Diamond Aircraft Ind Inc DA 20-C1 N409AM incident near Bloomington, Illinois

Probable cause

The cracked nose landing gear fork assembly found during the preflight inspection.

NTSB analysis

A student pilot found a cracked nose landing gear (NLG) fork, which was the third cracked fork the operator reported in the previous 17 months. A Federal Aviation Administration (FAA) Service Difficulty Report (SDR) query revealed there were 12 SDR reports on the NLG forks, which included the three from the incident operator. Another operator had a fleet of 44 airplanes. This fleet’s airplanes accumulated 13 cracked NLG forks in 17 months. According to a fleet representative, their normal procedure for reporting failed parts was to submit the information directly to the manufacturer, instead of submitting a SDR. The airplane’s manufacturer recommended the installation of screws in the bolt holes used to secure the fairing to the NLG fork, which reportedly reduced a stress concentration point. The airplane manufacturer published a Service Information Letter (SIL), which depicted a replacement NLG fork assembly, and described the installation process. The SIL also referred owners to the maintenance manual for new inspection requirements that require the NLG to be inspected every 100 hours as opposed to the previous 6,000-hour inspection cycle. The National Transportation Safety Board issued recommendations to the FAA to encourage "all persons or organizations that operate under 14 CFR Parts 43 and 91 to submit Malfunction or Defect Reports ... and to ... encourage foreign regulatory agencies to provide service difficulty data from resident operators and manufacturers to the FAA for incorporation into the FAA service difficulty data base."

Text from the NTSB. Open the NTSB docket for CEN10IA554 for the full record.