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
Methodology and troubleshooting procedure for testing of aerial
refueling probe used in fighter aircraft
2. APPLICANT(S)
(a) NAME: HINDUSTAN AERONAUTICS LIMITED
b) NATIONALITY: INDIAN
(C) ADDRESS: SM(PP-SUROH), Aircraft Overhaul Division, Nasik
3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL The following specification describes the invention.
COMPLETE The following specification particularly describes the invention and the manner in which is to be performed.
4. DESCRIPTION (Description shall start from next stage.) Refer Annexure 1
5. CLAIMS (Not applicable forprovisional 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:-
*Repeat boxes in case of more than one entry.
*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 column(s) which is/are not applicable.

Complete Specification of
Methodology and troubleshooting procedure for testing of aerial refueling probe used in
fighter aircraft

1 Title of the Invention
Methodology and troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft
2 Field of the Invention
The invention relates to electrical, mechanical and aerospace engineering in general and the specifically to fighter aircraft repair.
3 Background of the Invention
Air-to-air refueling (or in-flight refueling) is an important strategic need for increasing endurance and range in a fighter manned and unmanned aircraft traveling long distances. Although Air-to-air refueling is relatively common operation in military fighter aircraft, the aircraft to be refuelled must be precisely positioned in air for safe engagement, dispense and detachment form the source aircraft. Air-to-air refueling system is intended to accept fuel from a source aircraft during flying. The source aircraft is equipped with refueling pod having airborne signalling device to indicate the position of refueling drogue transmitter with respect to refueling pod. First visual detection is done and the approach made with the help of Short Range Navigation system. Thereafter to maintain stability the refuel mode is engaged to control pitch angle and rolling angle. To receive the fuel, aerial refueling probe is extended by the receiving aircraft.
Aerial refueling probe is essentially an independent unit installed in the fuselage nose section. The lower part is connected to refueling pipeline. This aerial refueling probe is extended and retracted by hydraulic system of aircraft. In-case of failure of hydraulic system, only extension is possible using emergency pneumatic system of aircraft. When aerial refueling probe is extended, its head comes out away from the fuselage. The aerial refueling probe is locked in both up and down position with the built in lock. Structurally attached aerial refueling boom system consists of carrier casing, retractable hydraulic rod, angular branch pipe and multi-purpose

head. Aerial refueling probe head is of special type, whose features are given below:
a) The head provides access for connecting the source aircraft drogue.
b) The head is provided with weak member to limit loads, which are imposed on the refueling rod and fuselage attachment fittings.
c) In case the loads are exceeded in lateral direction, the weak member will be broken and the aerial refueling probe is protected against destructive loads.
d) The head is provided with check valves to prevent fuel leakage after the weak member is broken.
In addition, the closeness of the source aircraft and the second aircraft during air-to-air refueling operation may create the danger of midair collision between the aircrafts such a danger may increase, if the components of aerial refueling probe system during extension not operate properly. In case of removal, change or to replacement of the aerial refueling probe system form fighter aircraft, trial and error process is adopted for testing. It is a tedious, time consuming and resource intensive process. There exists a need for precise testing methodology of aerial refueling probe system that provides the proper testing of all alignment points for attachment on aircraft, measurement of travel of aerial refueling probe, illumination electric circuit check and also proper systematic diagnostic procedure in case of any snag, during the testing of aerial refueling probe and also to reduce the down time of used in fighter aircraft.
3.1 Prior Art
a) United States patent, Patent No.: EP1824734B1
Patent title: In-flight refueling system and method for preventing oscillation
in system component.
The present invention provides the method for facilitating in-flight
stabilization of extended hose and avoid oscillation and prevent dangerous
mid-air collision Though it is related to an aerial refueling probe system of

