DESCRIPTION TECHNICAL FIELD

This invention describes an optimized process for loom fabrication to reduce the aircraft cycle time in LCA-TEJAS aircraft. Presently of the total 1,147 connectors on aircraft, 866 connectors are being finalized on the bench/wing/pylon. The remaining 281 connectors are finalized on the aircraft. The time required for finalization of these connectors on aircraft is 3 months.

BACKGROUND OF INVENTION

Tejas is a state-of-the-art aircraft with high-end avionics, rugged and reliable general systems, all rolled into one small aircraft. It is equipped with quadruplex fly-by-wire Flight Control system and Digital Avionics & weapon system with redundant MIL 1553B BUS for data acquisition and display of aircraft data in the cockpit along with sensor and stores information.

The electrical wiring integrates all the mechanical systems, avionics systems and weapon systems on the aircraft. The electrical system provided for the aircraft is highly reliable and robust from the point of view of EMI/EMC issues. The electrical system architecture provides power from multiple sources and also systems are segregated as far as possible, so as to avoid any common point failure. In LCA, unlike in other metal aircraft two-wire scheme is followed for grounding i.e., for the return currents, structure is not used as return path but a separate cable is routed. This is because of two reasons- first being the use of composites on LCA and the second to avoid ground loops and signal interference due to undesirable EMI/EMC effects of using structure as return path. LCA being avionics intensive aircraft, this scheme is desirable for better avionics performance even at the cost of doubling the electrical wiring on the aircraft. As such, electrical system on LCA has several redundancies built into the design, making it highly complex and reliable but also dense.

In Tejas aircraft there are 399 looms which comprises of 1147 connectors. In addition there are Terminal Lugs and Junction Modules/Splice Terminations. All the above put together consists of 11,373 electrical interconnections on the aircraft with 22,476 terminations.

The 399 loom drawings are broadly classified as follows:

1. Vendor looms: 57

2. Wing looms: 46

3. Pylon looms: 42

4. No. of looms integrated on loom boards: 54

5. Pigtail looms: 24

24 pigtail looms consists of 24 connectors. Out of these 24 connectors, 16 connectors are completed in loom shop and balance 8 connectors are done on aircraft.

6. Antenna looms: 15

These 15 antenna looms consists of 30 connectors. Out of this, 21 are completely finalized in loom shop and the balance 9 connectors are finalized on aircraft.

7. Power looms: 24

These 24 power looms contributes for 19 connectors/terminations. Out of this, 6 connectors/terminations are completely finalized in loom shop and balance 13 are finalized on aircraft. 8.1:1 looms (end to end): 36

These 36 looms consists of 54 connectors. Out of this 54 connectors, 50 are completed in loom shop and balance 4 are done on aircraft. 9.1: many looms: 101 .

These are the complex looms in LCA-Tejas aircraft. These 101 looms give way to 307 connectors connecting multiple LRUs located at different locations. Only 80 of these connectors are finalized in loom shop and balance 227 are finalized on aircraft.
In addition to connectors, 93 junction modules and 125 miscellaneous electrical terminations are carried out on the aircraft.
Note: S.No. 1 to 4 doesn't involve finalization of any connectors on the aircraft.
LCA is now into the series production schedule. In order to reduce the production cycle time of aircraft, it is required to reduce the time required for looming on the aircraft. Of the total 1147 connectors, 281 connectors are presently being finalized on the aircraft, which accounts for 24.5% of total connectors on aircraft. Hence effort is made to reduce this number so that aircraft cycle time for looming is reduced. This optimized process will yield reduction in aircraft built time.

SUMMARY OF INVENTION

CONCEPT EVOLUTION IN DETAIL

Out of the total 1147 connectors in LCA-Tejas aircraft, 866 connectors are finalized on the bench/ loom board/ pylon/wing. This does not account for the aircraft equipping cycle time. The remaining 281 connectors, are finalized on the aircraft. A new scheme is introduced to finalise additional 73 connectors, 34 Terminal Lugs, 3 Junction Modules and 42 miscellaneous terminations by integrating looms/connectors on bench in loom shop.

1. Pigtail Looms: Out of the 8 pigtail connectors finalized on aircraft, it is advised to finalise 4 of them on bench, since these pigtails belong to relatively smaller LRUs.

2. Antenna looms: 9 connectors of antenna looms are finalized on aircraft. They were not finalized in loom shop due to non availability of exact routing path. Antenna cable can neither be short nor long, it needs to be exact. Hence after determining the exact length from optimum routing path now 7 connectors will be finalized on bench in loom shop. The connector during routing is to be properly wrapped and then routed to avoid damage to adjacent cables.

3. Power Looms: Similar to antenna looms, length of power looms is vital.. Since they are very thick securing of these cables is difficult. Out of 19 connectors only 6 are completely finalized in loom shop and 13 connectors/20 looms are finalized on aircraft. Optimum routing path is identified and so the exact length, now 1 connector/10 looms will be finalized on bench in loom shop. The connector/lugs which are to be routed are to be properly wrapped and then routed to avoid damage to adjacent cables.

4. For 1:1 looms, maximum no. of connectors are already integrated on bench. Now one junction module is suggested to be integrated with existing loom in loom shop.

5. Looms with multiple connectors : These looms are complex in nature involving many connectors. Cables are routed between multiple LRUs located in different zones of the aircraft. A scheme is developed to finalise a few of these connectors with the existing design and structure {routing cutouts).

Every connector in this category is studied for its size and its location on the aircraft so that it can be integrated with the primary connectors of the loom shop. In this way 2 junction modules and 60 connectors are identified to be integrated and finalized in loom shop on bench.

In addition to the above proposed connectors, 21miscellaneous items are also identified to be completed on loom boards. By finalizing all the recommended connectors/junction modules in loom shop, 660 hours of aircraft equipping lead time is reduced.

CLAIMS

1. We claim that this process will optimize the loom fabrication in LCA-Tejas aircraft.