FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION: DATA BUS NETWORK FOR AIRCRAFT
2. APPLICANT(S)
(a) NAME: Aircraft Upgrade Research & Design Centre,
Hindustan Aeronautics Limited, Nasik Division,
(b) NATIONALITY: INDIAN
(c) ADDRESS: Design Avionics(DEA),
Aircraft Upgrade Research & Design Centre, Hindustan Aeronautics Limited, Nasik Division, Ojhar Township Post Office, Ojhar(MiG), Nasik-422207 (Maharashtra) India
3. PREAMBLE TO THE DESCRIPTION
COMPLETE The follwing specification describes the
invention and the manner in which it is to be performed.
4. DESCRIPTION (Description shall start from next page.) - Refer Annexure-I
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble—"We Claim" on separate page.) Refer Annexure-ll
6. DATE AND SIGNATURE (to be given at the end of last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on separate page) Enclosed
Note: - * Repeat boxes in case of more than one entry.
*To be signed by the applicant(s) or by authorized registered patent agent otherwise where mentioned.
* Name of the inventor and applicant should be given in full, family name in the
beginning.
*Complete address of the inventor and applicant should be given stating the postal
index no./code, state and country.
*Strike out the column which is/are not applicable.

FIELD OF INVENTION
The invention relates to a design and development of MIL-1553B Data Bus Network for integration of state of art airborne avionics systems/sensors for aircraft.
BACKGROUND OF THE INVENTION
Most of the aircraft are basically of old design. All the avionics systems {Central Computer, Air Data system, Radar, Inertial Navigation system, Head Up display, Cockpit control Panels, Head down display and store management, other sensors and flight safety system) are contemporary to that period. The present avionics complex on aircraft (systems/sensors) does not meet the present day operational requirements. Major drawbacks of these old aircraft are poor Navigation accuracies, poor man machine interface, limited scope for modification/upgrade, long maintenance and readiness time, non availability of spares due to obsolescence, etc.
To bridge the technology gap between latest modern technology development and existing operational capabilities of the aircraft, midlife avionics upgrade of aircraft is required to improve the navigation performance by incorporating flexible data bus network, introduction of new airborne avionics systems/sensors and smart display in cockpit provides better Navigation accuracies and improved Man machine interface (MMI) with less maintenance and flight readiness time.
During upgradation of Navigation complex on aircraft, to match with current scenario's, integration of new state of art avionics systems as is on aircraft is not possible due to incompatibility of interface issues (like interface types, computational speed, data exchange format and rate). To overcome this interface issue, introduction of new MIL-1553B Data Bus network provides the common interface platform for exchange of data information for new avionics system/sensors.
MIL-1553B Data Bus network has been designed and developed for integration of new avionics/sensors and to meet the operation requirements of aircraft. The data bus network on aircraft provides flexible data bus platform with highly reliable and high speed data transmission for computation in Mission Computer on aircraft, by reducing wires bundles in turn saving weight and space, improving maintenance on aircraft. The

data bus network enables the flexible growth potential for modification and upgradation in future just by modifying the software on aircraft.
SUMMARY OF THE INVENTION
An object of the invention is to provide an flexible MIL-1553B Data Bus Network system for integration of latest airborne avionics system/sensors for improved performance by sensor data fusion on aircraft.
The invention provides plurality in 1553 Data Bus network system having main (Primary) and standby (redundant) network improving data reliability.
In one embodiment, Integration of new state of art avionics systems/sensors with the MIL-1553B data bus network is a flexible system architecture using MIL Bus components comprising of two or appropriate single/ dual port data bus couplers connected by twisted shielded Data Bus Cable and compatible MIL Bus connectors with bus load of characteristics impedance terminated at both the ends of data bus network. This Data Bus network also integrate the non MIL-1553 compatible system in integrated mode within the Navigation complex, providing highly reliable data transmission, with weight reduction, increased Space and reduction in aircraft wiring and maintenance activities on the aircraft. The methodology for fabrication of Mil Bus Segments as per the designed layout was carried out. A testing procedure and technology is devised'for testing of Mil Bus Segments (Generation of technology for termination of MIL bus Connectors and testing procedure), implementation of 1553B Data bus network (Figure 3) on aircraft with MIL Bus components (as per Table 1) and MIL bus Segments (as shown in figure 3, 4, 5 and 6).
The invention provides retrofitting an existence 1553 Data Bus network system for increases error free data transfer capacity, without rewiring and rework and with minimal impact to extant 1553 data bus network by modifying the software.