fighter aircraft, it is not related to the testing of aerial refueling probe system on ground to identify irregularities in the air to air refueling system.
b) United States patent, Patent No,: US 8814081B2 dated Aug. 26, 2014
Patent title: Aircraft and external pod for aircraft, it describes about the
general design aspect of aircraft fuel system and form of external pods.
External pods were used for storage of additional fuel for the aircraft, the
above patent describe the delivery of fuel from external pod by complex fuel
management system of aircraft. Though it is related to an aircraft fuel
system, it is not related to the testing of air-to-air refueling probe on ground
to identify irregularities in the air-to-air refueling system.
c) United States patent, Patent No.: US20170225797A1 dated Aug. 10,
2017
Patent title: Aircraft design for.air-to-air refueling, it describes about the general design aspect and method for aerial refueling or in-flight refueling of aircraft. It consists of external hose deployed for sending the fuel from tanker aircraft and forwardly position probe for receiving the fuel in the aircraft. However, do not describe ground testing method for snag identification of on-board air to air refueling system in fighter aircraft.
4 Brief Summary of the Invention
Aerial refueling probe system of fighter aircraft is an independent unit installed in the fuselage nose section, the mating structure and attachment point of refueling probe system is precisely aligned in the fuselage. The Aerial refueling probe system is connected with fuel aggregate of aircraft refueling pipeline and connected to the fuel tanks of aircraft. Aerial refueling probe is design for extension and retraction by hydraulic system and in-case of failure of hydraulic system, only extension is possible using emergency pneumatic system. When aerial refueling probe is extended, its head gets projected away from the fuselage.

Complex testing of aerial refueling probe system that provide the proper testing of all alignment points for attachment on aircraft, measurement of travel of probe, illumination electric circuit check and proper functioning of aerial refueling probe during actuation and testing of aerial refueling probe system. Present invention also contains proper systematic diagnostic procedure in case of any snag, during the testing of aerial refueling probe system reduce the down time in fighter aircraft.
5 Detail Description of the Drawings
The invention can be better understood by reading the detail description of the disclosed embodiment followed by the accompanied drawings:
Figure-1: Schematic diagram for testing of aerial refueling probe system of
fighter aircraft.
Figure-2: Testing methodology for aerial refueling probe system for
hydraulic actuation and testing.
Figure-3: Testing methodology for aerial refueling probe system for
pneumatic actuation and testing.
Figure-4: Testing methodology for aerial refueling probe system for fuel
testing.
Details of figure 1 to 4
1: Device to test aerial refueling probe system.
2: Hydraulic supply, actuation & testing system.
3: Connecting element for Hydraulic supply.
4: Alignment unit.
5: Angle measuring device.
6: Timing measuring device.
7; Height measuring device.
8: Pneumatic supply, actuation & testing system.
9: Connecting element for Pneumatic supply.
10: Fuel supply & testing system.
11: Connecting element for Fuel supply.

12: Timing measuring device.
13: Electrical supply & testing system.
14: Connecting element for Electrical supply.
15: Insulation tester.
16: Continuity tester.
17: Connecting element.
18: Electric power supply.
19: Aerial refueling probe system.
6 Detail Description of the Invention
A full understanding of the invention can be gained, when wherein parts are
referred by the numerals read in conjunction with;
Figure-1: Schematic diagram for testing of aerial refueling probe system of
fighter aircraft.
Figure-2: Testing methodology for aerial refueling probe system for
hydraulic actuation and testing.
Figure-3: Testing methodology for aerial refueling probe system for
pneumatic actuation and testing.
Figure-4: Testing methodology for aerial refueling probe system for fuel
testing.
A device to test the aerial refueling probe system (1) is made of metallic frame as alignment unit (4) used for precise alignment at specific mounting point for securing, actuation and testing aerial refueling probe system (19) of manned and unmanned fighter aircraft. Hydraulic supply, actuation & testing system (2) is used to find out the leakage, if any, with high pressure and low pressure test, hydraulic supply, actuation & testing system (2) is connected to alignment unit (4) and aerial refueling probe system (19) with connecting element for hydraulic supply (3). Hydraulic supply, actuation & testing system (2) is connected with Electric power supply (18) through connecting element (17).

a. During testing of hydraulic system desired pressure is generated by hydraulic supply, actuation & testing system (2) for testing. Serviceability test of aerial refueling probe system is checked by actuating the aerial refueling probe system through high pressure hydraulic line and monitor the test results using angle measuring device (5), timing measuring device (6) and height measuring device (7). Refer fig No. 2 for flow chart of aerial refueling probe system for Hydraulic actuation & testing. Troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft for hydraulic actuation and testing is for identification of type failure and probable cause of failure.
Table No.1: Troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft for Hydraulic actuation and testing.

