FORM 2 THE PATENTS ACT, 1970
(39 of 1970)& The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION Device for checking Airflow Angle Sensor Installed on Aircraft
2. APPLICANT(S)
(a) NAME: HINDUSTAN AERONAUTICS LIMITED
(b) NATIONALITY: INDIAN
(c) ADDRESS: AGM(D), DESIGN ELECTRICAL.HAL, NASIK

3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL The following specification describes the invention.
X COMPLETE The following specification particularly describes the invention and the manner in which is to be performed.

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4. DESCRIPTION (Description shall start from next stage.) Refer Annexure I
5. CLAIMS (Not applicable for provisional specification. Claims should start with the preamble - "I/We claim" on separate page)
Refer Annexure II
6. DATE AND SIGNATURE (to be given at the end of last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on separate page)
Refer Annexure III
Note:-
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* To be signed by the applicant(s) or by authorized registered patent
agent.
* Name of the applicant should be given in full, family name in the
beginning.
* Complete address of the applicant should be given stating the postal
index no./code, state and country.
*Strike out the columnfs) which is/are not applicable.

Complete Specification of
Device for checking Airflow Angle Sensor Installed on Aircraft

1 Title of the Invention
Device for checking Airflow Angle Sensor Installed on Aircraft
2 Field of the Invention
The invention relates to design and development of device for Checking Airflow Angle Sensor Installed on Aircraft.
3 Background of the Invention
The fighter aircrafts are equipped with airflow angle sensors which is known as Angle of Attack (AOA) Sensor and Side Slip Angle Sensor Angle of Attack Sensors which are installed in l_H / RH side of nose cone area and one number of Side Slip Angle Sensor which is installed in bottom of nose cone area. These Angle of Attack and Side Slip Angle Sensors are moving vane type which can freely move in response to the air stream as aircraft maneuvers. The corresponding deflection angles of the vane are sensed via four potentiometers inbuilt inside the airflow angle sensor. The airflow angle parameters (angle of attack and side slip angle) are essential inputs for flight control system (i. e. Fly By Wire) system, which is a safety critical system for the aircraft. The Fly By Wire (FBW) control system is quadruple redundant system, which takes the airflow angle parameters through the four different potentiometers of the sensor. The potentiometer outputs are quorum inside the FBW system to generate the control algorithms in longitudinal direction. Considering the importance of angle of attack and side slip angle parameters from the aircraft safety point of view, it becomes very much essential to ascertain the serviceability status of airflow angle sensors.
For ensuring the serviceability of airflow angle sensors installed on aircraft no test procedure is available. In the event of any suspected failures, these airflow angle sensors need to be removed from the aircraft and then send to the lab for fault confirmation. In case when fault is not confirmed at the lab, these airflow angle sensors are again sent for installation on the

aircraft. Subsequent to this re-installation and harmonization of these sensors which is a mandatory requirement, needs to be carried out. The entire activity (during snag analysis) takes the significant amount of time which includes sensor removal, re-installation and harmonization process. This leads to increase in the downtime of the aircraft
4 Brief Summary of the Invention
To overcome this down time in the event of suspected failures of Angle of Attack and Side slip angle sensors, "Innovative instrument for Checking of Airflow Angle Sensor Installed on Aircraft" is developed. This Air Flow Angle sensor instrument can detect and indicate the failures associated with sensor installed on the aircraft. The instrument can be directly connected with the sensor installed on aircraft without removal to monitor its four potentiometric excitation and output voltages at different degree of deflection angle. In the event of failures in any one of the potentiometers it indicates the health status of the sensor through LED indicator and BUZZER sound. The provisioning is also made to test the heating system serviceability for the body heating, half and full mode heating of airflow angle sensor. The serviceability of the heater circuit can be ensured through LED indicator along with heater circuit current and voltage values. The newly developed test equipment ensures full functionality of airflow sensor insitu on aircraft without its removal.
The invention relates to design and development of Device for Checking of Airflow Angle Sensor Installed on Aircraft". This Air Flow Angle sensor instrument can detect and indicate the failures associated with sensor installed on the aircraft. The instrument can be directly connected with the sensor installed on aircraft without removal to monitor its four potentiometric excitation and output voltages at different degree of deflection angle. In the event of failures in any one of the potentiometers it indicates the health status of the sensor through LED indicator and BUZZER sound. The provisioning is also made to test the heating system

