HISTORY OF FLIGHTOn August 5, 2018, about 1500 eastern daylight time, a Schweizer SGS 2-33A glider, N2832H, was substantially damaged when it impacted trees shortly after takeoff from Harford County Airport (0W3), Churchville, Maryland. The flight instructor and passenger were not injured. The tow plane, a Bellanca/American Champion Scout 8GCBC, N88059, was undamaged and the commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which was operated under the provisions of Title 14 Code of Federal Regulations Part 91. According to the glider flight instructor, while attempting to take off the tow airplane became airborne about 100 ft later than on earlier flights that day. When it became apparent to him that they might not clear trees located about 1,300 ft off the departure end of the runway, he released from the tow airplane, made a right turn to avoid the tree line, and executed a forced landing in a nearby field. He had completed about 130° to 150° of the turn when the left wing impacted trees. According to the pilot of the tow airplane, the weather conditions were "the worst humidity and heat and slowest rate of flying" and the takeoff roll was long. He stated that they would have normally used a sod runway that was oriented into the wind and longer, but it was water logged, so they were using the grass area paralleling the southern edge of runway 28, taking off and landing in a westerly direction. That area was uphill, shorter, and had some wet areas. He stated the initial climb felt normal given the runway and weather conditions and that he noted no abnormal performance issues with the tow plane. He estimated the glider would clear the trees by 20 ft, but then felt the glider drop off and looked back to see it turning toward an open field. He reported that there were no mechanical malfunctions or failures with the tow airplane that would have precluded normal operation and reported no problems during subsequent flights in the airplane. PERSONNEL INFORMATIONThe flight instructor held a commercial pilot certificate with ratings for airplane single and multi-engine land and sea, instrument airplane, and glider. He held a flight instructor certificate with a rating for glider. His most recent Federal Aviation Administration (FAA) 2nd class medical certificate was issued July 2017. He reported 5,100 total hours of flight experience, with 975 hours in gliders. The tow plane pilot held a commercial pilot certificate with ratings for airplane single engine land, instrument airplane, rotorcraft-helicopter, and glider. METEOROLOGICAL INFORMATIONAt 1445, the reported weather at Martin State Airport (MTN), about 17 nautical miles southwest of the accident site, included clear skies, 10 miles visibility, and wind from 160° magnetic at 8 knots. The temperature was 32° C, the dew point was 24° C, and the altimeter setting was 30.16 inches of mercury. At 1451, the reported weather at New Castle Airport (ILG), about 35 miles east of accident site, included clear skies, 10 miles visibility, and wind from 160° magnetic at 8 knots. The temperature was 32°C, the dew point was 21°C, and the altimeter setting was 30.14 inches of mercury. The calculated density altitude at the time of takeoff was about 2,500 feet. According to an FAA Icing Probability Chart, the atmospheric conditions at the time of the accident were "conducive to icing at glide [idle] power." WRECKAGE AND IMPACT INFORMATIONExamination of the wreckage by an FAA inspector revealed that the glider was substantially damaged in the accident sequence. The left wing displayed damage consistent with tree impact. The rear portion of the fuselage was fractured just aft of the trailing edge of the wing and rested 90° to the right of the longitudinal centerline of the forward fuselage. The left wing leading edge was impact-damaged in multiple areas. ADDITIONAL INFORMATIONThe Civil Aviation Authority of the United Kingdom published Safety Sense Leaflet 7C, "Aeroplane Performance." The publication cautioned that operating from poor surfaces, such as long or wet grass, mud, or snow, often results in accidents that could be avoided if pilots were aware of the performance limitations of their airplanes. The publication also provided a list of variables that often affect performance and guidelines for calculating the effect of these variables on airplane performance in the absence of guidance from the manufacturer. Among these factors was a 30% increase in takeoff distance on wet grass runways, a 10% increase in takeoff distance with a 2% upslope, and a 20% increase in takeoff distance with a tailwind component of 10% of lift-off speed." According to FAA Pamphlet FAA-P-8740-2, Density Altitude: Whether due to high altitude, high temperature, or both, reduced air density (reported in terms of density altitude) adversely affects aerodynamic performance and decreases the engine's horsepower output. Takeoff distance, power available (in normally aspirated engines), and climb rate are all adversely affected. Landing distance is affected as well; although the indicated airspeed (IAS) remains the same, the true airspeed (TAS) increases. From the pilot's point of view, therefore, an increase in density altitude results in the following: • Increased takeoff distance. • Reduced rate of climb. • Increased TAS (but same IAS) on approach and landing. • Increased landing roll distance. Because high density altitude has particular implications for takeoff/climb performance and landing distance, pilots must be sure to determine the reported density altitude and check the appropriate aircraft performance charts carefully during preflight preparation. A pilot's first reference for aircraft performance information should be the operational data section of the aircraft owner's manual or the Pilot's Operating Handbook developed by the aircraft manufacturer. In the example given in the previous text, the pilot may be operating from an airport at 500 ft msl, but he or she must calculate performance as if the airport were located at 5,000 feet. A pilot who is complacent or careless in using the charts may find that density altitude effects create an unexpected –and unwelcome – element of suspense during takeoff and climb or during landing. According to the Glider Flying Handbook (FAA, 2013, p 7-3) "normal takeoffs are made into the wind." Review of the operator's standard operating procedures for this flight operation indicated that "normal sailplane traffic patterns will be into the prevailing winds" and that "no take-offs or landings are to be made against the normal take-off direction, except in an emergency or for training purposes." Further, the procedures state that "the tow pilot and the glider PIC [pilot-in-command] are both responsible for ensuring that sufficient take-off distance is available according to emergency release possibilities and the PIC's proficiency."