1 Title of the Invention

Tooling and procedure for blade folding of Rigid Rotor Helicopter

2 Field of the Invention

The invention relates to blade folding of a helicopter and more specifically

5 to development of simpie tooling to simplify blade folding of helicopter in a shipborne
hangar.·

3 Background of the Invention

Helicopter mostly uses four main blade system for its lift and flight. Main rotor blades are
designed having large diameter and high swept area. This
0 design feature causes severe impediment to its shipborne operations.

Shipborne operations mandates that helicopters have a blade folding feature to
reduce its width in lateral direction so that it can be accommodated in a
shipborne hangar. Hinge-less main rotor system or more commonly said rigid rotor system
used in 5- 5.5 Ton category
5 · helicopters require manual blade folding tooling to perform the blade folding
operation. Heavy helicopters can use automatic blade folding which utilizes complicated electro-
hydraulic mechanism to fold the blades. This has seve.re weight penalty and isn't
preferred. for lighU medium helicopters.

Smaller 3-3.5 Toh helicopters have fully articulated rotors and performing

0 blade folding is quite simple by detaching one or two bolts.

For rigid rotor system operating in shipborhe hangar it will be required either to remove the
blade or utilize some mechanism so that blades in lateral axis are folded to make them almost
parallel to longitudinal axis. Removal of blade is not a practical solution as it will require time
consuming
5 blade removal, installation procedure. Also complex rebalancing operation

will be required for this.

This title proposes a simplified single tool for achieving blade folding by minimally disturbing
the blade installation. By utilizing this simple tool
Title: Tooling and procedure for blade 'folding of Rigid Rotor. Helicopter

controlled blade folding can be achieved by even unskilled operators without doing any damages to
the blade or blade installation points.

3.1 Prior Art

Previously this operation was a·chieved through a combination of tools

consisting of Contour Pole and Support Beam, BeariNG off-loading tool.Earlier method involved utilization of more number of parts and also required more skilled
operation.

US patent 10287009 B2 provides the .detail about blade -folding kit developed for Apache
helicopter. This blade folding.kit is similar to Contour Pole and Support Beam, Bearing off-loading
tool and employs several loose parts to achieve blade folding.

4 Brief Summary of the Invention

This invention is about development of a simple single tool which can facilitate blade folding of
main rotor blade in a controlled manner. The blade folding tool has a blade support section whose
profile is similar to blade spoon region. It is used to clamp the main rotor blade on this tool. It
also has stopper provision to avoid· accidental overshooting of blade rotation. Main rotor blade is
attached to Blade fork on the helicopter through two blade fork bolts. Blade fork bolts has to be
removed to facilitate blade folding. Firstly the tool is installed on the main bolt of helicopter.
Conical bearing which takes the load in both radial and axial direction isn't disturbed. An offset
bolt called anti - rotation pin is installed on the conical bearing through inner housing to
prevent blades from rotating about the axis of attachment bolts, also needs to be removed for blade
folding.

After removal of blade fork bolts and installation of blade folding tool in main bolt, blade is
disengaged and moved so that it completely fits in the blade support section of the blade folding
tool. Blade support section has the same bushing as blade fork and removed blade fork bolts are
utilized for completely securing the blade folding tool installation. Main rotor hub where

main rotor blade gets installed ha·s holes for installation of Locking Pin of
,.
blade folding kit, which finally gets "attached with screw jack of blade folding kit. After
complete engagement of blades with blade support, further folding and unfolding can be done in a
controlled manner by operating screw jack of the tool.

5 Detail Description of the Drawings

Figure 1 shows the actual installation of Blade bearing and fork assy 1 to Main rotor hub 2 by
means of hollow Main Bolt 3 on a rigid hinge-less helicopter.

Figure 2 shows the actual drawing of Blade bearing and fork assy 1 with Main Rotor blade 4, Blade
Fork assy 5, Blade fork bolts 6 and 7. It also shows Conical bearing 8 installation on Main rotor
blade These two figures are only for illustration purpose and it helps defining the operation of tool
developed.

Figure 3 shows the Blade Folding Tool 100. It consists of a Box Assy 12 which has bushing·for
installation of Guide pin 9. Guide pin 9 gets installed on Box Assy 12 through Cap 17 and Rihg nut
A 18. Guide pin 9 gets installed on hollow Main Bolt 3 (Not shown in figure) Dowel Ring Nut 15.

Figure 3 also shows Blade Support Assy 10 which is installed on ai1other bushing of Box Assy 12
through Ring nut B 16 and Ring nut C 19. Blade Support Assy 10 is attached with a Screw Block 20
through which Screw
Jack Assy 11 is operated. Screw Jack assy 11 gets engaged through a Locking Pin Assy 14.For easier
handling there is a provision of Handle 13 which is installed on Box Assy 12.Through the use of
Ring nut B 16 and Ring nut C 19 vertical adjustment of Blade Support Assy 10 can be performed so
that main rotor blades directly gets fittedFigure 4 shows another view of the Blade Folding Tool 100 with its constituent part Box
Assy 12, Screw Jack assy 11 and Blade Support Assy
Claims

We claim1. A Blade Folding Tool 100 for folding and unfolding the Main Rotor Blade

4 comprising of

.Box Assy 12 for installation of Blade Folding Tool100 on Main Bolt 3

through Guiding Pi,n 9 and securing it through ap 17 al'ld Ring nut A

10 1,8;

Blade Support Assy 10 on which Main Rotor blade 4.ges fastened

· while performing blade folding;

Screw Jack assy 11 and Locking Pin Assy 14 which gets interlocked for.folding and unfolding of
blades;

Other attaching parts Dowel Ring Nut 15, Handle 13, Screw Block 20,
and Ring nut B 16 and Ring nut C 19.

2. Procedure for blade folding and unfolding by means of a Blade Folding Tool

100 as defined in claim 1, through disengagement of original blade fork bolts,

20 engagement of Blade folding tool 100 by insertion of Guide Pin 9, Completion of
installation by proper installation of blade fork bolts on Blade Support Assy
10 after carefully placing the blade on Blade Support Assy 10, thereby folding the blade with the
use of Screw Jack Assy and finally unfolding the blades.