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A METHOD AND SYSTEM OF AIRCRAFT ROLL CONTROL OR ROLL TRIM AND/OR ADVERSE YAW REDUCTION THROUGH FUEL TRANSFER IN WING FUEL TANKS

IP.com Disclosure Number: IPCOM000243482D
Publication Date: 2015-Sep-24
Document File: 7 page(s) / 156K

Publishing Venue

The IP.com Prior Art Database

Abstract

TECHNICAL FIELD This disclosure relates to a method of roll control or trimming the rolling moment of an aircraft, in particular a civil transport aircraft in its roll attitude though placement of fuel in wing fuel tank with the intention to generate a rolling moment due the differences in fuel quantity tank pairs (i.e. two fuel tanks at the mirrored locations on opposite wings). PROBLEM TO BE SOLVED AND PRIOR ART Typically aircraft roll control is achieved through the use of lift augmentation devices (e.g. ailerons) that differentially change lift on both wings of an aircraft to create a rolling moment for manoeuvring an aircraft this is illustrated by the figure below. The movement of ailerons in flight also incurs a drag penalty. Consider the following example, if a pilot wishes to effect a turn, the ailerons are commanded such that an aileron on one of the wings will move down and the one on the opposite wing will move up. The effect of an aileron moving down will be to increase the lift over that wing, whilst the aileron moving up will have a net effect of reducing lift on that wing. This essentially starts a roll. There are some secondary effects of this action. The wing, generating more lift will also generate more lift induced drag. The difference in drag between both wings also produces a tendency for the aircraft to yaw in the direction opposite to the intended direction of turn. This yaw tendency is referred to as adverse yaw. To overcome this situation, aircraft can be designed with a number of features which include: Frise ailerons: A patented device that when an aileron is deflected up (to reduce lift) there is a lip protrusion into the airflow. This increases drag on that wing. In the case of a down-going aileron the design is such that it is smooth and flush so as to reduce any drag. Differential Ailerons: These are designed so that the down-going aileron moves through less of an angle that the up-going aileron. Spoilers: These panels which can be raised on the upper wing surface. They can be designed to operate on the down-going wing in conjunction with a bank - again increasing drag on that wing to counter the "adverse yaw”. List of Prior Art Patents: US8613409 B2 24 Dec 2013 Olivier Cazals, Thierry Druot Aerodynamic flight control surface said of crocodile style for aircraft US6125882 * 16 Dec 1998 3 Oct 2000 Kong; Carl Cheung Tung Fluid transfer system. US5321945 18 Feb 1993 21 Jun 1994 Honeywell Inc. Apparatus for controlling fuel transfers in a distributed fuel tank system US2738150 A 13 Mar 1956 David A Robinette Single aileron control system for airplanes US2612329 * 13 Nov 1948 30 Sep 1952 Northrop Aircraft Inc Aileron, flap, and dive brake US4566657 * 1 Dec 1980 28 Jan 1986 Grow Harlow B Span loaded flying wing control US4717097 * 3 Mar 1986 5 Jan 1988 The Boeing Company Aircraft wings with aileron-supported ground speed spoilers and trailing edge flaps US20110135472 * 8 Nov 2010 9 Jun 2011 Airbus Operations (S.A.S) Aerodynamic flight control surface said of crocodile style for aircraft OBJECT AND ADVANTAGE An aircraft system is proposed, that: 1: Based on the knowledge of an upcoming waypoint along an aircraft’s known route, moves fuel across the wing fuel tanks at a high transfer rate to de-equalise fuel quantity in tank pairs thereby producing a rolling moment to bank the aircraft in the direction of the required turn. The rolling moment generated thereby shall help to reduce the aileron deflections required during such a turn. The aim in creating such a rolling moment is not to replace the action of the aileron but it is rather to augment roll control through a mechanism that inherently reduces the induced drag produced in a roll manoeuvre and thereby also reduces the required rudder deflection to counter adverse yaw. The extent of the augmentative rolling moment shall be determined to ensure that the summation of fuel over burn due residual drag arising from the aircrafts continued flight in banked turns after completion of a desired course correction(until the rolling moment due to fuel is nullified), is less than the summation of fuel burn reduction achieved due to a reduction in peak drag values during coordinated turns on any given route, through a reduction the additional lift produced by the aileron. As system is proposed that relates to a method of generating a rolling moment on an aircraft to affect a roll manoeuvre. As described in section 2, the use of ailerons in flight has some drawback, i.e. it inherently leads to an increase in fuel consumption during manoeuvres due to: 1. Generation of additional induced drag on the wing where the effective angle of incidence of the wing has been increased through the downwards deployment of an aileron. 2. Form drag increase due to spoiling effect of the downwards moving aileron. 3. Form drag increase due to rudder deflection to counter adverse yaw. The object is to remedy the aforementioned drawbacks. 2: The said system shall also be capable of generating a rolling moment through placement of fuel in fuel tanks to trim the aircraft in roll. It shall perform this function by taking account of the deviation of the aircraft’s roll attitude in flight from a known optimal roll attitude and placing fuel in tank such a countering rolling moment is produced to take the aircraft to its optimal (i.e. low fuel burn) cruise roll attitude. The said system is expected to reduce aircraft drag and fuel burn for any given route. SUMMARY The proposed system comprises a conjugate flight control, navigation and fuel management system that calculates the aileron deflections required for an upcoming aircraft turn and in turn commands the fuel transfer pumps and valves in the wing tanks to initiate a transfer of a predetermined quantity of fuel to a predetermined tank to create a predetermined moment about the aircrafts roll axis before the way point is reached, upon confirming that the predetermined fraction of rolling moment has been generated, it deducts the achieved rolling moment from the rolling moment required for the said turn and deflects the aileron to produce only the difference between the required and already achieved rolling moment when the turn is initiated at the way point. Once the desired course change has been implemented or the desired roll rate has been achieved, a further command may be issued by the proposed system to equalise fuel quantity in all fuel tanks involved in the previously described manoeuvre, thus reducing the augmentative rolling moment to zero. The extent of the augmentative rolling moment shall be determined to ensure that the summation of fuel over burn due to residual drag -arising from the aircrafts continued flight in banked turns after completion of a desired course correction- is less than the summation of fuel burn reduction achieved due to a reduction in peak drag values that are expected to occur during coordinated turns on any given route. The aircraft may remain in a residual sustained bank attitude after completion of a course correction until the fuel imbalance across the tanks has been corrected. An overview of the timeline of the expected actions of this system is illustrated in Figure 1 and a figure illustrating expected (non-validated) reduction in fuel burn is illustrated in Figure 2. FIGURE 1 FIGURE 2 The system shall also be capable of generating a rolling moment through placement of fuel in fuel tanks to trim the aircraft in roll. It shall perform this function by taking account of the deviation of the aircraft’s roll attitude in flight from a known optimal roll attitude and placing fuel in tank such a countering rolling moment is produced to take the aircraft to its optimal (i.e. low fuel burn) cruise roll attitude. In summary, the following is proposed: 1) A process for transferring fuel into an aircraft’s fuel tank in flight, whereby the mass of fuel contained in some tanks produces a rolling moment in flight. The said process makes it possible at each or some instance of the aircrafts expected manoeuvres while it is piloted manually or by an auto-pilot to reduce the angle of deflection of ailerons to affect a turn of that aircraft in flight or to solely create the desired turn through the moment generated by transfer of fuel to create a disparity in fuel mass in aircrafts fuel tanks. a) The said process may be carried out in predictive manner through a prior knowledge of the aircrafts flight path as planned in the route programmed into the auto-pilot system. 2) A process for transferring fuel into an aircraft’s fuel tank in flight, whereby the mass of fuel contained in some tanks produces a rolling moment in flight to counter an existing rolling moment due to the asymmetries of systems, cargo, passenger placement on the aircraft in that particular flight and thereby allows piloting of the said aircraft at its optimal cruise attitude. Although the system as described may be used at any times during flight it is also anticipated that this system may be selectively used only for specific manoeuvres in certain flight phases. Although the system may generate the augmentative rolling moment automatically in anticipation of an impending turn, this feature may also be implemented such that a crew executing a standard rate turn with the autopilot may have the possibility of activating the augmentative rolling moment function to reduce fuel burn. Although the system may be used to produce augmentative rolling moment, it may be possible to use this system as a sole means of banking an aircraft in a desired direction. Although the described embodiments concern civil transport aircraft fuel tanks, the system may be applied to other types of aircraft fuel tanks such as military transporters, etc.

