On June 12, 1999, at 1545 mountain daylight time, a Piper PA-28-140, sustained substantial damage when it settled to the ground following takeoff from a private airstrip located approximately 4 miles northwest of Grand Junction, Colorado. The commercial pilot/flight instructor and his private pilot certificated passenger were not injured. The flight was operating under Title 14 CFR Part 91 when the accident occurred and no flight plan was filed. Visual meteorological conditions prevailed. In a telephone interview, and in the written section of the Pilot Operator Report Form, the pilot said he had a left crosswind of 8 to 10 knots and that as the aircraft became airborne he encountered a wind shear causing the aircraft to settle back to the ground off the end of the runway. Airport elevation was 4,500 feet pressure altitude and the density altitude was calculated to be 7,700 feet. The runway was listed at 2,250 feet in length with a dirt surface. Runway slope was unknown. According to the National Weather Service observation at Walker Field, the Grand Junction Municipal Airport, located approximately 4 miles from the private airport, wind at the time was from 290 degrees at 10 knots with gusts to 17 knots. The pilot said he took off to the east. According to performance information in the flight manual, the maximum certificated gross weight of the aircraft is 2,150 pounds. According to Federal Aviation Administration information on the occupants, the combined weight of the people was 370 pounds. The pilot said he had 20 gallons of fuel aboard which weighed 120 pounds and the operating empty weight was 1,650 pounds. Thus the calculated weight of the aircraft at takeoff was 2,080 pounds, 70 pounds below the maximum certificated gross weight. Aircraft performance data also provided information that the take off roll chart does not extend above 7,000 feet density altitude and at that altitude, based on a hard surface runway, no slope, and no wind, the takeoff distance to rotation was 1,750 feet at the maximum certificated gross weight of the aircraft. A warning on the chart stated that extending performance curves off the chart above the maximum altitude was not permissible.