.

2) Field of invention
It is a mechanical engineering design which comes into deployment during operation of door locking mechanism, which is installed on fixed structure of the aircraft.
3) Use of invention
This invention finds application in the Door Locking Mechanism of aircrafts.
4) Prior art
the door locking mechanism consists of locking levers installed on fixed structure and locking plates fixed on movable doors. Previously, in door opened condition these locking levers were projecting outside the fixed structure causing inconvenience during ingress/egress. Also, closing of the door without operating the door handle used to damage the locking plates fixed on the door. Hence a mechanism was required to hold these locking levers in closed position to avoid projection when door is opened without affecting jettison/emergency exit of the door.
5) Draw backs of prior art
There are few shortcomings in the earlier design which is mentioned below:
• Locking levers were projecting outside the fixed structure casing inconvenience during ingress/egress.
• Damage to the locking plates fixed on the door.
6) Comparison between prior art and present invention
Previously, in door opened condition the locking levers were projecting outside the fixed structure causing inconvenience during ingress/egress. In present scheme, a mechanism was derived to hold these locking levers in closed position and avoid the projections when door is opened without affecting jettison/emergency exit of the door.
7) Aim of the invention
Helicopter includes Pilot/Co-pilot doors which are ergonomically designed for easy ingress/egress into the cockpit at normal/emergency situations. These doors are hinged and made integral with fixed structure by means of door locking mechanism. Electrical indicators are provided in the cockpit, to know whether the door is open or closed. The prime objective of the invention is to avoid the projections in egress/ingress area by holding the locking levers in closed position when the door is opened.

8) Detailed description of invention
The door locking mechanism with multiple latches and multiple load paths are provided to prevent opening of door in flight due to mechanical failure. The door may be closed from outside or inside. The door locking mechanism consists of locking lever installed on fixed structure and locking plates fixed on movable doors. In door opened condition these locking levers were projecting outside the fixed structure causing inconvenience during ingress/egress as shown in figure 1. Hence a mechanism was derived to hold these locking levers in closed position to avoid projection when door is opened without affecting jettison/emergency exit of the door.
The catch assembly is a spring loaded mechanism which holds the locking levers in closed position when the door is opened as shown in figure 2. Once the catch assembly gets activated the locking levers at all places will be held in closed position avoiding the projection in egress/ingress area. When the door is closed the catch assembly remains ineffective. Hence the catch assembly avoids the locking lever projection.
9) Brief description of drawings
The Figurel illustrates the schematic view of door locking mechanism and also explains the difference between pre-mod and post-mod. Pre-mod is the previous design while post-mod is the new modified design. The Figure 2 illustrates the detail concept of catch-assembly.
10) Statement of invention
The present invention of catch-assembly holds the locking levers in closed position avoiding the projection in egress/ingress area. Also, damage to the locking plates fixed on the door is avoided. Hence the reliability of the system is enhanced when compared to the previous design.

Claims
We claim that,
1. The design concept of catch assembly is a spring loaded mechanism which holds the locking levers in closed position when the door is opened as shown in figure 2. Once the catch assembly gets activated the locking levers at all places will be held in closed position avoiding the projection in egress/ingress area. When the door is closed the catch assembly remains idle without affecting jettison/emergency exit of the door.
2. Methodology adopted in using the concept of spring loaded catch assembly.