Amateur-built CURTISS JN4D N8262 accident near Bowling Green, Kentucky

Probable cause

The pilot’s exceedance of the biplane’s critical angle of attack during initial climb, which resulted in an aerodynamic stall and collision with trees.

NTSB analysis

The pilot of the experimental, amateur-built biplane reported that, following a normal initial climb, about 100 ft above the ground, the biplane started an uncommanded left turn, followed by a descent. He added that it became apparent that the flightpath was into the tree line, and he "attempted to climb to possibly maintain at least an altitude to clear the trees, but to no avail, nearly stalling." Subsequently, the biplane impacted the trees.

The biplane sustained substantial damage to the wings and fuselage.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the biplane that would have precluded normal operation.

The pilot added that the biplane is "not very stable once in a flying configuration, any air mass (gusts) change can disturb the balance and result in self-induced turns, climbs and descents. These movements have to be countered immediately because of the relative size (small) of control surfaces (rudder, ailerons). And corrections are slow, possibly resulting in loss of altitude. Pilots expect these upsets and become alert for them."

The automated weather observation system on the accident airport reported, about the time of the accident, the wind was from 360° at 5 knots. The pilot was departing from runway 03. The calculated density altitude was 1,897 ft.

Text from the NTSB. Open the NTSB docket for GAA17CA488 for the full record.