1) Title of the invention
DESIGN AND DEVELOPMENT OF A GROUND BASED SYSTEM FOR TESTING OPTICAL MAIN ROTOR TRACKER.
2) Field of invention
It is an optoelectronics engineering design, which comes into operation during the deployment of helicopter flights.
3) Use of invention
A compact and portable system for testing the Main Rotor Tracker sensor on ground and establish its functionality before installing it on the Helicopter prior to rotor track and balance test flights.
4) Prior art
The Main rotor tracker contains an optical receiver, which generates a pulse when there is a drop in the intensity of light. The pulse generated is transmitted to signal processing unit to measure the track based on the pulses. The main rotor tracker is a part of Vibration Monitoring System (VMS) used in tracking and balancing of the main rotor blades of a helicopter. Frequent failures of the tracker sensor was reported after the flights. This was leading to wastage of rotor track and balance flights, as there is no means to test the tracker unit on ground. Vendor had supplied breakout box to test the unit, it requires to power ON the helicopter power to test.
5) Draw backs of prior art
There are few shortcomings in the vendor supplied break out box which is mentioned below:
• Break out box supplied was heavy to carry
• To check the unit, it is required to power ON the helicopter power
• Too complex to use and test
• It also require to know few of the wiring details of VMS
6) Comparison between prior art and present invention
The present invention is portable to use in the lab as well as field environment. It works on 1-phase domestic power supply and light in weight. To work with this test equipment no prior training is required.
7) Aim of the invention
The requirement was raised from the field to develop a lab testing equipment which would declare tracker unit serviceability before fitted on the helicopter to be used for rotor track and balance flight tests.

Summary of the present invention
In the present design, equipment is designed to work with domestic power supply. And to test the sensor no special setup is required. The Main Rotor Tracker of a helicopter is an equipment which is used in tracking and balancing of the Main Rotor blades to ensure that all the blades are in the same track at any given location. It contains an optical receiver which generates a pulse when there is a drop in the intensity of light in the path of the receiver. Using this principle it detects the track of the blades and based on this data the VMS software generates an appropriate correction to be given to the individual blades to keep them all in the same track. It has self-contained power modules to power the sensor and test equipment as well. Brief description of drawings
The Figurel explains the basics principle of operation of Main rotor tracker. The Figure 2 illustrates tracker tester unit block diagram. The Figure 3 depicts the portable tracker tester unit along with main rotor tracker sensor.
) Statement of invention
The present invention and design is a compact and portable system for testing the Main Rotor Tracker on ground. It helps ground crew to establish its functionality before installing it on the Helicopter to carry out track and balance flights.
) Detailed description of invention
Most of the times track data would be missing after carrying out an RTB flight due to the
malfunctioning / failure of the tracker. In to the absence of a dedicated test equipment, there
exists no means to find out the functionality of the tracker except by conducting a full-fledged
flight test which is time consuming and expensive.
In order to test the Tracker an equipment has been designed, which would simulate the checker
light pattern observed by the tracker's optical receiver. The output of the tracker has been fed
into a microcontroller which would measure the noise level, pulse amplitude and frequency of
the output waveform.
The design and development of the portable test equipment is done by addressing the following issues and solving it to suit the requirement. First job is to find out power distribution scheme to power the entire unit along with the tracker under test. There exists a requirement to generate

the pulses to simulate the real time environment under rotor by designing high speed switching circuit to. control the flashing time of a high power LED. Unit developed is tested with various tracker units to establish a threshold values for tracker pulse. With the unit and tracker powered ON mode, output from the tracker unit is measured to find out the noise level if any and pulse amplitude. The pulse output amplitude and frequency is measured by neglecting the noise levels present in the measured signal. Measured output is compared with the target values to find out serviceability of the tracker under test and status is displayed on a LCD screen. An algorithm has also been developed and coding is carried out, it is imported onto the microcontroller which would establish the tracker's condition and display this on a LCD screen.


Claims
We claim that,
1. Easy to test the tracker sensor on lab facility thereby increasing the confidence in conduction of track and balance flights.
2. Initially, it is designed to work with domestic power supply available in the lab and' does not require any special arrangement to use this unit.
3. A portable and compact system to test the Main Rotor tracker of a Helicopter has been designed and developed.
4. Algorithm to check the unit has been developed and embedded coding is done, and ported to microcontroller.
5. The serviceability of the unit can be tested with the help of portable unit developed. This enables the ground crew to take quick actions.
6. Easy to use and test the sensor unit due to simple and robust design thereby saving
expenditure on rotor track & balance flights.
7. The units tested and offered for flight have been validated by means of flight tests
successfully at RWR&DC, HAL