Castle Rock, CO, USA
N535SP
GLASAIR AVIATION USA LLC SPORTSMAN GS-2
A review of air traffic control (ATC) recordings indicated that, after the airplane crossed over the mountains, the pilot checked in with the Denver terminal radar approach controller and expressed concern about the weather at her destination airport. After receiving weather for a closer airport, which included visibility 1.5 miles in mist with a 400-foot overcast ceiling, the pilot changed her destination to that airport. About 3 minutes later, the pilot asked the controller if other pilots had reported icing during descent, and the controller responded that other pilots had reported icing in cloud tops about 9,000 feet mean sea level (msl). The pilot advised that she wanted to change back to her original destination, and, shortly later, the controller cleared the approach. About 20 minutes later, the pilot advised the controller that the airplane was "picking up rime ice," and, about 3 minutes later, she again asked for clearance to the intermediate airport; the controller cleared that approach. During the approach, the controller issued three low altitude alerts because the airplane was not maintaining the assigned altitudes, and he provided the pilot with the weather information for the destination airport, which included visibility 2 miles in mist, 400 feet overcast, and temperature and dew point below freezing at -1° C. The pilot reported being established on the approach about 3 miles from the final approach fix shortly before the controller issued the third low altitude alert. After this alert, the pilot responded that the airplane was climbing and maintaining altitude and was established on the approach. Shortly later, the controller asked the pilot to indicate the airplane's altitude, but the pilot did not respond. Radar track data indicated that the airplane was about 6,800 feet msl before radar and radio contact were lost. The airplane subsequently descended and impacted terrain. The airplane likely accumulated ice when the pilot continued flight into known icing conditions, which adversely affected its performance and resulted in a loss of airplane control. ATC services were adequate, and no deficiencies were noted.
HISTORY OF FLIGHT On October 28, 2013, about 1900 mountain daylight time (MDT), a Glasair Sportsman GS-2, N535SP, impacted terrain after contact with a utility wire near Castle Rock, Colorado. The commercial pilot sustained serious injuries and the aircraft was substantially damaged. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a positioning flight. Instrument meteorological conditions prevailed for the flight, which was operated on an instrument flight rules flight plan. The flight originated from Yampa Valley Airport (KHDN), Hayden, Colorado at 1743, and Front Range Airport (KFTG), Denver, Colorado was the intended destination. The pilot was delivering the accident airplane, on behalf of the manufacturer, to a relative of registered owner who was awaiting the pilot's arrival into KFTG. Following delivery, the pilot was scheduled to conduct instruction and familiarity flight training with the registered owner's relative in the accident airplane while flying cross-country from KFTG to Virginia. PERSONNEL INFORMATION The pilot, age 32, held a commercial pilot certificate with ratings for airplane single-engine land, airplane multiengine land, instrument and flight instructor (airplane single-engine and multiengine). She was issued a second class airman medical certificate on January 3, 2013, with no limitations or waivers. The pilot reported a total time of 5,055 hours, with 903 in the Glasair Sportsman. She had flown 218 hours in the last 90 days and 81 in the last 30 days. Her latest flight review occurred on March 29, 2013. AIRCRAFT INFORMATION The high wing airplane, serial number 7369, was manufactured in 2012. The airplane was tail wheel with fixed main landing gear. It was built in the Glasair factory as a demonstration airplane; however, it was registered with the Federal Aviation Administration (FAA) as an experimental aircraft certificate. The airplane was powered by a Superior XP-IO-400-J4HD9 engine equipped with a controllable pitch, two-blade propeller. The airplane was equipped with an Advanced Flight Systems 3400s multi-function display. The last annual inspection on the airplane occurred on January 7, 2013, at manufacturing completion of the airplane. The aircraft was not equipped with ice protection and was not certificated for flight in icing conditions. AIR TRAFFIC CONTROL INFORMATION An NTSB air traffic specialist reviewed the air traffic control information pertaining to the flight. Review of the radar track and radio communications with air traffic control (ATC) during the pilot's inbound flight from KHDN showed the pilot departed at 1801 under visual flight rules. She told air traffic control she intended to operate under visual flight rules at 13,500 feet until crossing the mountains, and would then activate an instrument flight rules (IFR) flight plan with ATC and request clearance into KFTG. At 1823, at 13,700 feet and approximately 56 miles west of KFTG (across mountains), the pilot checked in with ATC and advised of her intention to pick up her IFR clearance to FTG as she "got a little closer." She also expressed concern about the weather at KFTG. The