FedEx Express Flight Operations and FedEx Engineering

Comment: FedEx Express Flight Operations and FedEx Engineering agree that increasing flameout margin to buffer against possible core shedding of ice crystal accretion is an important requirement, but strongly feel that part of the proposed addition to the AFM Limitation requirements is of limited value, and may not be justifiable. The proposed requirement for selection of Wing Anti-Ice would result in a small or incremental increase in core temperature while increasing fuel flow and unnecessarily exposing the aircraft to additional reliability risks. While activation of the ENG IGN OVRD switch and the engine anti-ice system is fully supported and believed to be an effective means of reducing flameouts, the activation of the wing and tail anti-system is not believed to be nearly as effective. FedEx notes that in the NTSB’s comments for this NPRM posted May 21, 2008, no mention is made of the wing and tail anti-ice systems being part of the successful recommendations on the Beechjet 400A aircraft. FedEx requests that additional justification be made available to support this portion of the recommendation due to the concerns that will be detailed further below. Justifications: Effectiveness vs. costs: FedEx believes that the total cost of this proposed rule has either not been fully considered, or not been properly communicated. The NPRM suggests an estimated fleet cost of $5,600 based on the labor required to make the AFM change. What has not been factored in however is that the selection of Wing and Tail Anti-Ice – while providing only a small incremental increase in core temperature of the engine - increases fuel burn and exposes the aircraft to additional aircraft reliability risks associated with increased use of this system. Per correspondence with Boeing, the increased fuel consumption due to Wing and Tail Anti-Ice is estimated to be 40 pounds for a descent from FL 400 to landing. Operation of the Wing and Tail Anti-ice relies on sensors, involves mechanical movement of switches and valves, and puts thermal and pressure loads on manifolds. Additional operations of these systems expose the aircraft system as a whole to additional reliability risks and an increased possibility of operational disruptions. Historical Data: GE has documented 6 flameout flight events suspected due to ice crystal accretion. GE Service Bulletin 73-21-07 ENGINE FUEL AND CONTROL - Electronic Control Unit Introduction of Software Version 8.3.K (8322) was introduced to improve flameout margin in ice crystal conditions. This change will create new engine control configurations with enhanced VBVs scheduling logic for inclement weather. The proposed software V 8.3.K will change the scheduling of the VBVs at high altitude to increase ice extraction from the booster-core flowpath transition to the fan exit stream and improve combustor flameout margin. This software improvement is currently required to comply with Docket No. FAA- 2007-28319; Directorate Identifier 2007-NE-27-AD; Amendment 39-15243; AD 2007-22-07. Incorporation in accordance with GE Service Bulletin is required at next shop visit, overhaul, or within 60 months. As required, FedEx is upgrading to this ECU software version. To our knowledge, there have been no suspected flameout events using the combination of Engine Anti-Ice and ECU Software Version 8.3.K on the MD-11 aircraft. Alternate Proposal: As a potential alternative, FedEx Express would like to recommend that the proposed rule allow for different AFM requirements based on the FADEC Electronic Control Unit (ECU) installed software version. In plain terms: a.) If the aircraft is installed with ECU Software Version 8.3.J or previous, follow the AFM Limitations requirements as noted in proposed rule. b.) If the aircraft is installed with ECU Software Version 8.3.K or subsequent, allow for the following AFM Limitation requirements: ‘‘With ECU software version 8.3.K or subsequent: Prior to reducing thrust for descent in visible moisture when TAT is 6 °C and below, the ENG IGN OVRD switch and the ENG ANTI-ICE switches must be placed in the ON position.’’ Combination of procedural requirements and software: FedEx’s proposal combines the actions of Engine Anti-Ice-ON and IGN-OVRD with the benefits of the ECU version 8.3.K software upgrade. This proposed requirement accomplishes the intent of increasing core temperature both procedurally and separately via the ECU software. Supporting Documentation: Reference a.) Docket No. FAA-2007-28319; Directorate Identifier 2007-NE-27-AD; Amendment 39-15243; AD 2007-22-07 Reference b.) GE Service Bulletin 73-21-07 ENGINE FUEL AND CONTROL - Electronic Control Unit Introduction of Software Version 8.3.K (8322) Reference c.) Data sheets provided by Boeing regarding the history and event data points for the flameouts suspected due to ice crystal accretion. These reports were provided to FedEx Express by Boeing, and may be proprietary. Reference d.) Estimates of increased fuel flow for Wing and Tail Anti-Ice descents. For additional comments regarding this NPRM comment, please contact: John McCormick MD-11/MD-10 Fleet Tech Pilot FedEx Flight Standards and Technical Support (901) 224-5353 jtmccormickiii@fedex.com Scott Rollen Project Engineer Powerplant Engineering Air Operations Office Tel: (901) 224-3843 Office Fax: (901) 224-3620 scott.rollen@fedex.com