FORM 2 THE PATENTS ACT, 1970
(39 of 1970) & The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Device for Expansion Test of Perspex Canopy of Aircraft
2. APPLICANT(S)
(a) NAME: HINDUSTAN AERONAUTICS LIMITED
(b) NATIONALITY: INDIAN
(c) ADDRESS: SM (Lean & IPR officer) Aircraft Manufacturing Division, Nasik
3. PREAMBLE TO THE DESCRIPTION
COMPLETE The following specification
particularly describes the invention and
the manner in which is to be performed.
4. DESCRIPTION (Description shall start from next stage.) Refer Annexure I
5. CLAIMS (Not applicable for provisional specification. Claims should start with the preamble - "I/We claim" on separate page)
Refer Annexure II
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)
Refer Annexure III
Note:-
*Repeat boxes in case of more than one entry.
*To be signed by the applicant(s) or by authorized registered patent agent.
*Name of the applicant should be given in full, family name in the
beginning.
♦Complete address of the applicant should be given stating the postal index
no./code, state and country.
♦Strike out the column(s) which is/are not applicable.

1 Title of the Invention
Device for Expansion Test of Perspex Canopy of aircraft
2 Field of the Invention
The invention relates to mechanical and aerospace engineering in general and specifically to aircraft repair.
3 Background of the Invention
An aircraft Perspex canopy is a transparent enclosure over the cockpit, which serves the following purpose:
a) To provide weatherproof and reasonably quiet environment.
b) To provide normal field vision to the pilot in air as well as on ground,
c) To protect the pilot against the airflow.
d) To maintain cabin pressure.
e) To provide access to safe ejection in case of emergency.
The construction of aircraft Perspex canopy is of floating type. Aircraft Perspex canopy is having metallic frame and Perspex. This Perspex is secured on the canopy frame by glued joint. During scheduled maintenance activity, an expansion test of Perspex canopy is mandatory. During cabin pressurization, there is relative expansion of Perspex with respect to frame. An expansion check is performed on the aircraft Perspex canopy to ascertain the health of the glued joint.
In conventional test, an expansion check is performed on the aircraft Perspex canopy under pressurization and expansion of Perspex is marked with the help of graph papers. The strips of graph papers are pasted with masking tape on the Perspex and on the metallic frame. A horizontal reference line is marked on the strips with the steel ruler in non-pressurized condition. Cabin pressurization is carried out using air pressure at designated values and the difference in the alignment of horizontal reference lines is considered as the expansion of Perspex canopy. Graph paper method is tedious, flawed, time consuming, subjective and resource

intensive. The present invention directed to an innovative design of portable device to perform expansion test of Perspex canopy of the aircraft.
3.1 Prior Art
US patent US US2652996A: Aircraft cockpit canopy, describes a general design aspect of cockpit canopy. Though it is related to a cockpit canopy, it does not relate to the present invention either on the scope or on the functionality.
US patent US US2505651A: Safety lock for sliding aircraft cockpit canopies, describes a general design aspect of cockpit canopy and Safety lock. Though it is related to a cockpit canopy, it does not relate to the present invention either on the scope or on the functionality.
US patent US 2730777A: Canopy mounting, describes a general design aspect of cockpit canopy mounting and improved mounting edge arrangement for cockpit canopy. Though it is related to a cockpit canopy, it does not relate to the present invention either on the scope or on the functionality.
4 Brief Summary of the Invention
The construction of aircraft Perspex canopy is of floating type. Aircraft Perspex canopy is having metallic frame and Perspex. This Perspex is secured on the canopy frame by glued joint. During scheduled maintenance activity, expansion test of Perspex canopy is mandatory. In cabin pressurization, there is relative expansion of Perspex with respect to frame. An expansion check is performed on the aircraft Perspex canopy to ascertain the health of glued joint.
During expansion test of Perspex canopy at designated air pressure, there is vertical displacement of Perspex with respect to frame. A portable device of present invention is used to measure the vertical displacement of Perspex canopy of aircraft by non-destructive testing methodology. When

