History of Flight
On January 19, 2016, about 1231 central standard time, a Socata TBM 700 airplane, N602MA, was substantially damaged after landing short of Runway 18 at Colonel James Jabara Airport (AAO), Wichita, Kansas. The private pilot and passenger were not injured. The airplane was registered to and operated by Premier Furnace Specialists, Inc. under 14 CFR Part 91 as a business flight. Day instrument meteorological conditions prevailed for the flight, which departed on an IFR flight plan from Schenck Field Airport (ICL), Clarinda, Iowa, about 1137.
The pilot stated that after departure, he encountered clouds at his cruising altitude of flight level 200. He was advised of icing along the route and activated the de-ice boots to automatic, turned on propeller heat, and the heated windshield, all of which appeared to operate normally. During descent into AAO, the pilot observed ice accumulating on the wing leading edges, but the de-ice boots seemed to keep the leading edges clear.
The pilot flew an ILS approach to Runway 18 with the autopilot engaged. After exiting IMC on final approach at about 1,200 ft AGL, he lowered flaps to the takeoff setting and extended the landing gear. Descending through about 1,000 ft AGL, the airplane shuddered and experienced an immediate increase in sink rate. The pilot applied full engine power, but the airplane continued to sink and touched down 1,463 ft short of the runway threshold. The airplane skidded 460 ft, during which the landing gear struck a ground hog hole, causing the airplane to nose over and damage the firewall and wing spar.
Federal Aviation Administration (FAA) personnel examined the accident site about 1500 and observed approximately 1/8 to 1/4 inch of ice on both wings aft of the de-ice boots to the trailing edge. The vertical stabilizer had similar ice accumulation aft of its de-ice boot.
Meteorological Information
At 1239, the weather observation station at AAO reported: wind 050 degrees at 8 knots, visibility 2 ½ miles in mist, broken clouds at 700 ft AGL, overcast at 1,100 ft AGL, temperature -2°C, dew point -3°C, altimeter 30.13 inches of mercury.
At 1233, the weather observation station at Wichita Dwight D. Eisenhower National Airport (ICT), about 12 miles southwest of AAO, reported: wind 020 degrees at 7 knots, visibility 2 miles in light drizzle and mist, overcast at 800 ft AGL, temperature -1°C, dew point -3°C, altimeter 30.13 inches of mercury.
The terminal aerodrome forecast (TAF) for ICT issued at 0854, used by the pilot for preflight planning, expected MVFR conditions at the estimated arrival time with wind 110 degrees at 12 knots, unrestricted visibility, and overcast at 1,500 ft AGL. Light freezing drizzle was forecast between 1300 and 1900.
At the time of the accident, the National Weather Service had an AIRMET covering the route for moderate icing from the freezing level to 18,000 ft MSL. The freezing level was from the surface to 7,000 ft MSL. Forecast icing products from 4 hours prior indicated a high probability of encountering moderate icing over the route and Wichita area, with some potential for supercooled large drop conditions.
During the period around the accident, there were 14 pilot reports of icing along the route, ranging from trace to moderate intensity, with light intensity most frequent (10 reports). Ice types included rime (5 reports), clear (4), and mixed (3). No severe icing events were reported.
The official ASOS observations at AAO showed visibility rapidly decreasing from 8 miles at 1154 to 2 ½ miles in mist at 1239. The ASOS did not detect any measurable precipitation. The ASOS Light Emitting Diode Weather Identifier (LEDWI) sensor cannot detect very light precipitation (less than 0.01 inch per hour), which occurs with mist or freezing drizzle. The ASOS does not report freezing drizzle.
Additional Information
The pilot operating handbook (POH) for the aircraft, certified for flight into known icing, provides guidance: ice on unprotected surfaces may change aerodynamic characteristics; stall speeds may increase up to 15 KIAS at flaps-takeoff and up to 10 KIAS at flaps-landing. Minimum recommended speeds for flight into known icing are 110 KIAS at flaps-takeoff and 90 KIAS at flaps-landing (based on the accident weight).
The POH notes that severe icing may result from environmental conditions outside the airplane's certification envelope. Flight in freezing rain, freezing drizzle, or mixed icing (supercooled water and ice crystals) may cause ice buildup on protected surfaces beyond the ice protection system's capability, or ice may form aft of protected surfaces. This ice may not be shed by the ice protection systems and can degrade performance and controllability.
FAA Advisory Circular 91-47B, 'Pilot Guide: Flight in Icing Conditions,' advises: determine if freezing drizzle or rain is reported and avoid those areas; use higher approach speed when carrying ice; carry power on flare and flare slightly faster than normal if carrying ice.
A Piper PA-46 operating northeast of Wichita around the same time also encountered significant icing and made an emergency off-field landing. That pilot was unable to maintain altitude and experienced a stall buffet, leading to a forced landing (NTSB case GAA16CA107).
Tests and Research
On January 28, 2016, the FAA and aircraft manufacturer performed an examination and operational test of the airplane's de-ice systems. The de-ice boots, pitot/stall vanes, and windshield de-ice systems all performed normally; no anomalies were found. The flaps were observed near the takeoff position.
The airplane was equipped with a Garmin G1000 system. Downloaded flight data from the last 20 seconds show:
- 1230:59 to 1231:11: airspeed decreased from 102 to 92 KIAS, engine torque from 20% to 8%.
- 1231:11: autopilot disconnected.
- 1231:14: airspeed decreased to 89 KIAS, descent rate increased, airplane banked 10° left.
- 1231:16: engine torque increased to 110% (normal engine response), airplane banked 24° right.
- 1231:19: approximate ground impact time.