FedEx Express Avionics Engineering

FedEx supports regulatory changes that improve safety. We also appreciate the opportunity to comment on the proposed AD. The FAA states in their comments that the original compliance time of 48 months has been reduced to 36 months. We believe 36 months is too short a period of time to modify the TCAS processors on a large mixed fleet of aircraft like FedEx's. The proposed AD requires modification of the software in every TCAS processor across 5 different fleets of aircraft. Installation of the new software changes the part number of the TCAS processors. Installation of the new TCAS part numbers is an FAA Major Alteration in every case. The current TCAS processor installations on these fleets are approved by 3rd party Supplemental Type Certifications (STCs that FedEx does not hold). FedEx will have to either obtain STC approval for the new installations or hire a 3rd party to develop the certifications before any TCAS processor upgrades can take place. If the certification work has to be outsourced there are bid solicitations and business negotiations that must occur before any work can begin. It generally takes about 6 months to get an agreement negotiated and signed. Regardless of who develops the STC, the development of an STC to certify a new TCAS processor on a commercial aircraft can take as long as 12 months. Development of a simple modification program for 5 fleets of aircraft requires at least 3 months of engineering and planning work. Aircraft modifications are typically scheduled to coincide with C Checks (a time when the aircraft is already out of service for scheduled maintenance). The longest C Check cycle in the FedEx fleet is 910 days (approx. 30 months).