WPR15FA072

The pilot’s continued visual flight into instrument meteorological conditions which resulted in an inflight collision with terrain. Contributing to the accident was the pilot’s inadequate preflight planning, during which he failed to identify forecasted deteriorating weather conditions along the route of flight.

The helicopter was on a visual flight rules (VFR) repositioning flight in preparation for providing contracted air support capability to the local sheriff's office the next day. The operator reported that the helicopter did not arrive at the intended destination, and the wreckage was located 29 miles north of the intended destination. The helicopter was fragmented into multiple pieces along a 174-ft debris path. Ground scars and wreckage distribution were consistent with collision with terrain while in forward flight. The observations from a weather station located 3 miles east-southeast of the accident site indicated ceilings less than 500 ft and visibility less than 1 mile were likely at the time of the accident. The relative humidity had rapidly increased above 90 percent immediately before the accident, which would be indicative of cloud cover and mist at or near the surface. Witnesses living in the local area reported that the visibility at ground level was very limited, with low clouds and fog. Observations near the destination showed lowered visibility and low ceilings as the rain moved eastward through the accident area. Gusty winds ahead of the lowering ceilings would have likely created low-level wind shear. The operator's flight data monitoring system indicated that the helicopter was flying along an interstate about 300 ft above ground level (agl), which decreased to about 200 ft agl, likely as the visibility was reduced. However, the last recorded points indicated that the helicopter had climbed to about 500 ft agl, and was no longer tracking the interstate. It is likely that the VFR flight encountered instrument meteorological conditions, and the pilot was trying to maneuver to an area with greater visibility when the helicopter collided with terrain. Weather information available to the pilot before takeoff showed a cold front between the departure airport and destination, with forecasted low clouds, rain, ceilings below 600 ft, and gusty winds associated with that front. It was the pilot's responsibility to review the weather before all Part 91 flights; the chief pilot was not required to review the conditions with the pilot for such flights. Had the pilot conducted thorough preflight planning, he should have identified the deteriorating weather conditions and recognized that he could not complete the VFR flight.

