Name of the Applicant: Application No.:

Hindustan Aeronautics Limited, ACD.

Sheet No: 3 Total Sheets: 14

1. Title of the invention
Manufacturing process of Composite Spar assembly used in the Horizontal stabilizer for Choppers
2. Introduction
The composite spar assembly is a reinforcing member of Horizontal Stabilizer assembly, which is a fixed wing section, whose job is to provide stability for the aircraft, to keep it flying straight. The horizontal stabilizer prevents up-and-down, or pitching, motion of the aircraft nose. If the fuselage deviates from the desired pitch angle (set by pilots cyclic input), an angle of attack is created between the horizontal stabilizer and the airflow, thus creating lift. This lift acts in the opposite direction to the original displacement of the fuselage, thereby giving a moment to return the fuselage to its starting state.
3. Field of invention
The invention is a Manufacturing process of Composite Spar assembly using manual lay-up of fiber reinforced composite plies. It relates to the field of manufacturing light weight composites used in the Aerospace applications, this one, particularly used in light weight choppers. The ' I ' cross section component fabricated in single piece throughout the stabilizer length involves lay-up in stages with the use of split tool and an insert potting process post the curing of component.
4. Use of invention
The invention is a contemporary method of fabricating an I section spar with the use of advanced composite materials. This is a flawless method, which can be consistently applied for fabrication of composite spars and similar components.
5. Prior art
Patent US 5492579A is for composite utility pole which is round in cross section but is not closely related to the present invention.
6. Draw backs of prior art
The composite utility pole does not have foam hence bulky in nature.
7. Comparison between prior art and present invention

SLNO PRIOR PATENT PRESENT INVENTION
1 For the patent US 5492579 A there is no mention of foam For present invention foam is available
2 For the patent US 5492579 A it is round in cross section For present invention it is rectangle in Cross section


ATEMTT' Q(£p#V&E- CHENN.AI Signature of the mventors

Qa/12/2017

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Applicant

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Name of the Applicant: Hindustan Aeronautics Limited, ACD. Sheet No: 4
Application No.: Total Sheets: 14

8. Aim of the invention
The aim of the invention is to manufacture the Spar assembly used in Horizontal stabilizer in choppers. The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight
The aim of this invention is to develop an exceptional process to fabricate a high strength low weight advanced composite ' I' section spar, which is capable to support the top and bottom skins of the stabilizer and which has integrated inserts for fastening. The process
9. Summary of the present invention
The Spar assembly is a part used in Horizontal stabilizer in choppers fabricated with fiber reinforced composite materials like carbon, glass, carbon UD, Nomex core, Metallic inserts etc.by using split mould. The component is fabricated in two stages. In first stage the layup is done for top and bottom flanges by using glass and carbon UD and cured separately in autoclave. In second stage layup is done for LH and RH web and pre-compacted at 60 deg using vacuum and 1.5 to 2 bar pressure for 1 hr in autoclave. After Pre-compaction core is used in between the web with FM-73 and FM 490 Foaming adhesive at spliced area of the core maintaining center line carefully to join web and flange (cured in lsl stage) and cure in the Autoclave as per cure cycle SK/ALH/COMP/041 in the spar assembly. Insert potting is done on the spar before bonding to horizontal stabilizer.
10. Brief description of drawings
O) Fig. 1 (a): Main view of Spar assembly.
Q_ (b): Sectional view where flange and Web layers are shown.
^ Fig.2: First stage Flange tool and layup
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Fig.3: Web tool
Fig4: Flange supporting tool during flange and web joining
Fig.5: a),b) & c) Horizontal spar After curing
Fig.6: Metallic Insert potting
11. Statement of invention
The invented Composite Spar assembly is used in Horizontal stabilizer in choppers fabricated with fiber reinforced composite materials like carbon, glass, carbon UD, Nomex core, Metallic inserts

