Embraer

Dear Sir: Please find below Embraer comments to NPRM Docket No. FAA-2008- 0194 dated May 07th, 2008. The NPRM would require airplanes with cycle totals above the thresholds to perform the required inspections within 90 days of the effective date of the AD. While 90 days is a reasonable deadline for the incorporation of changes to a maintenance program, to require the actual inspections to be completed within that time means that the affected airplanes will have to be removed from service for special inspections. Unlike as stated in the supplemental NPRM, the issue is not only the availability of replacement parts, but the necessity of requiring unscheduled, especially intrusive, inspections like these that require the fuel tanks to be safed (drained and ventilated) prior to inspection. The risk identified in the analysis done to develop this inspection program does not indicate such a rapid inspection is necessary, and in truth, requiring unscheduled tank penetrations will increase the probability of maintenance error which will result in an increase in the risk of ignition sources, which is exactly the problem this AD is trying to address. As stated in the preamble to the final rule: The fuel tank safety review may result in maintenance actions that are overdue prior to the effective date of the operational rules. The plan provided by the operator should include recommended timing of initial inspections or maintenance actions that are incorporated in the long term maintenance or inspection program. An analysis of and supporting evidence for the proposed timing of the initial action should be provided to the FAA. For example, it may be determined that an inspection of a certain component should be conducted after 50,000 flight hours. Some airplanes within the fleet may have accumulated over 50,000 flight hours. The timing of the initial inspection must be approved by the FAA and would be dependent upon an evaluation of the safety impact of the inspection. It is desirable to incorporate these inspections in the current heavy maintenance program, such as a "C" or "D" check, without taking airplanes out of service. However, it may be determined that more expeditious action is required, which may be mandated by AD. As stated previously, Embraer believes that there is no special risk identified that justifies such a rapid implementation of the inspection for airplanes that have exceeded the threshold. In lieu of the reference to the next “C” check, Embraer suggests within the next 5000 flight hours after the effective date of this AD. If FAA retains the 90 day inspection requirement for the over-the-threshold airplanes, the Cost of Compliance section should be revised to reflect the true cost of the unscheduled inspections. Embraer notes that, in the promulgation of SFAR88, FAA estimated the cost for the initial inspection as between 60 and 330 additional labor hours, with the subject airplane out of service for between 36 and 96 hours. Note that these values were determined for an inspection done concurrently with a C check, and that the cost of unscheduled inspections would be significantly higher.