controller provided weather information for Centennial Airport (KAPA) which is approximately 22 miles southwest of KFTG. The controller reported visibility at 1.5 miles in mist with 400 foot overcast. The pilot changed her destination to KAPA. The controller advised the pilot to maintain VFR until clear of the mountain ranges and then he would issue the pilot an IFR clearance to KAPA. At 1826, the pilot asked ATC if other aircraft had reported icing during descent. The controller responded that icing had been reported west of Denver in cloud tops around 9,000 feet. The pilot advised ATC she wanted to change back to her original destination, KFTG. At 1829, ATC cleared N535SP to KFTG via radar vectors. At 1848, while receiving radar vectors from ATC to KFTG, the pilot advised that the airplane was "picking up rime ice." The controller asked about the severity of the icing and the pilot advised it was light to moderate. At 1851, about 18 miles from KFTG, the pilot asked how far away she was from intercepting the approach to KFTG. The controller responded that a turn to intercept was projected to be approximately 6 miles. The pilot acknowledged and then asked if there was any chance she could go to KAPA. The controller cleared the pilot to KAPA via radar vectors and told her to expect the ILS runway 35R approach at KAPA. When the controller asked the pilot for the reason for the destination change, the pilot responded that she needed to "get something a little bit closer." At 1852, the pilot asked for vectors to the global positioning system (GPS) 35R approach. The controller advised N535SP to expect the GPS runway 35R approach. One minute later, the controller asked the pilot if she required assistance. The pilot responded that she did not, but that she needed to get on the ground as the airplane was picking up more ice and had "been down here for a little too long." The controller acknowledged and issued a low altitude alert to the pilot, advising that he was showing her to be 300 feet below the assigned altitude of 8,000 feet. The controller issued the current altimeter setting, 30.04 inches of mercury. The pilot acknowledged and indicated she was resetting her altimeter. The controller then asked the pilot if she was experiencing greater than light to moderate icing. The pilot responded, "negative," but said that the ice was "sticking on there." At 1856, the controller advised the pilot that he was showing her altitude at 7,600 feet and asked if she was able to maintain altitude. The pilot responded that she could maintain altitude and was climbing. The controller advised that ATIS information Juliet was current for KAPA. The controller then issued another low altitude alert, stating that N535SP was at 7,300 feet. The pilot acknowledged with "okay," followed by "I'm maintain[ing] 7,200 feet." The controller acknowledged and advised the pilot she was 3.5 miles from the final approach fix. At 1859, the controller advised the pilot she was 2.9 miles south of the final approach fix and asked her to advise when she was established on the approach. The pilot responded that she was established and was now maintaining 7,000 feet. Twenty seconds later the controller issued another low altitude alert advising the pilot that he observed the airplane at 6,800 feet descending. The pilot responded that she was climbing back up, maintaining altitude and that she was established on the approach. At 1901, the controller asked the pilot to say altitude. There was no response. Radar track data indicated the airplane was at 6,800 feet mean sea level before radar and radio contact was lost. No distress calls or further communications were received from the pilot. METEROLOGICAL INFORMATION An NTSB meteorology specialist reviewed the meteorological information pertaining to the flight. A review of the data revealed the pilot obtained several weather briefings prior to the flight utilizing a computerized data base called Direct User Access Terminal Service (DUATS). The last weather briefing occurred at 1738 MDT, which indicated that IFR to LIFR conditions were reported and forecast to continue at the destination airport and in the immediate vicinity. The briefing included the Airmen's Meteorological Information (AIRMET) Sierra for IFR and mountain obscuration conditions over the area. No advisories for turbulence or icing conditions were forecast in the AIRMET for the destination or route of flight. However, several pilot reports of light rime to mixed icing in the area were included in the briefing. Terminal Aerodrome Forecast (TAF) was issued for KAPA by the National Weather Service (NWS) Denver/Boulder Weather Service Forecast office (WSFO). The amended forecast issued at 1611 and current at the time of the preflight briefing expected low instrument flight rules (LIFR) conditions with a wind from 060° at 5 knots, visibility 3 miles in mist, ceiling broken at 300 feet above ground level (agl), overcast clouds at 600 feet agl, with a temporary period from 1600 through 2000 MDT of visibility 1 mile in light drizzle and mist. The next scheduled forecast was issued at 1729 MDT, within one-half hour of the departure from Hayden, which expected the LIFR conditions to continue with a temporary period of light freezing drizzle and mist from 1600 through 2000 MDT. Historical weather information for the original