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A Signature of ihe Inventors Signature of the Applicant
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Name of the Applicant: Hindustan Aeronautics Limited, ACD. Sheet No: 5
Application No.: Total Sheets: 14
This invention is used in the helicopters The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The horizontal stabilizer prevents up-and-down, or pitching, motion of the aircraft nose.
12. Detailed description of invention
The composite Spar assembly is manufactured in two stages. The raw materials used in the manufacturing process are Carbon prepreg, glass prepreg, Carbon UD, Nomex core, Metallic inserts Adhesive film and peel ply. The prepreg materials are available in rolls with standard size, the material should be preserved in the cold storage at -18 deg. Temperature to upkeep the shelf life expiry. On removal from cold store the material has to be monitored for its working life i.e Room Temperature life for 30 days, with in its working life the material has to undergo curing process. The specified room temperature condition 24° to 30° and relative humidity 80% max to be followed during layup activity for the Slithering Boom.
The Prepreg material after removal from cold storage needs to be kept under room temperature about 6 hours for thawing purpose. Thawing allows material temperature from -18 deg.to room temperature. There by the prepreg materials is cut to the required size for layup and also the Nomex core is machined to the required size and shape. The prepreg material has two sides protective film on top and bottom surfaces. The mould with required geometry is used to obtain shape, during the layup the two-sided protective film needs to be removed. The layup mould is to be prepared as per standard work instruction.
The Spar assembly is a part used in Horizontal stabilizer in choppers fabricated with* fiber reinforced composite materials like carbon, glass, carbon UD, Nomex core, Metallic inserts etc(Refer Fig 1 for Main view and sectional view and Layup scheme).by using split mould. The component is fabricated in two stages. In first stage (Refer Fig 2), the layup is done for top and bottom flanges by using carbon and carbon UD and cured separately in autoclave (Curing parameters are heating and cooling rate at 1-3 deg/min C,lst dwell at 75+/-5 deg 40+5 minutes, second dwell 135+/-5 deg.C for 60+15 minutes, pressure 5 bar and vacuum 0.2 bar). In second stage layup is done for LH and RH web (Refer Fig 3 tool for web layup) and pre-compacted at 60 deg. C using vacuum and 1.5 to 2 bar pressure for 1 hr in autoclave. After Pre-compaction core is used in between the web with FM-73 and FM 490 Foaming adhesive at spliced area of the core maintaining center line carefully to join web and flange (cured in Is' stage-refer Fig 4 tool used for supporting flange) and cured in the autoclave (Curing parameters are heating and cooling rate at 1-3 deg/min C,lsl dwell at 75+/-5 deg 40+5 minutes, second dwell 135+/-5 deg.C for 60+15 minutes, pressure 2 bar and vacuum 0.2 bar) in the spar assembly Refer fig 5 for cured part. Insert potting is done on the spar before bonding to horizontal stabilizer(Refer fig 6)

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EN"T C*Hrai&- CHENNAI Q8/12/201/ 12= G
Signature of the Inventors Signature of the Applicant

Name of the Applicant: Hindustan Aeronautics Limited, ACD. Application No.:

Sheet No: 1 Total Sheets: 1

Annexure-II
Claims
What is claimed is:
1. A process for manufacturing composite spar assembly for an advanced light weight helicopter at minimum cost and optimum weight to accomplish better strength. It comprises of carbon, glass, carbon UD prepreg layers, Nomex core, Metallic inserts etc. and fabricated using a split mould. This component is fabricated in a unique way to obtain the structural integrity between the web and flanges.
2. The process as defined in the claim 1, said that the component is fabricated in two stages where in first stage the layup is done for top and bottom flanges by using glass and carbon UD and cured separately in autoclave and in the second stage layup is done for LH and RH web and pre-compacted. Finally the web and flange are cured in the autoclave per the standard cure cycle.
3. The process as defined in the claim 2, said the top and bottom flanges are fabricated on a separate tool and cured in autoclave at 135+/-5 deg.C for 60+15 min by applying 5 bar pressure and minimum 0.2 bar vacuum.
4. The process as defined in the claim 2, said the RH and LH web is precompacted after
layup in autoclave at 60 deg. C by applying 1.5 to 2 bar pressure for 1 hr.
5. The process as defined in the claim 2, said the pre-compacted web and the flanges are
bonded using an adhesive layers using a split tool and co-cured in an autoclave to obtain
as a single piece spar that is used for a horizontal stabilizer of an advanced chopper.