OBJECT OF THE INVENTION
a. To improve accuracy of Navigation complex by integration of new
systems/sensors and devise a flexible avionics system architecture through
introduction of 1553 B data bus network on aircraft.
b. To provide error free, high integrity data transmission with high reliability.
c. To provide reduction in the space, weight and numbers of wire bundles.
d. To provide Data bus network with battle damage resistance resulting in saving of
life cycle cost.
e. To provide low impact for modification and increase growth potential for
integration of advance avionics systems on aircraft in future.
f. To reduce the maintenance and flight readiness time of aircraft.
BRIEF DESCRIPTION OF THE DESIGN DRAWINGS (REFER APPENDIX-1)
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the following design drawings, wherein like parts are referred by the numerals wherein:
Figure 1- Indicates the typical existing architecture of aircraft before upgradation.
Figure 2- Shows details of flexible Avionics Upgrade Architecture-MIL-1553B Data Bus Network
Figure 3 - Shows details of MIL-1553B Data Bus Network layout for BUS 1-Main
Figure 4 - Shows details of MIL-1553B Data Bus Network layout for BUS1-Standby
Figure 5 - Shows details of MIL-1553B Data Bus Network layout for BUS2-Main
Figure 6 - Shows details of MIL-1553B Data Bus Network layout for BUS2-Standby

DETAILED DESCRIPTION OF THE INVENTION
As the aircraft is of old design, the present avionics architecture is built around the Central Computer (1) within the existing Navigation complex. The typical avionics architecture before upgradation is as shown in Figure 1.
As per the Figure-1, the Central Computer (1) required large number of input/output wires for connecting multifaceted transducer/sensors/systems (4). The data information is provided from the connecting avionics system to Central Computer (1), in the form of electrical voltages, discrete signals, event signals and Doppler frequencies (2 & 3), which is further converted into binary code (engineering value) by Central Computer (1) and used for computation to solve the necessary logic and algorithms. Results of the computations inside the central computer (1) are converted into appropriate signals required for operation of the Navigation complex (4) on the aircraft. This type of system architecture is interdependent on the system connecting within the complex, and the system configuration is not achieved by individual system itself, but depends on the complex function. This avionics architecture has following disadvantages-
- Complex programming for readiness of aircraft
- High Readiness Time
- Large amount of wiring & connectors
- Low reliability
- Low maintainability
- Limited scope for improvement/upgrade
- Obsolescence

Design of Data Bus Network for Aircraft
The present Navigation complex (4) (as shown in Fig-1) of aircraft built around old Central Computer (1) with bulk number of wires (2) has been replaced by flexible avionics system architecture by introduction of MIL-1553B Data bus network.
The design of MIL-1553B Data Bus network is based on the following requirements.
a. Avionics system requirement (Specification, Interface Control Document (ICD)
b. System specification
c. Load analysis of Digital Data on the network for design phase
d. Feasibility study for installation and layout of avionics system on aircraft
e. Implementation of topology for interconnection between the avionics systems on
aircraft.
Fig-2 describes the design of data bus network with associated upgrade avionics equipments for the aircraft. Design of 1553B Data Bus Network operates on multi-level Bus (8) and (9) topology concepts with plural redundancy. In this Network all the MIL-1553B Compatible systems/sensors (7) of aircraft are interfaced through dedicated Data Bus Network called as MIL-1553BUS1 (8).
Two identical Mission computer i.e Mission Computer -1 (MC-1) (5) and backup Mission Computer-2 (MC-2) (6) are connected through MIL-1553B Data bus network (8) to other avionics subsystems (7) on aircraft.
The heart of the 1553B Data Bus Network is Mission Computer-1(5), which organizes and controls the message scheduling in addition to mission computations and generation of displays in the cockpit.
As per design of 1553B Data Bus network, Mission Computer -1 (5) and backup Mission Computer-2 (6) are connected through separate MlL-1553 B Data Bus network called MIL-1553B BUS2 (9). This Data Bus Network is used for transfer of system data between the Mission Computers to work in hot standby mode on aircraft.