the vertical displacement of Perspex is beyond permissible limit, the health of glued joint is ascertained as weak and hence the Perspex canopy is considered unserviceable and requires repair. In present invention, device comprises of a metallic casing with vacuum suction cups and measuring device along with the horizontal plunger. The device is stuck on the Perspex canopy surface and pointer is aligned on the metallic frame. During cabin pressurization, an expansion of Perspex canopy with respect to metallic frame is observed on the measuring device. The device offers the accurate and precise values of the expansion of canopy on the measuring device during cabin pressurization.
5 Detail Description of the Drawings
The invention can be better understood by reading the detail description of the disclosed embodiment followed by the accompanied drawings:
Figure 1: Schematic diagram of device for expansion test of Perspex canopy of aircraft.
Figure-2: Block diagram of device for expansion test of Perspex canopy of aircraft. Details of figure 1 &2 1: Device for expansion test 2: Suction cup 3: Measuring device 4: Locking knob 5: Casing
6: Extension plunger 7: Horizontal plunger 8: Plunger locking screw 9: Metal casing 10. Perspex canopy

6 Detail Description of the Invention
Present invention is a device to perform expansion test of Perspex canopy of aircraft.
A full understanding of the invention can be gained, when wherein parts are referred by the numerals read in conjunction with; Figure 1: Schematic diagram of device to perform expansion test of Perspex canopy of aircraft.
Figure-2: Block diagram of device to perform expansion test of Perspex canopy of aircraft.
Device for expansion test (1) is used for expansion test of Perspex canopy of aircraft. It consists of metal casing (5) fixed with suction cups (2). Suction cups (2) provide grip to the device for expansion test (1) on the Perspex canopy by the virtue of vacuum. A Metal casing (5) gives sturdiness to the device and acts as a housing, for measuring device (3) and suction cups (2). A measuring device (3) is fixed on metal casing (5) with locking knob (4). Locking knob (4) ensures the easy fitment and removal of a measuring device (3) for periodical servicing/calibration. Extension plunger (6) and horizontal plunger (7) are mounted on measuring device (3) and adjusted by plunger locking screw (8). The expansion of the Perspex canopy during cabin pressurization is sensed by the Horizontal plunger (7) and transmitted by Extension plunger (6) to the measuring device (3). Complete assembly is installed on Perspex canopy (10) with the help of suction cups (2). Horizontal plunger (7) is placed with point contact on metal frame (9).
Testing Procedure: Expansion test of Perspex canopy is performed to measure vertical displacement of Perspex with metal frame during cabin pressurization. The identified Perspex canopy is cleaned with the hygroscopic medicated cotton and lukewarm water to remove dirt/dust on Perspex. The Expansion test device is ensured for periodical servicing/calibration. The Suction cups (2) are cleaned with lukewarm water to remove dirt and dust The expansion test device is stuck on Perspex with

suction cups (2). Horizontal plunger (7) is placed with point contact on metal frame (9). Vertical alignment of Extension plunger (6) and horizontal alignment of Horizontal plunger (7) is ensured with steel ruler. Locking knob (4) and plunger locking screw (8) are tightened to fix the set up. A Device (1) is preloaded to 3 mm of scale to measure the vertical displacement of Perspex canopy. An expansion of Perspex canopy (10) with respect to metallic frame (9) is observed on the measuring device (1) during cabin pressurization. The vertical displacement of Perspex follows linear relationship with respect to cabin pressure. When the vertical displacement of Perspex is beyond permissible limit, the health of glued joint is ascertained as weak and hence the perspex canopy (10) is considered unserviceable and requires repair. The expansion test is performed at four places simultaneously on Perspex canopy to achieve repeatability and accuracy.

We Claim,
1. A device (1) for expansion test of Perspex canopy of aircraft
comprising:
A Metal casing (5) fixed with suction cups (2) for attachment of
device (1) on canopy surface;
A measuring device (3) to measure the Expansion of Perspex Canopy fixed on metal casing (5) with locking knob (4); An Extension plunger (6) with horizontal plunger (7) mounted on measuring device (3) adjusted by plunger locking screw (8) installed on Perspex canopy (10) for initial level adjustment; and A Horizontal plunger (7) with point contact on metal frame (9) of canopy.
2. The device (1) as claimed in Claim 1, fixed with suction cups (2)
installed on Perspex canopy (10) aerodynamic profile for precise test
results obtained during the expansion test