Schweizer SGS233 N2832H accident near Churchville, Maryland

Probable cause

The pilots' decision to take off from a wet, upsloping turf runway with a quartering tailwind and elevated density altitude conditions, which degraded takeoff and climb performance and resulted in the glider flight instructor's decision to discontinue the takeoff and the glider's subsequent impact with trees. Also causal was the pilots' failure to adhere to the operator's standard operating procedures, which prohibited takeoff with a tailwind.

NTSB analysis

The commercial pilot of the tow airplane stated that he was conducting the glider tow operations from an upsloping turf surface that was shorter than his usual takeoff area and was wet in some areas. He reported that the takeoff roll was long due to the humid, hot weather conditions, but he estimated that the glider would clear the tree line off the end of the runway by at least 20 ft. The flight instructor in the glider reported that the tow airplane became airborne about 100 ft later than on earlier flights that day. During the tow aloft, when it became apparent to him that they might not clear trees that were located about 1,300 ft off the end of the runway, he released the glider from the tow airplane, made a right turn to avoid trees, and attempted to execute a forced landing in a nearby field. He had completed about 130° to 150° of the turn when the glider's left wing impacted trees. The pilot of the tow airplane reported there were no mechanical malfunctions or failures with the tow airplane that would have precluded normal operation.

The wind conditions reported at nearby airports included a quartering tailwind at 8 knots. Additionally, the calculated density altitude at the time of takeoff was about 2,500 ft, which would have reduced the tow airplane's climb rate by about 20% and increased its takeoff distance by about 26%. The tailwind, density altitude, runway upslope, and wet turf likely resulted in takeoff and climb performance of the tow airplane that was inadequate for the glider tow operation. The pilots likely did not adequately assess the multiple factors negatively impacting takeoff and climb performance and did not adhere to the operator's standard operating procedures, which prohibited takeoff with a tailwind. Although the conditions were conducive to carburetor icing at glide power, the tow airplane was operating at takeoff power; therefore, it is unlikely that ice would have accumulated at the higher power setting.

Text from the NTSB. Open the NTSB docket for ERA18LA211 for the full record.