2) Field of invention
It is a mechanical engineering design which comes into operation during the EASA certification for Tail Rotor blade Bird strike test.
3) Use of invention
• This invention finds application in the Bird strike testing of Tail Rotor Blade.
4) Prior art
In the previous design, Tail Rotor blade pair was attached to the hub at the centre of flex beam with complete blade airfoil open along the axis of gun.
5) Draw backs of prior art
There are few shortcomings in the earlier design which is mentioned below:
• The air gush from the air gun used to cause the blade flap away/deviate from the bird travel axis before the bird is released on to the blade.
6) Comparison between prior art and present invention
In present set up blade aerofoil is completely covered with specially designed housing except location of bird hit point. This avoids flapping of blade from axis of bird hit gun. Where as in early set up blade was completely open and because of air gust of gun flapping away from axis of bird hit gun.
7) Aim of the invention
The prime objective of the invention is to avoid the flapping of blade due to air gust of gun.
8) Summary of the present invention
For conducting the Bird Hit test on Tail Rotor Blade, the blade pair assembly is attached to the hub at the centre of flex beam with 7.8 degree of pitch angle as shown in fig-1. As the air gust from the air gun passes through the aerofoil, blade is flapping away from the gun axis and missing the bird to hit the target.
A special housing is designed to cover the blade aerofoil and maintaining the blade pitch angle of 7.8 degree as shown in fig-2.This design eliminate the flow of air gust coming from air gun through aerofoil and it does not allow to flap away the blade.

9) Brief description of drawings
The Figurel explains the basic of prior design where blade aerofoil is open arid bird hit point is along the axis of gun. The Figure 2 illustrates special housing designed to cover the airfoil of blade.
10) Statement of invention
Design of fixture for holding Tail Rotor Blade to prevent it from flapping away from the air gun axis during Bird Hit test
11) Detailed description of invention
The Tail Rotor Blade Pair assembly comprises of two opposite aero foils molded on single flex beam. The blade pair assembly is attached to the hub at the centre of the flex beam. The pitch angle of the blade is se-t at 7.8 degree. The air gush from the air gun used to cause the blade flap away/deviate from the bird travel axis before the bird is released on to the blade.
The attachment of tail rotor blade pair to the holding fixture is as shown in Fig 1. The blade pair is installed between the hub plates at the center of it. The portion of the blade above the bird hit zone is housed inside the housing to prevent theblade from moving side wards, so that bird hit point on the blade is in line with the gun axis/bird travel path.
The special housing maintains blade pitch angle of 7.8 degree, keeps the alignment of bird hit point on the blade with the bird hit axis, and prevents the blade from flapping side wards. The housing allows bird to travel through it and hit the blade at the specified and aligned location. Fig. 2 shows the mechanism of holding and housing the blade within the fixture.

Claims
We claim that,
1. The design concept of blade holding mechanism which retains the alignment and holds the
blade in the desired position.
2. The special housing maintains blade pitch angle of 7.8 degree, keeps the alignment of bird hit
point on the blade with the bird hit axis, and prevents the blade from flapping side wards. The housing allows bird to travel through it and hit the blade at the specified and aligned location. Fig. 2 shows the mechanism of holding and housing the blade within the fixture
3. Methodology adopted in using the concept of cushioned housing to prevent the damage of the
blade due to bird impact.