Provision for testing for MIL-1553B Data Bus network were provided on aircraft through individual test connectors for each data bus network. The test connectors are used for checking the serviceability of data bus network as a part of maintenance aspect and verifying the Interface Control Document of new avionics system integrated on aircraft and can be used for monitoring and analyzing the data exchange and bus traffic .
Furthermore, a communication method over 1553 Data Bus Network system is provided. The method comprises the steps of transmitting 1553 signals in digital form on a main and on the standby bus according to a 1553 bus fault design and receiving 1553 signal from main and standby buses. The method further comprises the step of transmitting non compatible 1553 signal from non compatible 1553 system connected within the complex through 1553 compatible system over main and standby bus and step of selecting a non 1553 receive path between either the main and standby bus an a non 1553 receiver. The method also comprises the step of receiving non 1553 signals on the selected receive path. The receive path selection is based on predefined receive signal path selection design criteria.
Finalization of MIL-1553 B Components for Data Bus Network
Based on the requirement of data bus network, following Mil Bus Components are used to build Data Bus Network to upgrade aircraft;
Table-1

SI.No. Mil Bus Components
1. Twisted shielded Data Bus Cable
2. Type of Data Bus Coupler
- Single stub box coupler
- Dual stub box coupler
- Four stub box coupler
3. MIL Bus Connectors
- Connector
- Bulkhead Cable Jack
- Bulkhead Connector
4. Dust Cap
5. 78 Ohm load
6. 3K Ohm Terminator

Integration of MIL-1553B Data Bus Network on Aircraft
As per the requirement of Data Bus network all the types of data bus coupler as mentioned at SI. No. 2 of Table-1 were installed on the aircraft. Accordingly all MIL Bus segment has been laid on the aircraft as per the MIL Bus layout design drawing and independent data Bus network (Main and standby) has been formed by connecting data bus couplers with the help of MIL bus Segments as per Fig.3 to 6. Each independent data Bus network has independent standby network in case of failure of main network. All independent Data Bus network are terminated by characteristic impedance at the end of network. Installation of hermetically sealed bulkhead connectors were provided on aircraft to bring the MIL Bus segment inside the cockpit for new MIL compatible avionics system/ smart displays.
Test carried out after modification
As per the design of data bus network layout (Figure -3,4,5 and 6) , MIL Bus segment design drawing along with Bill of Material (BOM) for fabrication/manufacturing of MIL Bus segment is prepared and approved by Govt, agency. As per the approved Mil Bus Segment design drawings, all the MIL Bus segments required for MIL-1553B Data Bus network has been manufactured as per the new technology and tested according to test schedule (Physical Inspection and further Continuity, Inter shorting and Megger Test) and is also certified by Govt, agency for its airworthiness. Based on the results, these segments are cleared for installation on aircraft. The network is implemented on aircraft as per data bus network layout diagram (shown in figure 3,4,5 and 6) just by connecting the number of MIL Bus Segments to new airborne avionic systems/sensors through different types of Data bus coupler and all the data bus couplers are also interconnected with the help of MIL Bus Segments. Both ends of the data bus network terminated by load of characteristics impedance of network as per MIL-STD-1553B and Bulkhead connectors used for passing the MIL Bus Segment into cockpit for connecting avionics system/control panel inside the cockpit. .
After implementation of MIL-1553B Data Bus network on aircraft same has been tested by using Acceptance ground test procedure duly approved by Govt, agency and found satisfactory. After successful completion of ground test network has been tested with actual equipment (Power ON condition) on aircraft and found satisfactory.

What is claimed is:
1. In one embodiment, Integration of new state of art avionics systems/sensors with the MIL-1553B data bus network provides flexible system architecture of MIL Bus components, comprising of at least two single port data bus coupler connected with the help of twisted shielded Data Bus Cable and compatible MIL Bus connector with at least two bus load of characteristics impedance terminated at both the ends of data bus network; Within a 1553 Data Bus Network system compromise of main data bus , standby data bus, Mission computers and avionics systems/sensors and non compatible system; This Data Bus network also integrate the non MlL-1553 compatible system in integrated mode within the Navigation complex, providing highly reliable data transmission, with weight reduction, increased Space and reduction in aircraft wiring and maintenance activities on aircraft; The MIL-1553B Data Bus networks enables .the growth potential for modification in future through software modification.
2. The Data Bus Network system of claim 1, wherein the data transfer communication system comprises a plurality of avionics systems/sensors functioning as remote terminal communicating with Mission computer functioning as Bus Controller over two main (primary) and standby (redundant) data bus.
3. The data bus Network system of claim 1, wherein the system data transfer is established through dedicated data bus network, which reduced the data load on the operational data bus and provides the scope and reversed data capacity for future growth in the Data Bus network.
4. The Data Bus Network system of claim 1, wherein the 1553 data interface and communication is according to Notice 2 of MIL-STD-1553B communication standard.
5. The Data Bus Network system of claim 1, wherein said Data Bus network supports bandwidth configurability according to MIL-1553B channel conditions of the network.

6. The system of claim 1, wherein methodology of testing (Certification) of 1553B Data Bus network on aircraft and further testing of 1553B Network as part of Schedule Maintenance activities