Cessna A185 N185SC accident near Klamath Falls, Oregon

Probable cause

The pilot's improper landing flare, which resulted in the airplane porpoising and the subsequent loss of directional control.

NTSB analysis

The pilot receiving instruction in a high performance tailwheel-equipped airplane reported that during the initial touchdown the airplane porpoised, then settled onto the ground in a three point landing attitude. The pilot further reported that during the landing roll the airplane veered to the left. He "applied moderate right rudder to compensate", then he applied "heavy" right rudder, but he was unable to arrest the veer. The airplane ground looped to the left, the right main landing gear collapsed, and the right wing impacted the ground.

The airplane sustained substantial damage to the right wing.

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

The Federal Aviation Administration has published the Airplane Flying Handbook FAA-H-8083-3A (2004). This handbook discusses porpoising and states in part:

In a bounced landing that is improperly recovered, the airplane comes in nose first setting off a series of motions that imitate the jumps and dives of a porpoise—hence the name. The problem is improper airplane attitude at touchdown, sometimes caused by inattention, not knowing where the ground is, mistrimming or forcing the airplane onto the runway.

Ground effect decreases elevator control effectiveness and increases the effort required to raise the nose. Not enough elevator or stabilator trim can result in a nose low contact with the runway and a porpoise develops.

Porpoising can also be caused by improper airspeed control. Usually, if an approach is too fast, the airplane floats and the pilot tries to force it on the runway when the airplane still wants to fly. A gust of wind, a bump in the runway, or even a slight tug on the control wheel will send the air plane aloft again.

The corrective action for a porpoise is the same as for a bounce and similarly depends on its severity. When it is very slight and there is no extreme change in the airplane's pitch attitude, a follow-up landing may be executed by applying sufficient power to cushion the subsequent touchdown, and smoothly adjusting the pitch to the proper touchdown attitude.

Text from the NTSB. Open the NTSB docket for GAA16CA443 for the full record.