destination airport, KFTG, was not available at the time of meteorological review. However, the following weather conditions were reported at KDEN, located 6 nautical miles northwest of KFTG and 27 miles north of the accident site: The 1753 METAR observation for Denver International Airport (KDEN) was wind 100 degrees at 8 knots, visibility one half statute mile in mist, overcast clouds at 200 feet. Temperature -1 degree Celsius, dew point -1 degree Celsius. Altimeter 30.02 inches of mercury. Remarks: Surface visibility 2 statute miles. The 1834 special METAR observation for KDEN was wind 100 degrees at 8 knots, visibility 1 statute mile in mist, overcast clouds at 200 feet. Temperature -1 degree Celsius, dew point -1 degree Celsius. Altimeter 30.03 inches of mercury. Remarks: Surface visibility 4 statute miles. The 1853 routine METAR observation for KDEN was wind 090 degrees at 6 knots, visibility 1 statute mile in mist, overcast clouds at 200 feet. Temperature -1 degree Celsius, dew point -1 degree Celsius. Altimeter 30.04 inches of mercury. Remarks: Surface visibility 5 statute miles. The following weather conditions were reported at KAPA, located approximately 9 miles north of the accident site: The 1753 routine METAR observation for KAPA was wind 060 degrees at 6 knots, visibility 1 and a half statute miles in mist, overcast clouds at 400 feet, temperature -1 degree Celsius, dew point -1 degree Celsius, altimeter 30.01 inches of mercury. The 1804 special METAR observation for KAPA was wind 080 degrees at 5 knots, visibility 2 statute miles in mist, overcast clouds at 400 feet, temperature -1 degree Celsius, dew point -1 degree Celsius, altimeter 30.03 inches of mercury. At 1853, the KAPA automated surface observing system (ASOS) reported the following weather conditions: wind from 110 degrees true at 6 knots, visibility 2 miles in mist, ceiling overcast at 400 feet agl, temperature and dew point -1 degree Celsius, altimeter 30.03 inches of mercury. WRECKAGE AND IMPACT INFORMATION The main wreckage contained all primary structural components and flight control surfaces. Flight control continuity was confirmed from the flight control surfaces to their respective cockpit controls. An engine examination indicated no anomalies with the engine and signatures consistent with propeller rotation at the time of impact were observed. TESTS AND RESEARCH The airplane was equipped with an Advanced Flight Systems AF-3400 Electronic Flight Instrumentation System (EFIS) and aircraft monitoring system. The NTSB Recorders Laboratory examined the unit. The EFIS receives GPS time from the aircraft's GPS receiver. The EFIS also records information concerning altitude, heading, airspeed, vertical speed, ground speed, pitch, roll, and engine parameters. Of the approximately 9 hours and 44 minutes of data extracted from the multifunctional display (MFD), the last 88 minutes and 25 seconds were determined to be related to the accident flight. The displays present navigation and flight data to the pilot on liquid-crystal computer screens, replacing the individual gauges and flight instruments found in earlier generation general aviation airplane cockpits. Two plots of the MFD data were produced by the NTSB Vehicle Recorder laboratory and are available with the docket material associated with this accident. The plots cover the time period from 17:32:00 MDT to 19:02:00 MDT. Plot one contains the entire accident flight. Plot two contains the last 40 minutes of the accident flight in greater detail. According to the downloaded data, the airplane departed at approximately 1739. The airplane climbed to 13,500 feet agl, then briefly to 14,000 feet agl before descending back to approximately 13,500 feet agl. Approximately 1831 MDT, the airplane began descending from 13,500 feet agl to 12,000 feet agl. The airplane maintained 12,000 feet agl for approximately 3 minutes and began descending again until it reached about 7,900 feet agl, at approximately 1846. Airspeed at this time was approximately 110 knots; it then began a steady loss of airspeed to approximately 65 knots at 1859. Approximately 1851, the vertical speed began rapidly fluctuating, from a 600 feet per second climb to 600 feet per second descent. This fluctuation continued until the end of the recording. At 1851, the airplane began a constant, gradual descent until impact, approximately 6,500 feet agl. ADDITIONAL INFORMATION When local law enforcement arrived on scene, they observed ice on the leading edge (left side) of the horizontal stabilizer. During NTSB interviews with the pilot, she stated she was aware of pilot reports (PIREPS) for icing along her route of flight. However, the PIREPS were "an hour old." She recalled the temperature was about zero at KFTG but there were positive temperatures "for the tops." She stated she "did not think she would pick up ice." The pilot reported that when she noticed she was accumulating ice, she advised air traffic controllers and requested a vector closer to KAPA. She never declared an emergency to ATC, explaining she never had to do so in the past.
The pilot’s improper decision to continue flight into known icing conditions, which adversely affected the airplane’s performance and resulted in a loss of airplane control.
Source: NTSB Aviation Accident Database
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