1. Title of the invention

Fuel System for Military Trainer Aircraft with Dihedral Wing Tanks with Auto Level Balancing and Supply Tank Pressurisation

2. Field of invention

It is a mechanical engineering layout design used for aircraft fuel system.

3. Use of invention

This invention finds its applicability in the fuel system of military trainer aircraft with dihedral wing tanks.

4. Prior art

Not applicable

5. Draw backs of prior art

Not Applicable

6. Comparison between prior art and present invention

Not Applicable.

7. Aim of the invention

Aim of the invention is to design an effective fuel system with reduced number of components and piping by introducing innovative components and ideas to reduce cost and weight of the system without sacrificing any of the operational and maintenance performances and emergency redundancies in meeting requirements for military trainer aircrafts with dihedral wing tanks.

8. Summary of the present invention

Effective fuel system is invented to have reduced number of components and piping by introducing innovative components and ideas to reduce cost and weight of the system without sacrificing any of the operational and maintenance performances and emergency redundancies in meeting requirements for military trainer aircrafts with dihedral wing tanks.
Continuous fuel feed at required pressure is ensured to the engine from the fuel system at all maneuovers including inverted flying.

9. Brief description of drawings

Fig-l shows the schematic layout of fuel system for military trainer aircrafts with dihedral wing tanks using motorized valves. Here the instrumentation schemes are not shown as they are common for present system and this invention.

10. Statement of invention

The fuel system is said to be effective as it is using reduced number of components and piping, introduction of innovative components resulting in reduced cost and weight of the system but without sacrificing any the performances or emergency redundancies in meeting requirements for military trainer aircrafts with dihedral wing tanks.

11. Detailed description of invention

Refer Fig-l. Fuel system has the following tanks called LH wing tank (1), RH wing tank (2), Pump chamber (8) and Supply tank (11).
A vent valve (3) & (4) are the type made from the concept of the patent filed with title "Aircraft Tank Vent Valve gravity-ball based"

A level balancing valve (5) is the type made from the concept of the patent filed with title "Aircraft Dihedral Wing Tank Fuel Level Balancing Valve"

A vent valve (10) is the type made from the concept of the patent filed with title 'Tank Vent and Pressurisation Valve Operated by Fluid Pressure"

Exit (6) of balancing valve (5) is connected to pump chamber (8). The connectivity is shown in dotted lines as the top and bottom views are different. Pump chamber (8) is housing an ejector / jet pump (9) inside. Pump chamber (8) also has a flap valve (9) as shown. Pump chamber (8) is laterally attached to the supply tank (11) which acts as inverted flying chamber also. A centrifugal pump (12) is mounted at the bottom sump portion of the supply tank (11) so that even the last fuel is pumped to engine and when aircraft goes for maneouver this sump zone will have fuel inside positively.

Supply tank (11) is maintained as fully filled condition at all the time so that during inverted flying air does not go into the suction side of the centrifugal pump (13).

Vent valves (3) 8t (4) are maintaining breathing of wing tanks at all the time; even in steep maneouvers. There are one more vent valves of each (3) and (4) mounted on the rear spar of the wing tank (not shown in Fig-1) in such orientation that they help breathing of tank in pitch - down meneouver. The vent valve shown in Fig-1 will maintain tank breathing during roll and pitch-up conditions.

As the wings are dihedral, fuel flows down to balancing valve (5) inlets by gravity. In addition, the ejector / jet pump keep sucking the fuel from wing tanks. Hence even though aircraft is not in level flying to aid gravity flow, the suction will help fuel transfer even during steep maneouvers.

Motive flow (7) of small flow rate i.e. high pressure flow is tapped from engine high pressure line to feed ejector pump (9); in turn ejector pump sends the pump chamber (8) fuel with high pressure to supply tank (11). At this time of transfer, flap valve (9) remains closed as the supply tank (11) pressure is more than the pump chamber (8). Supply tank maintains pressure with incoming fuel from ejector pump by closing the passage of the vent valve (10) using the same motive pressure fluid (7). The pressure build up in the tank (11) is the function of incoming fuel minus outgoing fuel (through (13)).

If required the tank (11) shall have an orifice at the top to have safe tank pressure. The bleed from orifice may be dropped to wing tanks.

Single point refueling is achieved by filling any one of the wing tank through filler cap. The fuel from this wing tank comes to balancing valve (5) and raises to other wing tank and also goes to supply tank (11) through exit (6), pump chamber (8), flap valve (9). Now, air in the top of (11) escapes through vent valve (10) as it is at default position (without fluid pressurization).

In case of failure of pump (12), the pressure inside the tank (11) will help boosting the engine
feed line (13).

Claims

1. System has reduced number of components and piping by introducing innovative components and ideas to reduce cost and weight of the system without sacrificing any of the operational and maintenance performances and emergency redundancies in meeting requirements for military trainer aircrafts with dihedral wing tanks.

2. A single and simple fuel system replaces the need of two non-return valves in the fuel transfer line and need of two electrically operated valves, tank content sensors and an electronic controller. Hence this invention addresses the draw backs in the present practices and in addition does the automatic fuel imbalance correction.

3. It uses a reliable simplified vent valve hence smooth venting at all phases of flying.

4. in addition, it enables the system to have single point refueling facility.

5. Through a simpler way of supply tank pressurization, system ensures a positive pressure in the feeding line going to engine.