Sr No Failure Probable Cause
1 Alignment check a. b. c. d. e. Misalignment Structure deformation Bending of extension rod Mounting point damage Excess play on mounting point
2 High pressure leak test a. b. c. a. b. c. Structure deformation Bending of extension rod Sealing ring damage
3 Low pressure leak test
Structure deformation Bending of extension rod Sealing ring damage
4 Gravitational force leak test a. b. c. Structure deformation Bending of extension rod Sealing ring damage
5 Strength test a.
b. Sealing ring damage Structure damage
b. Pneumatic actuation & testing system (8) is connected to alignment unit (4) and aerial refueling probe system (19) with connecting element for pneumatic supply (9).
Serviceability test of aerial refueling probe system is checked by actuating the aerial refueling probe system through pneumatic supply line and monitor

the test results using angle measuring device (5), timing measuring device(6) and height measuring device (7). Refer fig No. 3 for flow chart of aerial refueling probe system for Pneumatic actuation & testing. Troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft for Pneumatic actuation & testing is for identification of type failure and probable cause of failure.
Table No.2: Troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft for Pneumatic actuation and testing.

Sr Failure Probable Cause
No
1 Extension angle a. Misalignment
b. Structure deformation
c. Bending of extension rod
d. Mounting point damage
e. Excess play on mounting
point
2 Extension time a. Structure deformation
b. Bending of extension rod
c. Sealing ring damage
d. Misalignment
e. Mounting point damage
f. Excess play on mounting point
3 Extension height a. Structure deformation
b. Bending of extension rod
c. Sealing ring damage
c. Fuel testing system (10) is connected to alignment unit (4) and aerial refueling probe system (19) with connecting element for fuel supply (11). Fuel supply & testing system (10) is used to test the desired flow of fuel from the aerial refueling probe and time through timing measuring device (12). Refer fig No. 4 for flow chart of aerial refueling probe system for Fuel testing. Troubleshooting procedure for testing of aerial refueling probe used in fighter aircraft for fuel testing is for identification of type failure and probable cause of failure.

Table No.3: Troubleshooting procedure for testing of aerial refueling probe for Fuel testing.

Sr Failure Probable Cause
No
1 Fuel testing a. Misalignment
b. Structure deformation
c. Bending of extension rod
d. FOD
d. Electrical supply & testing system (13) is connected to alignment unit (4) and aerial refueling probe system (19) with connecting element for electrical supply (14) and use to measure the Insulation resistance of electric by Insulation tester(15) and serviceability of illumination circuit by continuity tester (16). Electric power supply (18) is connected to the (10), (2), (8) and (13) using connecting element (17).

Claims
We Claim,
1. A methodology for testing of aerial refueling probe (19) for fighter
aircraft in alignment unit (4) at device (1) for precise alignment
comprising:
hydraulic supply, actuation and testing system (2) for pressure test with connecting element for hydraulic supply (3) and serviceability check using angle measuring device (5), timing measuring device (6) and height measuring device (7);
pneumatic supply, actuation and testing system (8) for pressure test with connecting element (9) connected to alignment unit (4) and serviceability test using said angle measuring device (5), said timing measuring device (6) and height measuring device (7);
fuel supply and testing system (10) to test the flow rates of fuel from the probe and time through timing measuring device (12); and
electrical supply and testing system (13) connected with connecting element (14) to measure the insulation resistance of electric by insulation tester (15) and serviceability of illumination circuit by continuity tester (16);
2. The methodology claimed in Claim-1, isolated individual system testing
in modular design of aerial refueling probe system during ground
testing.