Diamond Aircraft Ind Inc DA 40 N326AF incident near Colorado Springs, Colorado

Probable cause

Fatigue failure of the nose wheel fork, which resulted in separation of the nose wheel.

NTSB analysis

The flight instructor and student pilot were performing their fourth touch-and-go landing of the day when the student pilot bounced the airplane. The instructor determined that the bounce was not severe and allowed the student to remain on the controls for a second touchdown. As the airplane contacted the runway, the instructor observed the airplane’s nose wheel depart the airplane. The airplane skidded down the runway for about 120 feet on its main landing gear and nose wheel strut before coming to a stop. An examination of the nose landing gear determined that multiple fatigue cracks had originated in the forward machined pockets of the left and right sides of the nose wheel fork. The cracks propagated until the fork could no longer sustain the applied operational loads, at which point overload failure occurred. As a result of the investigation, the airplane manufacturer developed a reinforced nose wheel fork, and the operator conducted a one-time inspection of its fleet of airplanes to identify any other nose wheel forks with fatigue cracks. The operator also implemented a method to nondestructively inspect all their airplanes’ nose wheel forks for fatigue cracks on a periodic basis. Additionally, the operator evaluated and implemented ways to decrease low cycle, high intensity stress brought on by nose wheel shimmy during takeoffs and landings and published guidance outlining specific steps to take in the event of hard landings, bounces, nose wheel strikes, and excessive nose wheel shimmy or vibration.

Text from the NTSB. Open the NTSB docket for CEN11IA114 for the full record.