Incident Summary
A flight instructor reported that during a takeoff climb from a grass runway with a student pilot at the controls, the climb rate became stagnant at about 25 feet above ground level. The instructor instructed the student to lower the nose slightly, but after several seconds the airplane did not resume a normal climb rate. The instructor then took the flight controls and found them sluggish, with a sensation similar to wind swirls and downdrafts. Subsequently, the instructor made a small left turn toward a small gap in the tree line ahead, and the airplane impacted a heavily wooded area. Both wings and the fuselage sustained substantial damage.
Weight and Balance
Postaccident interviews with the NTSB investigator-in-charge revealed that the student pilot and flight instructor each provided their personal weights and reported a total of 10 gallons of fuel on board at takeoff. Based on this information, the takeoff weight was calculated at 1,389 lbs, which exceeded the maximum gross weight of 1,250 lbs published in the airplane's pilot operating handbook (POH) by 139 lbs. The airplane's center of gravity at takeoff was within limits at 18.65 inches (range 12.4 to 22.0 inches). The flight instructor reported that the airplane departed loaded at gross weight, while the student pilot stated that the instructor did not discuss weight and balance with him prior to flight. The instructor reported no preaccident mechanical malfunctions or failures that would have precluded normal operation.
Weather and Performance
An automated weather observation station located 8 nautical miles southwest reported wind from 200° at 5 knots, temperature 82°F, dewpoint 54°F, and a barometric setting of 29.76 inches of mercury around the time of the accident. The calculated density altitude from that station was 2,648 feet. The flight instructor reported taking off from runway 20, which was 2,600 feet in length. The airplane's POH did not publish takeoff performance information. According to the Federal Aviation Administration Koch Chart, given the surrounding temperature and field elevation, the airplane would have likely experienced a 30% increase to the normal takeoff distance and a 25% decrease in the normal climb rate.
Examination and Excerpts
The FAA Pilot's Handbook of Aeronautical Knowledge discusses the effect of weight on flight performance, stating that a heavier gross weight results in a longer takeoff run and shallower climb. It also addresses runway surface conditions, noting that surfaces such as grass increase ground roll due to tire resistance. The grass runway in this incident likely contributed to the takeoff challenges, but no explicit causal link was established in the source.