorological conditions prevailed at the nearest reporting station, which was 24 miles away. An instrument flight rules (IFR) flight plan had been filed. The approximate global positioning system (GPS) coordinates of the primary wreckage were 41 degrees 17.69 minutes north latitude and 120 degrees 11.936 minutes west longitude.

According to Federal Aviation Administration (FAA) records, the pilot called the Reno Automated Flight Service Station at 0941. The records show that the pilot filed an IFR flight plan, then asked for the winds aloft forecast. The specialist provided the winds aloft information. The pilot did not request any additional weather briefing information for the flight. No other record was found that the pilot obtained additional weather forecast information from any official source associated with the FAA or the National Weather Service. At the time of the pilot's call to the Reno AFSS, several AIRMET weather advisories had been issued hours prior detailing warnings for turbulence along the route of flight. The advisories warned of occasional moderate turbulence below 18,000 feet in moderately strong westerly winds especially in the vicinity of mountainous terrain. Clear Air Turbulence (CAT) between 18,000 and 40,000 feet was forecast over the area of the accident site due to jet stream wind shear and mountain wave activity. Complete details of the weather forecasts and conditions can be found in the Meteorological Information Section of this report.

A transcript of recorded radio transmission indicated that the pilot informed clearance delivery that he would depart under visual flight rules (VFR) and pickup his IFR clearance en route. At 1044, the pilot requested his IFR clearance from Reno Departure Control. Departure control cleared him to his destination via radar vectors Lakeview (LKV) VORTAC (very high frequency omni-directional radio range, tactical air navigation) as filed. They then cleared him via the V165 airway as filed, and the pilot acknowledged the clearance.

At 1051, the pilot checked in with Oakland Air Route Traffic Control Center (ARTCC) climbing through 12,000 feet to 14,000 feet. The controller instructed the pilot to fly a heading of 350 degrees to intercept V165.

At 1054, the pilot asked if he could maintain 12,500 feet. The controller advised him that the minimum IFR altitude on V165 was 14,000 feet, and the pilot cancelled his IFR flight. The controller said that he could provide flight following, but would lose radar contact in 20 miles. At 1059, the controller advised the pilot that he had lost radar contact, and instructed the pilot to squawk VFR and approved a frequency change; the pilot acknowledged the transmission.

Recorded radar data depicted a target operating along V165 at a mode C reported altitude of 10,500 feet. Between 1112 and 1126, the data indicated a series of up and down oscillations of 100 to 200 feet, which increased in frequency as the target approached the Warner Mountain Range. At 1124:58, the target made a slight change in course to the northwest and began descending.

The last target occurred at 1126:22, at 41 degrees 17 minutes 09 seconds north latitude and 120 degrees 11 minutes 41 seconds west longitude. This was about 1/2 mile east of Eagle Peak (elevation 9,920 feet). Rescuers discovered the wreckage near the crest of Eagle Peak on November 23. A team recovered the wreckage on July 23, 2002.

Personnel information

A review of FAA airman records revealed that the pilot held an airline transport pilot certificate with an airplane multiengine land rating. He held a commercial pilot certificate with ratings for single engine land, single engine sea, and glider aero tow. He held a certified flight instructor certificate with ratings for airplane single engine and multiengine land, instrument airplane, and glider. The operator estimated that the pilot's total flight time was 20,000 hours.

The pilot held a ground instructor certificate with ratings for advanced and instrument. He held an airframe and powerplant mechanic certificate.

The pilot held a second-class medical certificate issued on February 23, 2001. It had the limitations that the pilot must wear corrective lenses and possess glasses for near and interim vision.

Aircraft information

The airplane was an Aero Commander 500S, serial number 3070. The operator reported a total airframe time of 8,101 hours. The last annual inspection occurred on September 30, 2001.

The airplane had a Textron Lycoming IO-540-E1B5 engine, serial number L-8632-48, installed on the left side. Time since overhaul on the engine at the annual inspection was 1,197 hours.

The airplane had a Textron Lycoming IO-540-E1B5 engine, serial number L-6421-48, installed on the right side. Time since overhaul on the engine at the annual inspection was 1,197 hours.

Meteorological information

A National Transporation Safety Board staff meteorologist prepared a factual report, and a summary of the report follows. All directions are referenced to true north and distances are in nautical miles. Heights are above mean sea level (msl) unless otherwise noted. Visibility is in statute miles and fractions of statute miles. The IIC converted all time to PST.

The report included a topographical map, which showed the accident site on the eastern slope of the Warner Mountain Range.

Surface Observations

Alturas (KAAT), California, which was the nearest reporting station, was 24 miles west-northwest of the accident site at an elevation of 4,374 feet. It had an Automated Surface Observation System (ASOS). An aviation routine weather report (METAR) for Alturus was issued at 1055. It stated: auto; skies 3,400 feet overcast; visibility 10 miles; winds from 190 degrees at 12 knots; temperature 8 degrees Celsius (C); dew point 4 degrees C; altimeter 29.90 inches of mercury. The remarks section noted that the thunderstorm sensor was inoperative.

A METAR for Alturus at 1155 stated: auto; skies 3,400 feet overcast; visibility 10 miles in light rain; winds from 220 degrees at 6 knots; temperature 7 degrees Celsius (C); dew point 5 degrees C; altimeter 29.88 inches of mercury. The remarks section noted less than 0.01 inch of precipitation since the last observation, and that the thunderstorm sensor was inoperative.

Surface Analysis Chart

The National Weather Service (NWS) Surface Analysis Chart issued for 1000 on November 21, 2001, depicted a low pressure system over Idaho with a dissipating cold front to the south of the accident site. This system turned into a warm front and connected with an occluded frontal system with a low pressure system with a central pressure of 988 millibars (mb) off the Pacific coast. Across central and northern California, two high pressure systems with central pressures of 1019 mb and 1020 mb were on either side of the dissipating cold front, with one high pressure system located immediately to the south-southwest of the accident site. The isobars depicted an increasing gradient off the Pacific Northwest coast, but no significant pressure gradient over northern California at the surface.

Weather Depiction Chart

The NWS Weather Depiction Chart issued for 1100 depicted the dissipating cold front to the south of the accident site. It depicted a large area, which included the accident site, of marginal visual flight rule (MVFR) condit