On January 3, 2004, about 1530 mountain standard time, a Cessna 421C, N911EA, landed hard in gusty wind conditions at the Window Rock Airport, Window Rock, Arizona. Scenic Aviation, Inc., was operating the airplane under the provisions of 14 CFR Part 135. The airline transport pilot and four passengers were not injured; the airplane sustained substantial damage. Instrument meteorological conditions prevailed, and an instrument flight plan had been filed. The flight originated from the Flagstaff Pulliam Airport, Flagstaff, Arizona, at 1443, with a planned destination of Window Rock. During a telephone conversation with the National Transportation Safety Board investigator-in-charge, the pilot reported that he was attempting to execute the VOR/DME-A circling approach to runway 02. While performing the approach, he noted gusty wind conditions and freezing temperatures. Upon touchdown, the airplane hit hard on the left main landing gear. The pilot opined that due to the severe icing conditions, the airframe possibly accumulated a layer of ice, which contributed to the premature landing stall. At 1510, the weather observation facility (automated surface observing system) at Window Rock Airport reported wind from 260 degrees at 14 knots; light snow; mist; 1 statue mile visibility; broken cloud layer at 900 feet and 1,500 feet; and overcast at 2,200 feet; temperature 1 degree Celsius; dew point -1 degree Celsius; and an altimeter setting of 29.76 inches of mercury. At 1553, the facility reported wind from 290 degrees at 14 knots, gusting to 26 knots; light snow; freezing conditions and fog; 0.5 statue mile visibility; broken cloud layers at 700 feet and 1,300 feet; and overcast at 1,800 feet; temperature -1 degree Celsius; dew point -2 degree Celsius; and an altimeter setting of 29.79 inches of mercury. The Federal Aviation Administration-H-8083-3 Airplane Flying Handbook states, "Degradation of all flight characteristics and large performance losses can be expected with ice accumulation. Ice will accumulate unevenly on the airplane. It will add weight and drag (primarily drag), and decrease thrust and lift." Despite numerous attempts by a Safety Board investigator, both the pilot and operator failed to submit a NTSB Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2).