CHI99LA002

The pilot reported that the aircraft porpoised during landing on Runway 13 at Sheboygan County Memorial Airport, Sheboygan, Wisconsin. He added that he was too fast on short final and focused on trying to flare and land without first stabilizing speed. He further stated that this resulted in inadvertent failure to trim nose up to landing attitude. The pilot reported that the landing started with a normal attitude, bounced, and then began to porpoise. The pilot stated that he did not know how to respond.

On October 4, 1998, at 1100 central daylight time, a Cessna 336, N3884U, owned and piloted by a private pilot, received substantial damage on impact with terrain during landing and overrun on Runway 13 (3,993 feet by 75 feet, asphalt/dry) at Sheboygan County Memorial Airport (SBM), Sheboygan, Wisconsin. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The pilot reported no injuries. The flight originated at Hunington Municipal Airport, Hunington, Indiana, at 0840, and was en route to SBM.

In a written statement, the pilot reported the following, "...At SBM entered downwind for Runway 13. Wind was from 100 at 15 kts. Wx clear and dry. Due failure to compensate for the wind in the pattern, turn to final overshot centerline and I used up half of final getting lined up. Maintained 120 mph while turning back to centerline (normal approach is 100mph). Too fast on short final I extended full flaps (from 1/3) and focused on trying to flare and land without first stabilizing speed. This resulted in inadvertent failure to trim nose up to landing attitude. Landing started with normal attitude bounces ... stretched somewhat by excess speed. About when I expected it to stay down (presumably due to the failure to trim nose up) it instead began to porpoise. I didn't know how to respond to that (is there a gap in the training and safety literature regarding proposing? I can't recall ever seeing how to deal with it discussed or a warning that it gets worse rather than better if ignored). I did not respond to 2 small porpoise bounces, which were followed rapidly by a larger one, ... a catastrophic one which wiped out the nose gear and caused both front and rear props to strike the ground. I used a final, level attitude bounce to turn into the grass and the plane came to rest softly and quickly in the long matted grass. I received not so much as a bump. The aircraft was substantially damaged in lower front area."

Advisory Circular 61-21A, Flight Training Handbook, under Bouncing During Touchdown, states, "When the airplane contacts the ground with a sharp impact as the result of an improper attitude or an improper attitude or an excessive sink rate, it tends to "bounce" back into the air. ... The severity of the "bounce" depends on the airspeed at the moment of contact and the degree to which the angle of attack or pitch attitude was increased. ... When a bounce is severe, the safest procedure is to EXECUTE A GO-AROUND IMMEDIATELY. No attempt to salvage the landing should be made. ... The go-around procedure should be continued even though the airplane may descend and another bounce may be encountered."