Overweight, unstable airplane crashes

Aircraft: Hummel Bird. Injuries: 1 Fatal. Location: DeFuniak Springs, Fla. Aircraft damage: Destroyed.

What reportedly happened: A review of the pilot’s logbook indicated that he had accumulated only 4.4 flight hours in the two years preceding the accident flight, with only 0.3 hour in the accident airplane.

According to witnesses at the airport, the airplane took off and began porpoising. When it was about 300 feet AGL, it pitched up to a nose-high attitude and rolled to the right, stalled and crashed.

The post-accident examination did not reveal any preimpact mechanical malfunctions or abnormalities, but it was determined the weight of the airplane exceeded the maximum gross takeoff weight and the center of gravity was aft of the most rearward limit.

The pilot had reported to his aviation medical examiner that the airplane was having “great” difficulty with longitudinal stability. He also noted that his weight gain caused the airplane to be “over gross,” most likely causing the control problems. The AME advised the pilot to stop flying the airplane.

Because the airplane was at or aft of the rear CG limit, it would have been very sensitive in pitch control and may even have been at or near a dynamically unstable flight regime in terms of pitch handling. Accordingly, the airplane would have required more nose-down trim adjustment.

Additionally, because stall speeds increase as gross weight increases, the airplane would have stalled at a higher airspeed.

Investigators determined it is likely that during the climb the airplane stalled at a higher airspeed than the pilot expected and that it subsequently entered a spin.

It was likely that the pilot’s lack of experience in the airplane contributed to his decision to take off with the airplane in an overweight condition and his inability to understand the seriousness of the situation.

Probable cause: The pilot’s failure to maintain control due to the airplane’s exceedence of its maximum gross weight and center of gravity’s most rearward limit and his lack of familiarity with the airplane make and model, which resulted in an aerodynamic stall and subsequent spin. Contributing to the accident was the pilot’s decision to knowingly operate the airplane over the maximum allowable gross weight with reduced longitudinal stability.

NTSB Identification: ERA12FA326

This May 2012 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.