Event Summary
A private pilot with 156 hours of flight experience was conducting a night flight. According to the pilot's statement, the airplane's airspeed was allowed to decrease while flaring too high, resulting in a hard landing. Upon impact with the runway, the upper portion of the firewall separated from the airframe, causing the engine to drop downward approximately 30 degrees.
Inspection Findings
A post-accident inspection revealed two significant structural failures. The upper left engine support-mount had cracked at the bracket bolt hole, and the upper right engine attachment rivets had separated from the airframe stringer assembly. These failures allowed the engine to shift downward after the hard landing.
Metallurgical Examination
The upper engine mount brackets were removed from the airplane and sent to the NTSB Materials Laboratory for examination. The examination revealed that the brackets fractured due to fatigue. Additionally, the metal content of the brackets did not contain the constituent elements of the specified material and was approximately 40 percent below the specified strength. No other contributing factors were identified in the source material.