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Page 01 of 7

A METHOD AND SYSTEM OF AIRCRAFT ROLL CONTROL OR ROLL TRIM AND/OR ADVERSE YAW REDUCTION THROUGH
FUEL TRANSFER IN WING FUEL TANKS

TECHNICAL FIELD

This disclosure relates to a method of roll control or trimming the rolling moment of an aircraft, in particular a civil transport aircraft in its roll attitude though placement of fuel in wing fuel tank with the intention to generate a rolling moment due the differences in fuel quantity tank pairs
(i.e. two fuel tanks at the mirrored locations on opposite wings).

PROBLEM TO BE SOLVED AND PRIOR ART

Typically aircraft roll control is achieved through the use of lift augmentation devices (e.g. ailerons) that differentially change lift on both wings of an aircraft to create a rolling moment for manoeuvring an aircraft this is illustrated by the figure below. The movement of ailerons in flight also incurs a drag penalty.

Consider the following example, if a pilot wishes to effect a turn, the ailerons are commanded such that an aileron on one of the wings will move down and the one on the opposite wing will move up. The effect of an aileron moving down will be to increase the lift over that wing, whilst the aileron moving up will have a net effect of reducing lift on that wing. This essentially starts a roll. There are some secondary effects of this action. The wing, generating more lift will also generate more lift induced drag. The difference in drag between both wings also produces a tendency for the aircraft to yaw in the direction opposite to the intended direction of turn. This yaw tendency is referred to as adverse yaw.


Page 02 of 7

To overcome this situation, aircraft can be designed with a number of features which include:

Frise ailerons: A patented device that when an aileron is deflected up (to reduce lift) there is a lip protrusion into the airflow. This increases drag on that wing. In the case of a down-going aileron the design is such that it is smooth and flush so as to reduce any drag.

Differential Ailerons: These are designed so that the down-going aileron moves through less of an angle that the up-going aileron.

Spoilers: These panels which can be raised on the upper wing surface. They can be designed to operate on the down-going wing in conjunction with a bank - again increasing drag on that wing to counter the "adverse yaw".

List of Prior Art Patents:

US8613409 B2 24 Dec 2013 Olivier Cazals, Thierry Druot Aerodynamic flight control surface said of crocodile style for aircraft

US6125882 * 16 Dec 1998 3 Oct 2000 Kong; Carl Cheung Tung Fluid transfer system.

US5321945 18 Feb 1993 21 Jun 1994 Honeywell Inc. Apparatus for controlling fuel transfers in a distributed fuel tank system

US2738150 A 13 Mar 1956 David A Robinette Single aileron control system for airplanes


Page 03 of 7

US2612329 * 13 Nov 1948 30 Sep 1952 Northrop Aircraft Inc Aileron, flap, and dive brake

US4566657 * 1 Dec 1980 28 Jan 1986 Grow Harlow B Span loaded flying wing control

US4717097 * 3 Mar 1986 5 Jan 1988 Th...