Airwest holds a Part 135 Commuter and On Demand Operations certificate. Airwest was under contract with the Cochise County Sheriff to provide 30 hours of air support per month. The pilots check the weather and aircraft status themselves. They then will check-in with the Chief Pilot, review the weather, aircraft, and mission tasking. The Chief Pilot will give a verbal aircraft release as necessary for Part 135 operations. No approval was required for flights flown under Part 91 regulations, such as a repositioning flight. The National Weather Service (NWS) Surface Analysis Chart for 1700 MST depicted a cold front that stretched from just south of the accident site southwest across northern Mexico and into the eastern Pacific Ocean. A stationary front stretched from just south of the accident site southeastward into northern and central Mexico. A surface low pressure center with a pressure of 1006-hectopascals (hPa) was located in southeastern Arizona just south of the accident site. Two other surface low pressure centers were located in central and eastern Arizona with pressures of 1008-hPa. The station models around the accident site depicted temperatures in the low 40's to upper 50's Fahrenheit (F), with temperature-dew point spreads of 15° F or more south and east of the accident site and temperature-dew point spreads of 5° F or less west of the accident site, a variable wind between 5 and 20 knots, mostly cloudy skies, and moderate rain west of the accident site. Areas near and ahead of fronts and surface low pressure centers are typically areas where enhanced lift, clouds, and precipitation can occur. The cloudy skies and rainy conditions would have been expected to move from west to east across Arizona with the mid- and upper-level wind pattern. The area surrounding the accident site was documented utilizing official NWS Meteorological Aerodrome Reports (METARs) and Specials (SPECIs). The following observations were taken from standard code and are provided in plain language. AA1OV-2 Benson, Arizona, observation site (AU445) was the closest weather station to the accident site located 3 miles east-southeast of the accident site, at an elevation of 4,250 feet, and its reports were not supplemented. Benson weather at 1652 was reported as wind from 250° at 8 knots with gusts to 11 knots, temperature of 4° Celsius (C), dew point temperature of 2° C, a relative humidity of 88 percent, and an altimeter setting of 29.86 inches of mercury. Benson weather at 1702 was reported as wind from 243° at 8 knots with gusts to 13 knots, temperature of 3° C, dew point temperature of 2° C, a relative humidity of 90 percent, and an altimeter setting of 29.86 inches of mercury. Pioneer Airfield (KALK) was the closest official weather station to the accident site and had an Automated Weather Observing System (AWOS) whose reports were not supplemented. Pioneer was located 21 miles south of the accident site at an elevation of 4,767 feet. The following observations were taken and disseminated during the times surrounding the accident: Pioneer weather at 1556 reported as wind from 220° at 21 knots with gusts to 31 knots, 10 miles visibility, clear skies below 12,000 feet above ground level (agl), temperature of 10° C, dew point temperature of -1° C, and an altimeter setting of 29.88 inches of mercury. Remarks: automated station with a precipitation discriminator, peak wind from 230° at 33 knots at 1527, sea level pressure 1006.2 hPa, temperature 10.0° C, dew point temperature -1.1° C, lightning detection system with the sensor not operating. Pioneer weather at 1656 reported as wind from 210° at 14 knots, 10 miles visibility, scattered clouds at 4,200 feet agl, a broken ceiling at 5,000 feet agl, temperature of 9° C, dew point temperature of 1° C, and an altimeter setting of 29.90 inches of mercury. Remarks: automated station with a precipitation discriminator, peak wind from 220° at 31 knots at 1622 MST, sea level pressure 1006.9 hPa, temperature 8.9° C, dew point temperature 0.6° C, 6-hourly maximum temperature of 12.8° C, 6-hourly minimum temperature of 8.9° C, 3-hourly pressure increase of 0.5 hPa, lightning detection system with the sensor not operating. Tucson International Airport (KTUS) is located 6 miles south of Tucson, Arizona, and had an automated surface observation system (ASOS) whose reports were supplemented by air traffic control. Tucson is located 29 miles west-northwest of the accident site, at an elevation of 2,643 feet, and had a 12° easterly magnetic variation. The following observations were taken and disseminated during the times surrounding the accident: Tucson weather at 1648 reported as wind from 010° at 4 knots, 4 miles visibility, light rain, mist, broken ceiling at 600 feet agl, overcast skies at 1,100 feet agl, temperature of 6° C, dew point temperature of 4° C, and an altimeter setting of 29.95 inches of mercury. Remarks: automated station with a precipitation discriminator, one-hourly precipitation of 0.08 inches. Tucson weather at 1653 reported as wind calm, 3 miles visibility, moderate rain, mist, a broken ceiling at 600 feet agl, overcast skies at 1,100 feet agl, temperature of 6° C, dew point temperature of 4° C, and an altimeter setting of 29.95 inches of mercury. Remarks: automated station with a precipitation discriminator, sea level pressure 1013.0 hPa, one-hourly precipitation of 0.08 inches, 6-hourly precipitation of 0.14 inches, temperature 6.1° C, dew point temperature 4.4° C, 6-hourly maximum temperature of 15.6° C, 6-hourly minimum temperature of 6.1° C, 3-hourly pressure increase of 0.5 hPa. The observations from Benson indicated both ceilings less than 500 feet and visibility less than 1 mile (LIFR – Low IFR) were likely at the time of the accident near the accident site. Benson relative humidities rapidly increased to 79 percent by 1622 and the relative humidities increased above 90 percent by 1702 which would likely be indicative of cloud cover and mist at or near the surface or 4,250 feet msl. Tucson experienced similar conditions to Benson though conditions at Tucson were only IFR with the ceilings below 1,000 feet. Breezy to windy conditions were present ahead of the lowering visibility and ceiling conditions as seen in the Pioneer and Sierra Vista observations, with ceilings lowering at both of those locations as the rain moved eastward across southern Arizona after the accident time. The gusty winds ahead of the lowering ceilings and visibilities would have likely created low-level wind shear (LLWS). Sierra Vista was the closest site with a Terminal Aerodrome Forecast (TAF). The 1206 Sierra Vista TAF expected wind from 300° at 15 knots with gusts to 25 knots, 7 miles visibility, light rain, a broken ceiling at 2,000 feet agl, occasional light to moderate turbulence in clear air from the surface to 9,000 feet, light rime icing in cloud from 3,000 to 6,000 feet, and minimum altimeter setting of 29.92 inHg starting around 1600 and valid through 1900. The Tucson TAF issued at 1513 was the valid TAF before the approximate 1540 to 1550 takeoff time. The 1513 Tucson TAF expected wind from 320° at 8 knots, greater than 6 miles visibility, light rain, scattered clouds at 600 feet agl, and an overcast ceiling at 1,500 feet agl. Temporary conditions between 1500 and 1900 of 5 miles visibility, light rain, mist, and a broken ceiling at 600 feet agl was forecast. The National Weather Service Office in Tucson, Arizona, issued an Area Forecast Discussion (AFD) at 1423. The aviation section of the AFD mentioned IFR conditions developing due to lowering ceilings and precipitation from Tucson eastward starting around 1800. The aviation section of the AFD also mentioned the gusty southwest wind ahead of the front with gusts to 35 knots. "MVFR (marginal VFR) WITH POSSIBLE IFR CONDITIONS DEVELOPING DUE TO LOWERING CEILINGS AND SHOWERS...FIRST AT KTUS/KO