Description:1 Title of invention
Drop tank rear mount bracket assembly for in-flight safe separation from aircraft.
2 Field of invention
The present invention is related to mechanical engineering in general and more particularly to the carriage of a drop tank (500)at the external station/hard points of an aircraft and the safe separation of the drop tank (500) from the aircraft during flight.
3 Background of invention
Drop tanks are used to increase the flight endurance of an aircraft with additional fuel. These drop tanks are attached below the wing at different stations/hard points. In a particular case, where the drop tanks are required to be dropped or separated from the aircraft in full fuel, partial fuel, or empty fuel conditions. From drop tank separation analysis, it was found that the nose portion of the drop tank was likely to hit the aircraft after jettison due to the pitch-up tendency of the unguided drop tank. It is understood that this pitch-up tendency happens due to the aerodynamic center of pressure falling ahead of the center of gravity of the drop tank. Separation of the drop tank from the aircraft during flight tended to pitch up and damage the aircraft structure (wing &fuselage). This in turn results a catastrophic effect on the aircraft and crew.
4 Brief Summary of invention
As the drop tank(500)attached to the aircraft tends to pitch up during jettison, the present invention of a rear mount bracket assembly (300) is designed to have a safe in-flight separation of the drop tank(500) from the aircraft during jettison. In this mechanism, a C- hook(510) which is permanently attached to the drop tank (500) forms a hinge joint with link-2 (110) of rear mount bracket assembly (300). During jettison, the drop tank (500)disengages with the Ejector release unit (ERU) (610) and has contact with the hinge mechanism at the rear mount bracket assembly (300) till 20°of rotation of drop tank(500) with respect to hinge horizontal axis. During this 20° of rotation of the drop tank (500), the contact area of C-hook (510) with link-2 (110) reduces continuously and it becomes zero at the moment of separation of the drop tank (500)from the aircraft. The present invention avoids the pitch-up tendency of the drop tank and ensures the safe separation of the drop tank (500) from the aircraft.
5 Brief description of drawings
Fig-1 is a side elevation of the drop tank (500) installation under the wing (700) of the aircraft by using an ejector release unit (610) installed inside the pylon (600) along with Bracket-Unified (400).
Fig-2is a detailed view of the side elevation of drop tank C-hook (510) engagement with rear mount bracket assembly(300),in the installed condition, under the bracket-unified (400)with adjusting M-20 special hexagonal nuts (520).
Fig-3 is a sectional view along the line 1-1 of Fig. 2, showing the drop tank C-hook(510) engagement with rear mount bracket assembly(300) in installed condition under the bracket- unified (400) with adjusting M-20 special hexagonal nuts (520).
Fig-4shows the perspective view of the drop tank (500) rear mounts bracket assembly (300) with Bracket-Unified (400).
Fig-5shows the exploded front view of the drop tank (500)rear mount bracket assembly (300)which includes a rear mount bracket (100), link-2(110), special bolt (120), bush (130), stopper (140), plurality of special pin (150), washer (160), nut castle (170), hexagonal nut (180),split pin (200) and inspection window (800).
Fig-6shows the exploded back view of the drop tank (500) rear mount bracket assembly (300) for installation of link-2 (110)by using a plurality of special pins (150),a washer (190),and a plurality of split pins (210). Further, the Inspection window (800) is provided for ensuring proper engagement of the C-hook (510) with the link-2 (110).
6 Detailed description of invention
Typically, military aircraft carry external drop tanks (500) at different stations/hard points at the wing (700) or fuselage. The drop tank(500)is usually installed under a pylon (600).The Pylon (600) contains Ejector Release Unit (ERU) (610) to attach the droppable stores or drop tanks (500). In the case of drop tank separation from the aircraft during flight, it is observed that the drop tank(500) in full fuel or partial fuel, or empty condition tends to pitch up and damage the aircraft structure such as wing (700)or fuselage. This in turn results a catastrophic effect on the aircraft and crew. The pitch-up tendency is due to the aerodynamic center of pressure falling ahead of the center of gravity of the drop tank(500).
The present invention of the rear mount bracket assembly(300) is designed to have a mechanical hinge to rotate the drop tank(500) by a 20° nose-down angle before it separates from the aircraft. Therefore, the rear mount bracket assembly(300) serves as a mechanical hinge guiding the drop tank(500) by having contact up to 20° rotation of the drop tank(500). This in turn avoids pitch-up of the drop tank(500) and ensures the safe separation from aircraft during flight. Refer to Fig-1 for a side elevation of the drop tank (500) installation under the wing (700) by using an ERU (610) and a bracket-Unified (400) at forward attachment (620) and rear attachment (630) respectively. The ERU(610) and the bracket-Unified (400)are installed inside the pylon (600).
During the installation of the drop tank (500) to the pylon (600), a C-hook (510) on the drop tank (500) slides and a link-2 (110) rotates till the C-hook (510) is seated on the link-2 (110). Refer to Fig.2. The C-hook (510) is permanently attached to the drop tank (500) at the rear cone, forming a hinge joint with the link-2 (110) of the rear mount bracket assembly (300).The Inspection window (800) on the rear mount bracket (100) is used for ensuring proper engagement of the C-hook (510) with the link-2 (110).
The C-hook (510) is pushed against the link-2 (110) by rotating a stopper (140) with an Allen key and screwing/unscrewing the C-hook (510) of the drop tank (500) for height adjustment. The Link-2 (110) is installed in the rear mount bracket (100) using a bottom special pin (150). Hand tightening of the top and bottom M-20 special hexagonal nuts (520) is followed to lock the position of the C-hook (510) on the drop tank (500). Refer to Fig.2, Fig.3, Fig.4, Fig.5,and Fig.6.The position of the part shall be observed through the inspection window (800) on the bracket (100) by loosening the stopper (140).The contact surface of the link-2 (110) with the C-hook (510) of the drop tank (500) is provided with a hardened surface finish.
Fig.5 and Fig.6 show the exploded perspective view of the rear mount bracket assembly (300), which includes a rear mount bracket (100), link-2(110), special bolt (120), bush (130), stopper (140), special pin (150), washer (160), nut castle (170), hexagonal nut (180), and split pin (200).Fig-6 shows the exploded perspective view of the rear mount bracket assembly (300) for installation of link-2 (110) by using a special pin (150), washer (190), and split pin (210).
The rear mount bracket (100) is part of the rear mount bracket assembly (300). The bracket (100) is made of high-strength NCM steel. The bracket (100)is installed under the bracket-unified (400) and the forward shape provided on the rear mount bracket (100) has a lower aerodynamic drag during flight operations of the aircraft. The top portion of the bracket (100) is butting with the lower surface of the bracket-unified (400) which establishes more surface contact between the rear mount bracket(100) and the bracket-unified(400) resulting in better transfer of the side loads. Referring to Fig. 2, the rear mount bracket (100) is provided with an inspection window (800) to ensure the engagement of the C-hook (510) with the link- 2 (110).
During jettison, the drop tank (500) is disengaged from the ejector release unit (ERU) (610), but the tank (500) has contact with the hinge mechanism at the rear mount bracket assembly (300) till 20°of rotation of drop tank(500) with respect to the hinge horizontal axis. During this 20° of rotation of the drop tank (500), the contact area of C- hook (510) with link-2 (110) continuously reduces and becomes zero at the moment of separation of the drop tank (500)from the aircraft. The C-hook (510) is fitted on the drop tank (500) with two M-20 special hexagonal nuts (520). This engages with the link-2 (110), which is housed in the rear mount bracket (100) using two special pins (150), a washer (190), and a split pin (210).
The objective of the rear mount bracket (100) is to have contact with the aircraft (forming hinge) and rotate the drop tank by a 20° nose-down angle before it separates from the aircraft. The pitch-up tendency of the drop tank (500) just after the jettison is controlled by having a hinge connection at the rear portion of the drop tank (500). A mechanism is established wherein the hinge is designed by the contact between the structural element of the aircraft structure and the drop tank(500), which helps in the safe separation of the drop tank (500) from the aircraft during jettison.
The present invention avoids the pitch-up tendency of the drop tank and ensures the safe separation of the drop tank (500) from the aircraft.
, Claims:We claim:

1. A drop tank rear mount bracket assembly(300) for in-flight safe separation of the drop tank (500) from an aircraft, in the event of jettison during which the drop tank (500) disengages from a ejector release unit (610),is designed to interface between a bracket-unified (400) of the aircraft pylon (600) and a C-hook (510) fitted on the drop tank (500) with a plurality of M-20 special hexagonal nuts (520) , characterized in that, the assembly (300) is comprising:

- a rear mount bracket (100), made of high strength steel, installed under the bracket-unified (400), with a forward shape to enhance the lower aerodynamic drag during flight operations of the aircraft;

- a plurality of special bolts (120),bushes (130), washers (160), nut castles (170), and split pins (200) to secure the rear mount bracket (100) to the bracket-unified (400);

- a link-2 (110), made of high strength steel, installed inside the rear mount bracket (100) by using a plurality of special pins (150), washers (190), and split pins (210) to engage with the C-hook (510) of the drop tank (500);

- an inspection window (800) on the rear mount bracket (100) to ensure that the C-hook (510) is properly engaged with the link- 2 (110); and

- a stopper (140) that is installed on the rear mount bracket (100) and secured with a hexagonal nut (180) to push the C-hook (510) against the link-2 (110), and it operates such that, though the drop tank (500) is disengaged from the ejector release unit (610) during the jettison, the tank (500) maintains a contact with the hinge mechanism at the bracket assembly (300) till 20°of rotation of the tank (500) with reference to the hinge horizontal axis, the contact area of the C-hook (510) with the link-2 (110) reduces continuously during the 20°of rotation of the tank (500) and it becomes zero at the moment of separation of the drop tank (500) from the aircraft, and thereby a mechanism is established wherein the hinge is designed by the contact between the structural element of the aircraft structure and the drop tank (500) that ensures the safe separation of the drop tank (500) from the aircraft during the jettison.

2. The drop tank rear mount bracket assembly (300) for in-flight safe separation of the drop tank (500) from an aircraft, as claimed in claim 1, wherein, the rear mount bracket (100) is having contact with aircraft, forming hinge, that rotates the drop tank (500) by 20° nose down angle before it separates from the aircraft, and thereby, the pitch-up tendency of the drop tank (500) just after the jettison is controlled by having the hinge connection at the rear portion of the drop tank (500).