1 Title of the Invention

Methodology and setup for proof pressure testing of ALH Main Rotor Actuators.

2 Field of the Invention

The invention relates to Servo Hydraulic system and more specifically to design and methodology of Hydraulic system Test stand. By this invention hydraulic performance of Flight control Main actuators are ascertained before installation on helicopter.

3 Background of the Invention

Background description includes information that may be useful ih understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Helicopters employ three main rotor actuators for changing the main rotor blade angles and providing controls for collective, pitch and roll control channels .The collective actuator controls the upward and downward movement of the helicopter.The pitch and roll controls the forward-backward movement and the angular movements respectively. These actuators are hydraulically powered and transmit the cockpit control input to the rotors by amplifying the efforts put by the pilot.

Two independent hydraulic systems are dedicated to power the actuators. These actuators will be normally working utilizing both the hydraulic systems (206 bar pressure) and in the event of one hydraulic system failure, the actuator continues to work on the other hydraulic system. With this when both the hydraulic systems are in operation the helicopter can be flown within its full flight envelope and under one hydraulic system failed condition helicopter can be safely flown under reduced flight envelope.
As part of servicing, it is necessary to validate the performance and integrity of these Main rotor actuators. By this setup actual flying condition can be simulated and main rotor actuators can be proof pressure tested separately for leakage, cracks and its performance.

3.1 Prior Art

Previously the main rotor actuators are checked for leakage and integrity directly insitu on helicopter. In case there was leakage noticed the all the actuators were removed and sent for repair to lab. Lab test setup was similar to helicopter setup where all actuators were connected through a specially made hydraulic manifold.

This lab setup doesn’t facilitate testing of single main rotor actuator as it doesn’t have provision for single manifold. Further as the proof testing procedure requires actuator to be tested at higher operating pressure (> 206 Bar), initial troubleshooting of actuators at helicopter level testing possesses considerable safety hazards.

4 Brief Summary of the Invention

When the actuators are reported to have leakage, the faulty actuator is dismantled and send to test setup for proof pressure testing. Further actuators are sent for 6 monthly performance check when kept in store. This test setup simplifies the proof pressure procedure and enables testing of main rotor actuators individually by means of specially made manifold and hydraulic circuitry.

The test setup consists of single manifold & a mounting fixture to mount the main rotor actuator. Through the help of direction control solenoid valve pressure is applied for both the hydraulic system and through the procedure as provided later the proof pressure testing is performed and serviceability of main rotor actuator is ascertained.
5 Detail Description of the Drawings

Figure 1 shows the hydraulic circuitry of test stand (100) for carrying out

j

proof pressure testing of main rotor actuator.

The test stand (100) as shown in Fig 1 consists of a Hydraulic test Rig (1) of oil tank capacity 100 litres having Pump (5), Strainer (2), Check Valve

i

which opens at 0.5 bar (7), Breather (4), pressure relief valve (6), Level sight Gauge (3) and drain port with shutoff valve (10) as its constituent parts.

Pressure and Return Lines of Hydraulic Test Rig is shown as P and R in Figure-1.

Pressure regulation for testing is done by Directional Control Valve (8) as shown in Figure 1.

Test stand (100) is installed with pressure gauges (9) to measure the pressure and thereby finding the leakages as shown in Fig 1. Test stand is also installed with pressure relief valve (6) and check valve (7) as shown in Figure -1.

It consists of a single manifold (11) which is fabricated from aluminum sheet and is supported on a rigid aluminum stand. It is separately shown in Figure 2

6 Detail Description of the Invention

As part of proof pressure testing main rotor actuators are subjected to higher operating pressure i.e 306 bar for pressure line and 155 bar to the returh line for 3 mins. Thereafter any abnormalities or leakage is verified. This process requires a hydraulic test rig (1) of 100 litre capacity which is capable of producing such kind of pressure. The hydraulic test rig (1) is compatible with a grade of MIL-H-5606 G hydraulic oil.

The hydraulic test rig (1) is used to regulate and maintain pressure of hydraulic fluid and also acts as reservoir for test bench. The main function
of hydraulic test rig (1) is to regulate pressure from 0 to 310 bar. It has reservoir capacity of 100 Litre.

The hydraulic test rig (1) is installed with -

• 25 p filler breather (4) for filling the hydraulic oil

• Drain with shut-off valve (12)

• Visual oil level sight gauge (3) with high, low and run indication.

• Pump (5) suction from the reservoir is through a Strainer (2). The pump case drain is drained back to tank directly.

• Pump (5) is a variable delivery pump capable of producing 310 bar of pressure at 10 Ipm

• An inline check valve (7) opening at 0.5 bar, 350 bar working pressure rated

• Pressure relief valve (6) which is adjustable from 8- 350 bar pressure

The hydraulic test rig (1) is connected to a directional control valve (8) operated at 28 V DC which regulates the pressure supplied. It also changes the flow from pressure line to return line.

Single Manifold (11) is having provision of Sys 1 and Sys 2 pressure line and return line ports. It is having provision of connection of pressure line and return line.

Pressure line P and Return line R is connected to single manifold (11) and through directional control valve (8) pressure is regulated.

Detailed procedure for carrying out testing is as follows-

A. Proof pressure testing
a) Faulty main rotor actuator is mounted on the Manifold (11) with bolts and nuts.

b) Pressure line and return lines of hydraulic test rig (1) is connected to the manifold (11) interface of system 1 and system 2.

c) Directional Control valve (8) is operated through a control box to allow the pressure to both systems.

d) Pressure of 306 bar is applied through hydraulic test rig (1) to the pressure line for 3 minutes and observation are taken for any leakages.

e) Directional Control valve (8) is operated to change over from pressure port to return ports.

f) Pressure of 155 bar is applied to the return line for 3 minutes and observation are taken for any leakages.

B. Cycling test also is a part of completed check and is performed as follows-

a) Faulty main rotor actuator is mounted on the Manifold (11) with bolts and nuts.

b) Pressure line and return lines of hydraulic test rig (1) is connected to the manifold (11) interface of system 1 and system 2.

c) With supply pressure of 50 bar, input lever of faulty actuator is operated gently from end to end for 10 cycles, slowly pressure is increased to 206 bar and 25 full stroke operating cycles by operating mechanical input lever is done.