scope:

It is intended that this specification be used with the application and customer needs in mind. To enhance the breadth of use, the specification is set forth in three phases defined as follows:

a. Phase I - This phase specifies the definitions, guidances, and appraisals given in Section 1.1 for those instances in which the aircraft manufacturer intends to randomly mix ARINC 600 boxes and ARINC 404/404A boxes.

COMMENTARY

In some aircraft it may be that some ARINC 600 boxes will be interspersed with ARINC 404/404A boxes on one rack while others will be installed in a dedicated ARINC 600 Phase I rack/cabinet. The guiding principle followed in this specification is one-way generation (or phase) interchangeability. ARINC 600 Phase I boxes should meet qualification requirements and fit and perform satisfactorily when installed on a Phase 0 (ARINC 404/404A) rack. It is recognized that a portion of the ARINC 404/404A rack will have to be made to accommodate the ARINC 600 Phase I boxes due to different hold-downs, different connectors. This is not to imply that cooling air will be different. Air will continue to be drawn down in 404A Racks and Phase I LRUs will have to live with this condition. On the other hand, an ARINC 404/404A box could not be installed in an ARINC 600 Phase I rack/cabinet because it may be too large, it has front "dog houses," a cooling system (e.g., holes in the sides of the LRU) that would upset the cooling provided in an ARINC 600 Phase I Rack/Cabinet, and for other reasons. The user of this Specification may, therefore, always install a mix of boxes in the lower numbered phase rack/cabinet and only two phases will be mixed in one rack/cabinet.For purposes of this discussion, RINC404/404A is considered Phase 0 when considered along with ARINC 600 Phase I.

b. Phase II - This phase specifies the definitions, guidances, and appraisals given in Section 1.1 for those instances where ARINC 600 LRUs are of a design catering to mechanical, electrical, and environmental control that is substantially beyond those features for Phase I. Phase II, therefore, is another step in the evolutionary development of avionic installations. It is intended to enhance the operator's satisfaction with avionics built to and installed in accordance with Phase II specifications. This satisfaction is meant to encompass life cycle cost, reliability, maintainability, etc. As with Phase I and ARINC 404/404A, it is likely that aircraft manufacturers will find it necessary (convenient) to sometimes mix Phase II LRUs and Phase I LRUs in the new rack. When this is done, the installation criteria for Phase I will prevail. However, it will not be proper to install Phase II LRUs in ARINC 404/404A shelves since these shelves will not be able to meet certain Phase II requirements. The standard rule is, as stated above, always install a mix of LRU phases in the lower-numbered phase shelf/cabinet and no more than two phases may be mixed on one shelf. Put differently, a Phase N + 1 LRU can be used in (and only in) a Phase N or a Phase N+ 1 Rack/Cabinet. Similarly, a Phase N LRU can be used only in a Phase N or Phase N - 1 Rack/Cabinet.

COMMENTARY

The commentary set forth in (a) above generally applies here. It must be clearly understood that a Phase II box has not yet been fully defined and may not be expected to fit or survive in an ARINC 404/404A rack.

c. Phase III- This phase specifies the definitions, guidances, and appraisals given in Section 1.1 for those instances where ARINC 600 LRUs are of a design catering to improved mechanical, electrical, and environmental control that is substantially beyond those features for Phase II. The criteria for mixing Phase II and Phase III LRUs include the requirement that such a mix must always occur in a Phase III Rack/Cabinet only.

COMMENTARY

The commentaries under (a) and (b) generally apply here.

NIC Phase I Design Requirements are contained in Section 3 of this document. Phase II and Phase III Design Requirements will be provided as additional sections when they are developed and adopted by AEEC.