serviceability for the body heating, half and full mode heating of airflow angle sensor. The serviceability of the heater circuit can be ensured through LED indicator along with heater circuit current and voltage values. The newly developed test equipment ensures full functionality of airflow sensor insitu on aircraft without its removal.
5 Detail Description of the Drawings
The instrument shall have cabinet with Front Panel. The control switches and operation mode indicators and meters are situated on the front panel. The device shall operate on In-built battery backup supply. An input supply plug, interfacing connectors and safety fuse shall be provided on cabinet such a way that these components will be protected from damages. The invention is illustrated with the help of the accompanying Figure-1 as given below:

Sr. No Module
1. Main Module
2. Display Device
3. Control Key and Switches
4. Signal Conditioning and monitoring circuit
9. DC Signal Conditioning Circuit and Monitoring Module

Sr. No Module
5 Display Device
6 Battery Module
7 Battery Charger and Management System
8 Power Supply and reference signal generation module

6 Detail Description of the Invention
The Angle of Attack & Side Slip angle sensors are moving vane type which is attached to the nose cone area of the aircraft. The sensing vane move in response to the air stream as aircraft maneuvers. The sensor converts the deflection angle of the moving vane in form of electrical signals. These generated

electrical signals are analog in nature which is measured by the instrument corresponding to deflection angle of vane. The electrical signals are further converted from analog to digital form. Subsequently these digital signals are processed and indicated through LCD display installed on the panel of test equipment. The technological features of the instrument are as follows:
Logical Algorithms based system design. The instrument is designed and developed based on embedded system technology. It comprises general purpose hardware components and microcontroller boards. The logical program is embedded in microcontroller board. This microcontroller board is interfaced through the LCD display indicator, LED lamp and BUZZER on the test equipment.
Inbuilt decision capability for failure indication: The provisioning is also made to indicate the health status of airflow angle sensors through LED indicator and Buzzer without removing from aircraft. In case any of the potentiometers of the airflow angle sensors are in defective condition, the FAIL LED lamp glows on the face panel of instrument and simultaneously BUZZER generate the beep sound.
Easy of operation and maintenance: The design of the instrument is such that it is easy to maintain and operate without any special skill thus reducing efforts and aircraft downtime.
The airflow angle sensor tester shall also be able to verify potentiometric and heater circuitry of body and vane of airflow angle sensors in the aircraft without removing the sensor from the aircraft.

CLAIMS We Claim,
1. A device for assessing serviceability of angle of attack sensor and side slip angle sensor in installed condition on the aircraft comprising :
- main module (1);
- display device (2) and (5);
- controlling elements (3);
- signal conditioning and monitoring device (4);
- battery module (6);
- battery charging and management system (7);
- power supply and reference signal generating module (8);
- DC signal conditioning and monitoring module (9) and;
- connecting elements (10) and (11);
where in different modules are electrically connected to one as other as follows;
- the main module (1) is electrically connected to display device (2),controlling element , battery charging and management system (7) and DC signal conditioning and monitoring module (9) which is also connected to connecting element (10) ;
- the power supply and reference signal generating module (8) is connected to connecting element (10) and signal conditioning and monitoring device (4);
- the commercial power supply input is connected to power supply and reference signal generating module (8);
aircraft power supply input is connected to signal conditioning and monitoring device (4) which in turn is

connected to the display device (5) and also provide provision for checking heating circuit of unit under test through connecting element (11);
2. The device as claimed in Claim-1 provides means for identifying fault in angle of attack and side slip sensor without removing from aircraft; and also prevents overheating of angle of attack sensor vane and sensor body heating when aircraft on ground .