Cessna U206F N8737Q accident near Arcadia, Florida

Probable cause

The pilot’s decision to take off in high density altitude conditions with the airplane over its maximum gross weight, due to the pilot’s improper weight and balance calculations, which resulted in the airplane’s inability to climb or maintain altitude.

NTSB analysis

The pilot stated that during the water takeoff, he used 10 degrees of flaps to get the airplane on "plane." Once the airplane began to climb, he added another 10 degrees of flaps to climb. The airplane climbed to about 400 feet but would not maintain altitude. There was no loss in engine power, and the airplane began to descend. The pilot executed a forced landing into a field, and the airplane collided with trees. After recovery of the airplane, the engine was removed and test run. No preaccident mechanical malfunctions or failures were found that would have precluded normal engine operation.

A review of the performance chart revealed that the airplane, in a clean configuration and at a maximum gross weight of 3,800 pounds, should have been able to maintain a rate of climb of 600 feet per minute at about 65 knots. The density altitude at the time of the accident was about 2,300 feet. Although the pilot estimated the gross weight was 3,695 pounds, postaccident weight and balance calculations revealed the estimated weight of the airplane at takeoff was 3,855 pounds, which was 55 pounds above the maximum allowable gross weight. High density altitude and increased gross weight both adversely affect an airplane's climb performance. The presence of either or both conditions requires pilot vigilance to maintain adequate airspeed during takeoff and climb. Aircraft performance can become marginal in high density altitude conditions, and it may be necessary to reduce aircraft gross weight for safe operations. It is likely that the high density altitude combined with operation over the airplane’s maximum permitted takeoff gross weight resulted in the airplane's inability to climb or maintain altitude. These factors would both reduce the performance of the airplane.

Text from the NTSB. Open the NTSB docket for ERA11LA451 for the full record.